Exploring the Origins of Biodiversity

This presentation covers IBESS Topic 3.2, Origins of Biodiversity, under the main Topic 3, Biodiversity and Conservation. Recall from Topic 3.1 that biodiversity is the amount of biological or living diversity per unit area. It includes the concepts of species diversity, habitat diversity, and genetic diversity. The significant ideas for Topic 3.2 are 1. Evolution is the gradual change in the genetic character of populations over many generations achieved largely through the mechanism of natural selection. Two, environmental change gives new challenges to species, which drives the evolution of diversity. And three, there have been major mass extinction events in the geological past. Okay, you need to wrap your head around these important terms. Evolution. Evolution is a gradual change in the gene pool of a population over time, or the cumulative change in the heritable characteristics of a population. Natural selection is the mechanism by which individuals that are better suited to their environment survive and reproduce more successfully. You must understand, natural selection and evolution are not the same. Natural selection is the mechanism of evolution. Adaptation is an inherited characteristic that increases an organism's chance of survival. Charles Darwin proposed the theory of evolution in his book, The Origin of Species. Let's start our discussion with the mechanism of evolution, or natural selection. One aspect of natural selection as outlined by Darwin is that in order for evolution to take place, there must be variation within a population of a particular species. Variation means that each individual within a species is slightly different from other individuals due to its specific set of inherited genes. When you look at this population of frogs you can see how each individual is slightly different from the others. These differences are due to individual different genes. Different genes is what gives variation to a population. And it is this variation that allows the mechanism of natural selection to take place. So what causes this variation in a population? One major source of genetic variation is genetic mutation, the process of DNA mutating resulting in different proteins being produced. In all sexually reproducing populations, meiosis contributes to genetic variability through the process of cell division that results in greatly variant daughter cells from one sex cell. Also random fertilization of gamete cells in other words which of these daughter cells will be fertilized by these thousands of sperm. This further contributes to genetic variation in a sexually reproducing population random fertilization. Another component of natural selection is that their is that many offspring are produced that then must compete for limited resources for example look at the numerous offspring of this frog all of these offspring must compete for limited resources of the environment into which they hatch the production of many offspring as you can imagine sets the stage for this additional component of natural selection competition when there are many individuals sharing the same space there will be a struggle to survive a struggle to obtain the necessary resources to live. One of the competitors will have a slight genetic advantage that will allow him to survive and pass on his genes. Likewise, as in this picture, the impala that is able to eat well and also escape the cheetah will survive and pass on its genes. Also, the cheetah that is able to catch the impala will also be more likely to survive and be able to reproduce and pass on its genes. The bear that can secure the hunting space to feed off of salmon will also be more likely to survive, breed, and reproduce. Thus, a component of natural selection is that there is a struggle for survival among varied individuals, and some individuals are better suited to the environment or more fit to survive and reproduce and pass on their genes. In order for natural selection to occur, the individuals that are more fit for the environment must reproduce and pass on their genes. Take the example of the Arizona pocket mouse. The lighter colored mice living on lighter environments escape predation by birds and live to reproduce and pass on their genes. Thus, in this environment, more light colored mice are observed. However, when the same species of mice live on dark lava, those mice with the dark mutation escape predation and live to reproduce and pass on their genes. In the dark environment, the population of mice is dark. There is a genetic shift in the population towards a high frequency of mice with dark coloration. Evolution is described as a small accumulated change over generations in the kind and frequency of certain genes expressed in a population. Let's recap the mechanism of natural selection. There is variation in the population and the population reproduces easily. Some individuals are more fit than others and they reproduce more than other individuals, passing on their genes. The offspring of fitter individuals may inherit the genes that then provide them with an advantage to survive the environment. This gradual genetic change in a population leads to favorable characteristics accumulating over time and taken together, this leads to evolution and new species arising. over time. Here is a visual of the mechanism of natural selection. The population has variation due to meiosis, right? We have hairy and non-hairy caterpillars. Some characteristics are more favorable, helping an individual to survive. Individuals with less favorable characteristics may not survive or breed. In this example, birds preferred non-hairy caterpillars to eat. The individuals with more favorable characteristics are better adapted or more fit to survive in their environment. In this example, the hairy caterpillars were more adapted to the environment. They escaped predation and survived to breed. Thus, favorable characteristics are passed on to