PRO J ECTWORK
1. Collect some objects in your surroundings. Identify which of them are made
of metals and which of them are made of non-metals.
2. Make a list of items used in kitchen that are made metals and alloys.
Exercises
1. Fill in the blanks.
a. Metals are hard.....................and ductile.
b. There are.....................elements known.
c. Non - metals like.....................is a good conductor of heat and electricity.
d. Silicon and germanium are called......................
e. Brass and.....................are alloys.
2. Write true or false for the following statements.
a. There are 118 metals.
b. Iodine and sulphur are non-metals.
c. Alloys are used to make pots.
d. Brass is made from iron and gold.
e. Copper is called coinage metal.
3. Match the following.
Bronze coinage metal
Cooper metalloid
Sulphur jewellery
Silicon Alloy
Gold non-metal
4. Answer the following questions.
a. Define metal and non-metals with examples.
b. Write properties of metals.
c. What is sulphur? Write it uses.
d. What are metalloids? Give 3 examples.
Blooming Science & Environment Book 7 151
e. Write properties of metalloids.
f. What is iodine? Write its uses.
g. What are alloys? Give examples.
h. Brass is called an alloy. Explain.
i. What is Bronze? Write its uses.
j. What is catalyst?
k. Distinguish between metals and non-metals.
l. Write 2/2 uses of sulphur, iodine, brass and bronze. ‘
m. Write the historical importance of bronze.
Glossary
Metal : hard, shining materials which conduct electricity and produces deep
sound
Non-metals : dull, brittle material which is bad conductor
Metalloid : the substance which shows the properties of both metal and non-
metal.
Malleable : property to change into thin plates.
Ductile : property to change into thin wires.
Sonorous : giving deep sound
Lusture : quantity of being bright/shining property
Conduct : to carry from one place to another.
152 Blooming Science & Environment Book 7
14Chapter Some Useful Chemicals
Learning Outcomes
On the completion of this unit, students will be able to: Estimated Periods: 5+1
• introduce some chemicals loke phenol, dettol, detergent, baking power and
chemical fertilizers.
• describe the utility of above mentioned chemicals.
Phenol
Phenol is an organic compound with chemical formula C6H5OH. It is also
known as Benzenol, phenylic acid, carbolic acid or phenic acid. Phenol is
white crystalline solid. The molecule consists of a phenyl (C6H5) bonded to
a hydroxyl (-OH) group.
Phenol was first discovered in 1834, when it was extracted from coal
tar. The antiseptic properties of phenol were used by Sir Joseph Lister
(1827-1912). During Second World War injection of phenol was used as a means of
execution, by the Nazis. It is extracted from processing of petroleum product. It is
appreciably soluble in water.
Uses:
1. Phenol is used to disinfect around home to destroy housefly and other harmful
germs.
2. It is used to manufacture fibres, paints plastics, etc in industries.
3. Phenol is also used in drugs like aspiring herbicides and pharmaceuticals.
4. Phenol is used as oral anesthetic/analgesic commonly used to treat
pharyngitis.
5. Phenol is widely used as antiseptic especially as carbolic soap in hospitals and at
homes.
6. Phenol derivatives are also used in the preparation of cosmetics including
sunscreens, hair dyes and skin lightening preparations.
Cautions
1. Phenol and its vapours are corrosive to the eye, the skin and the respiratory tract.
Repeated or prolonged skin contact with phenol may cause dermatitis or even
second and third degree burns due to phenol’s caustic and defatting
properties.
2. Inhalation of phenol may cause lung edema. The substance may cause harmful
effects on the central nervous system and heart, resulting in dysrhythmia, seizures
and coma. The kidneys may be affected as well. Exposure may result in
death.
Blooming Science & Environment Book 7 153
Dettol
Dettol is a trade name for a series of liquid and solid antiseptic cleansing products. It
was first made by Reckitt Benckiser and Colman. It was discovered by Joseph Lister
in 1860.
Dettol is one of the chemical which we instantly recognize by its
distinctive smell. It is an aromatic compound derived from phenol. It
is commercially available as an inexpensive liquid antiseptic which
is safe and gentle enough to use on the skin and yet powerful enough
to use as disinfection. As several of the ingredients are insoluble in
water, dettol produces a white emulsion of oil droplets when diluted during use.
Properties
1. Dettol forms cream coloured crystal.
2. Melting point of Dettol crystal is 114oC to 116oC.
3. Dettol is active at pH 4 to 9.
4. It is slightly soluble in water and has good solubility in alcohols and pine oils.
5. It can kill pathogenic germs and fungi because of which it is a good cleansing
agent.
Uses
1. Dettol liquid antiseptic/disinfectant is used for first aid and for medical and
personal hygiene.
2. Powder form of Dettol is used in athlete’s foot.
3. Dettol can be used to clean out wound cut, etc.
4. It is also used to treat acne, which is caused by bacterial infections.
Allergic Reactions of Dettol
1. A rash or hives with swelling on the face, mouth throat or tongue.
2. There may be tightness of the chest and difficulty in breathing.
3. Redness, burning blisters and peeling of the skin.
Cautions
1. It can have lethal toxicity.
2. It is poisonous when ingested.
3. Inhalation may lead to death.
154 Blooming Science & Environment Book 7
Baking Poder
Baking powder is a dry chemical leavening agent used to
increase the volume and lighten the texture of baked goods
such as muffins, cakes, and biscuits. Baking powder works by
releasing carbon dioxide gas into a batter or dough through
an acid-base reaction causing bubbles in the wet mixture to
expand and thus leavening the mixture. It is used instead of
yeast for end-products where fermentation flavors would be undesirable or where the
batter lacks the elastic structure to hold gas bubbles for more than a few minutes.
Because carbon dioxide is released at a faster rate through the acid-base made by
chemical leavening are called quick breads.
Most commercially available baking powder is sodium bicarbonate (NaHCO3), also
known as baking soda, one or more acid salts and an inert starch.
Uses
Generally one teaspoon (5ml) of baking powder is used to raise a mixture of one
cup (200-250ml) of flour, one cup of liquid and one egg. It is widely used to make
bread and other beverages. Baking powder can also be used in making 'selroti' and to
neutralize the hyper acidity in stomach.
Fertilizers
Plantation of crops for a long time decreases the supply of
minerals in soil and the fertility of soil decreases. Therefore,
minerals must be added to soil as required by plants.
Substances used to increase the fertility of soil are called
fertilizers. Fertilizers are of two types : organic fertilizer and chemical fertilizer.
Organic fertilizers
Fertilizers made from the decay of animals and plants or the waste products of animals
are called organic fertilizers.
Compost manure is an organic fertilizer. It is prepared by making layers of plant, hay,
dung etc. in a pit. Sometimes, limestone is also used. This is left to decay for some
months. After decay, it is used as fertilizer.
Chemical Fertilizers
Fertilizers made by mixing the chemicals are called chemical fertilizers. Mostly,
nitrogen (N), Phosphorous (P) and potassium (K) compounds are used for making this
type of fertilizers.
1. Nitrogenous Fertilizers
Annomium nitrate - NH4NO3
Urea - CO(NH2)2
Ammonium sulphate (NH4)2SO4
Blooming Science & Environment Book 7 155
2. Phosphourous fertilizers
Ammonium phosphate - (NH4)3PO4
Super phosphate - Ca(H2PO4)2.2CaSO4
Triple superphosphate - 3Ca(H2PO4)2
Phosphrous can also be made from bone meal.
3. Potassium fertilizers
Potassium Chloride - KCl
Potassium nitrate - KNO3
Potassium sulphate - K2SO4
Little amount of potassium can be obtained from ash also.
Significance of Nitrogen (N), Phosphorous (P) and Potassium (K) in Fertilizers
Nitrogen is the source of protein. It helps to grow and to increase the greenary of
plants. Protein is required for the growth of plants, and phosphorus is required for the
growth of their roots. Phosphorus helps ripen the fruits and develop the seeds of crops.
Phosphorus is also important in the synthesis of protein, cell division and growth of
leaves and buds.
Potassium mainly helps in preparing food for the plants. Absence of potassium hinders
protein synthesis and cell division. In its absence, leaves and buds wither and immunity
is decreased. Fertilizers made by including all these elements are called NPK fertilizers.
Detergents
Synthetic petrochemical obtained from hydrocarbon which is more
soluble than soap is called detergent. Sodium lauryl sulphate, alkyl
benzensulphonate, sodium pyrophosphate etc. are detergents. Mostly,
detergent is used in washing clothes. It is more soluble and useful than
soap. Perfume is added to soap and detergent to make them popular.
Detergents are also called soapless soap.
Main Points to Remember
1. Phenol is also called carbolic acid is an organic compound with chemical formula
C6H5OH. It is used in anesthetic agent to clean floor and toilet.
2. Dettol is an antiseptic cleansing product and used in cut, wounds and to clean
infected areas.
3. Baking powder is a dry chemical in the form of powder which is used for baking
goods in cakes, muffing and biscuits.
156 Blooming Science & Environment Book 7
4. Fertilizer made from the decay of animals and plants or the waste products of
animals are called organic fertilizers.
5. Fertilizer made by mixing the chemicals are called chemical fertilizers. Nitrogen,
phosphorus and potassium compounds are used for making this type of fertilizer.
