School Science Health & Physical Education 6

4.2 Ecosystem

Key terms of the unit

Ecosystem: Ecosystem is the continuous interaction between living things
themselves and with the non-living things in the environment.

Abiotic components: Non-living things such as air, water, soil, sunlight etc. in
an ecosystem are called abiotic components.

Biotic components: Plants, animals and microorganisms present in our
surroundings are living things. They are called biotic components of the
ecosystem.

Producers: All green plants like algae, moss, fern, grass, food crops, vegetables,
fruits etc. are producers.

Consumers: All animals in an ecosystem are consumers.

Primary consumers: Some animals eat only plants and products of plants They
do not eat flesh. These animals are called primary consumers. Primary
consumers are called herbivores.

Secondary consumers: There are some animals that eat flesh of other animals.
They are called secondary consumers.

Tertiary consumers: Animals in an ecosystem that depend on primary
consumers for their survival are called tertiary consumers.

Decomposer: Decomposer is an  organism  that decomposes or breaks down
organic material such as the remains of dead organisms.

Aquatic ecosystem: The continuous and complex relationship between living
beings themselves and with their non-living environment in water is called
aquatic ecosystem.

Terrestrial ecosystem: The continuous and complex relationship between
living beings themselves and with their non-living environment in land is
called terrestrial ecosystem.

Forest ecosystem: The continuous and complex relationship between living
beings themselves and with their non-living environment in forest is called
forest ecosystem.

Living and non-living things closely interact in the environment. Living things
need air, water, sunlight and soil for survival. After death, their bodies decompose
in the soil, releasing nutrients that help the plants grow. So, this close interaction

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between living and non-living things, known as an ecosystem, is always at work
in the environment. An ecosystem is the continuous interaction between living
things among themselves and with the non-living things of the environment.
There are two major components in an ecosystem: abiotic and biotic.

Abiotic components

Non-living things such as air, water, soil and sunlight are abiotic components of
an ecosystem. The sun provides light and heat to plants and animals. Plants
perform photosynthesis in the presence of sunlight. In this process, they release
oxygen into the atmosphere. Animals use the oxygen for respiration. Plants and
animals also need water for survival. Terrestrial plants grow on land. Terrestrial
animals are also active on land. Human beings live on the land, too. So, the abiotic
components of the ecosystem play a vital role in the sustainability of the plants
and animals on the earth.

Biotic components

Plants, animals and microorganisms present in our surroundings are living
things. They are called biotic components of the ecosystem. They depend on non-
living things for their survival. On the basis of their food habits, biotic components
are classified as producers, consumers and decomposers.

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Producers (autotrophs)

An ecosystem has a large number of producers. Green plants such as algae, moss,
fern, grass, food crops, vegetables and fruits are producers. They prepare their
own food by way of photosynthesis. Despite being self-producers of food, plants
cannot make food without air, water, sunlight and heat. The food of plants is
called starch. Producers, or the plants, provide food to animals.

moss fern grass paddy fruit tree

Consumers (heterotrophs)

Animals in an ecosystem are consumers. They do not make their food. They
consume the food prepared by plants. Directly or indirectly, both terrestrial and
aquatic animals depend on plants for their food. They get their food from plants
in different ways. Based on how they consume food, consumers are also classified
into three categories: primary, secondary and tertiary.

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Primary consumers

Some animals eat only plants and products of plants. Cows, buffaloes, goats,
deer, rabbits, horses and grasshoppers are examples. They do not eat flesh. These
animals are called primary consumers. Primary consumers are called herbivores.
Herbivores are the food of carnivores.

grasshopper rabbit giraffe elephant

Secondary consumers

Some animals, called carnivores, eat the flesh or meat of animals. Other animals,
called ominvores, eat both plants and animals. They are all secondary consumers.
Secondary consumers depend on producers and primary consumers for food.
Examples of secondary consumers are frogs, snakes, crows, foxes, dogs and cats.
Secondary consumers are fewer in number than primary consumers.

frog crow snake

dog fox leopard

Activity

List the major producers and their consumers found in your surrounding
environment.

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Tertiary consumers

Animals in an ecosystem that depend on primary consumers and secondary
consumers for survival are tertiary consumers. They are tigers, sharks, lions,
snakes, pythons, eagles, etc. These animals eat the flesh of primary and secondary
consumers. They are top carnivores.

shark python tiger eagle lion

Environment and rank of consumers

The rank of consumers depends on the type of ecosystem in which they are
present.

Producers Primary Secondary Tertiary Top tertiary
Grass consumer consumer consumer consumer

Grasshopper Frog Snake Eagle

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Decomposers

Activity

Discuss in the class what would happen if no dead animal or plant on the earth
ever got rotten or decomposed.

Nature has a way to strike a dynamic balance between living and non-living
worlds. When a living being dies, it mixes into soil through the action of
decomposers. The components from the living world get mixed into the non-
living world. Decomposers are organisms that break down the organic materials
from the remains of the dead animals and plants. These tiny little creatures get
their energy from eating the organic material from the dead bodies. Decomposers
include bacteria and fungi. Mushrooms are a type of fungus that have a role in
the decomposition.
Decomposers play an important role in every ecosystem. Decomposition allows
organic materials to be recycled into the ecosystem. Without decomposers, dead
organisms would not be broken down and recycled into other living matters.
This process goes on in the ecosystem forever.

Types of ecosystem

Broadly, ecosystems can be divided into two groups: aquatic and terrestrial.
Aquatic ecosystem
Water bodies have an aquatic ecosystem. The continuous and complex relationship
between living beings themselves and their non-living environment in water is
called an aquatic ecosystem. The type of water such as freshwater or saltwater
determines which animals and plants live there. A pond ecosystem is an example
of an aquatic ecosystem as well.

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Terrestrial ecosystem
The continuous and complex relationship between living beings themselves and
their non-living environment in land is called a terrestrial ecosystem. Examples
of terrestrial ecosystems are a forest ecosystem, a grassland ecosystem and a
desert ecosystem. In this unit, we will focus on a forest ecosystem.
Forest ecosystem
The continuous and complex relationship between living beings themselves and
their non-living environment in a forest is called a forest ecosystem. It is a dynamic
and complex relationship of plants, animals and micro-organisms with abiotic
components of the forest. Trees are the key components of a forest ecosystem.
Forest ecosystems differ from one another based on the type of forest in question.

Fig : forest ecosystem

Both abiotic and biotic components are similar in almost all ecosystems. However,
they are affected by various abiotic factors, humidity, air, heat, light, minerals,
etc. In a forest ecosystem, trees and climbers are producers. Producers transfer
their food energy to primary consumers.
a. Abiotic components of the forest ecosystem
Abiotic components of a forest ecosystem are air, water, soil, heat, light,
minerals, humidity, etc.

