Living Science Biology Class 8 ICSE Solutions Chapter 2 Reproduction, Development and Growth

ICSE Living Science Biology for Class 8 Solutions Chapter 2 Reproduction, Development and Growth

Check Your Progress 1

Fill in the blanks.
Question 1.
The reproductive sex cells are known as ……………….
Answer:
The reproductive sex cells are known as gametes.

Question 2.
……………. is a non-green plant, which reproduces by budding.
Answer:
Yeast is a non-green plant, which reproduces by budding.

Question 3.
…………….. takes place in plants which do not produce seeds.
Answer:
Vegetative Propagation takes place in plants which do not produce seeds.

Question 4.
Sugarcane and pineapple are grown from …………….
Answer:
Sugarcane and pineapple are grown from cutting.

Question 5.
In grafting from one plant is attached and tied to the rooted stem called …………….. of another plant.
Answer:
In grafting scion from one plant is attached and tied to the rooted stem called stock of another plant.

Check Your Progress 2

Fill in the blanks.
Question 1.
The male reproductive part in flowers is called
Answer:
The male reproductive part in flowers is called androecium

Question 2.
Complete flowers are also called ………… or ……….. flowers.
Answer:
Complete flowers are also called bisexual or hermaphrodite flowers.

Question 3.
The process by which a sleeping or dormant embryo becomes active and grows into a new plant in known as
Answer;
The process by which a sleeping or dormant embryo becomes active and grows into a new plant in known as germination.

Question 4.
The lower part of the uterus called ………… is …………. connected to the vagina.
Answer:
The lower part of the uterus called cervix is connected to the vagina.

Question 5.
The time between \fertilization and birth is called ……………….
Answer:
The time between fertilization and birth is called pregnancy.

Question 6.
……………….. starts from birth and lasts till about two years of age.
Answer:
Infancy starts from birth and lasts till about two years of age.

A. Tick the most appropriate answer.

Question 1.
The simple division of an organism into two smaller daughter cells of roughly equal size is called
a. binary fission
b. multiple fission
c. fragmentation
d. budding
Answer:
a. binary fission

Question 2.
Which of these can be reproduced by its stem ?
a. Carrot
b. Bryophyllum
c. Rose
d. Papaya
Answer:
c. Rose

Question 3.
An incomplete flower with only androecium is called a
a. hermaphrodite flower
b. pistillate flower
c. bisexual flower
d. staminate flower
Answer:
d. staminate flower

Question 4.
Flowers which have all the four whorls are called
a. neutral flowers
b. staminate flowers
c. complete flowersd.
d. incomplete flowers
Answer:
c. complete flowers

Question 5.
A pollen tube grows through the
a. filament
b. style
c. anther
d. ovary
Answer:
b. style

Question 6.
Seeds are produced from
a. ovules
b. anthers
c. pollen grains
d. eggs
Answer:
a. ovules

Question 7.
An embroyo consists of –
a. cotyledons and embryonal axis
b. plumule and radicle
c. plumule and cotyledons
d. cotyledons, embryonal axis and radicle
Answer:
a. cotyledons and embryonal axis

Question 8.
Sperms are produced by –
a. urethra
b. ureter
c. testes
d. ovaries
Answer:
c. testes

Question 9.
Testes are present in a sac called –
a. sternum
b. scrotum
c. sperm duct
d. semen
Answer:
b. scrotum

Question 10.
The sperms reach urethra by travelling through –
a. scrotum
b. testes
c. sperm duct
d. vagina.
Answer:
d. vagina.