6. Synthetic petro chemicals obtained from hydrocarbon which is more soluble
than soap is called detergent.
PRO J ECTWORK
Visit a paddy field nearby you and ask the farmer about the types of fertilizers used in
the field. Also discuss advantages and disadvantages of both chemical and organic
fertilizers.
Exercises
1 . Fill in the blanks.
a. ...................... is used in bathroom for cleansing purpose.
b. Dettol is used in cuts and wound as a......................
c. ......................is used for baking foods.
d. Bone contains......................mineral.
e. Animal waste is rich in......................matter.
2. Match the following.
Urea organic fertilizer
Ash Anesthetic purpose
Dettol Cleansing agent
Phenol Nitrogen
Humus Potash
3. Write true or false for the following.
a. Dettol kills germs and keeps us safe.
b. Nitrogen helps to ripe the fruits.
c. Breads are baked by baking powder.
d. Potassium chloride is a source of phosphorus.
e. Detergents and petrochemical obtained from hydrocarbon.
Blooming Science & Environment Book 7 157
4. Answer the following questions.
a. What is phenol? Write its uses.
b. Write in short about Dettol.
c. What is baking powder? Write its molecular formula.
d. Detergents are called soapless soap, explain.
e. What are called organic fertilizers?
f. Define NPK fertilizers.
g. Write one one function of nitrogen, phosphorus and potassium for plants.
h. Name 2/2 compounds from which plants get NPK fertilizer.
i. Organic fertilizers are better than chemical fertilizers, explain.
5. Write the name of 3/3 compounds which give nitrogen, phosphorus and
potassium
Glossary
Alkenes : unsaturated hydrocarbons with a double bond between carbon
atoms
Polymer : a long chained molecule formed by merging together of simple
molecules
Monomer : a unit that combines with similar units to form a polymer
Polymerisation : act of forming polymer from monomers
Crude oil : oily liquid mined from petroleum mines
Synthetic : made by the union of simpler substances
Regenerate : to make again
Supercooled (liquid) : a solid whose molecules are arranged as in a liquid in a molten
state.
Absorbant : a substance that soaks in liquid
Emulsion : a milky liquid with suspended oil droplets
158 Blooming Science & Environment Book 7
15Chapter Living Beings
Learning Outcomes
On the completion of this unit, students will be able to: Estimated Period-12+2
• to classify vertebrates with their characteristics.
• describe life cycle of frog with diagrams.
• classify flowering and non-flowering plants.
• describe the structure and functions of different parts of flowering plants
with diagrams.
A. Vertebrates
Introduction
There are two types of animals in nature. Animals without backbone in their body
called invertebrates and animals with backbone in thier body called vertebrates.
We have seen different kinds of animals on the earth. Some live on water such as
whale, fish and octopus whereas some live on land like tiger, peacock, human etc.
Some animals live on land as well as in water. Birds have adaptation so as to fly.
Animals like roundworm, cockroach and octopus do not have vertebral column while
fishes, birds, whale and human have vertebral column.
Animal kingdom is chiefly divided into two sub-kingdoms on the basis of vertebral
column:
a. Invertebrates b. Vertebrates
Classification of Animal Kingdom
Animal Kingdom
Invertebrates Vertebrates
Pisces
Protozoa Amphibia
Porifera Reptilia
Coelenterata Aves
Platyhelminthes Mammalia
Ascheminthes
Annelida Blooming Science & Environment Book 7 159
Arthropoda
Mollusca
Echinodermata
Invertebrates
Animals that do not have vertebral column or backbone are called invertebrates.
Earthworm, mosquito, butterfly etc are invertebrate animals. These animals are also
known as lower animals.
Vertebrates
Animals having vertebral column or backbone are called vertebrates. The vertebrate
animals have certain general characteristics.
Cold Blooded and Warm Blooded Vertebrates
According to the maintenance of body temperature vertebrates can be classified into
two groups.
a. Cold Blooded Animals
Animals whose body temperature change according to the surrounding temperature
are called cold-blooded animals. They are also known as poikilothermic animals. The
body temperature of these animals frequently fluctuates in line with environmental
temperature. Cold-blooded animals are unable to regulate their body temperature
metabolically. The three classes of vertebrates, i.e., Pisces, amphibian and reptilian
are cold-blooded vertebrates. All the invertebrates are also the cold blooded animals.
In winter season, you cannot see frogs, snakes, lizard etc. because they hide themselves
to protect from coldness. This hiding is called hibernation. In extreme hot season,
they also hide themselves to protect from the harmful effect of extreme heat. This
hiding behaviors of animals into the soil in order to protect them from hotness is called
summer aestivation.
Vertebrates
Cold Blooded Warm Blooded
Pisces Amphibia Reptilia Aves Mammalia
b. Warm Blooded Animals
Animals that maintain constant body temperature irrespective of the environmental
temperature are called warm-blooded vertebrates. As the temperature of the body
remains the same, they are sometimes called homoeothermic animals. The body
temperature of warm-blooded vertebrates is usually 35-44oC. Aves and mammalian
are warm-blooded vertebrates.
160 Blooming Science & Environment Book 7
Diffenreces between Poikilothermic and Homoeothermic animals
Poiliothermic Animals Homoeothermic Animals
They can change their body temperature. They cannot change their body
temperature.
They may be aquatic or terrestrial. They may be aerial or terrestrial.
Most of them have gills for respiration. They have lungs for their respiration.
Skin is either naked or covered with Skin is covered with either hair or
water-proof scales. e.g. fish, frog, snake, feathers. e.g., birds, cow, man, etc.
etc.
Classification of Vertebrates
There are different types of vertebrate animals found in nature. The sub-kingdom
vertebrates is further divided into five different classes. They are :
a) Pisces Scan for practical experiment
b) Amphibians
c) Reptiles
d) Aves
e) Mammals
Class 1: Pisces visit: csp.codes/c07e23
The animals in this group are well adapted to live in water. All fishes belong to this
group. The chief characteristics of pisces are as follows:
a. They are aquatic cold-blooded animals.
b. Respiration take place through gills.
c. Locomotion is accompanied by paired as well as unpaired fins.
d. Heart is two chambered; one auricle and one ventricle.
Fish Seahorse Eel
Blooming Science & Environment Book 7 161
e. Body is covered with scales.
f. Body is streamlined or boat shaped.
g. There is no external ear.
h. Eggs are produced. Generally fertilization.
Examples: Labeo (Rohu), Torpedo (Electric ray), Hippocampus (Sea-horse), Scolidon
(Dog-fish), Myxine (Hagfish) and Sharks, etc.
Class 2: Amphibians
They are the first vertebrates to occupy the land. The word amphibian in Greek means
dual life (Amphi = dual; bios = life). These animals have adaptation to live in water
as well as on land. Amphibian larvae are aquatic, having gills for respiration; they
undergo metamorphosis to the adult form. Metamorphosis is the rapid transformation
from the larval to the adult form.
The chief characteristics of amphibian are as follows:
1. They live in water as well as on land and are cold blooded.
2. The soft, moist, scale-less skin is used for gaseous exchange to supplement lungs.
3. Body is divided into head and trunk.
4. The heart is three-chambered with two auricles and one ventricle.
5. There is no external ear.
6. They undergo metamorphosis from larva to adult in their life cycle.
7. Fertilization is usually external. They lay eggs in water. Reproduction commonly
occurs in water.
8. Larvae of amphibians are aquatic, having gills for respiration.
9. Frog shows hibernation and aestivation.
Examples are Rana (frog), Bufo (toad), Hyla and Salamander, etc.
Salamander Frog Toad
162 Blooming Science & Environment Book 7
Class 3: Reptilies
The animals in this group are the first terrestrial vertebrates, which can live in dry
terrestrial habitats. The chief characteristics of reptilian are:
1. They posses dry scale skin with horny scales. The skin prevents water loss from
the body surface.
2. They are most terrestrial, some are aquatic.
3. They are cold-blooded and have elongated or cylindrical body.
4. Body of most reptiles is divisible into head, neck, trunk and tail.
5. They breathe atmospheric oxygen by means of lungs.
6. They have three-chambered heart except in crocodile which have four chambered
heart.
7. Fertilization is internal and the majority of reptiles lay eggs on land.
Examples: lizards, snakes, crocodiles, turtles, tortoises etc.
Snake Lizard Crocodile
Class 4: Aves
The birds have feather, wings and a beak. Aves are bipedal vertebrates that evolved
from reptilian ancestors. Modern birds have scaly legs, like reptiles . The chief
characteristics of aves are as follows:
1. They are warm-blooded having streamlined body.
2. Body is divisible into head, neck, trunk and tail.
3. Body is covered with feathers, legs have scales.
4. Fore limbs are modified into wings for flying. Hind limbs are used for walking,
perching etc.
5. There is no external ear.
6. Bones are light, porous with air cavities to reduce the body weight.
7. The heart is four chambered.
8. Fertilization is internal. They lay eggs. Their eggs having large yolk are covered
with calcareous shells.
Examples: Columba (pigeon), Aquila (eagle), Sparrow, Parrot, Crow etc.
Blooming Science & Environment Book 7 163
Pigeon Peacock Sparrow
Class 5: Mammals
There are around 4500 species of mammals on the earth. They are highly developed
warm-blooded animals. All mammals have mammary gland, which secrete milk to
nourish the young ones. The chief characteristics of mammals are listed below.
