Pra-U STPM Biology Term 3 2018 CB039148c

42 Biology Term 3 STPM Chapter 15 Ecology 15 15.1 Levels of Ecological Organisation Concept 1. The basic unit of life is organism. It is a living unit, ranging from the simplest such as viruses that only reproduce parasitically inside living cells to the most complex like human beings. 2. Life is organised in different ways, depending on what aspect is emphasised and whether it is seen from within or without. 3. From within, the most basic components are the genes. The genes are usually in the form of DNA, though RNA can behave likewise. 4. Genes cannot function without being inside a cell. Therefore, the basic unit of organisms is a cell, both prokaryotic and eukaryotic. 5. Unicellular organisms exist as cells but most organisms are multicellular. The cells within them are organised into tissues, then organs, then systems that form an organism. 6. Organisms are organised into populations, communities, ecosystems and biosphere, as shown in Figure 15.1. Learning Outcomes Students should be able to: (a) explain the concept of hierarchy in an ecosystem and the interaction between biotic and abiotic components. Producers (Autotrophs) Primary consumers (Herbivores) Secondary consumers (Carnivores/ omnivores) Detritivores and decomposers Tertiary consumers (Carnivores/ omnivores) Quaternary consumers (Carnivores/ omnivores) Genes Cells Tissues Organs Systems Organisms Populations Communities Ecosystems Biomes Biosphere Organism Component hierarchy: Trophic hierarchy: Figure 15.1 Concept of hierarchy in an ecosystem 7. They are also nutritionally organised into autotrophs or producers and heterotrophs, consumers, detritivores and decomposers. 8. Autotrophs can synthesise their own food from carbon dioxide and water with energy coming from the sunlight or chemical reactions. They are than able to supply food to the heterotrophs forming food chains and food webs. 9. Organisms are interdependent and they interact with the environment to live in different organisations of life.

43 Biology Term 3 STPM Chapter 15 Ecology 15 Hierarchy 1. Hierarchy is the ranks of organisms. The ranks represent the roles they play in an ecosystem. 2. These roles may be based on the components of life or nutritional relationship. 3. Based on the components of life, the lowest rank is the individual organisms of a species. 4. They then form the next rank i.e. the population, members of the same species. For example, a population of moss grow on a wet rock surface which is suitable for their growth. 5. The populations form communities. For example, besides mosses that grow on moist rock surface, algae, fungi, bacteria and ferns may start to grow from spores blown there. Thus, these populations form a community in that habitat. 6. More than one community may form an ecosystem. If a big area is taken into consideration, seeds from plants may drop in new areas. This forms a community of plants. As plants attract animals as food source, an ecosystem may develop over time depending on the location of the area. 7. On a bigger scale, more than one ecosystem may from a biome. For example, a tropical rainforest biome comprises not just the forest but also the river, seaside and ocean. 8. The biosphere is formed by 8 major biomes i.e. tropical rain forest, temperate deciduous forest, temperate evergreen forest, taiga, savannah, temperate grassland, desert and tundra. Biomes usually occupy big areas with characteristic features determined by climatic factors. 9. Based on nutritional relationship, the lowest rank is the producers i.e. the green plants and some bacteria. Under the ocean, around the volcanic vent chemoautotrophic bacteria living in seashells are the producers serving that community. 10. The second rank is the primary consumers, consisting of herbivores and detritivores. The primary consumers usually eat part of the plants such as leaves, flowers or fruits. Detritivores feed on fallen leaves. These detritivores include earthworms and some insects. 11. The third rank is the secondary consumers, consisting of carnivores and omnivores. There is seldom a fourth rank of tertiary consumers and even less common, fifth rank of quaternary consumers. 12. The decomposers fit into another rank. They consist of bacteria and fungi. With the help of insects and other animals, decomposers decompose the dead producers or consumers. Their actions help to recycle the mineral ions in the biosphere. Summary Hierarchy 6. Biosphere The part of Earth that contains all biomes. 5. Biome More than one ecosystem 4. Ecosystem Several communities and its non living surroundings 3. Communities More than one population of different species sharing a common habitat 2. Population Group of organism of the same species living in the same area. 1. Organism Individual living thing

44 Biology Term 3 STPM Chapter 15 Ecology 15 Interactions between Biotic Components 1. The different interactions in the biosphere can be summarised in Figure 15.2. Plants Predation Environment Decomposers Epiphytes Symbionts Parasites Omnivores Herbivores Carnivores Herbivory Detritivores Figure 15.2 The different interactions in the biosphere 2. Members of a species compete for food, water, shelter, mates and sunlight in their lives. This is a simple form of interaction which eliminates the weak through competition. 3. Members of the same species help one another, especially animals that live in herds like elephants or social groups like bees and termites. They are more succesful in life compared to animals that live alone. 4. There are interspecific competition for food and nesting sites. The tigers and the panthers compete and kill deers for food. Such competitions will lead to the adaptation or elimination of either one from the habitat. 5. There are mutualistic relationships among different species. The hermit crab and the sea anemones are classic examples of symbiosis where both sides benefit. Another is flowering plants and pollinating insects. Such interactions ensure cooperation between different species. 6. Commensalism is another relationship where only one benefits but the other does not and is not harmed. Examples are epiphytes attached on tree trunks such as orchids and ferns. 7. Parasitism is another form of relationship where the parasite benefits and the host suffers. The parasitic round worms benefit from the food and warmth in the intestine of animals and the host suffers from the loss of food and injuries to the intestinal walls. 8. Heterotrophs depend on autotrophs for food. For example, herbivores like cows depend on plants for food. Detritivores such as crabs and earthworms also depend on autotrophs. Autotrophs INFO Interspecific Competition

45 Biology Term 3 STPM Chapter 15 Ecology 15 in turn benefit from heterotrops as animals, polinate, dispose seed and recycle nutrients. 9. Predators depend on preys for food. For example, owls feed on rats. This is a natural population control from the top down. Without predators, the ecosystem may not be balanced. 10. When plants and animals die, they are decomposed by decomposers, bacteria and fungi with the help of detritivores like fly larvae. Therefore, others benefit through their actions which return mineral ions to the biosphere. Interactions between Biotic and Abiotic Components Sunlight 1. Sunlight gives heat to the Earth. Without sunlight, the temperature on Earth would approach absolute zero and all water would freeze thus, no organism can live. 2. Sunlight is the ultimate source of energy which supplies energy for photosynthesis to photoautotrophs including plants and in turn the plants are the food source for other organisms. 3. Most of our fuels such as coal, oil and natural gas represent sunlight energy captured by photosynthetic organisms. These fuels may only be temporarily power the Earth as it is exhaustible. 4. Sunlight powers biogeochemical cycles and is the primary climate determinant. The heat hastens the process of chemical reactions in nature. It also heats up the Earth resulting in drought or uneven distribution of rain. 5. Sunlight in the form of photoperiod affects flowering in plants and reproductive activities of many organisms including seed germination. It also affects the internal clock of many organisms and their activities. Temperature 1. Temperature is a form of kinetic energy that increases the movement of electrons of atoms, atoms within molecules and molecules within organisms or in the environment. Too low a temperature results in slow biochemical reactions and too high a temperature denatures enzymes stopping all biochemical reactions. Optimal temperatures of 10°C to 40°C are suitable for variable organisms on Earth. 2. Temperature changes with latitude. The direct overhead sunlight produces high temperatures in the tropics throughout the year resulting in higher organism densities especially in the tropical rainforest. 3. The seasonal temperature changes in different parts of the Earth affect the activities of all organisms. Plants drop their leaves in autumn and almost stop growing in winter. 2013

46 Biology Term 3 STPM Chapter 15 Ecology 15 4. The different seasonal temperatures in opposing north and south hemispheres cause animal migrations. Birds from the southern hemisphere fly to the north during summer. Summer in the North Pole produces abundant food in the form of vegetation and insects that attract the birds to nest and reproduce. Precipitation 1. Precipitation in the form of rain affects the distribution of organisms. Water is essential for life. Deserts are almost devoid of lives. 2. High rainfall in tropical rainforests produces the richest biodiversity in Malaysia and other tropical countries. 3. Please refer to “moisture” page 68. Wind velocity 1. Wind velocity affects precipitation that affects distribution of organisms on earth. 2. Wind causes ocean currents affecting temperature and nutrient distribution in the ocean. This causes algal bloom affecting aquatic life distribution and migration. Example is the migration of whales in the Pacific Ocean. 3. Wind is required for pollination and dispersal of seeds and spores further affecting vegetation distribution. The atmosphere 1. The atmosphere contains oxygen, essential for life. Oxygen is required for aerobic respiration to break down food producing ATP. ATP supplies energy for all energy-required processes in organisms. 2. The atmosphere contains carbon dioxide that is essential for photosynthetic organisms to make organic food. The increase in carbon dioxide causes greenhouse effect and global warming threatening organisms on Earth. 3. It protects the Earth’s surface from radiations from the sun and outerspace. 4. Present with different gases such as oxygen, it helps to maintain life on Earth and regulates climate changes. Wildfires 1. Wildfires which are fires started by lightning are common occurrences in certain regions such as North America and Australia during summer. Wildfires are disastrous and directly kill organisms.

47 Biology Term 3 STPM Chapter 15 Ecology 15 Interactions between biotic and abiotic components: 1. Sunlight (energy, drive biogeochemical cycles and photoperiodic effects) 2. Temperature (kinetic energy, tropical heat, regulate growth and migration) 3. Precipitation (water sustains life and determines organism distribution) 4. Wind (affects rain, ocean currents and plant dispersal) 5. Atmosphere (gases for physiological processes, and balance on Earth) 6. Wildfires (kill, free minerals and cause adaptation) 7. Soil (determines biomes and distribution) 8. Freshwater (determines inland aquatic life) 9. Ocean (buoyancy, supports aquatic animals) 10. Humans (affects atmosphere through man-made structures and activities) 2. It dries substances freeing minerals that are locked in organic substances. The ashes remaining after a fire are rich in potassium, phosphorus, calcium and other minerals essential for growth. 3. It removes plant cover and exposes soil. This stimulates the germination and establishment of seeds requiring bare soil and growth of shade-intolerant plants. 4. Wildfires increase soil erosion as they remove plant cover leaving the soil vulnerable to wind and water. 5. It also causes adaptation in many grasslands and pine forests. It helps to maintain grasses as dominant vegetation in grasslands by removing fire-sensitive hardwood trees. Soil 1. Soil structures and components determine the survival of vegetation and animals. The world’s biomes with their dominant vegetation are partly due to soil (edaphic) factors. 2. Soil water content, salinity, fertility, and topography determine different types of vegetation and animal population. Freshwater 1. Rivers, ponds and lakes affect aquatic lives depending on latitude, climate change and mineral content. Different parts of the world have differently adapted fishes. 2. Flooded forests of Brazil sustain fish like archer fish and piranha. The largest freshwater arapaima is found in the Amazon river. 3. Freshwater ecosystem in the Amazon supplies other aquatic animals besides fish. These animals include the giant Anaconda and freshwater porpoise. 4. In Malaysia, the wetland is adapted with special vegetation such as Nipah palm, ferns and water lilies. Besides, different types of fish, amphibians, reptiles and birds are endemic there. Ocean 1. This biggest biome on Earth is divided into different zones such as neritic (littoral), pelagic (far from shore), abyssal (dark ocean) and benthic (ocean floor) zones. 2. Depending on the ocean depth, each zone supports different adapted organisms. Humans 1. Human are major biotic components due to their large population on Earth. They play major roles in changing and affecting other lives. Summary

