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Chapter-9 in Exercises

A. Tick (√) the correct option. 1. occurs in which of these animals? a. Dog c. Cow b. Human d. All of these Answer: d. All of these 2. A tadpole develops into an by the process of: a. Fertilization c. metamorphosis b. Binary fission d. budding Answer: c. metamorphosis 3. The number of nuclei in the zygote is: a. None c. one b. Two d. four Answer c. one 4. The female reproductive system includes which of the following structures? a. c. b. d. All of these Answer: d. All of these 5. The gets embedded in the wall of which part of the reproductive system? a. c. Oviducts b. Testes d. Uterus Answer: d. Uterus 6. Which one is not oviparous? a. Bird c. Frog b. Snake d. Horse Answer: d. Horse 7. External fertilization occurs in: a. Frog c. hen b. Cow d. deer Answer:a. Frog 8. Which of the following organism reproduces by budding? a. Hydra c. b. Bacteria d. Sponge Answer: a.Hydra B. State whether the following statements are TRUE or FALSE. 1. The is connected to the embryo by a tubular cord called umbilical cord.True 2. Frog lays in water.True 3. Embryo develops into foetus.True 4. Female parent produces female called .False 5. An ovary releases single every month.False 6. The formation of zygote marks the beginning of a new individual.True 7. Female reproductive system consists of a pair of testes, sperm ducts and a penis.False 8. Binary fission is a mode of asexual reproduction.True C. Fill in the blanks. 1. The period between the fertilization and the birth of the baby is called period or . 2. Each parent produces special reproductive cells called . 3. The gamete produced by male and female isspermand ovum respectively. 4. In most aquatic animals,external fertilization takes place. 5. On reaching the uterus, embryo gets attached to the wall of uterus by placenta. 6. The process of transformation of larva or tadpole into an adult through drastic changes is called metamorphosis. 7. Full form of IVF is in-vitro fertilization. D. Give one word for the following. 1. The organ which produces sperm.Testes 2. The organ which produces egg.Ovaries 3. The place where embryo develops in a female body.Uterus 4. The organ in reproductive system which receives the sperm.Vagina 5. A floating clump of eggs.Frog- 6. A method of asexual reproduction in which individuals develop from the bud.Budding 7. Animals which give birth to their young ones.Viviparous 8. Animals which lay eggs. Oviparous E. Answer the following questions in brief. 1. Define reproduction. Answer: Reproduction is a process by which a living organism produces an offspring (i.e. young ones) of their own kind. 2. What is the significance of reproduction? Answer: Reproduction is an important life process that involves the multiplication of living organisms. It is essential for the continuation of species. Like plants, plants also reproduce to increase in number and continue their race. 3. Why does a show some characteristics of the father and some of the ? Answer: The child inherits the characters of father and mother due to the that are passed on by the parents. 4. What is the function of amniotic fluid? Answer: The uterus is filled with a fluid called amniotic fluid that protects the foetus from jerks and change in temperature. 5. How does an embryo obtain nutrition to grow and develop its body parts? Answer:The placenta is connected to the embryo by a tubular cord called umbilical cord. Blood vessels in the umbilical cord supplies nutrients and oxygen from the mother’s blood to the embryo and take away the waste carbon dioxide and other waste from the embryo to the mother’s blood. 6. Differentiate between viviparous and oviparous animals. Answer: Viviparous animals: Animals which give birth to their young ones are called viviparous animals. Mammals like cow, horse, dog, cat and human beings are viviparous animals. Oviparous animals: Animals which lay eggs are called oviparous animals. Animals such as hen, frog lizard, birds and butterfly are Oviparous animals. 7. What is metamorphosis? Answer: Newly born organisms and newly hatched young ones have a shape and structure similar to their parents. In some animals the newly born offspring is different from the adult ones. It is called larva. The conversion of larva into an adult by undergoing through drastic changes is called metamorphosis. 8. Differentiate between sexual reproduction and asexual reproduction. Answer: Asexual reproduction  The type of reproduction in which only a single parent is involved is called asexual reproduction.  There is no mixing of genetic information.  Examples: lower animals like Amoeba, Hydra, yeast, starfish and worms. Sexual reproduction  The type of reproduction, which involves two parents to give rise to an offspring is called as sexual reproduction.  There is a mixing of genetic information.  Examples: In humans, almost in all mammals and many other multicellular animals. 9. Name the hormones produced by testes and ovaries. Answer: The hormone produced by testes is testosterone and thehormones produced by ovaries are oestrogen and progesterone. F. Answer the following questions in detail. 1. Explain the process of fertilization in human beings. Answer: Sexual reproduction takes place in human beings. Male reproductive organs(testes) produce (male gametes) while the female reproductive organ(ovaries) produce ovum (female gametes). The sperms are ejected inside female bodies where they fuse with ovum and forms zygote (called internal fertilization). The zygote begins to develop into an embryo that attaches to the uterus wall of female. The embryo further multiples into many cells and develops further into a small baby called foetus and later, a baby is born. 2. Describe the structure and functions of different male and female reproductive organs with the help of diagrams. Answer:

