The comprehensive approach in SCERT Class 8 Basic Science Textbook Solutions Chapter 18 Cells that Become Daughter Cells Important Questions ensure conceptual clarity.
Cells that Become Daughter Cells Extra Questions and Answers Class 8 Basic Science Chapter 18 Kerala Syllabus
Cells that Become Daughter Cells Class 8 Important Questions
Question 1.
Regarding Mitosis, choose the correct statements.
i. It helps in the formation of gametes.
ii. The chromosome number in daughter cells is the same as in the parent cell.
iii. It involves two main stages: Karyokinesis and Cytokinesis.
iv. Four daughter cells are produced from one parent Cell.
(a) i, iv correct
(b) ii, iii correct
(c) i, iii correct
(d) ii, iv correct
Answer:
(b) ii, iii correct
Question 2.
Characteristics of human gametes are given. Choose the correct option.
i. Sperm has three parts: head, body, and tail.
ii. Ovum is larger in size than sperm.
iii. Sperm has no ability to move.
iv. Ovum is motile.
a) i, ii correct
b) iii, iv correct
c) i, iii correct
d) ii, iv correct
Answer:
(a) i, ii correct
Question 3.
Select the correct statements about twins.
i. Identical twins are formed from two eggs fertilized by two different sperm.
ii. Fraternal twins will always be of the same sex.
iii. Identical twins have the same genetic material and hereditary traits.
iv. Conjoined twins result from the incomplete division of a single zygote.
a) i, ii correct
b) iii, iv correct
c) i, iv correct
d) ii, iii correct
Answer:
(b) iii, iv correct
Question 4.
Complete the flowchart related to events after ovulation if fertilization does not occur.
Ovulation → Ovum released → Fertilization does not occur (a) __________ disintegrates → Endometrium breaks down → (b) ___________
Answer:
(a) Ovum
(b) Menstruation
Question 5.
Complete the sequence of development from a zygote to a child.
Zygote → (a) ________ → Embryo → (b) ______ → Baby → Child
Answer:
(a) Cell division / Cell growth
(b) Foetus
Question 6.
Fill in the blanks in the summary of Mitosis stages.
(a) ________ → Chromosomes align at the center (Metaphase) → (b) ________ → Daughter nuclei are formed (Telophase).
Answer:
(a) Prophase (Chromosomes form)
(b) Anaphase (Chromatids separate)
Question 7.
Define the following terms:
(a) Pollination
(b) Fertilization (in humans)
Answer:
(a) Pollination: The process of pollen grains settling on the stigma of the pistil.
(b) Fertilization: The process of the sperm uniting with the egg (ovum), typically in the fallopian tube.
Question 8.
Give one example for each of the following modes of asexual reproduction:
(a) Budding
(b) Regeneration
Answer:
(a) Budding: Yeast
(b) Regeneration: Planaria or Hydra
Question 9.
What are the male and female gametes called in humans? Where are they produced?
Answer:
Male gamete: Sperm, produced in the Testis.
Female gamete: Ovum (egg), produced in the Ovary.
Question 10.
Illustration 18.2 shows the Stamen.
(a) Identify the part labelled as producing pollen grains.
(b) What is the function of pollen grains?
Answer:
(a) Anther.
(b) Pollen grains contain the male gam¬etes required for fertilization in plants.
Question 11.
Observe Figure.
(a) Which part contains the nucleus?
(b) Which part helps the sperm to move?
Answer:
(a) The Head.
(b) The Tail.
Question 12.
List any two physical changes of adolescence.
Answer:
Two physical changes are:
Sudden increase in height and body weight.
The growth of reproductive organs accelerates.
(Other acceptable answer: The activity of the glands in the skin increases).
Question 13.
Explain the significance of Meiosis in sexual reproduction.
Answer:
Meiosis is significant because it produces gametes (sperm and egg) with half the number of chromosomes (haploid, 23 in humans) compared to the parent germ cell (diploid, 46). When these gametes fuse during fertilization, the resulting zygote gets the correct diploid number of chromosomes (46). This process ensures the chromosome number remains constant across generations.
Question 14.
Why is the temperature in the scrotal sac maintained slightly lower than the normal body temperature?
Answer:
A temperature 2 to 2.5 degrees Celsius lower than normal body temperature is required for the proper production and development of sperm in the testes, which are located in the scrotal sac.
Question 15.
What happens during menstruation, and why does it occur?
Answer:
Menstruation occurs if fertilization does not happen after ovulation. The thickened inner lining of the uterus (endometrium), which had prepared to receive a fertilized egg with extra tissues and blood capillaries, is no longer needed. This lining breaks down and is discharged through the vagina along with blood and mucus.
Question 16.
Evaluate the statement: “Mitosis and Meiosis are essentially the same process.” Is this correct? Explain the key difference in outcome.
Answer:
No, the statement is incorrect. While both are types of cell division, they have different outcomes.
Mitosis produces two daughter cells that are genetically identical to the parent cell and have the same number of chromosomes. It’s primarily for growth and repair.
Meiosis produces four daughter cells (gametes) that are genetically different from the parent cell and have half the number of chromosomes. It’s essential for sexual reproduction.
Question 17.
Explain the importance of providing proper nutrition during adolescence.
Answer:
Adolescence is a period of rapid growth and development, including a sudden increase in height and weight, maturation of reproductive organs, and brain development. A balanced diet providing the right nutrients (proteins, vitamins, minerals, energy) is crucial to support this rapid physical growth and the significant hormonal and metabolic changes occurring. Both lack of essential nutrients and over-nutrition can negatively affect the body and overall health during this critical stage.
Question 18.