1. Skin bears hair. They are warm blooded.
2. Body is divisible into head, neck, trunk and tail, There is no tail in some mammals.
3. The senses of sight, smell and hearing are well developed.
4. External ear called pinna is present.
5. Heart is four chambered having two auricles and two ventricles.
6. Respiration takes place by lungs.
7. Mother has mammary glands, which produced milk for the newly born youngones.
8. Feet with five toes are adapted for walking, running, flying, burrowing, swimming
and climbing.
9. Fertilization is internal. They give birth to young ones, except the spiny anteater
and platypus.
Examples: Human, rabbit, bat, tiger, lion, dolphin, whale etc.
Bat Whale Cow
Main Points to Remember
1. There are two groups of animals; invertebrates and vertebrates
2. Fishes, amphibians, reptiles, birds and mammals are vertebrate animals.
3. Invertebrates do not have backbone whereas vertebrates have.
164 Blooming Science & Environment Book 7
4. According to the temperature control, vertebrates are divided into two groups
cold blooded and warm blooded.
5. Pisces, amphibian and reptilian are cold blooded while aves and mammalian are
warm-blooded animals.
6. Cold-blooded animals are also called poikilothermic animals.
7. Warm Blooded animals are also called homoeothermic animal.
8. Homoeothermic animals can generate and maintain heat within their body
independent of the environmental temperature.
9. Poikilothermic animals maintain their body temperature by absorbing heat from
the surrounding environment.
10. Pisces are aquatic and cold-blooded having two chambered heart and contain
gills for respiration.
11. Amphibians can live in water as well as on land. They have soft and moist skin
through which gaseous exchange takes place.
12. Metamorphosis is the rapid transformation from the larval to the adult form that
occurs in the life cycle of amphibians.
13. Reptiles have three-chambered heart except in crocodiles.
14. Pentadactyl limbs are absent in snakes.
15. Aves are a class of bipedal vertebrates with feathers, wings and a beak. The skin
is dry and loose and has no sweat glands. They are warm blooded.
16. Birds’ feathers are vital for flight, streamlining the body and insulation against
heat loss.
17. Mammals have external ear. The females have milk glands which secrete milk to
nouish the babies.
18. The sense of sight, smell and hearing are well developed in mammals.
PRO J ECTWORK
Visit different places around your home like pond, garden, etc. and observe different
types of vertebrate animals. If you are living in Kathmandu you can visit a zoo with
.your friends. List the name of animals you see around your home or at zoo in the
following table
Cold blooded Warm blooded
S.N. Pisces Amphibia Reptilia Aves Mammalia
1.
2.
3.
Blooming Science & Environment Book 7 165
Exercises
1. Fill in the blanks:
a. The transformation from the larval to the adult form is called ......................
b. Mammals have ................................ glands.
c. Heart in crocodile is ................................ chambered.
d. Limbs are absent in .................................
e. Salamander belongs to class.................................
f. External ear is present in .................................
g. The platypus lay eggs and belongs to class .................................
h. Lizards belong to class .................................
i. Animals whose body temperature change according to the surrounding
environment are called ................................
j. Whales have ................................ for respiration.
2. Choose the correct answer.
a. Which one of the following belongs to invertebrates?
i. Aves ii. Porifera iii. Amphibia iv. Mammalia
iv. Snake
b. Which of the following is warm blooded? iv. Frog
iv. Gills
i. Fish ii. Whale iii. Frog iv. Bat
c. Four chambered heart is found in :
i. Pisces ii. Mammals iii. Lizards
d. Fish respires through
i. Skin ii. Air sac iii. Lungs
e. Which of the following gives birth to a baby:
i. Labeo ii. Parrot iii. Lizard
3. Match the following.
Column A Column B
Whale Pigeon
Metamorphosis Three chambered heart
Penguin Pisces
Columba Aves
Reptiles Mammals
Sea-horse Amphibia
166 Blooming Science & Environment Book 7
4. Answer the following questions:
a. Define warm blooded and cold blooded animals .
b. Why do some animals hibernate?
c. Write the names of any two oviparous animals.
d. List out two general characteristics of fishes.
e. List out two general characteristics of reptiles.
f. What are the general characteristics of aves?
g. How can you say that the monkey is a mammal?
h. What are the five classes of vertebrates? Write three general characteristic
features of mammals and amphibians.
i. How do birds fly in the air?
j. What is summer aestivation?
k. Draw the tree sketch of animal kingdom.
l. What are mammals? Give three examples.
m. What are amphibians? Give three examples.
5. Define.
a. Vertebrates b. Warm blooded c. Cold blooded
d. Amphibian e. Invertebrates
6. Name one animals of the following character.
a. Has no legs. b. Lives both in water and on land.
c. Crawling animal. d. Having feathers on the body.
e. Lives in water only.
7. Differentiate between.
a. Cold-blooded and warm-blooded animals. b.Fish and amphibian
c. Oviparous and viviparous animals
8. Draw the diagram of the following organism.
a. Pigeon b. Frog c. Fish d. Lizard e. Cow
Glossary
Respond : react, do or say something to reply
Connect : join, attach
Stimuli : agents or factors that provoke interest or excitement
Accessory : an additional part that may be fitted to something for additional
function
Concerned: involved
Distinct : clearly different
Extreme : great or intense
Heterotroph: getting nutrients from organic substances
Blooming Science & Environment Book 7 167
B. Life Cycle of Frog
Frog
There are many species of frogs. Most frogs are similar in external appearance and
internal morphology. They differ only in colour, size and special features. The following
description is based on the Indian bull frog:
Classification of Frog
Kingdom : Animalia
Phylum : Chordata
Sub-phylum : Vertebrate
Class : Amphibian
Genus : Rana
Species : tigrina
Scientific name of frog is Rana tigrina.
Habit and Habitat
Frogs are generally found in or near fresh water such as ponds, ditches, rivers, streams
and lakes etc. and in moist places on land. The Indian bull frog lives in water most of
the time of course during rains it may be found far away from its aquatic home. During
breeding season they must come into pond water for copulation or pairing and for the
egg laying.
Water is a good breeding as well as protective medium from enemies. Frogs live in or
near water for the following reasons:
1) To escape from enemies by immediate jump and dive into the water.
2) Availability of plenty of insects near water.
3) To keep skin moist to carry on cutaneous respiration.(respiration by skin)
Frogs are non-poisonous, harmless and normally silent animals. Its presence is difficult
to notice unless it is disturbed.
Its important habits are:
1) It is diurnal i.e. active during daytime.
2) It is solitary in nature and only during breeding season males gather in shallow
water.
3) Locomotion: Frog swim in water and leap on the land. They are excellent
jumper.
168 Blooming Science & Environment Book 7
4) Feeding: Frog is carnivorous and feeds on small insects, snails, earthworms
eggs, small fishes. Sometimes larger frog eat the small ones. The longs and
sticky tongue captures small prey. The frog is simply a glutton and captures only
moving foods (insects, fishes etc.).
5) Camouflage: Frogs can change their body colour to match with the surrounding.
So they are not noticeable to enemies.
6) Breeding: Frogs generally breed in rainy season. Males gather to appropriate
shallow water and croak to attract females for mating.
7) Hibernation and Aestivation: The frog is
poikilothermic i.e. its body temperature
changes with temperature of its environment.
During winter, the frogs bury themselves deep
into mud and take rest-remains in a peculiar
dormant condition. This is called the winter
sleep or hibernation. Hibernation lasts for 3
to 4 months. During summer when the
temperature is very high and followed by Fig: Hibernating frog
drought, the frogs conceal themselves under water or moist place. This is known
as summer sleep or aestivation. It lasts for 1 to 15 days.
8) Croaking: Croaking is the characteristic noise or sound made by frogs. It is
commonly heard in breeding season during rainy seasons. It is a mating call
made by males to females.
External Features (Morphology)
Frogs are adopted for amphibian mode of life i.e. to live both in water and on land.
Their body is bilaterally symmetrical i.e. it can be divided into two exactly similar
halves along the mid dorsal line into left and right. The dorsal surface is green with
black spots and hard. The ventral surface is faint (pale) yellow and soft. A light yellow
mid-dorsal line runs from tip of snout to the cloacal opening on the back. The adult
frog is from 12 to 18 cm in length and 5 to 8 cm in width.
Eye Hump
Tympanum Cloacal
aperture
Fore limb
Web Hind limb
Blooming Science & Environment Book 7 169
Body is divided into head and trunk only. There is no neck. The body is streamlined
which makes swimming easy. Head is roughly triangular, somewhat flattened and
blunt at the anterior end. The anterior conical end of the head is the snout. There is a
pair of external nostrils near its extremity. Behind each nostril is a large spherical and
bulging eye placed on the top of the head. Each eye has three eyelids: Upper eyelid,
lower eyelid and third eyelid or nictitating membrane. The eyelids are without any
eyelashes. There are no external ears in frog but behind and slightly below each eye
there is a round depression covered by top grey membrane called tympanum, that
receives sound waves. The mouth is wide and extends from ear to ear as there is no
cheeks and lips. The cloacal aperture lies on slightly dorsal part of trunk. Trunk bears
two pairs of limbs laterally.
The forelimbs are shorter and the hind limbs are longer. Forelimbs bear four digits
without web but hind limb consists of five slender toes with web. Excretion, laying
eggs and sperm ejection occurs through cloacal aperture.
