1 00:00:00,820 --> 00:00:10,820 Hello! This is the video about the Phanerozoic Eon, which, as you already know, started 545 million years ago 2 00:00:10,820 --> 00:00:14,820 and is still the Eon in which we live. 3 00:00:14,820 --> 00:00:23,820 Then, as I explained in class, rocks from times before this Eon, before the Phanerozoic Eon, 4 00:00:23,820 --> 00:00:35,100 not show fossils of any animals from the types of animals okay that exist currently okay and 5 00:00:35,100 --> 00:00:41,899 i remind you that in the taxonomy in the classification of living things phyla are 6 00:00:41,899 --> 00:00:48,700 the different basic types of whatever kingdom of living things we are speaking about if we 7 00:00:48,700 --> 00:00:55,659 are speaking about animals the phyla are the basic types of animals okay and the singular of phyla is 8 00:00:55,659 --> 00:01:05,579 a phylum so before this time before 545 million years ago there were living things on the planet 9 00:01:05,579 --> 00:01:13,340 but there were no animals like the animals that exist now except perhaps some sponges and a 10 00:01:13,340 --> 00:01:23,980 jellyfish that existed around 600 to 550 to 550 million years ago okay so apart from sponges and 11 00:01:23,980 --> 00:01:29,659 jellyfish there were no animals like the ones that exist now then as i explained in class 12 00:01:31,579 --> 00:01:39,019 almost all the different types of animals that exist now and this means almost all the different 13 00:01:39,019 --> 00:01:48,719 animal phyla appeared in a short time short time means hundreds of thousands of years okay in a 14 00:01:48,719 --> 00:01:57,319 few hundreds of thousands of years almost all the different animal phyla appeared hundreds of 15 00:01:57,319 --> 00:02:03,420 thousands of years for a person is a lot but from the point of view of geology it is almost nothing 16 00:02:03,420 --> 00:02:08,960 so it is a sudden appearance in a very short time short from the point of view of geology 17 00:02:08,960 --> 00:02:18,180 almost all different types of animals appeared of course when i say types of animals i do not mean 18 00:02:18,180 --> 00:02:27,439 different the well the species that exist now okay what i mean is that for every basic type of animal 19 00:02:27,439 --> 00:02:34,639 represent different representatives different species that do not exist now ancient species 20 00:02:34,639 --> 00:02:43,639 that represent the basic types of animals appeared at this time, at 545 million years ago. 21 00:02:43,639 --> 00:02:50,639 Then this marks the beginning of the Cambrian period. 22 00:02:50,639 --> 00:02:59,639 The Cambrian period is the first period of the Paleozoic era, which is the first era of the Phanerozoic eon. 23 00:02:59,639 --> 00:03:12,639 Then since this sudden appearance of life, this explosion of life, happened at the beginning of the Cambrian period, this is called the Cambrian explosion. 24 00:03:12,639 --> 00:03:16,639 And I explain this in class. 25 00:03:16,639 --> 00:03:27,639 Then everything that we have studied that happened on Earth before this time, before 545 million years ago, is called the Precambrian. 26 00:03:27,639 --> 00:03:41,860 So precambrian is everything that happened before, the Cambrian explosion, which is the explosion of life of different types of animals that existed and that still exist now. 27 00:03:42,639 --> 00:03:54,919 Then the Phanerozoic is divided into three eras, and the three eras are called the Paleozoic, the Mesozoic and the Cenozoic eras, each of which is divided into periods. 28 00:03:54,919 --> 00:04:07,080 So the first era, the Paleozoic era, started with the Cambrian explosion 545 million years ago and finished 250 million years ago. 29 00:04:09,199 --> 00:04:15,300 The trilobites are the typical fossils of the Paleozoic era. 30 00:04:15,599 --> 00:04:24,879 So these animals lived in the ocean and they were arthropods, so animals with jointed legs and exoskeleton. 