"AKC SCIENCE CLASSES"
CLASS 10 TH (CBSE AND MP BOARD)
CHAPTER 08
HOW DO ORGANISMS REPRODUCE?
EXERCISE QUESTIONS AND ANSWERS
Q.01:- Asexual reproduction takes place through budding in
(a) amoeba
(b) yeast
(c) plasmodium
(d) leishmania.
Ans:- (b) yeast.
Q.02:- Which of the following is not a part of the female reproductive system in human beings?
(a) Overy
(b) Uterus
(c) Vas deferens
(d) Fallopian tube.
Ans:- (c) Vas deferens is a part of male reproductive system.
Q.03:- The anther contains
(a) sepals
(b) ovules
(c) carpel
(d) pollen grains.
Ans:- (d) pollen grains.
Q.04:- What are the advantages of sexual reproduction over asxual reproduction?
Ans:- Sexual reproduction incorporates the process of combining DNA from two different individuals during reproduction. Sexual reproduction promotes variation among the offspring of the same parents and provides opportunities for new combination of characters, thus playing an important role in the origin of new species. In asexual reproduction very little variations occur over generations. Asexual reproduction has a lesser significance for evolution of species.
Q.05:- What are the functions performed by the testis in human beings?
Ans:- Testis are the sites for the formation of sperms. They also produce a hormone named testosterone, which is responsible for secondary sex characters in males.
Q.06:- What does menstruation occur?
Ans:- The ovary released one egg every month and the uterus prepares for the implantation of the zygote by thickening its walls. If the egg is not fertilised, the uterine lining slowly breaks down and comes out through the vagina as blood and mucus. This cycle takes place roughly every month and is known as menstruation and lasts for about two to eight days.
Q.07:- Draw the label diagram of the longitudinal section of a flower.
Ans:-
Q.08:- What are the different methods of contraception?
Ans:- The methods used for regulation of child birth are :-
- Barrier method :- In this method physical devices like condom, cervical cap and diaphragm are used to prevent sperms to reach up to the ovum.
- Chemical method :- In this method specific drugs are used by females. These drugs may be (a) oral pills or (b) vaginal pills. Oral pills mainly contain hormones and are called oral contraceptives.
- Intrauterine Contraceptive Devices (IUCDSs) :- IUCD like Copper-T is placed safety in the uterus by a skilled doctor. IUCDs prevent implantation of the fertilized ovum inside the uterus.
- Surgical method :- This method is applicable to both male and female. In males, a small portion of vas deferens (on both side) in female is surgically removed or ligated (tied). It is known as vasectomy in males which prevents release of sperms from the testes. In females, it is called tubectomy.
Ans:- The modes for reproduction in unicellular organisms are :-
(ⅰ) Binary fission :- It is found in unicellular animals like amoeba, paramoecium, euglena,etc. After attaining an optimum size, the adult individual undergoes a simple division into two daughters of equal size. It consists of division of the nucleus followed by cleavage of cytoplasm into equal parts, each having a daughter nucleus. Binary fission can occur in any place in amoeba. It is longitudinal in euglena and transverse in Paramoecium. The organisms undergoing binary fission are almost immortal since they never grow old but divide to form two young offspring after attaining the adult size.
(ⅱ) Multiple fission :- The mode of asexual reproduction is found in unicellular animals or protozoans, e.g., amoeba, plasmodium, monocystis. The nucleus of the parent cell undergoes repeated divisions to produce a number of daughter nuclei. The cytoplasm cleaves around each nucleus simultaneously to form a number of daughter cells or individuals inside a parent cell. Ultimately, under favourable conditions parent cell membrane ruptures and daughter individuals are released.- Regeneration :- The ability of an organism to replace its lost body parts is called regeneration. Hydra, planaria and sponges exhibit regeneration. In hydra, 1/6 mm body piece is capable of regenerating into an entire individual.
- Fragmentation :- The mature spirogyra (an algae) breaks into two or more pieces (fragments). Each fragment grows into new individual. The process is called fragmentation.
- Sexual reproduction :- This is the mode in which male and female gametes fuse to form the zygote.
Ans:- Reproduction includes variations in the population which help the population to tide over adverse environment conditions and adapt to changing environment. Reproduction also helps generate copies of individuals which are suited to a particular environment.
Q.11:- What could be the reasons for adopting contraceptive methods?
Ans:- In our country, the population is increasing exponentially with equivalent of population of Australia being added every year. This puts strain on the natural resources of the country and is major cause of poverty in the country. Contraception prevents unintended pregnancies. Some contraceptive methods like condoms also prevent spread of STDs and lethal diseases like HIV-AIDS.