Life Cycle of Frog
The rainy season is the breeding period of the frogs. The period starts from early july
and continues till september. In the evening during rainy season male frogs croak to
attract the females. Females are slightly larger in size with pronounced abdomen due
to the production of large number of eggs. As the female approaches the males, the
male mounts on her back and presses her firmly by means of forelimbs which make
easier to lay the eggs. Then a female frog lays eggs in water. A floating clump of eggs
is called frog spawn. The large and slippery mass of eggs are too big to be eaten.
This is natural way of protecting them. But the smaller clumps of eggs will be eaten
by the creatures living near or in the pond. Soon after laying of eggs, the male sheds
the spermatic fluid containing a large number of sperms on eggs. The sperms and egg
unites in water and start to develop.
The single cell in the egg eventually splits into two. These two split making four cells
and so on. Eventually, there are many cells in the egg. The mass of cells in the egg
come to form an embryo. Organs and gills begin to form and in the meantime the
embryo lives off of its internal yolk.
This supplies it with nutrients for 21 days. After 21 days development period, the
embryo leaves its jelly shell, and attaches itself to a weed in the water. This quickly
becomes a tadpole, a baby frog.
The tadpoles grow until they are big enough to break free into the water. This can take
from 3 days to 3 weeks depending on what kind of frog they will become. They eat
every small plants that stick to larger plants in water. These tiny plants are called algae.
The tadpole has a long tail and lives in the water. It is extremely vulnerable and must
rely on its camouflage to protect it. The tadpoles also face danger by being eaten by
other water animals. Sometimes the pond dries up. As a result the tadpoles die.
170 Blooming Science & Environment Book 7
Eggs Embryo
Tadpole
Adult frog
Tadpole with 4 legs Tadpole with 2 legs
Fig: Life cycle of frog
After about five weeks, the tadpole begins to change. It starts to grow hind legs, which
are soon followed with forelegs. Behind their heads bulges appear where their front
legs are growing. Their tails become smaller. Lungs begin to develop, preparing the
frog for its life on land. Now and then, they wiggle to the surface to breathe in air.
They eat plants and decaying animal matter. Some tadpole eat frog’s egg and other
tadpoles.
Overtime, the tadpole becomes even more froglike. They shed their skin and lips. Its
mouth widens, and it loses its horny jaws. The tail is now almost vanished and the legs
grow. The lungs are almost functioning at this time.
This is the end of the tadpole stage. Such abrupt changes in body structures of tadpole
undergo a transition into the adult frog is called the metamorphosis. This metamorphosis
last typically only 24 hours.
Eleven weeks after the egg was laid, a fully developed frog with lungs, legs and no tail
emerges from the water. This frog will live mostly on land, with occasional swims. The
tiny frog begins to eat insects and worms. Eventually it will find a mate. The way this
is done varies depending on the species. The female lays the eggs, the male fertilizes
them and the whole process begins again.
Main Points to Remember
1. A process which begins from one stage and after passing a number of stages, it
is back again in the same stage is called life cycle.
2. Life cycle of frog completed in four stages. They are egg, embryo,tadpole and
adult.
Blooming Science & Environment Book 7 171
3. The animal which can live both on land and in water is called amphibia. Frog is
an amphibian.
4. The life cycle of frog starts in water and in adult it breathes through lungs.
5. External fertilization occurs in frog where female lays eggs in still water and
then male sprays sperms.
6. The young frog is called froglet.
7. The life cycle of frog is completed within 11-12 weeks.
8. During winter, the frogs bury themselves deep into mud and take rest-remains in
a peculiar dormant condition. This is called the winter sleep or hibernation.
9. During summer when the temperature is high and followed by drought, the frogs
conceal themselves under water or moist place. This is known as summer sleep
or aestivation.
10. The abrupt changes in body structures of tadpole undergo a transition into the
adult frog is called the metamorphosis.
PRO J ECTWORK
Draw the complete life cycle of frog on a chart paper and keep on the wall of your
classroom/study room.
Exercises
1. Fill in the blanks:
a. There are ............. stages in life cycle of frog.
b. Frog lives both in water and .....................
c. The animals which live both in water and on land are called...................
d. The young frog is called....................
e. The tadpole breathes through........................ in water.
2. Write true or false for the following statements.
a. Frog and toad are called mammals.
b. The young frog is called froglet.
c. Tadpole has a lung to breathe.
d. There is external fertilization in life cyce of frog.
e. The life cycle of frog is completed with in 12 weeks.
172 Blooming Science & Environment Book 7
3. Match the following.
Toad gills
Froglet adult
Tadpole young frog
Frog amphabian
4. Answer the following questions.
a. What is life cycle? Write stages of life cycle of frog.
b. What is external fertilization?
c. Define amphabians with examples.
d. What is called a froglet?
e. How does tadpole breathe in?
f. How does frog survive on land?
g. Draw life cycle of frog.
h. Describe the life cycle of frog with all stages.
i. What is cutaneous respiration?
j. Why do frogs croak?
k. What is the scientific name of Indian bull frog?
l. What is hibernation?
m. How many toes are found in forelimbs and in hind limbs?
n. What is the advantage of camouflage in frog?
o. Why do frogs have bulging eye?
p. What is metamorphosis?
Glossary
Mate : breed, reproduce
External : outer, outdoor
Predator : killer
Froglet : young frog
Clusters : group, bunch
Bugs : insects, termites
Wiggle : twist, worm
Camouflage: hiden disguise
Vulnerable: helpless, weak
Blooming Science & Environment Book 7 173
C. Plant Life
There are large number of living organisms in our earth. These organisms differ greatly
from each other. They have been divided into two broad kingdoms: plant kingdom and
animal kingdom. The plant kingdom includes all the green plants from lower plants
like algae to higher plants like rose, pea etc and non-green plants like mushroom and
yeast.
In this chapter, we will learn about plants.
Characteristics of Plants
1. Plants are fixed to the soil or substratum by the roots. So they cannot move from
one place to another.
2. Growth in plant continues throughout their lifetime. They show regeneration i.e.
a new plant grows from the broken or wounded body parts.
3. The plant body generally consists of root, leaf and stem.
4. The plant cell contains plastids, which has chloroplast due to which the plants
appear green.
5. Plants can prepare their own food using simple materials by the process called
photosynthesis. Thus, they have autotrophic nutrition.
Classification of Plants
Millions of different species of plants are found on the earth. Some of them produce
flowers and some do not.
On the basis of presence or absence of flowers, plants are broadly divided into two
types.
(i) Non-flowering plants (Cryptogams) and
(ii) Flowering plants (Phanerogams)
Cryptogams
Cryptos-Hidden, games - marriage.
These are the non-flowering seedless plants. So they reproduce by means of spores.
Characteristics Scan for practical experiment
a. They don't bear flowers and seeds.
b. They have autotropic or heterotropic mode of nutrition.
c. They may be unicellular or multicellular.
They are further divided into three divisions.
1. Thallophyta visit: csp.codes/c07e21
174 Blooming Science & Environment Book 7
2. Bryophyta
3. Pteridophyta
Thallophyta
1. They may be unicellular or multicellular.
2. The plant body of them is called thallus.
3. Their body is not differentiated into root, stem and leaves.
Thallophytes are further sub-divided into two sub - divisions:
i. Algae ii. Fungi
i. Algae Spirogyra Volvox
1. They are unicellular or multicellular
2. Mostly they grow in water or in damp soil.
3. They are autotrophs.
4. e.g. spirogyra, volvox, chlamydomonas, etc.
ii. Fungi Mushroom Mucur
1. They are generally multicellular except ' yeast'.
2. They are non-screen plants which do not have
chlorphyll in them.
3. Some are saprophytic and some are parasitic.
4. They are hetrotropic in nature.
e.g. yeast, mucor, mushroom, etc.
Bryophyta Moss Liverwort
1. They mostly grow in moist and shady places.
2. Their plant bodt is called thallus except moss.
3. They are amphibian plants because they nees
water for their reproduction.
e.g. riccia, liverwort, moss, etc.
Pteridophyta Fern Club moss
1. They grow in moist, cold and shady places.
2. They are most developed among the non-
flowering.
3. They are autotrophs.
4. They have well differentiated root, stem and leaves.
e.g. fern, horse tail, club moss, etc.
Blooming Science & Environment Book 7 175
Phanerogams Scan for practical experiment
Phanerogams include various types of highly developed plants
and they bear flowers and seeds. They are multicellular and
autotropic plants.
Phanerogams include various types of highly advanced plants.
They bear flowers. Flowers are beautiful and attractive parts of
a plant. The colours of the flowers are different. The flowers are visit: csp.codes/c07e22
important reproductive parts of a plant because they develop
fruits and seeds. From the seeds many new plants are grown. The plant body of them
is differentiated into root, stem and leaves. They can prepare their own food, so they
are known as autotrophs. These plants are further divided into sub-divisions. They are:
a. Gymnosperms b. Angiosperms
Gymnosperms
Gymnosperms are the most primitive of all seeded plants.
Characteristics
1. All the gymnospermic plants are woody
and live for many years.
2. The plant body is differentiated into well
developed root, stem and leaves.
