Important Questions Class 8 Science Chapter 9

Important Questions Class 8 Science Chapter 9 – Reproduction in Animals

 Science Chapter 9 of Class 8 is about reproduction in animals. This chapter is about learning the different modes of reproduction, like sexual reproduction and asexual reproduction. In the sexual reproduction part, the students will learn about the male reproductive organs, female reproductive organs, and fertilisation. In the asexual reproduction part, the students will learn about budding and binary fission.

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Important Questions Class 8 Science Chapter 9 – With Solutions

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 Given  below are a set of few questions and their answers from our question bank of Important Questions Class 8 Science Chapter 9. Students after solving these questions will also get to revise the entire chapter.

Question 1. Sets of reproductive terms are given below. Choose the set that has an incorrect combination.

• sperm, testis, sperm duct, penis 

•  menstruation, egg, oviduct, uterus 

• sperm, oviduct, egg, uterus 

•  ovulation, egg, oviduct, uterus

Answer 1.

1. C) Sperm → oviduct, egg → uterus

Reproduction is a process in which organisms make more organisms similar to themselves. Millions of these sperm are in this small amount of semen, and they swim up from the vagina through the cervix following the uterus to meet the egg present in the fallopian tube. It takes sperm to fertilise the egg.

• Around 5 to 6 days after the sperm fertilises the egg, the fertilised egg becomes a multicelled blastocyst.
• A blastocyst is the size of a pinhead, a hollow ball of cells with fluid inside. The blastocyst burrows itself into the uterus lining, called the endometrium.
• The oestrogen hormone causes the endometrium to become thick and rich in blood.
• Progesterone hormone, released by each of the ovaries, keeps the endometrium thick with blood through which the blastocyst may attach to the uterus and absorb nutrients.
• This process is called implantation.

Question 2. Explain the embryo’s future development after it gets embedded in the uterus.

Answer 2.

The developing embryo gets embedded in the uterus wall for further development. The embryo continues to develop inside the uterus. It eventually develops body parts such as hands, legs, eyes, head, ears etc. The stage of an embryo in which all the parts of the body can be identified is known as a foetus. When the development of the foetus is completed, the mother gives birth to the baby.

Question 3. How is reproduction in hydra different from that in Amoeba?

Answer 3.

Amoeba is a unicellular organism that can change its shape. It is generally found in water bodies like ponds, lakes and slow-moving rivers.

Binary fission in Amoeba

• Initially, the pseudopodia are retrieved. The body of an amoeba is coiled and becomes round.
• Amitosis is observed, and the nucleus’s division occurs, followed by the cytoplasm’s splitting.
• Constriction starts to develop at the point of fission in the amoeba body.
• The furrow or constriction turns deeper, resulting in the formation of two daughter cells.

Budding in Hydra

• Hydra is a freshwater organism, having different species.
• Hydra uses regenerative cells for reproduction, where a bud expands as an outgrowth because of repeated cell division at one specific location.
• These buds then develop into new small individuals who, when completely matured, detach from the parent body.

Question 4. Define asexual reproduction. Explain one method of asexual reproduction in animals.

Answer 4.

The continuity of generation in society is a common process. Everyone wants to see the next generation. This process is termed reproduction. The process through which organisms give birth to young, new organisms of the same kind is known as reproduction. There are two main types of reproduction. Sexual and asexual are two types of reproduction. This article will read about asexual reproduction.

Asexual reproduction is the mode of reproduction involved in producing offspring by a single parent. Asexual reproduction is the mode of reproduction in which a single parent produces new offspring. The new individuals produced are physically and genetically identical to each other.

Features

The following are the important features of asexual reproduction:

• A single parent is involved.
• This process of reproduction occurs in a short time.
• No fertilisation or gamete formation takes place.
• The offspring is genetically similar.
• The organisms multiply and grow rapidly.

Types of asexual reproduction

There are various types of asexual reproduction:

• Binary Fission
• Fragmentation
• Vegetative Propagation
• Budding
• Sporogenesis

Binary fission

The term “fission” indicates “to divide”. Through binary fission, the parent cell gets divided into two cells. The cell division patterns vary in various organisms, i.e., some are directional while others are non-directional.

