Lesson Twenty: Abiotic and Biotic factors of an Ecosystem

• Outcome
• Starter Activity (5-7 minutes)
• Group Work
• Abiotic factors
• Biotic factors or biotic interactions
• Assessment Questions

Outcome

• Distinguish between abiotic and biotic components of an ecosystem.
• Explain some of the abiotic factors that affect the distribution of organisms.
• Explain some of the biotic factors that affect the distribution of organisms.

Starter activity (5-7 minutes)

Thinking about Ecosystems

Let the students make a connection in the relationship between living and nonliving components of an ecosystem. Students are introduced to the terms abioticandbioticin place of “nonliving” and “living” parts of an ecosystem. They also use the term habitatin place of “environment” and begin to think about organisms living together and interacting in a “community.

As an example of what students already know about the interactions of biotic and abiotic factors in the environment, ask questions related to air, water, soil etc.  

Let’s list some abiotic factors that you depend upon. For example, What two abiotic components you need each day?  It is clear that oxygen and water are necessities for our existence. We need oxygen every minute to survive. Also, we need water on a daily basis.

The teacher is expected to guide students to think about various types of habitats. To get them to think beyond, remind them that a habitat is a place where interactions take place between abiotic and biotic components.

Group Work

1. Let the students in small groups describe an interaction that might occur between living and non-living components in the environment. Their answers should be supported with evidence that the interactions had taken place.
2. Let the students in small groups describe an interaction between two or more living components of an ecosystem. Their answers should be supported with evidence.

Abiotic factors

Abiotic factors include all the non-living components of the environment, e.g., sunlight, temperature, air, water and soil. Abiotic factors are grouped into climatic, edaphic, physiological factors.

• Climatic factors – temperature, water, light and gases.
• Edaphic factors – soil types, pH and humus content.
• Physiological factors – aspect (position of the area in relation to the sunlight), slope and altitude.

Biotic factors or biotic interactions 

In nature populations of different species in a habitat do not live in isolation but interact in many ways. Depending on the outcome, these interactions between two species are classified as competition (both species suffer), predation and parasitism (one benefits and the other suffers), commensalism (one benefits and the other is unaffected), amensalism (one is harmed, other unaffected) and mutualism (both species benefit). Predation is a very important process through which trophic energy transfer is facilitated and some predators help in controlling their prey populations.

Fig. 20.1: Components of an Ecosystem.

Assessment Questions

1. Classify the factors in the picture as either biotic factors or abiotic factors by listing them in the space provided.

   
   Fig. 20.2: Biotic and Abiotic components of an Ecosystem

2. Ask students to consider and discuss what effect(s) a decrease in one of the biotic and\or abiotic factors might have on the population.  Have students select one of the organisms in their food chain and determine how it could serve as a limiting factor.  Be sure to include abiotic factors such as temperature, amount of water, and shelter.
3. Conduct an ecological study of a local habitat (e.g. school compound or nearby pond) and identify the biotic or living and abiotic or non-living components in a habitat. This activity might be done in an extra time.