future generations and become more common. To summarize, natural selection as a driving force for speciation. Evolution is the cumulative, gradual change in the genetic characteristics of successive generations of a species or race of an organism, ultimately giving rise to species or races different from the common ancestor. Charles Darwin developed his theory from his studies on 13 species of finches in the Galapagos Island. He looked at beak size, shape, and shape of the finches. and functions. Some of his observations were that there were stout beaks for eating seeds, and short and sharp beaks for eating insects, and woodpecker-like beaks for eating insects from trees, but instead of a large tongue, it uses a cactopus spine held in its beak to remove prey. How did all of these species of birds come to be on these islands? They all share a common ancestral seed-eating ground finch. A simplified explanation for what happened next is that as mutations occurred, certain traits enabled individuals to obtain food in a new niche. They continued to breed with other individuals having the same mutation, and pretty soon they became a distinct species. Again, over generations, a cumulative gradual change occurred in the shape and size of the beak, ultimately giving rise to many different species of finch. distinctly different from each other and from the common ancestor. So what about the significant idea that states that environmental change gives new challenges to species, which drives the evolution of diversity? Let's look at the example of the Colorado potato beetle. The larvae feed heavily on foliage of potato plants, stripping them of all green material when uncontrolled. These beetles... reproduce rapidly, so over a short time, many generations pass. A mutation in the beetle makes some individuals resistant to the pesticide. Of course, these individuals survive insecticide spraying and survive to pass on their genes to the next generation. Pretty soon, all of the beetles are resistant to the insecticide. In the past 50 years, these beetles have developed resistance to 52 chemical compounds. The environmental change of added insecticide gave a new challenge to the species, which drove the evolution of diversity, specifically giving rise to beetles that are resistant to insecticide. Another really famous example of evolution in response to environmental change is the peppered moth in Europe. During the Industrial Revolution, Pollution blackened the barks of trees in the forest. The gene resulting in a black peppered moth began to appear with higher and higher frequencies over time until virtually the entire population was black. Why do you think that was? Well, look at this image. Which peppered moth is more likely to survive predation? Yes, the black one, because it's more difficult to see. Another example. is the development of resistance to antibiotics by bacteria. Exposure to antibiotics causes the mutation giving resistance to the antibiotic to yield survivorship in the bacteria, and allowing this trait to be passed on to the next generation. I already mentioned the Arizona pocket mouse, that in response to a volcanic eruption and having the ground covered in black lava, the population of mice living on the black lava express a much higher higher frequency of the dark color than those populations living in the sand. Notice that in all of these examples that it is the entire population that is evolving, not individuals. Let's look back at the Darwin finches. What happened over many generations? Well, these populations of finches evolved to the point of actually becoming new species. This is called speciation. The formation of new species when the population of a species becomes isolated and then evolved differently from their ancestors. How does this isolation take place? Geographical, behavioral, genetic, or reproductive factors can contribute to isolation. Simply put, if the gene flow between two subpopulations is prevented, new species may evolve. For example, as the Colorado River slowly carved out the Grand Canyon, different populations of squirrels became separated from each other on either side of the river. Thus, they couldn't exchange genes anymore. Therefore, changes through mutation were different on each side of the canyon. Changes that occurred on the north rim were different from those on the south rim, and vice versa. This genetic isolation resulting from a geographic barrier of the river yielded different species of squirrels on either side of the canyon. Even if these species found themselves in the same habitat for whatever reason, they would not interbreed because they are now a new species. Isolation need not only occur via rivers dividing populations of organisms. In a study done in 2008, it was demonstrated that the uplift of the Andes mountain range in South America resulted in the speciation of a specific species of butterfly into many different new species because different populations were separated by the mountain. As genes mutated in these different populations, the frequency of different genes appeared in these different populations giving rise to entirely new species. Again, even if these species found themselves in the same habitat for whatever reason, they would not interbreed because they are now a new species. Darwin's finches are also an example of genetic isolation between islands. Consider a population of species migrating either from the mainland to the islands or from one island to a neighboring island, and through natural selection evolves into a new species being exposed to a new environment with new niches. Perhaps another population migrates to a different island. with different niches and also evolves into a new species through natural selection. If all these species of birds migrate back to one of the original islands, the birds again will not interbreed or mix because they are now different species. So islands can provide genetic isolation as well. To recap, the