Evolution & Classification of Life | Single Celled Bacteria to Humans

today I'm going to show you the step-by-step evolutionary journey from the earliest single-celled organisms all the way to modern humans I'll be using my evolution and classification of life chart which is available as a poster from my website useful charts calm as the title suggests this is both an evolution chart and a classification chart so it not only shows how living things are connected from an evolutionary point of view it also shows the categories that are used to classify living things so you'll be hearing familiar terms such as kingdom phylum class and order this video is part of a two channel collaboration with fellow youtuber Stefan mellow whereas I will be describing the full journey of human evolution Stefan will be talking about some of the quirks in that process which demonstrate that our bodies were not designed from scratch but rather bear traces of a long history of adaptation so make sure you check his video after this one [Music] [Music] so we're going to start at the bottom of the chart with the emergence of life about four billion years ago that life would have been in the form of single-celled organisms similar to the bacteria of today now I'm not going to discuss how that first cell came to exist because that's something that is beyond the scope of evolutionary theory however there are several ideas out there about how that happened so if you're interested in learning more about that you'll want to search for the term abiogenesis I'm also not going to talk about viruses you can see how I've placed them off to the side here because there is currently some disagreement over how exactly they relate to life and whether they evolved before or after bacteria but what we do know is that life eventually proceeded in three different directions these are called domains and they are the top classification level coming before the more well-known kingdom level so we have bacteria which includes single-celled organisms that often cause infections in humans such as cholera or tetanus then we have archaea which are kind of like bacteria and can sometimes be found in really extreme environments such as super hot or super salty conditions and then finally and most important to us is the eukaryote domain eukaryote means true cell and is so labeled because eukaryotes have cells with a nucleus and other inner parts this originally occurred because of a process known as endosymbiosis in which several different types of cells came together to form one big cell that was more complex this likely occurred about two billion years ago from this point life again proceeded in three different directions first there were different types of algae that eventually evolved into the plant kingdom second there were various types of mold that evolved into the fungus kingdom and then third there were several amoeba like organisms that evolved into the animal kingdom all of these simple forms of life are called protists and in fact they can actually be divided into a bunch of mini kingdoms the fungus kingdom of course includes the familiar mushroom but also things like yeast and the mold that grows on bread but this chart is mostly concerned with the two really big kingdoms plants and animals and since we're mostly going to be looking at the animal side let's quickly look at the plant side before we do so so from red algae and brown algae eventually came green algae plants are green because they have a special part of their cell that other living things do not have this is called a chloroplast and it's the part that captures energy from the Sun through a process called photosynthesis from algae came the earliest types of land plans such as moss that occurred about 450 million years ago from there we get these simplest types of plants with branches and leaves like ferns next we get a really important development we get plants that bear seeds and thus are able to replant themselves over longer distances and it is at this point that the plant kingdom splits into two main divisions we get conifers which are trees with cones such as pine trees or cypress trees and then we get angiosperms which are trees and plants with flowers now interestingly flowering plants actually evolved relatively late in Earth's history only about 150 million years ago that's halfway through the age of the dinosaurs and when I say flowering plans I'm not just talking about things like tulips roses and daisies I'm also talking about the food that we eat everything from wheat and rice to fruits vegetables and even chocolate all of those things come from flowering plants okay what we really want to focus on though is the animal kingdom most people will be surprised to learn that a sea sponge is actually an animal it might look like a plant but it's actually comprised of a bunch of simple animal cells bunched together from this point what happened is that different cells evolved to perform different types of jobs such as those involved in movement so for example we eventually get gel fish a jellyfish is still a very simple creature but unlike a sea sponge it can move around this is because it has nerve cells that send electrical signals to certain parts of its body causing those body parts to jerk and thus causing itself to swim now keep in mind as we go step-by-step that each new development along the evolutionary journey took millions if not tens of millions of years to occur so none of these changes happened fast a million years is a really long time and it's really hard for our brains to think using numbers that are that big so just remember that evolution occurs because the mechanisms involved such as mutation and natural selection have really really long periods to work with ok so around 550 million