Example: Amoeba and euglena show binary fission.

It is one of the most simplest and uncomplicated methods of asexual reproduction. The parent cell gets divided into two, each daughter cell containing a nucleus of its own that is genetically identical to its parent. The cytoplasm also takes part in division, leading to two equal-sized genetically identical daughter cells. The process repeats itself, and these daughter cells grow and further divide.

Question 5. The hen is odd in the list of animals given below. (human beings, cows, dogs, hens). The reason for it is 

• it undergoes internal fertilisation. 

• It is oviparous. 

•  It is viviparous. 

•  It undergoes external fertilisation.

Answer 5.

1. B) It is oviparous

Here, the hen is the odd one out because it is oviparous, i.e. it lays an egg from which young ones are hatched later. Viviparous animals undergo internal fertilisation, and the embryo develops inside the mother until a young one is born. The ovoviviparous animals produce eggs, but the eggs develop inside the mother, and a live organism is born. However, unlike viviparous animals, ovoviviparous animals do not have a placenta. Ovoviviparous animals are born alive.

• Examples of oviparous are birds and reptiles.
• Examples of viviparous species are snakes and sharks.

Question 6. Although two cells called gametes fuse, the product formed is a single cell called the zygote. Justify.

Answer 6.

During the process of fertilisation, the sperm gets fused with the egg cell. The content of the sperm cell gets transferred into the egg to form the zygote. Hence, the product formed is a single-celled zygote. A zygote is the first diploid cell formed by the fusion of female and male gametes resulting in the formation of an embryo.

The zygote rapidly divides in the initial 12-24 hours of formation.

The cell mass forms a hollow ball during the process of blastulation.

Cells start differentiating and forming cavities.

The three germ layers form during gastrulation.

Formation of primitive streak is followed by notochord formation

Tubes get formed, making a neurula.

The notochord forms into the neural plate.

The neural plate folds to form a neural tube and crest.

The mesoderm gets divided into axial, paraxial, intermediate and lateral plate mesoderm, which gives rise to different organs.

 Question 7. Why do only male gametes have a tail?

Answer 7.

Male gametes or sperms are motile. The tail of the sperm helps the sperm swim through the female’s reproductive tract to reach the oviduct. The male gametes, i.e., sperms, are produced within the male reproductive system. Sperms are small unicellular structures with a head, middle piece, and tail.

• The tip of the sperm head is a portion called the acrosome that enables the sperm to penetrate the egg.
• The midpiece has the mitochondria that supply the energy the tail needs to move and swim.
• The tail moves in whip-like movements back and forth to propel the sperm toward the egg.

Question 8. How can we say that fish exhibit external fertilisation?

Answer 8.

External fertilisation in fish:

1. External fertilisation is the process where the fusion of male and female gametes occurs in the outside environment.
2. The female fish lays its eggs in the surrounding water environment, and the male sperm travels towards the egg randomly in the water.
3. The nucleus of sperm moves into the egg and fuses with it.
4. Due to water as the external environment, the female eggs do not dry out in case of external fertilisation.
5. Since fertilisation occurs in water, outside the female body, it is external fertilisation.
6. Hence,  we can say that fish exhibit external fertilisation.

 Question 9. In which female reproductive organ does the embryo get embedded?

Answer 9.

The embryo gets embedded in the uterus of the female reproductive system. The female reproductive organ is where the embryo gets embedded in the uterus wall. It is here that the embryo continues its development.

Question 10. What is the uterus?

Answer 10.

The uterus is a hollow muscular structure seen in the pelvic region of females between the rectum and the bladder. The uterus’s main function is to nourish the developing foetus until birth.

Process

Over the gestation period which is 9 months in humans, the embryo develops its body parts such as hands, ears, eyes, nose, legs, etc. There is an embryonic stage wherein all body parts can be distinguished, and the embryo has then termed the foetus.

