What is ecology?
Overview of ecology. Biotic and abiotic factors. The different levels of ecology.
- Ecology is the study of how organisms interact with one another and with their physical environment.
- The distribution and abundance of organisms on Earth is shaped by both biotic, living-organism-related, and abiotic, nonliving or physical, factors.
- Ecology is studied at many levels, including organism, population, community, ecosystem, and biosphere.
Welcome to ecology!
Have you ever hiked through a forest and noticed the incredible diversity of organisms living together, from ferns to trees to mushrooms the size of dinner plates? Or taken a road trip and watched the landscape change outside the window, shifting from oak forest to tall stands of pine to grassy plains? If so, you’ve gotten a classic taste of ecology, the branch of biology that examines how organisms interact with each other and with their physical environment.
Ecology isn't just about species-rich forests, pristine wilderness, or scenic vistas, though. Have you, for instance, ever found cockroaches living under your bed, mold growing in your shower, or even fungus creeping in between your toes? If so, then you’ve seen equally valid examples of ecology in action.
Images illustrating interactions among organisms and between organisms and their physical environment.
Upper left: mushrooms growing on a mossy log. Upper right: rolling green hills covered with wildflowers, grasses, and occasional trees. Lower left: rolling fields of dry, yellow grass with scrub-covered hills and snowy mountains in the distance. Lower right: cockroach on floorboards.
Biotic and abiotic factors
One core goal of ecology is to understand the distribution and abundance of living things in the physical environment. For instance, your backyard or neighborhood park probably has a very different set of plants, animals, and fungi than the backyard of a fellow Khan Academy learner on the opposite side of the globe. These patterns in nature are driven by interactions among organisms as well as between organisms and their physical environment.
As an example, let's go back to our shower mold. Mold is more likely to appear in your shower than, say, your sock drawer. Why might this be the case?
- Maybe the mold needs a certain amount of water to grow, and this amount of water is found only in the shower. Water availability is an example of an abiotic, or nonliving, factor that can affect distribution of organisms.
- Maybe mold feeds off of dead skin cells found in the shower, but not in the dresser. Availability of nutrients provided by other organisms is an example of a biotic, living-organism-related, factor that can influence distribution.
Case study: the red panda
Let's apply the idea of biotic and abiotic factors to another organism, one that a field ecologist might be likely to study. Red pandas are distant relatives of raccoons and are found only in the eastern Himalayas. They spend most of their time in trees and eat a primarily vegetarian diet. In recent years, the red panda population has dropped significantly, leading conservation groups to classify it as a vulnerable or endangered species.
Red panda hanging from a tree branch. It's a cute animal that looks roughly similar to a raccoon with reddish fur.
What are the main factors behind this change in abundance? Ecologists have found that biotic factors, such as logging of trees and introduction of diseases from domestic dogs, played a major role in the decline of red panda populations. Abiotic factors have been less important to date, but changing temperatures could cause further habitat loss in the future.
Understanding the main factors responsible for the decline in red panda numbers helps ecologists form conservation plans to protect the species.
How do ecologists ask questions?
To ask questions about the natural world—such as, "Why is the red panda declining?"—ecologists draw on many areas of biology and related disciplines. These include biochemistry, physiology, evolution, behavioral biology, and molecular biology, as well as geology, chemistry, and physics.
Natural historians were arguably the first ecologists—dating back to the Greek philosopher Aristotle! However, today's ecologists are rigorous, quantitative scientists. They run controlled experiments, use statistics to find patterns in large datasets, and build mathematical models of ecological interactions.
Ecology at many scales
Within the discipline of ecology, researchers work at five broad levels, sometimes discretely and sometimes with overlap: organism, population, community, ecosystem, and biosphere.
Let's take a look at each level.
- Organism: Organismal ecologists study adaptations, beneficial features arising by natural selection, that allow organisms to live in specific habitats. These adaptations can be morphological, physiological, or behavioral.
- Population: A population is a group of organisms of the same species that live in the same area at the same time. Population ecologists study the size, density, and structure of populations and how they change over time.
- Community: A biological community consists of all the populations of different species that live in a given area. Community ecologists focus on interactions between populations and how these interactions shape the community.
- Ecosystem: An ecosystem consists of all the organisms in an area, the community, and the abiotic factors that influence that community. Ecosystem ecologists often focus on flow of energy and recycling of nutrients.
- Biosphere: The biosphere is planet Earth, viewed as an ecological system. Ecologists working at the biosphere level may study global patterns—for example, climate or species distribution—interactions among ecosystems, and phenomena that affect the entire globe, such as climate change.
