Basic Ecological Concepts – SS1 Biology Lesson Note (Second Term)

Ecology is the study of plants, animals and microorganisms in relation to their environment.

Behavioural objectives

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

1. define ecology and state what ecological studies involve;
2. distinguish between autecology and synecology;
3. explain the terms environment, biosphere, habitat, ecological niche, population, community, ecosystem and biome;
4. name the three major portions of the ecosphere;
5. list the abiotic and biotic components of an ecosystem and give examples.

What is ecology?

Ecology is the study of plants, animals and microorganisms in relation to their environment.

As a practical science, ecological studies involve:

1. Distribution: studying where living organisms are found.
2. Dependence: finding out how organisms depend on one another and on the non-living environment for survival.
3. Measurement: measuring the factors that affect the environment, such as temperature, light and rainfall.

What are the branches of ecology?

Ecology has two branches: autecology and synecology, depending on whether organisms are studied alone or in groups.

• Autecology: the study of one organism, or one species, and its environment, e.g. a student and his school environment.
• Synecology: the study of the relationships between groups of organisms or different species living together in an area, e.g. fish, crabs and seaweeds in a pond.

What are the main ecological terms?

Ecological terms describe the parts of nature that ecologists study, from one organism up to the whole earth.

1. What is the environment?

The environment is the sum of all external and internal factors, living or non-living, that affect an organism or a group of organisms.

• Habitat conditions: physical conditions such as light, food, water and air.
• Predation: animals preying on other animals.
• Disease: diseases affecting the organisms.

2. What is the biosphere (ecosphere)?

The biosphere is the zone of the earth occupied by living organisms where they carry out their biochemical activities.

The ecosphere has three major portions: lithosphere, hydrosphere and atmosphere.

• Lithosphere: the solid, outermost zone of the earth, made of rocks and minerals. It forms about 30% of the earth’s surface and is the basis of human settlement.
• Hydrosphere: the liquid (aquatic) part of the biosphere. It covers about 70% of the earth’s surface.
• Atmosphere: the gaseous portion of the earth, made mainly of nitrogen, oxygen and carbon(IV) oxide.

What does the hydrosphere contain?

• Forms of water: solid (ice), liquid and gas (water vapour).
• Water bodies: lakes, pools, springs, oceans, ponds and rivers.

What gases make up the atmosphere?

3. What is a habitat?

A habitat is the place where an organism is naturally found.

Habitats are always affected by environmental factors. There are three types of habitat: aquatic, terrestrial and arboreal.

• Aquatic habitat: where plants, animals and microorganisms live in water, e.g. sea, ocean, lagoon and stream.
• Terrestrial habitat: where organisms live on land, e.g. forest, grassland (savanna) and desert.
• Arboreal habitat: tree trunks and tree tops, where some organisms, usually animals, are found.

4. What is an ecological niche?

An ecological niche is the habitat and the entire habit (behaviour, feeding and breeding) of an organism.

• Space: the physical space the organism occupies.
• Role: its functional role in the community, e.g. what it eats and what eats it.

5. What is a population?

A population is the total number of organisms of the same species living together in a habitat.

• Example: the cockroaches in the Biology laboratory.

6. What is a community?

A community is all the populations of living organisms that exist together in a habitat.

• Example: decomposers, insects and birds on a decaying log of wood.

7. What is an ecosystem?

An ecosystem is the basic functional unit in nature, made of all living factors and their interaction with the non-living factors of the environment.

• Natural ecosystem: formed without human work, e.g. a forest, a pond or an ocean.
• Artificial ecosystem: made and kept by people, e.g. a farm, a garden or an aquarium.

8. What is a biome?

A biome is a large natural terrestrial ecosystem, a plant and animal community produced and maintained by the climate.

• Examples: tropical rainforest, savanna and desert.

How do these terms fit together?

What are the components of an ecosystem?

An ecosystem has two main components: the abiotic (non-living) and the biotic (living) components.

1. What are abiotic components?

Abiotic components are the non-living basic elements and compounds of the environment in which an organism lives.

• Organic substances: carbohydrates, lipids and proteins.
• Inorganic substances: carbon(IV) oxide (CO₂) and water (H₂O).
• Climatic factors: light, temperature and rainfall.
• Edaphic factors: soil type, soil texture and topography.

2. What are biotic components?

Biotic components are the living things in the ecosystem: producers, consumers and decomposers.

• Producers: autotrophs that make their own food from simple inorganic substances, e.g. green plants, protophytes and chemosynthetic bacteria.
• Consumers: heterotrophs that feed on producers or on one another, e.g. goats, grasshoppers, lizards and lions.
• Decomposers: saprophytes that break down the remains of plants and animals and release nutrients into the soil, e.g. fungi and some bacteria.

What are the levels of consumers?

• Primary consumers: feed directly on producers, e.g. grasshopper.
• Secondary consumers: feed on primary consumers, e.g. lizard.
• Tertiary consumers: feed on secondary consumers, e.g. snake or hawk.

How do living things influence one another?

• Feeding (parasitism): one organism feeds on another and harms it.
• Shading: tall plants block sunlight from smaller plants.
• Pollination: insects and other animals carry pollen between flowers.
• Seed dispersal: animals carry seeds to new places.
• Competition: organisms struggle for food, water, light or space.

Some of these influences are favourable to an organism, while others are unfavourable.

Evaluation

1. Define ecology.
2. State the difference between autecology and synecology.
3. Name the three types of habitat and give one example of each.
4. List the three main gases in the atmosphere.
5. Name the three kinds of biotic component of an ecosystem.

Assignment

Answer all the questions below in your exercise book.

1. Which of the following is not classified as a terrestrial habitat? A. forest B. guinea savanna C. littoral zone D. desert
2. The activities of an organism which affect the survival of another organism in a habitat can be described as A. biotic factors B. abiotic factors C. climatic factors D. edaphic factors.
3. The number of individuals of the same species interacting in a habitat at a particular time is best described as A. community B. ecosystem C. population D. biome.
4. A biotic community with its physical environment (abiotic factors) defines A. ecosystem B. population C. habitat D. biosphere.
5. The most abundant gas in the atmosphere is A. oxygen B. nitrogen C. carbon dioxide D. a rare gas.
6. Define: (i) biotic community, (ii) habitat, (iii) ecosystem.
7. Write short notes on the three major portions of the ecosphere.