Class 8 Science Chapter 6 MCQ

In option [C], sperm is a male gamete, a part of male reproductive system, whereas the other three terms are related to the female reproductive system. As there is a mismatch, this option is an incorrect combination. This is because it has parts of both male and female reproductive system. In option [A], all four terms are related to male reproductive system, and in option [B] and [D], all four terms are related to female reproductive system. As there is no mismatch, these options are correct combinations.

The fusion of a male gamete with the female gamete gives rise to a new cell called zygote. Zygote is a single cell which contains one nucleus. The nucleus of zygote is formed by the combination of nuclei of “sperm” and “egg”.

Here, all the statements are correct. Hence, your answer will be option [D].

Asexual reproduction is the simplest method of reproduction. It takes only in those animals whose bodies have a simple structure. In asexual reproduction the young one or offspring produced is an exact copy of the parent. Asexual reproduction is a method producing generally identical off-springs.

Hen is the odd one because it is the only one which lays eggs (oviparous), that is it shows oviparity. Humans, cow and dog are viviparous, i.e., they give birth to young ones. All four organisms show internal fertilization, none of them fertilizes externally, except one.

A large number of gametes are released by such animals to ensure better chance of fertilization. Since, the gametes are laid in water, many of them are carried away by moving water, wind or rain and many are eaten by other animals. Therefore, production of large number of gametes is necessary.

Ovary is the structure that occurs in the reproductive system of flowering plants as well as of humans. In both of them, it produces female gametes called egg.

In Hydra, reproduction take place by budding. A small part of the body of an organism grows as “bud” which then detaches and becomes a new organism. The other options Amoeba, Paramecium and bacteria reproduce asexually by binary fission.

Testes are the oval shaped organs which lie outside the abdominal cavity of man. A man has two testes. Testes are the real reproductive organs in man. The male sex cells called sperms are made in testes. Thus, testes make male gametes called sperms or millions of sperms are produced in the testes.

Fertilization in humans take place in the female body. The sperms of men are introduced by penis into female’s body through vagina. The sperms then pass through the uterus and reach to oviducts. It is here, that sperms combines with egg to forms zygote (i.e. fertilization occurs).

In humans, the immediate product of fertilization is the zygote formed by the fusion of sperm and egg. This zygote undergoes repeated cell divisions white traveling its path from the fallopian tube to uterus, and this group of divided cells is called embryo, which gets embedded in the uterine walls. This is called implantation. Remember, a zygote is formed by the fusion of male and female gametes (sperm and egg). An embryo is formed by the repeated cell division of zygote. A foetus is formed by the growth and development of an embryo.

The offspring formed as a result of sexual reproduction exhibits more variations because genetic material comes from two parents of same species.

The aquatic animals in which fertilization takes place in water, lay unfertilized eggs and fertilization takes place when male gametes, already present in water, float up to them and fuse. Thus, these animals are oviparous as they lay eggs, and exhibit external fertilization as the fusion of male and female gametes takes place outside the body of an organism.

Here, all the statements are correct. Hence, your answer will be option [D].

All the multicellular animals (including humans) start their life from a single cell called “Zygote”, through sexual reproduction. In human beings, the process of fertilization is the meeting of a sperm cell from the father with an egg cell from the mother to form a “fertilized egg” cell called zygote. And this is the stage where multicellular organisms start their life with the single cell called “Zygote”.

Embryo grows and becomes a foetus in which all the main body features of the baby animal have formed. And foetus grows and develops to form a new baby animal.

Here, all the statements are correct. Hence, your answer will be option [D].

After the sperms are mixed with eggs in a glass dish or glass test tube then it about after a week, one or more embryos are placed in the woman’s uterus or womb. If the embryo gets implanted in the uterus successfully, then normal pregnancy occurs and a baby is born after about nine months.

The hen is a bird. Internal fertilization take place in hen also. But a hen does not give birth to chicks (like human beings). As fertilization take place inside the body of hen and after that it travels down the oviduct, many protective layers are formed around the embryo. The hard shell that we see in hen’s egg, is the outermost protective layer. After the hard egg shell is formed around the developing embryo, the hen finally lays the egg. The hen then sits on the eggs to provide sufficient warmth to the eggs for the development of the embryo into the chicks. The embryo takes about 3 weeks or 21 days to develop into a complete chick. And after the chick is completely developed, the egg shell breaks open automatically and the chick comes out of it.

The fertilization which takes place outside the female body is called external fertilization. In external fertilization the female animal eggs are fertilized by sperm outside her body. External fertilization is very common in aquatic animals such as frog, fish and star-fish etc. Animals exhibiting external fertilisation produce a large number of gametes to ensure better chance of fertilisation.

The production of a new organisms from a single parent without the involvement of sex cells or gametes is called asexual reproduction. It is called asexual reproduction because it does not use special cells called “sex cells” or “gametes” for producing a new organism.

An egg cell can live in the body for only 6 – 8 hours or 1 day. This process takes about two weeks on average, beginning with a woman’s menstrual period. Once the egg is mature, it’s released from the ovary in a process known as ovulation. The egg then travels down the fallopian tube toward the uterus. The egg is only viable for about 24 hours once it’s been released. Sperm can live inside a woman’s body for less than 5 days. A released egg lives for less than 24 hours. The highest pregnancy rates have been reported when the egg and sperm join together within 4 to 6 hours of ovulation.

Unicellular organisms also can reproduce. But their methods are different. There are many different ways in which new organisms are produced from their parents. Some organisms like Amoeba just splits into two parts to produce new Amoebae, some organisms like Hydra grow out of the parent’s body in the form of a bud.

Option [B] and [C] are true. Menstruation occurs every 28 days and during every menstrual cycle, one mature ovum will be released by the ovary.

In human beings, the process of reproduction starts by the formation of male and female gametes respectively in the male and female reproductive systems. This is followed by the fusion of these gametes inside the female body, a process called fertilization. The fertilized product of this process is termed as a zygote. The fusion forms a zygote, which divides repeatedly to form the embryo. The embryo gets implanted in female uterus for further development to form foetus. Thus, the correct sequence is gamete formation, fertilization, zygote and embryo. Hence, your answer should be option [A].