isolated population is an isolated gene pool since it does not breed with other populations. The gene pool can therefore change as it adapts to new conditions by natural selection natural selection might result in changes to appearance or behavior of the populations and there is no longer attraction among the two types and therefore they no longer breed resulting in different species. Natural selection might result in the two populations no longer being able to physically breed due to changes in the reproductive organisms. Again, speciation. Or natural selection might simply result in too many genetic differences for the two populations to produce fertile offspring. Another example, different species of fox. Some living in polar locations, and others living in southern latitudes all share the common ancestral species. However, they were isolated from each other through different populations moving northward and southward. The populations became isolated and being exposed to different environmental conditions through the process of natural selection evolved into different species. These two species, if reunited, would not be able to breed and reproduce fertile offspring as they have evolved into different species over many generations. There are many evidences of evolution. One of them is fossil records. Different strata of rock contain fossils that show evolution. For example, the fossil record shows the evolution of fish to amphibian. In addition to the fossil records, there are other pieces of evidence of evolution, including DNA studies, which show how closely specimens are related and that they have a common ancestor. Also, comparative anatomy provides evidence of evolution, such as looking at homologous structures, such as the skeletal structure of an arm and hand found in different species of human, cat, whale, and bat. Or, in looking at the... embryonic development of different species that is also similar. So to recap, speciation is the formation of a new species when populations of a species become isolated and evolve differently. So how did Earth develop so many different species, so much biodiversity, all over the surface? Well, one contributor is the movement of tectonic plates. The surface of Earth is divided into crustal tectonic plates, which have moved throughout geological time. This has led to the creation of both bridges and physical barriers with evolutionary consequences. Furthermore, the distribution of continents has also caused climatic variations and variation in food supply, both contributing to evolution. Over 200 million years ago, a relatively short time geologically, the continents were together, known as Pangea. As a result of this single land mass, we can find certain dinosaur types of today's separated continents. Dinosaurs were the dominant land animals, so even though there was an ancestral mammal species at the time, they had not radiated out like the dinosaurs. The continents then began to drift apart, as visualized in this image, due to the process of plate tectonics. You can see that the separation of the continents began about... 150 million years ago. Populations of organisms were separated or isolated. Evolution occurred in isolated locations. New species formed and biodiversity increased. Remember, these plates are moving continuously. Here is a quick review of plate tectonics. Earth's crust is broken into large pieces called plates. Plates move over time, creating many landforms and geological events, such as earthquakes and volcanoes. These geologic events, such as volcanoes and earthquakes, can bring about a loss of habitat and potential loss of species, thus temporarily lowering biodiversity. The movement of the major and minor plates in relation to one another is called plate tectonics. Plate tectonics can produce barriers such as mountain ranges, oceans, and rift valleys that can lead to isolation of gene pools and then speciation. Perhaps you remember the different types of plate movements? Convergent plates are pushed together. Divergent, where plates are moving apart. And transform are where plates are sliding past each other. Can you think what happens at each of these type of boundaries regarding land, habitat, and biodiversity? Either the activity can be constructive, building new land, or... destructive destroying land and habitat at transform boundaries when plates slide past each other with friction earthquake activity occurs there is no new land or habitat formation in fact there might be destruction of land or habitat at divergent boundaries when plates separate a rift is created Rifts on land result in lake formation, which results in the formation of a new habitat, the lake itself, and a physical barrier, leading to isolation and possible development of new species on either side of the lake. When two continental plates collide, creating a convergent boundary, the result can be the formation of folded mountains. This could lead to both isolation due to the separation of populations on either side of the mountain range and the creation of new habitats. At this type of boundary, there are both constructive and destructive activities occurring. When two oceanic plates collide, the more dense plate subducts and a deep sea trench and oceanic islands can be formed. The Aleutian Islands are a classic example of such activity. With new land formation, new space for additional habitats is created leading to more biodiversity. Through plate tectonics, land bridges can also form previously unconnected plates allowing species to spread. This has of course evolutionary consequences as species migrate and are exposed to new environments different traits will be selected for causing speciation. The movement of plates through different climatic zones allows new habitats and food variations to present themselves and allows for different adaptations. Again creating evolutionary consequences and contributing to speciation. Evidence for plate tectonics comes from just