Our country is split into states, districts, cities, and so on. Within that, our towns are also organized into residential and commercial spaces. On an even smaller scale, the schools that we go to are also categorized based on locations, levels, and even classes. Within ecology, scientists also organize interactions between organisms and their environments into different groups to study them better.
The following will cover how ecological levels are organized, some examples, the different types of interactions, and how energy flows through the different levels.
Ecological levels of organization
Ecology involves studying how organisms interact with their environment. We seek to understand how living organisms are distributed and the number of living beings in each habitat.
The word ecology comes from the Greek word Oikos which means household or place to live, which Ernst Haeckel first coined.
Levels of organization in ecology help scientists generally study the anthropogenic impact, energy flow, changes in population dynamics, etc.
The biological levels we study are in order from smallest to largest are:
Organisms-> Population-> Community-> Ecosystem-> Biosphere
Scientists researching at the organismal level are interested in organisms or individuals living beings such as plants, animals, etc. They examine biological adaptations that allow specific individuals to live in particular habitats.
Populations are groups of organisms that are part of the same species living in the same habitat and time. When scientists study populations, they focus on why populations fluctuate over time.
A community comprises different species interacting in the same habitat and time. At this level, scientists are often concerned with studying interactions among species for limited resources. These interactions include parasitism, mutualism, commensalism, competition, predator-prey, etc.
Ecosystems are comprised of both living (biotic) and non-living (abiotic) factors. Abiotic components can include grass, soil, etc. Scientists at this level are concerned with how energy and nutrients cycle through organisms into and out of the environment.
Finally, the biosphere includes all the ecosystems on this planet. The biosphere consists of most of our earth, including our atmosphere and oceans.
Ecological levels of organization examples
After reviewing the different ecological levels, we can examine some examples to understand them further.
An organism is an individual plant, animal, or living being, which means a good example would be a lion, fox, or even a flower.
Populations consist of the same species, which means a good example would be a group of lions, a group of foxes, or even a group of plants.
Communities are all the species in an environment which means a good example would be lions, foxes, rabbits, and plants interacting.
Ecosystems consist of living, and non-living things in the same area, which signifies that a good example would be a grassland ecosystem made up of plants, animals, the sun, air, etc.
The biosphere consists of all living things on earth.
Figure 1: Ecological Levels of Organization. Vaia Originals.
Ecological levels interaction
You have probably noted from earlier sections that all ecological levels are interconnected. This means that there will be interactions between ecological levels.
When we talk about interactions, we usually refer to communities and ecosystems as both these levels involve more than one species of living organisms interacting.
The types of interactions ecologists most commonly study are:
| Types of Interactions | Definition & Consequences |
| Mutualism | Both species benefit positively from the interaction. |
| Competition | Both species benefit negatively from the exchange. |
| Commensalism | One species benefits and the other one remains unaffected. |
| Predation | When one species, the predator, hunts another species which we call the prey. This means that the predator benefits while the prey gets affected. |
| Parasitism | One species benefits, the parasite, while the other one or the host gets affected negatively. |
Specific examples of the interactions mentioned above are:
Aphids and ants share a mutualistic relationship. Aphids produce sugar that acts as nutrients for the ants while the ants protect the aphids from predators and parasites.
Woodpeckers and squirrels compete for the same holes to nest in, in trees overall, giving both fewer resources in the form of habitat in this case.
Goby fish live on other organisms and change colors to blend in to avoid predators. This interaction is commensalism because the organisms hosting the goby fish remain unaffected.
Owls hunt mice making their relationship a predatory one.
Lice are parasites that often occupy animal scalps, including humans. Lice suck blood and lay eggs on scalps making it itchy and can also lead to the spread of disease. This makes the relationship parasitic.
Ecological levels and energy flow
The energy flow through ecological levels occurs via a food web.
As mentioned, ecosystems are composed of all the organisms and the environment in which they interact.
A food web combines all the food chains in an ecosystem. In comparison, food chains show one line of predator-prey relationships.
Figure 2: Food chain illustrated. Vaia Originals.
Predators are animals that consume another organism, while producers or autotrophs make their own food to survive.
Plants are producers that get their energy to make food from the sun. Although, not all producers get their energy from the sun.
For example, chemoautotrophs such as sulfur bacteria get their energy from oxidizing inorganic compounds.
Consumers are heterotrophs that cannot make their own food to survive; thus, they have to get their energy from consuming either producers or other consumers.
Primary consumers feed on producers or plants, making them herbivores. For example, in a food chain, a rabbit is the primary consumer that eats the plant, making it a herbivore.
Secondary consumers are consumers that feed on primary consumers, making them carnivores. For instance, a fox is can be our secondary consumer as it preys on a rabbit.
Tertiary consumers are consumers that feed on secondary consumers, making them carnivores. Our tertiary consumer can be a lion which preys on the fox.
Decomposers are heterotrophs that break down dead organisms and organic waste for food.
This is generally not drawn in any figures because all organisms would eventually point to it when they died.
Examples of decomposers are fungi and bacteria.
Figure 3: Food Web illustrated. Vaia Originals.
Overall, food webs are more complex than food chains as they show multiple energy transfers at the community and ecosystem levels.
For example, although plants still receive energy from the sun, more animals are involved, from mice to rabbits. This is because there are multiple producers and consumers of different trophic levels in a whole ecosystem.
In an example of a food web, the rabbits, worms, and mice are in the same trophic level as primary consumers. In comparison, the owl and fox can be considered secondary consumers of their respective chains. In contrast, the lion can be viewed as a secondary consumer in the mouse chain or a tertiary consumer in the chicken chain. This shows us that energy flow through ecosystems can differ based on the interactions and exchanges between organisms and the environment we're dealing with.
Trophic levels describe an organism's place in a food web.
After understanding what food chains and food webs are, we can now move on to understanding how energy flows through the different trophic levels.
Figure 4: Trophic levels illustrated. Vaia Originals.
The energy transfer between the different trophic levels can be drawn as a pyramid. About 10% of the energy is transferred from each trophic level because the rest is lost as heat. This makes producers or trophic level 1 have the most energy.
For example, if the producers produced 10,000 Kilocalories (Kcal) of energy, then only 10% of that or 1,000 Kcal end up being stored in trophic level 2. Then 10% of 1,000 Kcal is transferred to trophic level 3 and so on for trophic level 4.
Dynamics, energy transfers, and interactions between organisms are vital because that's how we sustain life. Consumers, such as predators, get their food by eating other organisms; without these interactions, they would go extinct. Without predators, the prey population would go unchecked and proliferate, causing chaos at the lower trophic levels.
For example, if lions ceased to exist, mouse and chicken populations would grow out of control, causing the plant and worm populations to decimate.
We, humans, are also part of this planet, making us part of the ecosystem. We will eventually be affected if we do not understand how to sustain our ecosystems. We can run out of resources, such as food, water, etc., if not adequately managed, making it essential to study ecological interactions.
Ecological Levels - Key takeaways
References
- Mary Ann Clark, Matthew Douglas, Jung Choi, The Scope of Ecology, Biology 2e, 2018
- Badgley, Ecological Communities: Networks of Interacting Species, 2008
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