3. They produce cones instead of the flowers. cycas
4. They have needle-shaped green leaves.
fir
5. Fruits are not produced in them so seeds are naked.
Examples: Pine, Cycas, Fir, Deodar, Dhupi, etc.
Angiosperms
Angiosperms are the most advanced group of flowering plants. Economically, they
include the most important plants as they are the source of our basic needs like food,
shelter and clothing They are primarily land plants. They are further divided into two
groups; monocotyledonous plants and dicotyledonous plants.
Monocotyledonous Plants
The plants with single cotyledons in their seeds or one seed leaf in their seeds are
called monocotyledonous plants.
Characteristics
1. They have fibrous root system. bamboo paddy
2. Leaves are usually long, narrow and
have parallel venation.
176 Blooming Science & Environment Book 7
3. They contain only one cotyledon in their seeds.
Examples: Maize, Wheat, Paddy, Barley, Bamboo, etc.
Dicotyledonous Plants
The dicotyledonous plants include those plants which have two seed leaves or two
cotyledons in their seeds. They include plants of all kinds of herbs, shrubs and
trees.
Characteristics
1. They have tap root system in their roots.
2. Usually leaves are broad and have reticulate neem tree gram plant
venation.
3. They bear two cotyledons in their seeds.
Example : Pea, Mustard, Gram, Mango, Orange, Neem, etc.
Activity
Observe various plants found in your locality. Make a list and make a table to
show their classes (groups) as shown below.
S.N Non flowering plants Flowering plants
Gymnosperms Angiosperms
Thallophyta Bryophyta Pteridophy
Monocot Dicot
Algae Fungi
Blooming Science & Environment Book 7 177
Similarities between Non-flowering and Flowering Plants.
Non-flowering Plants Flowering Plants
They may not be hydrophytes, They may be hydrophytes, mesophytes,
mesophytes, xerophytes and epiphytes. xerophytes and epiphytes.
Green non-flowering plants prepare
their own food with the help of carbon They prepare their own food by using
dioxide and water in the presence of carbon dioxide and water in the presence
sunlight except non-green flowering of sunlight.
plants.
Most of the non-flowering plants
are green, a few of them like mucor, All the flowering plants are green.
mushroom, etc. are non-green.
Dissimilarities between Non-flowering and Flowering Plants.
Non-flowering Plants Flowering Plants
They are simple and less developed plants. They are highly developed plants.
The plant body of them is not differentiated The plant body of such plants is
into root, stem and leaves except the plants differentiated into root, stem and
which belong to pteridophyta. leaves.
Most of the non-flowering plants are green All the flowering plants are green
in colour while some other like mushroom, in colour due to the presence of
mucor, etc. are not green due to absence of chlorophyll.
chlorophyll pigment.
Example: Spirogyra, Liverwort, Fern, etc. Example : Pea, Maize, Mango, etc.
Main Points to Remember
1. Plants may be unicellular or multicellular.
2. Plants are classified into two divisions: cryptogams and phanerogams.
3. Those plants which do not bear flowers are called non-flowering plants. They are
also known as cryptogams.
4. Those plants which bear flowers are called flowering plants. They are also known
as phanerogams.
5. Non-flowering plants are less developed while the flowering plants are highly
developed.
6. The plants which belong to thallophyta and bryophyte are primitive plants and
their plant body is not differentiated into root, stem and leaves except moss.
7. The plant body of ferns is differentiated into root, stem and leaves.
178 Blooming Science & Environment Book 7
8. Gymnosperms bear cones instead of flowers.
9. The seeds of gymnosperms are naked as these are not enclosed in fruits.
10. Angiosperms are well developed plants which bear flowers and seeds.
11. Monocotyledonous plants are those plants which bear one seed leaf in their
seeds.
12. Dicotyledonous plants are those plants which bear two seed leaves in their seeds.
PRO J ECTWORK
1. Collect some pond water containing green slippery substances. Put a drop
of water with the collected green substances on the glass slide. Observe the
slide by using a microscope. What do you observe on these substances under
the microscope? List the characteristics which you observe in such substances
with a figure in your science copy.
2. Visit a nearby garden and collect the name of five flowering and five non-
flowering plants of your surroundings. lete life cycle of frog on a chart paper
and keep on the wall of your classroom.
Non-flowering Plants Flowering Plants
Exercises
1. Tick () the correct and cross (×) the false statements.
a. Chlamydomonas is a multicellular plant.
b. Mushrooms cannot prepare their own food.
c. Moss belongs to the division thallophytta.
d. Rice and wheat are monocotyledonous plants.
e. Angiosperms produces naked seeds.
2. Encircle the non-flowering plants.
Barley, pine, spirogyra, wheat, fern, mucor, apple, moss
3. Answer the following questions.
a. What are cryptogams? Give any two examples.
b. Why is a mustard plant called a flowering plant?
c. List any two characteristics of maize.
d. List any two characteristics of angiosperms.
e. Write the similarities between flowering and non-flowering plants.
Blooming Science & Environment Book 7 179
f. List any two characteristics of monocotyledonous plants.
g. What are called saprophytes?
h. Classify non-flowering plants.
i. Classify flowering plants.
4. Define.
a. Unicellular plants b. Autotrophs c. Heterotrophs d. Hydrophytes
5. Differentiate between.
a. Gymnosperm and angiosperm
c. Monocotyledonous plants and dicotyledonous plants
d. Flowering plants and non-flowering plants.
6. What are the characteristics of pteriodophya? Write any two examples.
9. Why is classification of plants necessary?
10. Draw tree sketch of plant kingdom.
11. Identify the given figures with two characteristics.
Glossary
Unicellular: describing tissues, organs or organisms consisting of a single cell.
Multicellular: describing tissues, organs or organisms that are composed of a number
of cells.
Hydrophytes: a plant that lives either in very wet soil or completely or partially
submerged in water.
Mesophytes: any plant adapted to grow in soil that is well supplied with water
mineral salts.
Xerophytes: a plant that is adapted to live in conditions in which there is either a
scarcity of water in the soil or in deserts.
Epiphytes: plant that grows upon another plant but is neither parasitic nor rooted
in the ground.
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D. Parts of a Flowering Plant
Morphology of a Flowering Plant
Flowering plants are more developed than non-flowering plants. They have distinct
root, stem, leaves, flowers, etc. Generally flowering plants are multicellular and green.
A typical flowering plant has following parts:
a. Root system b. Shoot system
Root system
The part of a plant that remains underground is called root. It anchors the plant to the
soil. Mustard is a dicotyledonous plant that has a tap root. The main part of the root that
grows deep into the soil is called primary root. The primary root gives many branches
called secondary roots and inturn tertiary roots. The fine branches of tertiary roots are
called rootlets. The tip of a rootlet is soft and delicate which is covered by a root cap.
Behind the tip there are large numbers of hair-like outgrowths called root hairs.
primary root
secondary root
tertiary root
root cap
Tap root Fibrous root
In monocot plants like wheat, maize, rice, etc. have fibrous root instead of tap
root.
Functions
1. Root system gives fixation to the plants.
2. Roots absorb water and mineral salts from the soil.
3. They hold the soil particles firmly to prevent soil erosion.
The Shoot System
The stem with its branches along with leaves, flowers and fruits is called shoot system.
Usually it grows vertically above the soil. Based on the functions, the shoot system
consists of two organs. They are vegetative and reproductive parts.
Blooming Science & Environment Book 7 181
Vegetative Parts
The stem, branches and leaves are the vegetative parts of the plant.
The stem terminal bud
bud scale
The stem is the main axis of shoot system. It is the aerial part axillary bud
that develops from the plumule of the embryo of a seed. It is internode
green in colour. It bears lateral branches. The lower part of the
stem is thick and gradually thinner towards the apex. The stem node
has swollen points called nodes. The branches and leaves arise
from the nodes. The part of the stem between two nodes is called
internodes. In this way, the stem bears nodes and internodes.
Buds are condensed stem. On the basis of their position on the
plant, buds are of two types. They are axillary and terminal buds.
Axillary buds are born in the axil of leaves. These give rise to either branches or
flowers. Terminal buds are present at the apex of the stem and branches. They help to
increase the height of the plant.
Functions
1. The stem helps the plants to stand upright and supports the leaves and
branches.
2. It conducts water and minerals from root to the leaves for photosynthesis.
3. It also supplies the food from leaves to the other parts.
Leaf
A leaf is a thin, flattened, lateral outgrowth of a
plant. Leaves are borne on the nodes of the
stem and branches. They are green in colour
due to the presence of chlorophyll. A typical
leaf consists of three parts. They are leaf base,
petiole and leaf blade.
Leaf base: Leaf base is the lowermost part of the leaf. It connects the leaf to the node
of the stem. In some dicotyledonous plants like pea, the leaf base bears lateral outgrowth
called the stipules.
Petiole: Petiole is the stalk between the base and blade of the leaf. A leaf with
petiole is called petiolate leaf. If petiole is absent in a leaf, it is said to be sessile.
Usually the leaves are sessile in monocotyledonous plants like maize.
182 Blooming Science & Environment Book 7
petiolate leaf sessile leaf
Leaf blade: Leaf blade is also called lamina. It is a flattened, expanded green part of
the leaf. There is a midrib in the middle of the leaf blade runs from its base to the apex.
It gives rise to a number of lateral veins. These veins further to form a network of the
veinlets on the leaf blade.