31 00:04:24,879 --> 00:04:36,879 There are no trilobites now, but the fact is that these representatives of the arthropods appeared 545 million years ago. 32 00:04:36,879 --> 00:04:42,879 So the phylum arthropods appeared 545 million years ago. 33 00:04:42,879 --> 00:04:50,879 The arthropods that existed at that time are different from the arthropods that exist now, but they were arthropods. 34 00:04:50,879 --> 00:05:01,879 So the different phyla appeared 545 million years ago, even though the species that existed then are different from the species that exist now. 35 00:05:01,879 --> 00:05:13,879 Then trilobites are one example of arthropods. There were other arthropods at this time, like eurypterids, so these kind of scorpions from that time. 36 00:05:13,879 --> 00:05:24,879 But not only animals, ok, also different plants appeared, and what is very important is that terrestrial plants appeared during the Paleozoic era. 37 00:05:24,879 --> 00:05:37,879 Most of the plants during the Paleozoic era were plants that depended on water to reproduce, the same as mosses and ferns do now. 38 00:05:37,879 --> 00:05:46,639 We studied this in the first test, so that most sun ferns can only reproduce if there is liquid water for their sperm cells to swim. 39 00:05:47,379 --> 00:05:57,040 But near the end of the Paleozoic era, then different plants appeared, plants that reproduce with pollen and seeds. 40 00:05:57,660 --> 00:06:06,779 So the plants that reproduce with pollen and seeds do not need water, because they do not need sperm cells to swim in water. 41 00:06:06,779 --> 00:06:13,819 they reproduce with pollen and seeds and it means that they may reproduce even if there are dry 42 00:06:13,819 --> 00:06:20,220 conditions. So the plants that reproduce with pollen and seeds appeared near the end of the 43 00:06:20,220 --> 00:06:30,139 Paleozoic era. Then vertebrates are animals that belong to a phylum, the phylum Chordates. Then 44 00:06:30,139 --> 00:06:35,980 the phylum chordates appeared also in the cambrian explosion 545 million years ago 45 00:06:36,540 --> 00:06:43,180 the first chordates were not vertebrates but bit by bit the first chordates evolved into vertebrates 46 00:06:43,180 --> 00:06:50,939 and the first vertebrates that appeared were fish and as we studied in first so most fish evolved 47 00:06:50,939 --> 00:06:57,579 into other fish that evolved into other fish etc but some fish evolved into amphibians most 48 00:06:57,579 --> 00:07:05,579 Most amphibians evolved into amphibians that evolved into other amphibians, but some amphibians evolved into reptiles. 49 00:07:05,579 --> 00:07:16,579 In the Paleozoic era, the only vertebrates that existed were first fish, then later also amphibians, and later also reptiles. 50 00:07:16,579 --> 00:07:26,579 Here you have images of fossils of the trilobite and the eurypterid, and these are plant fossils. 51 00:07:26,579 --> 00:07:29,819 These are ferns from the Paleozoic era. 52 00:07:29,819 --> 00:07:36,259 Then near the end of the Paleozoic era, Pangea formed. 53 00:07:36,259 --> 00:07:43,660 So the continents merged forming Pangea near the end of the Paleozoic era. 54 00:07:43,660 --> 00:07:52,920 And also the last period of the Paleozoic is called the Pyramian, and at the end of 55 00:07:52,920 --> 00:07:59,620 the Permian, there was the worst, the greatest, massive extinction known, okay? 56 00:08:00,100 --> 00:08:05,620 So at the end of the Paleozoic era, at the end of the last period in the Paleozoic era, 57 00:08:05,620 --> 00:08:14,439 the Permian, an enormous number of animal and plant species got extinct, and this includes 58 00:08:14,439 --> 00:08:16,259 the last trilobites, okay? 59 00:08:16,360 --> 00:08:20,420 So the last trilobites died at the end of the Paleozoic. 60 00:08:20,980 --> 00:08:22,800 Why did this extinction? 