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Ecology: Definition, Types, Importance & Examples

Understanding these interactions between organisms and the natural world around them is crucial for understanding the organisms themselves as well as how ecosystems form.

The study of all of this is called ecology.

Definition and Importance of Ecology

Ecology is the study of relationships between organisms and their physical surroundings. This includes how organisms interact with each other (beetle eats grass, bird eats beetle, beavers cut down trees, worms decompose dead plants) and how organisms interact with their physical environment (meerkats create tunnels in the ground, fish live in certain types of water, plants grow towards the sunlight).

Why is this so important? Well, the study of ecology and ecological systems can teach us about how organisms interact with each other and with the natural world. It can teach us why organisms live in certain areas; it can teach us how changes to a physical environment (such as climate change, newly introduced organisms, natural disasters, human interference) will affect organisms and the natural world in an ecosystem.

In short, ecology is the study of the relationships between everything in the biosphere. It teaches us how all organisms on Earth interact with each other and the Earth around them, which reveals:

  • How ecosystems form.
  • How and why organisms act/behave/distribute as they do.
  • How we as humans are affecting the world around us. 

It can help us understand conservation biology, invasive species, climate change and more.

Key Ecology Terms to Know

Within the scientific study of ecology, there are a few important terms to know:

Biotic factors and abiotic factors. Biotic factors refer to living (or things that once were living) organisms in a particular environment. These could be things like:

  • Trees.
  • Grass.
  • Animals.
  • Fungi.
  • Bacteria.

Abiotic factors, on the other hand, refer to non-living or physical factors in the environment. These could be things like:

  • Sunlight.
  • Availability of water.
  • Soil composition.
  • Temperature.
  • Air quality.

Both biotic and abiotic factors are important components of ecology as they can affect what organisms live in certain environments, the distribution of those organisms and the number of organisms the area can support.

Biosphere. The biosphere, first coined by geologist Eduard Suess, refers to all life on Earth. This includes the lithosphere (rock), the atmosphere (air) and the hydrosphere (water).

Population. A population is a group of individual organisms within the same single species living in the same general area. An example of a population would be all of the clownfish living in a particular coral reef, all of the daisies in a field or all of the E. coli found in a puddle of water.

Community. A community refers to all of the populations of different species that live in a particular environment or habitat in the same area. A forest community, for example, would include all of the deer, trees, bees, ticks, foxes, wolves, moose, squirrels, moss, mold, mushrooms and flowers that exist in that forest.

Ecosystem. This includes the community of organisms and their physical environment, as well as both biotic and abiotic factors.

Ecological niche. Within an ecosystem, different organisms will fill a certain role or job that's referred to as their "niche." It categorizes each individual and single species or organism in a community in a specific role that allows the ecosystem (and that single species) to exist.

This can depend on their role in the food chain or food web, the conditions they need to survive (sunlight, water type, shelter, nutrients) and necessary interactions with other organisms (such as parasites or mutualism).

Types of Ecological Science and Ecological Studies

For each of the above key ecology terms, you'll find a specific subset of ecological science that focuses on the study of that term. "Ecology" refers to the general study of the relationships of organisms and their interactions with each other and the environment. Each of the following ecological studies look at particular and specific aspects.

Molecular ecology. Molecular ecology is the smallest scale of ecological studies. Molecular ecologists mainly focus on DNA and proteins that organisms produce, how they affect the environment they live in and how the environment affects that DNA and protein production. These ecologists may also look at factors such as gene flow, genetic drift in populations, co-evolution and genetic diversity within populations.

Organismal Ecology. Organismal ecological studies focus on specific, individual organisms. Scientists will examine very particular organisms and all of their specific interactions with their physical environment and other organisms.

Zoologists, for example, are organismal ecologists that study animals. Many will pick a single species of animals, like scientists who study killer whales specifically, for example, or some may look at groups of species, like scientists who study sharks in general. They may study animal behavior, animal interactions with biotic and abiotic factors and how these factors change or affect those behaviors.

However, it isn't just the study of animals. Any organism can be studied within organismal biology including bacteria, fungi and plants.

Population ecology. Population ecology is the study of how both biotic and abiotic factors affect population size, population growth, population density and dispersion of populations of organisms. Scientists often will study populations and how these specifics of the population change over time and are affected by changes in:

  • Climate.
  • Atmosphere.
  • Temperature.
  • Other populations.

For example, scientists studied deer and wolf populations in Yellowstone National Park after wolves were reintroduced into the area. They saw how the wolf population increased over time and the deer population was controlled (and decreased) over time.

Another example would be scientists studying the population of certain algae species in coral reefs. Many species have seen a huge decrease in population size and density in coral reef communities as time goes on, which many attribute to climate change.

Community ecology. Very similar to population ecology, community ecology looks at the overall structure and organization of various communities including both biotic and abiotic factors.

This often results in the construction of food webs and food chains to relate various organism populations to each other. Scientists will also look at species richness, species diversity and different species interactions, and these categories help specify each species' ecological niche within the community.

Community ecological research may also examine how changes to the environment and other species affect the community structure, including invasive species, ecological succession events, natural disasters, climate change and more.

Ecosystem ecology. As you might have noticed, each of these subsets of ecology are getting broader with each one we go over. Ecosystem ecology looks at the broadest and largest scale of interactions between communities, populations and species in their ecosystem.

Often, scientists will examine complex cycles and systems and how they affect communities and populations. For example, ecosystem ecological research can examine:

  • Nutrient cycles of carbon and carbon dioxide.
  • The nitrogen cycle.
  • The water cycle.
  • Weather patterns.

These studies and practices are applied all around the world from the United States to Canada to all of North America to Asia, etc.

Human ecology. You also might have noticed that "climate change" has come up quite a few times. That's because human activity and our effect on the Earth and the ecosystems within it has a lot to do with our impact on climate and climate change.

There's a subset of ecology called "human ecology" that looks more in depth at how humans and human activity in particular affect the ecosystems, communities and populations around us. This could be through:

  • Our land-use.
  • Our use of natural resources.
  • Deforestation.
  • Burning of fossil fuels.
  • Introduction of invasive species.

Human ecological research can also refer to the study of how humans evolved, how human behavior evolved and how those two things affect and were affected by our environments.

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