looking at the map and visualizing how the continents at one time all fit together. Additionally, geologic rocks and fossil records support plate tectonics. The same types of geological rocks and fossils are found in certain areas, like here and here, or here and here, because those animals existed when the continents were together. It suggests that organisms in these areas now exist. now separated, shared a common ancestor. Also, locations that are no longer near the equator show evidence of tropical plants and their fossil record, indicating continental drift. As I mentioned before, mammal species radiated much later, like 60 million years ago, after the continents were already separated. So we find different mammals on the different continents. The final I.B. Silimus statement. for topic 3.2 is that mass extinctions of the past have been caused by a combination of factors such as tectonic movements, super volcanic eruption, climatic changes including drought and ice ages, and meteor impact, all of which resulted in new directions and evolution and therefore increased biodiversity. We've already talked about the role of tectonic movements and volcanic eruptions affecting the direction of evolution. Let's discuss these others now. Pictured here is the Al-Waba crater in Saudi Arabia. It is thought that the five great extinctions resulted from meteor impacts on Earth. The impacts certainly reduced biodiversity for the short term. However, with the change in environment, speciation resumed and biodiversity was restored. Climatic change, including ice ages, has influenced evolution and increased biodiversity. You can see in this graph temperature fluctuations over long periods of time, millions of years. Environmental change, including the advance and retreat of glaciers, causes pressures on species to adapt, resulting in speciation. Thus, the formation of new species occurs with climatic change. Drought, another climatic change, also puts pressure on species to adapt. Again, this results in speciation and subsequent occurrence of evolution. Changes in sea levels can also lead to isolation. Bridges might be removed, causing isolation of species. For example, look at the difference in sea levels over a 21,000-year period in Beringia, the land bridge between North America and Siberia. You can see the passageway becomes covered with water, causing isolation of populations that are trapped on either side of the water, again, leading to speciation. Extinction is the process by which a species, genus, or family becomes extinct. no longer existing and living in the world. 99% of all species that have been on earth no longer exist. Background extinction rate is the natural extinction rate of all species and is estimated at about one species per million species per year. Species are becoming extinct at a rate far greater than the background rate. Why? Mass extinctions have occurred over geological time, and there have been about five major ones. You can kind of see them pictured here. These mass extinctions could have been due to some of the factors we've talked about. Rapid climate change, natural disasters like volcanic eruptions or meteorite impacts. These type of events could have resulted in many species dying at once. This slide shows you the estimates for the loss of species during the five major extinctions to date. The percent of families, remember Kingdom Phylum Class Order family, where each family contains up to 1,000 species, is indicated in red. So the percent of families lost is indicated in red. After each of the extinctions, you can see a burst of adaptive radiation of the surviving species, to fill the ecological niches left open. Keep in mind, however, that this does not happen quickly. It takes millions of years. Getting back to my question, why are species becoming extinct at a rate far greater than the background rate? Well, as I've said, there have been at least five mass extinctions in the history of Earth so far, and it has been well argued that we are currently in the midst of a sixth mass extinction event, the Holocene extinction, or alternatively, the Anthropocene extinction. But past extinction events were geological and extraterrestrial. This sixth extinction, however, is human-caused. And this is why species are coming extinct at a rate far greater than the background rate. This extinction event is happening over a much shorter time period. The last 2 to 300 year loss is comparable to 2 to 3 million years. Okay, let's recap this entire movie. Evolution is a gradual change in the genetic character of populations over many generations, achieved largely through the mechanism of natural selection. Make sure you can explain the mechanism of natural selection, and you can distinguish between natural selection and evolution. They are not the same thing. Environmental change gives new challenges to species, which drives speciation. Make sure you understand that term, and thus the evolution of diversity. Isolation of populations can be caused by environmental changes forming barriers such as mountain building, rivers and changes in rivers, sea level change, climatic change, or plate movements. There have been five major mass extinction events in the geological past and we are currently entering the sixth. This ends the movie for IBESS topic 3.2. The slides are adapted from William Green's presentation on his site, The Amazing World of Science with Mr. Green, found at that URL. The Amazing World of Science is licensed under a Creative Commons Attribution International License. Any additional material that I incorporated, I've cited at the bottom of the image or slide where the material is located. Additional insight was obtained from Mr. Dave Hoover's movie presentations at Hoover's YouTube channel. Both of these sites provide additional resources for you for studying and learning. Another resource for you is your IBES's textbook, whether in hardback form or online, such as Cognity. Thanks for listening.