Question 11. Aquatic animals where fertilisation occurs in water are said to be: 

• Viviparous without fertilisation. 

• Oviparous with external fertilisation. 

•  Ovoviviparous with internal fertilisation. 

•  Oviparous with internal fertilisation.

Answer 11.

1. b) oviparous with external fertilisation.

Fertilisation that occurs on the outside of the body of an organism is known as external fertilisation. It normally requires a water body for successful fertilisation.

• It results in increased genetic variations.
• It produces a larger number of offspring.
• The gametes released can drift, making it easy to find mates.

Frogs

The female releases its eggs in the water. The male also releases the sperm in the water for fertilising them. The larval life of frogs is in water, whereas the adult life is on land.

Question 12. The eggs of frogs do not have shells for protection, yet they are safe in the water. How?

Answer 12. 

Frog’s eggs are present without any external covering or shell, but a layer of jelly holds the eggs together, thus providing them protection. This jelly or thick covering also protects them from drying up and prevents them from being eaten by other predators or animals.

• In a female frog, the pair of ovaries produce an ovum and pass it to the oviduct, which opens into the cloaca. The cloaca is a common pathway for the process of excretion and reproduction. At a time, 2500 to 3000 eggs are laid and fertilised externally.

Question 13. Hens and frogs are both oviparous exhibiting different types of fertilisation. Explain.

Answer 13.

Hens are oviparous in nature, in which internal fertilisation takes place. The fertilised egg develops into an embryo inside the body. Frogs are oviparous, in which fertilisation and development of zygote to the embryo and young ones occur outside the body.

• Internal fertilisation occurs in hens. The fertilised egg is enclosed in a protective shell covering the hen’s body and is laid outside for development.
• In frogs, fertilisation and development of zygotes occur outside their body, that is, external fertilisation.

Question 14. The term metamorphosis is not used while describing human development. Why?

Answer 14.

In human beings, the body parts of an adult are present from the time of birth. In the metamorphosis process, the parts of the adult are different from those at the time of birth. Metamorphosis does not occur in humans and other viviparous animals because their offspring are entirely formed inside their mother’s womb. They do not require any further differentiation of their body parts. However, the body parts grow and develop to reach maturity after birth.

Question 15. Explain the importance of reproduction in living organisms.

Answer 15.

Reproduction is the process of producing or giving birth to an offspring. There are generally two forms of reproduction – Asexual and sexual reproduction.

 Here are some points highlighting the importance of reproducing in living organisms:

1. It’s very critical for any species to reproduce to continue their species. Else that species would become extinct.
2. Reproduction plays a crucial role in organisms evolution as it creates small variations via genetic recombinations over generations.
3. Having a healthy balance is very important for any ecosystem. Reproduction helps to increase the number of species ensuring a good ecosystem balance. 

Question 16. Which of the following statements about reproduction in humans is correct? 

• Fertilisation takes place externally. 

•  Fertilisation takes place in the testes. 

•  During fertilisation, the egg moves towards the sperm. 

•  Fertilisation takes place in the human female.

Answer 16.

1. D) Fertilisation takes place in the human female (oviduct).

The female reproductive system is framed in such a way to perform different functions. It makes egg cells that are essential for reproduction, called ova. The system is organised for delivering the ova to the region of fertilisation. The egg fertilisation takes place in the fallopian tubes along with the sperm. Implanting in the uterus’s walls and initiating the pregnancy stages is the next step for fertilised eggs. Once sperm enter the vagina, they can move through the cervix, into the uterus, and to the end of a fallopian tube. If sperm can fuse with an egg, fertilisation takes place.

Question 17. A mother gives birth to a baby, but the baby has the characteristics of both parents. How is this possible?

Answer 17.

Though the mother gives rise to a baby, fertilisation involves the fusion of gametes from both parents. Hence, the character is obtained by both parents. The zygote, therefore, has both father’s and mother’s contributions. Since the zygote develops into the baby, it has the characteristics of both parents.

