hello we are going to continue with the diversity of life we've talked about the vertical dimension this is the scale of the hierarchy that we reviewed and it stretches from atoms to molecules all the way up to the biosphere the second dimension that we're going to examine today is a horizontal perspective and a horizontal perspective is a dimension that we're going to look at that goes across the diversity of organisms existing now and those from the past and the way that we organize this type of dimension is through taxonomy now we've talked a great deal about diversity and just to give you a little perspective biologists have identified about 1.8 million species compare the the number that we've identified to the number of actual species that we believe are out there and depending on who you talk to some scientists think that there's 10 million and then we have other scientists that say there's probably over a hundred million when you think about organisms that are so small that we can't see them that we haven't identified them or come across them one way that you can kind of make your own mark in life is if you head down to the rain forest take a net with you shake a tree you're bound to have some kind of beetle fall into your net that's never been identified and so you can take that beetle and send it off and they can look up its appearance and do some genetic testing and find out if it has ever been identified and if it hasn't you get to name it and you can name it after yourself so when they're looking this information up and they're looking at the dna or the genetics and they're looking at the coloring and the size and shape wings leg lengths structures things like that we group these organisms into categories and this is called taxonomy taxonomy is that part of biology that's going to name describe and classify species and this classifying of organisms into groups is based on how the different organisms are related or how they appear to be related to one another the taxonomic system categorizes living things and it was developed by carl linnaeus who was a swedish botanist and zoologist and physician in the 1700s things haven't changed too much in the way we name things and just like the vertical hierarchy that we discussed earlier the taxonomic system is also hierarchical the broadest group is referred to as a domain and each sublevel becomes more specific and the organisms are more similar now i like to view this perspective actually in the opposite direction as we did with the uh hierarchy of life where i like i like to start at the bottom and move from small to big in the classifying my own preference is to start at the largest hierarchy and move down so the largest that broadest group is considered the domain the next sub-level is the kingdom and then phylum class order family and genus sometimes it helps to make a little mnemonic uh people often say king philip came over for good spaghetti so right here we're missing the the term species right here so that smallest sublevel would be species we're also in this slide missing the largest which would be domain so let's take a moment and look at an example we can look at the classification of humans so if we start with the domain there are three domains and we'll look at those in a moment the three domains are eukarya bacteria and archaea and like i said we'll reserve that for just a moment so we're in the domain eukarya the next sub-level would be the kingdom the kingdom that humans fall into is animalia the phylum is chordata because we have a backbone it's a little bit more detailed than just saying you have a backbone but for the most part if you have a vertebrae then you'll fall into the phylum chordata our class is mammalia mammals are classified based on lactation and having fur the order is primate the family sub-level is hominidae the genus is homo and the species is sapiens so we are homo sapiens and homo sapiens if you translate it it's latin for wise man when you write homo sapiens you either have to italicize it if you're unable to italicize then you would have to underline it and the first word the genus is always a capital letter and the species would be a lowercase letter as of today homo sapiens are the only living humans on the planet there have been previous humans but they are all extinct so there's the neanderthals there's homo erectus there's a whole group and asu has a really great program and research department the institute of human origins and it's really really interesting if you have a chance to go over and go through the office it's really cool the uh at the discovery of lucy asu was part of that research team and so they have a really cool cast and information on lucy over there so okay let's move forward so i said we were going to talk about the domains which is that highest level on that hierarchy our horizontal hierarchy the diversity of life can be arranged into three higher levels called domains bacteria archaea and eukarya and bacteria are the most diverse and widespread prokaryotes and at this point you should be able to recall or answer a question about prokaryotes what's interesting about them what are their characteristics so if you don't recall make a note for yourself or right now you can pause it and write down what you know or what you remember about the characteristics of a prokaryote and then go back and see if you've covered everything archaea are also prokaryotes and these are microorganisms that live in extreme environments extremophiles are microorganisms they're highly adapted for these extreme conditions and the extreme conditions are the norm for them and they're able to metabolically and biochemically operate so what are some of these extreme environments well temperatures for example extreme temperatures extreme pressures or extreme phs radiation salinity energy and even a lack of nutrients some can even survive harsh conditions of space so we have found microorganisms in space attached to like space shuttles and things like that and in environments with extreme radiation this is an image of what's called a black smoker and it's deep in a c vent and what's coming out of that is hydrogen and sulfur so