Biogeography - Online Tutor, Practice Problems & Exam Prep

Biogeography studies the geographical distribution of organisms, influenced by dispersal, which is the movement of individuals or gametes from their birthplace. Species unable to disperse can become endemic, like polar bears in the Arctic. Ecosystems affect species distribution through biotic factors (e.g., predators, vegetation) and abiotic factors (e.g., temperature, water). Net primary productivity (NPP) indicates ecosystem health, with high NPP supporting diverse life, as seen in the Amazon rainforest compared to the Sahara Desert.

Biogeography

This video, we're going to talk about biogeography. Now ecology is actually impacted by where living species can be found on our planet, which is what makes ecology so closely linked to biogeography. Now biogeography can be defined as the study of how and why organisms are distributed geographically through space and time. Now dispersal is a major factor that impacts the biogeography of a species. So dispersal refers to the movement of individuals or their gametes away from their birthplace to other new locations where they could establish a new population.

Now, again, if the individuals are not capable of moving like plants, for example, then perhaps their gametes such as pollen are capable of being moved by means of the wind or pollinators. Now if a species is not capable of dispersal, that could lead to an endemic species and that is going to be a species that's naturally found in only one specific area on Earth and nowhere else. For example, polar bears are an endemic species to the North Pole and they're only found in Arctic regions despite the South Pole having very similar conditions to the North Pole, and this is because the polar bears are not able to disperse themselves to the South Pole because there's no land mass that directly connects it. Now, on the other hand, these birds that you can see here are called Arctic Terns and they also originated in the North Pole like the polar bears. However, because they are capable of flying, they are actually able to migrate to the South Pole, and so populations of these Arctic Terns can be found all throughout the globe, as they migrate seasonally from the North Pole to the South Pole.

So this here concludes our lesson on biogeography, and we'll be able to continue to learn more as we move forward. So I'll see you all in our next video.

Biogeography Example 1

So here we have an example problem that asks, which of the following factors would not impact a species' ability to expand its range during dispersal? And we've got these four potential answer options down below. Now, of course, recall from our last lesson video that dispersal refers to the movement of individuals or their gametes from their birthplace to other new locations where they could potentially establish a new population and expand the range of the species. Taking a look at answer option A here, it says competition for resources with other species. Now, competition is going to make it more challenging to establish yourself in a new area.

Competition certainly is a factor that would impact the dispersal of a species. But again, we're looking for the answer that would not impact a species' dispersal. So for that reason, we can eliminate answer option A. Now moving on, option B says, the availability of suitable conditions for survival. And, again, the conditions in the environment are going to have an impact on the dispersal of a species.

If the conditions of the environment are not suitable, then the species will not be able to disperse into that area. And so once again, we're looking for the factor that is not going to have an impact on species dispersal, so we can eliminate answer option B because this would have an impact on species dispersal. So now we're between either option C or option D. Notice answer option C says, genetic diversity within a population of that species, and option D says, geographic barriers such as mountains or oceans. For sure, geographic barriers such as mountains or oceans can certainly prevent the dispersal of some species.

Because option D is a factor that would or could impact species dispersal, we can eliminate answer option D, because again, we're looking for the one that would not have an impact on species dispersal. This leaves answer option C, which is going to be the correct answer here, which says, genetic diversity within a population of that species. Genetic diversity is going to exist within every population, and so genetic diversity within a population is not necessarily going to prevent the dispersal of that species, because even with species that are capable of dispersal, there will be some genetic diversity within their population. Option C is going to be the correct answer to this example problem. That concludes this example, and I'll see you all in our next video.

How Ecosystems Impact Species Distribution

This video, we're going to very briefly talk about how ecosystems can impact species distribution by showing you just a few examples of some biotic factors and a few examples of some abiotic factors that can impact the distribution of a species. Recall that biotic factors are considered alive. The presence, absence, and/or amounts of things such as predators, herbivores, vegetation, competing organisms, pollinators, parasites, and pathogens are all just a few examples of living factors that can impact the distribution of a species. You can imagine a scenario where you either add, remove, or change the amounts of any of these things that could potentially impact the distribution of a species. Now, with abiotic factors, we're showing you temperature, water availability, sunlight, oxygen availability, salinity, and the composition of rocks and soil.