“Identical twins share the same hereditary factors, while fraternal twins do not.” Explain the biological reason for this difference based on their formation.
Answer:
Identical twins develop from a single zygote (one egg fertilized by one sperm) that splits into two early in development. Since they originate from the exact same genetic material, they share the same hereditary factors.
Fraternal twins develop from two separate eggs, each fertilized by a different sperm. They are essentially siblings conceived at the same time and share only about 50% of their genes on average, hence their hereditary factors are different.
Question 19.
Observe the following figure and answer the questions
(a) Identify the cell.
(b) In which human reproductive part, does it form?
(c) Temperature is a factor that influences the formation of these cells. How is it maintained?
Answer:
a) Sperm
b) Testis
c) Temperature less than body temperature (35 – 360C) is favourable for the formation of sperms. The scrotal sac helps to maintain this temperature.
Question 20.
Observe the following figure and answer the questions.
(a) Identify the part labelled as A.
(b) To which part does it grow?
Answer:
a) Pollen tube
b) It grows towards the ovary
Question 21.
Complete the illustration of physical changes during adolescence using indicators given in the box.
u Menstruation starts
u Shoulder bones expand
u Hair grows in various parts of body
u Ejaculation starts
u Hip bones widen
u Fast growth of sex organs Girls Boys
Answer:
B. Hip bones widen
C. Hair grows in various parts of the body
D. Fast growth of sex organs
E. Shoulder bones expand.
F. Ejaculation starts.
Question 22.
Correct the mistake if any in the underlined part of the given statements.
a) The ovum is produced by the oviduct.
b) Amniotic fluid protects the foetus from dehydration.
c) Fertilization takes place in the uterus.
Answer:
a) Ovary
c) Fallopian tube (oviduct)
Question 23.
Observe the figure of Pollen grain given below and answer the questions.
a) Identify the part indicated as ‘X’
b) Write the change that takes place in ‘X’ after pollination
Answer:
a) X: Generative nucleus
b) Generative nucleus divides to form two male gametes.
Question 24.
Analyse the following statement and give reason.
‘Changes related to adolescence are more rapid in girls than in boys’
Answer:
The parts of brain that control physical and mental changesdevelop rapidly in girls.
Question 25.
Adolescence is the period of rapid physical growth. Write any four food habits that ensures the availability of nutrients during that period.
Answer:
- Eat the right type of food at regular intervals.
- Never avoid breakfast.
- Take the right quantity of food during the right time.
- Include fruits and vegetables lentils etc. in the diet.
Question 26.
Fill in the blank:
The male reproductive organ in a flower is called the __________ .
Answer:
Stamen
Question 27.
Statement Analysis:
Read the following statements regarding cell division and choose the correct option:
Statement I: Mitosis helps in the growth of the body and repair of tissues.
Statement II: Meiosis helps to maintain a constant number of chromosomes across generations.
a) Statement I is correct and II is incorrect.
b) Statement I is incorrect and It is correct.
c) Both statements are correct.
d) Both statements are incorrect.
Answer:
c) Both statements are correct.
Question 28.
Find the odd one out:
Planaria, Hydra, Amoeba, Rose.
Answer:
Rose (Rose reproduces vegetatively/sexually, while the others are simple organisms/microorganisms listed under asexual modes like fission/regeneration in the text context).
Question 29.
Identify the relation:
Male Gamete : Sperm:: Female Gamete: _____________
Answer:
Ovum
Question 30.
The scrotal sac in males is capable of contracting and relaxing. How does this help in sperm production?
Answer:
Sperm production requires a temperature 2 to 2.5°C lower than body temperature. The contraction and relaxation of the scrotal sac help regulate and maintain this temperature.
Question 31.
Write two differences between pperm and Ovum based on their motility (ability to move) and size.
Answer:
Sperm: Motile (can move), Smaller size.
Ovum:Non-motile (cannot move), Larger size.
Question 32.
“In the first phase of Meiosis, the germ cell divides into two daughter cells.”
How many chromosomes will each daughter cell have if the parent cell has 46 chromosomes? What happens in the second phase of Meiosis?
Answer:
Each daughter cell will have 23 chromosomes (half of 46). In the second phase, these cells divide again like mitosis (chromosome number remains unchanged).
Question 33.
Explain the formation of the Endosperm in plants and state its function.
Answer:
Endosperm: Formed by the fusion of the second male gamete with the polar nuclei. Its function is to **store food** needed for the growth of the embryo.
Question 34.
Match the following:
| A (Part) | B (Function) |
| 1. Prostate gland | a) Production of Ovum |
| 2. Fallopian tube | b) Site of Fertilization |
| 3. Ovary | c) Produces fluid for sperm nourishment |
| d) Carries sperm to urethra |
Answer:
1 – c (Produces fluid for nourishment)
2 – b (Site of Fertilization)
3 – a (Production of Ovum)
Question 35.
Adolescence is a period of rapid growth.
a) Why do pimples (acne) commonly occur during this period?
b) Why is it important to include essential nutrients in the diet during this stage?
Answer:
a) Increased production of sex hormones
stimulates sebaceous glands to produce more sebum, which accumulates with dead cells to cause acne.
b) Rapid growth occurs during adolescence, so essential nutrients are required to support this development; lack of nutrients can negatively affect the body.
Question 36.
Observe the process of fertilization in plants:
a) Which part of the flower develops into the seed after fertilization?
b) What is the function of the Pollen tube?
c) How is the Zygote formed?
Answer:
a) Ovule
b) To transport male gametes (nuclei) into the ovary/ovule.
c) The fusion of one male gamete with the egg cell forms the Zygote.