Two, environmental change gives new challenges to species, which drives the evolution of diversity. And three, there have been major mass extinction events in the geological past. Okay, you need to wrap your head around these important terms. Evolution. Evolution is a gradual change in the gene pool of a population over time, or the cumulative change in the heritable characteristics of a population.

Natural selection is the mechanism by which individuals that are better suited to their environment survive and reproduce more successfully. You must understand, natural selection and evolution are not the same. Natural selection is the mechanism of evolution.

Adaptation is an inherited characteristic that increases an organism's chance of survival. Charles Darwin proposed the theory of evolution in his book, The Origin of Species. Let's start our discussion with the mechanism of evolution, or natural selection.

One aspect of natural selection as outlined by Darwin is that in order for evolution to take place, there must be variation within a population of a particular species. Variation means that each individual within a species is slightly different from other individuals due to its specific set of inherited genes. When you look at this population of frogs you can see how each individual is slightly different from the others.

These differences are due to individual different genes. Different genes is what gives variation to a population. And it is this variation that allows the mechanism of natural selection to take place. So what causes this variation in a population?

One major source of genetic variation is genetic mutation, the process of DNA mutating resulting in different proteins being produced. In all sexually reproducing populations, meiosis contributes to genetic variability through the process of cell division that results in greatly variant daughter cells from one sex cell. Also random fertilization of gamete cells in other words which of these daughter cells will be fertilized by these thousands of sperm. This further contributes to genetic variation in a sexually reproducing population random fertilization. Another component of natural selection is that their is that many offspring are produced that then must compete for limited resources for example look at the numerous offspring of this frog all of these offspring must compete for limited resources of the environment into which they hatch the production of many offspring as you can imagine sets the stage for this additional component of natural selection competition when there are many individuals sharing the same space there will be a struggle to survive a struggle to obtain the necessary resources to live.

One of the competitors will have a slight genetic advantage that will allow him to survive and pass on his genes. Likewise, as in this picture, the impala that is able to eat well and also escape the cheetah will survive and pass on its genes. Also, the cheetah that is able to catch the impala will also be more likely to survive and be able to reproduce and pass on its genes. The bear that can secure the hunting space to feed off of salmon will also be more likely to survive, breed, and reproduce.

Thus, a component of natural selection is that there is a struggle for survival among varied individuals, and some individuals are better suited to the environment or more fit to survive and reproduce and pass on their genes. In order for natural selection to occur, the individuals that are more fit for the environment must reproduce and pass on their genes. Take the example of the Arizona pocket mouse.

The lighter colored mice living on lighter environments escape predation by birds and live to reproduce and pass on their genes. Thus, in this environment, more light colored mice are observed. However, when the same species of mice live on dark lava, those mice with the dark mutation escape predation and live to reproduce and pass on their genes.

In the dark environment, the population of mice is dark. There is a genetic shift in the population towards a high frequency of mice with dark coloration. Evolution is described as a small accumulated change over generations in the kind and frequency of certain genes expressed in a population. Let's recap the mechanism of natural selection.

There is variation in the population and the population reproduces easily. Some individuals are more fit than others and they reproduce more than other individuals, passing on their genes. The offspring of fitter individuals may inherit the genes that then provide them with an advantage to survive the environment. This gradual genetic change in a population leads to favorable characteristics accumulating over time and taken together, this leads to evolution and new species arising. over time.

Here is a visual of the mechanism of natural selection. The population has variation due to meiosis, right? We have hairy and non-hairy caterpillars.

Some characteristics are more favorable, helping an individual to survive. Individuals with less favorable characteristics may not survive or breed. In this example, birds preferred non-hairy caterpillars to eat. The individuals with more favorable characteristics are better adapted or more fit to survive in their environment. In this example, the hairy caterpillars were more adapted to the environment.

They escaped predation and survived to breed. Thus, favorable characteristics are passed on to future generations and become more common. To summarize, natural selection as a driving force for speciation.

