A science teacher asked students to imagine a world where plants and animals do not produce any new individuals. The students quickly realised that as the older organisms die, the number of living organisms will keep decreasing. The teacher then introduced the term reproduction and explained that it is the process by which living organisms produce new individuals of their own kind. The class also discussed that reproduction can take place in different ways in different organisms.

1. (a) What is reproduction?
2. (b) Why is reproduction important for a species?
3. (c) If reproduction stops in a species, what will happen after some time?
4. (d) Name the two main modes of reproduction in animals.

1. Reproduction is the biological process by which living organisms produce new individuals of their own kind.
2. It is important to maintain the continuity of a species and prevent its extinction.
3. The number of individuals in that species will go on decreasing and the species will eventually become extinct.
4. Sexual reproduction and asexual reproduction.

In a group activity, students collected pictures of different animals. They found that dogs, cats, cows and humans give birth to young ones, whereas hens, frogs and fish lay eggs. Their teacher told them that animals like sponge, hydra and amoeba can also form new individuals from a single parent. The class concluded that there are different modes of reproduction in animals depending on their body structure and habitat.

1. (a) What type of reproduction is seen in humans and cows?
2. (b) What type of reproduction is seen in Amoeba and Hydra?
3. (c) Name one egg-laying animal and one animal which gives birth to young ones.
4. (d) Why do different animals show different modes of reproduction?

1. Sexual reproduction.
2. Asexual reproduction.
3. Egg-laying: hen or frog; gives birth to young ones: cow or human.
4. Because their body structure, complexity and habitat are different, so the methods best suited for their survival also differ.

During a science lesson, a labelled diagram of the human male reproductive system was shown to the class. The teacher pointed out the testes, sperm ducts, urethra and penis. She explained that testes are located in the scrotum and produce male gametes called sperms. Sperms travel through the sperm ducts and finally pass out through the urethra. The students were told that each sperm is a microscopic cell having a head, middle piece and a tail.

1. (a) Name the primary reproductive organs in males.
2. (b) What is the function of the testes?
3. (c) Which tube carries sperms to the outside of the body?
4. (d) Why do sperms have a tail?

1. The testes.
2. They produce male gametes called sperms and secrete male hormones.
3. The urethra (through the sperm ducts and penis).
4. The tail helps the sperm to swim towards the ovum in the female reproductive tract.

Riya observed a diagram of a sperm in her textbook. She noticed that the head of a sperm contains a nucleus, the middle piece is packed with energy-giving structures, and the tail is long and thin. Her teacher explained that sperms are motile cells and many sperms are released together. Only one of them usually succeeds in fusing with the ovum during fertilisation.

1. (a) Which part of a sperm contains the father’s genetic material?
2. (b) Why does the middle piece of a sperm have many energy-giving structures?
3. (c) What is meant by “sperms are motile”?
4. (d) How many sperms generally fuse with one ovum during fertilisation?

1. The head of the sperm contains the nucleus with the father’s genetic material.
2. To provide energy needed for the movement of the sperm.
3. It means sperms can move on their own using their tail.
4. Usually only one sperm fuses with one ovum.

A diagram of the human female reproductive system was displayed in class. The teacher marked the ovaries, oviducts (fallopian tubes), uterus and vagina. She explained that the ovaries produce ova (eggs), the oviducts carry the ovum, and the uterus is the place where the embryo gets attached and grows. The vagina acts as the passage for sperms to enter and the birth canal during childbirth.

1. (a) Name the organ where the embryo develops.
2. (b) What are the functions of the ovaries?
3. (c) In which part of the female reproductive system does fertilisation usually take place?
4. (d) Why is the vagina called the birth canal?

1. The uterus.
2. They produce ova (eggs) and secrete female hormones.
3. In the oviduct (fallopian tube).
4. Because the baby passes through the vagina to come out of the mother’s body during childbirth.

Once in about 28 days, one ovum is released from an ovary in a human female. After its release, the ovum enters the oviduct and slowly moves towards the uterus. If a sperm is present in the oviduct, fertilisation may occur. If no fertilisation takes place, the ovum dies after a short time and is removed from the body along with the soft lining of the uterus.

1. (a) From which organ is the ovum released?
2. (b) Through which part does the ovum travel towards the uterus?
3. (c) What happens to the ovum if a sperm fuses with it?
4. (d) What happens to the ovum if it is not fertilised?

1. From the ovary.
2. Through the oviduct (fallopian tube).
3. It gets fertilised to form a zygote.
4. It dies and is removed from the body along with the uterine lining.

During reproduction in humans, millions of sperms are released inside the female body. The sperms travel through the uterus and reach the oviduct. If an ovum is present there, one of the sperms may fuse with it. The fusion of the nucleus of the sperm with the nucleus of the ovum is called fertilisation. The fertilised egg is called a zygote. Because this process occurs inside the female body, it is known as internal fertilisation.

1. (a) What is fertilisation?
2. (b) What is the name of the cell formed after fertilisation?
3. (c) Why is fertilisation in humans called internal fertilisation?
4. (d) Where does fertilisation usually occur in humans?

