Questions
Q1. Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
Answer:
In multi-cellular organisms like humans, all cells are not in direct contact with the surrounding environment. Diffusion is a slow process and can only transport oxygen over short distances. Since human bodies have many layers of cells and tissues, oxygen cannot reach all cells quickly enough through diffusion alone. Therefore, specialized respiratory and circulatory systems are needed to transport oxygen efficiently throughout the body.
Q2. What criteria do we use to decide whether something is alive?
Answer:
We use several criteria to decide whether something is alive: (i) Movement – either visible or molecular; (ii) Growth over time; (iii) Respiration – exchange of gases; (iv) Nutrition – intake of food; (v) Excretion – removal of waste products; (vi) Response to stimuli; (vii) Reproduction. However, the most fundamental criterion is the presence of molecular movements necessary for maintaining life processes, as even organisms that appear still are alive due to internal molecular activities.
Q3. What are outside raw materials used for by an organism?
Answer:
Organisms use outside raw materials for two main purposes: (i) As a source of energy – food provides energy for various life processes like growth, repair, and maintenance. (ii) For body building and growth – raw materials like carbon, nitrogen, phosphorus, iron, magnesium, etc. are used to synthesize proteins, carbohydrates, fats, and other compounds needed for the organism's structure and function.
Q4. What processes would you consider essential for maintaining life?
Answer:
The essential processes for maintaining life are: (i) Nutrition – to obtain food and energy from outside; (ii) Respiration – to break down food and release energy; (iii) Transportation – to carry food, oxygen, and wastes throughout the body; (iv) Excretion – to remove harmful waste products from the body; (v) Control and coordination – to regulate body functions; (vi) Growth and repair – to maintain and build body structures; (vii) Reproduction – to produce offspring, though not essential for survival of an individual organism.