there's no light down there there's no nutrients at this level and yet these microorganisms are able to survive they're able to extract the sulfur the hydrogen and the sulfur to utilize as a nutrient and they're able to withstand these extreme temperatures um a deep sea vent like that can range in temperature from like 500 degrees to 750 degrees fahrenheit or possibly even higher so these are really unique organisms and then we have the eukarya this is our third domain and these are the organisms that are comprised of eukaryotic cells so again at this point you should be able to jot down in your notebook so please make a note and write down some characteristics of a eukaryotic cell and in this group we're going to find single-celled organisms like protis and if you had a high school biology class you may have looked into a microscope and observed some of these protists some examples are algae amoebas euglena plasmodium slime molds these are all protists some protists are capable of carrying out photosynthesis algae diatoms an organism called dinoflagellates and euglena they all are able to photosynthesize these organisms are often unicellular but they can form colonies as well and we also have the more familiar group of eukarya which are multicellular these are fungi animals and plants this is an image showing the three domains here we have the bacteria eukarya and archaea here's some fun pictures of the various domains so here right domain bacteria domain archaea and domain eukarya in the upper left we have some bacillus bacteria bacillus because of the shape if you have a rod shaped bacteria it's called bacillus right here we have archaea and over here we have our domain eukarya here's an example of a protist this is probably an amoeba right here in the upper right is our kingdom plantae so this is a beautiful plant kingdom fungi we have mushrooms these are our decomposers hopefully you have that written down in our your notes and then our kingdom animalia this is a sloth and the interesting thing about our sloth is notice this green greenish color fur inside of the fur is a particular organism that does photosynthesis and so that's why the organism has a green tinge to it if you look up photos of polar bears you can probably see polar bears with a green tinge to them as well the hair itself is kind of like a tube and so the microorganisms exist in those tubes so we have a symbiotic relationship going on here where the sloth is providing a an environment for those organisms to live the other thing that i wanted to point out right both of these bacteria and archaea are prokaryotes and these all are individual single celled here these organisms are not multicellular even though they kind of appear that way but each of these is independent of the one that they're next to but they do usually exist in colonies like this grouped together and we do talk about that in another chapter or lecture when we're looking at these in our i believe histology lecture so these are able to survive and exist independent from each other and these are simply colonies evolution is defined as the process of change that transform life on earth from its earliest beginnings keep in mind that the earth is 4.5 billion years old prokaryotes were the very first inhabitants they appeared about 3.5 to 3.8 billion years ago during a time referred to as the pre-cambrian period now we have these fossils fossils record our recorded documents and when darwin began his work biologists and geologists had begun to assemble and interpret the fossil record so what's a fossil a fossil is any trace of an organism that lived in the past and these traces can range from bones branches shells and dung to tracks or impressions left by an organism in soft sediments such as sand and clay and the fossil record consists of all the fossils that have been found on earth and described in scientific literature so life has been evolving on earth for billions of years and the fossil record documents that and it documents the pattern of ancestry how are these organisms related to one another this is an image of charles darwin most people relate his name to evolution but interestingly the idea of evolution was actually discussed by philosophers and scientists well before darwin's time including darwin's grandfather erasmus darwin what was unknown was how was evolution occurring the contribution that we're going to focus on from darwin is his discovery of this mechanism and darwin wasn't the only person that discovered the mechanism of evolution a colleague of his at the same time independently also proposed the same idea it's just that darwin published first so his colleague's name is alfred wallace the two of them both came up with the mechanism of evolution and how evolution occurs in 1859 darwin publishes his book on the origin of species by means of natural selection the publication of this book is generally regarded as the beginning of modern biology and another thing that was going on at the same time some experiments that were being carried out by an austrian monk by the name of gregor mendel he was working on the basics of genetics so during this time frame there was a really expansive knowledge and a lot of experiments and new things coming out that have led to where we are today now the main points in the origin of species are that species living today descended from ancestral species and what darwin called the descent with modification and that it occurred due to natural selection please make sure that in your notebooks you are putting an asterisk by natural selection is a mechanism for evolution natural selection occurs whenever two conditions are met one individuals within a population vary in characteristics that are heritable meaning traits that can be passed on to offspring and two in a particular environment certain versions of these heritable traits help individuals survive better and reproduce more than do other versions so if certain heritable traits lead to increased success in producing offspring then those traits become more common in the population over time and in this way the population's characteristics change as a result of natural selection acting on