Evolution is the cumulative, gradual change in the genetic characteristics of successive generations of a species or race of an organism, ultimately giving rise to species or races different from the common ancestor. Charles Darwin developed his theory from his studies on 13 species of finches in the Galapagos Island. He looked at beak size, shape, and shape of the finches.

and functions. Some of his observations were that there were stout beaks for eating seeds, and short and sharp beaks for eating insects, and woodpecker-like beaks for eating insects from trees, but instead of a large tongue, it uses a cactopus spine held in its beak to remove prey. How did all of these species of birds come to be on these islands? They all share a common ancestral seed-eating ground finch.

A simplified explanation for what happened next is that as mutations occurred, certain traits enabled individuals to obtain food in a new niche. They continued to breed with other individuals having the same mutation, and pretty soon they became a distinct species. Again, over generations, a cumulative gradual change occurred in the shape and size of the beak, ultimately giving rise to many different species of finch. distinctly different from each other and from the common ancestor.

So what about the significant idea that states that environmental change gives new challenges to species, which drives the evolution of diversity? Let's look at the example of the Colorado potato beetle. The larvae feed heavily on foliage of potato plants, stripping them of all green material when uncontrolled. These beetles...

reproduce rapidly, so over a short time, many generations pass. A mutation in the beetle makes some individuals resistant to the pesticide. Of course, these individuals survive insecticide spraying and survive to pass on their genes to the next generation. Pretty soon, all of the beetles are resistant to the insecticide. In the past 50 years, these beetles have developed resistance to 52 chemical compounds.

The environmental change of added insecticide gave a new challenge to the species, which drove the evolution of diversity, specifically giving rise to beetles that are resistant to insecticide. Another really famous example of evolution in response to environmental change is the peppered moth in Europe. During the Industrial Revolution, Pollution blackened the barks of trees in the forest.

The gene resulting in a black peppered moth began to appear with higher and higher frequencies over time until virtually the entire population was black. Why do you think that was? Well, look at this image. Which peppered moth is more likely to survive predation? Yes, the black one, because it's more difficult to see.

Another example. is the development of resistance to antibiotics by bacteria. Exposure to antibiotics causes the mutation giving resistance to the antibiotic to yield survivorship in the bacteria, and allowing this trait to be passed on to the next generation. I already mentioned the Arizona pocket mouse, that in response to a volcanic eruption and having the ground covered in black lava, the population of mice living on the black lava express a much higher higher frequency of the dark color than those populations living in the sand. Notice that in all of these examples that it is the entire population that is evolving, not individuals.

Let's look back at the Darwin finches. What happened over many generations? Well, these populations of finches evolved to the point of actually becoming new species. This is called speciation. The formation of new species when the population of a species becomes isolated and then evolved differently from their ancestors.

How does this isolation take place? Geographical, behavioral, genetic, or reproductive factors can contribute to isolation. Simply put, if the gene flow between two subpopulations is prevented, new species may evolve. For example, as the Colorado River slowly carved out the Grand Canyon, different populations of squirrels became separated from each other on either side of the river. Thus, they couldn't exchange genes anymore.

Therefore, changes through mutation were different on each side of the canyon. Changes that occurred on the north rim were different from those on the south rim, and vice versa. This genetic isolation resulting from a geographic barrier of the river yielded different species of squirrels on either side of the canyon.

Even if these species found themselves in the same habitat for whatever reason, they would not interbreed because they are now a new species. Isolation need not only occur via rivers dividing populations of organisms. In a study done in 2008, it was demonstrated that the uplift of the Andes mountain range in South America resulted in the speciation of a specific species of butterfly into many different new species because different populations were separated by the mountain. As genes mutated in these different populations, the frequency of different genes appeared in these different populations giving rise to entirely new species.

Again, even if these species found themselves in the same habitat for whatever reason, they would not interbreed because they are now a new species. Darwin's finches are also an example of genetic isolation between islands. Consider a population of species migrating either from the mainland to the islands or from one island to a neighboring island, and through natural selection evolves into a new species being exposed to a new environment with new niches.

Perhaps another population migrates to a different island. with different niches and also evolves into a new species through natural selection. If all these species of birds migrate back to one of the original islands, the birds again will not interbreed or mix because they are now different species.

So islands can provide genetic isolation as well. To recap, the isolated population is an isolated gene pool since it does not breed with other populations. The gene pool can therefore change as it adapts to new conditions by natural selection natural selection might result in changes to appearance or behavior of the populations and there is no longer attraction among the two types and therefore they no longer breed resulting in different species.

