Skip to main content
Loading Explore guides…
Evolution, Extinction, Biodiversity · Acedra
Home
Explore
Biology
Evolution, Extinction, Biodiversity
Sign in to save
Chat
If YouTube asks you to sign in, open the video on YouTube.
Watch on YouTube
Reload player
Transcript
101 segments
Copy
Hide video
0:10
hi everyone welcome back I'm Professor Paul day and I'm going to be doing a new topic in environmental Sciences Evolution Extinction and biodiversity these are very sophisticated Topics by the way you can do an entire course just on Evolution an entire course on extinction an entire course on biodiversity but we're going to be nibbling a little bit at uh at this topic because it's so important for understanding the fabric of life that is all around us and that fabric of Life of
0:41
course is important for understanding the consequences for decisions that are being made and it's also important for understanding the past when we're looking especially at the fossil record what might have happened to bring about the conditions that exist today so let's go ahead and jump into this fascinating world of evolution Extinction and biodiversity I know you're really going to enjoy it all right we're going to go ahead and we're going to begin by learning a couple of very important
1:07
terms they're thrown about quite a bit in common textbooks they're thrown about on television they're thrown about on the internet a lot of people use these words but they don't really know what they mean so we want to dig into what we mean in terms of environmental science the first word here is going to be species species is a population and we're going to come to this word population here in a minute you can see it down here or group of populations whose members share characteristics
1:36
um so what do we mean by that well ultimately we mean by characteristics that result in animals that can breed with one another and produce fertile offspring that's a species so just because an animal has four legs walks around and eats grass does not necessarily mean it's the same species as other animals that have four legs and eat grass I'll give you an example of say a wildebeest and a and a horse right they are not members of the same species they cannot breed with one another and
2:06
produce fertile offspring horses can find other horses wildebeest can find other wildebeest in the case of horses you might be thinking to yourself yeah but wait a minute can't a horse breed with a donkey aren't those therefore of the same species well ask yourself what is The Offspring of a horse and a donkey right it's a mule so it's neither a horse nor a donkey it's a hybrid of the two and can a mule reproduce the answer is it cannot so these two species in this case the horse
2:41
and the donkey are separate species that do have enough in common with one another genetically where they're able to produce Offspring but those offspring are not viable in other words they cannot produce their own offspring okay so there's not going to be a wild horde uh herd I'm sorry of mules running around out in the wilderness a population is simply a group of individuals of a species that live in the same area in other words this is a group that has the ability to interact
3:14
with one another to uh to survive together they might even have a common food source and they're certainly reproducing with one another okay I want to give you an example of two animals who have very similar characteristics but do not interbreed with one another and produce a fertile offspring we brought up the case of the horse the mule but here we have this right here right two birds the warbler and the chip chaff if I'm saying that even correctly the chiff chaff is this one over here
3:45
here's the warbler over here they're very similar they're almost identical in appearance but they do not interbreed they do not interbreed at all all right so now that we have defined what a species is and we've defined what populations are let's go ahead and dive right into a very important topic kind of the focus of most of this lecture everything else is derived from it this Evolution evolution is just simply change over time in biological systems biological evolution is simply change in
4:18
populations of organisms over Generations it's just the net change in the populations itself right it might be in an individual here or a trait that we're seeing here and there but overall we're seeing biological evolution which is the overall change genetic changes lead to changes in appearance now remember when we're talking about genetic we're talking about the genes right the DNA that make us up those changes that Evolution lead to changes in appearance functioning right so we
4:49
don't look the same over time we don't function the same way over time or we might not have the same behaviors as a consequence now genetic changes in evolution may be random they can occur due to a mutation for example however some things are favorable in other words it might be really good to have I don't know x-ray vision or something if you're a human being so suddenly you can see through walls and detect threats and maybe be a great hunter um so we as far as I could tell people
5:23
have not evolved this yet but it might be something that's favorable or it might turn out that x-ray vision takes up so much energy that you have a very short lifespan and it makes life very difficult right who knows how that would work out life is full of trade-offs it turns out so that means that it might be directed by natural selection now what is natural selection natural selection is simply the process in which traits that enhance survival and reproduction so both of these things
5:55
are passed on more frequently to Future Generations than those that do not so if you have a better chance to survive in an environment um then over time your offspring are going to pick up on that survivability and they're going to have more offspring right and so it becomes a self-fulfilling process where the reproduction is feeding the survivability which is then feeding the reproduction back and forth okay and there's a great example of this here I have a YouTube uh example that I would
