- Assertion (A) : The sex of a child in human beings will be determined by the type of chromosome he/she inherits from the father.
Reason (R) : A child who inherits ‘X’ chromosome from his father would be a girl (XX), while a child who inherits a ‘Y’ chromosome from the father would be a boy (XY).
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion (A).
(c) (A) is true, but (R) is, false.
(d) (A) is false, but (R) is true. (2020)
Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A). - Assertion (A): Variation is useful for the survival of species over time.
Reason (R): Populations of organisms fill well-defined places in the ecosystem, using their ability to reproduce.
Answer:
(b) Both (A) and (R) are true but (R) is not the correct explanation of the assertion.
Explanation: Although populations of organisms fill well-defined pLaces in the ecosystem, using their ability to reproduce, the consistency of DNA copying during reproduction. Reproduction is important for the maintenance of body design features. Reproduction is linked to the stability of populations of species.
However, variation is useful for the survival of species over time as niches can change drastically but only those organisms will be able to survive which have some variations in them.
- Assertion (A): All multi-cellular organisms can divide cell by cell.
Reason (R): Many multi-cellular organisms are not simply a random collection of cells.
Answer:
(d) (A) is false but (R) is true
Explanation: All multi-cellular organisms cannot simply multiply cell by cell as they are not just a random collection of cells. Specialized cells are organized as tissues and tissues are organized into organs, which occupy definite positions in the body. Multi-cellular organisms, therefore, need to use more complex ways of reproduction.
- Assertion (A): Pollen grains are produced by all flowers.
Reason (R): Stamen is the male reproductive part of a flower and produces pollen grains.
Answer:
(d) (A) is false but (R) is true
Explanation: All flowers do not produce pollen grains as flowers may be unisexual when it contains either stamens or pistil or bisexual when it contains both stamens and pistil. Stamen is the male reproductive part of a flower and produces pollen grains that are yellowish in colour.
- Assertion (A): Testes in human males are located outside the abdominal cavity in scrotum.
Reason (R): Testes secrete the male sex hormone testosterone.
Answer:
(b) Both (A) and (R) are true but (R) is not the correct explanation of the (A)
- Fertilisation is the process of:
(a) transfer of male gamete to female gamete.
(b) fusion of nuclei of male and female gamete.
(c) adhesion of male and female reproductive organs.
(d) the formation of gametes by a reproductive organ.
Answer:
(b) Fusion of nuclei of male and female gamete.
Explanation: Fertilization is the fusion of nucleus of male and female garnets to form a single cell called as zygote. Fertilization occurs in sexually reproducing organisms.
Related Theory:
During sexual mode of reproduction germ cells (gametes) of two individuals need to fuse together. It can happen by either of the following:
External release of germ cells from body of an individual as seen in angiospermic plants, frog, fish etc. This is known as external fertilization.
Internal transfer of germ cells by physical contact between male and female organisms as in mammals. This is called internal fertilization.
- Characters that are transmitted from parents to offsprings during reproduction show:
(a) OnLy similarities with parents
(b) Only variations with parents
(c) Both similarities and variations with parents
(d) Neither similarities nor variations
Answer: - Choose the correct statement(s) on budding in yeast from the following:
(I) A parent cell divides into two or more daughter ceLLs and here the parent identity is Lost.
(II) In this the elongated nucleus divides to form two or more daughter nucLei.
(III)A bud arises from a particular region on a parent body.
(IV)After detaching from the parent body the bud grows into a new independent individual.
(a) (I) only
(b) (III) only
(c) (II) and (III) only
(d) (III) and (IV) only
Answer:
(d) (III) and (IV) only
Explanation: Yeast reproduces asexually by the process of budding in which a bud arises from a particular region on a parent body. And after detaching from the parent body the bud grows into a new independent individual.
Statements I and II are for binary and multiple fission respectively.
- The number of chromosomes in parents and offsprings of a particular species remains constant due to:
(a) Doubling of chromosomes after zygote formation
(b) Halving of chromosomes during gamete formation
(c) Doubling of chromosomes after gamete formation
(d) Halving of chromosomes after gamete formation
Answer: - Slides of binary fission in Amoeba and budding in yeast were given for observation to a group of students. Some of the observations reported by the group are given below:
(I) Cytokinesis was observed in the yeast cell.
(II) A chain of buds were observed in Amoeba.
(III) Single cell of Amoeba and single cell of yeast were undergoing binary fission and budding respectively.
(IV) Elongated nucleus was dividing to form two daughter nuclei in Amoeba.
The correctly reported observations are:
(a) (I) and (II)
(b) (II) and (III)
(c) (III) and (IV)
(d) (I) and (IV)
Answer:
(c) (III) and (IV) - Which of the following statements are true for flowers?
(I) Flowers are always bisexual
(II) They are the sexual reproductive organs
(III) They are produced in all groups of plants
(IV) After fertilization they give rise to fruits
(a) (I) and (IV)
(b) (II) and (III)
(c) (I) and (III)
(d) (II) and (IV)
Answer:
(d) (II) and (IV) i.e. they are the sexual reproductive organs and after fertilization they give rise to fruits
Explanation: Flowers are the sexually reproductive organs of a plant and a fertilized flower give rise to fruit.