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b. Biotic components of the forest ecosystem
Biotic components of the forest ecosystem include produces (plants),
consumers (animals) and decomposers (fungi and bacteria).
Green plants are called producers. This is because they produce food for
themselves as well as for animals. Consumers consume food prepared by the
green plants. In the forest ecosystem, primary consumers are insects, squirrels,
porcupines, deer, monkeys, zebra, elephants, rhinos, wild buffaloes, etc. They eat
plants or products of plants. The food energy is transferred from primary
consumers to secondary consumers when animals such as toads, wolves, snakes,
bears, etc. eat primary consumers. The tertiary or top consumers of the forest
ecosystem, for example, are leopardsand owls. From secondary consumers, food
energy passes to tertiary consumers or top consumers.
Dead plants and animals or their parts are eaten by bugs and beetles. The
remaining matter is digested by decomposers, namely, bacteria and fungi.
Decomposers break those organic matters into simpler substances like minerals.
These minerals make the soil fertile for the growth of plants. This way, a forest
ecosystem continues to exist.

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Fact file

Half the world's species live in tropical rainforests.

Importance of ecosystem

a. An ecosystem provides habitat for plants and animals.
b. It provides air, water and minerals for regulating life processes.
c. It provides food to living beings.
d. It recycles nutrients between biotic and abiotic components.
e. Humans obtain all goods and services from the ecosystem.

Project Work

What type of ecosystem is found in your surrounding environment? Name its
type and list the producers as well as the primary, secondary and tertiary
consumers there.

Exercise

1. Tick the correct alternative from the given options.
a. Large fish in a pond ecosystem is an example of……….

i. producer ii. primary consumer

iii. secondary consumer iv. tertiary consumer

b. Which biotic component is mostly found in a grassland ecosystem?

i. producers ii. primary consumers

iii. secondary consumers iv. top carnivores

c. Tree leaves, monkey and leopard are the components of …..

i. a pond ecosystem ii. a forest ecosystem

iii. a marine ecosystem iv. all of them

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d. Which is an abiotic component of ecosystem?

i. air ii. water iii. sunlight iv. all of them

e. Which biotic component cleans the environment?

i. producers ii. consumers iii. decomposers iv. all of them
2. Fill in the blanks with appropriate words.

a. Primary consumers are also known as …………………….

b. Tertiary consumers are sometimes also known as ………….. carnivore.
c. ………………. and …………… are the examples of decomposers.

d. …………………. break complex molecules to release energy for living

beings.

e. All producers have green pigment called ………………….

3. Write True for correct and False for the incorrect statements.
a. An ecosystem is the result of interaction between living and non-living
things.
b. Autotrophs cannot make their own food.
c. Grass, rabbit, fox and lion are parts of a forest ecosystem.
d. Algae are the primary consumers of pond ecosystem.
e. Fungi are the decomposers of the ecosystem.

4. Match the following:

Grass primary consumer

Grasshopper secondary consumer

Frog decomposer

Snake producer

Eagle top carnivore

Fungi tertiary consumer

5. Write your answer to the following questions in a word each.
a. From where does the energy for the ecosystem come?
b. What types of components are air, water, soil, and sunlight?

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c. Which component of the ecosystem produces food?
d. Which component of the ecosystem does bacteria belong to?
e. Which group is responsible for recycling nutrients into the ecosystem?
6. Write two differences between:
a. Biotic and abiotic components
b. Producers and consumers
7. Give reasons:
a. Sunlight is the ultimate source of energy in the ecosystem.
b. Bacteria and fungi are called the cleaner of the ecosystem.
c. Green plants are called producers of the ecosystem.
d. Animals are called consumers of the ecosystem.
8. Look at the following figures and name the type of ecosystem.

9. Define the following terms with appropriate examples of each.
i. Ecosystem ii. Producers iii. Consumers iv. Decomposers
v. Aquatic ecosystem vi. Terrestrial ecosystem vii. Forest ecosystem
10. Answer the following questions.

a. What types of consumers are there in an ecosystem? Describe their
features with two examples of each.

b. List any four important aspects of the ecosystem for humans?
c. Draw a neat diagram of a forest ecosystem showing producers,

consumers and decomposers.
d. What is the role of the decomposer in an ecosystem?
e. Explain the consequences of a forest ecosystem if all deer are killed.

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Unit Estimated Teaching Periods:

5 Life Processes Theory Practical
8 2

Topics in Their Order according to CDC Curriculum

1. Introduction to mode of nutrition
2. Types of nutrition
3. Autotrophic mode of nutrition
4. Heterotrophic mode of nutrition (holozoic, parasitic and saprophytic)
5. Introduction to photosynthesis, its importance and process
6. Introduction to digestion
7. Human digestive system and process of digestion

Learning outcomes

At the end of this unit, students will be able to:
1. Show they understand the mode of nutrition.
2. Discuss photosynthesis and its importance.
3. Discuss human digestive system and its processes.

Learning outcomes

Life processes: All the systematic activities that are performed by a living body
are known as life processes.
Nutrients: Nutrients are those substances that are required by the body of living
organisms for their proper growth and development.
Nutrition: The process by which living beings obtain food and utilize nutrients
present in it is called nutrition.
Autotrophic nutrition: The mode of nutrition which is shown by autotrophs or
producersis called autotrophic nutrition.
Heterotrophs: Those living organisms that depend upon others for their food
are called heterotrophs or consumers.

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Heterotrophic nutrition: The mode of nutrition which is shown by heterotrophs
is called heterotrophic nutrition.

Holozoic nutrition: Holozoic nutrition involves the ingestion and internal
processing of solid and liquid food in an organism.

Herbivores: Herbivores depend upon plants for their food.

Carnivores: Herbivores feed on other animals for their food.

Omnivores: Omnivores feed on plants and animals for their food.

Saprophytes: Those organisms which feed on dead and decayed organisms for
their food are called saprophytes.

Saprophytic nutrition: The nutrition shown by saprophytes is called saprophytic
nutrition.

Parasites: Those organisms which take their food from the living body(host) of
other organisms are called parasites.

Parasitic nutrition: The nutrition shown by parasites is called parasitic nutrition.

Digestion: Digestion is a process of breaking down of complex substances in
the food into simpler and absorbable forms.
Glands: Those organs which secrete enzymes are called glands.

Digestive tract: The passage along which food passes through the body from
the mouth to the anus during digestion process is called alimentary canal or
digestive tract.

Digestive glands: Digestive glands are the organs that secrete enzymes for the
digestion of food.
Villi: Villi help to absorb the nutrients present in the digested food.

Egestion: The undigested food moves to the rectum and is excreted out from
the body through the anus. This process is called egestion.
Photosynthesis: Photosynthesis is a process in which green plants and certain
micro-organisms prepare their own food in presence of chlorophyll by using
carbon dioxide and water as raw materials and sunlight as a sources of energy.