Question 11.
The female sex hormones secreted by ovaries are –
a. progesterone and testosterone
b. progesterone and oestrogen
c. thyroxine and testosterone
d. oestrogen and testosterone
Answer:
b. progesterone and oestrogen

Question 12.
The release of an egg from an ovary is called –
a. fertilization
b. menopause
c. menstruation
d. ovulation
Answer:
d. ovulation

Question 13.
From the third week of development till the end of the second month of pregnancy, the developing organism is called –
a. infant
b. embryo
c. foetus
d. zygote
Answer:
b. embryo

Question 14.
The embryo is attached to the uterus by a special structure called –
a. umbilical cord
b. placenta
c. stalk
d. oviduct
Answer:
a. umbilical cord

B. Write true or false for each statement. Rewrite the false statements correctly.

Question 1.
Sexual reproduction involves the fusion of an egg and a sperm.
Answer:
Tme

Question 2.
The development of a new plant from the vegetative part of a plant is called fragmentation.
Answer:
False. The development of a new plant from the vegetative part of a plant is called vegetative propagation.

Question 3.
A whole new plant can grow from the eye of a tuber.
Answer:
True

Question 4.
Cutting and layering are natural means of asexual reproduction.
Answer:
False. Cutting and layering are artificial means of asexual reproduction.

Question 5.
The male gamete travels down each pollen tube and fuses with the ovule present in the ovary.
Answer:
False. The male gamete travels down each pollen tube and fuses with the egg cell present in the ovule.

Question 6.
In hypogeal germination, the cotyledons remain below the soil.
Answer:
True

Question 7.
Fallopian tubes carry the ova from the ovary to the uterus.
Answer:
True

Question 8.
Oestrogen is a female sex hormone.
Answer:
True

Question 9.
Marked changes in the appearance of an organism as it develops from an egg to an adult is called development.
Answer:
False. Marked changes in the appearance of an organism as it develops from an egg to an adult is called metamorphosis.

Question 10.
Infancy is the stage of growth which starts at the age of 12 years.
Answer:
Infancy is the stage of growth which starts as soon as a child is born.

C. Fill in the blanks.

Question 1.
Under unfavourable conditions certain organisms develop a …………. for protection.
Answer;
Under unfavourable conditions certain organisms develop a cyst for protection.

Question 2.
The small outgrowth arising from the yeast cell is called a ………….
Answer:
The small outgrowth arising from the yeast cell is called a bud.

Question 3.
The stem cutting which is grafted on the stem of a rooted plant is called a …………
Answer:
The stem cutting which is grafted on the stem of a rooted plant is called a grafting.

Question 4.
Calyx consists of green leaf-like structures called ………………….
Answer:
Calyx consists of green leaf-like structures called sepals.

Question 5.
The gynoecium consists of …………. and …………
Answer:
The gynoecium consists of ovary, style and stigma.

Question 6.
Pollination taking place between tw o flowers present on two separate parent plants is called ………..
Answer:
Pollination taking place between two flowers present on two separate parent plants is called cross pollination.

Question 7.
The radicle develops into a ………….
Answer:
The radicle develops into a root.

Question 8.
In peas, germination is ………….
Answer:
In peas, germination is epigeal germination.

Question 9.
In maize, the germination is ………..
Answer:
In maize, the germination is Hypogeal germination.

Question 10.
When an ovum fuses with a sperm outside the body, it is called …………..
Answer:
When an ovum fuses with a sperm outside the body, it is called external fertilization.

Question 11.
The fusion of an egg with a sperm results in the formation of …………..
Answer:
The fusion of an egg with a sperm results in the formation of zygote.

Question 12.
The ………… is the larval stage of a butterfly.
Answer:
The caterpillar is the larval stage of a butterfly.

D. Define these terms.
1. multiple fission
2. budding
3. hybridization
4. germination
5. puberty
6. ovulation
7. menstruation
8. menopause
9. metamorphosis
10. adolescence
Answer:
1. multiple fission – The process of asexual reproduction in which the body of parent individual divides in to many new individual or daughters under unfavourable conditions.

2. budding – The formation of daughter individual from a small projection called bud, arising from the parent body is known as budding.

3. hybridization – The process of cross breeding done by artificial pollination to have a variety of crop, which has characteristics of both the parent varieties is called hybridization.