6:29
like to direct you to if you've got the chance I'll put it down in the comment section so you can go ahead or I'm sorry in the description so that you can go ahead and follow up on it it's a great little video showing how natural selection can work in the proliferation of say of diseases and how antibiotics are can over time be overcome through natural selection of pathogens that are trying to make you sick uh genetic makeup of future populations is therefore changed over time through
7:03
natural selection right so here we have a male peacock and a female peacock the female peacock does not have the plumage that we're seeing coming off this male peacock this male peacock of course has acquired this plumage through years and years in fact Generations upon generations of natural selection so what is making the selection well we believe that the female is attracted to that plumage and so that enhances his ability to reproduce doesn't mean that it's easy I'm sure
7:37
maintaining this and feeding that feather those feathers to be able to make that plumage uh is a bit of a challenge it's a little bit of extra energy but that energy is put to good use because it enhances their ability to reproduce because it's being selected for by the female okay and that plays a big role if one of these Sexes inside of the uh you know in the in the peacock species is selecting for large plumage you're going to see large plumage over time but they dislike
8:08
it you'll see less of it
8:20
now I cannot emphasize enough as we're going through this that evolution is one of the best supported and most Illuminating Concepts in all of Science in fact it is the foundation of Modern Biology and of course Modern Biology is the foundation of modern medicine so it's extremely important to understand Evolution and how it works now we must understand it to appreciate what environmental science has to offer us so understanding how species change over time and adapt to their surroundings is
8:52
crucial for comprehending ecology we're going to get into what ecology is here in a little bit and the history of life where do we come from it's an important question right because it's the question of us where did we come from human beings when I show a a graphic like this here we see that there's a given and a human and a chimpanzee and a gorilla an orangutan and people will immediately say are you trying to tell me that I evolved from a chimpanzee or an orangutan no that's not what evolution
9:24
is telling us was telling us is that we might have some type of common ancestor that has many of the same traits right the ability to stand upright with the long appendages that are used for holding and grabbing things we're walking on feet right we can see that many of these features that we're seeing between especially a human in a chimpanzee are very similar but also a little bit different right a little bit different right the way that a chimpanzee walks is
9:54
not the same way that a human being walks the way that they socialize is not the same but there's still some familiarity between the two right so evolutionary processes influence pesticide resistance agriculture medicine Health etc etc etc in fact it is our understanding of evolution that has led to the breakthroughs of many of the things that we enjoy today in our modern Sciences in our food supply and of course the lecture series that I'm presenting right now will cover many of
10:28
those evolutionary processes and those breakthroughs that human beings have accomplished as our consequence of our understanding of it now our understanding of natural selection and how it shapes organisms and diversity wasn't really worked out for a very long time in human history we it's actually a fairly New Concept in terms of science uh it really came about on the shoulders of person by the name of Charles Darwin uh who is pictured right over here off to the right he's a
10:57
very famous person he wrote some very important treatises um On the Origin of Species which is the regard which is considered one of the most important texts in all of biology that book lays out the principles of natural selection including the evidence which is pretty convincing stuff and in 1858 he came out with it uh Alfred Russell Wallace had independently come up with the idea also um and they realized that Darwin and Russell came to get to know each other
11:30
they were familiar they became familiar with each other's works and they decided to go ahead and release this New Concept this natural selection that later fed into the concept of how Evolution operates in 1858 so premises of natural selection were these that organisms struggled to survive and reproduce uh so life is hard right it takes a lot of effort takes some self-defense takes some camouflage um it takes a a large social network in certain situations right but that life
12:05
was difficult and there was a large amount of struggle that organisms produce more offspring than can survive so in other words they're constantly trying to improve the uh in terms of the species the number of offspring that they have right so if you if if your species constantly producing three Offspring but five die for every three you produce you're going to decline pretty quickly so you need to have an upward trajectory on your population now that doesn't mean that your
12:35
population is going to grow infinitely right you can continue to produce but there's going to be effects that that kick in at some point something called the carrying capacity will set in all right so individuals of a species vary in their characteristics due to genes and the environment individuals right so it's not just the species themselves that are carrying all the genes but the individuals within the the uh species are almost like little Laboratories of little things that are
13:05