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Life processes are systematic and basic functions performed by living organisms
to survive on the earth. They include photosynthesis, respiration, transportation,
digestion, excretion, reproduction, circulation, control and coordination and
growth. All the systematic activities that are performed by a living body are
known as its life processes.

Respiration Movement
Metabolism

Transportation Life Growth
Processes

Excretion Reproduction

Nutrition

Nutrients

Living beings need food to survive. Food provides necessary nutrients to the
body. These nutrients provide energy for their proper growth and development.
Nutrients are substances that are required by the body of living organisms for
their proper growth and development. Broadly, nutrients are divided into
carbohydrates, proteins, fats, vitamins and minerals.

Nutrition

Nutrition is an organic process. In this process, living organisms obtain food and
use it for growth, metabolism, repair, etc. Thus, the process by which living
beings obtain food and utilise nutrients present in it is called nutrition. In short,
nutrients are the substances obtained from food and nutrition is the process to
obtain these substances.

Fact file

Holozoic nutrition includes ingestion (eating), digestion, absorption,
assimilation and excretion.

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Modes of nutrition

Plants and animals show two modes of nutrition: autotrophic and heterotrophic.
a) Autotrophic nutrition
Autotrophic nutrition is a process where a green plant prepares its own food
from simple inorganic materials such as water, mineral salts and carbon dioxide
in the presence of sunlight. This process of making food is called photosynthesis.
Thus, the mode of nutrition which is shown by autotrophs or producers (green
plants) is called autotrophic nutrition.

Fact file

Living organisms that prepare their own food by using inorganic substances
are called autotrophs or producers.

Fig: green plants conducting photosynthesis

b) Heterotrophic nutrition
All animals and non-green plants are called heterotrophs. This is because they
are unable to prepare their own food. These organisms directly or indirectly
depend on others for their food. Thus, the living organisms that depend on others
for their food are called heterotrophs or consumers. Similarly, the mode of
nutrition which is shown by heterotrophs is called a heterotrophic nutrition.

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Types of heterotrophic nutrition

In nature, organisms show various types of heterotrophic nutrition as follows:
a. Holozoic Nutrition b. Saprophytic Nutrition c. Parasitic Nutrition

Holozoic nutrition

Holozoic nutrition involves the ingestion and internal processing of solid and
liquid food in an organism. Generally, holozoic nutrition involves five steps.
They are ingestion, digestion, absorption, assimilation and excretion.

Ingestion is the intake of a solid or liquid food as a whole. This food is broken
down into simpler organic matters by a process called digestion. After digestion,
the useful nutrients are absorbed in the body. This process is called absorption.
The absorbed nutrients are utilised in the body for energy, growth, repair, etc. It
is called assimilation. Finally, the unwanted and undigested food particles are
excreted out from the body by a process called excretion.

Organisms which show holozoic nutrition can be divided into three types:

Herbivores:   These animals depend on plants for their food. Cows, buffaloes,
deer, elephants, etc. are examples of herbivores.

cow eating grass buffalo eating grass deer eating grass elephant eating grass

Carnivores:  These animals feed on other animals for their food. Lions, tigers,
leopards, etc. are examples of carnivores.

lion eating flesh tiger eating flesh leopard eating flesh

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Omnivores: These animals feed on plants and animals for their food. Humans,
dogs, cats, bear, etc. are examples of omnivores.

dog eating meat dog eating rice cat eating milk cat eating meat

Saprophytic nutrition

Organisms which feed on dead and decayed organisms for food are called
saprophytes. For example, bacteria and non-green plants such as mushroom,
mucor, yeast are saprophytes. The nutrition shown by saprophytes is called
saprophytic nutrition. Saprophytes are an important part of the ecosystem. This
is because they help keep our environment clean and recycle nutrients back into
the ecosystem.

bacteria mushroom mucor yeast

Parasitic nutrition

Organisms which take their food from the living body of other organisms (hosts)
are called parasites. Most parasites are harmful to the health of hosts. Sometimes,
they even kill the host. Both animals and plants may serve as a host. Examples of
parasites are louse on a human head, cuscuta plant and tapeworms. The nutrition
shown by parasites is called parasitic nutrition.

mosquito bed bug tapeworm leech

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Human digestive system

Food provides energy to our body. But, all the food we eat does not convert into
energy. It is ofen a combination complex substances. Our body cells cannot
consume the substances as they are. The food is first broken down into simpler
substances for our body to absorb the nutrients. This process is called digestion.
Digestion is a process of breaking down the complex substances in the food into
simpler and absorbable forms. Digested food is absorbed by our body and
undigested materials are excreted out. In digestion, there are two main processes
involved. They are: a) Mechanical process b) Chemical process

The mechanical process involves the grinding of food materials into smaller
pieces with the help of different sets of teeth. The chemical process involves the
chemical breakdown of food due to the action of various digestive enzymes. The
organs which secrete enzymes are called glands. Different glands help in the
digestion of different substances present in food. The human digestive system is
made up of two main parts: (A) Alimentary canal (B) Digestive glands

Fact file

1. The approximate surface area of the small intestine is 2,700 square feet which covers
half the size of a basketball court.

2. Salivary glands produce 1 to 3 litres of saliva on a day.

3. The whole digestive tract is over 29 feet long, starting at the mouth and ending at
the anus.

4. The large intestine is approximately 5 feet in length.

a) Alimentary canal (digestive tract)

The passage along which the food passes to our
the body from the mouth to the anus during the
digestion process is called the alimentary canal or
digestive tract. The alimentary canal of human
beings is composed of mouth, pharynx, oesophagus
(food pipe), stomach, small intestine, large
intestine, rectum and anus. On its passage in the
alimentary canal, food comes into contact with
different digestive enzymes. Accessory organs
help the process of digestion. They include teeth,
tongue, salivary glands, liver, gallbladder and
pancreas. The food may not pass through all these
organs but they are important in the digestion
process.

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b) Digestive glands

Digestive glands are the organs that secrete enzymes for the digestion of food.
Similarly, enzymes are special chemical proteins that act as catalysts in various
biochemical processes. Enzymes perform the chemical breakdown of the food so
that the food becomes absorbable for the body cells. Salivary gland, gastric gland,
liver, pancreas and intestinal gland secrete specific substances or enzymes to act
on the specific substances in food.

Reason to remember

The salivary gland is also known as the digestive gland, why?

The salivary gland is also known as the digestive gland because it secretes
saliva that helps in the digestion of carbohydrates.

Process of digestion of food

Ingestion means the intake of food through the mouth. The tongue, teeth and the
salivary glands help in the digestion of food in the mouth. Teeth grind the food
into smaller pieces. Salivary glands secrete saliva that moistens the food and
begins the digestion of starch. The saliva contains an enzyme called salivary
amylase (ptyalin) which converts starch into maltose. Taste buds in the tongue
taste the food. The tongue helps lubricate the food and push it into the pharynx
for swallowing.