Natural selection might result in the two populations no longer being able to physically breed due to changes in the reproductive organisms. Again, speciation. Or natural selection might simply result in too many genetic differences for the two populations to produce fertile offspring. Another example, different species of fox. Some living in polar locations, and others living in southern latitudes all share the common ancestral species.

However, they were isolated from each other through different populations moving northward and southward. The populations became isolated and being exposed to different environmental conditions through the process of natural selection evolved into different species. These two species, if reunited, would not be able to breed and reproduce fertile offspring as they have evolved into different species over many generations. There are many evidences of evolution. One of them is fossil records.

Different strata of rock contain fossils that show evolution. For example, the fossil record shows the evolution of fish to amphibian. In addition to the fossil records, there are other pieces of evidence of evolution, including DNA studies, which show how closely specimens are related and that they have a common ancestor.

Also, comparative anatomy provides evidence of evolution, such as looking at homologous structures, such as the skeletal structure of an arm and hand found in different species of human, cat, whale, and bat. Or, in looking at the... embryonic development of different species that is also similar.

So to recap, speciation is the formation of a new species when populations of a species become isolated and evolve differently. So how did Earth develop so many different species, so much biodiversity, all over the surface? Well, one contributor is the movement of tectonic plates.

The surface of Earth is divided into crustal tectonic plates, which have moved throughout geological time. This has led to the creation of both bridges and physical barriers with evolutionary consequences. Furthermore, the distribution of continents has also caused climatic variations and variation in food supply, both contributing to evolution.

Over 200 million years ago, a relatively short time geologically, the continents were together, known as Pangea. As a result of this single land mass, we can find certain dinosaur types of today's separated continents. Dinosaurs were the dominant land animals, so even though there was an ancestral mammal species at the time, they had not radiated out like the dinosaurs.

The continents then began to drift apart, as visualized in this image, due to the process of plate tectonics. You can see that the separation of the continents began about... 150 million years ago.

Populations of organisms were separated or isolated. Evolution occurred in isolated locations. New species formed and biodiversity increased.

Remember, these plates are moving continuously. Here is a quick review of plate tectonics. Earth's crust is broken into large pieces called plates.

Plates move over time, creating many landforms and geological events, such as earthquakes and volcanoes. These geologic events, such as volcanoes and earthquakes, can bring about a loss of habitat and potential loss of species, thus temporarily lowering biodiversity. The movement of the major and minor plates in relation to one another is called plate tectonics.

Plate tectonics can produce barriers such as mountain ranges, oceans, and rift valleys that can lead to isolation of gene pools and then speciation. Perhaps you remember the different types of plate movements? Convergent plates are pushed together. Divergent, where plates are moving apart.

And transform are where plates are sliding past each other. Can you think what happens at each of these type of boundaries regarding land, habitat, and biodiversity? Either the activity can be constructive, building new land, or... destructive destroying land and habitat at transform boundaries when plates slide past each other with friction earthquake activity occurs there is no new land or habitat formation in fact there might be destruction of land or habitat at divergent boundaries when plates separate a rift is created Rifts on land result in lake formation, which results in the formation of a new habitat, the lake itself, and a physical barrier, leading to isolation and possible development of new species on either side of the lake. When two continental plates collide, creating a convergent boundary, the result can be the formation of folded mountains.

This could lead to both isolation due to the separation of populations on either side of the mountain range and the creation of new habitats. At this type of boundary, there are both constructive and destructive activities occurring. When two oceanic plates collide, the more dense plate subducts and a deep sea trench and oceanic islands can be formed. The Aleutian Islands are a classic example of such activity. With new land formation, new space for additional habitats is created leading to more biodiversity.

Through plate tectonics, land bridges can also form previously unconnected plates allowing species to spread. This has of course evolutionary consequences as species migrate and are exposed to new environments different traits will be selected for causing speciation. The movement of plates through different climatic zones allows new habitats and food variations to present themselves and allows for different adaptations.

Again creating evolutionary consequences and contributing to speciation. Evidence for plate tectonics comes from just looking at the map and visualizing how the continents at one time all fit together. Additionally, geologic rocks and fossil records support plate tectonics. The same types of geological rocks and fossils are found in certain areas, like here and here, or here and here, because those animals existed when the continents were together. It suggests that organisms in these areas now exist.

now separated, shared a common ancestor. Also, locations that are no longer near the equator show evidence of tropical plants and their fossil record, indicating continental drift. As I mentioned before, mammal species radiated much later, like 60 million years ago, after the continents were already separated.

