The natural environment

The natural environment consists of all living and non-living things that occur naturally on Earth. This includes air, water, animals, plants, micro-organisms, stones, clouds, and rocks.

Importance of the natural environment

The natural environment is important because:

• It is a source of food for organisms.
• It provides shelter and security.
• It creates suitable conditions for reproduction and growth.
• It allows interaction between living and non-living things.

Natural environment

Common terms in studying the natural environment

Biotic factors

These are all the living components of the environment such as plants, animals, and micro-organisms.

Abiotic factors

These are the non-living components of the environment, for example, light, water, rocks, and soil.

Ecology

This is the branch of biology that studies the relationship between living organisms and their natural environment.

Population

The total number of individuals of a particular species in a given area.

Example: Number of frogs in a pond.

Community

A group of different populations living in the same habitat.

Example: Grassland community – grass, acacia trees, lions, antelope, giraffes, and cheetahs.

Habitat

A specific area with suitable conditions where a particular community lives.

Example: Tropical rainforest, desert, swamp, pond, grassland, ocean.

Ecosystem

A natural unit made up of living and non-living things whose interactions form a self-sustaining system.

Components of an ecosystem

A. Biotic factors

These include both population and community factors.

Population factors

1. Population density: Number of organisms in a given area.
2. Dispersion: Geographical distribution.
3. Age structure: Age distribution of a population.
4. Sex ratio: Ratio of males to females.
5. Birth and death rates.
6. Population growth: Increase in number of individuals.

Community factors

• Include food chains and food webs which show feeding relationships and energy flow within a community.

B. Abiotic factors

These are the non-living parts of the environment and are divided into:

1. Climatic factors

Temperature

The degree of heat. Organisms adapt differently:

1. Some plants shed or roll leaves to reduce water loss.
2. Cold-climate animals have extra fat for insulation.

Light

Light comes from the sun and is important for photosynthesis.

• Some animals hunt in daylight (e.g. hawks), dusk (e.g. lions), or night (e.g. owls).

Wind

1. Increases evaporation.
2. Helps in seed dispersal and formation of rain.

Atmospheric pressure

1. Affects gas exchange and respiration.
2. Influences distribution of organisms.

Water

• Acts as a habitat, solvent, and temperature buffer.

2. Aquatic factors

Salinity

The amount of dissolved salts:

• Freshwater and saltwater organisms adapt differently.

Wave action

• Affects organisms in tidal zones such as crabs, seaweeds, and shrimp.

3. Soil factors

Soil texture

Refers to the particle size (sand, silt, clay). It affects drainage and fertility.

Soil composition

Includes air, water, mineral salts, micro-organisms, and organic matter – influences fertility.

Soil pH

1. Refers to acidity or alkalinity.
2. Tomatoes and pineapples prefer slightly acidic soil.
3. Onions and cabbage prefer slightly alkaline soil.

4. Geological factors

Altitude

1. Higher altitude = lower temperature and pressure, higher rainfall.
2. Affects the type of vegetation and animals found.

Geological substratum

• Type of parent rock influences soil chemistry and fertility.

Slope

1. Refers to land gradient:
   • Steep slopes have more erosion → less fertile.
   • Gentle slopes retain topsoil → support more plants.