The pharynx passes the chewed food from the mouth to the food pipe or the
oesophagus. The oesophagus is a muscular tube connecting the pharynx to the
stomach. It carries the swallowed mass of chewed food along its length and drops
it into the stomach.

The stomach is a muscular sac that stores food for digestion. It secretes a gastric
juice which contains chemicals called pepsin and renin. It also produces
hydrochloric acid. The rhythmic contraction of stomach crushes the food and
mixes it with gastric juice and hydrochloric acid. In stomach,
i. Pepsin acts on proteins and converts them into peptones.
ii. Renin acts on milk protein (casein) and converts it into insoluble curd

(paracasein).
iii. Hydrochloric acid kills microorganisms in the food and provides an acidic

environment for pepsin to work.

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After upto a 3-hour long digestion, the food passes from the stomach to the small
intestine in the form of a thick paste called chyme. The small intestine is a long,
thin tube, about one inch in diameter and about 10 feet long.

The internal surface of the small intestine is full of many ridges and folds. These
folds are used to maximise the digestion of food and absorption of nutrients. The
small intestine is divided into three parts: the upper duodenum, the middle
jejunum and the lower ileum.

In duodenum, the liver secretes the bile juice, which converts large fat globules
into tiny fat droplets and makes the food alkaline. This process is called
emulsification of fat. Pancreas also secretes the pancreatic juice that contains
enzymes called trypsin, amylase and lipase.

i. Trypsin converts proteins into peptides.

ii. Amylase converts starch into maltose.

iii. Lipase converts fats into fatty acids and glycerol.

The food then passes from the duodenum to ileum. In ileum, the intestinal juice
secreted by intestinal glands acts on it. The intestinal juice contains four enzymes.
They are Erepsin, Maltase, Lactase and Sucrase.

i. Erepsin digests peptides and converts them into amino acids.

ii. Maltase digests maltose and converts it into glucose.

iii. Lactase digests lactose and converts it into glucose and galactose.

iv. Sucrase digests sucrose and converts it into glucose and fructose.

This way, carbohydrates (starch), proteins and fats get digested into simpler
soluble substances in the small intestine. The inner wall of the small intestine is
densely folded to maximize the surface area that comes in contact with digested
food. Small projections called villi are present in the inner wall of the small
intestine. Villi projections help absorb the nutrients present in the digested food.
Small blood and lymphatic vessels connected with the villi absorb the digested
food molecules and transport them throughout the body through the blood
stream. This process is called absorption.

The undigested food material then passes to the large intestine. The large intestine
absorbs most of the water from the undigested food. Finally, the remaining
substances move to the rectum and are excreted out of the body through the
anus. This process is called egestion. This way, for the digestion process to
complete in the human body, a series of actions have to happen: ingestion,
secretion, mixing and movement, digestion, absorption and egestion.

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Reason to remember

Why is amylase called the digestive enzyme?
Amylase is called the digestive enzyme because it changes starch into maltose.

Photosynthesis

Photosynthesis is a process in
which green plants and certain
micro-organisms prepare their
own food in the presence of
chlorophyll by using carbon
dioxide and water as raw materials
and sunlight as a source of energy.
In photosynthesis, green plants
and certain microorganisms
transform the light energy into
chemical energy. During
photosynthesis, green plants
capture sunlight as a source of
energy. This energy is used to
convert water and carbon into an
oxygen and energy rich organic
compound called glucose. Photosynthesis takes place in green plants, euglena
and certain bacteria. The overall chemical reaction involved in photosynthesis is
given below:

Carbon dioxide + Water → Glucose + Oxygen

Glucose formed as a product of photosynthesis is used by plants. Excess glucose
is stored as starch. All animals directly or indirectly depend on plants for their
food. Oxygen is the by-product of photosynthesis. During respiration, living
organisms take in the oxygen and release carbon dioxide into the atmosphere.

Activity

Objective: To show that starch is present in the green leaves.

Requirement: Beaker, fresh green leaf, petri dish, distilled water, ethanol (90%),
iodine, forceps, burner and dropper

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Methods: Take a fresh green leaf and boil it in the beaker for about two minutes.
Boiling removes the hard and water-proof covering of the leaf. Take out the leaf
using forceps and again boil it for about one minute in 90% ethanol solution.
Boiling in ethanol removes chlorophyll from the leaf. Take out the leaf and put
it in a petri dish. Wash the leaf with distilled water and add some drops of
iodine on the leaf surface.
Observation: The leaf turns blue-black in colour. This is because the starch
reacts with iodine to form a blue-black colour.
Conclusion: This experiment proves that green leaves contain starch in them.

Reason to remember

1. Leaves are called the kitchen of plants, why?
Leaves are called the kitchen of plants because they prepare food in the
presence of carbon dioxide, water and sunlight.

2. Animals would not exist if there were no plants, why?
Animals depend on plants for their food. So, animals would not exist if there
were no plants.

Requirements for photosynthesis

Chlorophyll
Plants can synthesise food but animals cannot because plants have chlorophyll in
them while animals do not. Chlorophyll is found in the chloroplast of the plant
cell. It is a green pigment. Chlorophyll absorbs sunlight that is essential for
photosynthesis.

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Sunlight
Sunlight provides energy to convert carbon dioxide and water into glucose. The
amount of sunlight required by plants varies according to plants. Some plants
need longer sunshine hours while others need shorter time or some shading.
Chlorophyll absorbs the sunlight for photosynthesis.

Carbon dioxide
Carbon dioxide is essential for photosynthesis. During photosynthesis, plants
take carbon dioxide from the atmosphere and release oxygen as a by-product.
But during respiration, plants take oxygen and release carbon dioxide. Carbon
dioxide released by living organisms is the source of raw material for
photosynthesis. Thus, plants maintain the balance of carbon dioxide and oxygen
in the atmosphere.

Water

Water is another important raw material for photosynthesis. Plants absorb water
and different kinds of minerals through their root hairs. They need more water in
hot and warm climates to make up for their loss of water they experience through
evaporation and transpiration.

Activity

Objective: To show that oxygen gas is produced during photosynthesis.

Requirement: Twigs of hydrilla, large test tube, beaker, glass funnel, water,
sodium bicarbonate, matchbox, etc.

Methods: Put twigs of hydrilla in a beaker and cover them inside an inverted
funnel. Fill the beaker with water and add a pinch of sodium bicarbonate as a
source of carbon dioxide. Fill the test tube with water and invert it gently over
the funnel stem as shown in the figure. Air should not enter inside the test tube
while inverting it over the stem of the funnel. Keep the apparatus in the sunlight
for a few hours.

Observation: After a few hours, gas bubbles are seen in the test tube. Gas starts
to displace the water downward in the test tube.