The arrangement of veins and veinlets in the leaf blade of a leaf is called venation.
Venation of leaf is classified into two types. They are reticulate venation and parallel
venation.
Reticulate Venation
The arrangement of veins in a net-like form in the
leaf blade is called reticulate venation. This type
of venation is found in the dicotyledonous plants
like mustard, peepal, china rose, etc.
Parallel Venation reticulate venation parallel venation
The arrangement of veins is more or less parallel to one another in the leaf blade
is called parallel venation. It is found in the leaves of monocotyledonous plant like
maize, banana, bamboo, etc.
Functions
1. Leaves are green in colour due to the presence of green pigment called
chlorophyll. Thus, the leaves of plants can prepare their food during
photosynthesis.
2. Most of the leaves contain tiny pores called stomata. Through the stomata,
exchange of gases i.e., oxygen and carbon dioxide takes place during respiration
and photosynthesis.
3. Leaves help to remove the excess water by evaporation. This is called
transpiration.
Blooming Science & Environment Book 7 183
Activity
To study the different parts of a mustard plant
Materials required : A mustard plant Flower
Fruit
Method:
Stem Shoot
1. Visit the nearby field and uproot a Leaf
flowering plant of mustard system
without any harm to its root.
2. Take the plant and wash its roots Node {
gently with water. Internode
3. Hold the plant firmly and observe Bud
its parts. Primary root Root
Secondary root system
4. Identify the each part of the plant with
the help of the givenfigure.
Observation: A mustard plant has underground part and aerial part that lies
above the ground.
Conclusion: From this activity, we conclude that, a mustard plant is a flowering
plant. It has an underground part called root while the part above
the ground is called shoot.
Reproductive Parts
Flower
A flower is a modified shoot and in flowering plants it bears organs for sexual
reproduction. The flower parts are adapted to bring about pollination and fertilization
resulting in the formation of seeds and fruits. The stalk of the flower is known as
pedicel. The terminal part of the pedicel is called the thalamus. There are four types of
floral leaves such as sepals, petals, stamens and carpels, which develop from the nodes
of the thalamus. Petal
Parts of a Flower stigma anther
style filament
A typical complete flower
consists of calyx, corolla,
androecium and gynoecium.
sepal receptacle
overy
184 Blooming Science & Environment Book 7
a. Calyx
It is the outermost whorl of a flower. It is usually green in
colour and each individual members of the calyx is called
sepal. The calyx may be made up of free or united sepals.
The flower having free sepals is known as polysepalous calyx
flower, whereas the flower having united sepals is known as
gamosepalous flower. In the bud stage, calyx encloses and protects the delicate parts
of the flower.
b. Corolla
Corolla is the second whorl of a flower, which lies just inner to
calyx. It is composed of petals, which are brightly coloured. In some
flowers the petals are joining while in other flowers, they are free
from each other. Like calyx, the flowers with free petals are known as corolla
polypetalous flowers and those with fused petals are known as gamopetalous flowers.
Petals are sometimes scently and due to bright colour they attract bees, butterfly and
other insects that help in pollination of flower. The petals of some flower secrets sweet
nectar to attract the insects.
c. Androecium
Androecium is the male reproductive organ
of a flower that lies just inner to petals. The pollen grans
stamens are collectively called androecium. stamen
Each stamen has usually a filament and anther. Filament is the slender stalk of the
stamen, which bears the anther at its tip. The anther bears pollen grains or microspores.
The pollen grains are the male gametes.
d. Gynoecium
Gynoecium is the innermost whorl of a flower. It Stigma Pollen
grains
is the female reproductive organ of the flower. It Pollen tube
is composed of one or more carpels. Each pistil or Anther
gynoecium consists of three parts; ovary, style and Style
Ovule
stigma. The swollen basal part of the pistil is called Female
ovary. Ovary bears ovules. After fertilization the Ovary
Gamete
ovary gives rise to the fruit and the ovules develop
into seeds.
The slender stalk supporting the stigma is called the style. The stigma is the terminal
part of the pistil. During pollination, the pollen grains are deposited on the stigma.
Blooming Science & Environment Book 7 185
Functions of flower
1. The flowers have bright and attractive colour. They also possess fragrance, which
attract various types of insects. Insects help in cross-pollination.
2. Flowers are the source of honey, as they possess sweet nectar. Bees suck the
nectar and process it to make honey.
3. Flowers possess male and female organs by which fertilization occur. The male
and female gametes are fused to form zygote. The zygote later develops into a
seed. Under suitable condition seeds develop into plants.
4. The fruits are developed from the ovary of the flower whereas the seeds are
developed from the ovules.
Some terms related to Flower
Complete Flower: When all the four floral parts namely calyx, corolla, androecium
and gynoecium are present in a flower, it is called a complete flower. Mustard plant is
the example of complete flower.
Incomplete Flower: If one or more flower parts are lacking in a flower then we call
such flower as incomplete flower. Flower of the Oak tree is an example of incomplete
flower.
Bisexual Flower: If both male and female part, i.e., androecium and gynoecium are
present in a flower; we call such flower as a bisexual flower. e.g. Mustard plant.
Unisexual Plant: If the flowers possess either male or female part i.e., androecium or
gynoecium we call such flower as unisexual plant.
Fruit
Fruit is defined as a matured ovary containing seeds. It develops from the ripened
ovary after pollination and fertilization. There are varieties of fruits. The fruits are
of various coloured. They are found in different shapes and sizes according to the
plant, e.g. mango, apple, orange, banana, pomegranate, guava, berry (kafaal), leechi,
coconut, etc.
mango apple banana guava
The fruit consists of three parts. They are epicarp, mesocarp and endocarp.
1. Epicarp: It is the outermost covering of the fruit. It acts as the skin layer of the
186 Blooming Science & Environment Book 7
fruit. Its function is to protect the inner part of the fruit.
2. Mesocarp: It is the middle part of the fruit which is usually fleshy type. It forms
the edible part of the fruit.
3. Endocarp: The endocarp is the innermost hard stony part of the fruit that enclosed
the seed. Its main function is to give protection to the seeds.
epicarp
mesocarp
endocarp
seed
tomato apple mango
Functions of Fruit
The main functions of a fruit are as given below:
1. The fruits protect the seeds from unfavorable environmental conditions and
animals.
2. In most of the cases, fruits help in dispersal of seeds.
3. Fruits also provide nutrition to the developing embryo.
4. The fruit stores food materials which are used by animals as a source of food
energy.
Seeds
Seeds are developed from the fertilized ovules. They contain a baby plant or an
embryo, reserve food and protective coat. Seeds are of different colours, shapes and
sizes. Some seeds are very small and some are large. For example, the seeds of orchids
are so small as compared to the seeds of mango, coconut, peach, etc.
mango seed coconut seed
Types of Seeds
On the basis of the number of cotyledons, seeds are of two types. They are
monocotyledonous and dicotyledonous seeds. The gram, pea, bean, mustard, mango,
orange, etc. are dicotyledonous plants. The seeds of these plants contain two cotyledons.
The rice, wheat, maize, barley, etc. are monocotyledonous plants. Seeds of these plants
have only one cotyledon.
Blooming Science & Environment Book 7 187
Structure of a Dictotyledonous Seed: Pea
The basic structure of pea and other plants seeds is same. The pea seeds are large
and round in shape. A pea seed has three parts. They are seed coat, an embryo and
cotyledons.
1. Seed coat: It is the outermost covering of the seed. It is made up of two layers :
outer testa and inner tegmen. It protects the inner part of the seeds from injury,
high temperature, microbes and insects.
A large scar left by the stalk of the seed is hilum. It is also the point of attachment to
the fruit.
There is a tiny pore at one end of the seed coat, called micropyle. When the seeds are
soaked in the water, the water enters through the micropyle. This results the swelling
of the seeds and helps to germinate.
Seed coat
Plumule
Cotyledons Hypocotyl
Radicule
2. Cotyledons: On either side of the embryo, two cotyledons are present. They may
store the food for the growing embryo.
In some seeds like dicotyledonous seeds of castor, endosperm is present on one side
of the embryo surrounding the embryo on all sides. Such seeds are called endospermic
seeds. Endosperm is fleshy in which food is stored for the growing embryo.
In most of the seeds like bean, pea, mango, gram, etc. endosperm is absent. Such
seeds are called non-endospermic seeds. In these seeds the food is stored in cotyledons
during the maturation of seeds.
3. Embryo: An embryo is called baby plant. It is present with one of the cotyledons.
It contains distinct lower part, the radicle and upper part the plumule. During the
germination of the seed, the radicle grows into the root while the plumule grows
into the shoot of the plant.
Structure of Monocotyledonous Seed : Maize
Maize is one seeded fruit or grain. It is more or less flattened and triangular on one
side. Each maize grain is made up of the following parts.
188 Blooming Science & Environment Book 7
Endosperm Seed coat endosperm
Embryo Aleurone layer
Scutellum
seed of maize Coleoptile
Plumule
Radicle
Coleorhiza
Maize cob Longitudinal section of maize seed
Seed coat: It is the outermost covering of the grain. In this, the seed coat and fruit wall
are fused together to form a protective layer.
Embryo: On one side of the grain, there is a light white coloured small egg-shaped
area. This area contains the embryo. An embryo contains a single lateral cotyledon and
embryo axis with plumule and radicle are at its two ends. The radicle is present at the
pointed part of the seed while the plumule is found in the flat part.
