Extra 20 important long questions and answers from the chapter:6 "Reproduction in Animals" for Class 8 Science CBSE:-
1. What is reproduction? Explain its types.
Ans: Reproduction is the biological process by which organisms produce offspring for species continuation. It is of two types:
Asexual reproduction
– Involves a single parent and does not require gamete fusion (e.g., Hydra, Amoeba).
Sexual reproduction
– Involves two parents and the fusion of gametes (e.g., humans, cows).
Asexual reproduction is faster and produces identical offspring
, while sexual reproduction results in variation.
Organisms reproduce to maintain their species.
Reproduction can occur through different methods like
binary fission, budding, and fertilization
.
2. Explain the process of sexual reproduction in animals.
Ans: Sexual reproduction involves the fusion of male and female gametes.
The male reproductive system produces
sperms
in the testes.
The female reproductive system produces
eggs (ova)
in the ovaries.
Fertilization
occurs when a sperm fuses with an ovum to form a
zygote
.
The
zygote undergoes cell division
and forms an
embryo
.
The embryo develops further in viviparous animals inside the
uterus
.
In oviparous animals, fertilized eggs develop
outside the mother's body
.
3. What is fertilization? Explain its types with examples.
Ans: Fertilization is the fusion of male and female gametes to form a zygote. It is of two types:
Internal fertilization
– Takes place inside the female’s body (e.g., humans, dogs).
External fertilization
– Takes place outside the female’s body (e.g., fish, frogs).
In internal fertilization, the embryo develops inside the uterus.
In external fertilization, large numbers of eggs and sperms are released in water.
Internal fertilization ensures better survival chances, while external fertilization involves high egg production.
Fertilization leads to the formation of a
zygote
, which develops into an
embryo
.
4. Describe the male reproductive system with its parts and functions.
Ans: The male reproductive system is responsible for producing and transporting sperm. It consists of:
Testes
– Produces sperms and testosterone hormone.
Scrotum
– Holds the testes and maintains a lower temperature.
Vas deferens
– Transports sperms from testes to urethra.
Seminal vesicles & prostate gland
– Secrete fluid to nourish sperms.
Urethra
– A common passage for urine and sperm.
Penis
– Transfers sperm into the female body during reproduction.
5. Explain the female reproductive system with functions of its parts.
Ans: The female reproductive system is responsible for egg production and supporting embryo development. It consists of:
Ovaries
– Produce eggs (ova) and secrete female hormones.
Oviduct (Fallopian tube)
– Site of fertilization; carries egg to uterus.
Uterus
– Supports embryo development during pregnancy.
Cervix
– Opening between uterus and vagina.
Vagina
– Receives sperm during reproduction.
The fertilized egg implants in the uterus and develops into a baby.
6. What are viviparous and oviparous animals? Give examples.
Ans: Animals can reproduce in two ways:
Viviparous animals
give birth to live young (e.g., humans, dogs, cows).
Oviparous animals
lay eggs that hatch outside the body (e.g., birds, frogs, reptiles).
In viviparous animals, the embryo develops inside the mother's body.
In oviparous animals, the eggs are laid and incubated externally.
Viviparous animals provide
direct nourishment
to the baby.
Oviparous animals often produce a
large number of eggs
to ensure survival.
7. What is metamorphosis? Describe it with an example.
Ans: Metamorphosis is a drastic change in body form during development.
It occurs mainly in
amphibians and insects
.
The life cycle of a
frog
includes four stages:
Egg → Tadpole → Developing frog → Adult frog
The
tadpole
stage has gills and a tail, suitable for an aquatic life.
As it grows, it loses its tail and develops lungs.
This transformation allows it to live on land.
Insects like
butterflies
also undergo metamorphosis, where a larva turns into an adult.
8. What is the function of the placenta?
Ans: The placenta is an organ that connects the fetus to the mother.
It is a disc-shaped structure that develops in the uterus.
It supplies
oxygen and nutrients
from the mother’s blood.
It removes
waste products
from the
fetal
blood.
It produces hormones necessary for pregnancy.
It prevents the mixing of mother’s and baby’s blood.
The umbilical cord connects the
fetus
to the placenta.
9. What are the stages of embryo development in humans?
Ans: The development of a baby inside the mother involves:
Fertilization
– Fusion of sperm and egg forms a zygote.
Cell division
– The zygote divides to form an embryo.
Implantation
– The embryo attaches to the uterus wall.
Growth and differentiation
– Organs start developing.
Fetal
stage
– The embryo is now called a
fetus
.
Birth
– After about
9 months
, the baby is born.
10. What is binary fission? Explain with an example.
Ans: Binary fission is a type of asexual reproduction where one cell divides into two.
It is commonly seen in
Amoeba and bacteria
.
The
nucleus first divides
into two.
The cytoplasm also divides, forming two daughter cells.
