Important Questions: Reproduction in Animals - Class 8 MCQ

Asexual reproduction is a type of reproduction where offspring are produced without the fusion of gametes (sperm and egg). Instead, a single organism can reproduce on its own, creating genetically identical offspring (clones).

B is incorrect because it describes sexual reproduction, where male and female gametes fuse.

C is incorrect because asexual reproduction occurs in both plants and animals, not just in plants.

D is incorrect because it refers to sexual reproduction, where gametes fuse, often being dissimilar (male and female).

A (Reproduction in hydra), B (Reproduction in amoeba), and C (Reproduction in bacteria) are all examples of asexual reproduction, where offspring are produced without the fusion of gametes.

D (Reproduction in butterfly) is an example of sexual reproduction, where two parents (male and female) contribute genetic material to produce offspring.

A is correct: The human female egg cells (oocytes) begin to mature and are available for release starting at puberty.

B is correct: The two ovaries alternate in releasing egg cells, though both ovaries do not release eggs simultaneously.

C is correct: Typically, one egg is released from the ovary every 28 days during a woman's menstrual cycle.

D is incorrect: An egg cell (ovum) typically survives for about 12 to 24 hours after ovulation. It does not live for a month.

Explanation:

• Placenta (W): The placenta provides nutrients and oxygen to the fetus and removes waste products.
• Fetus (X): The developing baby inside the uterus.
• Amniotic fluid (Y): The fluid surrounding the fetus inside the amniotic sac, which cushions and protects it.
• Fetal membrane (Z): The membrane that surrounds the fetus and amniotic fluid within the uterus.

The placenta is the structure that facilitates nutrient, gas, and waste exchange between the mother and fetus while preventing the direct mixing of their blood. The placenta has a special barrier (placental membrane) that allows the exchange of substances but keeps the blood of the mother and fetus separate.

The umbilical cord (A) connects the fetus to the placenta but does not prevent the mixing of blood.

The uterus wall (B) surrounds the uterus but does not specifically prevent blood mixing.

The water sac (D), or amniotic sac, surrounds the fetus but does not play a role in preventing blood mixing. It contains amniotic fluid to protect and cushion the fetus.

The correct answer is:

C: Placenta

The correct sequence in the formation of a baby is as follows. Zygote →  Embryo → Foetus → Baby

• Zygote: The fertilized egg, formed after the sperm and egg fuse.
• Embryo: The early stage of development after the zygote, where the basic body structures begin to form.
• Foetus: The later stage of development, where the organism starts to resemble a baby and organs continue to develop.
• Baby: The final stage after birth, when the organism is fully developed and capable of independent life.

Options I and III are true of comparison of sexual and asexual reproduction.

Sexual reproduction - It involves two individuals, where two different gametes fuse together (male gamete fuses with female gamete).
Asexual reproduction - It involves only one individual; the offspring has same characters as parents.

Both Paramecium and Amoeba are unicellular organisms (A), meaning they consist of only one cell.

Both reproduce by binary fission (C), where a single cell divides to form two identical daughter cells.

B is incorrect because both Paramecium and Amoeba have a nucleus, which contains their genetic material.

• Fertilization occurs when a sperm meets an egg, which typically happens in the fallopian tube.
• The fallopian tubes connect the ovaries to the uterus and provide a pathway for the egg to travel after ovulation.
• While the ovaries produce eggs and the uterus is where a fertilized egg implants, the actual meeting of sperm and egg takes place in the fallopian tube.

The animals that produce new young ones are called viviparous animals.

Explanation:

Viviparous animals give birth to live young, unlike oviparous animals, which lay eggs. In viviparous animals, the embryo develops inside the mother's body, receiving nourishment directly until birth. Examples include most mammals, like humans, dogs, and cats.

The correct answer is:

Frog

Explanation: External fertilization occurs when the fusion of sperm and egg happens outside the body of the organism, usually in a water environment. Frogs show external fertilization, where both male and female release their gametes into water, and fertilization takes place outside their bodies. In contrast, humans, cows, and hens undergo internal fertilization, where fertilization happens inside the female body.

P is ovulation, Q is implantation and R is fertilization.

• The umbilical cord connects the fetus to the placenta, facilitating nutrient and waste exchange.
• It transports urea, a waste product, from the fetus to the mother for elimination.
• Antibodies are transferred to provide the fetus with immunity against infections.
• Carbon dioxide, a waste gas produced by the fetus, is carried back to the mother for exhalation.

Hydra reproduce by asexual mode. Budding is the process by which hydra reproduce through asexual mode. An outgrowth grows from the parent body due to the repeated cell division at a specific site. The cell which divide rapidly are known as regenerative cell. The outgrowth from the parent body is known as bud. This bud separates from the parent and develops into a genetically identical new organism.