- Characters transmitted from parents to offspring are present in:
(a) Cytoplasm
(b) Ribosome
(c) Golgi bodies
(d) Genes
Answer:
(d) Genes
- Semen which contains millions of sperms also contains secretions of seminal vesicle and prostrate gland (accessory glands). It makes the tranport of sperms easier and provide nutrition to sperms.
Correct sequence of organs in the male reproductive system for transport of sperms is:
(a) Testis → vas deferens → urethra
(b) Testis → ureter → urethra
(c) Testis → urethra → ureter
(d) Testis → vas deferens → ureter
Answer:
(a) Testis → vas deferens → urethra
Explanation: Testis produces sperms or germ cells. The sperms formed are delivered through the vas deferens which unites with a tube coming from the urinary bladder. The urethra thus forms a common passage for both the sperms and urine.
- Which among the following diseases is not sexually transmitted?
(a) Syphillis
(b) Hepatitis
(c) HIV-AIDS
(d) Gonorrhoea
Answer:
(b) Hepatitis
- Which of the following is not the part of female reproductive system?
(a) ovary
(b) fallopian tube
(c) uterus
(d) vas deferens
Answer:
(d) vas deferens
Explanation: Vas deferens is part of male reproductive system.
- Study the figure below and identify the row containing incorrect information.
Part Name Function
(a) A is Cotyledon It is the future plant
(b) B is Plumule It is the future shoot
(c) C is Seed coat It is the outer covering of the ovule
(d) D is Radicle It is the future root
Answer:
(a) Part Name: A is cotyledon; Function: It is the future plant
Explanation: A is cotyledon and is the food store of the future plant.
- Identify the incorrect statement from among the following statements for unisexual flowers.
(a) They always possess stamen and pistil
(b) They possess either stamen or pistil
(c) They show cross pollination
(d) Unisexualflowers posessing only stamens cannot produce fruits
Answer:
(a) They always possess stamen and pistil
Explanation: Unisexual flowers contain either stamens or carpels. Bisexual flowers contain both male and female reproductive organs stamen and carpel.
- The table below lists the organs/parts of human reproductive system and their functions. Identify the row containing incorrect information.
Part/ Organ of Reproductive system Function
(a) Prostate gland and seminal vesicles Production of fluid to provide a medium for sperms.
(b) Testis Secretes the hormone that regulates formation of sperms.
(c) Uterus Provides nutrition from mother’s blood to embryo.
(d) Fallopian tube Carries egg from ovaries to the womb
Answer:
(c) Part/Organ of Reproductive system: Uterus; Function: Provides nutrition from mother’s blood to embryo.
Explanation: The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta which is a disc embedded in the uterine wall and contains villi on the embryo’s side of the tissue.
- Reason, why paramecium decides for sexual reproduction, is:
(a) It can produce more number of progenies.
(b) Progenies can be considered to be clones of their parents
(c) It leads to genetic variations
(d) Asexual reproduction is unreliable.
Answer:
(c) It leads to genetic variations
Puberty is the time when boys and girls move through a series of significant, natural and healthy changes. These physical, psychological and emotional changes signal that they are moving from childhood to adolescence. Puberty starts when changes in their brain cause sex hormones to start being released in girls’ ovaries and boys’ testes. This usually happens around 10-11 years for girls and around 11-13 years for boys. But it’s normal for the start of puberty to range from 8-13 years in girls and 9-14 years in boys.
The graph below shows the average height of girls and boys up to the age of 18 years.
- Select the correct observations:
(I) During 8-12 gears, girls experience a sudden growth.
(II) During 12-16 gears, bogs experience sudden grown
(III) Bogs are alwags taller than girls of their age.
(IV) Growth in both bogs and girls stops after 16 gears.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (I), (II) and (III)
(d) (I), (III) and (IV)
Answer:
(a) Both (I) and (II)
Explanation: We note that during 8-12 years, girls experience a sudden growth and have more height as compared to boys. This is because puberty occurs earlier in girls (10-12 years), so they grow rapidly during this phase.
During 12-16 years, boys experience sudden grown and their height becomes the same as girls. This is because puberty occurs later in boys (12-13 years) and they grow rapidly during puberty.
- The table below lists some changes observed in girls and bogs during pubertg. Select the row containing incorrect observation.
Changes in Girls Changes in Bogs
(a) Height increases verg quickly and earlier than in bogs Height increases very quickly and Later than girls
(b) Voice pitch becomes higher Voice pitch becomes Lower
(c) Shoulders become broad Hips become broad
(d) Menstruation starts Nocturnal emissions occur
Answer:
(c) changes in Girls: Shoulders become broad;
Changes in Boys: Hips become broad
- The most rapid growth in girls takes place during:
(a) 0 – 4 gears
(b) 4 – 8 gears
(c) 8-12 gears
(d) 12 – 16 gears
Answer:
(a) 0 – 4 years
- Name the organs producing sperms and ova respectively in humans.
- Name the method by which Spirogyra reproduces under favourable conditions. Is this method sexual or asexual?
- Name one organism which reproduces by:
(A) multiple fission
(B) binary fission
- Name the part of Bryophyllum where the buds are produced for vegetative propagation
- What is meant by the term regeneration?
Answer:
Regeneration: The process of getting back a full organism from its body parts is called regeneration. The simple animals like Hydra and Planaria shows regeneration, i.e. if Hydra or Planaria somehow get cut into a number of pieces, then each body part can grow into a new complete organism.