7.2.1 Levels of Organisation

Levels of Organisation in Ecosystems

1. Producers

• Role: They convert light energy into chemical energy by making glucose, which is then used to create other biological molecules. These molecules form the biomass that provides energy for other organisms in the food chain.

2. Primary Consumers

• Energy Transfer: When primary consumers eat producers, they obtain the energy stored in the biomass of the producers.

3. Secondary Consumers

• Predator-Prey Relationship: In this level, the animals that are eaten are called prey, and the animals that hunt and eat them are known as predators.

4. Tertiary Consumers

• Top Predators: In some ecosystems, tertiary consumers are the apex predators, meaning they have no natural predators.

Studying Ecosystems

To determine the distribution (where organisms are found) and abundance (how many of them there are) of species in an ecosystem, ecologists use specific tools:

• Transects: Lines along which samples are taken at regular intervals to study changes in an ecosystem.

  

• Quadrats: Square frames used to isolate a standard unit of area for study of the distribution of organisms.

  

Data Analysis

• Once data is collected using transects and quadrats, it can be analysed by calculating statistical measures such as the mean, mode, and median.
• Results are often represented graphically to show patterns of distribution and abundance.

Population Cycles in Stable Communities

In a stable community, the populations of predators and prey often follow cyclical patterns:

• Increase in Prey Population: Leads to an increase in predator numbers as more food becomes available.
• Decrease in Prey Population: As predators consume more prey, the prey population decreases over time.
  • Decrease in Predator Population: When prey becomes scarce, the predator population declines due to lack of food.
  • Recovery of Prey Population: With fewer predators, the prey population can begin to increase again. This cyclical relationship helps maintain balance within ecosystems.

Population cycle