happening for example the traits that I have have probably never been seen by any other human being before it doesn't mean that there aren't people that don't look similar to me or there aren't people that have many of the similar traits that I have but my genetic makeup is unique to me okay now of course uh Charles Darwin and Alfred Wallace had no idea about the way that genes worked and all of this other stuff they just knew that these traits were there okay that some individuals
13:35
are better suited to their environment and reproduce more effectively and this feeds into what we're talking about with the peacock example previously right now organisms with better adapted traits will produce more offspring over time and so as a consequence if you're able to produce more offspring you can we'll get into this idea of competition but you're able to out-compete other people in an environment or other species within an environment or other individuals with an environment and your
14:03
traits are more likely to be passed on until something else gains some type of advantage over you which case your traits will take a nosedive and theirs will take it will be preferred in that situation now that we've discussed what natural selection is we have to talk about the process where over time these traits wind up manifesting themselves in organisms and the creation of species the main way that this occurs is what through a process we call adaptation this is where as I just defined the
14:42
process where over time characteristics what we call traits right those are those characteristics I use the word traits uh on the last little segment there but it's the term characteristics is a really good uh descriptor for that that lead to better reproductive success and becomes more prevalent in the population that's adaptation so you start to see more and more and more of it as it's adapted into the population there an Adaptive trait is a trait that promotes reproductive success something
15:13
that's actually functioning and working is the actual trait that is working um now we need to say what is it that might be triggering these adaptive traits what might be creating this these changes that are happening um one of the ways that is most commonly cited is mutations mutations are accidental changes in DNA that may be passed on to the next Generation so remember your DNA is a code and a mutation is just a change in that code that's all it is now non-lethal mutations provide the
15:46
genetic variation on which natural selection acts now what if there is a lethal mutation well it means you don't survive right you die from it maybe it causes a heart defect perhaps it causes some type of of cancer or for whatever reason it's lethal it terminates the organism if they happen to have this mutation but a non-lethal mutation could be an opportunity to alter the toolkit that some organism has and it might make things like I don't know five fingers
16:21
versus six figures blue eyes versus say green eyes whatever the change is right that is being changed or tinkered with is the consequence of a mutation that is happening within the genetic code sexual reproduction also leads to variation right everybody's bringing something to the table right we're all individuals with our own kind of biological laboratory and what we're doing is we're combining our biological laboratory with the biological laboratory of another individual with
16:53
the population so if a human male and human female are reproducing they're bringing their own traits to the table and The Offspring are going to have some of one trait and some of another uh some I'm sorry some traits of one parent and some traits of the other right that's what sexual reproduction does this is as opposed to asexual reproduction which is where The Offspring look just like the parents and there's uh all kinds of issues that can arise from that over time but sexual
17:25
reproduction allows for these Laboratories to constantly experiment and to alter things so your Offspring may look like you but they're not identical to you and they will have little changes that have never been seen before uh within the species now this could lead to some really interesting consequences a concept called directional selection this is what drives a feature in One Direction so if you go out into the desert for example the the desert of the southwestern
17:57
United States you'll find very tall cacti the the cacti populations out there are a consequence of directional selection you do not find oak trees for example in the middle of a sand dune uh and the reason why is because of the conditions that are favoring one type what we call a phenotype over another so a phenotype is a body form or a or a type of of or set of adaptations that are being manifested by that organism and so what we could do is we could look
18:30
at these charts here to give you an idea of how directional um how directional changes can happen over time what we call genetic selection we have a y-axis in that x-axis and what we're seeing here is the red is the original distribution of the population here with all the different types and if there is a uniform directional push in One Direction over time this red will morph into what we're seeing here with the blue okay this is what we're seeing it pushed
19:05
into an extreme Direction so for example if an area if you have birds that are say red and another type of bird with that is within the species that is white and the area undergoes some type of climate change all of a sudden the area is covered in snow the red birds become much less preferred in that environment than the white ones because the white ones can hide obviously and the trees or in the snow okay more effectively than the red ones can so what will you see over time
19:38
adrift towards the white colored birds living within that snow environment now if it was a snowy environment and it went the opposite direction then perhaps the red ones would be preferred over time right so you get the concept so this is where you're taking something and pushing it into an extreme Direction now uh what we're seeing here on graph number two is that same population over time is suddenly uh being normalized where we're having a single the kind of