The male reproductive organs are a pair of testes, sperm duct, Urethra and Penis.  Testis: Testis is located outside the abdominal cavity within a sac called scrotal sac or scrotum.They produce millions of tiny sperm cells. Testes produce a hormone called testosterone. Testosterone is a male hormone, which maintains the entire reproductive activities that occur in a male.  Vas deferens: They are also known as sperm duct. This duct connects each testis to the urethra. They transport sperms into the penis. They also collect fluids secreted by different glands. These secretions are rich in proteins to enrich the sperms. Sperms along with these secretions form a thick substance called as semen.  Penis: It is a muscular organ which transfers semen into the female reproductive tract.  Urethra: It is a tube-like structure present inside the penis, which receives both urinary tube and sperm duct and serves as a common transporting organ for urine and semen.

Female Reproductive system:

The female reproductive system consists of organs a pair of Ovaries, a pair of oviducts, uterus and vagina. 1.Ovary: Ovaries are oval-shaped organs located on either side of the abdomen. Each ovary contains thousands of eggs called ovum. It secretes female hormones called oestrogen and progesterone which regulate and maintain the female reproductive cycle. 2.: Also, known as fallopian tubes. It is a thin and long tube that carries the egg from the ovary to uterus. They allow ovum to travel in the tube. 3.Uterus: Uterus is a hollow muscular organ which has the capacity to bear the child. It is otherwise called as the womb. After fertilization, female reproductive hormones bring in many changes to the uterus, so as to bear the growing embryo. The uterus opens into the vagina. 4.Vagina: Vagina lies at the end of the uterus. It receives penis during the sexual intercourse and is the site where sperms are deposited. The vagina is connected to the uterus at the cervix. Cervix is the neck like the opening to the uterus. 3. Define asexual reproduction. Describe two methods of asexual reproduction with the help of diagrams. Answer: Asexual reproduction The type of reproduction in which only a single parent is involved is called asexual reproduction. Types of asexual reproduction 1.Budding:  A bud starts as an outgrowth on the parent body.  As this bud grows, it becomes a new individual organism.  In some organisms, the buds remain attached to the parent’s body (example: yeast)  In some organisms, it detaches from parent body and develops into a complete mature individual (hydra).  This type of reproduction is called as budding.

2.Fission It is a type of asexual reproduction in which a single-celled organism divides into two. • Division of nucleus is followed by division of other organelles in the cytoplasm and finally the cytoplasm. • Thus, two cells are produced from one parent cell. • Example: Amoeba, Paramecium, Euglena, etc. • Amoeba reproduces by binary fission, which is dividing into two cells. If one parent cell gives rise to many daughter cells, this type of fission is called as multiple fission.

4. Differentiate between internal and external fertilization. Answer: i. Internal fertilization: When fertilization takes place inside the female’s body, it is called internal fertilization. Example: human beings some animals such as hen, cows, dogs etc. ii. External fertilization: When fertilization takes place outside the female’s body, it is called external fertilization. Example: aquatic animals like fish, starfish and frog. 5. Discuss how a zygote develops into an individual in humans. Answer: Development of an embryo After fertilization, the zygote moves down to the uterus and divides repeatedly to form a ball of cells called embryo. The embryo attaches itself to the uterus wall with the help of placenta, where further development occurs. Once implanted, the embryo divides further and starts differentiating into different types of cells performing specific functions, such as muscle cells, nerve cells and blood cells. These cells eventually form different tissues and organs of the body.Gradually, the different body parts such as hands, legs, head, eyes, ears, etc. start to develop. The stage of the embryo in which all the body parts can be identify is called a foetus. This stage takes place in or after about 8 weeks of fertilization. 6. Describe the life cycle of a frog to explain metamorphosis. Answer: Life cycle of frog

Frogs are amphibians. They go through several stages of life before they become adult frogs and during those stages, they live only in water. Stage 1: Egg A frog begins life as a fertilized egg. A female frog lays a lot of eggs at one time in a pond. The eggs float on water in a jelly mass or cluster. Stage 2: Tadpole When the tadpole hatches, it looks more like a fish than a frog. It doesn’t have any legs! It has gills that allow it to breathe underwater. Stage 3: Young Frog The tadpole grows two front legs and its long tail becomes shorter and shorter. Stage 4: Adult Frog The frog’s tail will eventually disappear completely and it will start to eat insects instead of plants from the water. 7. Write a short note on in-vitro fertilization. Answer: Some women are unable to bear babies because their oviduct is blocked. This prevents them from being fertilized as the sperms cannot reach the oviduct where the ovum is present. This problem can be overcome by fertilizing an ovum with a human sperm in the laboratory with a technology called in-vitro fertilization. In this technique, freshly ovulated eggs are collected from women who are incapable of bearing babies. These eggs are maintained under sterilized conditions and are fertilized with the sperms collected from the husband of the woman. Here the fertilization occurs outside the body of the female. In case fertilization occurs, the zygote is allowed to develop for about seven days and then it is transferred into the mother’s uterus. Foetus develops in the mother’s womb and is delivered at the end of nine months. Babies born through this method are called test-tube babies.