Climate & Climate Classification II – SS2 Geography Lesson Note (First Term)

An ecosystem is a community of plants and animals living together and interacting with their physical environment. It has living (biotic) and non-living (abiotic) components that depend on one another. The Earth’s environment is made up of four spheres: lithosphere, hydrosphere, atmosphere and biosphere. Environmental balance keeps matter recycling and energy flowing.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Name the four spheres of the environment and describe each one.
2. Define an ecosystem.
3. Identify the abiotic and biotic components of an ecosystem.
4. Explain interdependence within the ecosystem, with examples.
5. State the processes through which environmental balance is achieved.

What are the spheres of the environment?

The Earth as an environment is grouped into four spheres:

1. Lithosphere: The solid portion of the environment, which contains rocks, sand, soil, minerals etc.
2. Hydrosphere: The liquid portion of the environment, such as rivers, lakes and oceans.
3. Atmosphere: The gaseous portion of the environment, where gases like oxygen, nitrogen, carbon dioxide and ozone are found.
4. Biosphere: The portion of the environment where plants and animals are found.

These four spheres of the environment are interrelated and interdependent.

What is an ecosystem?

An ecosystem is a community of plants and animals living together in harmony and interacting with their physical environment.

In other words, an ecosystem is the relationship that exists between living things and their non-living environment.

What are the components of an ecosystem?

The ecosystem is made up of two main components:

1. Abiotic (non-living) component: Soil, water, gases, sunlight etc. in the environment.
2. Biotic component: The living component of the ecosystem. It includes plants and animals.

Groups of biotic components

Biotic components can be grouped into three:

1. Autotrophs: These are also called the producers. They include the green plants, which manufacture their food through a process known as photosynthesis.
2. Heterotrophs: These are called primary and secondary consumers. They cannot manufacture their food but depend directly or indirectly on plants for their food, e.g. man, parasites and saprophytes.
3. Decomposers: These are microorganisms that decompose dead organic matter to release nutrients required by producers to prepare their food, e.g. fungi and bacteria.

Components of the ecosystem as a whole

Taken as a whole, the components of an ecosystem can be grouped into the following:

• Land (soil)
• Water (lakes, oceans)
• Plants
• Animals
• Drainage (rivers)
• Climate (atmosphere)

What is interdependence within the ecosystem?

Interdependence is the word used to describe the relationship between the components of the ecosystem. Components in an ecosystem depend on one another and cannot exist in isolation. A state of interdependence within the ecosystem is best achieved where the components are undisturbed.

Interdependence in an ecosystem exists in three ways:

1. Interdependence within abiotic components, e.g. the weathering of rock to form soil or the evaporation of water to form clouds.
2. Interdependence within biotic components, e.g. animals depend on plants for food, or plants and animals exchange oxygen and carbon dioxide.
3. Interdependence between the biotic and abiotic components, e.g. plants depend on soil for support and nutrients, and autotrophs convert sunlight energy, water and carbon dioxide into food during photosynthesis.

What is environmental balance?

Environmental balance refers to the ways of recycling matter and the flow of energy within an ecosystem to ensure continuous supply or availability.

Environmental balance is achieved through the following processes:

1. Hydrological (water) cycle
2. Carbon cycle
3. Nitrogen cycle
4. Mineral nutrient cycle
5. Food chain and food web

Evaluation

1. Name the four spheres of the environment.
2. Define an ecosystem.
3. State the two main components of an ecosystem and the three groups of biotic components.
4. Give one example of interdependence between biotic and abiotic components.
5. List the processes through which environmental balance is achieved.

Assignment

1. The height of a place above the sea level is known as (a) Latitude (b) Altitude (c) Lapse rate (d) Spot height
2. Which of these factors does not affect weather and climate? (a) Cloud cover (b) Humidity (c) Latitude (d) Natural vegetation
3. The instrument used for measuring wind direction is (a) Wind vane (b) Thermometer (c) Anemometer (d) Rain gauge
4. Wet and dry bulb thermometers could be used for measuring (a) Rainfall (b) Relative humidity (c) Temperature (d) Wind speed
5. Which of the following weather elements is paired with the wrong instrument? (a) Wind direction and wind vane (b) Humidity and anemometer (c) Rainfall and rain gauge (d) Atmospheric pressure and barometer