20:08
the central parts of the uh the group the average part of the group being emphasized where the extreme examples are being cut out they're not being preferred okay so we're reinforcing everything towards a single uh what we call phenotype again or we could have a disruptive one where the the single phenotype is not preferred maybe a disease is hit and it's able to wipe out the center part of this but for some reason the extremes are able to survive right and be able to reproduce and carry
20:40
that on into the future populations and so we'll see in this case disruptive speciation one species separating off from the other it's it's really interesting to see all the different possibilities now probably the best way to really understand what is going on when we're talking about this is not to Simply show you the graphs even though it gives you the idea is to actually show you real examples that we believe have happened where we look at related species in
21:09
different environments right so you're taking a species that is in one environment and has been subjected to a completely different environment to see if there's any changes that have occurred over time and this would create different pressures and would in theory cause the creation of different traits this would be more Evolution that would happen right and so one of the best places to look at is Charles Darwin's own work he was actually looking at finches uh in the Galapagos Islands uh as well
21:39
as animals across South America but the the finches are just famous what we're looking at is four of Darwin's finches um the species that he was looking at here and we'll notice that they are all started off as just regular finches they were all identical they are from a common ancestor but they were on an island where there were no competitors or these big open areas uh and so the finches spread out into different areas some went into the trees some went down
22:07
into the grass and they began adapting and hunting for different things some became animals that hunted for nuts and other ones looked for insects other ones became more vegetarian looking for seeds and other ones we're looking for and picking for other little insects and worms and so as a consequence over time they had selective traits and pressures that were put on them and they who underwent something called divergent evolution so divergent evolution is the accumulation of differences between
22:41
closely related populations within a species leading to speciation in other words the formation of new species so here we are seeing these finches notice that they're bills right are all designed for different things they eat differently they run in different populations they live in a different portion of the Galapagos Islands under and fulfilling different roles and we'll get into what those roles are in another lecture but here we're seeing four different species of finches that
23:11
originated as a single species conversely if you take animals from that are unrelated to one another but you put them into similar environments they might even take on very similar body forms to the point where you might make the assumption that they're very closely related when in fact they have very different ancestries a great example of this would be the modern dolphin right here we're seeing the skeleton of a modern dolphin and below here is an extinct species of something called an
23:44
ichthyosaur so when we're looking at these we might say these things are very closely related they're clearly marine animals the difference is is that the modern dolphin is a mammal um it originated on land but it's a mammal has completely different ancestry than this ichthyosaur whose ancestors were also land animals but in this case it was a reptile so here we're seeing something that looks like a fish but it's in fact a reptile here we're seeing something that has features that shows
24:14
that it's meta that it's Marine um we could even say fish like also but again this is a mammal this is a land animal and the relationship between these two there is none there is none but we see that convergent evolution of them going into the same environment and therefore adapting similar traits
24:47
so now that we've covered the basics of what evolution is and how it changes animal forms and life forms over time one of the things that also is very good at doing is generating something called biodiversity so biodiversity we've got a nice little definition up here is also biological diversity right it's a two words put together it's the variety of Life across all levels of biological organization this is the species right not just uh all turtles but down to the specific Turtles
25:20
over time as we're seeing a sea turtle swimming through the ocean right here in a marine environment near a coral reef but it also affects the genes so it might be affecting areas they're not visible to us it could be infecting populations and communities and so as a consequence we're producing new animal forms all the time with all these different traits with different genes those genes are moving into different portions of the ecosystem globally scientists have described about 1.8
25:51
million species but estimates of the total number of species that exist range from 3 million to 100 million and biodiversity exists nearly everywhere and one of the most biodiverse locations where you can see it plain as day is a coral reef this is unlike a rainforest which is one of the most bio which is the most biodiverse area uh coral reefs you can look through the water and you could see every little thing that's going on out here as long as you have a
26:17