61 00:08:22,920 --> 00:08:29,959 happen? We don't know. We don't know the reasons for this massive extinction, the 62 00:08:29,959 --> 00:08:36,000 worst massive extinction that we know of. The fact is that there is a big 63 00:08:36,000 --> 00:08:41,519 difference in the fossil record, a very big difference between the end of the 64 00:08:41,519 --> 00:08:46,919 Permian, this means the end of the Paleozoic era, and the beginning of the 65 00:08:46,919 --> 00:08:53,759 next period. The next period is called the Triassic and the Triassic is the 66 00:08:53,759 --> 00:09:00,659 first period of the Mesozoic era. So this extinction event was so 67 00:09:00,659 --> 00:09:06,419 terrible that scientists consider it to be the end of one era, the end of the 68 00:09:06,419 --> 00:09:11,679 Paleozoic era and the beginning of the Mesozoic era. And this terrible mass 69 00:09:11,679 --> 00:09:19,600 extinction event is called the Permian-Triassic mass extinction because it is the mass extinction 70 00:09:19,600 --> 00:09:26,799 that happened at the end of the Permian and at the beginning of the Triassic. So this mass extinction 71 00:09:26,799 --> 00:09:35,120 was the beginning of the Mesozoic era. The Mesozoic era then started 250 million years ago when that 72 00:09:35,120 --> 00:09:41,539 mass extinction happened and it ended 66 million years ago, which as we will see 73 00:09:41,539 --> 00:09:47,480 is also the time of a mass extinction. So mass extinctions are the borders 74 00:09:47,480 --> 00:09:56,700 between one era and the next. Then the new fauna that evolved after the awful 75 00:09:56,700 --> 00:10:03,940 Permian-Triassic mass extinction was dominated by reptiles. That's why the 76 00:10:03,940 --> 00:10:11,960 The Mesozoic era is also called the era of the great reptiles or the era of the dinosaurs. 77 00:10:11,960 --> 00:10:17,419 During the Triassic period, which is the first period of the Mesozoic era, some reptiles 78 00:10:17,419 --> 00:10:19,220 evolved into mammals. 79 00:10:19,220 --> 00:10:26,360 So mammals evolved and appeared at the beginning of the Mesozoic era in the Triassic period. 80 00:10:26,360 --> 00:10:33,360 And later, after the Triassic period, we have the Jurassic period. 81 00:10:33,360 --> 00:10:38,100 And in the Jurassic period some dinosaurs evolved into birds. 82 00:10:38,100 --> 00:10:45,200 As we can see here in this fossil, this fossil is the fossil of a dinosaur that had feathers 83 00:10:45,200 --> 00:10:48,980 and it was probably able to fly like a bird. 84 00:10:48,980 --> 00:10:55,720 Scientists cannot really say whether this is one of the first birds or simply a dinosaur 85 00:10:55,720 --> 00:10:59,399 that is in the branch of evolution that led to birds. 86 00:10:59,399 --> 00:11:03,139 The fact is that birds evolved from dinosaurs. 87 00:11:03,139 --> 00:11:14,220 Here you can see an image of a lot of dinosaurs, but not only dinosaurs dominated the world 88 00:11:14,220 --> 00:11:15,220 at that time. 89 00:11:15,220 --> 00:11:19,860 There were other reptiles that were not dinosaurs. 90 00:11:19,860 --> 00:11:25,620 Some were able to fly and they were pterosaurs, like the ones here, and some lived in the 91 00:11:25,620 --> 00:11:32,820 oceans like mosasaurs, plesiosaurs and ichthyosaurs. This is an ichthyosaur, this is a plesiosaur, 92 00:11:32,820 --> 00:11:40,019 this is a mosasaur. So all these were reptiles that existed during the Mesozoic era but they were 93 00:11:40,019 --> 00:11:45,779 not dinosaurs. Their skeleton is very different from the skeleton of dinosaurs and they are not 94 00:11:45,779 --> 00:11:54,710 considered dinosaurs. Apart from reptiles there were a lot of invertebrates that became very 95 00:11:54,710 --> 00:12:01,110 numerous in this era and the most characteristic are the ammonites that well which you have already 96 00:12:01,110 --> 00:12:09,350 seen in the lab that we did with fossils okay the ammonites we saw in the lab were the small ones 97 00:12:09,350 --> 00:12:14,789 but as you can see some were really big and this is how the animal looked when it was alive okay 98 00:12:17,799 --> 00:12:23,720 and if we speak about plants during the Triassic and Jurassic periods 99 00:12:23,720 --> 00:12:31,720 There were seed plants that were very numerous, but those seed plants did not produce fruits. 