Question 1: Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans ?
Answer: In multicellular organisms like humans, all the body cells are not in direct contact with the surrounding environment. Therefore, every cell of the body will not get oxygen as per need by the process of diffusion from the environment. Therefore diffusion is insufficient to meet the oxygen requirements of multicellular organisms.
Question 2: What criteria do we use to decide whether something is alive ?
Answer: The main criteria used to decide whether something is alive are breathing and respiration. However, living beings also show growth and movement.
Question 3: What are outside raw materials used by an organism ?
Answer: Any organism uses organic molecules as raw material. Heteroptrophs use food and autotrophs use carbon dioxide, minerals, water and all organisms use oxygen (for respiration) as raw materials.
Question 4: What processes would you consider essential for maintaining life ?
Answer: Processes essential for maintaining life are :
(i) Nutrition
(ii) Respiration
(iii) Transportation
(iv) Excretion
Question 5 : Where do plants get each of the raw materials required for photosynthesis ?
Answer:
(i) Carbon dioxide : Plants get carbon dioxide from the environment/atmosphere through stomata.
(ii) Water : Plants absorb water from the soil through roots and transport to leaves.
(iii) Sunlight : Plants get sunlight from the sun.
(iv) Chlorophyll : It is present in chloroplast found in green leaves and green parts of plants.
Question 6: What is the role of the acid in our stomach ?
Answer: Role of acid in our stomach is :
(i) To make acidic medium which is necessary for the activation of the enzyme pepsin.
(ii) To kill bacteria which the food may contain.
Question 7: What is the function of digestive enzymes ?
Answer: The food we eat is complex in nature, i.e., it contains complex molecules. Digestive enzymes break down these complex molecules into smaller simpler molecules so that they can be absorbed by the walls of the intestine.
Question 8: How is the small intestine designed to absorb digested food ?
Answer: The small intestine is designed to provide maximum area for absorption of digested food and its transfer into the blood for its circulation into the body. For this the inner lining of the small intestine has numerous finger-like projections called villi. The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body.