The major portion of the grains is occupied by endosperm. It is yellow or white
coloured food materials in the form of proteins and starch. Thus, the maize is called
endospermic seed. Beside maize, the other monocotyledonous seeds like rice, wheat,
etc. are also endospermic seeds.
Functions of Seeds
1. A seed develops into a new plant after getting suitable conditions. Therefore it
helps in reproduction.
2. The cotyledons of seeds store the food material which is used during the
germination of seed while germinating. A seed cannot manufacture food
itself.
3. The seed coat of the seeds protects the inner part of the seeds from injure,
microbase and insects.
Germination of seed
The process of development of an embryo of a seed into a new plant uder a suitable
condition is called germination. The embryo of seeds remains inactive but alive till
environment is not suitable for germination for a short or a long duration of time after
maturation. it means that, the seeds of some plants grow into new plants as soon as the
seeds get a suitable conditions like, soil, water, light, air and suitable temperature. Some
seeds like seeds of cereals remain inactive and do not germinate immediately after
maturation. Such seeds are caled dormant seeds. After the completion of dormancy
period and onset of suitable conditions, the seed begins to germinate.
Blooming Science & Environment Book 7 189
Activity
To prove that air, water and suitable temperature are essential for the
germination of seed.
Material required: a beaker, a ruler, three bean seeds thread.
Method:
1. Take three bean seeds and tie them with thread at
three positions of a ruler as shown in the figure.
2. Take a beaker and put the ruler with the seeds into
the beaker.
3. Pour water into the beaker in such a way that the
lowest seed is under the water, the middle one is
partly immersed in the water and the uppermost
seed is in the air.
4. Let the beaker remain in warm place for a fewdays. After that, what will you
observe?
Observation
You wil see that the lowermost seed does not germinate and gets decay due to
water. The uppermost seed remains as such and has no sign of germination. But
the middle one germinates to form a small new plant.
Conclision
The middle sed germinates into a new plants because it gets all the conditions.
From this activity, we have concluded that the seed requires air, water and suitable
temperature to germinate.
Differences between Monocotyledonous Seeds and Dicotyledonous Seeds
Monocotyledonous Seeds Dicotyledonous Seeds
The seeds have only one cotyledon. The seeds have two cotyledons.
Generally seeds are endospermic. Generally seeds are non-endospermic.
Hilum and micropyle are very much Hilum and micropyle are distinct.
small.
It is a single seeded fruit. The seeds are formed inside the fruit.
Embryo or baby plant is very small. Embryo or baby plant is large.
There is one seed coat. There are two seed coats called testa
and tegmen.
Plumule is very small. Plumule is large.
Example : Maize, rice etc. Example: Pea, gram, etc.
190 Blooming Science & Environment Book 7
Activity
To observe cotyledons in a seed.
Materials required: different seeds like wheat, maize, castor, bean and pea, etc.
a beaker with water.
wheat maize bean Rajma
Method
1. Take a beaker with some water.
2. Soak some seeds like wheat, maize, castor, bean and pea in the water for a
day.
Observation
After a day, gently peel the seed coat and find out how many cotyledons each of
the seeds has.
Conclusion
We find that seeds like castor, bean and pea have two cotyledons, while the maize
and wheat seeds have only one cotyledon.
Main Points to Remember
1. The plant is basically divided into the root system and the shoot system.
2. Root helps in fixing the plant to the soil and absorption of water and minerals
from the soil.
3. Tap root produces many lateral branches from the main root whereas adventitious
root produces cluster of fibrous root from the base of the stem.
4. Dicot plants have tap root whereas monocot plants have adventitious root.
5. The shoot system can be divided into vegetative parts (stem, leaves, branches)
and reproductive parts (flower).
6. Stem has nodes and internodes, buds, leaves and branches.
7. Stem helps to mobilize water, mineral salts and food materials around the plant
body.
8. Leaf is the major organ for photosynthesis.
9. Leaf consists of leaf base, petiole and lamina. Leaf base is lowermost part.
Petiole is a long stalk. Lamina is the flattened and most important part of a
leaf.
10. The arrangement of veins may be irregularly distributed forming a network
(reticulate venation) or run parallel to each other (parallel venation).
Blooming Science & Environment Book 7 191
11. The stalk of the flower is known as pedicel.
12. Thalamus is the terminal part of pedicel.
13. A complete flower consists of calyx, corolla, androecium and gynoecium.
14. The outermost whorl of the flower is calyx. The sepals are collectively called
calyx.
15. Corolla is the second whorl of the flower. The petals are collectively called
corolla.
16. Petals attract bees, butterfly and other insects, which help in the pollination of
flower.
17. Androecium is the third whorl of the plant. It is the male reproductive part of
flower. The stamens are collectively called androecium.
18. Gynoecium, a female reproductive part is the innermost whorl of the flower. The
pistils are collectively called gynoecium.
19. Ovary and ovules of a gynoecium give rise to fruit and seed respectively.
20. When both androecium and gynoecium are present in the same flower, it is
referred as bisexual flower.
21. When only one of these whorls is present, it is referred as unisexual and
incomplete flower e.g. cucumber.
22. The fruit consists of three parts namely epicarp, mesocarp and endocarp.
23. On the basis of cotyledons seed are classified into two categories: monocotyledons
and dicotyledons.
24. A typical; seeds is made up of seed coat, embryo and endosperm.
25. Seeds store essential nutrients for the embryo.
PRO J ECTWORK
Collect different flowers around your home. Observe different parts of the flower.
Look for calyx, corolla, androecium and gynoecium. What differences do you find
among these flowers? List out the major characteristics of the flowers in your
notebook. Record the number of sepals, petals, statemens and pistils of a flower in
a sheet of paper. If you find newkind of flower, take it to your school and show it to
your teacher and learn more about it.
Exercises
1. Fill in the blanks.
a. Ovary gives rise to ........................ and ovule gives rise to ...........................
b. ................................ is the fourth whorl of a flower.
c. Each anther consists of ................................ lobes.
192 Blooming Science & Environment Book 7
d. Gynoecium is composed of one or more .................................
e. Mustard is the example of ................................ plant.
f. The flattened part of the leaf is called .................................
g. The space between two successive nodes is called the .................................
h. The outermost whorl of the flower is .................................
i. Monocot plants have ................................ root.
j. The stalk of the flower is known as .................................
2. Match the following.
Column A Column B
Tap root Reproductive organ
Androecium Petals
Dicot Vegetative part
Epicarp Outer layer of fruit
Corolla Tomato
Shoot system Radicle
3. Write down 'True' or 'False' and correct false statements.
a. Tap root system is present in dicotyledonous plants.
b. Wheat and maize are the examples of dicotyledonous plants.
c. Tap root system develops from the radical of the embryo.
d. A flower with united sepals is called gamosepalous flower.
e. Pollen grains are not deposited on the stigma during pollination.
f. The hardest part of fruit is endocarp.
g. A complete flower consists of a calyx, corolla and gynoecium.
h. Ovary and ovules of a gynoecium give rise to seed and fruit respectively.
i. Thalamus is the terminal part of pedicel.
j. When both androecium and gynoecium are present in the same flower, it is
referred as bisexual flower.
4. Answer the following questions:
a. Give the name of four plants having tap root and adventitious root system
respectively.
b. What are the basic functions of a root?
c. What are the functions of stem?
d. Draw a well-labeled diagram of a leaf.
e. Name two types of venation and define them.
f. What is the function of leaves?
Blooming Science & Environment Book 7 193
g. Describe the parts of a leaf with a suitable diagram.
h. Draw a flowering plant and label its parts.
i. Which part of a seed gives rise to root and shoot of a plant.
j. Differentiate between:
i. Vegetative part and reproductive part
ii. Taproot and adventitious root
iii. Root and stem
iv. Reticulate and parallel venation.
k. Draw a well-labelled diagram of a flower and label its parts.
l. Describe the male and female reproductive organs of a flower.
m. What are the functions of a flower?
n. Give the name of different parts of a fruit.
o. What are the functions of a fruit?
p. Why are seeds important for plants?
q. Name the different types of seeds.
r. Differentiate between dicotyledons and monocotyledons.
s. What are the functions of a seed?
t. List 5 monocot and 5 dicot plants.
u. Draw a seed and label its parts.
5. Write short notes on.
a. Flowering plant b. Dicot plant
c. Pollination d. Fertilization
6. Differentiate between. b. Taproot and adventitious root
a. Vegetative part and reproductive part d. Reticulate and parallel
c. Root and stem
Glossary
Vary : differ
Absorption : taking of liquid into the substance
Store : put something safely to use in future
Maturation : process of becoming mature
Adverse : unfavourable, undesirable, harmful
Sweel : increase in size
Endosperm : the tissue that surrounds the embryo in a seed
194 Blooming Science & Environment Book 7
16Chapter Cell
Learning Outcomes
On the completion of this unit, students will be able to: Estimated Period-6+3
• describe structure of plant and animal cells.
• describe cell organelles of animal cell and plant cell.
• describe function of some cell organells
• describe an unicellular organism (Amoeba) and multicellular organism
(Hydra) in brief.
