Introduction to Ecology - Online Tutor, Practice Problems & Exam Prep

What is Ecology?

This video, we're going to begin our introduction to ecology. And so what is ecology? Well, ecology can be defined as the study of how organisms interact with both the living and the nonliving parts of their environment. And so really ecology is about the relationships that organisms have with their surrounding environment. Now the term biotic refers to the living components of the environment since the root bio means life.

This includes things such as, for example, the trees, the bacteria, and really any other form of life that impacts the organism. Now, of course, the term abiotic on the other hand refers to the nonliving components of the environment that impact the organism, such as, for example, the weather, the mountains, the bodies of water, or the rocks and soil. Now what's really important for you to note is that the ecological interactions that organisms have today are actually influenced by biotic and abiotic factors of both the present, and although you may not realize it, the past as well. And so, yes, factors from 1,000,000 or even 1,000,000,000 years ago can still influence the ecological interactions that organisms have today. And so let's take a look at this image down below to see an example of polar bears and their interactions.

So, notice the left-hand side focuses on biotic factors, the right-hand side focuses on abiotic factors, the top focuses on factors of the present, and the bottom focuses on factors of the past. An example of a biotic factor of the present are modern-day seals, which are actually the main prey of polar bears, and so the distribution of seals impacts the distribution of polar bears since these polar bears are going to be found where they can find their main food source, the seals. Now an example of an abiotic factor of the present is going to be sea ice, since the sea ice is not alive. However, these polar bears spend quite a lot of their time on the sea ice as they're hunting for their main prey, the seals, and so the availability of sea ice will certainly have an impact on the interactions these polar bears have. Now an example of a biotic factor of the past are going to be woolly mammoths, which are organisms that are now extinct.

However, the interactions that polar bears had with woolly mammoths millions of years ago would have shaped the evolution of these polar bears and therefore has an impact on the interactions that the polar bears have today. Now an example of an abiotic factor of the past is continental drift, which refers to the very slow movement of the continents. And so the evidence shows that the continents were connected as you see here, but over a long period of time they drifted apart and this actually isolated the polar bears in the northern hemisphere, and this isolation certainly has an impact on the interactions that the polar bears have today. And so this here concludes our lesson on what is ecology, and we'll be able to learn a lot more about ecology as we move forward. So I'll see you all in our next video.

Environment vs. Habitat vs. Niche

In this video, we're going to differentiate between the terms environment, habitat, and niche as we apply them to this beaver down below in the image. And so the term environment is a very broad term that refers to the total sum of all external biotic and abiotic factors that are surrounding and influencing an organism in any significant way. And so, really, the environment refers to everything that's surrounding and influencing an organism. And so down below in the image, everything that's surrounding and influencing this beaver, including these mountains in the background, could be considered part of the environment.

Now, the habitat, on the other hand, is a smaller subset of the environment as it only refers to a specific part of the external environment and the physical location where an organism actually lives and reproduces. And so the habitat is going to meet an organism's basic needs for survival and reproduction. So notice that down below, this blue region here is representing the habitat where the beaver lives and reproduces. And the mountains, although they are part of the environment, the beaver doesn't actually live and reproduce there, so it's not part of the habitat.

Now, the term niche is an overlapping and multi-dimensional concept that includes the habitat, but it also refers to the functional or ecological role or job that a species performs in its habitat. And that's going to include how the organism utilizes resources and how the organism interacts with both the biotic and abiotic components of its environment, which means that the term niche also captures the conditions that the organism can tolerate.

So notice that this region down below in green represents the niche of this beaver, and what you'll notice is that this beaver is utilizing resources to build this dam, and the dam is going to slow down the flow of water and create new habitats for other organisms. So that is the ecological role of this beaver. So this here concludes our video, and I'll see you in our next one.

Introduction to Ecology Example 1

So here we have an example problem that asks, which of the following scenarios best corresponds with the term niche? And we've got these three potential answer options down below. Now recall from our last lesson video that the term niche is an overlapping concept that includes the habitat but also includes the ecological or functional role or job that an organism performs within its habitat. And so that's important to keep in mind as we go through these options.

Now option A says that a desert fox living in the Sahara Desert, specifically in the sandy dunes where it faces challenges such as extreme heat and scarcity of water. Now it seems to be describing its environment or its habitat with the extreme heat and scarcity of water, but option A does not give any indication as to what the desert fox's role or job is in its ecosystem, and so for that reason, we can eliminate answer option A.

Moving on, option B says, a fish in a pond ecosystem surrounded by mountains where it coexists with frogs, aquatic plants, and algae. Once again, it's giving a little bit of a description of the environment or the habitat since it's saying that it's surrounded by mountains, and it also gives a little bit of an indication as to what its community is by indicating that it's coexisting with frogs, aquatic plants, and algae. But once again, option B gives no indication as to what the role or job is for these fish in this pond ecosystem. And so for that reason, we can eliminate answer option B.

And, of course, this leaves answer option C as the only option, which is the correct answer. It says that a polar bear in the Arctic marine ecosystem navigating the sea ice and serving as a top predator that primarily hunts seals and regulates their population dynamics. Now the reason that this is going to be the correct answer is that it does indicate the role or job of the polar bears, because it says that these polar bears are serving as a top predator. And so as a top predator, it's going to be hunting these seals and, again, regulating the population of those seals to ensure that the population of seals never gets too high, because again, these polar bears are going to be acting as predators to them. And so, option C is the correct answer to this example problem. That concludes this problem, and I'll see you on our next video.

