1.
The disease caused by micro-organism which reproduces by multiple fission is known as:
Correct Answer
C. Malaria
Explanation
Malaria is caused by a micro-organism known as Plasmodium. Plasmodium reproduces by multiple fission, which means it undergoes a type of cell division where multiple daughter cells are produced at once. This process allows the micro-organism to rapidly multiply within the host's red blood cells, leading to the characteristic symptoms of malaria such as fever, chills, and fatigue. Therefore, the disease caused by a micro-organism that reproduces by multiple fission is known as malaria.
2.
Reproduction is essential for living organisms in order to:
Correct Answer
D. Continue the species for ever
Explanation
Reproduction is essential for living organisms to continue the species for ever. Through reproduction, organisms can produce offspring that inherit their genetic traits and ensure the survival and continuation of the species over time. This allows for genetic diversity, adaptation to changing environments, and the potential for evolution. Reproduction is a fundamental biological process that ensures the long-term survival and success of a species.
3.
A greater similarity between themselves is found in the offspring’s formed by asexual reproduction method is because:
(i) Asexual reproduction involves only one parent
(ii) Asexual reproduction involves two parents
(iii) Asexual reproduction involves gametes
(iv) Asexual reproduction does not involve gametes
Correct Answer
D. (i) and (iv)
Explanation
The correct answer is (i) and (iv). This is because asexual reproduction involves only one parent, which means that the offspring will have a greater similarity to the parent. Additionally, asexual reproduction does not involve the fusion of gametes, which further contributes to the similarity between the parent and offspring.
4.
A simple multicellular animal having tentacles living in freshwater usually reproduces by the asexual process of:
Correct Answer
C. Budding
Explanation
Budding is a form of asexual reproduction in which a new organism develops as an outgrowth or bud from the parent organism. In this process, a small portion of the parent organism's body grows and eventually detaches to become an independent individual. This method of reproduction is commonly observed in simple multicellular animals, such as Hydra, which have tentacles and live in freshwater. By reproducing through budding, these organisms can quickly and efficiently create offspring without the need for a mate or the production of specialized reproductive cells.
5.
The rapid spreading of bread mould on slices of bread are due to:
(i) Presence of large number of spores in air
(ii) Presence of large number of thread-like branched hyphae
(iii) Presence of moisture and nutrients
(iv) Formation of round shaped sporangia
Correct Answer
A. (i) and (iii)
Explanation
The rapid spreading of bread mould on slices of bread is due to the presence of a large number of spores in the air, which allows for easy dispersal and colonization of new areas. Additionally, the presence of moisture and nutrients on the bread provides an ideal environment for the mould to grow and thrive.
6.
Vegetative propagation refers to the formation of new plants from the following existing organs of the old plants:
Correct Answer
B. Stems, roots and leaves
Explanation
Vegetative propagation is the process by which new plants are formed from existing organs of old plants. Stems, roots, and leaves are the three main organs that can be used for vegetative propagation. Stems have the ability to produce new shoots and roots, while roots can give rise to new plants through the formation of adventitious buds. Leaves can also be used for vegetative propagation through techniques such as leaf cuttings. Therefore, the correct answer is that new plants can be formed from stems, roots, and leaves.
7.
An organism capable of reproducing by two asexual reproduction methods one similar to the reproduction in yeast and the other similar to the reproduction in Planaria is:
Correct Answer
C. Hydra
Explanation
Hydra is the correct answer because it is capable of reproducing by two asexual reproduction methods. One method is similar to the reproduction in yeast, which involves budding, where a small outgrowth or bud forms on the parent organism and eventually detaches to become a new individual. The other method is similar to the reproduction in Planaria, which involves regeneration, where a portion of the organism can grow into a new individual if it is cut or damaged.
8.
A Planaria worm is cut horizontally in the middle into two halves P and Q such that the part P contains the whole head of the worm. Another Planaria worm is cut vertically into two halves R and S in such a way that both the cut pieces R and S contain half head each. Which of the cut pieces of the two Planaria worms could regenerate to form the complete respective worms?