1. Fertilisation is the fusion of the male gamete (sperm) and the female gamete (ovum).
2. A zygote.
3. Because it takes place inside the body of the female.
4. In the oviduct (fallopian tube).

In frogs, fertilisation occurs outside the body of the female. The female frog lays a large number of eggs in water. The male frog releases sperms over the eggs. Both eggs and sperms meet in water and fusion of gametes takes place there. This type of fertilisation is called external fertilisation. To increase the chances of fertilisation, a large number of eggs and sperms are released.

1. (a) What do you mean by external fertilisation?
2. (b) Where does fertilisation occur in frogs?
3. (c) Why do frogs release a large number of eggs and sperms?
4. (d) Name one more animal that shows external fertilisation.

1. Fertilisation that takes place outside the body of the female.
2. In water, outside the body of the frog.
3. Because many eggs and sperms are destroyed or do not meet, so more gametes increase the chances of fertilisation.
4. Many fish show external fertilisation.

After fertilisation, the zygote formed in the oviduct begins to divide repeatedly. It forms a ball of many cells and gradually moves towards the uterus. This developing stage is called the embryo. The embryo gets attached to the soft lining of the uterus and starts growing there. The uterus provides protection and nourishment to the developing embryo.

1. (a) What is the zygote?
2. (b) What name is given to the zygote after it divides to form many cells?
3. (c) Where does the embryo get attached in the female body?
4. (d) Why is the uterus a suitable place for the development of the embryo?

1. The zygote is the single cell formed after fertilisation.
2. Embryo.
3. To the soft lining of the uterus.
4. Because it has thick, soft walls with rich blood supply that give protection and nourishment.

As the embryo grows, it develops body parts such as head, hands, legs and eyes. At this stage it is called a foetus. The foetus is connected to the mother through a special structure called the placenta. Through the placenta, the foetus receives oxygen and nutrients from the mother and sends waste products back to the mother’s blood for removal.

1. (a) When is the developing baby called a foetus?
2. (b) What is the function of the placenta?
3. (c) How does the foetus receive nourishment?
4. (d) How are the wastes from the foetus removed?

1. When the body parts like hands, legs, head and eyes become visible.
2. It allows the exchange of nutrients, oxygen and waste products between mother and foetus.
3. Nutrients and oxygen pass from the mother’s blood to the foetus through the placenta and umbilical cord.
4. Waste products from the foetus pass into the mother’s blood through the placenta and are removed by the mother’s body.

In a farm, hens lay eggs in nests. The farmer collects the eggs and keeps some of them for hatching. After warm conditions are provided for some days, chicks come out of the eggs. In the same farm, frogs in a nearby pond lay eggs in water and their eggs hatch into tadpoles. In both cases, the animals lay eggs from which young ones come out.

1. (a) What term is used for animals that lay eggs?
2. (b) Name two oviparous animals from the passage.
3. (c) Where does the embryo develop in these animals?
4. (d) Why do these animals lay many eggs at a time?

1. Oviparous animals.
2. Hen and frog.
3. Inside the egg.
4. Because many eggs may be destroyed or eaten, so laying more eggs increases the chances of survival of some young ones.

In a village, a cow gave birth to a calf. The cow fed the calf with her milk and stayed close to it to protect it. Similarly, a pet dog gave birth to puppies, and the owner arranged a warm place and proper food for the mother and puppies. In both these cases, the young ones were born directly from the mother’s body and did not hatch from eggs laid outside.

1. (a) What term is used for animals that give birth to young ones?
2. (b) Name two viviparous animals from the passage.
3. (c) Where does the embryo develop in viviparous animals?
4. (d) How does parental care help the survival of young ones in viviparous animals?

1. Viviparous animals.
2. Cow and dog.
3. Inside the mother’s uterus (body).
4. Parents give food, protection and warmth to the young ones, so their chances of survival increase.

Students watched an animation showing the life cycle of a frog. First, they saw eggs laid in water. These eggs hatched into tadpoles, which had tails and gills and lived only in water. Gradually, the tadpoles developed legs, their tails became shorter and lungs developed. Finally, they turned into adult frogs that could live both in water and on land. The teacher said that this drastic change is called metamorphosis.

1. (a) Name the larval stage of a frog.
2. (b) How does a tadpole breathe?
3. (c) What changes occur in a tadpole during metamorphosis?
4. (d) Why is the adult frog called an amphibian?

1. Tadpole.
2. It breathes through gills.
3. Legs appear, the tail becomes shorter and disappears, and lungs develop for breathing air.
4. Because it can live both in water and on land.

A frog’s eggs are laid in water and float in clusters. The jelly around the eggs protects them from injury and drying. The tadpoles swim freely and feed on small plants in the water. As they change into adult frogs, they develop strong hind limbs and lungs. Adult frogs can jump on land and also swim in water. Their moist skin helps them to breathe when in water.