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Test of gas: After enough collection of the gas, lift up the test tube and insert a
burning matchstick inside the inverted test tube immediately. The matchstick
burns more vigorously inside the test tube than in the ordinary air.
Conclusion: This experiment shows that oxygen is produced during
photosynthesis.

Exercise

1. Write True for correct and False for incorrect statements.
a. Food is the source of energy.
b. Green plants convert solar energy into food energy.
c. Stomata are the green pigments found in the leaf.
d. Hydrochloric acid digests proteins in the food.
e. Glands are the group of specialized cells that secrete enzymes.

2. Fill in the blanks with correct words.
a. The green pigment found in the leaves of plants is called
…………….
b. Green plants use…… and…………… as the raw materials for
photosynthesis.
c. Starch when immersed in ………….. shows dark blue/ blue black
colour.

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d. The alimentary canal of human starts from ………… and ends at
………….

e. ………………. are the small projections at the wall of small intestine that
absorb digested food materials.

3. Select the best answer from the given alternatives.
a. Chlorophyll is able to trap……

i. carbon dioxide ii. oxygen iii. sunlight iv. water

b. ………….is the end product of photosynthesis.
i. glucose ii. carbon dioxide iii. water iv. protein

c. All green plants need…………. gas for photosynthesis.
i. carbon dioxide ii. oxygen iii. nitrogen iv. water

d. Saliva can digest…………… iv. all of them
i. protein ii. starch iii. fat

e. Gastric juice is found in……………..

i. mouth ii. stomach iii. small intestine iv. large intestine

4. Match the following:

Mouth absorbs water

Stomach bile juice

Liver pancreatic juice

Pancreas intestinal juice

Small Intestine hydrochloric acid

Large intestine salivary juice

5. Write your answer to the following questions in a word each.
a. In which part of the plant does photosynthesis occur?
b. Which gas is released as a result of photosynthesis?
c. Name that substance in which starch becomes dark blue in colour?
d. What is the secretion of salivary gland?

Oasis School Science and Technology -6 117

e. Which juice digests food protein and milk protein?
f. These are finger like projections in the wall of small intestine.
6. Write any two differences between:
a. Photosynthesis and digestion
b. Stomach and liver
c. Pancreatic juice and bile juice
7. Give reasons:
a. Green plants are called producers.
b. Animals are called consumers.
c. Photosynthesis does not occur during the night time.
d. Non-green plants cannot prepare food by themselves.
8. Identify the following figures and list one important function of each.

9. Define the following terms:
a. Life processes
b. Photosynthesis
c. Digestion

10. Answer the following questions.
a. Name the substances that are required for photosynthesis.
b. Describe photosynthesis in plants.
c. Name the organs of human digestive system.
d. List the function of the following:
gastric juice, hydrochloric acid, bile juice, pancreatic juice, intestinal
juice and villi
e. Briefly describe the digestion process in humans.
f. Draw a labelled diagram of the human alimentary canal.

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Unit Estimated Teaching Periods:

6 Force and Motion Theory Practical

82

Topics in Their Order according to CDC Curriculum

1. Definition of rest and motion
2. Transformation of force
3. Types of motion (linear and curvilinear)
4. Definition of force and its measurement
5. Effects of force (change in shape, size and motion)
6. Definition and examples of simple machines

Learning outcomes

At the end of this unit, students will be able to:
1. Define rest and motion.
2. Differentiate between linear and curvilinear motions.
3. Define force and learn to measure it with a spring balance.
4. Understand and demonstrate the effects of force.
5. Give simple examples of the transformation of force.
6. Define simple machines and give their examples from our daily life.

Learning outcomes

Force: Force is a factor which changes or tries to change the state of rest or state
of motion of an object.

Transformation of force: Application of force at one point of the tool to do
work at another place with the tool is called transformation of force.

Motion: A body is said to be in motion if it changes its position with respect to
the surrounding objects.

Oasis School Science and Technology -6 119

Rest: A body is said to be at rest if it does not change its position with respect
to the time and surrounding objects.

Reference: A reference point is a point which is used to determine if an object
is at rest or motion.

Linear motion: If an object travels in a straight line, it is called linear motion.

Curvilinear motion: The motion of an object other than the straight line is
called curvilinear motion.

Circular motion: The curvilinear motion of a body in a curved or a circular path
is called circular motion.

Rotatory motion: The type of curvilinear motion in which a body moves about
a fixed point or an axis without changing its position is called rotatory motion.

Oscillatory motion: The motion in which an object moves to and fro from the
mean position is called oscillatory motion.

Random motion: Random motion is a condition when an object continuously
changes its path.

Simple machines: The simple tools that make our work easier, faster and more
convenient are called simple machines.

Transformation of force: The process in which force applied at one point of
the machine is transferred and does work from another point of the machine is
called the transformation of force.

Compound machine: A machine formed by the combination of two or more
simple machines is called a compound machine.

6.1 Force and Motion

We perform a variety of actions all the while. Pulling, pushing, sliding, lifting,
loading, unloading, squeezing, stretching and twisting, for example, are some of
these actions. What do we need to make all these actions happen? That is a factor
we call force. Thus, the force is a factor which changes or tries to change the state
of an object at rest or in motion. Force can change the shape and size of a body. It
can change the speed and direction of a moving body. We also use force to cut,
split, stop, break or tie things.

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Fact file

A pulling force displaces or tries to displace an object towards the source of the
force. Similarly, a pushing force displaces or tries to displace an object away
from the source of force.

pulling water from the well pushing a car cutting apple

Reason to remember

What happens if two forces of equal amount are applied on a body from
opposite directions?

If two forces acting on an object are equal and opposite, the object will neither
be pulled nor pushed.The resulting force is called a balanced force.

Measurement of force

Different activities require different quantities of force. For example, pushing a
bicycle requires less force than pushing a car. The quantity of force is measured
by using a device called a spring balance. In SI system, the unit of force is newton
and in CGS system it is dyne. One newton of force is equal to 105 dyne.

Fig.: spring balance

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Reason to remember

Push and pull are called forces. Why?
Push and pull are forces because they can bring about a change in the state of
an object in motion or at rest.

Activity

Make a list of 5 daily activities that you do by using force.

Effects of force

In our daily life, we are aware of the effects of force. For example, we know that
a bullet can pierce through a metal sheet, a stone can break the glass into pieces
and a hammer can break a rock. We may have squeezed the wet clay into different
shapes. Do we not chew our food to break it into pieces? In the following section,
we will discuss some major effects of force:

Force can change the state of a body

In a football match, the striker kicks the ball setting it into motion but the
goalkeeper grabs the ball and brings it to rest. Similarly, pressing the pedal of the
bicycle makes it move while using the brakes stops it. Therefore, force can bring
a stationary object to motion. It can stop a moving object as well.