4. germination – The process by which a sleeping or dormant embryo becomes active and grows into a new plant is known as germination.

5. puberty – The attainment of sexual maturity is called puberty.

6. ovulation – The release of an egg from an ovary is called ovulation.

7. menstruation – The cyclic discharge of blood, mucus, unfertilized egg and other substances from the uterus at an average interval of 28 days in the reproductive life of human female is called menstruation.

8. menopause – At the age of 45-50 years when no eggs are released and a woman can no longer reproduce, this stage is called menopause or the permanent stoppage of menstruation.

9. metamorphosis – The kind of changes in the appearance of an organism as it develops from an eggs to an adult are called metamorphosis.

10. adolescence -The period of life when the body undergoes changes leading to reproductive maturity.

E. Differentiate between

Question 1.
asexual reproduction and sexual reproduction.
Answer:
Asexual Reproduction :

1. Always monoparental
2. It does not involve the formation and fusion of gametes.
3. No sex organs are formed
4. New individual develops from a cell or a part of one parent.
5. The new individuals are genetically similar to the parent.

Sexual Reproduction :

1. usually biparental
2. It involves the formation and fusion of two types of gametes.
3. Sex organs are always formed
4. New individual develops from a Zygote.
5. The new individuals are genetically different from either of the two parents.

Question 2.
binary fission and multiple fission.
Answer:
Binary fission :

1. Nucleus divides in to two parts.
2. It occurs under normal conditions
3. It give rise to two individuals.

Multiple fission :

• Nucleus divides in to many parts.
• It takes place during unfavourable conditions
• If forms many individuals.

Question 3.
sexual reproduction and vegetative propagation.
Answer:
Sexual Reproduction :

• New individual develops from the fertilization two different gametes.
• New organism produced is not exactly similar to the parents.
• Fusion of two gametes occurs.

Vegetative propagation :

• New individual develops of from vegetative part of plant i.e. from root, stem or leaf.
• New individual developed is exactly the same as the parent plant.
• There is no fusion of gametes in it.

Question 4.
cutting and grafting
Answer:
Cutting :

• The portion of any plant organ like root, stem, leaf or bulb used for vegetative propagation of plant.
• No new varieties are developed.

Grafting :

• In this process stem cutting (scion) is attached to the stem of another plant (stock) having extensive root system.
• It helps in developing new varieties.

Question 5.
self pollination and cross pollination.
Answer:
Self pollination :

• Self pollination is the transfer of pollen grains from anther to filament within the same flower.
• It occurs either in the same flower or another flower of the same plant.
• It occurs in the flowers which are genetically same.

Cross-pollination :

• Cross pollination is the transfer of pollen grains from anther to filament of another flower.
• It occurs between two flowers that are on different plants but are of the same species.
• It occurs between the flowers which are genetically different.

Question 6.
epigeal germination and hypogeal germination.
Answer:
Epigeal germination :

• In this type of germination two cotyledons are pushed up through the soil.
• It is observed in dicot seeds.
• It occurs in beans, peas.

Hypogeal Germination :

• In this type of germination the cotyledon remain below the soil.
• It occurs in monocot seeds.
• It occurs in maize.

Question 7.
external fertilization and internal fertilization.
Answer:
External fertilization :

• The fusion of sex calls occurs outsidé the body.
• It occurs in fishes and frogs.

Internal Fertilization :

• The fusion of sex cells occurs inside the body.
• It occurs in mammals, birds and reptiles.

F. Write short answers.

Question 1.
What is tissue culture ?
Answer:
The production of plants by cell or tissues or organs in a synthetic medium with suitable nutrients is called tissue
culture.

Question 2.
Define hybrid.
Answer:
The new variety formed after cross breeding done by. artificial pollination ‚is called hybrid.

Question 3.
Mention the changes that occur in the body of a male and a female at puberty.
Answer:
Changes that occur in the body of a male

• Appearance of facial hair.
• pitch of the voice changes.
• Pubic hair grow over the reproductive organs.
• broadening of shoulders changes that occur in the body of a female.

