Grade 9 : Science - 3. Reproduction (Set 3) | Concept of Maths

Question 1

A student is observing binary fission in Amoeba and Leishmania under a microscope. They notice that while Amoeba divides in any random plane, Leishmania divides only along a specific longitudinal plane. Which of the following statements correctly explains the biological reasoning behind this difference?

Accepted Answer

A) In Amoeba, there is no fixed body shape or specific organelle alignment, permitting fission in any plane. In Leishmania, binary fission must occur in a definite longitudinal orientation relative to its whip-like flagellum.

Answer

B) In Amoeba, fission is longitudinal due to pseudopodia alignment, while Leishmania undergoes transverse fission to keep the flagellum intact.

Answer

C) Both organisms divide along random planes, but Leishmania requires a longer period to dissolve its nucleus.

Answer

D) Leishmania reproduces by multiple fission to produce flagellated spores, whereas Amoeba only undergoes simple transverse binary fission.

Question 2

Four healthy, bisexual mustard flowers (A, B, C, and D) are manipulated in an experiment before they bloom:

Flower A: Anthers are removed (emasculated) and the flower is covered with a polythene bag.
Flower B: The pistil is removed, and the flower is left open to the wind.
Flower C: Left completely intact but covered with a polythene bag.
Flower D: Anthers are removed, pollen from another mustard plant is dusted on its stigma, and it is covered.

Which of these flowers will successfully develop into fruits containing viable seeds?

Accepted Answer

B) Flowers C and D only

Answer

A) Flowers B and C only

Answer

C) Flowers A and D only

Answer

D) Flowers A, C, and D

Question 3

A surgical procedure known as a vasectomy involves cutting and ligating the vas deferens on both sides. Analyze the physiological effects of this procedure. Which of the following statements is scientifically accurate regarding the semen composition of a vasectomized individual?

Accepted Answer

B) Sperms are still produced in the testes but cannot travel to the urethra; hence, the ejaculated fluid (semen) contains accessory gland fluids but no sperms.

Answer

A) Semen will no longer contain secretions from the prostate gland and seminal vesicles, but will still carry active sperms from the testes.

Answer

C) Sperms immediately cease to be produced in the testes due to negative feedback, leading to a complete loss of testosterone production.

Answer

D) Sperms are redirected to the urinary bladder to be excreted with urine, while semen production stops entirely.

Question 4

Let the levels of Estrogen and Progesterone in a female be represented by E and P. During a normal 28-day menstrual cycle, a sudden drop in P occurs around Day 28 if fertilization has not taken place. What is the direct cellular/tissue consequence of this rapid decrease in Progesterone (P)?

Accepted Answer

A) It causes the breakdown of the highly vascularized endometrium (uterine lining), leading to the onset of menstruation.

Answer

B) It signals the immediate maturation and release of another mature follicle from the ovary.

Answer

C) It triggers the endometrium to grow thicker and more glandular to support delayed implantation.

Answer

D) It stimulates the conversion of the degenerated corpus luteum back into a functioning follicle.

Question 5

Population X of a plant species propagates solely via vegetative propagation (asexual), while Population Y propagates strictly via cross-pollination (sexual). A novel, highly infectious fungal pathogen is introduced to the fields harboring both populations. Predict the long-term survival outcome of these populations.

Accepted Answer

B) Population Y will have a higher survival rate because sexual reproduction introduces genetic variations, increasing the likelihood that some individuals possess resistance to the fungal pathogen.

Answer

A) Population X will survive better because asexual reproduction preserves the exact genetic traits of the strong parent plant.

Answer

C) Both populations will undergo total extinction at the exact same rate because they belong to the identical species.

Answer

D) Population X will adapt faster because vegetative clones can modify their DNA rapidly in response to external pathogens.

Question 6

A student records four observations in their laboratory notebook comparing budding in Yeast with binary fission in Amoeba:

In budding, the parent cell identity is completely lost as it splits into two equal halves.
In binary fission, karyokinesis (nuclear division) is followed by cytokinesis (cytoplasmic division).
Budding is an asymmetric process where a tiny outgrowth forms on the parent cell, which eventually detaches.
Binary fission yields two equal-sized daughter cells, whereas budding yields unequal-sized structures initially.

Which of these observations is/are incorrect?

Accepted Answer

A) Observation 1 only

Answer

B) Observation 3 only

Answer

C) Observations 1 and 4

Answer

D) Observations 2 and 3

Question 7

When a student cuts a Planaria into three pieces, each piece grows into a complete worm. When they cut a filament of Spirogyra into three pieces, each piece also grows into a new filament. Why is the process in Planaria classified as "Regeneration" while in Spirogyra it is called "Fragmentation"?

Accepted Answer

C) Spirogyra has a simple multicellular body plan where any fragment can grow by direct cell division. Planaria has complex tissue layers and organs, requiring specialized stem cells to proliferate and differentiate to reconstruct missing body parts.

Answer

A) Planaria is unicellular and undergoes mitosis, while Spirogyra is multicellular with complex organ systems.

Answer

B) Spirogyra utilizes specialized stem cells to grow, whereas Planaria simply divides its existing cells without growing.

Answer

D) Regeneration in Planaria requires mating at the site of injury, whereas fragmentation in Spirogyra is entirely non-reproductive.

Question 8

The placenta contains finger-like villi on the embryo side surrounded by maternal blood spaces on the mother’s side. If a genetic mutation reduces the development of these placental villi, reducing the total contact surface area by 50%, what is the direct physiological consequence on the fetus?

Accepted Answer

B) The rate of diffusion of oxygen, glucose, and metabolic wastes between maternal and fetal blood will be severely compromised, leading to growth retardation.

Answer

A) The flow of maternal blood directly into the fetal circulatory vessels will double to make up for the loss.

Answer

C) The fetus will compensate by synthesizing its own glucose and oxygen internally via anaerobic metabolic pathways.

Answer

D) The gestation period will be shortened by half because the embryo will develop twice as fast.

Question 9

A medical chart groups contraceptive methods by their main mechanism of action:

Category I (Barrier): Condoms & Diaphragms (prevent physical contact of sperm with egg).
Category II (Hormonal): Oral pills (prevent ovulation).
Category III (Intrauterine Devices): Copper-T (suppresses sperm motility and prevents fertilization/implantation).
Category IV (Surgical): Tubectomy (stops estrogen and progesterone production in ovaries).

Which category contains an incorrect description of its physiological mechanism?

Accepted Answer

D) Category IV

Answer

A) Category I

Answer

B) Category II

Answer

C) Category III

Question 10

In a certain angiosperm (flowering) plant, the somatic leaf cells contain 2n = 24 chromosomes. If this plant undergoes double fertilization, calculate the chromosome count in the following structures:

The egg cell before fertilization
The zygote
The endosperm cell

Identify the correct set of chromosome numbers.

Accepted Answer

A) Egg cell = 12, Zygote = 24, Endosperm cell = 36

Answer

B) Egg cell = 24, Zygote = 24, Endosperm cell = 48

Answer

C) Egg cell = 12, Zygote = 12, Endosperm cell = 24

Answer

D) Egg cell = 24, Zygote = 48, Endosperm cell = 72