Questions within chapter text
Q1. What is the importance of DNA copying in reproduction?
Answer:
DNA copying is essential in reproduction because it ensures that the genetic information (blueprint) of the parent is passed on to the offspring. This copying creates two copies of DNA that can be separated into new cells. It also introduces slight variations, which are important for evolution and adaptation. Without accurate DNA copying, the body design features that allow an organism to survive in its niche would not be maintained.
Q2. Why is variation beneficial to the species but not necessarily for the individual?
Answer:
Variation is beneficial for the species because it increases the chances of survival if the environment changes (e.g., temperature rise, water level changes). Some variants may be better suited to the new conditions and survive, while others may die. However, for an individual, variation may not be directly beneficial because most variations are neutral or harmful to that specific organism. The advantage is for the population as a whole over time.
Q3. How does binary fission differ from multiple fission?
Answer:
In binary fission, the parent cell divides into two equal halves (e.g., Amoeba, Leishmania). In multiple fission, the parent cell divides into many daughter cells simultaneously (e.g., Plasmodium). Binary fission produces two offspring, while multiple fission produces many offspring at once.
Q4. How will an organism be benefited if it reproduces through spores?
Answer:
Spore formation benefits an organism in several ways: (1) Spores are covered by thick walls that protect them from harsh conditions (e.g., heat, drought) until they find a favourable environment. (2) Spores are lightweight and can be easily dispersed by wind or water, helping the organism colonise new areas. (3) Many spores can be produced at once, increasing the chance of survival and spread.
Q5. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Answer:
More complex organisms (e.g., humans, mammals) have highly specialised cells organised into tissues, organs, and organ systems placed at definite positions in the body. Regeneration would require the precise reorganisation of these different cell types into the correct pattern, which is not possible from just any body part. In contrast, simple organisms like Hydra and Planaria have relatively simple body organisation and contain specialised regenerative cells that can proliferate and differentiate to form a complete organism.
Q6. Why is vegetative propagation practised for growing some types of plants?
Answer:
Vegetative propagation is practised because: (1) Plants raised by this method can bear flowers and fruits earlier than those grown from seeds. (2) It allows propagation of plants that have lost the capacity to produce seeds (e.g., banana, orange, rose, jasmine). (3) All plants produced are genetically similar to the parent plant, ensuring the desirable characteristics are preserved. (4) It is a quicker and more reliable method for growing many economically important plants like sugarcane, roses, and grapes.
Q7. Why is DNA copying an essential part of the process of reproduction?
Answer:
DNA copying is essential because it ensures that the genetic information (blueprint) is transferred from parent to offspring. The DNA contains the instructions for making proteins, which determine the body design and features of the organism. Without accurate DNA copying, the new cells would not have the necessary information to function properly. Additionally, the slight variations introduced during DNA copying are the basis for evolution and adaptation, allowing populations to survive in changing environments.