Functions of life

Question 1

Maintaining Boundaries

Answer 1

All living organisms have an internal environment separated from the surrounding external environment by a boundary.
Thus cells are surrounded by a selectively permeable membrane and the whole body is covered by the integumentary system.

Question 2

Movement

Answer 2

The skeletal system provides a bony framework that the skeletal muscles pull on as they work.
Movement also occurs where smooth muscles move substances such as blood and food through tubes of the cardiovascular and digestive systems.

Question 3

Responsiveness or Excitability

Answer 3

This relates to the ability to recognise and respond to changes in the internal or external environment e.g. rising carbon dioxide levels in the blood.
All body cells are excitable to some extent; however the nerve cells are highly excitable

Question 4

Digestion

Answer 4

This is the breaking down of ingested nutrients into simple molecules that can be absorbed into the blood or lymph.
It includes mechanical digestion e.g. chewing and chemical digestion by enzymes e.g. pepsin.

Question 5

Metabolism

Answer 5

This is regulated by hormones secreted by endocrine glands e.g. thyroid gland. Metabolism refers to all chemical reactions in the body. It includes catabolism (breaking nutrients down), anabolism (building more complex substances) and cellular respiration (the production of ATP).

Question 6

Excretion

Answer 6

This is the process of removing wastes from the body.

Organs of excretion include the digestive system (faeces), skin (sweat), lungs (exhaled air) and the kidneys (urine).

Question 7

Reproduction

Answer 7

This occurs at both the cellular and organisational level.

The ability to perform cellular reproduction varies between tissues e.g. epithelium requires a fast turn over.

Question 8

Growth

Answer 8

Growth occurs where an individual cell of body part increases in size.
At the cellular level growth is essential before cell division can occur.
At the higher levels growth can only occur where there is an increase in cell number.

Question 9

Survival Needs

Answer 9

The ultimate goal of all the body systems is to maintain life; in order to do this we have survival needs:

• Nutrients
• Oxygen
• Water
• Normal Body Temperature
• Appropriate Atmospheric Pressure.