Reason to remember

Our push cannot bring a wall into motion, why?
Our push cannot bring a wall into motion because the force we are applying
against it is far less than the weight of the wall and its resistance.

Fig. striker kicking ball and goalkeeper stopping it

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Force can change the shape and size of a body

When force is applied on an area, it generates pressure. The pressure can deform
the object. For example, stretching a rubber band makes it thinner and longer; a
metal lump can be hammered into a thin sheet; a copper piece can be stretched
into a wire; hammering a glass can break it into pieces. So, force can change the
shape and size of an object.

hands stretching rubber hammer braking glass knife cutting vegetable

Fact file

Sir Isaac Newton was the first person to study gravity and force. Therefore, the
SI unit of force is called newton (N) to honor him.

Activity

Take a lump of clay. Apply force to change its shape into a cube, cuboid,
cylinder, triangle and circle.

Force can change the direction of a body

While playing cricket, a batsman changes the direction of the ball by hitting it
with the bat; a football player changes the direction of the moving football by
kicking or heading it; we can open or close a door by pulling or pushing its
handle, etc. So, force can change the direction of a moving body.

batsman hitting a ball football player kicking football

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Force can alter the speed of an object

Force can alter the speed of an object. For example, pushing the pedal of a bicycle
increases its speed, whereas pulling its brakes decreases the speed; we can make
a table tennis ball move faster by hitting it harder; if we push the ground harder
by our feet we can run faster.

Reason to remember

Why can the knife cut the vegetable?

The knife can cut the vegetable because the force applied on its handle goes
from our hand to its sharp edge creating a greater pressure where the edge
comes in contact with the vegetable.

Transformation of force

Activity

Observe different activities going on in our surroundings: cutting grass,
chopping the wood, digging the field, filling air in the bicycle, lifting water
from the well, flying kite, cycling, etc. In these activities, we use tools. Observe
these activities carefully - where do these tools work? Similarly, where do we
apply force on these tools?

chopping the wood digging the field lifting water from the well flying kite

We apply force on tools and machines to do our work with ease and efficiency.
For example, we use a spade for digging the field; we use the wheel and axle
(lattai) for flying kite; we use an axe for chopping the wood; we use a sickle for
cutting grass; we use a knife for cutting vegetables, etc. We can see that the force
is applied on a certain part of the tool before it is transferred to another part to get
our work done. For example, we apply force on the handle of the axe and the axe
chops the wood at another end; we apply force on the knife and the knife cuts the
vegetables, etc. All kinds of simple machines such as the axe, spade, spoon,
broom, sickle, crowbar, wheel and barrow transform force from one place to

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another. Therefore, the application of force at one point of the tool to do work at
another point with the tool is called the transformation of force.

cutting vegetable with a knife cutting wire with pliers beating rice with a dhiki

6.2 Rest and Motion

The earth revolves around the sun. Animals move from one place to another for
food, safety and shelter. Rivers flow towards oceans. Air blows from colder to
warmer places. All these things change their locations with respect to time. They
are called moving bodies. Thus, a body is said to be in motion if it changes its
position with respect to the surrounding objects. But, mountains, trees, buildings,
etc. are at rest. They never change their place with respect to time and surroundings.
They are called bodies at rest. Thus, a body is said to be at rest if it does not
change its position with respect to time and surrounding objects.

moving car running boy

Fact file Oasis School Science and Technology -6 125

Motion is the effect of force.

Reference point

A reference point is a point which is used to determine if an object is at rest or
in motion. For example, let’s say your bench is a reference point. After a few
seconds if you are changing your place with respect to that bench, you are in
motion, otherwise you are at rest. Similarly, if the land is taken as a reference
point, the buildings, mountains, trees, bridges, football grounds and electric
poles never change their place with respect to the land. Therefore, these objects
are at rest in reference to that land.

bridge building a man at rest

Reason to remember

Rest and motion are relative terms. Why?

Rest and motion are relative terms because an object can be at rest and motion
at the same time depending on the reference point. For example, a passenger
sitting on a moving bus.

However, flying birds, walking people, running animals, falling leaves, rainfall,
moving vehicles, etc. are changing their place with respect to the land. Therefore,
these objects are in motion.

Fig.: a person sitting in a running car

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Reason to remember

If you are sitting on a chair, are you at rest or in motion? But what if that chair
is in a moving van?
Of course, we are at rest with respect to the chair. If that chair is in a moving
van, we are in motion with respect to the surrounding areas. It means we are at
rest and in motion at the same time depending on our reference point. Therefore,
rest and motion are relative terms.

Activity

The motion of an object with respect to another object is called a relative motion.
If you and your friend are walking at the same speed, will you be at rest or in
motion relative to your friend? Discuss.

Types of motion

Objects in motion change their place with respect to the surrounding objects.
They move in various patterns of motion. For example, the river flows randomly
towards the lower elevations, wheels rotate on their axis, people move freely in
different directions, etc. But, the bullet travels in a straight line, raindrops fall in
straight lines, etc. These motions can be classified into two groups: linear and
curvilinear.

Linear motion

What would you do if you take part in a 100 m race? You would probably run as
fast as you can in a straight line. Similarly, a drop of rain falls in a straight line,
light travels in a straight line, a bullet fired from a gun also travels in a straight
line, etc. Thus, if an object travels in a straight line, it is called a linear motion.

Fig.: ray of light, child sliding down in a slide, fired a bullet

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Fact file

The object in a linear motion will continue to be in the same motion unless an
external force is applied on it.

Curvilinear motion

Have you ever seen a flying bee? Does it move in a straight line? No, it does not.
It usually flies randomly in a curved path. The wheel of a bicycle moves in a
circle. The road we travel and the streets we walk on have many turnings. We
hardly move in a straight line. Thus, the motion of an object on paths other than
the straight line is called a curvilinear motion. Some examples of curvilinear
motion are the circular motion, rotatory motion, oscillatory motion, random
motion, etc.

Fig.: curvilinear motion

SN Linear motion SN Curvilinear motion

1 If an object travels in a straight 1 The motion of an object other than

line, its motion is called a in a straight line is called a

linear motion. curvilinear motion.

2 An object in linear motion 2 An object in a curvilinear motion

does not change its direction. continuously changes its direction.

Example: a falling raindrop Example: spinning of the earth on
its axis

Circular motion

Have you seen people riding the Ferris wheel? They move continuously but their
distance from the centre of the wheel does not change. It means they are moving
in a circle. The curvilinear motion of a body in a curved or a circular path is called

128 Oasis School Science and Technology -6

a circular motion. A circular motion is observed when vehicles travel through
curved roads; planets revolve around the sun, etc.