100 00:12:31,720 --> 00:12:43,720 The most typical example of these plants that reproduce with seeds but do not produce fruits are the conifers, because they have cones. 101 00:12:43,720 --> 00:12:47,720 Pines and firs are examples of conifers. 102 00:12:47,720 --> 00:12:54,720 So these plants were extremely abundant during the Triassic and the Jurassic periods, ok? 103 00:12:54,720 --> 00:13:02,720 But then near the end of the Jurassic, in evolution, the plants that reproduce with fruits appeared, ok? 104 00:13:02,720 --> 00:13:05,720 And those plants are called angiosperms. 105 00:13:06,720 --> 00:13:15,720 Then if we look at the continents, what we see is that during the Triassic, Pangea split into different continents. 106 00:13:15,720 --> 00:13:24,960 First, it split into two big continents and then those two big continents in turn separated into other continents that were moving 107 00:13:24,960 --> 00:13:30,960 and they were moving towards an arrangement very similar to the current one, okay? 108 00:13:31,639 --> 00:13:42,159 During the Mesozoic era, during the era of the dinosaurs, our peninsula, the Iberian Peninsula, was mostly underwater, okay? 109 00:13:42,159 --> 00:13:47,679 So only a few parts of the Iberian Peninsula were emerged and were dry land. 110 00:13:47,820 --> 00:13:49,539 Most of it was the bottom of the ocean. 111 00:13:51,279 --> 00:13:57,259 Then, in the last period of the Mesozoic era, which is called the Cretaceous period, 112 00:13:57,960 --> 00:14:04,539 the angiosperms, the plants that reproduce with fruits that had appeared at the end of the Jurassic, 113 00:14:05,139 --> 00:14:10,019 during the Cretaceous period became extremely numerous and diverse 114 00:14:10,019 --> 00:14:13,220 and in the end dominated the continents, as they do now. 115 00:14:13,480 --> 00:14:17,399 So the dominant plants now on Earth are the angiosperms. 116 00:14:17,860 --> 00:14:20,480 They appeared near the end of the Jurassic, 117 00:14:20,639 --> 00:14:24,340 but it was during the Cretaceous period that they expanded. 118 00:14:25,720 --> 00:14:28,860 And then we reach the end of the Mesozoic era, 119 00:14:29,059 --> 00:14:33,399 and as I said, the end of an era means mass extinction event. 120 00:14:33,980 --> 00:14:37,399 So the third period of the Mesozoic era, the Cretaceous, 121 00:14:37,399 --> 00:14:45,679 ends with a mass extinction. This mass extinction is not as terrible as the one at the end of the 122 00:14:45,679 --> 00:14:52,299 Permian. So it is not the worst, but it is the second worst mass extinction event that we know. 123 00:14:53,320 --> 00:15:01,480 So in this mass extinction event, the last dinosaurs that were not birds died, okay? 124 00:15:01,480 --> 00:15:10,600 birds are dinosaurs, okay? So not all dinosaurs got extinct, okay? Only the non-avian dinosaurs. 125 00:15:10,600 --> 00:15:18,919 Then ammonites, pterosaurs, mosasaurs, plesiosaurs, etc. also disappeared. And they disappeared 126 00:15:18,919 --> 00:15:26,960 suddenly, okay? So this was a mass extinction event. Why did this happen? Well, looks like it 127 00:15:26,960 --> 00:15:28,960 was because of the fall of an asteroid. 128 00:15:28,960 --> 00:15:30,960 As probably many of you know, 129 00:15:30,960 --> 00:15:34,960 this asteroid made the Earth inhospitable 130 00:15:34,960 --> 00:15:37,960 for animals bigger than a couple of kilograms. 131 00:15:37,960 --> 00:15:42,960 So big animals got extinct in this mass extinction event. 132 00:15:42,960 --> 00:15:45,960 The change in the fauna was so big, 133 00:15:45,960 --> 00:15:47,960 as we can see in the fossil record, 134 00:15:47,960 --> 00:15:50,960 that geologists considered this mass extinction 135 00:15:50,960 --> 00:15:52,960 to be the end of an era, 136 00:15:52,960 --> 00:15:54,960 the end of the era of the dinosaurs, 137 00:15:54,960 --> 00:16:01,679 of the dinosaurs, the end of the Mesozoic era, and the beginning of the next era, the Cenozoic era. 138 00:16:02,879 --> 00:16:11,120 The beginning of the Cenozoic era is the Paleogene period. So the mass extinction event 139 00:16:11,120 --> 00:16:19,519 that eliminated the last non-avian dinosaurs was the mass extinction event at the end of the 140 00:16:19,519 --> 00:16:24,440 the Cretaceous Period and at the beginning of the Paleogene Period, so it is called the 141 00:16:24,440 --> 00:16:28,240 Cretaceous-Paleogene Mass Extinction. 