Life Processes

Lesson

Part 1 — what keeps living things alive, how green plants make their own food, and how animals, including you, digest food.

In this lesson you will

List the basic life processes and explain why they are needed to maintain life
Describe the events of photosynthesis and the roles of chlorophyll and stomata
Compare autotrophic and different kinds of heterotrophic nutrition
Trace the path of food through the human alimentary canal and state the role of each digestive juice

Concept

What are life processes?

Living things are highly organised. Keeping that order needs energy and raw materials all the time, even at rest. The processes that perform this maintenance are the life processes.

Table of the four life processes with what each does and how it happens in humans and plants
Life process	What it does	In humans	In plants
Nutrition	Takes in food for energy and growth	Eating and digestion	Photosynthesis
Respiration	Breaks down food to release energy	Breathing and cell respiration	Cell respiration; gas exchange through stomata
Transportation	Carries materials around the body	Blood and lymph	Xylem and phloem
Excretion	Removes harmful wastes	Kidneys	Leaves, bark, vacuoles

Concept

Why large organisms need special systems

In a single-celled organism every part touches the surroundings, so diffusion is enough. In a large, multicellular organism most cells are far from the surface, so diffusion is too slow: it needs specialised organs for nutrition, breathing, transport and excretion.

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