Levels of Organisation

Definition of Levels of Organisation

Ecologists categorise the natural world into smaller chunks to make them easier to understand. These chunks are called the levels of organisation.

Levels of organisation can span from a singular cell to the global biosphere.

Level of Organisations Within a Population

The term population in biology refers to a group of living organisms that live in a specific geographical location at the same time. As you may notice, there are two main components: the living organisms and the geographical area they inhabit.

Wildlife populations are not contained within national borders (except in island countries!). Because of this, scientists study populations within their habitat range.

Describing Populations

Populations are typically described by their size, density, and dispersion.

Population Size

A population size refers to the number of individuals it has. It is usual for a population to fluctuate over time; many things could cause this. An increase in a population can be brought about by individuals being born or immigration (new individuals entering the population from elsewhere). A population decrease can result from individuals dying or emigration (individuals leaving the population to go elsewhere).

Population Density

Population density is often related to the size of the species - small rodents have much higher population densities than large carnivores. But as animals get larger, this change in population density becomes more extreme.

Population Dispersion

Dispersion is how individuals are spaced out within the population. Individuals can be clumped together in groups, spread out uniformly (in an even pattern), or distributed randomly with no predictable pattern.

Level of Organisations Within a Community

The next group after population in the hierarchical structure of nature is a community. A biological community refers to the collection or gathering of organisms, either from the same or different species, inhabiting a specific geographical location at the same time.

Different species that live within communities interact with each other. Some interspecies interactions are defined in this table.

One of the major properties of a community is its function. How exactly does a community filled with various species all fit together? A community function refers to the flow or transfer of energy (usually in the form of a food web) and resiliency (how a species survives and creates its own niche) within the community.

Niches

Every species in a community has its own niche. Different niches allow species to coexist in a community.

If two species occupy the same niche in a community, they will compete. Eventually, the more successful species will outcompete the other.

Food Webs

Food chains can represent the transfer of energy within a community and contain the following components:

Producers ⇨ Primary consumers ⇨ Secondary Consumers ⇨ Tertiary consumers

Consumers that kill and eat other animals are known as predators. The animals that get eaten are known as prey. Predator and prey populations are linked, rising and falling in cycles.

Food chains are linked together to form complex food webs. These can be used to understand the interdependence of species within an ecosystem.

Level of Organisation Within Ecosystems

We've learned that a community comprises all the different species populations living in an area. So, what is the next level up?

Organisms interact with their physical environment and the rest of their community. Ecologists focus on energy flow and how nutrients recycle within the ecosystem. Think of food chains feeding into larger food webs of a habitat. The predator-prey relationship was discussed in the section above. However, it also involves decomposers when talking about ecosystems.

These decomposing organisms release enzymes that break down the dead matter and are eventually consumed by the decomposers. They are essential in the Recycling process. Plants also absorb these decomposed nutrients through their roots.

Examples of Levels of Organisation

Now that we've covered populations, communities and ecosystems, let's see how they all fit together.

Individuals from one species live together in a population. The population is found within a broader community. Think about what other species might be present in that community. This information is tabulated below, with the wider ecosystems in which the species live.

Human Impact on the Different Levels of Organisation

Human activities have disrupted the natural environment. Burning Fossil Fuels has increased the concentration of carbon dioxide in the atmosphere, causing climate change. Furthermore, deforestation and land use change has led to habitat loss.

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