142 00:16:28,240 --> 00:16:35,779 But when scientists abbreviate it, they use older names and also in German, so it is called 143 00:16:35,779 --> 00:16:41,019 the KT Mass Extinction Event, okay? 144 00:16:41,019 --> 00:16:49,500 KT Mass Extinction Event represents Cretaceous-Paleogene Mass Extinction, the end of the last non-aging 145 00:16:49,500 --> 00:17:01,639 So then is the beginning of the Cenozoic era, which is the era in which we live, which started 66 million years ago. 146 00:17:01,639 --> 00:17:10,640 And in this era, the animals that have expanded and diversified a lot have been the mammals. 147 00:17:10,640 --> 00:17:19,640 So mammals have become dominant on the planet. They have colonized all the different continents and the oceans. 148 00:17:19,640 --> 00:17:24,640 But of course, this doesn't mean that only mammals have evolved. 149 00:17:24,640 --> 00:17:28,640 All living species evolved with time, as we will understand in the future. 150 00:17:28,640 --> 00:17:33,640 All living species evolved, so the other living things have also been evolving. 151 00:17:33,640 --> 00:17:42,640 Different kinds of birds, reptiles, amphibians, fish and invertebrates have appeared, evolved during the Cenozoic era. 152 00:17:42,640 --> 00:17:47,640 One of the famous ones is the gigantic shark megalodon. 153 00:17:47,640 --> 00:17:57,640 Below you can see a tooth of Megalodon, that gigantic shark, although it was not as big 154 00:17:57,640 --> 00:18:02,099 as it is depicted in some movies or documentaries. 155 00:18:02,099 --> 00:18:06,759 It was very big, but it was not as big as a blue whale, for instance. 156 00:18:06,759 --> 00:18:10,220 The blue whale is the biggest animal we know of. 157 00:18:10,220 --> 00:18:16,359 Here you have examples of different animals that evolved and expanded during the Cenozoic, 158 00:18:16,359 --> 00:18:19,359 these animals are now extinct. 159 00:18:19,359 --> 00:18:24,799 Then, if we speak about geology and the continents, 160 00:18:24,799 --> 00:18:28,799 during the Cenozoic the continents moved to their current position 161 00:18:28,799 --> 00:18:31,799 and special things that happened was that 162 00:18:31,799 --> 00:18:35,799 Africa was moving north, so Africa collided with Europe 163 00:18:35,799 --> 00:18:39,799 and this created mountains. 164 00:18:39,799 --> 00:18:44,799 An episode of mountain building is called an orogeny. 165 00:18:44,799 --> 00:18:52,400 and the orogeny that happened when Africa and Europe collided is called the alpine orogeny 166 00:18:52,400 --> 00:18:58,799 because it was the origin of the Alps. But not only the Alps, also in the Iberian Peninsula 167 00:18:58,799 --> 00:19:06,000 we have the Pyrenees, the central system, so Guadarrama, etc. So these mountains have formed 168 00:19:06,000 --> 00:19:12,240 because of the collision between Europe and Africa. At the same time India, which had been 169 00:19:12,240 --> 00:19:19,119 separated from Asia until then. India collided with the rest of Asia, this happened around 45 170 00:19:19,119 --> 00:19:27,519 million years ago, and this gave place to the Himalayas. Then six million years ago 171 00:19:29,630 --> 00:19:36,269 is the beginning of what we call human evolution. So around six million years ago 172 00:19:36,269 --> 00:19:42,990 the last ancestor, the last common ancestor between chimpanzees and humans 173 00:19:42,990 --> 00:19:48,009 existed. Why do we call it the last common ancestor? Because all the 174 00:19:48,009 --> 00:19:53,190 ancestors of this ancestor have also been common ancestors between chimps and 175 00:19:53,190 --> 00:19:57,990 humans. This represents the last common ancestor between chimps and 176 00:19:57,990 --> 00:20:02,950 humans. From this point on, in evolution, some species, species after species after 177 00:20:02,950 --> 00:20:09,829 species gave place to chimpanzees, or species after species after species gave place to modern humans. 