Q1.  Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?

Ans:-In multicellular organisms like humans the body design is very complex and the oxygen demand is quite high. The oxygen requirements of an animal cannot be met by the process of diffusion as diffusion is a very slow process.
Unlike unicellular organisms, multicellular cells are not in direct contact with the outside environment. Therefore, diffusion simply cannot meet their oxygen requirements.

Q2.  What criteria do we use to decide whether something is alive?

Ans:- The following are criteria to decide whether something is alive-

1 Nutrition: Living thing performs Nutrition for growth.

2 Respiration:- Living thing performs Respiration to produce energy in their cells.

3 Movement:- All living things do move, and that includes both animals and plants. plants also make movements, though slow and at times unnoticeable.

4 Excretion:- Living things have mechanisms of expelling and eliminating waste and toxic matters from their systems.

5 Growth:- All living things grow.

6 Reproduction:- This is the process by which new individual organisms are produced from the existing parent.

7 Sensitivity:- All living things are able to sense and respond to stimuli around them such as light, temperature, water, gravity, and chemical substances.

Q3.  What are outside raw materials used for by an organism?
Ans. Various outside raw materials used by an organism are-
i) for autotrophic organisms- $CO_{2}&space;,&space;H_{2}O&space;\;and\;&space;minerals.$
ii) for heterotrophic organisms – organic nutrients.
iii) oxygen is essential for respiration and generation of chemical energy as ATP during respiration.
an organism.
Q4.  What processes would you consider essential for maintaining life?
Ans. All processes that perform the maintenance function of living organisms are called life processes. All essential life processes for maintaining life are mentioned below—
1) Nutrition- To obtain and digest food.
2) Respiration -To obtain oxygen and break down molecules to release energy.
3) Circulation – To transport the metabolites to all parts of the body.
4) Excretion – To remove waste product of the body.