Change that occur in the body of a female.

•  breast become bigger
• broadening of hips takes place
• Mensttual cycle starts.
• Pubic hair grow over the reproductive organs.

Question 4.
What do you mean by foetus ?
Answer:
From the beginning of the third month until birth the developing baby is called a. foetus.

Question 5.
What is a Nymph ?
Answer:
The young one that hatches from the fertilized egg is called Nymph.

Question 6.
Name the stages of growth in the life of a human being.
Answer:
Various stage of growth in the life of a human being are:
(a) Infancy
(b) childhood
(c) adolescence
(d) adulthood.

G. Answer in detail.

Question 1.
Why is it important for living organisms to reproduce ?
Answer:
Reproduction is the process by which a living organism is able to produce new individuals of its on kind. This
ability of organisms to reproduce is one of the most basic features of life. Reproduction is important for the existence and continuity of the species.

Question 2.
List the different types of asexual reproduction giving one example of each.
Answer:
Asexual Reproduction :
It is the form of reproduction that involves only one parent organisms. Fusion of an egg and a sperm cell does not occur in it. New organisms formed is exact copy of parent.
Different methods of Asexual reproduction are :

2. Budding: A small out-growth called bud grows into new organism. Example Hydra

3. Spore Formation : Tiny, spherical, unicellular bodies protected by a thick wall called spore develops into new organism. Example Bacteria, fungi.

4. Regeneration : In some organisms, entire body divides in to several parts and each part develops in to new complete organisms. Example – Hydra, Flatworm.

5. Fragmentation : In Spirogyra, the long ribbon like body breaks up in to two or more fragments. These fragments grow into new individuals.

6. Vegetative Propagation : The development of a new plant from the vegetative part like a stem, root or leaf.
(a) stem – Potato (underground stem) Strawberry (Aerial stem)
(b) leaves – Bryophyllum

7. Artificial Propagation – The methods of vegetative propagation adopted by man are called artificial propagation. These are –
(a) Cutting – Example Bougainvillea
(b) Layering – Example lemon, rose
(c) Grafting – Example Mango
(d) Tissue Culture – Example Asparagus, orchids

Question 3.
Explain the process of budding in Hydra.
Answer:
Budding takes place in simple organisms like Hydra. In budding, a small outgrowth called a bud arises on the body of the parent organism. The bud grows and develops into a new organisms and finally gets detached from the parent organism to lead the life of an independent organism. The bud grows and develops into a new organism and finally gets detached from the parent organism to lead the life of an independent organism.

Question 4.
What are the advantages of vegetative propagation?
Answer:
advantages of vegetative propagation –

• The plants produced by vegetative propagation bear flowers and fruits earlier than the plants produced from seeds.
• It is a faster method of growing plants than growing from seeds.
• It is extremely useful for production of seedless plants like banana, grapes and sugarcane.
• The plants produced are exactly the same as the parent plant.
• Most plants are able to survive in unfavourable conditions.

Question 5.
How is artificial pollination carried out ?
Answer:
Artificial pollination is performed to produce a new variety of a crop plant with certain required characteristics. In this process two different varieties of a crop plant (each possessing some wanted characteristics) are selected. One variety of a crop plant may be high- yielding (higher seed producing) and the other variety may be disease-resistant (resistant to diseases). After selection of the parent plants, cross-breeding is done by artificial pollination to have a variety of crop which has characteristics of both the parent varieties. This is called hybridization. The new variety fomied is called a hybrid.

Many hybrid high-yielding varieties of wheat, rice and maize have been produced by the process of hybridization. In artificial pollination during hybridization, the stamens of a bisexual flower are removed before their anthers mature.
↓
This flower with gynoecium intact, is covered with a paper or a muslin bag to prevent natural pollination.
↓
When the stigma of this flower matures, pollen grains from another selected plant are taken and deposited on the stigma.
↓
The seeds produced after artificial pollination give rise to new hybrid variety which is generally better than the parent crops.
↓
They are high-yielding, of better quality and disease-resistant.