178 00:20:11,109 --> 00:20:19,109 So this branch of the evolutionary tree, this is the branch from the last common ancestor between 179 00:20:19,109 --> 00:20:27,109 chimpanzees and humans, and modern humans. So this branch has a lot of branches as well, different 180 00:20:27,109 --> 00:20:35,269 species that existed in the past that we will study in another another unit like Neanderthals 181 00:20:35,269 --> 00:20:45,190 or Australopithecus etc so these living things these species that lead to modern humans in 182 00:20:45,190 --> 00:20:53,990 evolution but do not lead to chimpanzees are called the hominins okay so the hominins are 183 00:20:53,990 --> 00:21:01,829 all the species in this part of the evolutionary tree all these species are extinct okay all 184 00:21:01,829 --> 00:21:11,029 hominins are extinct except one species which is our species homo sapiens okay by the way i repeat 185 00:21:12,150 --> 00:21:20,069 this group of species is called the hominins with an m perhaps some of you have heard the word 186 00:21:20,069 --> 00:21:29,109 hominid before but hominid is a bigger group of species okay the hominids is a group of primates 187 00:21:29,109 --> 00:21:35,430 okay a group of primates that is much bigger it includes the chimpanzees and these ancestors of 188 00:21:35,430 --> 00:21:41,910 chimpanzees it also includes the orangutans the gorillas and of course the humans okay 189 00:21:41,910 --> 00:21:49,349 so the hominids is not the same as hominins hominids is a very big group of species that 190 00:21:49,349 --> 00:21:55,190 includes some monkeys that exist now while hominins is a group of species that are all 191 00:21:55,190 --> 00:22:02,549 extinct except humans and it is specific of the evolution towards humans okay and finally we're 192 00:22:02,549 --> 00:22:09,589 about to finish another special thing of the sinusoic era is that in the last period of the 193 00:22:09,589 --> 00:22:19,269 sinusoic era which is called the quaternary period and is divided into epochs we have the current 194 00:22:19,269 --> 00:22:26,230 ice age. What is an ice age? From the point of view of glaciology an ice age is a time 195 00:22:26,230 --> 00:22:34,670 in which there are permanent ice caps on the poles. So now there is permanent ice on the 196 00:22:34,670 --> 00:22:39,930 north pole and on the south pole. So from the point of view of glaciology we live in 197 00:22:39,930 --> 00:22:45,750 an ice age. And during ice ages there are times that are extremely cold and they are 198 00:22:45,750 --> 00:22:53,829 called glaciations or also glacials and there are times in which there is permanent ice on the poles 199 00:22:53,829 --> 00:23:01,990 but they are not so cold so the ice caps are not so big then those periods that are not so cold 200 00:23:01,990 --> 00:23:10,869 are called interglacials okay so we now live in an ice age but we live in an interglacial of this ice 201 00:23:10,869 --> 00:23:14,869 So we live in an ice age but not during a glaciation. 202 00:23:14,869 --> 00:23:22,869 So this current ice age, this current cycle or succession of glaciations and interglacials 203 00:23:22,869 --> 00:23:27,869 started around 2.5 million years ago. 204 00:23:27,869 --> 00:23:35,869 So from the point of view of glaciology we live in an ice age which started 2.5 million years ago 205 00:23:35,869 --> 00:23:39,930 although we live in an interglacial of these ice age. 206 00:23:40,470 --> 00:23:41,589 Okay, and then with this, 207 00:23:41,769 --> 00:23:43,990 I have finished speaking about the Fannyrozoic union. 208 00:23:44,150 --> 00:23:45,049 Thank you for your attention.