Again, removing, adding, or changing the values of any of these things could potentially impact the distribution of any particular species. This is just important to keep in mind as we move forward. So, I'll see you all in our next video.

Biogeography Example 2

So here we have an example problem that wants us to analyze the flowchart and fill in the blanks. So notice down below, we've got this flowchart that's starting on the left-hand side and making its way towards the right-hand side. And it starts with a question asking, what limits the distribution of a species? Now, it turns out that every species on Earth is limited in terms of its distribution because there's no single species on Earth that's capable of surviving and reproducing in every single environment that Earth has to offer. And so when we want to determine what limits the distribution of a species, one of the first questions we might ask ourselves is, is the species able to disperse?

Or in other words, is the species able to move individuals or their gametes from their birthplace into new locations? Now if the answer to this question is yes, the species is capable of dispersing into these new locations, then there must be some factor that limits the distribution into those new locations. And so whether those factors be biotic or abiotic, we can move forward in this flowchart. Now if the answer to this question is no, the species is not able to disperse into this new area. Then in that case, that new area may be inaccessible to that species.

And in this case, dispersal is a limitation to that species. But even if dispersal is a limitation, there can still be other factors that also limit the distribution of that species. So we can still move forward in this flowchart as well. So in either case, we can ask ourselves, do biotic factors limit the distribution of the species? Now if the answer to this question is yes, then all we needed to do is determine which biotic factors limit the distribution.

And so it could be things such as predators, parasites, competition, disease, the amount or type of vegetation, and so on. Now if the answer to the question is no, there are no biotic factors limiting the distribution, then in that case, there must be some abiotic factors limiting the distribution of the species. And even if there are biotic factors limiting the distribution, there can still also be abiotic factors limiting the distribution, so we can still move forward in this flowchart. And so when it comes to the abiotic factors, they could be categorized either as chemical abiotic factors or physical abiotic factors. Now the chemical abiotic factors are going to have to do with chemicals themselves, such as, for example, the amount of water that's present, the amount of oxygen gas that's available, the salinity of the aqueous solution, or the pH of the environment, or even the soil nutrients that are available, and things of that nature.

Now if it is a physical abiotic environment, then it has less to do with the chemicals themselves and more to do with the physical nature of the environment, such as, for example, the temperature, the amount of light, the altitude of that environment, or the climate of the environment, for example. And so this here concludes this example problem, and hopefully, this is a helpful reminder that there can be many factors, biotic or abiotic, that impact the distribution of any particular species. So, I'll see you in our next video.

Which of the following statements about dispersal is correct?

• A. Dispersal can establish new populations and expand the range of the species.
• B. Dispersal only occurs for organisms that can fly, such as birds.
• C. Humans cannot be the cause of dispersal of an animal species.
• D. Animals never play a significant role in plant dispersal.

NPP is a Key Factor in Species Distribution

This video, we're going to talk about NPP. A key factor in species distribution and an indicator of ecosystem health is net primary productivity. Net primary productivity is abbreviated as NPP, and it's often referred to as just the productivity. This is just an estimate of all the organic matter that's available as food in a specific region. The greater the NPP value is, the more food there is in that region.

What this means is that the greater the NPP value, the greater the ecosystem's ability to support more life, essentially allowing for more biomass. Notice below, we've got the satellite image of the entire globe, and we're highlighting two specific regions that have very different NPP values. The first region that we're highlighting is in the northern part of South America, the Amazon rainforest, which has a very high NPP value. This means that it has a lot of organic matter available as food and it's capable of supporting a lot of life. The other region that we're highlighting is in the northern part of Africa, the Sahara Desert, which has a very low NPP value, meaning that it has very little organic matter available as food, therefore it does not support as much life.

So this here concludes our video, and I'll see you all in our next one.

Which of the following is the best indicator of net primary productivity (NPP)?

• A. Weather (temperature & precipitation).
• B. Wind speed & direction.
• C. Biodiversity.
• D. Biomass.