So we find different mammals on the different continents. The final I.B. Silimus statement.

for topic 3.2 is that mass extinctions of the past have been caused by a combination of factors such as tectonic movements, super volcanic eruption, climatic changes including drought and ice ages, and meteor impact, all of which resulted in new directions and evolution and therefore increased biodiversity. We've already talked about the role of tectonic movements and volcanic eruptions affecting the direction of evolution. Let's discuss these others now. Pictured here is the Al-Waba crater in Saudi Arabia.

It is thought that the five great extinctions resulted from meteor impacts on Earth. The impacts certainly reduced biodiversity for the short term. However, with the change in environment, speciation resumed and biodiversity was restored.

Climatic change, including ice ages, has influenced evolution and increased biodiversity. You can see in this graph temperature fluctuations over long periods of time, millions of years. Environmental change, including the advance and retreat of glaciers, causes pressures on species to adapt, resulting in speciation. Thus, the formation of new species occurs with climatic change. Drought, another climatic change, also puts pressure on species to adapt.

Again, this results in speciation and subsequent occurrence of evolution. Changes in sea levels can also lead to isolation. Bridges might be removed, causing isolation of species.

For example, look at the difference in sea levels over a 21,000-year period in Beringia, the land bridge between North America and Siberia. You can see the passageway becomes covered with water, causing isolation of populations that are trapped on either side of the water, again, leading to speciation. Extinction is the process by which a species, genus, or family becomes extinct. no longer existing and living in the world.

99% of all species that have been on earth no longer exist. Background extinction rate is the natural extinction rate of all species and is estimated at about one species per million species per year. Species are becoming extinct at a rate far greater than the background rate. Why?

Mass extinctions have occurred over geological time, and there have been about five major ones. You can kind of see them pictured here. These mass extinctions could have been due to some of the factors we've talked about.

Rapid climate change, natural disasters like volcanic eruptions or meteorite impacts. These type of events could have resulted in many species dying at once. This slide shows you the estimates for the loss of species during the five major extinctions to date. The percent of families, remember Kingdom Phylum Class Order family, where each family contains up to 1,000 species, is indicated in red.

So the percent of families lost is indicated in red. After each of the extinctions, you can see a burst of adaptive radiation of the surviving species, to fill the ecological niches left open. Keep in mind, however, that this does not happen quickly.

It takes millions of years. Getting back to my question, why are species becoming extinct at a rate far greater than the background rate? Well, as I've said, there have been at least five mass extinctions in the history of Earth so far, and it has been well argued that we are currently in the midst of a sixth mass extinction event, the Holocene extinction, or alternatively, the Anthropocene extinction.

But past extinction events were geological and extraterrestrial. This sixth extinction, however, is human-caused. And this is why species are coming extinct at a rate far greater than the background rate. This extinction event is happening over a much shorter time period. The last 2 to 300 year loss is comparable to 2 to 3 million years.

Okay, let's recap this entire movie. Evolution is a gradual change in the genetic character of populations over many generations, achieved largely through the mechanism of natural selection. Make sure you can explain the mechanism of natural selection, and you can distinguish between natural selection and evolution.

They are not the same thing. Environmental change gives new challenges to species, which drives speciation. Make sure you understand that term, and thus the evolution of diversity. Isolation of populations can be caused by environmental changes forming barriers such as mountain building, rivers and changes in rivers, sea level change, climatic change, or plate movements.

There have been five major mass extinction events in the geological past and we are currently entering the sixth. This ends the movie for IBESS topic 3.2. The slides are adapted from William Green's presentation on his site, The Amazing World of Science with Mr. Green, found at that URL. The Amazing World of Science is licensed under a Creative Commons Attribution International License. Any additional material that I incorporated, I've cited at the bottom of the image or slide where the material is located.

Additional insight was obtained from Mr. Dave Hoover's movie presentations at Hoover's YouTube channel. Both of these sites provide additional resources for you for studying and learning. Another resource for you is your IBES's textbook, whether in hardback form or online, such as Cognity.

Thanks for listening.

Transcript for:Exploring the Origins of Biodiversity

Transcript for:
Exploring the Origins of Biodiversity