48 Biology Term 3 STPM Chapter 15 Ecology 15 2. Human buildings and structures have changed the surface of the Earth. In some cities, there is hardly any space for vegetation. 3. Agricultural activities have made many places barren due to unregulated stripping of top soil. 4. Pollution and carbon dioxide emission caused by humans are major contributors to greenhouse effect and global warming. 15.2 Biogeochemical Cycles 1. Biogeochemical cycle (Figure 15.3) is the flow of element (nutrient) that circulates through the communities and environment in the biosphere, involving nutritional relationship among autotrophs, heterotrophs and decomposers. Element reservoir in the environment Geochemical reactions Element reserves in the ecosystems Herbivores, carnivores, parasites Detritivores, decomposers Producers Figure 15.3 Generalised biogeochemical cycle 2. It can be generalised that only a fraction of the element is made available to the ecosystem from the main reservoir. Most of the mineral elements in the environment are locked in insoluble form. 3. The element is first absorbed by producers from the environment in the form of soluble salts or mineral ions in the soil water. After biosynthesis, most of the elements are assimilated and become organic forms. 4. The element is circulated from producers to consumers and made available again through detritivores and decomposers. Therefore, the ecosystem reserves of the elements come from the physical environment and recycling. A small proportion of the elements is also become insoluble and locked away. 5. Each year, the amount of element that enters the ecosystems of the biosphere is smaller than that is being circulated. The process of interchanging from insoluble to soluble is affected by many environmental and human factors. Learning Outcomes Students should be able to: (a) describe the biogeochemical cycles (carbon, phosphorus and sulphur),and explain their importance.

49 Biology Term 3 STPM Chapter 15 Ecology 15 6. Geochemical activities such as rainfall, snowfall, volcano eruption and weathering, make elements available to the reservoir in the ecosystems. Metabolic fixations such as nitrogen fixation also bring some elements into the reservoir. Mining also bring a certain amount into the environment. Carbon Cycle 1. The carbon cycle involves the cycling of the carbon element. The outline of the process is as shown in Figure 15.4. Carbonification Marine animals Marine plants Factories Bicarbonate in ocean Marine sediments Land plants Land animals Decomposition Carbon dioxide in the atmosphere Dead organisms and animal waste Combustion Photosynthesis Respiration Decay Diffusion Settling Herbivory Figure 15.4 Carbon cycle 2. Carbon dioxide gas in the atmosphere forms the element reserve in the ecosystem. The percentage of carbon dioxide gas in the atmosphere is only 0.04%. The solubility of carbon dioxide gas in water is low but it forms an important element reserve in aquatic environment in both freshwater, marine, and not so significant in soil water. 3. From the atmosphere or aquatic environment, autotrophs mainly plants absorb carbon dioxide through the stomata for photosynthesis in the presence light. This also occurs in the aquatic environment for both photoautotrophs and chemoautotrophs especially bacteria living around marine volcanic vents. VIDEO The Carbon Cycle

50 Biology Term 3 STPM Chapter 15 Ecology 15 4. The carbon in the producers in the form of organic substances especially carbohydrates, proteins, and fats are passed to the primary consumers or omnivores. This occurs when the primary consumers like herbivores feed on plants. These carbon forms are also passed to the higher-level consumers through the food web. Thus, carbon element is passed from plants to animals. 5. During cellular respiration, carbon dioxide is produced and recycled into the atmosphere. All organisms break down carbon organic food to produce energy in the form of ATP. This is the basic cycling of carbon in the atmoshere where the carbon element is returned to the element reserve. 6. More carbon dioxide is released from the decomposition of detritus like leaves sheded from plants or hair from mammals. The decomposition of plants and animal bodies also releases carbon dioxide after they die. This is carried out by saprophytic bacteria and fungi. Some of the carbon element is absorbed by the decomposers as glucose. 7. When organisms die from mass extinction, their body carbon is compressed. In the course of millions of years, the carbon element forms graphite, coal and raw petroleum including natural gases like methane. These carbon forms of fossil fuels are now extracted and burned including wood emitting carbon dioxide into the atmosphere. 8. Besides that, the geological changes of soluble carbonate salts in the water also form insoluble carbonate rocks. This insoluble form of carbonate comes from animal shells and skeletons which are part of the element resevoir in the environment. 9. Natural volcanic activity and artifical mining can also change these insoluble carbonates into carbon dioxide. However, only a small addition of carbon dioxide is emitted from insoluble rocks either through natural or artificial reactions like the making of cement. 10. An important aspect of carbon cycle is its balanced nature of cycling. Any imbalance like what is happening now due to the increase in carbon dioxide concentration in the atmosphere will cause greenhouse effect and global warming. Thus, if carbon dioxide concentration keeps on increasing, many organisms would die. 11. We can make use of the knowledge we have on carbon cycle to reduce the emission of carbon dioxide from fossil fuels. Plants are not to be cut but more should be planted. Agricultural systems have to be adjusted to have less tillage or ploughing so that more organic substances remain in the soil rather than being converted into carbon dioxide. A more unconventional method is by artifically removing carbon dioxide and store it some where in the Earth.

51 Biology Term 3 STPM Chapter 15 Ecology 15 Phosphorus Cycle 1. The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus in the environment as shown in Figure 15.5. Weathering Mining Settling Sedimentation Marine animals Sedimentary rocks Marine sediments Excretions Marine birds Wastes and decomposition Wastes and decomposition Uptake by marine autotrophs Phosphates in soil, water, rivers and lakes Phosphates in sea Uptake by plants Animals Figure 15.5 Phosphorus cycle 2. Soluble phosphates in the soil, water, river and lakes act as phosphorus element reserves in the ecosystem. These soluble phosphates may flow into the sea to be used by marine autotrophs. 3. The soluble phosphates are absorbed by plants and other autotrophs in aquatic freshwater or marine ecosystems. These phosphates are assimilated as organic phosphates mainly in the form of phospholipids in the cell membrane, nucleotides including ATP and nucleic acids, RNA and DNA. Certain amounts are also present in plant cells as phosphates. 4. Through herbivory, the organic phosphates are passed to the herbivores which is then passed to the carnivores or top predators. Thus, the element is passed from plants to animals. 5. When the animals urinate, defecate or die, the phosphates are returned to the soil after being decomposed by bacteria and fungi. Similarly, detritus from plants or the whole plant will also decompose. 6. This too happens in the sea with a slight difference. Marine autotrops are plytoplankton and marine algae. The herbivores are zooplanktons and algae eating fish or crustaceans. The primary INFO Phosphorus Cycle

52 Biology Term 3 STPM Chapter 15 Ecology 15 consumers will pass the organic phosphates to the carnivores, mainly fish. When marine birds feed on these fish, the phosphates may be returned to the land again after birds defecate or die on land. 7. Phosphates tend to be less soluble in water and much is lost in insoluble form by sedimentation. This has also occured throughout the ages forming phosphate rocks. These phosphate rocks form the element resevoir in the environment. 8. Phosphate rocks will be returned as soluble phosphate only by geological activities such as volcanic activities or mining. Guano from bat faeces are mined as fertilisers and returned to the soil again. 9. The importance of the phosphorus cycle is that the element forms part of the phosphate fertiliser for plants. The intense agricultural practice over the past decades has caused in the reduction of soluble phosphates in the element reserve in both soil and water. Phosphates are leached into the soil or settle as insoluble phosphate on the ocean floor. 10. Understanding of the phosphorus cycle enables the balance or reduction of the loss of soluble phosphate from soil and water. One artificial way to mine these insoluble phosphates and convert them back to soluble form is by the use of organic fertilisers and better agricultural systems of less tillage. Sulphur Cycle 1. The sulphur cycle is the movement of sulphur to and from minerals and living systems. It involves both atmospheric and terrestrial processes. 2. Soluble sulphates in the soil and aquatic environment act as the element reserves in the ecosystems. These soluble sulphates are present in amounts enough to sustain plant life in most soil and aquatic environments, both freshwater and marine. 3. Plants and other autotrophs absorb the sulphate ions and assimilate the sulphur element to form sulphur containing organic compounds. These compounds include two amino acids, cysteine and methionine that are used to form proteins. Besides that, a few coenzymes also contain sulphur. 4. From plants, the sulphur containing proteins are passed to the herbivores, which is then passed to the carnivores or top predators. 5. When these animals excrete, defecate or die, certain amount of sulphur element are returned to the soil through aerobic breakdown. The sulphur element may also be returned to the soil through anaerobic breakdown in the form of sulfides. Similarly, Exam Tips Remember the phosphorus and sulphur cycles and the roles of the different organisms. INFO Sulphur Cycle

53 Biology Term 3 STPM Chapter 15 Ecology 15 when the whole plant dies, the sulphur containing element returns to the soil as sulphate or sulfides. 6. Sulphates in the soil may be converted into sulfides by sulphatereducing bacteria, Desulfovibrio. These anaerobic bacteria use sulphates as oxygen donors. 7. Sulfides in the soil are spontaneously converted into sulphur. Autotrophic bacteria in hotsprings, the green sulphur bacteria Chlorobium or purple sulphur bacteria Chromatium use hydrogen sulfide as hydrogen ion donor forming sulphur. These are photosynthetic bacteria. 8. Sulphur in the soil can be oxidised by sulphur oxidising bacteria, Thiobacillus into sulphates. These bacteria are chemosynthetic bacteria using sulphur as energy source to fix carbon dioxide into glucose. 9. The soluble sulphates in the soil or water may be leached as insoluble sulphate salts. This is part of the sedimentation process that occur through the ages forming the sulphur element reservoir in the environment. Through mining and geological activities like volcanic activity and weathering, the insoluble sulphates may become soluble to be recycled again. 10. The sulphur cycle is summarised in Figure 15.6 below: Organic sulphur in plants (Sulphur containing amino acids) Organic sulphur in animals Sulphides in the soil Anaerobic breakdown Aerobic breakdown Sulphate reducing bacteria Desulfovibrio Herbivory Absorption Sulphur Oxidation by sulphur bacteria Thiobacillus Spontaneous or autotrophic bacteria Chlorobium and Chromatium Sulphates in soil Figure 15.6 Sulphur cycle 11. Sulphur cycle seems more balanced in the ecosystem due to its lesser amount in the ecosystem. However, monitoring the cycle would enable us to notice any imbalances. 12. The sulphur element is an element in the proteins of both plants and animals. Any form of sulphur element in this Earth should not be increased or decreased dramatically. An increase will be leached and a decrease will reduce the growth of plants, so that of animals.

