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What Is Ecology? - Definition & Explanation

What Is Ecology? - Definition & Explanation
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  • 0:01 What Is Ecology?
  • 0:59 Organismal Ecology
  • 2:22 Population Ecology
  • 3:38 Community Ecology
  • 4:39 Ecosystem Ecology
  • 6:00 Lesson Summary
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Lesson Transcript
Instructor: Marta Toran

Marta has taught high school and middle school Science and has a Master's degree in Science Education.

From the largest animals to bacteria invisible to the human eye, the survival of any organism depends on its interaction with the environment. In this lesson you will learn the basics about ecology, the scientific study of these interactions.

What Is Ecology?

The prefix 'eco' has become synonymous with environmentally-friendly living. This green fad, however, has more to do with conservation biology than with ecology, where the prefix is borrowed from.

All organisms, no matter their size, their species, or where they live, need to interact with other organisms in their 'neighborhood' and with their environment in order to survive. Ecology is the scientific study of the interactions between organisms and their environment. The term comes from the Greek 'study of house', or the study of the place we live in.

The scope of ecology is huge, and it encompasses all organisms living on Earth and their physical and chemical surroundings. For this reason, the field is usually divided into different levels of study including: organismal ecology, population ecology, community ecology and ecosystem ecology.

Organismal Ecology

To begin exploring these levels of ecology, picture an American alligator hanging out in the swamp in the Florida Everglades.

Organismal ecology looks at how individuals interact with their environment, which is made up of biotic (living) and abiotic (non-living) components. Consider the biotic and abiotic factors that affect alligators.

At the organismal level, ecology looks at how organisms are adapted to these living and non-living components of their surroundings. For example, because an alligator is cold-blooded, it needs to maximize daylight hours absorbing heat from the sun, so it hangs out on the swamp banks soaking up the rays. This is a behavioral adaptation.

Now, when hunting - especially during cooler or cloudy days - the alligator will move very slowly and is able to hold its breath underwater for almost an hour waiting for its prey. This is a physiological adaptation.

Alligators have developed eyes and a nose on the top of their heads so they can hide just below the surface while still being able to look out for prey and predators. This is a morphological adaptation.

So, with organismal ecology, individual species are linked to various adaptations - behavioral, physiological, or morphological. The adaptations of the alligator allow it to survive in its environment.

Population Ecology

A population is a group of individuals belonging to the same species and living in the same geographic area at a given time. They use the same natural resources and are affected by similar environmental factors. Population ecology examines the factors affecting population density and distribution. Population density is the number of individuals in a given area or volume. Population distribution is how spread out the individuals are in that area. Basically it is how populations change over time. For example, what would happen to the gator population in the swamp if the catfish population decreased due to disease, or if a new competing predator was introduced?

By looking at birth and death rates of specific populations, ecologists can determine the carrying capacity (maximum number of individuals) a habitat can sustain. This helps to determine whether a species will thrive in a particular area, if it is endangered, or if its numbers need to be controlled in order for other species to thrive and resources to be replenished. The human carrying capacity of the Earth is estimated at around 12 billion. In 2011, the population of the Earth was believed to have reached 7 billion and it continues to grow exponentially!

Community Ecology

A biological community is made up of two or more populations of different species inhabiting a particular geographic area. Community ecology looks at the interactions between the populations - for example, competition and predation. One way to represent these relationships is through a food web, which shows predators and prey in a biological community. Let's consider the alligator and the swamp food web as an example.

In this swamp community, the alligator is the top predator. It competes with the heron and the snapping turtle for food because they all share snacks (catfish and invertebrates). However, the alligator also preys on the heron and turtle. The duck, catfish, invertebrates and snake are all primary consumers. This is because they are herbivores and they eat the plants, which are producers in the food chains. The nematodes at the bottom of the food web serve as detritivores. Detritivores clean up (eat) dead matter at the bottom of the swamp.

Ecosystem Ecology

An ecosystem is made up of all the communities living in the same area plus the abiotic factors that affect them. Abiotic factors may include salinity and climate. Major ecosystems which are defined by similar geography, climate, and wildlife, are called biomes. Examples of biomes include deserts, forests, savannas, tropical seas and wetlands like this swamp.

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