Fig.: circular motion

Rotatory motion

The type of curvilinear motion in which a body moves about a fixed point or an
axis without changing its position is called a rotatory motion. The spinning of a
blender machine, a drill machine, the engine of vehicles, potter’s wheel, etc. are
examples of a rotatory motion.

rotating fan rotating wheel of a bicycle spinning top

Reason to remember

Why is the earth in a rotatory motion?
The earth is in a rotatory motion because it spins around its axis.

Oscillatory motion

An oscillatory motion is characterised by a to-and-fro motion. Observe a person
swinging in a swing. The person will swing forward in a curve, reaches the
maximum possible height (to) and swings backwards in a curve (fro) repeatedly.
This kind of motion is called an oscillatory motion. The motion in which an object
moves up and down from the mean position along an arc is called an oscillatory
motion. The vibration of the vocal cord, string of a guitar, pendulum, etc. are
examples of an oscillatory motion.

Oasis School Science and Technology -6 129

a kid playing swing oscillating pendulum

Random motion

In the late autumn, dried yellow leaves fall from trees. They take a random path
down. Children playing chase and catch run randomly. Dust flies in a storm
without any particular direction. A random motion is a condition when an object
continuously changes its path. Random motions are more common in nature.

a flying bird people moving on the road

Activity

Observe objects in motion while you are at school. Make their list and note the
type of motion for each of these objects.

6.3 Introduction to the Simple Machine

We need various simple tools in our daily life: a spoon, broom, nail cutter, beam
balance, etc. They have simple and convenient structures to ease our work. These
tools are simple machines. Thus, the simple tools that make our work easier,
faster and more convenient are called simple machines. Similarly, some machines
such as we see in a motor cycle, car, bus and train have complex structures.
Depending on their structures, machines are divided into two groups: simple
and complex.

130 Oasis School Science and Technology -6

scissor spoon pan balance wheel barrow

Fact file

There are six basic types of simple machines. These are lever, pulley, wheel and
axle, inclined plane, wedge and screw.

Reason to remember

1. Why is a knife a simple machine?

A knife has a very simple structure, with a sharp edge on one side and a
blunt edge on the other. When we apply force on its handle, the sharp edge
cuts the vegetable, for example, with ease and convenience. So, it is a simple
machine.

2. Why is it easier to do work by using simple machines?

It is easier to do work by using simple machines because they can transfer
and multiply force or increase the rate of doing work.

Use of simple machines

A simple machine is a useful tool. It reduces effort and time. It enhances the
efficiency of a person to do work. For example, a nail cutter helps us cut nails, the
chisel helps us make a borehole on wood, windlass holds the windowpane, a
ladder helps us go up a building, etc. Simple machines are used to make work
easier, faster and more convenient for us.

Some simple machines and their uses

S.N. Simple machine Uses

1. Scissors Cut clothes, paper, etc.

2. Crowbar Lift a heavy load, such as a stone.

3. Knife Cut vegetables, fruits, etc.

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4. Bottle opener Open the lid of, say, a coca-cola bottle.
5. Wheelbarrow Carry loads, for example, stones and bricks.

Fact file

The wedge is the oldest type of simple machine. It was a hand axe made of
stone.

Differences between simple and complex machines

S.N. Simple machine S.N. Complex machine

1. A simple machine is a simple 1. A complex machine is the
tool which makes our work combination of many simple
easier, faster and more machines.
convenient.

A simple machine has a very A complex machine has a complex

2. simple body structure and is 2. structure and may be difficult to

easy to operate. operate without training.

Activity

Observe a sewing machine. Is it a simple machine or a complex one? Discuss
this in the classroom.

Effects of simple machines

Simple machines make our work easier, faster and more convenient in the
following ways:

A simple machine can transfer the force

A spoon held at one end lifts food from another end. Similarly, when the scissors
are pressed on one end, the paper is cut from another end. Why is work done by
another part of the simple machine when we use the force somewhere else? This
is because simple machines can transfer force from one point to another. The
process in which a force applied at one point of a machine is transferred to do
work from another point is called the transformation of force.

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Transformation of force helps us do several types of work. For example, we use
an axe for chopping the wood; we use a spade for digging the field; we use a
pump for filling air in the bicycle; we use pulleys for lifting water from the well;
we use a sickle for cutting grass; we use the wheel and axle (lattai) for flying kites;
we use a knife for cutting vegetables, etc.

scissors cutting paper chopping the wood digging the field

Fact file

Human beings of stone age used stone tools as a simple machine to break nuts
and for hunting purposes.

A simple machine can multiply force

A simple machine with longer handles usually multiplies the force. For example,
the nail cutter has a long handle, so it is easy for us to trim our nails with it. Have
you ever seen a metal cutter? It looks like scissors. Its cutting side is very short
but handles are very long. Longer handles help the force applied to magnify and
cut metals easily. Have you noticed that it is easy to climb up to the next floor in
a long ladder with a gentle slant? It is because longer ladders magnify the force.

a person climbing ladder winding road in hills

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Reason to remember

Why is it easier to walk on a slanted plank while loading a truck?

It is easier to walk on a slanted plank while loading a truck because a longer
and gentler slant multiplies the force we need to move the load. So it feels easy
to climb on the truck.

Activity

Try cutting a cucumber with your bare hands. Now use a knife to cut the
cucumber. What difference do you observe? Was it easier to chop the cucumber
with a knife? Discuss the reason behind this.

A simple machine can change the direction of force

A sea-saw is a fun plank. Children usually play on it. When a child sitting on one
of its ends pushes the seesaw downward, the child sitting at another end is lifted.
What is happening here? This simple machine is changing the direction of the
force that the first child applies on the seesaw. Similarly, you might have seen a
pulley in a well. It is a circular disc with a groove where the rope can move.
When the rope is pulled downward, the bucket at another end of the rope is
pulled upward.

single pulley taking out water from the well

Reason to remember

Why do people use a single fixed pulley in the well?

People use a single fixed pulley in the well because it helps them change the
direction of the force, lifting water up from the well, while they are pulling the
rope down with ease on their side.

134 Oasis School Science and Technology -6

A simple machine can increase the rate of doing work

Riding a bicycle is faster than walking. Using a sickle helps to cut grass faster. A
lemon squeezer squeezes the lemon faster than the bare hands do. Therefore, the
use of simple machines increases the rate of doing work.

Fig.: wheelbarrow carrying a load

Reason to remember

Why is a wheelbarrow used to carry loads?
The wheelbarrow is used to carry loads because it helps the work get done
faster and with ease.

Simple machines make work convenient
A simple machine helps us use force at an exact point. For example, you can use
a hammer and nail to fix woods at the required part, using a spoon to eat hot
soup is convenient, forceps can be used to pluck hair that you find very hard to
do with fingers, needles can pass through clothes without damaging them, etc.

forceps picking hot burning charcoal a woman using needle sewing cloth

Oasis School Science and Technology -6 135

Fact file

The idea of a simple machine originated with the Greek philosopher Archimedes
around 3 BC.