54 Biology Term 3 STPM Chapter 15 Ecology 15 15.3 Energy flow Energy 1. Energy is the ability or capacity to perform work. 2. It is a quantitative property describing a physical system or the state of an object. In the form of ATP, energy is required by organisms for anabolism, active transport and to push nutrients through the organisms. 3. Energy exists in different forms such as mechanical, chemical, heat, electric and potential forms that are inter-convertible. 4. Its transfer is controlled by the law of thermodynamics. 5. The first law of thermodynamics states that energy cannot be created nor destroyed but can change form. 6. The second law of thermodynamics states that when performing work, the transfer of energy is not 100% efficient and energy is lost as heat. Energy Flow 1. Energy flow is the energy conversion from sunlight to organic substances during photosynthesis with nutrients from abiotic components which is then transferred to animals. Finally, energy is lost in the atmosphere after the organisms die and with the help of decomposers that break down dead organisms. 2. An example of such flow is in a tropical rainforest ecosystem. Another example is in the aquatic ecosystem of a lake. 3. The forest plants as producers carry out photosynthesis to convert light energy into chemical energy in the form of biomass. In the lake, the producers are the aquatic plants such as Elodea and the algae that lives on the surface of the aquatic plants as well as unicellular algae living in the water such as Chlorella. 4. In the forest, energy in the plants flows to the primary consumers like monkeys and deer when they consume parts of these plants. In the lake, the primary consumers are the mosquito larvae, water snails, tadpoles and herbivorous fish that feed on the algae and aquatic plants. 5. In the forest, this energy in turn flows to the secondary consumers like the tigers when they feed on the primary consumers. Meanwhile, in the lake, carnivorous fish such as guppy will feed on the mosquito larvae. Bigger fish like snakehead will feed on the guppy and smaller herbivorous fish. Eagles and Kingfishers act as top predators. Learning Outcomes Students should be able to: (a) describe the energy flow and the efficiency of energy transfer in terrestrial ecosystems (tropical rainforest) and aquatic ecosystems (lake). Exam Tips Remember the two laws of thermodynamics and relate them to energy transfer. 2010

55 Biology Term 3 STPM Chapter 15 Ecology 15 6. When the plants and animals die, the chemical energy within them flows partly to the decomposers like bacteria and fungi, some to the detritivores and animals that feed on the dead body but is mainly loss as heat in to the atmosphere. Similarly, in the lake, when the aquatic plants and fish die, they are also decomposed. In both cases, the energy is finally lost but the nutrients are recycled. Energy Transfer 1. About 1 × 106 kJ m–2 year–1 of sunlight energy shines onto the forest plants. The same amount would also reach the surface of a tropical lake. 2. 95 – 99% of it is lost from the plants through reflection, radiation and heat of evaporation in the forest. The same amount would also be reflected from the water surface and lost as evaporation heat. 3. 1 – 5% of it is absorbed by the chlorophylls to produce organic molecules in the forest plants. Lesser percentage would be absorbed by aquatic plants and algae as the water in lakes are not fully transparent to allow light penetration. 4. The storage rate of chemical energy is known as gross primary production. This is the amount of energy absorbed by chlorophylls to form organic substances without deducting what is used in respiration. 5. 20 – 50% of the stored energy is used at the same time in the process of photorespiration and respiration, leaving the balance called net primary production (NPP). 6. The total net primary production is only about 1% of the total sunlight absorbed. The mean NPP of a tropical rainforest is 2200 g/ m2 /year whereas less than 200 g/m2 /year in most lakes. This is due to high temperatures and rainfall with high density of forest with plants. 7. When the energy is transferred to herbivores and carnivores, a big proportion is lost. This is due to the organisms are not fully edible or digestible and are egested. A portion of the energy is also used in respiration and excretion. Aquatic plants may contain less nutrient content as compared to land plants. 8. The net balance in the primary consumers’ biomass is called net secondary production. 9. From the primary consumers, the energy may be passed to the tertiary or quaternary consumers. 10. Every time energy flows from one trophic level to another, only a small amount (10%) is passed on and the majority is lost as heat. 11. This loss of energy is due to the transfer efficiency which is less than 45% when the energy is converted from one form to another. An example is the conversion of chemical to mechanical energy for body movement. Exam Tips Remember the energy flow through the biosphere and how the energy is lost in each level in terms of carbon recycling. 2014 INFO Net Primary Productivity

56 Biology Term 3 STPM Chapter 15 Ecology 15 12. Finally, when the consumers die, the energy is lost as heat. Some energy is passed to the decomposers like bacteria and fungi. 13. The energy flow in the ecosystem is as shown below. Learning Outcomes Students should be able to: (a) explain population growth (S and J growth curves), biotic potential, natality, mortality, migration and survivorship; (b) explain the characteristics of populations that show Type I, Type II and Type III survivorship curves, K-strategies and r-strategies. Keys: A = energy absorbed PS = photosynthesis G = gross primary production N = net primary production R = respiration D = die E = egested or excreted S = secondary production C = consumed by A S Sunlight G Reflected Heat N Detritivores & decomposers S S C C C R E D D D D E E R R R PS Quick Check 1 1. Outline the energy transfer in a pond. 15.4 Population Ecology Biotic Potential 1. Biotic potential is the maximum population growth rate possible for a species i.e. the growth rate in a condition with ideal unlimited environmental resources. 2. The growth rate can be represented by dN dt = rN, where r is a constant or the intrinsic rate of natural increase for a species and N is the number of individuals in a population. 3. The natural rate of increase is always exponential and leads to population explosion, as shown in Figure 15.7. 1 000 Population size/number Number of generations or time dN dt = 1.0 N Figure 15.7 Exponential growth 4. When the population is limited by one or more limiting factors, it can be represented by

57 Biology Term 3 STPM Chapter 15 Ecology 15 dN dt = rN(K – N K ) where, r = intrinsic growth constant N = number of individual in a population K = maximum number of individuals in a population in an environment (carrying capacity). This will give a normal sigmoid curve, as shown in Figure 15.8. 1 000 dN dt 1 000 – N 1 000 – = 1.0(––––––) Population size/number Number of generations or time Figure 15.8 Normal sigmoid growth 5. However, the actual population increase can be represented as: Population increase = (birth rate – death rate) + (immigration – emigration) 6. In many natural populations, the full biotic potential is never achieved. This is due to more than one limiting factors acting independently or together. Any two such factors may be positively or negatively correlated. 7. The biotic potential of each species varies and depends on many factors. Some of the factors are also too difficult to determine or a minor amount may have large effect like certain microelements. 8. The limiting factors are both abiotic and biotic. Most factors act together. It is almost impossible to separate out how each factor acts. 9. The abiotic factors are light, temperature, climatic conditions, humidity, rainfall, edaphic, food resources and resting places. 10. The biotic factors are competition, predation, adaptive behaviour, parasitism and mutualism. 11. Biotic potential also depends on the ratio of male to female and demography, the age distribution in the population. These affect the chances of mating and the success of the outcome. 12. It is important to determine the population size of a species as the next generation depends on it. The survival or the extinction of a species is controlled by the biotic potential. High biotic potential will result in high survival. Language Check Language Check Edaptic = relating to soil. Characteristics include such factors as water content, acidity, aeration and nutrient availability

58 Biology Term 3 STPM Chapter 15 Ecology 15 Natality 1. Natality is the birth rate i.e. the number of offspring produced per female per unit time, usually per year. 2. In human population, it is the number of children born per 1,000 persons per year. Malaysia has a birth rate of around 22 births per 1000. 3. In general, the birth rate in developed countries is less than that of developing countries. This is due to the focus on career development rather than family development. 4. Genetic factor is the main factor that determines the number of eggs produced. Fish produce thousands of eggs per spawn. Mammals like cows produce usually one whereas some like pigs may produce twelve per litter. 5. Environmental factors, such as temperature, rain, food and diseases influence birth rates. 6. For example, during rainy season, oil palms produce more fruits, resulting in more food for rats as well as higher birth rates. Drought, lack of food and diseases lower the birth rates. Mortality 1. Mortality is the death rate, the percentage or number of deaths per thousand per year. 2. In developed countries, the mortality rate is low in comparison to developing countries. 3. The reason is the higher standards of health care and living condition. 4. In Japan and Costa Rica, the mortality rate is very low, as the proportion of younger people is more than older people. 5. In general, better environmental conditions, food and water supplies lower the mortality rate. For example, a year with good amount of rainfall increases the growth of grass and lowers the mortality of herbivores. 6. Disease outbreak such as AIDS has increased the mortality rate in many countries, such as Africa. Migration 1. Migration is the movement of animals from one place to another. 2. It can be divided into immigration and emigration. 3. Immigration increases the population as individuals are moving in. 4. Emigration decreases the population as individuals are moving away.

59 Biology Term 3 STPM Chapter 15 Ecology 15 5. Reasons of migration are to look for food, water, warmth, nesting sites and to avoid bad weather. 6. For examples, reindeer, birds and other animals migrate to the North Pole during the short summer to breed and hunt. Some birds come from as far as Australia, New Zealand, South America and South Africa. They then migrate south after the summer. 7. The herbivores in Southern Africa make annual circuit of migration to seek pasture and avoid drought. These animals include the wildebeests, zebras and deers. Survivorship 1. Survivorship is the percentage of organisms that are able to survive any part of their life cycles, in a particular area. 2. Environmental factors that favour survival are abundant food and water resources and optimum environmental conditions such as suitable warmth. 3. The factors that decrease survival are diseases, poor environmental resources and conditions, such as drought. 4. Survival also depends on genetic factors that determine the lifespan. Some animals such as tortoises invariably live longer. 5. The organisms start to become old or undergo senescence after maturity and the chances of dying increase. 6. There are three types of survivorship, as shown in Figure 15.9. Type I Curve I shows death occurs during senescence like people in developed countries. Example, people in Japan mostly die at the age of 80 years old and above. Type II Curve II shows a uniform death rate from young to old as in many invertebrates and plants. Type III Curve III shows death occurs at early and also later part of life like people in under-developed countries, especially in Ethiopia. Death rate is high at early infancy and young age because of starvation and diseases. Population Growth 1. Population growth is the rate of increase in the number of members over time as shown in a growth curve. 2. There are two types of growth curves, namely S or sigmoid growth curve and J growth curve, as shown in Figure 15.10. 3. S curve shows an initial slow growth rate, a rapid increase and levelling off to a maximum size. This is as shown in most populations of large organisms, including the laboratory culture of yeast. Exam Tips Remember two types of growth curves, carrying capacity and factors affecting growth. (STPM 2015 structured question) 100 50 0 Percent survived Age I II III Figure 15.9 Patterns of survival 2014

