Chapter 8 How do Organisms Reproduce Solutions
Question - 1 : - What is the importance of DNA copying in reproduction?
Answer - 1 : - DNA – Deoxyribonucleic acid is the genetic material that is present in the cells of all organisms. DNA carries genetic information from one generation to the other and this helps in producing organisms of its own types. DNA copying is a must for inheriting the traits from parents. Any variations in DNA copying will give rise to origin of new species.
Question - 2 : - Why is the variation beneficial to the species but not necessarily for the individual?
Answer - 2 : - The reason why the variation is beneficial to the species than individuals is because sometimes the climatic changes have a drastic effect on the species, which makes their survival difficult. For examples, if the temperature of the water body increases, then there might be certain species of microorganisms which might die. This may result in disturbance in the environment. So, variation is beneficial to species and not for the individuals.
Question - 3 : - How does binary fission differ from multiple fission?
Answer - 3 : -
When a single cell divides into two equal halves, it is known as binary fission. Bacteria and amoeba are the examples of binary fission.
When a single cell divides into multiple daughter cells at the same time, it is known as multiple fission. Algae and sporozoans are the examples of multiple fission.
Question - 4 : - How will an organism be benefited if it reproduces through spores?
Answer - 4 : -
Following are the ways through which an organism will be benefited if it reproduces through spores:
• Number of spores produced in one sporangium would be large.
• In order to avoid competition at one place, spores can be distributed to faraway places with the help of air.
• In order to prevent dehydration under unfavorable conditions, the spores are covered by thick walls.
Question - 5 : - Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Answer - 5 : - Organisms at higher complex levels cannot give rise to new individuals through regeneration because they have organization of their organs system at different levels. All these organ systems are interconnected and work in full coordination. They can regenerate a few of their lost body parts like skin, blood, muscles, etc. but can’t give rise to new individuals.
Question - 6 : - Why is vegetative propagation practised for growing some types of plants?
Answer - 6 : -
Following are the advantages of practising vegetative propagation for growing some types of plants:
• Crops like orange, banana, pineapple do not have viable seeds, so vegetative propagation can be used.
• It is a rapid, cheap and easier method to grow crops.
• It can be used in places where seed germination fails.
• A good quality of variety can be preserved.
Question - 7 : - Why is DNA copying an essential part of the process of reproduction?
Answer - 7 : - DNA copying is an essential part of the process of reproduction because it carries the genetic information from the parents to offspring. A copy of DNA is produced through some chemical reactions resulting in two copies of DNA. Along with the additional cellular structure, DNA copying also takes place which is then followed by cell division into two cells.
Question - 8 : - How is the process of pollination different from fertilization?
Answer - 8 : -
Pollination is defined as the process of transfer of pollens from anther to stigma. The process takes place with the help of pollinators like air, water and some insects.
Fertilization is defined as the fusion of male and female gametes. It takes place in the ovule and leads to the formation of zygote.
Question - 9 : - What is the role of the seminal vesicles and the prostate gland?
Answer - 9 : - Lubrication of sperms and providing of a fluid medium for the easy transportation of sperms takes place with the help of secretions from the seminal vesicles and the prostate gland. These secretions also provide nutrients in the form of fructose, calcium and some enzymes.
Question - 10 : - What are the changes seen in girls at the time of puberty?
Answer - 10 : -
Following are the changes seen in girls at the time of puberty:
• In genital area, hair growth appears.
• Hair growth in other areas like underarms, face, hands and legs.
• The size of uterus and ovary increases.
• The size of the breast increases followed by darkening of the nipple skin that is present at the tip of the breast.
• Beginning of menstrual cycle.
• Appearance of pimples, as the oil secretion is more from the skin.