good Vision through the water as long as it's not too murky whereas the urinate Forest a lot of this stuff could be hidden you can clearly see the complex interactions between all of these animals all of which depend upon each other to some extent and it's biodiversity created through Evolution that makes this scene that you're looking at in this picture happen now the question fundamentally is going to be if evolution is constantly taking old forms and making new forms there's
26:48
got to be a point where a new form a new species comes into existence so we call that speciation speciation produces new types of organisms it's the process of generating new species from a single species right you're going to create one species and that species have has the opportunity to Branch out and to have descendants that could be of different types in different locations I want to give a great example of speciation allopatric speciation so species formation due to physical
27:18
separation of populations where you're physically moving animals or separating them due to some kind of barrier this is considered the main mode it's not the only mode but it's the main mode for speciation why would you need to create another body form well a great place to look at this is going to be right here in central Africa we're going to come back to this map here in a minute but the populations can be separated by glaciers right so a glacier is a moving
27:44
object has the ability to come into a valley and separate herds of animals away from each other perhaps run over certain areas freeze Rivers things like this Rivers coming into existence can separate one group of animals from another and of course mountains Rising imagine an entire mountain chain rising in the middle of a continent or near the edge of a continent and separating one group off from another and in fact we see this frequently when we look at Mountain the animals are rapidly having
28:13
to evolve in response to the uplift of those mountains think of the Himalaya and it's very rapid growth around Mount Everest you know that the animals are having to adapt to those constantly changing situation or they have to leave okay so each population gets its own set of mutations in the manner that we just described over the last couple of slides and of course natural selection can speed the process this situation that we're looking up over here is the range
28:41
of different animals uh that are related to the um chimpanzees bonobos these are primates right so the red shade shows the Dominion of the bonobo over here the blue shading is the common chimpanzee over here and notice that where the bonobo is and where the chimpanzee here has very little in fact on this map there's no overlap between the two of them this is a classic example of allopatric speciation because there's a separate there's a separating barrier between the two of these in this fact
29:14
it's one of the largest rivers in the world the Congo River and so these two populations are completely separated from one another and they have no habitat in common okay and there are other species that show these separations also right here but this one here is clear's date you can clearly see that here we have the chimpanzee and here we have the bonobo right in this location with the Congo River separating the two classic allopatric speciation
29:51
Now by looking at all of the different animals and all the different plants and all of the different uh organisms bacteria and whatever that we're finding on planet Earth we can compare them we start to realize that certain patterns start to emerge by comparing them one to another one thing that we can do very easily for example is we can compare a human being to a chimpanzee and we recognize very rapidly well we're not chimpanzees but we're certainly much
30:17
more similar to a chimpanzee than we are to say a piece of algae that's floating in the water right we have we have hands we have the ability to walk you know we carry out reproductive abilities that algae does completely differently but we do have some things in common with algae we have certain traits that we have in common with algae and so and algae of course is very similar to other things that are very algae like so we have groups that we can compare things to and
30:45
one of the things that begins to arise is that we see these relationships and when they start to show up in Earth's history one of the great things about our ability to do this map all of this out is it allows us to produce something called a phylogenetic tree the phylogenetic tree is simply a diagram that shows the relationships among species groups and genes Etc that happen on planet Earth so speech I'm sorry scientists can trace how certain traits evolved some traits
31:13
evolved and were passed on right so we know that they came about they were passed on to descendants and that other traits evolved more than once for example the ability to fly swimming dinosaurs uh dinosaurs are really interesting right these are reptiles reptiles who uh evolved on land but their ancestors were amphibians which evolved in the water so we have these animals that came out of the water lost the ability to live in the water permanently and then we see reptiles
31:46
then re-entering the water and forming these ichthyosaurs which were huge animals by the way okay just absolutely fascinating animals so we have losing the ability to swim and now they could swim again right fascinating the ability to fly certain we actually recognize that certain species and and ancestors of birds gain the ability to fly and lose it gain it lose it gain it lose it and it's just kind of the way that Evolution works because sometimes it works to be a flyer and sometimes it
32:18
doesn't just depends on where you live look at a penguin you might be thinking yourself if I'm a bird I don't ever want to lose my ability to fly Penguins learned the ability to swim and they're fantastic swimmers so it just depends on your environment so let's look at this phylogenetic tree to show you a little bit about how it works now what we notice right away is it all stems from a common ancestor something that exists what does that common ancestor have well it has DNA it
