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What is Ecology?

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Ecology Definition

Ecology is the branch of biology that studies how organisms interact with their environment and other organisms. Every organism experiences complex relationships with other organisms of its species, and organisms of different species. These complex interactions lead to different selective pressures on organisms. The pressures together lead to natural selection, which causes populations of species to evolve. Ecology is the study of these forces, what produces them, and the complex relationships between organisms and each other, and organisms and their non-living environment.

Ecology Definition (Continued)

Scientists can view ecology through a variety of different lenses, from the microscopic molecular level all the way to the planet as a whole. These different types of ecology will be discussed further on. At every level of ecology, the focus is on the selective pressures that cause evolutionary change. These pressures arise from a variety of different sources, and there are numerous methods for observing and quantifying this data. The field of ecology has a huge variety of sub-disciples. Although the types of ecology below are divided by the level of organization being viewed, some ecologists specialize in specific aspects of each field. For example, cognitive ecology is a branch of organismal ecology that studies the mental processes of animals. Other ecologists study only the interactions between humans and the rest of the biome, a field known as human ecology or environmental science. Still, other ecologists focus on the interactions between organisms and the abiotic factors that affect their evolution, such as nutrients and toxins in the environment. Ecology is a vast field, the following are only a sampling of the variety of things scientists study in ecology.

Types of Ecology

Let's learn about them.

Type #1: Molecular Ecology

At the molecular level, the study of ecology focuses on the production of proteins, how those proteins affect the organism and the environment, and how the environment, in turn, affects the production of various proteins. In all known organisms, DNA gives rise to various proteins, which interact with each other and the environment to replicate the DNA. These interactions lead to some very complex organisms. Molecular ecologists study how these proteins are created, how they affect the organism and environment, and how the environment, in turn, affects them.

Type #2: Organismal Ecology

Taking a step back, the study of organismal ecology deals with individual organisms and their interactions with other organisms and the environment. While organismal biology is a division of ecology, it is still a huge field. Each organism experiences a huge variety of interactions in its lifetime, and to study all of them is impossible. Many scientists studying organismal ecology focus on one aspect of the organism, such as its behavior or how it processes the nutrients of the environment. The field of ethology, or the study of behavior, can also be studied as ecology. Instead of just analyzing certain behaviors in animals, behavioral ecologists study how those behaviors affect the organism evolutionarily, and how the environment puts pressures on certain behaviors. For example, a behavioral ecologist might study the way that an eagle hunts for prey, noting which behaviors lead to success and which to failure. In this way, the scientist can hypothesize the forces that cause eagles to behave the way they do. This information can be very important when trying to develop conservation plans to protect animals in the wild.

Type #3: Population Ecology

The next level of organism organization, populations, are groups of organisms of the same species. Due to the wide variety of life on Earth, different species have developed many different strategies for dealing with their conspecifics, or organisms of the same species. Some species directly compete with conspecifics, while other organisms form close social bonds and work cooperatively to secure resources. A branch of ecology, social ecology, studies organisms like bees and wolves, which work together to provide for the colony or pack. The complex interactions between these organisms and their environment lead to different selective forces than in animals that compete with conspecifics. In fact, scientists hypothesize that the increased success found in human society may have been what lead humans to be so communicative. Population ecologists study the populations of organisms and the complex interactions they have with the environment and other populations.

Type #4: Community Ecology

Different populations that live in the same environment create communities of organisms. These communities create niches, or various spaces, for organisms to occupy. For instance, several niches can be found in a wheat field. The wheat exists on the sun’s rays and the nutrients in the soils. Various insects live off of the nutrients collected by the wheat. Certain bacteria occupy a niche in the roots, where they convert nitrogen for the plant. Community ecologists study these complex interactions and the selective pressures they produce. Sometimes, organisms in communities will begin to experience coevolution where 2 or more species both evolve in response to each other. This can be seen in many species, from bees and the flowers they pollinate to predators and the prey they eat.

Ecosystem Ecology

The largest scale of organismal organization is the ecosystem. An ecosystem is a network of interconnected biological communities. The largest ecosystem, the biosphere, encompasses all ecosystems inside of it. Ecosystem ecologists study the complex patterns produced by interacting ecosystems and the abiotic factors of the environment. They may study water, nutrients, or other chemicals that cycle through the ecosystem. Ecosystem ecology is a very complex and large-scale science that includes many disciplines.

Examples of Ecology

Let's learn about them.

Human Ecology

Some ecologists study humans, their effect on each other and other organisms, and their effects on the environment. Humans create an enormous impact on the globe, and some constructions can be seen from space. Some ecologists study this phenomenon, and the possible effects it could have on the biome. Other ecologists study human behavior, where it came from, and the evolutionary pressures that lead to it. Also, a discipline needed in anthropology, human ecology is a giant field that analyses human evolution and our interaction with nature.

Niche Construction in Termites

Ecologists of many different specialties study niche construction, or process by which organisms alter their environment. An example of this is niche construction in termites. Termites build mounds that stands over 6 feet tall and can go much deeper underground. To get oxygen to the inner parts of the next, termites form the nest the keep air flowing deep underground. This behavior can be studied in many ways. In evolutionary ecology, they would look at the proteins that cause the termite to build nests, and how they change over time in response to different environments. In community ecology, scientists might study how termite mounds affect the surroundings, and how they change in response to the environment. In ecosystem ecology, the focus might be on the nutrients the termites recycle underground to support the nearby trees. Although the scope is huge, all of the different aspects are considered the ecology of termites.

Related Biology Terms

  • Primary Production – The process of converting inorganic energy, such as sunlight, into biological energy, usually glucose.

  • Niche – A role or position that a creature can role within an ecosystem.

  • Nutrient cycling – The process through which different elements pass from organism to organism, and are used in different ways or returned to the environment.

  • Biosphere – The sum of all ecosystems on the planet, acting as one ecosystem.


1. A scientist is studying the structure of a specific protein. He writes a paper on its shape, and what molecule it changes. Is this ecology?

answer choices

A. Yes

B. No


Talking about a protein alone isn't ecology. The study of ecology deals with how organisms respond to their environment. To be ecology, the scientist would have had to discuss why the protein was important to the organism, and how it could change in response to the environment.


2. A beaver cuts down trees, drags them into a stream, and floods an area to create a pond it can live in. What is this behavior called?

answer choices

A. Habitat Destruction

B. Niche Construction

C. Forest Thinning


In this case, the beaver is changing the environment and creating a niche that was not previously there. Ecologists study this behavior to see the effects it has on other organisms and the environment as a whole.


3. An ecologist studies a pack of hyenas, and their interactions with the local lions. Which type of ecology would best describe this study?

answer choices

A. Organismal Ecology

B. Population Ecology

C. Community Ecology


This would be an example of community ecology or the study of the interactions of different populations of animals. Although they might not like it, the hyenas and the lions are part of the same community. Population ecology might study the pack behavior of the hyenas, while organismal ecology would study the interaction between single hyenas and their environment, including interactions with other hyenas.


What is an organism?

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