individuals so this is a key insight here natural selection acts on individuals but evolutionary change occurs in populations based on our previous lectures and information hopefully this is making sense to you so make sure that you're understanding evolution has changed over time something is evolved once that a trait a favorable trait has been passed through the population and it's this the trait is passed from parent to offspring because that trait enabled it to survive better than other versions and i want you to go back to an example of the desert rabbits with the large ears and make some notes in your notebook what do you remember about that adaptation those ears what did they what was the purpose the function of the ears being large and thin and how does it relate to natural selection and to evolution so put that in your notebook you can pause the recording or you can make a note to go back leave yourself some space in your notebook to fill that in also in nature we see that there's an ability for more offspring to be produced than what an environment can support so what does this mean this helps to make sure that the genes that you pass to offspring continue to be passed along so the offspring have to survive to an age of reproduction so that they too can reproduce if sea turtles only produced five eggs and those eggs hatch the little sea turtles then try to run to the ocean as quickly as they can so that they're not eaten by a predator they could be eaten by the predator before they even hatch or on their journey to the sea now once they if they make it to the sea then they also have to survive predation in the ocean as well as hunger if the sea turtle only produced five eggs under these circumstances the predation the journey to the sea hunger then the likelihood that those five offspring reaching a reproductive age is slim to none and the genes never get passed along so this is why sea turtles lay approximately a hundred eggs per nest and they also have multiple nests so they uh lay eggs more than a few times a year and the reason for this is that only one in one thousand survive to adulthood so this is why there's an overproduction of offspring so you can make those observations yourself just like i explained with the sea turtles you can observe that you can see how many you can also try to look at other examples of frogs and the number of eggs that get laid by frogs also um would follow this observation and you can draw two very logical inferences here that there is unequal reproductive success and we have discussed this several times so at this point this should be sounding familiar to you individuals with heritable traits best suited to the environment are more likely to survive and reproduce than less well-suited individuals we also have the accumulation of favorable traits over time so as a result of this unequal reproductive success over many generations an increasing proportion of individuals in a population will have the advantageous traits let's look at a hypothetical example here's an environment with a population of bugs and you can see that there's variation in this population some of the bugs are light-colored some are a grayish in between color and then others are have a dark darker color this color comes from the parents they inherited this color this trait and you can see that the background is really dark so some of the bugs are going to blend into their environment better than others now in this image we have our predator coming in this bird here and it's going to be hunting and eating the bugs the light colored bugs are going to stand out more so the bird is probably going to be eating and eliminating the individuals with the light color trait which is less advantageous than bugs that happen to have the darker color the darker bugs are more likely to survive and because they're more likely to survive they're more likely to reproduce now it doesn't mean that it's a given but we're talking about likelihood so if you happen to inherit a favorable trait you're more likely to survive and reproduce than if you inherit an unfavorable trait in this particular environment so you're less likely to survive and reproduce and that's what we see here so here the bird fed some of the bugs died some survived and the survivors reproduced so you see that the bugs that had the darker color were more likely to survive and pass that dark coloring onto their offspring the lighter colored bugs with less favorable traits were picked off and when you compare this last population here with the first you can see that it's changed there's a higher proportion of darker colored bugs than in the previous generations so we have an evolution a change in the characteristics of the population over time an important thing to note here is that when evolution occurs it's affecting the population our individuals do not evolve if you start out a white colored bug you're going to dye a white color bug even if you make it to successive generations if you're light color you die a light color so the perspective here that you really want to understand is that you're considering the characteristics of the entire population when you're talking about evolution now this is a hypothetical but i can give you a real life example and this relates to the peppered moth in england way back prior to the industrial revolution the tree bark was very light colored and so there were moths that had a light coloring and they blended in and camouflaged on the bark so they were less likely to be eaten by birds than the moths that were black when the other the industrial revolution occurred there was so much pollution and soot that it coated the tree bark so now we have a shift and a change so now the white moths that used to blend in no longer blended in and so the white moths were eaten by the birds more than the black moths and so we had a change in the population the population frequency of the light color moths decreased and the dark colored moths increased now when the pollution was addressed over time and regulations put in place the trees went back to having light colored bark and the frequency of the light and dark moths flip-flopped again so this