The Characteristics of Life

Types of living things:

1. Plants
2. Animals
3. Fungi
4. Bacteria
5. Other e.g amoeba-single celled organisms found in water

Key Definitions

Metabolism	The sum of all the chemical reactions in an organism. It is controlled by enzymes.
Catabolic reaction	The breakdown of larger molecules into smaller molecules e.g. digestion.
Anabolic reaction	The use of smaller molecules to form larger molecules e.g. photosynthesis, protein synthesis.
Continuity of life	Living organisms arise from other living organisms of the same species.
Life	An organism which shows metabolism and continuity of life.

Characteristics of living things

1. Organisation
2. Nutrition
3. Respiration
4. Excretion
5. Reproduction
6. Response

1. Organisation

The ordered way in which living things are arranged structurally.

7. Cell

• The basic building block of all living organisms.
• Some organisms are unicellular (consist of one cell e.g. amoeba).
• Some organisms are multicellular (consists of many cells).

8. Tissue: A group of cells working together to perform a shared function e.g. muscle tissue.
9. Organ: A structure made up of groups of different tissues, working together to perform specific functions e.g. liver.
10. Organ system: A group of organs with related functions, working together to perform a bodily function e.g. the digestive system.

2. Nutrition

• Nutrition: The way in which an organism obtains and uses food.
• Autotrophic: organisms that produce their own food e.g. plants produce their food through photosynthesis.
• Heterotrophic: organisms that cannot make food and must use food made by other organisms, e.g. animals, fungi.

3. Respiration

Respiration: The release of energy through the breakdown of food.

4. Excretion

Excretion: The removal of metabolic waste from the body e.g. carbon dioxide is excreted through the lungs.

5. Reproduction

• All life develops from living things.
• Sexual reproduction: joining of two gametes.
• Asexual reproduction: the splitting of an organism.

6. Response

• Response: The way in which living organisms detect and respond to changes in their environment (stimuli).
• Animals use their muscles and glands to respond to stimuli e.g.. light-sight etc
• Plants show growth tropisms

Plants Growth Tropisms:

1. Phototropism**:** plant response to light.
2. Geotropism**:** plant response to gravity.
3. Thigmotropism**:** plant response to touch.
4. Chemotropism**:** plant response to chemicals.
5. Hydrotropism: plant response to water.