A flow chart of three boxes explaining the hierarchy of living organisms.
The top box contains a photograph of tall trees in a forest and is captioned, “Organisms, populations, and communities: In this forest, each pine tree is an organism. All of the pine trees living in the area make up a population. All of the populations of different species in the area form a community."
The second box contains a photograph of a body of water, behind which is a stand of tall grasses developing into more dense vegetation and trees as distance from the water increases. The photo is accompanied by the following text: “Ecosystems: This coastal ecosystem in the southeastern United States consists of a community of living organisms plus their physical environment."
The third box contains a drawing of planet Earth and is labeled, “The biosphere: The biosphere consists of all the ecosystems on Earth, considered together.
The five levels of ecology are listed above from small to large. They build progressively—populations are made up of individuals; communities are made up of populations; ecosystems are made up of a community plus its environment; and so forth. Each level of organization has emergent properties, new properties that are not present in the level's component parts but emerge from from these parts' interactions and relationships.
The levels of ecological study offer different insights into how organisms interact with each other and the environment. I like to think of these levels as magnifying glasses of different strengths. If you really want to get what's going on in a particular ecological system, you'll likely want to use more than one!
Want to join the conversation?
- Which level of ecology deals with the concept of "niche?"(12 votes)
- Niche is the role an organism has in an ecosystem. For more info, click https://www.khanacademy.org/science/biology/ecology/community-ecosystem-ecology/v/niche-bozeman (video) or https://www.khanacademy.org/science/biology/ecology/community-ecosystem-ecology/a/niches-competition (article). I think the study of niche should be in community, because it is the role it has that impacts other populations. I hope you find this helpful! :)(22 votes)
- In biotic and abiotic factor, why does dead skin cells fall under biotic instead of abiotic?(5 votes)
- This is because they were once alive, and were created by a living thing. Take an abiotic rock, for example, it was never living, never part of a living thing, and will never be. Dead skin cells, however, were once living as part of a living thing such as you. So even though those cells are dead, they are still considered biotic factors(9 votes)
- So Ecology Is basically how different things Interact with each other.(3 votes)
- Yes and no. Organisms interacting with each other are only part of Ecology. The formal definition of Ecology is the study of how life interacts with life/other living things and their environment. So, yes different things are interacting with each other, but they're also interacting with their environment, like the ocean or a forest, or a large rock.(6 votes)
- what is difference between ecology and environmental science ?!(3 votes)
- This is a great question, and I am so glad you asked! Ecology is the study of how living things interact with each other and their environment. Environmental science uses ecology, but falls on the more human end of the spectrum, focusing on conservation, sustainability, and basically how we can keep the environment going.(5 votes)
- What are examples of emergent properties?(2 votes)
- An emergent property may be the cycle of energy within a community that is made possible through the populations included in the community. An energy cycle would not exist in a population, but would exist in a community due to the presence of populations.
Hope that makes sense!(8 votes)
- In a Food Web, can there be more than five in a chain to the top?(3 votes)
- Sure, but really not practical since energy diminishes by about 90% as we move to each level. 0.001% is really slim and under most circumstances would not be adequate to support a 6th layer.(5 votes)
- When studying organisms in ecology can it be any size, like some might study bacteria, but studying an elephant would also be studying an organism?(3 votes)
- the list above is correct because it is in smallest to largest.(5 votes)
- Does the Biosphere have to be the entire earth? Or can it be made up of multiple Biospheres depending on how you look at it?(2 votes)
- A biosphere does not necessarily have to be an entire planet.The Amazon forests or the Savannah grasslands,for instance,can be considered as biospheres. Earth has several such biospheres so when we consider all the biospheres on earth, our planet simply becomes the largest scale to look at biospheres.So yes,biospheres can be made up of multiple Biospheres depending on how you look at it.(6 votes)
- What is the difference between ecologists and environmentalists?(2 votes)
- I believe that the difference is so nuanced that they can be used almost interchangeably, but ecologists study the science of how nature evolves and lives and try to conserve that, while environmentalists study the effects of human actions on the environment and how to prevent any negative outcomes.(4 votes)
- Does biotic and abiotic come under ecology? if yes, please can you explain or provide some information or explain if there are any connection between these two topic and ecology.(3 votes)
- Of course that biotic and abiotic come under ecology. Since ecology is a discipline of Biology which explains and investigates interactions among organisms plus their interaction with the environment.
Biotic factors are living things while abiotic factors are non-living things.(1 vote)