Activity

Forceps neither make work easier nor faster. They are used as if they were a
simple machine. What might be the reason for this? Discuss this in the classroom.

Compound machines

Let’s look at a bicycle. Is it a simple machine or a combination of simple machines?
A bicycle has a relatively more complex body structure than a knife or scissors. It
is a combination of simple machines. Therefore, a bicycle is a compound machine.
A machine formed by the combination of two or more simple machines is called
a compound machine. A compound machine has a complex structure and design.
It may or may not need fuel to operate. Compound machines are also called
complex machines.

bike cranes bicycle sewing machine

Fact file

The inclined plane was not included in the simple machine in the beginning.

Reason to remember

A sewing machine is called a complex machine. Why?

A sewing machine is a complex machine because it is made by the combination
of many simple machines and has a complex body structure.

136 Oasis School Science and Technology -6

Use of compound machines

Compound machines have a wide range of applications. For example, bicycles,
motorcycles, buses, trucks, etc. are some means of transportation. Blenders,
grinders, fans, water pumps, etc. are used in households. Cranes, trucks, dozers,
etc. are used in construction.

blender fan grinder water pump

Summary

1. Force is a factor which changes or tries to change the state of rest or state of motion
of an object.

2. In SI system, the unit of force is newton and in CGS system the unit of force is dyne.
One newton of force is equal to 105 dyne.

3. Application of force at one point of the tool to do work from another point of the tool
is called transformation of force.

4. A body is said to be in motion if it changes its position with respect to the surrounding
objects.

5. A body is said to be at rest if it does not change its position with respect to the time
and surrounding objects.

6. A reference point is a point which is used to determine if an object is at rest or in
motion.

7. If an object travels in a straight line, it is said to be in a linear motion.

8. The motion of an object in curved paths, not a straight line, is called a curvilinear
motion.

9. The simple tools that make our work easier, faster and more convenient are called
simple machines.

10. A machine formed by the combination of two or more simple machines is called a
compound machine.

Oasis School Science and Technology -6 137

Exercise

1. Fill in the blanks with appropriate words.
a. In CGS system the unit of force is …………..

b. In ………, a body does not change its position with respect to the
reference point.

c. Rest and motion are……………………terms.

d. ………… motion is characterized by to and fro motion.

e. A machine made from two or more simple machines is…………

2. Write True for the correct and False for the incorrect statements.
a. Force brings a moving body to rest and body at rest to motion.
b. Rest and motion are relative terms.
c. One dyne of force equals 105 newton.
d. In a linear motion an object moves on a straight path.
e. A simple machine is formed from many compound machines.

3. Select the best answer from the given alternatives.

a. Which of the following is the SI unit of force?

i. erg ii. dyne

iii. newton iv. joule

b. What can a force do to an object?

i. change the direction ii. change the shape and size

ii. change its speed iv. all of them

c. Which one of the following is an example of rest?

i. river ii. flying aeroplane

iii. tree in the forest iv. all of the above

d. Which one is an example of a circular motion?

i. Ferris wheel iii. the person sitting in a seat of Ferris wheel

iii. falling rain drop iv. none of them

138 Oasis School Science and Technology -6

e. Which one of the following can be done by a simple machine?

i. transfer the force ii. magnify the force

iii.change the direction of force iv. all of them

4. Match the following: i. oscillatory motion
CGS unit of force

Flying bird ii. scissors

The pendulum of a clock ` iii. truck

Simple machine iv. random motion

Compound machine v. dyne

5. Write your answer to the following questions in a word each.

a. Which device helps us measure the amount of force?

b. What is the term for an object used to observe the state of rest or motion?

c. What type of motion is the spinning of a top?

d. Give an example of a simple machine.

e. What type of machine needs fuel?

6. Write any two differences between:
a. Linear motion and curvilinear motion
b. Simple machine and compound machine

7. Give reasons:
a. Push and pull are called forces.

b. Rest and motion are relative terms.
c. Falling raindrop is in a linear motion.
d. Scissors are called a simple machine.
e. A bicycle is considered a compound machine.

8. Observe the given diagram and write their uses.

Oasis School Science and Technology -6 139

9. Answer the following questions:
a. Define force. Write its SI and CGS units.
b. List the effects of force.
c. Define rest and motion with an example of each.
d. What is a reference point?
e. What are linear and curvilinear motions? Write with examples.
f. Define rotatory motion and random motion with examples.
g. Define simple machines with four examples.
h. List the effects of simple machines.

10. Project Work
Make a list of machines used in your house and classify them as simple and
complex machines.
11. Glossary:
gravity : force by which earth pulls an object from its surface to its

centre.
pressure : force acting perpendicularly on the area
axis : imaginary straight line in which an object spins
vocal cord : sound-producing organ

140 Oasis School Science and Technology -6

7Unit Energy in Our Estimated Teaching Periods:
Daily Life
Theory Practical
16 4

7.1 Energy 7.2 Heat

7.3 Light 7.4 Sound

7.1 Energy

Topics in Their Order according to CDC Curriculum

1. Definition of potential energy and examples
2. Factors affecting potential energy
3. Definition of kinetic energy and examples
4. Relationship of kinetic energy with mass and velocity
5. Examples of energy transformation

Learning outcomes

At the end of this unit, students will be able to:
1. Define potential energy and provide examples.
2. Define kinetic energy and provide examples.
3. Demonstrate kinetic energy is greater for an object with a higher mass and

velocity.
4. Provide examples of transformation of potential energy into kinetic energy.

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Key terms of the unit

Energy: Energy is an ability to do work.

Mechanical energy: The energy of an object due to its motion or position is
called mechanical energy.

Potential energy: The energy present in a body due to its position or deformation
is called potential energy.

Kinetic energy: The energy present in an object due to its motion is called
kinetic energy.

Energy transformation: The process of change of energy from one form to
another is called energy transformation.

Law of conservation of energy: Energy can neither be created nor be destroyed,
but it can be transformed from one form to another one.

We eat food to live. Food gives us energy. We use energy to carry out activities
such as speaking, walking, reading and writing. Plants make food by
photosynthesis and consume it for their growth and development. Petroleum
provides energy for vehicles and machines to operate. Electricity is required to
operate radio, television, computers, fans and other gadgets. Thus, energy is the
ability to do work.

Units of energy

The SI unit of energy is joule (J) and its CGS unit is erg.

Reason to remember

Why do living things eat food?

Living things eat food because food is the source of energy. All organisms use
food to produce energy.

Forms of energy

We use fire to cook food and boil water. We use light so we see. Foods contain
chemical energy that is used by our body. Moving objects have the kinetic energy.
Water stored in a dam has the potential energy. We use cells in a torchlight to
produce light. Thus, energy exists in various forms: mechanical energy, heat

142 Oasis School Science and Technology -6