years ago we get what's called the Cambrian explosion that's when we get animal life starting to go in a bunch of different directions and it all started with something called bilat teria if you look over at this flat worm here you'll notice that one side of it mirrors the other side well this is basically true for all animals from this point forward including humans that's why we have two eyes two arms two legs and so forth from here animals can be divided into two categories protostomes and deuterostomes protostomes include the various worm phyla as well as the phyla arthropoda and moleska phylum Arthropoda is comprised of all those creepy crawly things that most humans tend to hate like spiders and insects but also larger creatures like lobsters phylum Mollusca is comprised of creatures with hard shells like snails and clams but also some really intelligent sea creatures such as octopi and squid it is from early deuterostomes that the vertebrates eventually evolved all vertebrates belong to the phylum Chordata and they differ from invertebrates shown in purple in that they possess a backbone or spine that long column of bones that runs down the back and protects the spinal cord the earliest vertebrates were all fish first jawless fish and then fish with jaws and teeth after this point we then get Kartal creatures like sharks but also for the first time creatures that have what we consider to be a full skeleton the bony fish bony fish can be divided into two main categories most fish are ray-finned fish these include all the familiar types of aquarium fish such as tetras Guppies and goldfish and also all the fish that humans tend to eat like cod halibut and salmon the lobe-finned fish are quite a bit different they have downward facing fins with more muscles in them eventually this feature led to the evolution of certain fish that could prop themselves up in shallow water like the now extinct Tiktaalik from a creature similar to Tiktaalik came the tetrapods tetra meaning four and pod meaning feet so tetra pods are animals with four limbs which basically includes all of the animals that we tend to think of as being animals first off there's the amphibians like frogs who live both in the water and on land but then something evolved called the amniotic sac which allows some animals to lay their eggs on the land instead of in the water from this point animal life preceded in two very different directions we get the early synapsids that eventually evolved into mammals and we get these sirop seeds that eventually evolved into reptiles and birds since we'll be focusing mostly on mammals from this point forward let's quickly look at these sir opsins before we do so the three main reptile orders that still exist today are the crocodiles the lizards and the turtles most of the other orders are now extinct such as the fish like plesiosaur x' and egg Theo Soares and the bird like pterosaurs although those groups are sometimes called dinosaurs the term dinosaur technically only refers to these two orders here sirisha and ornithischian horny theisha which means bird hipped includes dinosaurs like Triceratops and Stegosaurus whereas sericia which means lizard hipped includes the huge long herbivores called sauropods as well as the carnivores called theropods in the theropod group we get the infamous t-rex as well as the Raptors the theropods are also important because it is from that group that Birds eventually evolved one of the earliest being the Archaeopteryx now you might have thought that birds would have evolved from the bird hipped dinosaurs but take note that they actually evolved from the lizard hipped dinosaurs and in particular from the theropods the technical term for birds is Aves so the bird class is called the avian class note that the ancestors of game birds like chickens and ducks evolved first and then we get a large group known as the Neo Aves or new birds where we find all sorts of familiar birds like Eagles pigeons and crows okay let's now go back to the synapse I'd line the earliest synapsids looked a lot like reptiles sort of like these paliku soar here but eventually their skeletal and organ structure evolved along a very different path initially this had a lot to do with movement if you watch a lizard move you'll notice that they tend to waddle from side to side whereas a dog has the ability to run in more of a galloping style this is a very rough way to explain the initial difference the first big group of synapsids were the therapsids and from them evolve the cynodonts eventually the cynodonts developed one of the key features of the mammal class they became warm-blooded which meant they also evolved hair or fur in order to regulate their temperature of course the other thing that sets mammals apart is that they possess mammary glands which they use to feed their young in fact this is where the word mammal comes from one of the earliest types of mammals that still exists today is the duck-billed platypus they belong to the monotreme order and most people think they look awfully strange but most mammals belong to a group called theory a-- which simply means beasts there are two major categories of beasts marsupials and placentals and the fact that they evolve differently had a lot to do with geography for example today we only find marsupials in the Americas and in Australia marsupials such as the kangaroo or opossum grow their babies in a pouch whereas placentals have a placenta and are thus able to grow their babies inside and give birth to them when they are more well-developed I should note that up until the time that modern humans arrived in Australia there are all sorts of other types of marsupials types that we don't see today including marsupials that looked like cats and marsupials that looked like bears