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Q1. Animals that give birth to young ones are called?
Correct Answer: Viviparous
Detailed Explanation:
Animals reproduce in different ways. Some animals lay eggs, while others give birth directly to babies. Animals that give birth to young ones are called viviparous animals.
The word “viviparous” comes from Latin words that mean “live birth.” In these animals, the baby develops inside the mother’s body and receives nourishment from the mother until it is ready to be born.
Humans, cows, dogs, cats, and goats are examples of viviparous animals.
Why is the answer “Viviparous”?
Viviparous animals:
- Give birth directly to babies
- Protect the developing young inside the body
- Provide food and oxygen to the embryo
- Usually take care of the young after birth
Because these animals produce living young ones directly, the correct answer is viviparous.
What are Oviparous Animals?
Oviparous animals are animals that lay eggs.
Examples:
- Hen
- Snake
- Frog
- Fish
- Crocodile
In these animals, the embryo develops inside the egg outside the mother’s body.
Difference Between Viviparous and Oviparous Animals
Viviparous Animals:
- Give birth to babies
- Embryo develops inside the body
- Example: Human, dog
Oviparous Animals:
- Lay eggs
- Embryo develops inside eggs
- Example: Hen, frog
Important NCERT Point
NCERT explains that animals are grouped based on the way they reproduce. Viviparous animals directly produce young ones, while oviparous animals lay eggs.
Real-Life Example
A cow gives birth to a calf directly. Therefore, a cow is a viviparous animal.
A hen lays eggs, so it is oviparous.
Q2. The fusion of male and female gametes is called?
Correct Answer: Fertilization
Detailed Explanation:
In sexual reproduction, two special reproductive cells called gametes combine together.
- Male gamete = Sperm
- Female gamete = Egg (Ovum)
The process in which these two gametes fuse together is called fertilization.
After fertilization:
- A zygote is formed
- The zygote develops into an embryo
- Finally, a new organism is formed
Why is Fertilization Correct?
Fertilization is the joining of:
- Male reproductive cell
- Female reproductive cell
This process starts the development of a new life.
Without fertilization, sexual reproduction cannot occur.
Types of Fertilization
1. Internal Fertilization
When fertilization occurs inside the body of the female.
Examples:
- Humans
- Dogs
- Cows
2. External Fertilization
When fertilization occurs outside the body.
Examples:
- Frogs
- Fish
What is Reproduction?
Reproduction is the complete process by which living organisms produce young ones of their own kind.
Fertilization is only one step of reproduction.
What is Metamorphosis?
Metamorphosis means a sudden change in body form during development.
Examples:
- Caterpillar to butterfly
- Tadpole to frog
What is Budding?
Budding is a type of asexual reproduction where a small bud develops into a new organism.
Example:
- Hydra
- Yeast
Important NCERT Point
NCERT states that fertilization is essential in sexual reproduction because it forms the zygote from which a new organism develops.
Real-Life Example
In humans:
- Sperm from the father
- Egg from the mother
Their fusion forms a zygote, which later develops into a baby.
Q3. In which of the following, budding takes place?
Correct Answer: Hydra
Detailed Explanation:
Budding is a type of asexual reproduction.
In budding:
- A small outgrowth called a bud appears on the parent body
- The bud grows gradually
- It later separates and forms a new individual
Hydra reproduces through budding.
Why is Hydra Correct?
Hydra is a small aquatic organism.
During reproduction:
- A bud forms on its body
- The bud develops mouth and tentacles
- It finally separates into a new Hydra
Thus, Hydra reproduces by budding.
How Budding Happens in Hydra
Step 1:
A small bulge appears on the body.
Step 2:
The bud grows bigger.
Step 3:
Tentacles develop.
Step 4:
The bud separates and becomes independent.
Why Other Options are Wrong
Amoeba
Amoeba reproduces mainly by binary fission.
Paramecium
Paramecium also reproduces through binary fission.
Bacteria
Most bacteria reproduce by simple cell division.
Binary Fission
Binary fission means:
- One organism divides into two equal parts.
Examples:
- Amoeba
- Bacteria
- Paramecium
Important NCERT Point
Hydra and yeast are common examples of budding given in NCERT books.