60 Biology Term 3 STPM Chapter 15 Ecology 15 4. J curve shows a fast ‘boom’ to reach the maximum and follows by a fast ‘bust’ pattern. This is as shown in most population of smaller organisms including the laboratory culture of Dapnia, a water flea. K-strategy 1. K-strategy is a growth pattern that exhibits S or sigmoid pattern of growth. 2. This shows a slow reproductive rate with few offspring, as in big trees or bigger mammals. Growth rate = dN dt = rN(K – N K ) where r = intrinsic growth constant N = number of individual in a population K = carrying capacity (maximum number of individuals in a population in an environment) 3. When N > K, the rate of growth is negative. There is a decrease in the population size. 4. When N < K, the rate of growth is positive. The population size increases. 5. When K = N, the rate of growth is zero meaning that the size has reached carrying capacity, and there is no further increase. r-strategy 1. r-strategy is a pattern of growth that exhibits J pattern of growth with fast ‘boom’ and fast ‘bust’. 2. This shows a fast reproductive rate with large broods as in annual plants and smaller invertebrates such as insects. Growth rate = dN dt ∝ N Therefore, dN dt = rN where r is a constant. 3. When r is big and positive, the population growth rate is very fast. 4. When r is big and negative, the rate of population decrease is very fast. 5. The differences between r-species and k-species is summarised in Table 15.1 Time S growth curve Number S curve Time J growth curve Number J curve Figure 15.10 The patterns of growth

61 Biology Term 3 STPM Chapter 15 Ecology 15 Table 15.1 The differences between r-species and K-species Characteristics r-species K-species 1. Reproductive rate Fast Slow 2. Offspring number Big Small 3. Influence of density Pronounced, on the reproductive rate Does not affect the reproductive rate 4. Population size Fluctuates widely Seldom fluctuates much 5. Population distribution Not fixed in one place Usually fixed 6. Dispersal Fast and wide Slow 7. Size of organisms Small Big 8. Lifespan Short, one year or shorter Long, up to hundreds of years 9. Survive better In exposed land Not in exposed land 10. Their habitat Last for a short while Last for a very long time 11. As a competitor Not good Very good 12. Defence system Not good Usually good 13. Dominant species Usually not Usually climax community 14. Adaptation as pioneer Usually good Usually not good 15. Examples Microorganisms, small insects Big trees and humans Learning Outcomes Students should be able to: (a) explain what is meant by carrying capacity and sustainable development; (b) explain the factors limiting the population size and distribution. 15.5 Carrying Capacity 1. Carrying capacity is the maximum number of individuals of a species that an environment can indefinitely support. 2. It is a stability point when the growth rate of a population under such an environment is zero. 3. It is the same as the maximum population size, as shown in the sigmoid curve in Figure 15.11. Number of individuals Carrying capacity Time Figure 15.11 Maximum number of individual is the same as carrying capacity 4. It also equals to the inflexion point I in the graph of rate of change against population size, as shown in Figure 15.12. 2014 INFO Carrying Capacity

62 Biology Term 3 STPM Chapter 15 Ecology 15 I Rate of change Population size Figure 15.12 Inflexion point is equal to carrying capacity 5. It is represented by K in the sigmoid growth formula as shown below. dN dt = rN(K – N K ) 6. It is important as it represents the maximum population size. It is used as a reference point to represent the maximum sustainable size in the wild population of fish in the sea and other animals in the wild. With the maximum production known, the amount of natural resources to be collected can be worked out. Management and Conservation of Ecosystems 1. Management and conservation of ecosystems in each country and the biosphere in general should be carried out with care so as not to destroy the ecosystems for the survival of all species including humans. 2. Aspects needed to be managed and conserved are as follows: (a) Genetic variation. Species diversity of animals or plants should be maintained. The population of endangered species should be increased by various means. (b) Land or soil. Land destroyed by mining and natural disasters such as volcanic activities should be planted with suitable plants, so that animals can survive there. (c) Pollution. Pollutions of air, soil, river and sea should be controlled. Industrial wastes should be treated before released into the environment. Random dumping of wastes, especially non-biodegradable ones, should be avoided. (d) Forest destruction. Forest is the treasure of future generations. Any unplanned utilisation should be avoided. (e) Over-collection. Over-collection is a major problem, especially in the sea. This may result in the decrease in future food resources.

63 Biology Term 3 STPM Chapter 15 Ecology 15 Sustainable Development 1. Sustainable development is the management of ecosystems so that natural resources are perpetuated, while continually being exploited. 2. It is of the utmost importance in fishery, forestry and agriculture. Fishery 1. Its aim is to continually collect marine organisms, especially fish without endangering any species driving it towards extinction. 2. The fish collected should follow a model suggested by Russell (1940), as shown in the formula below: S2 = S1 + (A + G) – (C + M) where S1 = stock weight at the beginning of the year S2 = stock weight at the end of the year A = addition from small fish G = gain from all fish C = collected weight M = mortality weight 3. The weight of fish collected should be equal to A + G – M, so that stock at the beginning of the year is the same as that of at the end of the year. 4. If too little is collected, the population will reach carrying capacity and competition will occur, small fish will tend to grow at a slower rate. 5. If overfished, collection will become smaller and fish collected will be thinner. 6. If overfishing continuous, the size of fish will become smaller, as the small ones are left to reproduce. Small fish will produce small variety by this artificial selection. 7. For sustainable development, a joint effort consisting all the neighbouring countries in the world, agree on the time, the amount to be fished and the diameter of net size to be used. Forestry 1. Sustainable development of forestry resources is to obtain resources without disturbing the ecosystem and causing species extinction. 2. If there is no cutting down of trees, the forest ecosystem will stabilise and species biodiversity will flourish. This is ideal but for economic reasons, trees still have to be cut.

64 Biology Term 3 STPM Chapter 15 Ecology 15 3. The gene pool in the forest can then be perpetuated and be very useful in the future for agriculture, medicine and aesthetics. Conservation is important for the future. 4. One third of each nation should be reserved as forest reserve. This should be treated as a national treasure, as future benefits may be more than present gain. 5. Optimum form of logging should be selectively carried out where a tree of certain diameter is allowed to be felled. Big canopy loss and rare species logging should not be allowed. 6. Replanting of species should be done as soon as logging is over. This will replace species cut and treat the harm done to the ecosystem more efficiently. 7. Illegal and excessive logging should not be allowed. Enforcement of the law should be strictly carried out. 8. Excessive logging in most countries have already occurred. Global warming, due to excessive amount of carbon dioxide produced and not utilised, causes green house effect. 9. Besides that, logging causes leaching, soil erosion, flood and change of climate. Local ecosystems and the biosphere are already damaged. Therefore, further damages should be avoided. 10. Paper recycling to prevent excessive felling has already been carried out. Effort in certain areas will counter the damage done in other areas. 11. Forest regeneration from barren ground is carried in an experimental and serious scale. Sustainable development of forestry utilisation is not a dream but can be a reality. Agriculture 1. The aim of sustainable development in agricultural land is to ensure enough food is produced for the world population. 2. The increase in agricultural land at the expense of forests should not be allowed. Enough damages have already been done to the forest ecosystem. 3. Increase in agricultural production may be carried out with desert land, lake and sea. Aquaculture has already produced food sources, especially fish and prawns. 4. The optimum condition is to produce higher yield with the present land areas by using modern techniques. 5. Modern equipment, incorporating computer control in tractors, can carry out ploughing, seed sowing, addition of fertilisers, weed and pest control, and harvesting.

65 Biology Term 3 STPM Chapter 15 Ecology 15 6. Green revolution started in the past is already producing results. The next revolution may come from genetic engineering. This will increase both quantity and quality of food produced. 7. Pest control is done biologically. The environment should not be spoiled by pesticides as pesticides can cause damage to the ecosystems. 8. Increase food production using green house is already practised. Unconventional methods using hydroponics have started to produce more food. Exam Tips Remember the meaning and importance of carrying capacity and sustainable development. Remember how fishery, forestry (STPM 2010 essay question) and agriculture are managed and conserved for sustainable utilisation. Quick Check 2 1. Suggest the aims and guidelines in the management of ecosystems. Limiting Factors on Population Size and Distribution The limiting factors affecting size and distribution of populations are divided into abiotic and biotic factors. Abiotic factors 1. The abiotic factors are non-living chemical or physical factors in the environment. They can be grouped into climatic factors such as light intensity, temperature, moisture, edaphic factors such as salinity, nutrient concentration (fertility), pH and water current. 2. These abiotic factors influence population growth, according to the Liebig’s and Shelford’s laws. 3. Liebig’s law (1840) (a) Liebig’s law is known as the law of minimum. (b) It states that the distribution of species is controlled by the environmental factor for which the organism has the narrowest range of adaptability or control. (c) In other words, it means that the success of a population growth is determined by the one crucial ingredient in the environment that is in short supply or minimum. (d) All abiotic factors are important in determining the growth of an organism but the one that is in short supply will limit the extent of its population size and distribution. (e) Many plants and animals have their own adaptations to different abiotic factors and the responses of their growth and distribution vary. (f) For example, the forest plants have different liking for sunlight intensity or shadiness. Some trees like full sunlight, others like intermediate sunlight and some like shadiness. The relative rates of tree growth in different light availability are as shown in Figure 15.13.

66 Biology Term 3 STPM Chapter 15 Ecology 15 50 Shade-loving Sun-loving Intermediate Relative diameter increment 0 0.5 1 Light availability (% full sun) 100 Sun-loving Intermediate Shade-loving Forest trees of different heights Figure 15.13 Light or shade determines growth of trees (g) Therefore, the trees in the tropical rainforest are of different heights. The shortest trees are the shade-loving trees where their growth is determined by the shade provided by the taller plants. The intermediate plants’ growth is determined by the shades of the tallest plants. The tallest plants are the sun-loving plants and they grow the fastest in order to receive the maximum amount of sunlight. 4. Shelford’s law (1913) (a) Shelford’s law is also known as the law of tolerance. (b) It states that organisms can only tolerate a certain range of physical factors. (c) There are upper and lower limits of the physical factors that a population can survive. (d) No individual can survive at any factor lower than the minimum limit or above the maximum limit. (e) This can be seen in the range of temperatures a population of monkeys can survive, as shown in Figure 15.14. Frequency/ number of individuals No individual Few –20 0 30 50 Temperature/ °C Abundant Few No Individual Intolerance zone Stress zone Optimum zone Stress zone Intolerance zone Figure 15.14 The bell shape tolerance range of a factor e.g. temperature (f) The range of tolerance is from – 20°C to 50°C but most of the individuals are found in the optimum zone of between 0°C and 30°C. Very few are found in the stress zones of – 20°C to 0°C and 30°C to 50°C. None can survive below – 20°C and above 50°C.