Introduction
Cell is the basic unit of life. It is responsible for the shape and structure of a living
body. As a building is made up of bricks, a living body is made up of cells. The work
done by a living body is the total work done by all the cells. So, a cell is the structural
and functional unit of life.
All the living beings from plants to animals are made up of cells. Thus all the living
beings are cellular. The skin, muscles, blood of an animal body and stem, leaves, root
of a plant body are made up of cells.
Discovery of Cells
The word cell is derived from the Latin word “Cellula” which means “a little
room”.
The discovery of cells dates back to 1664 AD, when, British Botanist Robert Hook
gave the name cell to the honey comb like structure observed in a slice of botlle cork
under his crude miscroscope.
In 1840 AD, J.R. Purkenje used the term protoplasm to describe the juicy, slimy
contents of the cell. The protoplasm was referred to the physical basis of life.
Thus, it was cleared that all organisms from unicellular to multicellular organisms are
made up of cells and every cell has protoplasm to conduct life activities like growth,
movement, sensitivity, respiration, reproduction etc.
The Cell: Shape, Size and Structure
The structure and shape of cells differ from species to species and organ to organ of
living organism. Even a plant cell differs from an animal cell. The cell of particular
shape found in different parts of the plant or animals body is according to the function
it has to perform.
Blooming Science & Environment Book 7 195
Unicellular organisms like amoeba, white blood cells (WBC) constantly change
their shape whereas nerve cells, Red blood cells (RBC) and plant cells have fixed
shape.
A cell may be irregular (Amoeba, WBC), flat (skin cells), spindle shaped (muscle
fibers), spherical (RBC) or cubical in shape.
Cells are generally too small to be seen through our naked eyes. Except some big
cells like eggs of birds, all other cells can be seen through microscope. Thus, cells are
microscopic.
The size of a cell ranges from 0.1µ to 1µ (micron). The smallest size of the bacteria
cell is 0.5µ. The smallest cell of human being is the red blood cell. The longest cell is
the nerve cell, which may be up to 3 or 3.5 feet in length. Among plants, the size of
the fibers can be of the size of the plant itself. The largest cell is the egg of an Ostrich,
which is around 17cm in diameter.
The size of a cell is measured in micron (µ).
1 cm = 10 mm 1 mm = 1000µ
Red Blood Cell Muscle fibre Cells of Onion
Paramecium Nerve cell Human cheek cells
The Structures of the Cell
The cell is essentially composed of a living substances known as protoplasm. The
protoplasm of the cell mainly consists of two parts. They are a central nucleus and
fluid substance known as cytoplasm. The plant and animal cells show the following
structures:
196 Blooming Science & Environment Book 7
Cell Cell wall
membrance Cell
Membrance
Mitochondrion Vacuole
Centriole
Cytoplasm
Necleolus Nuclear Membrane
Nucleus Necleus
Nuclear Cytoplasm Nuceleolus
Membrane
Fig: Animal Cell Fig: Plant Cell
a. Cell Wall
The outermost part of the plant cells is called cell wall. It is a non-living rigid layer,
made up of cellulose. Its function is to protect and determine the shape of the plant
cells. The cell wall is absent in animal cells.
b. Cell Membrane
It is a living layer which is also called plasma membrane. It represents the outermost
layer of animal cells, whereas in plant cells, it is found below the cell wall. Its main
function is to control the entrance and exit of substances. It also gives shape and
rigidity to the cells.
c. Cytoplasm
The cytoplasm is the fluid content lies inside the cell membrane. It is the thick jelly like
solution that fills each cell and is enclosed by the cell membrane. It is mainly composed
of water, salts and proteins. All of the organelles such as nucleus, endoplasmic
reticulum, mitochondria , plastids, etc are located in the cytoplasm. Presence of large
central vacuole pushes the cytoplasm to the sides. So, in a plant cell, a thin layer of
cytoplasm is seen in the periphery whereas in an animal cell it covers all the area inside
the cell. Some importabt cytoplasmic organelles are given below:
i. Vacuoles
A plant cell has big and central vacuole. In an animal cell, small and temporary vacuoles
are seen. These may be absent in some animal cell whereas they are comparatively
many in plant cells. They are used to transport and store nutrients, water and waste
materials.
Vacuoles are fluid filled spaces. In the plant cells, the vacuoles are filled with a fluid
called cell sap, which is a solution of water and water soluble materials. In animal
cells, vacuoles are smaller in size and lesser in number than that in plant cells.
In animal cells, vacuoles do different functions. For example, in amoeba two types of
vacuoles are found. The contractile vacuole is capable of excreting waste substances
while food vacuole is concerned with digestion and absorption of food.
Blooming Science & Environment Book 7 197
ii. Plastids
These are important cell organelles of a plant cell. Chromoplast (coloured), Leucoplast
(white or colourless) and Chloroplast (green) are found in different parts of the plant
according to their functions. Such plastids are completely absent in an animal cell.
These all are involved in different functions like photosynthesis, storing of food and
colouration, etc.
iii. Centrosome
These are present in an animal cell only. They are found near the nucleus and help in
cell division by forming spindle fibers.
iv. Lysosomes
These are also found in the animal cell and secrete enzymes (digestive juices). These
are also called suicidal bags of a cell.
v. Golgi Bodies
They are sac like structures responsible for secretion, synthesis and storage of various
organic compounds. They are found close to the nucleus in an animal cell. They are
scattered in a plant cell and are known as dictyosomes.
vi. Mitochondria
These are rod shaped structures scattered in the cytoplasm. Their main function is to
produce energy. They are also called power house of a cell.
d. Nucleus
This is a very important part of a cell. It is usually Nuclear
shpherical in shape but in plant cells, it is often flat due membrance
to its displacement to a peripheral position. Nucleo plasm
It is bounded by two thin membranes called nuclear Nucleolus
membrane. The nucleus contains one or more dense
rounded bodies. Each is known as nucleolus. A nucleus Centrosomes
also contains chromosomes in it.
In some unicellular plants like virus and bacteria, there is no nucleus but there is a
presence of chromatin in them. The size of the nucleus varies from cell to cell.
Functions:
a) The nucleus transmits the hereditary characteristics from parents to the offsprings.
b) It controls all the activities and functions of the cell.
c) It takes part in cell division.
198 Blooming Science & Environment Book 7
Activity Scan for practical experiment
Study of plant cells
Materials required : Fleshy leaf from onion bulb ,
Forceps, Glass slides, Cover slip,Water slip, Water
Microscope, etc.
Method: visit: csp.codes/c07e24
Take out fleshy leaf from an onion bulb. With the help of
forceps, peel off the thin upper membrane of this leaf. Colour the cells for a few
minutes by dipping it in safranine. Put a drop of water
in the center of a glass slide. Place a bit of the coloured
membrane on the slide and cover it with a cover slip.
Examine under a microscope.
You will observe a brick like arrangements of cells. All
the cells are adjoined. Thin cell wall, prominent nucleus
and faint protoplasm can also be seen.
Draw the structure in your science notebook.
Activity
Study of animal cells
Materials required : Scalpel Glass slides,
Cover slip, Water, Microscope, etc.
Method
Scrap gently the inside of your cheek with a scalpel.
Place a drop of water on a glass slide. Put the tissue in the liquid and cover it with
a cover slip. Examine under the microscope.
You will notice a group of irregular cells. Here also cell membrance, nucleus and
faint protoplasm can be seen.
Differences between Animal and Plant Cells.
Some major differences between animal and plant cells are as given below
Animal Cell Plant Cell
It is smaller in size. It is larger in size.
Cell wall is absent. Cell wall is present.
Plastids are absent. (except euglena) Plastids are present.
Vacuoles are small and many in number. Vacuoles are larger and few in number.
Centrosome is present. Centrosome is absent.
Blooming Science & Environment Book 7 199
Similarities between Plant Cell and Animal Cell
1. Both of them contain cytoplasm.
2. Both of them contain ribosomes.
3. Both of them have a cell membrane.
4. Both of them contain endoplasmic reticulum.
5. Both of them contain nucleus.
Amoeba
Amoeba is a unicellular organism. Its body is made up of single cell. All the life
activities like nutrition, respiration, reproduction, digestion etc. are performed within
a cell.
Structure
Amoeba is very small. They cannot be seen with naked eyes. They can be seen with
the help of microscope. Nucleus
The shape of amoeba is irregular. Its body Vacuole Cell membrance
is covered by an elastic membrane called
plasma lemma. Due to the elasticity
of plasma lemma, it can produce
pseudopodia and change its shape.
Pseudopodia are the false feet. They are Cytoplasm Pseudopodia
finger like projections produced at the
Fig: Amoeba
time of locomotion. They are used for
locomotion and capturing the food materials.
Inside plasmalemma, protoplasm is found. It has two parts: outer non-granular
ectoplasm and inner granular endoplasm.
Food vacuoles, contractile vacuoles and nucleus are found inside endoplasm. Vacuoles
containing food is called food vacuoles. The food within food vacuole is digested with
the help of protoplasm. Undigested food is thrown out from plasmalemma.
Contractile vacuoles store excess water. They move near the cell membrane and burst
to remove excess water. They regulate water content in the cell.
Nucleus is round and contains chromatin materials. It helps in growth and reproduction.
Habitat of Amoeba
Amoebae are of different kinds. They are found at different places. Some are found in
water some in soils and some are found inside the body of animals.
200 Blooming Science & Environment Book 7
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