1. (a) How are frog eggs protected in water?
2. (b) What do tadpoles feed on?
3. (c) Name two adaptations of adult frogs for life on land.
4. (d) How does the skin of frog help in respiration?

1. They are covered with a jelly-like substance which protects them.
2. On small plants and plant parts in water.
3. Strong hind limbs for jumping and lungs for breathing air.
4. The moist skin allows exchange of gases when the frog is in water.

Under a microscope, a student observed a slide of Amoeba. The teacher explained that Amoeba reproduces by binary fission. First, the nucleus of Amoeba divides into two. Then the cytoplasm also divides to form two daughter cells. Each daughter Amoeba receives one nucleus and some cytoplasm and grows to full size. In this way, a single parent gives rise to two new individuals.

1. (a) What type of reproduction is shown by Amoeba?
2. (b) What happens to the nucleus during binary fission?
3. (c) How many daughter cells are formed from one parent Amoeba in binary fission?
4. (d) Why are the daughter Amoebae identical to each other?

1. Asexual reproduction by binary fission.
2. The nucleus divides into two nuclei.
3. Two daughter cells.
4. Because they are formed from the same parent cell without mixing of genetic material from another organism.

In an aquarium, students noticed small outgrowths on the bodies of some Hydra. Their teacher informed them that Hydra reproduces asexually by budding. A small bud appears on the parent body due to repeated cell division. The bud grows and develops tentacles and mouth. Finally, it detaches and becomes a new Hydra. Sometimes, more than one bud may be seen on the same parent at a time.

1. (a) What is the method of asexual reproduction in Hydra?
2. (b) How is a bud formed on the body of Hydra?
3. (c) When does the bud detach from the parent Hydra?
4. (d) Does the parent Hydra remain alive after buds separate? Explain.

1. Budding.
2. By repeated cell division at a particular spot on the parent’s body.
3. When it becomes fully developed and can live independently.
4. Yes, the parent remains alive and can form more buds because only a small part of its body forms each bud.

Yeast is a unicellular fungus used in baking. Under a microscope, students saw that a small bulb-like outgrowth develops on the yeast cell. This outgrowth is called a bud. The nucleus of the parent cell divides and one nucleus moves into the bud. The bud grows and may form more buds. Sometimes a chain of buds is formed. Each bud can separate and live as a new yeast cell.

1. (a) Name the method of asexual reproduction in yeast.
2. (b) What is a bud?
3. (c) How does the nucleus take part in budding in yeast?
4. (d) Why are the new yeast cells called clones of the parent?

1. Budding.
2. A small bulb-like outgrowth formed on the parent yeast cell.
3. The nucleus divides and one of the daughter nuclei enters the bud.
4. Because they are genetically identical to the parent yeast cell.

A worksheet asked Ankit to compare how new individuals are formed in humans, frogs, Amoeba and Hydra. He wrote that humans and frogs both use sexual reproduction, while Amoeba and Hydra reproduce asexually. He also mentioned that humans and frogs produce offspring that may show variations, while Amoeba and Hydra produce offspring which are identical to the parent.

1. (a) Which two organisms in the passage use sexual reproduction?
2. (b) Which two organisms in the passage use asexual reproduction?
3. (c) In which of these will offspring show more variations – humans or Amoeba? Why?
4. (d) Name the methods of asexual reproduction in Amoeba and Hydra.

1. Humans and frogs.
2. Amoeba and Hydra.
3. Humans, because sexual reproduction involves mixing of genetic material from two parents, producing variations.
4. Binary fission in Amoeba and budding in Hydra.

A family noticed that their child had curly hair like the father and dimpled cheeks like the mother. The science teacher explained that such similarities appear because characters are passed from parents to offspring through their gametes. The sperm carries the father’s characters and the ovum carries the mother’s characters. When these gametes fuse, the child inherits traits from both parents.

1. (a) Which cells carry the father’s characters to the child?
2. (b) Which cells carry the mother’s characters to the child?
3. (c) How does the child get traits from both parents?
4. (d) What is the role of fertilisation in inheritance?

1. Sperms.
2. Ova (eggs).
3. Because the nucleus of the sperm and the nucleus of the ovum fuse and combine genetic material from both parents.
4. During fertilisation, the male and female gametes fuse, so the zygote formed carries characters from both parents.

Before the Class 8 Science test, a group of students revised Chapter 9 by solving NCERT examples, diagrams and case-based questions. They focused on key terms like zygote, embryo, foetus, oviparous, viviparous, metamorphosis, binary fission and budding. Their teacher told them that clear understanding of these concepts helps in answering both short questions and case-based questions in the exam.

1. (a) Which chapter were the students revising?
2. (b) Name any four key terms from this chapter mentioned in the passage.
3. (c) How can solving case-based questions help in exams?
4. (d) Name two methods of asexual reproduction included in this chapter.

1. Chapter 9: Reproduction in Animals.
2. Any four of: zygote, embryo, foetus, oviparous, viviparous, metamorphosis, binary fission, budding.
3. They improve reading, understanding and application of concepts, helping to answer higher-order and mixed-type questions.
4. Binary fission and budding.