67 Biology Term 3 STPM Chapter 15 Ecology 15 5. Light (a) Light intensity affects plants directly more than light quality. This is because plants depend on light as energy source for photosynthesis. Only light at the forest ground and lower part of the ocean has different quality, as it is filtered by leaves or the water. (b) Light is a factor of survival for plants and photosynthetic bacteria. Without light, as in dark caves and dark ocean depth, photoautrophs cannot live. (c) Low light intensity or short photoperiod is a limiting factor for plants. This occurs under cloudy sky, at night or during winter months with short photoperiods. (d) Plants grow slower when light is in short supply. Together with low temperature as in winter, there is no growth or the plants die and exist as dormant seed or storage organs such as rhizomes or bulbs. (e) Shady plants and aquatic plants, such as algae are adapted to live in low light intensity. High light intensity is a limiting factor. They can be killed by strong light as photo-oxidation and destruction of the chlorophyll occur. (f) Desert has light intensity which is too high besides heat. Very few plants can adapt to such intensity. (g) Animals are indirectly affected by light. When there are no plants, there are no food for the animals. They migrate away from the dark tundra area during winter. (h) Blind cave fish and fish in dark ocean floors are adapted to live under dark conditions. They cannot survive and compete with those adapted to live in places with light. 6. Temperature (a) Temperature affects the population size and distribution of organisms, especially plants. It supplies kinetic energy. Temperature which is too cold or too hot is detrimental to growth. (b) Plants cannot survive in the tundra, as the temperature is too low. The tree line in Canada was further south a few thousand years ago, as digging in newly forested areas shows no plants residue older than 5,000 years. (c) The distribution of the giant Saguaro cactus (Cereus giganteus) as shown in Figure 15.15 in North America is determined by the low temperature. Areas with consecutive 36 hours of freezing temperature have no such cactus, as they are killed by freezing temperature of that length of time. (d) The distribution of butterflies of the Papilionidae family is also determined by temperature. Certain species are found only in cold Alaska whereas others are found further south. Low temperature is found to kill the southern varieties. Figure 15.15 Saguaro cactus

68 Biology Term 3 STPM Chapter 15 Ecology 15 (e) Hotspring bacteria are thermophiles. Green and colourless sulphur bacteria can survive in water of 70°C or even higher. Their enzymes are special and do not denature at that temperature. 7. Moisture (a) Water affects the population size and distribution of both plants and animals. Organisms cannot survive without the presence of water. It is a vital component and solvent within organisms. (b) Most of our tropical rainforest plants cannot survive in arid land as they are adapted to live in abundance of water. (c) The changes of forest boundary to grassland and from grassland to desert are also due to the presence of soil water concentration. More than a certain monthly rainfall can change a grassland to forest. (d) In Malaysia, the mountain forest, lowland forest and swamp forest are different because of water content in the soil. For example, nipah palms grow very well in water-logged areas. (e) Cacti are adapted to live in the desert with little rainfall per year. They can store up water in the stem or leaves immediately after the rain and survive for a year or two before the next rain. (f) Few animals can survive in the desert, as they need water to get rid of nitrogenous wastes. Only camels, kangaroo rats and desert goats can survive as they are able to make use of metabolic water. 8. Salinity (a) Salinity influences the population size and distribution of organisms because it lowers the water potential of the soil. (b) This is true especially for plants that have to absorb water by osmosis from soil water. Most plants cannot survive in low water potential as water cannot be absorbed. (c) In our coastal mangrove swamp, plants are arranged in order of salinity liking, with those salt-loving species found nearer to the sea while those that least like salinity are found inland. This is due to water diffuses down water potential gradient. (d) In the southwestern part of United States, many valleys have high salinity. The distribution of certain plants is found to be inversely proportionale to saline concentration, where more plants are found in non-salty slopes and least number of plants in the saltier valley bottoms. 9. Nutrient concentration (a) Plant density and distribution increases with more nutrient concentration in the soil. This is especially so for macronutrients like sodium, potassium and phosphorus elements and their salt ions.

69 Biology Term 3 STPM Chapter 15 Ecology 15 (b) Plants depend on nitrogen and phosphorus sources to synthesise proteins and nucleic acids. The plants absorb these elements in the forms of nitrates and ammonium ions for nitrogenous source and phosphate ions for phosphorus source. (c) Areas with high nitrogen and phosphorus content are fertile with high density of different plants. The plants can grow very well. (d) Areas with low nitrogen content only have legumes. The legumes have symbiotic Rhizobium bacteria that can fix nitrogen in the nodules of their roots. (e) In the artic areas, the lemming population is found to be influenced by mineral levels in a cyclic pattern. When their population increases, the plant population decreases, not because the plants are eaten by the animals but the mineral ions are trapped in their bodies. Only when enough animals die, then the soil is returned with enough ion concentration for the plants to grow. Biotic factors 1. Territorial behaviour (a) Territorial behaviour is the behaviour of a male or together with its female partner, fiercely guarding a territory so that other males or females are not allowed in. (b) This behaviour is found in many fish, reptiles, birds and mammals. (c) The size of the territory depends on the species of animals and their aggressiveness. A male tiger territory can be a few km2 but a male tilapia fish may be just less than a m2 . (d) This behaviour limits the population size and distribution of the animals, though it ensures that their offspring have enough to eat. That will ensure enough preys for the tiger to catch and the male tilapia can take care of the fry in its territory. (e) This behaviour also causes their population size and distribution to remain unchanged for a long time. However, the tiger population depends very much on the prey population. 2. Overcrowding (a) Overcrowding is the condition when the density of an animal’s population has reached a stage that affects its reproductive rate or fecundity that members of the population eventually leave. (b) This is found in certain birds and mammals. (c) Overcrowding stimulates the brain to respond in different manners. Language Check Language Check Infanticide = the inter national killing of infants.

70 Biology Term 3 STPM Chapter 15 Ecology 15 (d) Usually, this individual behaviour is changed in response to the secretion of certain hormones. (e) The behaviour includes the decrease in the number of gametes, refusal to mate and take care of the eggs or young, infanticide and migration. (f) This affects the population size and distribution of animals, depending on the species. So, there is usually an optimal size in an area for any population of organisms. (g) For example, sea birds like puffins choose the face of steep cliff to make nest. When the population grows larger, the competition limits the population size. The birds may move to another cliff. 3. Predation (a) Predation is a relationship in which a bigger animal, the predator, catches and feeds on a smaller animal, the prey. (b) Examples of such relationship are eagle and hare, owl and rat, tiger and deer. (c) Both populations fluctuate, as shown in Figure 15.16. Number Time Prey Predator Figure 15.16 The predator and prey relationship (d) When the population size of prey increases, the population of the predator will follow suit as there is plenty of food for the predator. (e) If the population of the prey decreases, the population of the predator will decrease too due to insufficient food. (f) When the predator is eliminated, such as the wolf population in the United States, the reindeer and bison populations increase tremendously. 4. Competition (a) Interspecific competition for food, water and mineral resources are common in both animals and plants. (b) Competition will always decrease the population of the competitors. (c) An example is wildebeest and zebra which compete for food. Either population is bigger without the other. (d) One population may increase and the other may decrease. (e) An example is the wild buffalos and elephants in the savannah of central Africa. Near water, the wild buffalos are better competitors and in drier areas, the opposite is true.

71 Biology Term 3 STPM Chapter 15 Ecology 15 (f) In another case, the population of one will increase and the other will die. This is known as Gause’s law or the competitive exclusion principle. An example is in Paramecium. When Paramecium caudatum is cultured with Paramecium aurelia, Paramecium caudatum eventually dies, as shown in Figure 15.17. Time / days 16 P. caudatum P. aurelia 8 100 200 Number Figure 15.17 Competition between two species of Paramecium 5. Parasitism (a) Parasitism is a relationship between the parasite living temporarily on the surface or more permanently inside the host, causing damage to the host. Tha parasites feed on the host. (b) The relationship affects the population size and distribution of the two organisms. (c) In areas without the host, the parasites can never live off the host. (d) In ectoparasites like mosquitoes, the number of parasites is positively correlated to that of the host. Most hosts can support more parasites. (e) For example, the annual migration of reindeer to northern Siberia increases the population of mosquitoes during the summer months. (f) For parasites that kill the host such as virus-carrying mosquitoes, the population of mosquitoes decreases when the population of host decreases. (g) For parasites that do not kill hosts such as round worms, their number depends on the cleanliness and the standard of hygiene in an area. They are almost absent in developed countries. Exam Tips Remember how the climatic and biotic factors affect the size of a population and Paramecium competition. Quick Check 3 1. Explain the meaning and importance of biotic potential. 2. How do natality, mortality, migration and survivorship affect population size and distribution? 2012

72 Biology Term 3 STPM Chapter 15 Ecology 15 15.6 Quantitative Ecology Sampling Methods Quadrat 2017 1. A quadrat is a square marked with string used to count organisms within. It can be a square wire ring, a foldable wooden frame or a plastic netting. 2. The usual size is 1 m × 1 m for grasses or small plants. It can be as small as 1 cm × 1 cm to count the distribution of colonies of unicellular algae on tree trunks or as big as 10 m × 10 m to count the distribution of certain forest trees. 3. Sampling using quadrat is for counting plants and animals that move very slowly. It can be used to estimate the number of flying insects, like grasshoppers if the square ring is placed on the grass and the number of insect flown through the ring can be noted. 4. Quadrat sampling is usually used to estimate plants that are well distributed and not arranged in rows or in gradation because of the habitat, such as near the shore. 5. The number of quadrats used depends on the size of the land or the time allocated. It may be done with a minimum of 5 or usually 10, 20, 30 or even up to 50 quadrats. 6. The quadrat may be placed systematically or at random, depending on the outline of the land and the distribution of the plants. A computer may be used to generate random coordinates and the intersections of a pair of them marking the point for placing a quadrat. 7. Three parameters are usually determined. They are species frequency, species density and species cover. (a) Species frequency or percentage frequency is the chance of finding a species within a quadrat. To find the frequency, the presence of the species is noted and the total number of quadrats with the species is then divided by the total quadrats determined. If the species is present in 2 out of 10 quadrats, then; Frequency = Total number of quadrats with the species Total number of quadrats × 100% Frequency = 2 10 × 100% = 20% Learning Outcomes Students should be able to: (a) describe the use of quadrat and line transect sampling methods and explain the advantages and disadvantages of using these methods; (b) calculate the various sampling parameters (frequency, density, cover and their absolute and relative estimations) and estimate the population size of organisms; (c) explain the pattern of distribution of organisms in an ecosystem. Systematic quadrats Random quadrats Figure 15.18 Systematic sampling or random sampling