is just an example of how selection operates darwin realized that numerous small changes in populations as a result of natural selection could eventually lead to major alterations of species the fossil record provides evidence of such diversification of species from ancestral species here is a phylogeny you can see and it includes organisms from elephants so this is a phylogeny tree for elephants and the previous these ancestors are all extinct if the line doesn't make it to the edge here if this branch doesn't extend all the way over then it's extinct so if you look down here you can see that currently modern elephants are right here we have two african elephants and an asian elephant and on the bottom on this x-axis so to speak here you have time so your organisms you can look at how far back did these organisms exist and when did they go to extinct so if we look at the woolly mammoth here it went extinct about 3700 years ago and you can also see that it appeared probably somewhere between three and four million years ago so you can use this this is a time reference of when organisms appeared and perhaps even disappeared or are they still living today and when you look at this this branch where the branches divide or split right here is a last common ancestor so right here would be the last common ancestor of this ancient elephant here and this one here if we look right here at this this is called a node this would be the last common ancestor between the woolly mammoth and our modern day elephants here now this is a really interesting story because we're still finding out information and getting new information from dna or genetic sequencing for a long time zoologists thought that there were only two species of modern elephants one asian and one african and those two species were elephants maximus which is the asian elephant and l'occidona africana which is our really big savannah elephant savannah elephant that you think about in the uh african savannas then there was the discovery of this elephant l'occidona cyclitus and it's a really small dwarfed elephant that lives in the forest so when you're looking at africa there's the big savannah and then there's a border where the there is a forestry there and that's where they discovered this elephant here and genetic analysis suggests that these two african elephants are different species you can see that the skull size and shape is different they're well one even their body size this is a much smaller elephant but look at the the ears are different the tusks are different this elephant here has tusks that are straight and they're pointed down where the big elephants that you're custom seeing on the savannah have these curved up tusks so how could this be well there's now a new elephant that's been added to the mix here and it's called the paleoloxin antiquis and it's been extinct for about 120 000 years this elephant roamed europe and western asia during the last ice age about 400 000 years ago and dna is showing that this supposedly european animal is actually the african forest elephant's closest relative so there's uh another study in addition to adding this new uh elephant to the mix here and at a genetic level this other group discovered that it may have even more in common with the modern african forest elephant than the african savannah elephant and this study changes everything we thought we knew about evolutionary history and ancestry of our modern elephants and their closest relatives so this these new studies are also demonstrating that the african elephant's lineages was not confined to africa the animals actually went out of the continent which we did not know this before and roamed europe and when this was happening there was a lot of interbreeding occurring and it was this interbreeding that left its genetic mark far from its original stomping grounds in africa and what's really cool is this paleoloxadon antiquis is known as a straight tusked elephant and it's because of its distinctive and somewhat bizarre appearance its ancestors paleo lochsan on recce lived in africa between 3.5 million and 100 000 years ago so fossils show that the straight-tusked elephants arrived in eurasia around 750 000 years ago so they actually left africa through the middle east and once it reached europe the paleoloxadon into quest had to adapt to the new conditions then a new environment and one of the uh areas its new home was the island of sicily and what happens to large animals when they end up on an island they evolve into a smaller species a dwarfed species and this occurs because they have to deal with the limited resources on islands now there's some dna evidence that is revealing a particular dwarf elephant actually being more closely related to the asian elephant so how was this possible this makes no sense how could the straight test elephant be related to african elephants and the and its dwarf descendant be related to asian elephants well the new study with paleolocitin antiquis its dna helped to unravel this mystery and because the paleoloxadon antiques dna appears to be a mixture of many species dna so this would have happened when all of that interbreeding was going on so this is a process known as admixture and it probably occurred once the paleoloxadon left africa so that's how its descendants ended up with asian elephant dna and even dna from the woolly mammoth so it is possible that a small chunk of the dwarf elephant's dna that was analyzed years ago was extracted from a just a sequence a fragment that was inherited from the asian elephant and the other origins the woolly mammoth genes and the african elephant genes were not picked up in that particular analysis so um are you going to be questioned about which elephant came from where and all of that no this is just really cool information and it's showing you how the fossil record dna genetic sequencing all of this is giving us so much information to be able to construct these this horizontal hierarchy of organisms and how they're related when ancestor between those two organisms between those two elephants okay that's going to conclude this recording and this group of slides for our themes of biology