32:45
has DNA and then once we if if that's all we have we just have kind of a blob of DNA within a cell structure that's a bacteria okay but if we have other features within the cell for example mitochondria which helps carry out metabolic processes within the within the cell nuclei whether or not the animal has organs you know maybe a stomach a heart liver right unlike uh unlike a an iguana for example uh conifers don't have organs what do conifers have well conifers they have seeds they carry out
33:20
photosynthesis this is a chloroplast which allows the uh the organism to carry out photosynthesis which is to say to take sunlight and use it to produce sugar right um and the same thing is happening all along here we see in this case organs are developed nerves and Vascular systems well jellyfish they have organs but they don't have nerves and Vascular systems and so on and so forth it just keeps going on we start to recognize that certain animals are very closely
33:48
related even if they don't appear to be related for example crocodiles are very closely related with birds okay um I if you had asked me prior to you know if I was just kind of a zoo Observer walking around I would never think that a crocodile was more closely related to a bird than it was to say a deer or something else right but they are and the reason why is they live in different environments they walk differently but they they clearly have a recent common ancestor a recent to them
34:21
common ancestor okay um and in fact the same thing is happening over here marsupials these are animals with pouches like the kangaroo is actually much more closely related to us than it is to say um an iguana or a lizard or you know lizards and snakes of course are clearly closely related but a snake is actually more closely related to a bird than it is probably to a marsupial all right now you may be of the impression that all we do is we look at modern animals
34:53
we can infer all of this history but the reality is is that we actually have a good understanding of what animals in the past look like even the ones that are no longer with us we call those extinct animals and we'll get into those here in a moment what is that record well it comes from fossils so a fossil is an imprint in stone of a dead organism for example here we see a 558 million year old fossil this is an animal that does not have um uh skeletons uh or skeletal material
35:25
it doesn't have teeth it doesn't have claws or anything like this it's a soft bodied uh you know as it's described here in the in the caption a mysterious jellyfish like red creature um and it existed prior to the existence of shells and all of these other things yet here we see it it clearly has what we call bilateral symmetry just kind of like what we have right one half mirrors the other half right and so here we see that bilateral symmetry right there in the mud okay
35:58
um and this type of record where we're looking at these old animals and as we're looking at the oldest animals they're very simple like these things like this jellyfish-like creature okay as we get to more recent times even as recently it's a 400 million years ago they get a lot more complicated and then when they get to 200 million years ago we start to see vast changes in the fossil record again and and right up until modern times and we're recognizing the animals are
36:28
constantly changing they're constantly altering themselves and we call that Evolution so we have that record what we call the fossil record which is the cumulative body of fossils worldwide now the fossil record shows that life has existed on planet Earth for at least 3.5 billion years and the reason why we know it's only the 3.5 billion it could be even older is because it's really hard to find rocks with fossils in them prior to that the Earth if you remember
36:55
from our previous lecture lecture number three in the series the Earth is constantly recycling its crust and as a consequence it's always erasing its surface and when it's erasing and it's destroying old rocks through the rock cycle and putting them into new forms and putting it to New use the fossil record is also being destroyed so it's really hard to get rocks that far back yet we do have definitive evidence actual fossils of animals from three and a half billion years old or older okay
37:27
and what we recognize is the simple process right the one we've been describing that earlier types of organisms evolved into later ones and that the number of species has increased over time we see this in the Rock record this is is actually in fact what we observe we also recognize that most species have gone extinct on Earth we see these really exotic things whether it be a T-rex or something like a trilobite which is a simple sea creature that lived on the seafloor for hundreds
37:55
of millions of years and then just went extinct okay yet they were an important part of Earth's ecosystem and a big part of our own ancestry and what gave us who we are as a as not just a species as of human beings but the entire palette of what the earth looks like right now um is really as a due to their existence and what they were doing now most species have gone extinct and there have been several mass extinctions in the past so sometimes they go extinct slowly
38:25
there's always kind of a background Extinction going on we'll talk about that here in a minute however these mass extinctions which is where animals suddenly die in Mass have happened several times in the past and have taken out uh large uh swaths not just of numbers of animals but entirely wipe the entire species out so that so that the biodiversity of that system had to be reset and evolution had to refill those holes whether it be the grasses out in the prairie or the animals living in the
38:58