73 Biology Term 3 STPM Chapter 15 Ecology 15 Relative frequency can also be determined using the following formula: Relative frequency = Frequency of a species Total frequency of all species × 100% (b) Species density is the number of the species per unit area, usually the number of individuals per m2 . For example, if 10 quadrats are counted and the results are as follows: Quadrat number 1 2 3 4 5 6 7 8 9 10 Number of individuals 6 3 4 8 2 7 6 5 4 5 Therefore, Density = Total number of individuals Number of quadrats Density = 6 + 3 + 4 + 8 + 2 + 7 + 6 + 5 + 4 + 5 10 = 5 per m2 From the density, the total number of plants in an area of 10,000 m2 can be determined simply by multiplying 10,000 by 5, i.e. 50,000 plants of that species. Relative density = Density of a species Total density of all species × 100% (c) Species cover is the percentage of area which is occupied by a particular species. This is done by drawing the plan on a graph paper to scale and estimate the area covered by each species in a quadrat. A more accurate way is taking a photograph from the top and using a transparent graph to estimate the total area covered by each species. (d) Relative species cover can also be estimated by using the following formula: Relative species cover = Total percentage cover of a species Total percentage cover of all species × 100% Line transect 1. Line transect is a line or string placed on land to count the number of organisms along it. 2. Such line is usually with a minimum length of 10 m for small size plants. It may be 100 m, 1 km or even more for big trees. Exam Tips Remember a quadrat sampling, procedure and conditions. 1 m 21 25 Percentage cover = – x 100% = 84% 1 m Figure 15.19 To determine the cover of a particular species drawn to scale on a graph paper 2009

74 Biology Term 3 STPM Chapter 15 Ecology 15 3. Besides plants, it can estimate insects, birds, mammals or other animals seen along the line. 4. Line transect is used to estimate plants that are arranged in rows or where there is a transition or a profile difference along a line. 5. The number of lines used depends on the size of the area. A minimum of 10 will give a reasonable estimation with accuracy. 6. The lines are placed perpendicular to the rows of plants or along the transition of changes, starting from a boundary. The boundary is usually straight. 7. An example of such sampling is to estimate the change of plant distribution as it goes inland or away from the bank of a river. Another example is distribution of organisms from the foothill to the top of a mountain or a change of altitude. 8. Three parameters are usually determined. They are species frequency, species density and species cover. (a) Species frequency or percentage frequency is the chance of finding a species within a transect line. To find the frequency, the presence of the species is noted in every interval and the total number of intervals with the species is then divided by the total number of intervals determined. If the species is present in only 33 out of 100 intervals, then; Frequency = Total number of intervals with the species Total number of intervals × 100% Frequency = 33 100 × 100% = 33% (b) Species density is the number of species per unit interval, for example 1 m. For example, if 10 intervals of first interval are counted and the results are as follow: Transect number 1 2 3 4 5 6 7 8 9 10 Number of individuals 6 3 4 8 2 7 6 5 4 5 Therefore, Density = Total number of individuals Number of intervals × 100% Density = 6 + 3 + 4 + 8 + 2 + 7 + 6 + 5 + 4 + 5 10 = 5 per m

75 Biology Term 3 STPM Chapter 15 Ecology 15 From the density, the total number of plants from the starting line, for example the riverbank, is 5 within the first metre. Further sampling along the transect enables the observation on any influence of the river on the distribution of a species of plant. Relative density can also be determined using the following formula: Relative density = Density of a species Total density of all species × 100% (c) Species cover is the percentage of the transects, which is occupied by a particular species. This is done by drawing the cross section of each plant along the line to scale and estimate the total length covered by each species in all the transects, as shown in Figure 15.20. A B C D B F E A C A Figure 15.20 To determine the cover of a particular species in 1 m interval The percentage of species cover = Total cross sectional length of a species Total length of transect × 100% A high percentage cover indicates the dominance of a species along the transect. Relative species cover can also be estimated by using the following formula: Relative species cover = Total cross sectional length of a species Total cross sectional length of all species × 100% Belt transect 1. Belt transect is the use of two lines to create a belt along it to count the organisms within. 2. Belt transect is a modified line transect to give a more accurate estimation. 3. It is to standardise the width to estimate the plants or animals within its belt rather than to take only into consideration of plants touching the line or animals seen within certain distance. 2014

76 Biology Term 3 STPM Chapter 15 Ecology 15 4. The belt may be further modified to have quadrats along it to reduce counting if it is too tedious to count all the plants. This is done as shown in Figure 15.21. Sea Quadrat Belt 1 Belt 2 Figure 15.21 Belt transect with quadrats Estimation of Population Size of Organisms Capture-recapture method 1. It is a method to estimate the number of fast moving animals in a designated area. 2. The animals include fish, amphibians, reptiles, birds and mammals. 3. Initially, the animals are caught or trapped. They are marked with non-washable stain or are tagged. 4. The numbers marked, X (=100) are released into an area where they are caught. 5. They are allowed to mix with the general population, N. The time allowed depends on the rate of movement. Animals that move slowly are allowed longer time, for example a week. 6. Traps are then set to recapture the animals. It may be a light trap for insects that are attracted to the light. It may be any other way so that the animals can be caught with ease such as using nets to catch fish. 7. The numbers trapped, Y (=80) are examined for the mark or tag. If the marked or tagged numbers are Z (=20), then the total number in the population can be estimated. 8. The formula used is Number recaptured with mark (Z) Number recaptured (Y) = Initial number marked (X) Total number in the population (N) Total number in the population is = Initial number marked (X) Number recaptured with mark (Z) × number recaptured (Y) = XY Z = 80 20 × 100 = 400 This is known as Lincoln index.

77 Biology Term 3 STPM Chapter 15 Ecology 15 9. Many assumptions are made such as: (a) The released sample mixes well with the general population. (b) The proportion of recaptured members with the mark is the same as that of initially marked member over the total population. (c) There is no death or missing of marked members. (d) There is no selective predation of marked members. (e) The recaptured members are not ‘trap-shy’ (fear of trap) or ‘trap-happy’ (like to be trapped). Quick Check 4 1. What are the advantages and disadvantages of quadrat, line transect, belt transect and capturerecapture methods? Distribution Pattern of Organisms in an Ecosystem 2017 1. The distribution pattern of organisms in an ecosystem is the manner in which different species are located. 2. Examples of land ecosystems are those found in the eight major biomes of the world i.e. tropical rainforest, temperate deciduous (broadleaf) forest, taiga (boreal forest), savannah (tropical grassland), temperate grassland, desert and tundra. 3. Examples of aquatic ecosystems are freshwater and marine ecosystem. 4. The pattern of plant distribution on Earth is as shown in the distribution of biomes. 5. The major factors that determine this huge ecosystem is the climatic condition i.e. the pattern and amount of rainfall, temperature, latitude and soil factors. 6. In each of the ecosystems and subsets of a biome, the pattern of the major vegetation will depends on the soil structure, fertility, salinity, pH and moisture content. The altitude, direction of the sun, rainfall and temperature also affect the plant distribution. 7. Malaysia lowland diptocarp forest and montane forest have different patterns of plants due to the higher moisture content and higher temperature in the lowland. Taller forest plants are found in lowlands and shorter plants including fern trees are found in highlands. 8. The distribution pattern of animals and plants in an ecosystem can be divided into three major patterns i.e. clumped distribution, regular or uniform distribution and random distribution. Exam Tips Remember how the size of an animal population can be estimated. Summary 1. Distribution pattern differs across biomes. 2. Plants and animals differ 3. Determined by abiotic factors 4. 3 patterns: (a) Clumped due to patchy resources, social factors, parental care and mechanism against predators. (b) Regular due to territorial behaviour, even nutrient distribution and manmade activities. (c) Random due to homogenous environments, consistent environmental conditions and uncontrollable factors. 2003

78 Biology Term 3 STPM Chapter 15 Ecology 15 Clumped distribution 1. It is the most common type of dispersion found in nature where the distance between neighbouring individuals is minimised. 2. This type of distribution is found in environments that are characterised by patchy resources. 3. Animals need certain resources to survive, and when these resources like water holes become rare during certain times of the year, animals tend to “clump” together around these crucial resources. 4. Individuals might be clustered together in an area due to social factors such as selfish herds and family groups. Organisms that usually serve as prey form clumped distributions in areas where they can hide and detect predators easily. 5. Other causes of clumped distributions are the offspring’s restricted mobility. This is seen in juvenile animals that are immobile and strongly dependent upon parental care. For example, the bald eagle’s nest of eaglets exhibits a clumped species distribution because all the offspring are in a small subset area before they learn to fly. 6. Clumped distribution can be beneficial to the individuals in that group. However, in some herbivore cases, such as cows and wildebeests, the vegetation around them can suffer, especially if animals target one type of plant in particular. 7. Clumped distribution in species acts as a mechanism against predation as well as an efficient mechanism to trap or corner prey. African wild dogs, Lycaon pictus use communal hunting to increase their success rate at catching prey. It has been shown that larger packs of African wild dogs tend to have a greater number of successful kills. 8. It has also been observed that extinct and threatened species are more likely to be clumped in their distribution on a phylogeny or evolutionary relationship. They share traits that increase vulnerability to extinction because related taxa are often located within habitats where human-induced threats are concentrated 9. Using recently developed complete phylogenies for mammalian carnivores and primates, it has been shown that the majority of threatened species are far from randomly distributed among taxa and phylogenetic clades. Figure 15.22 Clumped distribution

79 Biology Term 3 STPM Chapter 15 Ecology 15 Regular or uniform distribution 1. Less common than clumped distribution, uniform distribution is evenly spaced. It is found in populations in which the distance between neighbouring individuals is maximised as a result of competition for a resource or direct social interactions between individuals within the population, such as territoriality. For example, penguins often exhibit uniform spacing by aggressively defending their territory among their neighbours. 2. Plants also exhibit uniform distributions, like the creosote bushes in the south-western region of the United States. Salvia leucophylla is a species in California that naturally grows in uniform spacing. This flower releases chemicals called terpenes which inhibit the growth of other plants around it resulting in uniform distribution. This behaviour is called allelopathy. 3. Farming and agricultural practices often create uniform distributions in areas where it would not previously exist, for example, oilpams growing in rows on a plantation. Random distribution 1. Random distribution (unpredictable spacing) is the least common form of distribution in nature. 2. It occurs when the members of a given species are found in homogeneous environments in which the position of each individual is independent of other individuals: they neither attract nor repel one another. 3. Random distribution is rare in nature as biotic factors, such as the interactions with neighbouring individuals, and abiotic factors, such as climate or soil conditions, generally cause organisms to be either clustered or spread apart. 4. It usually occurs in habitats where environmental conditions and resources are consistent. This pattern of dispersion is characterised by the lack of any strong social interactions between species. For example, when dandelion seeds are dispersed by wind, random distribution will often occur as the seedlings land in random places determined by uncontrollable factors. 5. Oyster larvae can travel hundreds of kilometres powered by sea currents causing random distribution when the larvae land in random places. It is however the only dispersion that has a mathematical equation to represent it despite being random. This is due to the individualistic characteristics of random dispersion based on the idea that every species has equal opportunity and access to resources. Figure 15.24 Random distribution Allelopathy is the release of chemicals from plant parts by leaching, root exudation, volatilisation, residue decomposition and other processes. Allelopathy can have beneficial, harmful, or neutral effects on surrounding organisms. Some allelochemicals even have selective effects on surrounding organisms; for example, the tree species exudes a chemical that inhibits the growth of other plants but not those of its own species, and thus can affect the distribution of specific rival species. Allelopathy usually results in uniform distributions. Info Bio Figure 15.23 Regular distribution

