Science Question Answer (5 Marks)

Differences between internal fertilization and external fertilization:

Internal fertilization	External fertilization
It takes place inside the female body.	It takes place outside the female body.
Example: Human being.	Example: Human being.

1. In frog, external fertilization takes place.
2. In fox, internal fertilization takes place.

The diagram of the human female reproductive system is shown below:

1. In the human body, an egg (or ovum) gets fertilized in the fallopian tubes.
2. The fertilized egg (or zygote) develops into a baby in the uterus of the human body.

Following steps are involved in the process of sexual reproduction in an animal:

1. In the animal, male parent produces male gametes called sperms. Millions of sperms are produced by testes.
2. The female parent produces female gamete called ova (eggs). Like a sperm, an egg is also a single cell.
3. The next step is fertilization. In this step, sperm enters the ovum and fuses with it to form a new cell called zygote. The zygote is the beginning of a new individual.
4. In this step, zygote begins to develop into an embryo. The zygote divides repeatedly to form a large number of cells and ultimately the zygote grows and develops to form a baby.

1. General Name of Animals Like X is Oviparous. Oviparous animals are those which reproduce by laying eggs. The young ones develop inside the eggs.
2. Examples of Animals like X are Frog, Fish and Star Fish etc.
3. General Name of Animals Like Y is Viviparous. Viviparous animals are those animals in which the young ones develop inside the uterus of the mother.
4. Examples of Animals like Y are Human beings, cattle, etc.

In hens, internal fertilization take place but they do not give birth to chicks like human beings. After fertilization, the zygote divides repeatedly to form embryo which travels down the oviduct. As it travels down, many protective layer are formed around it.
The outermost protective layer is hard shell which we can see in a hen’s egg. After the hard shell is formed around the developing embryo, the hen finally lays the egg. The hen, then sits on the egg to provide sufficient warmth to the eggs for the development of the embryo into the chicks. The embryo takes about 3 weeks to develop into a complete chick.

1. The animals which give birth to young one are called viviparous animals. In such animals, the baby develops inside the body of the mother.

Examples of Viviparous animals: Human beings, cat, dog, cow, tiger.

2. The animals that reproduce by laying eggs are called oviparous animals. In such animals, the baby develops inside eggs that the mother lays.

Examples of Oviparous animals: Frog, sparrow, lizard, hen, fish, butterfly.

1. Animal A is Frog and form is Tadpole.
2. The change from Tadpole to Frog is called as Metamorphosis.
3. Since, A is Frog, hence the breathing organ of Frog is Lungs.
4. Since, B is Tadpole. The breating organ of Tadpole is gills.

Internal fertilization: Fertilization which takes place inside the female body is called internal fertilization. Internal fertilization occurs in many animals including humans, cows, dogs and hens.
External fertilization: This type of fertilization in which the fusion of a male and a female gamete takes place outside the body of the female is called external fertilization. It is very common in aquatic animals such as fish, starfish, etc.

Hydra reproduces by budding. In hydra, there may be one or more bulges. These bulges are the developing new individual and they are called buds. This bud then grows gradually to form a small hydra by developing a mouth and tentacles. The tiny new hydra detaches itself from the parent body and become new independent individual.

Amoeba reproduces by common asexual method called binary fission. In this method, Amoeba cell divides into two equal daughter cells. The nucleus of amoeba first divides into two parts. After that the cytoplasm of amoeba divides into two parts, one part around each nucleus. This leads to the formation of the two daughter Amoebae cell having a nucleus and its own cell organelles.