Chapter 8: Associations in Biological Communities

Keywords

1. competition
2. adaptation
3. association
4. commensalism
5. host mutualism
6. parasite
7. parasitism
8. predator
9. prey
10. resource symbiosis

By the end of this chapter, you will be able to:

a) know what competition is and describe how organisms compete in nature.

b) differentiate prey from predators and describe a predator-prey relationship.

c) understand symbiosis, mutualism, commercialism and parasitism and appreciate their roles in an ecosystem.

d) recognize the role of parasites and vectors in the transmission of common diseases (malaria, bilharzia, nagana, and sleeping sickness.

e) know the adaptations of parasites to their mode of life.

Introduction

Associations in organisms are interactions between living organisms. In this topic, you will study and appreciate that living organisms depend on between the living organisms have caused organisms to develop specific one another for food as seen in the previous chapter. These associations adaptation to be able to survive within their biological communities. members of the same species and those between different species.

In this chapter, you will research and study the different associations between include competition for resources, predator-prey relationships, symbiosis, mutualism, commensalism, and parasitism.

Competition

Competition is a relationship between organisms trying to use the same same species or between members of different species.

Activity 8.1 Discussing competition among organisms

Key question

Why do organisms compete?

What you need

Notebook

Pen

What to do 1

In your group, observe a farm or garbage pit with dense populations of organisms.

2 Note the competition taking place and use your findings to generate a meaning of competition.

3 Discuss the causes of the competition.

4 Report how the organisms behave and which seems to dominate others in terms of space occupied and food competed for.

Activity 8.2 Discussing types of competition

Key question

What are the different types of competition?

What you need Science journals on competition

Biology textbook

Computer with internet connection

Notebook

Pen

Manila paper

Marker

What to do

1 In your groups, research and discuss the different types of competition.

2 Identify and describe the types of competition.

3 Make a write-up of your findings and share it with the class.

4 Harmonise your information and pin it up on the class noticeboard.

Predator-prey relationships between different specie.

In the following activity, you will discuss the predator prey is is the type of association where one organism is fed on by the other of lationships.

8.3 Discussing predator prey relationship

Figure 8.1: Predator-prey relationship

Key question

What is a predator-prey relationship?

What you need

• Notebook

• Pen

Manila paper

Markers

What to do

1 In your pairs discuss predator prey relationships.

2 Make a write-up and share your findings with the class.

3 Harmonise your information and pin it up on the class noticeboard.

8.3 Predator and prey population curve

A predator prey curve is a graph showing the changes in the predator and prey populations with time.

What to do 1

In a pair examine the data provided and plot the predator prey population curve.

2 Describe and explain the predator prey curve.

8.4 Symbiotic relationships

This association between two living organisms of different species. In this activity, you will research and discuss the meaning and explain the examples of the symbiotic association.

THIS VIDEO EXPLAINS SYMBIOTIC RELATIONSHIPS

What to do 1

In your groups, identify the type of symbiotic relationship in each image or drawing.

2 Describe each type of symbiotic relationship giving examples.

3 Make a write-up and share your findings with the class.

4 Harmonise your work and pin it up on the class noticeboard.

8.5 Parasitism

Parasites affect humans, crops, domestic animals and other living things around them. In this activity you will research on common parasitic diseases.

Activity 8.6 Finding information about common parasitic diseases

Key question

What are the common parasitic diseases?

What you need

Computer with internet connection

Biology textbook

What to do

Notebook pen

In groups, research and discuss the meaning of:

parasite and parasitism.

parasites and vectors for malaria, bilharzia, nagana. and sleeping sickness.

mode of transmitting the diseases.

2. Make a write-up and share with the class.

3 Take note of your findings in your notebooks.

4 Harmonise information and pin it up on the class noticeboard.

Parasites have adaptations in their structure, behaviour or chemical processes that enable them find, reach and stay on or in their hosts.

In this activity you are going to role-play the adaptations of parasites to their mode of life and how humans try to prevent their transmission.

Activity 8.7 Discussing the adaptations of parasites to their mode of life and how humans try to prevent their transmission

Key question

What are the adaptations of parasites to their mode of life and how can transmission of parasitic diseases be prevented?

What you need

Notebook Biology textbook

Manila paper

Marker

Pens

Computer with internet connection connection

What to do

1 In groups research and discuss:

adaptations of parasites to their mode of life.

methods of preventing of parasitic diseases.

2 Make a write-up and share with the class.

3 Harmonise your information and pin it up on the class noticeboard.

Chapter Summary

In this chapter, you have learnt that:

1. organisms in nature engage in various associations to enhance their survival.
2. the associations may be interspecific (i.e. between individuals of different species) or intraspecific (between individuals of different species).
3. in the process parasites cause diseases to their hosts e.g.
4. measles is caused by viruses.
5. organisms in biological associations show adaptations to each other as a way of sustaining the association for their species survival.
6. mutualism where both members in the association benefit in some way e.g. nutritionally.
7. commensalism where one member benefits and the other neither benefits nor suffers harm.

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