ocean all right so now that we've talked about Evolution we've talked about the fossil record and the Origin of Species themselves what we call speciation um and we've introduced the concept of Extinction we need to talk about what Extinction is so Extinction is simply The Disappearance of a species from Earth we've discovered that the average species will last on Earth between 1 to 10 million years on average and this is the the fossil record that's really giving us this information now this is
39:27
important because it turns out that speciation and Extinction together are what determine biodiversity right so your speciation is the creation of new species whereas Extinction is the destruction of new species or a new new destruction of species I should say so over time species are going extinct Extinction has historically been a natural occurrence it's happening all the time it would happen every single day whether people were here or not uh to observe it it's just been going on
39:58
since the beginning of the origins of life on Earth the loss of a species is irreversible we can't bring it back and there's a very sad story here um that I want to show in this picture here this is the last Northern White Rhino we have that here in the caption he died on 3 20 2018 so in that'd be March 20th 2018. uh that was four months after this Photograph was was taken from this source that we have right here I retrieved it in November of 2017. and I've kept it for a very long time
40:32
because it's very sentimental to me this is the very last Northern White Rhino there were a few females that were remaining but this was the last of the of the males and as we talked about without the males you know the species tends to go pretty quickly because there's nothing to reproduce with at that point uh there's some uh interesting history about what's going on here what they're trying to do to be able to make sure that that ecosystem is taken care of by what the
41:00
Rhinos used to do for it but anybody who's interested in that can definitely delve into an internet search and again go down that rabbit hole and see what was going on there so let's talk about what causes Extinction what might be the effects of Extinction on say biodiversity so human activity profoundly affects rates of Extinction on Earth we've discovered this all over the place that biodiversity loss affects people directly it affects our food it has affected our fibers you know in the form
41:34
of forest and deforestation medicines are undoubtedly have been lost many of the medicines that we need for just for everyday use for some people are natural in the environment they're enhanced and they're sold through the pharmaceutical business but we discover them because nature already has it for us and of course ecosystem Services which we've talked about in previous lectures but this is the services the Clean Air the cleaning of the air the cleaning of the water that the and the
42:02
Rejuvenation of oxygen in the atmosphere all of these things are protection of your head from ultraviolet radiation is all provided for free by by the Earth right so it does seem to have some effect on certain aspects of these things Extinction can occur when the environment changes rapidly and natural selection cannot keep up so if natural selection cannot keep up and continuously fill the gap Extinction will eventually take over and it will cause damage to the ecosystem
42:34
and cause in in cause permanent harm many factors cause Extinction severe weather climate changes is a climate change image that we're having up over here this is a obviously a polar bear that's uh emaciated it's starving to death this is a place where the polar bear historically has been able to live but there has been a retreat of the ice sheet in the north and as a consequence we have this bear that is white which does really well when it's got snow and there's sea ice all around but it
43:07
doesn't do so well when there's no sea ice there's nothing to eat every uh it's prey can see it coming from miles and miles away and it gets out of the way so this this polar bear is definitely struggling at this location so climate change can do this changing sea levels can do this of course uh the arrival of a new species perhaps there's you know a better Predator that's in the area that's more effective at getting the food supply or give them that food source than you are and so it's able to
43:37
out compete you remove that food supply and you starve to death so a rival of a new species and of course being a small population or specialized species you can only live in a certain area because you only do a certain thing so panda panda bears do effectively this now of course there are specialized species all over the world and some of these species are extremely vulnerable to Extinction and in particular I want to focus on endemic species an endemic species are a
44:12
species that only exists in a certain specialized area so you it can only live here you can't take it somewhere else and have it effectively reproduce and Thrive and be prosperous and as a consequence this makes it very susceptible to Extinction um they usually have fairly small populations and this is really common on island species which are often endemic and thus at risk so if you take a a certain bird for example the one that we have right here is the Sunbird which
44:43
lives in South Africa it lives in a very narrow range I believe they call it the finbos range where it can only live in certain areas it performs certain functions and then once you get out of that area if you try to take the Sunbird somewhere else they can't survive it doesn't do well at all so this is an orange crusted or I'm sorry orange breasted Sunbird um from South Africa and it's endemic to that region it can't be moved anywhere else so let's look at what we now know about
45:16
Extinction on planet Earth over time first off there's the background Extinction rate it's what's happening all the time uh every single day it's the constant slow rate of Extinction that occurs as a part of evolution it's it's a part of life it's it's something that nature needs and uses it's a way of kind of gardening or when you're doing gardening you remove the weeds and you are constantly revitalizing the garden by removing those weeds and making room for New Growth that's what Extinction