80 Biology Term 3 STPM Chapter 15 Ecology 15 STPM PRACTICE 15 Objective Questions 5. Which equation is correct representing the relationship between gross primary productivity (GPP), net primary productivity (NPP) and energy used by primary producer for respiration (R)? A R=NPP-GPP B GPP=NPP-R C NPP = GPP+R D NPP=GPP-R 6. What is the actual energy that flows in an ecosystem? A The light energy which is converted to chemical energy by the producers B The energy which is transferred from the producers to the consumers C The energy used by all the organisms at every trophic level D The energy used by decomposers 7. Which statements are true of the second law of thermodynamics? I Energy cannot be created nor destroyed. II Energy is lost to the environment as heat. III Energy is transformed from one form to another. IV Energy must be continuously supplied from outside sources. A I and II C II and III B I and IV D III and IV 8. Which are the reasons for decrease in energy when it flows through a trophic level? I Loss in respiration II Breakdown by saprophytes III Transformed to storage substances IV Not assimilated A I, II and III C II, III and IV B I, II and IV D I, II, III and IV 1. Which is an abiotic component? A Heterotroph B Hydrosphere C Decomposer D Ectoparasite 2. What is an ecosystem? A All the living organisms that live in a particular area B A group of individuals of the same species living in a particular area C The entire community of species interacting with the abiotic factors in a certain area D All the areas on Earth including atmosphere, oceans and land that are inhabited by living organisms 3. The table below shows two lists of animals. List I List II (a) Flagellates (b) Guppies (c) Remora (d) Plasmodium sp. i Mosquito larvae ii Termites iii Man iv Sharks Which combination indicates their relationship? Predation Symbiosis Commensalism Parasitism A (a) (i) (b) (iii) (c) (iv) (d) (ii) B (b) (i) (a) (ii) (c) (iv) (d) (iii) C (c) (iv) (b) (i) (d) (iii) (a) (ii) D (d) (ii) (b) (i) (a) (iii) (c) (iv) 4. Which determines the carrying capacity of a population? A Natality B Limiting resources C Population growth D Mortality

81 Biology Term 3 STPM Chapter 15 Ecology 15 9. Which of the following process is represented by V, W, X, Y and Z in the phosphorus cycle? Plants Animals Dissolved phosphates Shallow sedimentation Deep sedimentation V V W X Y Z V W X Y Z A Erosion Active transport Decaying Excretion Geological upsurge B Geological upsurge Diffusion Decaying Respiration Erosion C Dissolving Active transport Excretion Decaying Geological upsurge D Sedimentation Osmosis Excretion Decaying Erosion 10. Which of the following organisms plays an important role in the sulphur cycle? I Nitrosomonas II Desulfovibrio III Thiobacillus A I only C II and III B III only D I, II and III 11. Which bacteria does not contribute to the primary productivity of an ecosystem? A Purple bacteria B Cyanobacteria C Saprotrophic bacteria D Chemosynthetic bacteria 12. Consider the efficiency of energy transfer from producers to herbivores is 10% and to the higher level is 20% and the amount of energy obtained by the secondary consumers is 48 kJ m–2y–1, calculate the net primary productivity of the producers. A 480 kJ m–2y–1 B 960 kJ m–2y–1 C 1600 kJ m–2y–1 D 2400 kJ m–2y–1 13. Why is the number of trophic levels in a food chain limited to only four or five levels? A There are different organisms that occupy different trophic levels B There are different modes of nutrition among the organisms C High amount of energy is lost at every trophic level D The food chain reaches the carrying capacity 14. Which of the following involves the greatest amount of energy transferred in the energy flow of an ecosystem? A Plant → herbivore B Plant → decomposer C Herbivore → carnivore D Carnivore → decomposer 15. Which of the following ecosystems has the pyramid of biomass as shown below? Primary consumers Producers A Tropical rainforest B Aquatic C Temperate forest D Desert 16. A sample of 80 earthworms was collected from 50 quadrats in a field. If each quadrat is 100 cm2 , what is the density of earthworms per square metre of the field? A 1.6 B 16.0 C 160.0 D 1600.0 17. What situation causes an algal bloom to occur in a pond? A Plenty of sunlight B After a heavy rain C A run-off from a nearby fertilised field D The presence of a large population of zooplankton

82 Biology Term 3 STPM Chapter 15 Ecology 15 18. The average size of birds in tropical countries is smaller than that of birds in temperate countries. Which of the following is the explanation? A Natural selection eliminates birds with high metabolic rate in tropical countries. B Larger birds have higher metabolic rate C Larger birds lose less heat D Higher temperature inhibits the growth 19. The graph below shows the changes in the following factors in a lake during one year: • Number of producers • Number of primary consumers • Quantity of dissolved nutrients • Intensity of light Which of the following curves represents producers? Number Winter Spring Summer Autumn D C B A A C B D 20. If there are 52 beetles in 40 quadrats of 10 cm2 each, what is the density of the insects per m2 ? A 130 C 5,200 B 1,300 D 52,000 21. Which of the following statements is true of natality? I The number of offspring per female per unit time II The number of eggs produced per reproductive cycle III The number of deaths per thousand individuals per year IV The number of births per thousand individuals per year A I and II B I, II and IV C I, III and IV D II, III and IV 22. Two species of Paramecium cultured separately and together produced different results as shown below: Number Separately P. caudatum P. nasutim 100 6 Number Together P. caudatum P. nasutim 100 6 What is the relationship between the two species? A Mutualism B Predation C Intraspecific competition D Interspecific competition 23. The graph below shows the mortality and natality rates of an animal. Natality rate Mortality rate Rate per population Time (year) X Which is correct at X? A Increases B Decreases C Unchanged D Increases then decreases

83 Biology Term 3 STPM Chapter 15 Ecology 15 24. Which of the following population is not facing any limiting factor? A Population size Time B Population size Time C Population size Time D Time Population size 25. In a culture of yeast maintained at 29°C, food is constantly added while toxic substances are removed. Which of the following is the pattern of growth? A Time Population size B Time Population size C Time Population size D Time Population size 26. Which about a population that grows exponentially is correct? A Growth is influenced by a high population density. B Growth is limited by the environmental resistance. C Growth starts rapidly. D Growth is unlimited. 27. In a study of a shrimp population, the mean mass is 12.3 g and the standard deviation is 1.2 g. Which of the following statements correctly describes the conclusion? I 68% of the population have masses of 11.1 g – 13.5 g II 68% of the population have masses of 12.3 g – 14.7 g III 95% of the population have masses of 9.9 g – 14.7 g IV 95% of the population have masses of 12.3 g – 14.7 g A I and III C II and III B I and IV D II and IV 28. What is the definition of carrying capacity? A The maximum population growth rate under ideal conditions B The change in the population size per individual per unit time C The maximum number of species that can live in an ecosystem D The maximum population size that can be supported by an ecosystem

84 Biology Term 3 STPM Chapter 15 Ecology 15 29. Which of the following terms means the maximum of individuals in a population that can be supported by natural resources in a given area? A Biotic potential B Carrying capacity C Population growth D Survivorship 30. A 25 cm × 25 cm quadrat is used to study the density of love grass. The result is as follows: Quadrate 1 2 3 4 5 6 7 8 9 10 Quantity 10 2 8 10 0 9 2 5 4 0 The density of love grass per metre2 is A 5 C 80 B 50 D 160 31. Which of the following is false about the r-strategist species? A The lifespan is short B The body size is small C It involves parental care D The development period to achieve maturity is short 32. A 25 cm × 25 cm quadrat is used to study the density of love grass in two areas X and Y. The result is as follows: Quadrat 1 2 3 4 5 6 7 8 9 10 Quantity at X 3 0 5 1 2 3 0 7 6 3 Quantity at Y 0 2 1 4 1 2 3 4 0 3 The density of love grass per m2 is Area X Area Y A 30 20 B 48 32 C 32 48 D 20 30 33. In an investigation to estimate the population size of a bug species by capturerecapture method, the lower surface of the bug is marked with a dye. The reason the bug is not marked on its back is because the dye A hinders the movement of the bug B damages the epidermis of the bug C makes the bug more noticeable to predators D is more visible on the lower surface of the bug 34. Which of the following is the assumption in the capture-recapture method of population size estimation? I Any death or birth does not affect the estimation II The sampling is made randomly III Marked individuals mix evenly with the general population IV The total caught that is marked must not be equal to those unmarked in the recapture A I and III B I, II and III C I, II and IV D II, III and IV 35. A sampling of soil organisms was carried out by mixing the soil with 25% of salt solution with a little benzene. What organisms were expected to float up and be collected? I Bugs with antennae II Spiders III Mites IV Slugs A III only B II and IV C I, II and III D I, III and IV

85 Biology Term 3 STPM Chapter 15 Ecology 15 36. The following table shows the number of plants per quadrat of 1 m2 . 3 8 9 7 5 2 1 8 3 2 7 7 5 4 3 6 5 4 6 6 5 4 6 4 5 The sampling was carried out in an area of 2500 m2 . If the land is 10,000 m2 , what is the total number of plant? A 125 C 12,500 B 500 D 50,000 37. The data of species X density in ten quadrats measuring 1 m2 each is given in the table below. Total number of species X in all quadrats 50 Average species coverage of X in each quadrat 0.05 cm2 What is the percentage of species coverage of X? A 0.5 C 0.005 B 0.05 D 0.0005 38. The following histogram shows the number of plants in 10 quadrats of 50 cm x 50 cm. 1 10 0 5 10 Number Quadrat number Which is the density of the plant per m2 ? A 4 C 40 B 16 D 160 39. A total number of 45 pest snails were caught from an area of farmland, marked and released back into their habitat. After seven days, 66 pest snails were caught from the same farmland of which 10 were marked. Estimate the size of the pest snail population found in the farmland. A 121 C 450 B 297 D 660 Structured Questions 1. The diagram shows three types of survivorship curves Q, R and S. 1000 100 10 0 20 40 60 80 100 Percentage of life span Number of survivors (log scale) Q R S (a) Define survivorship. [1] (b) Label and explain the survivorship curves of Q, R and S. [3] (c) State one example of organism exhibiting the survivorship curve of Q. [1] (d) Name three density-independent factors that affect the size of population. [3]