Correct Answer
D. P, Q, R and S
Explanation
Both P and Q can regenerate to form a complete worm because part P contains the whole head, which is necessary for regeneration. Additionally, both R and S can regenerate to form a complete worm because each piece contains half of the head, which is sufficient for regeneration. Therefore, all four cut pieces (P, Q, R, and S) have the potential to regenerate into complete worms.
9.
The number of chromosomes in parents and offsprings of a particular species remains constant due to:
Correct Answer
B. Halving of chromosomes during gamete formation
Explanation
During gamete formation, the number of chromosomes is halved. This is because gametes, which are reproductive cells, need to have half the number of chromosomes as compared to the regular body cells. When the gametes combine during fertilization, the resulting zygote will have the correct number of chromosomes for that particular species. Therefore, the number of chromosomes in parents and offspring remains constant due to the halving of chromosomes during gamete formation.
10.
The surgical method which prevents the sperms from reaching the ovum and pregnancy does not occur is:
Correct Answer
B. Vasectomy
Explanation
Vasectomy is the correct answer because it is a surgical procedure that involves cutting or blocking the vas deferens, the tubes that carry sperm from the testicles to the urethra. By blocking these tubes, sperm are unable to reach the ovum, preventing fertilization and pregnancy. IUCD (intrauterine contraceptive device) is a form of birth control that is inserted into the uterus, but it does not involve surgical intervention to prevent the sperm from reaching the ovum. Condoms act as a barrier method, preventing sperm from entering the vagina. Tubectomy is a surgical procedure for female sterilization, where the fallopian tubes are cut or blocked to prevent the egg from reaching the uterus.
11.
The figure given alongside shows the human male reproductive organs. Which structures make sperms and seminal fluid?
Correct Answer
D. Y makes sperms and V makes seminal fluid
Explanation
The correct answer is Y makes sperms and V makes seminal fluid. In the figure, Y represents the testes, which are responsible for producing sperm cells through a process called spermatogenesis. V represents the seminal vesicles, which produce the seminal fluid.
12.
The correct sequence of organs in the male reproductive system for the transport of sperms is:
Correct Answer
A. Testis → vas deferens → urethra
Explanation
The correct sequence of organs in the male reproductive system for the transport of sperms is testis → vas deferens → urethra. The testis is responsible for the production of sperm cells. The sperm cells then travel through the vas deferens, which is a tube that connects the testis to the urethra. Finally, the sperm cells are transported through the urethra, which is the tube that carries both urine and semen out of the body.
13.
Which among the following are not the functions of testes at puberty?
(i) Formation of germ cells
(ii) Secretion of testosterone
(iii) Development of placenta
(iv) Secretion of estrogen
Correct Answer
D. (iii) and (iv)
Explanation
At puberty, the testes undergo several changes and functions. They are responsible for the formation of germ cells, which are the precursor cells for sperm production. The testes also secrete testosterone, a hormone that is responsible for the development of secondary sexual characteristics in males. However, the development of the placenta is a function of the female reproductive system, not the testes. Similarly, the secretion of estrogen is also a function of the female reproductive system, primarily the ovaries. Therefore, the correct answer is (iii) and (iv).
14.
In the figure given alongside, the parts marked A, B and C are sequentially:
Correct Answer
C. Plumule, cotyledon and radicle
Explanation
In the figure, the part marked A is the plumule, which is the embryonic shoot of a plant. The part marked B is the cotyledon, which is the embryonic leaf of a plant. The part marked C is the radicle, which is the embryonic root of a plant. Therefore, the correct sequence is plumule, cotyledon, and radicle.
15.
The ratio of number of chromosomes in a human zygote and a human sperm is:
Correct Answer
A. 2 : 1
Explanation
In humans, a zygote is formed by the fusion of a sperm cell and an egg cell during fertilization. The sperm cell contributes half of the genetic material to the zygote, while the egg cell contributes the other half. Since the sperm cell only contains 23 chromosomes and the egg cell also contains 23 chromosomes, the ratio of the number of chromosomes in a human zygote to a human sperm is 2:1.