45:45
technically is doing in the garden of evolution right it's weeding out species that no longer have a proper role that are ineffective or inefficient or might have some problem that has been corrected by another species however there are also mass extinction events that have happened throughout Earth's history and these are episodes that have killed off massive numbers of species all at once in a very short period of time it could be in a short period of time in the sense that the Earth was hit
46:17
by an asteroid or something like this or perhaps there was a climate event or there was uh maybe a disease or something that spread or maybe a combination of these things so that the extinction event lasted over maybe a million years but what we do know is is that we do have these events and some of them we know a lot about and some of them we don't know a lot about uh what we can see by looking at the fossil record is we have five very clear times in Earth's history where 50 to 95
46:45
percent of all species go extinct at one time the biggest event um I have these actually out of order over here down here the biggest event was 250 million years ago this is the end of the Permian and so 250 million years ago let's look at this timeline over here these are the extinction occurrence these are the percentages 250 million years ago we could see wow look at the number of species that we've lost right so this is the extinction occurrence percentage in terms of the
47:19
species themselves that went extinct 75 to 95 of all species went extinct this was a giant reset on The evolutionary button there were huge holes in the ecosystem that had to be filled and so a lot of things began to change and in fact it's from the end of the Permian into the end of the Cretaceous which we're going to talk about here in a moment we have another Extinction this is the famous KT Extinction this is the period of time called the Mesozoic and the Mesozoic is
47:50
famously known as the time of the dinosaurs so if it wasn't for the Permian Extinction which created this huge hole in the ecosystem in the biodiversity I should say and and gave rise through the through the ecosystem for these different land animals and sea animals to to proliferate um that gave rise to the uh to the reptiles and the reptiles became the dinosaurs and then of course 65 million years ago the dinosaurs went extinct right here and if it wasn't for their
48:22
Extinction it's very possible that mammals we are now living in a period of time called the age of mammals it's the cenozoic um from 65 million years ago to today you we notice that there's little little blurbs of extinctions in here but for the most part it's been pretty smooth sailing compared to what's happened in the past and we can recognize that here's another Extinction here's another Extinction here's one here's one here's one so that's five that we have
48:50
um and so we are the benefactors of our probably our greatest competitor the dinosaurs having gone extinct is it possible that human beings wouldn't exist had that not happened it's a great question to ponder
49:13
now we did bring up the idea earlier that human beings um do have the ability to affect and change things around them and it does appear that humans are might be causing the sixth Mass 16 Extinction event so we've talked about the five uh what are the types of things that we're doing well resource depletion population growth um development of homes and buildings uh destruction of natural habitats hunting and harvesting of species uh introduction of non-native species we
49:48
take plants and animals from one place and we put them in another place for example we are taking snakes from Indonesia the python and we're putting them in Florida where they don't live but they're able to out-compete the AL uh the alligator species and the Snake species that are already there as a consequence today's Extinction rate is 100 to 1 000 times higher than the background rate and Rising um and we believe that it's going to take millions of years for biodiversity
50:18
to recover what are the types of things that we might be hunting and harvesting species for well in this case these are it's illegal to do this but these are elephant tusks so how many elephants is this represented by well I'm not going to count up all the tusks but we know that elephants have two tusks per elephant and we clearly see that these two here seem to match even have the same coloration that's probably one elephant here's another one here's another one and so forth we're looking
50:46
at a large number of unfortunately dead elephants probably due to poaching in fact it says here in the caption the tests are from an eight million dollar shipment intercepted in Singapore so this is uh this is a major problem we have a similar thing going on with sharks specifically with shark fin soup the number of sharks that are getting captured and having their their fins removed just for the purposes of making this delicacy it's a very expensive delicacy but that also drives the demand
51:20
for the shark fin itself because it's so valuable so with that let's go ahead and conclude what I think was a very interesting conversation about Evolution biodiversity and Extinction and the way that they're interrelated to one another we're going to be doing more lectures that expand upon this and develop the entire fabric that is the ecosystem all around us the environment that is all around us and how it works and how it options on planet Earth if you're
51:50
interested I look forward to seeing you uh in those videos when those are posted um if you have any questions or comments please put them down in the comment section I look forward to seeing what you have to say with that said I'll see you next time take care bye
Here to help you learn
Sign in to keep a private conversation with your course tutor.
Ask me anything about the material…
Sign in to chat