86 Biology Term 3 STPM Chapter 15 Ecology 15 2. In an experiment done by G.F. Gause, two different species of paramecium, that is P. aurelia and P. caudatum, have been cultured in test tubes with limited resources. The result of the experiment is shown in the graph below. Relative population density P. aurelia P. caudatum Separately Mixed population Separately Mixed population 200 150 100 50 0 Days 24222018161412108642 200 150 100 50 0 (a) Explain why the curves which resulted from the mixed cultures of both paramecia are as such. [3] (b) State five possible characteristics of P. aurelia which can be deduced from the experiment. [5] (c) What conclusion can be made from the experiment? [2] 3. The diagram below shows the flow of energy through a forest ecosystem. All figures are in kJ m–2 year–1. Light energy absorbed by producers 1.88 x 106 Producers trapped energy and convert it into biomass = 99168 Primary consumers 3838 22228 44118 Secondary consumers 228 Tertiary consumers Respiration and heat loss Detritus Decomposers (a) How is energy made available to the primary consumers? [1] (b) Calculate the efficiency of energy transfer between the secondary consumers and tertiary consumers using the formula: Energy available to tertiary consumers Energy available to secondary consumers × 100% [1]

87 Biology Term 3 STPM Chapter 15 Ecology 15 (c) What is the advantage of omnivores such as monkeys that feed on different trophic levels? [2] (d) Explain how two abiotic factors affect the energy flow. [2] (e) Explain how two biotic factors affect the energy flow. [2] (f) Explain the relationship of energy flow and carbon cycle. [2] Essay Questions 1. (a) What is meant by carrying capacity? How is the concept used in the management and conservation of forests? [6] (b) Differentiate the characteristics of r-selected and K-selected species.[6] 2. (a) Define population distribution and the population density. [2] (b) Give four advantages of quadrat sampling method. [4] (c) There are various patterns of the plant distribution especially in the forest. Explain the patterns of plant distributions. [9] Quick Check 1 1. • Sunlight energy enters the pond not just by the photoautotrophs in the pond but also the plants around the pond. The leaves that fall into the pond also contribute source of energy. • The photoautotrophs include submerged plants, floating plants, algae and photosynthetic bacteria. • The fine producers such as algae and bacteria are eaten by microscopic animals such as protozoa, insect larvae, fine round worms and annelids, and fish fry. • Water weeds are eaten by herbivorous fish, snail and water birds. • These microscopic animals are eaten by bigger crustaceans like crayfish and fish. • Then, the aquatic animals are eaten by top predators such as kingfishers and other predatory birds and snakes. • When the organisms die, they are eaten by scavenger fish and decomposed by bacteria and fungi. Quick Check 2 1. • The aim is to maintain biodiversity and prevent destruction of the environment, including the climate. • Remedial actions have to be taken early if there is a first sign of environmental change, such as the thinning of ozone and global warming. • Concerted actions by world bodies are required in the conservation of ecosystems, such as tropical rainforests and coral reefs. Quick Check 3 1. • Biotic potential is the maximum growth rate of a species i.e. to reproduce in a condition with ideal unlimited environmental resources. • Specieswith high biotic potentialwill not become extinct, especially in an environment with many limiting factors. 2. Natality, longer survivorship and immigration increase while mortality, shorter survivorship and emigration decrease population size and distribution. ANSWERS

88 Biology Term 3 STPM Chapter 15 Ecology 15 Quick Check 4 1. • Quadrats are used to determine even distribution and give wrong information if used for estimation in areas with gradual changes. • Line transect gives estimation of changes across a gradation of environmental differences and give meaningless estimation across a uniform landscape. • Belt transect gives better estimation within two lines rather than depending on plants touching the line but the width is arbitrary. • Capture-recapture method gives a fast estimation of fast-moving animals but its accuracy for insects with short lifespans are questionable. STPM Practice 15 Objective Questions 1. B 2. C 3. B 4. B 5. D 6. B 7. C 8. B 9. A 10. C 11. C 12. D 13. C 14. B 15. B 16. C 17. C 18. C 19. C 20. B 21. B 22. D 23. A 24. B 25. C 26. A 27. A 28. D 29. B 30. C 31. C 32. B 33. C 34. B 35. C 36. D 37. D 38. B 39. D Structured Questions 1. (a) Survivorship means the percentage of survival plotted against the age of the organism. (b) Q: Die only when old, high medical standard prolongs life R: Die evenly throughout, genetically determined. S: Die young and old, poor medical standard. (c) People in developed countries like Japan (d) • The size of the organism • The number of gametes produced each time • The caring of young for animals 2. (a) P. caudatum can compete better before the 10th day in mixed population. P. aurelia can compete better after the 10th day in mixed population. P. caudatum population increased to maximum density on the 8th day due to better environment which then started to decrease as the environment conditions worsen an until day 24. (b) 1. The size of P. aurelia is smaller. 2. P. aurelia can live with less food. 3. P. aurelia has a reproduction which is not affected by crowding. 4. P. aurelia is not affected much by waste products. 5. P. aurelia might release toxins that kill P. caudatum. (c) Two species competing for the same limited resources cannot coexist in the same place at the same time. One ‘stronger’ species will eventually completely exclude the less efficient species resulting in the decrease in its population. 3. (a) It is through photosynthesis by producers in the form of biomass. (b) 228 3 838 × 100% = 5.94%. (c) They are provided with more types of food. The chances for them to survive would be better if one type of food is wiped out. (d) One factor is drought when there is no water. The plants does not grow well and some die. Another factor is when there is increase in temperature that kills some temperaturesensitive plants. (e) One factor is the increase in the number of herbivores. This will destroy more plants and more energy flow to the consumers. Another factor is disease. It will decrease the number of organism at any level and stop the energy flow. (f) The energy from the sun is trapped by producers by fixing carbon dioxide, converting it into chemical energy in the form of carbohydrates. When the animals eat the plants, the chemical energy in the form of carbohydrates, mainly cellulose, is passed on to the animals. Essay Questions 1. (a) • Carrying capacity is the maximum number of individuals of a species that an environment can indefinitely support. • This is the reference point in the management of an ecosystem with the intention to collect the maximum resource from it and be able to perpetually sustain. • Extraction of timber from forests should take into consideration the population size or the carrying capacity of each type. • The time taken for the tree to reach maturity when they can produce seed or to reach a circumference of extractable size should be studied and recorded. • If all trees of extractable size are felled, the possibility of natural replacement is studied or it is replanted for sustainable extraction in the future. • The effect of extraction on other species should be studied inclusive of the time for recovery or belt should be left untouched for faster recovery. • One third of the nation’s land should be kept untouched as forest to maintain the gene pool.

89 Biology Term 3 STPM Chapter 15 Ecology 15 • The other species especially animals are studied as they may affect the plant reproduction or growth. (b) • r-selected species are of small size, whereas K-selected species are of big size. • r-selected are of short life span, whereas K-selected are of long lifespan. • r-selected are very well adapted in the new environment, whereas K-selected are not. • r-selected are lacking in defence system, whereas K-selected have good defence system. • r-selected reproduce very rapidly, whereas K-selected reproduce very slowly. • r-selected do not take care of their young, whereas K-selected do take care of their young. 2. (a) • Population distribution is the ways of organisms are found in various places within an ecosystem. • Population density is the number of individuals per unit square of the area in which the members of a group are found living. (b) • Needs minimum time to estimate the number, density and cover for plants and animals that move very slowly. • Can estimate the number, density and cover of plants especially if they are distributed uniformly in an accurate way. • Requires minimum amount of apparatus; only strings and measuring tape. • Requires minimum cost and labour. (c) • One pattern is clumped distribution where the plants are found in groups due to various environmental factors. • One of the factorsisthe watersupply. Hence, plants that like water are clumped in low lying areas including along river banks and lakes. • Another factor is cool temperature like tree ferns and certain pines found cluster on the top of hills. • Regular or uniform pattern has plants distributed in even spacing especially due to human farming. • In nature such pattern is common in areas where the texture of the soil is more or less the same like in lowland forest. • Some plants produce terpenes that inhibit the germination or growth of the same species. • Random distribution seems not common in plants as there is no fixed pattern and unpredictable not to be uniform or clustered. • One example is the seed dispersal by wind as in dandelion due to the unpredictable direction of wind and soil condition that allow germination. • Another example is seed dispersal by animals after swallowing whole seeds and the random disposal causing random distribution.

CHAPTER Bilingual Keywords SELECTION AND SPECIATION Concept Map 16 Paleontology: Kajian fosil Disruptive selection: Pemilihan berporak poranda Niche: Nic Kline: Ahli berfinotip beza Sympatric: Dipencil secara pembiakan Finches: Burung cak Transient: Sementara Deme: Ahli selalu bergaul Allopatric: Dipencil secara fizik Adaptive radiation: Penyebar menyesuai Selection and Speciation Natural and artificial selection Continuous and discontinuous variations in relation to selection and speciation Modes of natural selection Sexual selection and polymorphism with examples Importance of artificial selection Speciation Gene bank Germplasm bank Genetic drift Isolation Sperm bank Hybridisation Adaptive radiation Importance of speciation in relation to evolution

91 Biology Term 3 STPM Chapter 16 Selection and Speciation 16 Introduction 1. Selection is the choosing of individual by man or nature, permitting it to live, depending on the genotype as expressed in the phenotype in an environment. 2. Those with advantageous characteristics are able to live longer and reproduce i.e. able to mate with the opposite sex if they are animals or can cross or self fertilize if they are plants. 3. Their genes are passed on to the next generation through the offspring they produce. Those with no advantageous characteristics will die and leave no offspring. 4. The importance of selection is to change certain characteristics of the future generations that are able to adapt to the environment. 5. There is a relationship between selection and variation. Variation is the substrate of selection. 6. Speciation is the formation of new species from existing one or two species. 16.1 Natural and Artificial Selection Variation (Meaning and relation to selection and speciation) 1. Variation is the character differences that exist among members of the same species of organisms. Such variation includes differences in phenotypes, as a result of structural, physiological and biochemical changes. Variation is the raw material for selection. If there are more variable characters among the population, then it is easier for some to be selected to suit a certain environment. 2. Variation is important for the survival of a species of organism. For example, if a population is uniform and do not have the genes that are resistant to a certain disease and an outbreak of that disease occurs, the whole species will die. Therefore, in the outbreak of any disease, a variable population will have some which are resistant to the disease. 3. Variation enables certain members of a species to be selected to live in certain environments. For example, the white peppered moths are adapted to live in clean environments and the black peppered moths in dirty industrial areas. This is due to their colour as means of comouflage with their respective environments, protecting them from predators. Learning Outcomes Students should be able to: (a) describe continuous and discontinuous variations in relation to selection and speciation; (b) explain the modes of natural selection (stabilising, directional and disruptive) and their consequences; (c) describe with examples, sexual selection and polymorphism; (d) explain the importance of artificial selection (gene bank, germplasm bank and sperm bank).