• The term used for describing the fusion of the female and male gametes is fertilisation.
• Fertilisation can also be described as the fusion of the male gametes with the female gametes to form a diploid zygote.
• It is a process that occurs after the process of pollination of the carpel. The complete sequence of the process takes place in the zygote to develop into a seed.

Question 18. In markets, birds’ eggs are available but never dogs’ eggs. Why?

Answer 18.

Dogs are viviparous. Dogs do not lay eggs, and it gives birth to puppies. Hence, dog eggs are not available in the market. Birds lay their eggs, Birds are oviparous, hence, their eggs are easily available in the market,

• Oviparity refers to a mode of reproduction in which animals lay eggs. These eggs are released into the external environment. Thus, these embryos develop on the outside of the mother’s body. Here, egg yolk nourishes the developing embryo.
• Viviparity refers to the mode of reproduction through which animals directly give birth to their young ones. Therefore, viviparous animals give birth to their young ones without laying eggs. Fertilisation takes place internally inside the female organism.

Question 19. What is metamorphosis? Give examples.

Answer 19.

In many living species, the young one or the offspring does not resemble the adult. This is known as indirect development and such a young one is known as a larva or nymph. The process of changing from a nymph or larva to an adult body is known as metamorphosis. This transformation of a larva or nymph into an adult is characterised by a series of morphological, behavioural and physiological changes.

Examples include frogs, butterflies, etc.

20. State two differences between a zygote and a foetus.

Answer 20:

Zygote:

• It is the earliest stage of development
• It is a single cell
• It is formed by the fusion of male and female gametes
• The zygote usually lasts a week and then develops into its next stage.
• The zygote gets divided several times to form an embryo

Foetus

• It is the last developmental stage of an organism
• The embryo stage shows all a mature organism’s main recognizable body parts.
• The foetus stage usually occurs after the embryo stage.
• Foetus mainly undergoes internal development.

Question 20. Differentiate between internal fertilisation and external fertilisation.

Answer 20.

Fertilisation is generally defined as the fusion of a male and a female gamete.

Internal fertilisation occurs inside the female body.

There are higher chances of survival of the offspring.

Internal fertilisation protects fertilised eggs or embryos from harsh environments.

Examples are cows, humans, dogs, monkeys, etc.

External fertilisation

It occurs on the outside of the female body.

There are low chances of survival of the offspring.

Most aquatic animals use this type of fertilisation, and the advantage of external fertilisation is that it produces many offspring due to external hazards. Examples are fish, frogs, organisms etc.

Question 21. Reproduction by budding takes place in 

•  Hydra 

•  paramecium 

•  amoeba 

•  Bacteria

Answer 21.

1. a) Hydra

Reproduction in all the given organisms takes place through asexual methods. Hydra reproduces by forming buds on its body surface, which develops into a new organism. Amoeba, paramecium and bacteria multiply by dividing themselves into two parts, i.e. by binary fission method. Budding is an asexual mode of producing new organisms. In this process, an organism is developed from a small part of the parent’s body.

• Hydra uses regenerative cells for reproduction, where a bud expands as an outgrowth because of repeated cell division at one specific location.
• These buds then develop into new small individuals who, when completely matured, detach from the parent body.

Benefits of Solving Important Questions Class 8 Science Chapter 9

Students must first read through the entire chapter to understand the new themes presented in the  chapter. It also helps to identify the crucial concepts necessary from an examination point of view. 

Regularly solving questions will further enhance the exam preparation for any student. Students can rely on Extramarks question bank of Class 8 Science Chapter 9 Important Questions to get a full set of questions from different sources at  one place. The question bank comes with simplified and clear answers to each question. The list of questionnaires cover the entire chapter. All the questions covered in our question bank are quite important and expected  in the exams.

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• Students will receive a fair idea about the important topics they must study for their examinations. By solving these questions they would be able to understand their weak areas. Based on it they can properly revise these areas and become stronger with overall  concepts of the chapter. 
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• The questions and answers are based on the latest CBSE syllabus and as per CBSE guidelines. So students can rely on them completely. . So we recommend students to refer to our Science Class 8 Chapter 9 Important Questions during their exams and come out with flying colours.  .

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