but let's continue with the placental line some of the oldest branches of this group eventually lead to elephants as well as sloths and armadillos but another branch leads to the boreal youth theory a group which has two main categories larae atheria and the supra primates humans are super primates so let's look at laurasia atheria first lots of well known animal species belong to Laurasia therea including all of those that are carnivores the carnivore order includes bears dogs and cats but also sea creatures such as seals and walruses larae atheria also includes the ungulates which are the animals with hooves those with an odd number of toes are called pari so dactyls and include horses and rhinos those with an even number of toes are called artiodactyls and include farm animals like pigs cows and sheep but also animals with antlers like deer interestingly dolphins and whales are also closely related to the artiodactyls they evolved from land animals that eventually returned to the sea ok let's look at these super primates from the original super primates evolved rabbits and rodents but also the earliest types of actual primates we tend to associate primates with monkeys but the primate order also includes animals such as tarsiers and lemurs monkeys as well as apes belong to a special group of primates called simians a lot of people use the word monkey and ape interchangeably or really they are quite different apes do not have tails and are generally quite a bit larger and smarter it is of course from the early ape species that humans evolved currently there are only four kinds of great apes orangutangs gorillas chimpanzees and humans but over the last 15 million years there have been many other kinds as well it's important to remember that the great apes of today all evolved from these now extinct species not from each other so although you may sometimes hear it said that humans evolved from chimpanzees this is actually not true both modern humans and modern chimps evolved from a now extinct common ancestor who lived about 7 million years ago to us that creature probably looked more like a chimpanzee than a human but really they were equally both from that common ancestor evolved the now extinct genus known as Australopithecus which included the female known as Lucy whose skeleton was found in Africa in the 1970s and dated to about three million years ago Australopithecus is thought to be one of the earliest Apes to walk primarily on two feet from Australopithecus evolved the genus Homo which is the genus that modern humans called Homo sapiens belong to currently Homo sapiens is the only species in this genus but over the last two and a half million years many other homo species have come and gone we know this from the archaeological record which gets larger and better every year one of the earliest homo species was Homo habilis they were among the first humans to start extensively using tools then there was Homo erectus the African version of which is now called Homo ergaster they are thought to be the direct ancestor of Homo heidelbergensis from which came homo sapiens are close cousins the Neanderthals and a recently discovered group known as the Denisovans you only have to go back around 50,000 years in history to find more than one human species still existing on our planet at that time the Neanderthals and the Denisovans were still around as was Homo Florin Sciences the hobbit-like species that lived on an island in what is today Indonesia but of course nowadays Homo sapiens is the only human species left I've chosen a member of the South African sand tribe to represent our species since genetically they are closer to the ancestor of all living humans than any other group on earth so there you have it a step-by-step look at how modern humans evolved all the way from single-celled organisms of course there's a lot more that could be said on the topic and in this video I wasn't able to go into all the various lines of evidence that support the theory of evolution however fellow youtuber Stefan Mello has made a video that starts to scratch the surface of that subtopic be sure to click the prompt at the end of this video or click on the link in the description if you find history genealogy and monarchies interesting be sure to subscribe to the channel if you check the playlists you'll find that I have videos covering the family trees of famous dynasties from all over the world and to see what else I'm up to follow me on Twitter or Instagram thanks for watching

Channel: undefined

Views: 320,435

Rating: 4.9058614 out of 5

Keywords: evolution from bacteria to humans, evolution from single cells to humans, evolution tree of life

Id: HpXaiG8L28s

Length: 17min 55sec (1075 seconds)

Published: Mon Nov 11 2019

Reddit Comments

[u/Brovio]

I really dislike this phylogeny. It over represents mammals (to no surprise) and is ripe with polytomies. Many of the evolutionary relationships depicted in the chart are resolved. This is how misconceptions about evolution originate. When mammals are taking up 1/4 of the tree space and you have homo sapiens at the top-center it can mislead someone into thinking evolution is goal oriented, that furry animals make up most of life, or that humans are "more evolved" than other species. Communicating evolutionary principles to a lay audience, or even experts in the field, is a challenge. However we can certainly do better than this.

[u/bgwinup]

Is there a website that has a flow chart of every single mapped organism?

[u/misterfall]

Cool chart!! Hate to be the actually guy but this topology is extremely outdated. The currently accepted story is even more fascinating, with the greatest hits being eukaryogenesis from archaea and bacteria “fusing” and the truly monstrous diversity of protists.