Real-Life Understanding
If you observe a Hydra under a microscope:
- You can see a tiny bud attached to its body.
- This bud grows into a complete organism.
Q4. External fertilization occurs in?
Correct Answer: Frogs
Detailed Explanation:
External fertilization means fertilization that takes place outside the body of the female.
In frogs:
- Female lays eggs in water
- Male releases sperms over the eggs
- Fertilization occurs in water
Thus, frogs show external fertilization.
Why Frogs are Correct?
Frogs need water for reproduction because:
- Eggs dry quickly on land
- Water helps sperms swim toward eggs
- Fertilization occurs outside the body
Therefore, frogs are examples of external fertilization.
Internal vs External Fertilization
Internal Fertilization
Occurs inside female body.
Examples:
- Humans
- Cow
- Dog
External Fertilization
Occurs outside body.
Examples:
- Frog
- Fish
Why Humans and Cows are Wrong
Humans and cows show internal fertilization.
The sperm and egg fuse inside the female body.
What About Hens?
In hens:
- Fertilization is internal
- Egg development continues later outside the body
So hens are not examples of external fertilization.
Advantages of External Fertilization
- Large number of eggs produced
- Better chances of survival
- Easy mixing of gametes in water
Disadvantages
- Many eggs may be eaten by predators
- Fertilization success may be low
- Young ones receive less protection
Important NCERT Point
NCERT clearly explains that frogs and fishes generally reproduce through external fertilization.
Real-Life Example
During rainy season:
- Frogs gather near ponds
- Females lay eggs
- Males release sperms over them
This is external fertilization.
Q5. The zygote divides repeatedly to give rise to an?
Correct Answer: Embryo
Detailed Explanation:
After fertilization:
- A zygote is formed
- The zygote is a single cell
This zygote starts dividing repeatedly.
These repeated divisions form an embryo.
The embryo later develops into a complete organism.
Formation Process
Step 1:
Fertilization occurs.
Step 2:
A zygote forms.
Step 3:
Zygote divides continuously.
Step 4:
Embryo develops.
Step 5:
Embryo grows into a baby organism.
What is a Zygote?
A zygote is:
- The first cell formed after fertilization
- Formed by fusion of sperm and egg
It contains characteristics from both parents.
What is an Embryo?
An embryo is:
- An early developing stage of an organism
- Formed after repeated cell division of the zygote
Why Other Options are Wrong
Egg
Egg is a female gamete formed before fertilization.
Sperm
Sperm is a male gamete.
Neither develops from the zygote.
Important NCERT Point
NCERT explains:
- Zygote → Embryo → Foetus → Baby
This is the normal developmental sequence in many animals.
Real-Life Example
In humans:
- Fertilization forms a zygote
- The zygote divides many times
- An embryo forms inside the uterus
The embryo gradually develops into a baby.
Additional Important Concepts from This Chapter
Sexual Reproduction
Sexual reproduction involves:
- Two parents
- Male and female gametes
- Fertilization
It helps in producing variation among organisms.
Asexual Reproduction
Asexual reproduction involves:
- Only one parent
- No gamete fusion
- Faster reproduction
Examples:
- Budding in Hydra
- Binary fission in Amoeba
Embryo and Foetus
Embryo
Early stage after zygote division.
Foetus
When body parts become identifiable.
Importance of Reproduction
Reproduction is important because:
- It maintains continuity of species
- Prevents extinction
- Transfers characters from parents to offspring
Metamorphosis in Frogs
Life cycle of frog:
Egg → Tadpole → Adult Frog
The tadpole undergoes body changes called metamorphosis.
Key NCERT Revision Points
- Viviparous animals give birth to babies.
- Oviparous animals lay eggs.
- Fertilization is fusion of gametes.
- Hydra reproduces by budding.
- Frogs show external fertilization.
- Zygote develops into embryo.
Important Learning Points
- Reproduction ensures continuation of life.
- Different animals reproduce differently.
- Fertilization is necessary for sexual reproduction.
- Budding is a simple asexual reproduction method.
- Frogs reproduce in water through external fertilization.
- Embryo formation begins from the zygote.