Each daughter cell is identical to the parent.
It helps in rapid population growth.
It requires
no gametes
and occurs under
favourable
conditions.
11. What is budding? Explain with an example.
Ans: Budding is a type of asexual reproduction where a new individual develops from a bud.
It occurs in
Hydra and yeast
.
A small bud forms on the parent’s body.
The bud grows and develops tentacles.
Eventually, it detaches from the parent.
The new organism is genetically identical to the parent.
Budding allows fast reproduction in
favourable
conditions.
12. Why is reproduction necessary for survival?
Ans: Reproduction is essential because:
It ensures the
continuation of species
.
It helps in maintaining
biodiversity
.
It allows organisms to
adapt
to changing environments.
It prevents
extinction
of species.
Sexual reproduction introduces
genetic variation
.
Asexual reproduction allows
rapid population growth
.
13. What are the differences between asexual and sexual reproduction?
Ans: The differences between asexual and sexual reproduction are:
|
Feature |
Asexual Reproduction |
Sexual Reproduction |
|---|---|---|
|
Number of Parents |
One |
Two (Male & Female) |
|
Gametes Involved |
No |
Yes (Sperm & Ovum) |
|
Offspring Identical? |
Yes (Clones) |
No (Genetic Variation) |
|
Examples |
Amoeba (Binary Fission), Hydra (Budding) |
Humans, Frogs, Dogs |
|
Speed |
Faster |
Slower |
|
Genetic Variation |
Absent |
Present |
14. How does reproduction occur in birds?
Ans: Birds reproduce sexually through internal fertilization.
Male and female
birds
mate
, and fertilization occurs inside the female's body.
The fertilized egg has a
hard shell for protection
.
The female
lays eggs in a nest
and incubates them.
The
embryo develops inside the egg
, receiving nutrients from the yolk.
After a few days, the chick
hatches
from the egg.
The
mother bird feeds and protects the young
until it can survive on its own.
15. Explain the importance of variation in sexual reproduction.
Ans: Variation in sexual reproduction is important because:
It helps in
adaptation
to changing environments.
It increases the
survival chances of species
.
It leads to
evolution
over generations.
It prevents
genetic disorders
caused by identical genes.
It helps species
become resistant to diseases
.
Variation ensures
diversity in living organisms
.
16. Describe the life cycle of a frog.
Ans: The life cycle of a frog includes four stages:
Egg Stage
– The female lays eggs in water.
Tadpole Stage
– The egg hatches into a tadpole with gills for breathing.
Metamorphosis
– The tadpole develops legs, lungs, and loses its tail.
Adult Stage
– The
fully grown
frog can live on land and water.
The life cycle takes about
12 to 16 weeks
.
This process is an example of
complete metamorphosis
.
17. What is the role of hormones in reproduction?
Ans: Hormones play a key role in controlling reproductive functions.
Testosterone
(Male hormone) – Controls sperm production and secondary sexual characteristics in males.
Oestrogen
(Female hormone) – Controls egg production and secondary sexual characteristics in females.
Progesterone
– Helps in maintaining pregnancy.
FSH (Follicle-Stimulating Hormone)
– Stimulates egg and sperm production.
LH (Luteinizing Hormone)
– Triggers ovulation in females.
Hormones regulate
puberty, menstrual cycle, and reproduction
.
18. What is cloning? How is it different from natural reproduction?
Ans: Cloning is the process of creating genetically identical copies of an organism artificially.
It is a form of
asexual reproduction
.
Cloning can be done through
artificial methods like nuclear transfer
.
Dolly the sheep
was the first cloned mammal.
Unlike natural reproduction, cloning does not involve
gamete fusion
.
Cloning produces
identical organisms
, while natural reproduction creates genetic diversity.
Cloning is useful in
medicine and agriculture
, but it has ethical concerns.
19. How does the menstrual cycle work in females?
Ans: The menstrual cycle is a 28-day cycle that prepares the female body for pregnancy.
Day 1-5:
Menstruation – The uterus sheds its lining if fertilization doesn’t occur.
Day 6-13:
Egg matures in the ovary under the influence of hormones.
Day 14:
Ovulation – A mature egg is released from the ovary.
Day 15-28:
If fertilization occurs, the uterus supports the embryo. Otherwise, the cycle repeats.
Hormones
oestrogen
and progesterone
regulate this cycle.
If pregnancy occurs, menstruation
stops
until birth.
20. What are test-tube babies? How are they formed?
Ans: Test-tube babies are babies born through In-Vitro Fertilization (IVF).
IVF is a method of artificial fertilization
.
The
sperm and egg are fertilized outside the body
in a lab.
The resulting
zygote is placed into the mother's uterus
.
This method helps couples who cannot conceive naturally.
The first test-tube baby was
Louise Brown, born in 1978
.
IVF is an important advancement in
medical science and fertility treatment
.