Which of the following scenarios best corresponds with the term “niche”?

• A. A bird flying in the sky.
• B. A fish swimming in a river.
• C. A bee pollinating flowers.
• D. A plant growing in the soil of a forest.

Which of the following is NOT a biotic factor?

• A. Vegetation density.
• B. Soil pH.
• C. Decomposers (e.g. bacteria, fungi).
• D. Predators.

Levels of Ecological Study

In this video, we're going to talk about the levels of ecological study. So ecology can be studied at 6 varying levels of the biological hierarchy, and for each level, we're going to provide a definition and include a typical question that an ecologist studying at that level might ask. Each of these questions is going to be geared toward the species here, which is the capybara, one of the largest rodents on Earth. Now, the first level of ecological study is organismal ecology, which focuses on the behavior, physiology, and evolutionary adaptations of individual organisms, as its name implies with the term organismal, which is why we're showing you just one capybara organism here. A question appropriate for this level of study is: what is the diet of a capybara in this region?

Now the next level of ecological study is population ecology, and recall from the previous lesson videos that a population refers to multiple individuals of the same species living in the same area at the same time. Population ecology is going to examine the population dynamics of just one single species. By dynamics, it means looking at how the population changes over time, including birth rates, death rates, and population size. Notice in the image, we're showing you multiple individuals of the same species, multiple capybaras. A question appropriate for this level of study is: what happens to the capybara population size over time?

Now the next level of ecological study is community ecology, and recall from previous lesson videos that a community refers to multiple populations of different species living in the same area at the same time. Community ecology is going to study the interactions between multiple species within a defined area or habitat. Notice here, the question is: how do caiman, which are predators, affect the distribution of capybaras, the prey, in a wetland ecosystem? Notice that in this image, we're showing you not only the population of capybaras but the populations of other species as well, including caiman.

Now the next level of ecological study is ecosystem ecology; recall from previous lesson videos that an ecosystem includes not only the living community but also their nonliving abiotic environment. Ecosystem ecology is going to investigate an ecosystem's flow of energy and nutrients and analyze biotic-abiotic interactions from both the present and the past, as we've discussed in the previous lesson videos. A typical question suitable for this level of study is: how does precipitation, a non living component of the environment, impact capybaras in a wetland ecosystem? Notice in this image over here, we're showing you these water areas in this wetland ecosystem, which will be influenced by the precipitation, and we're also showing you the living community as well.

Now the next level of ecological study is landscape or seascape ecology; so, a landscape or a seascape is really just a mosaic of multiple ecosystems that are interacting in some way. Landscape focuses on terrestrial ecosystems and seascape focuses on aquatic ecosystems. This is going to examine spatial arrangements and interactions across, again, multiple nearby ecosystems that are interacting with each other. A typical question suitable for this level of study is: how do forest and mountain ecosystems affect capybaras and nearby wetland ecosystems? Notice in this image here, we're showing you a mountain ecosystem, a forest ecosystem, and we're also showing you this wetland ecosystem here. When we look at how these nearby ecosystems impact each other, that's looking at landscape ecology.

Now last but not least, the final level of ecological study is global ecology, which, as its name implies, is going to explore interactions between all of Earth's ecosystems and their impacts on a global scale, looking at the biosphere. A typical question appropriate for this level is: how does global climate change affect worldwide capybara distribution? It's at a very large scale, which is why we're showing you the entire Earth here. That concludes this video, and I'll see you all in our next one.

Introduction to Ecology Example 2

So here we have an example problem that asks, which of the following questions is one that would be asked and investigated by a community ecologist? And we've got these 4 potential answer options down below. Now, of course, recall from our last lesson video that a community ecologist studies the interactions between different species in a defined area or habitat. So that's important to keep in mind as we go through each of these answer options. Now option a says, how does an individual species adapt to changes in its environment?

And option a gives no clear indication that it's looking at the interactions between different species. So for that reason, we can eliminate answer option a. And option a is more of a question that we would expect an organismal ecologist to ask since it's looking at 1 individual species as a whole, not any particular population or community or anything like that, just the individual species as a whole. Now option b says, what are the physical and chemical properties of soil in a particular ecosystem? Now, of course, soil is a nonliving abiotic component of the environment.

And for that reason, we might expect an ecosystem ecologist to ask this particular question. But again, it's not looking at the interactions between different species, so it's not going to be the correct answer for this problem. Now moving on, option c says, how do interactions between different species influence the structure and dynamics of a forest ecosystem? And this is definitely going to be the correct answer to the problem because it's looking at the interactions between different species, and that is what the community ecologist focuses on. So we can indicate that answer option c is the correct answer to this example problem.

But just to be sure, let's check option d which says, what are the genetic variations within a population of birds in a specific region? And again, this is not going to be the correct answer because it's not looking at the interactions between different species. Instead, it's looking at a single population and analyzing the genetic variation. So we might expect a population ecologist to ask this question. And so this here concludes this example; option c is correct, and I'll see you in our next video.

Which of the following is generally considered true of an ecosystem?

• A. Ecosystems consist only of plants, animals & fungi in an environment.
• B. Energy in an ecosystem is transferred from predators down the food chain to producers.
• C. Ecosystems take up relatively small areas, always less than 1 square kilometer.
• D. Ecosystems consist of biotic (e.g. plants, animals) & abiotic (e.g. water availability, soil composition) factors