Question 6.
Explain the events taking place during fertilization in flowering plants.
Answer:
Once a pollen grain reaches the stigma, it begins to grow a pollen tube. The pollen tube grows down through the style to the ovary. A male gamete or male sex cell travels down each pollen tube and joins with the egg cell or a female gamete inside an ovule. The fusion of the male gamete with the female gamete is called fertilization.

Question 7.
Explain the life cycle of a butterfly.
Answer:
In insects, such butterflies, fertilized eggs are laid. A caterpillar hatches out from an egg. The caterpillar looks more like a worm than like a butterfly. A Caterpillar of a butterfly is called the larva. A larva eats a large quantity of leaves and grows larger until its skin bursts. A new and larger caterpillar comes out and continues to eat and grow. The process of casting off the old skin while growing is called moulting. The caterpillar then produces an outer covering called a cocoon around itself.

Inside the cocoon, the organism begins the next stage of its life cycle, called the pupa. Sometimes the pupa is called a resting stage but it is not a time of rest. There are many changes which take place inside the cocoon. Within the cocoon, the tissues of the larva reorganize to form the butterfly. Finally the cocoon breaks open and the adult butterfly comes out.

Question 8.
Explain the process of development of a zygote into a foetus.
Answer:
The process of formation of an individual from the basic unit of life, that is, zygote (in plants it is a seed or any body part) is called development. In humans the zygote after reaching the uterus begins to divide to form many more cells and becomes a ball of cells. This gets attached to the wall of the uterus for further development. The time between fertilization and birth is called pregnancy, which lasts for around 280 days or 9 months.

From the third week of development till the end of the second month the developing organism is called an embryo. The embryo is attached to the uterus by a special structure called placenta. Through the placenta, materials like nutrients and oxygen pass from the mother to the embryo but the blood of the mother and embryo do not mix.

Carbon dioxide and other wastes from the embryo pass to the mother’s blood through the placenta. The embryo is connected to the placenta through a cordlike structure called the umbilical cord. The embryo is surrounded by a sac-like membrane called amnion and it is filled with a fluid called amniotic fluid. This acts like a cushion and protects the growing embryo. The ball of cells undergoes many cell divisions.

The cells change their size, shape and turn into particular types of cells performing specific functions, such as nerve cells and blood cells. This is called cell differentiation. From these differentiated cells, tissues and organs develope which get organized and finally develop to form a new individual. From the beginning of the third month until birth the developing baby is called a foetus.

Question 9.
Briefly explain the changes which take place during infancy, childhood and adulthood.
Answer:
Infancy – The beginning of the second stage of growth called infancy starts as soon as a child is born. Infancy starts from birth and lasts till about the child becomes two years old. During this period babies grow rapidly. They learn to sit, stand, recognize people and things around them.

Childhood – Childhood lasts for about ten years – from about 2 years to 12 years of age. Physical changes take place during childhood. You grow in size at a slow and steady rate. You continue to grow intellectually, emotionally and socially.

Adolescence – Adolescence most often starts from the age of 10 years and last till age of around 18 years. During adolescence the body grows very quickly and changes in many ways. This is the period when lot of emotional, physical and mental development is taking place. This is because many hormonal changes taking place in the body during this period. In females at the age of 10-11 years and in males at the age of 13-14 years/the reproductive organs become functional.

Adulthood – When are you really an adult ? There is no sign that shows that a person has-reached adulthood. You might look like an adult as adolescent growth ends. At that time, one would have reached Hill height with all body systems folly formed. But emotionally, intellectually and socially one keeps on growing. One takes many important decisions about where to work, live, how to spend money and how to raise a family.
One keeps growing and changing during adulthood.

Living Science Biology Class 8 ICSE Solutions