Speciation and Extinction

Summary

Highlights

• Speciation is when one species evolves into two, driven by genetic change and environmental factors. 🧬
• Extinction reduces species to zero, often due to harsh environmental shifts or human impact. 🌐
• Adaptive radiation causes rapid species diversity in new ecological niches, as seen with Hawaiian honeycreepers. 🌺
• Mass extinctions are rare and catastrophic, with five major ones in Earth's history, eliminating vast species numbers. 🦖
• The Cretaceous-Tertiary extinction was likely caused by an asteroid impact, evidenced by global iridium layers. 🔍

Key Takeaways

• Speciation transforms one species into two due to evolutionary changes and environmental pressures. 🌱
• Extinction occurs when a species completely disappears, a process also influenced by environmental changes. 🌍
• Adaptive radiation leads to rapid species diversification when new ecological niches open up. 🌿
• Mass extinctions are rare events sometimes spurred by dramatic causes like asteroid impacts, as with the dinosaurs. ☄️
• Birds are considered the living descendants of certain dinosaur lineages, surviving past mass extinctions. 🦜

Overview

Chapters

• 00:00 - 00:30: Introduction to Speciation and Extinction In this chapter, the instructor introduces the topics of speciation and extinction. Speciation refers to the process of one species evolving into two distinct species, whereas extinction is the loss of an entire species. The discussion includes examples from paleontological discoveries, such as the analysis of Taposa surus, a saurischian dinosaur discovered in Brazil. The chapter serves as a foundational introduction to understanding how species differentiation and elimination occur in biological history.
• 00:30 - 01:00: Speciation and Phylogenetic Trees The chapter titled 'Speciation and Phylogenetic Trees' discusses the concept of phylogenetic trees as a way to trace the evolutionary lineage of species such as dinosaurs. Each branching point on the tree represents a common ancestor and demonstrates the process of speciation, where one species splits into two. The chapter also touches upon extinction, which is the opposite process where a species ceases to exist. Further discussion is anticipated on the mechanisms of speciation.
• 01:00 - 02:00: Speciation, Extinction, and Evolution The chapter explores the concepts of speciation, extinction, and evolution. It uses a timeline to illustrate how species have evolved over millions of years, starting from a common ancestor. It highlights the process of extinction, where some species completely disappear, while others evolve and diversify through speciation. This evolution and diversification lead to the rich biodiversity we observe today.
• 02:00 - 02:30: Adaptive Radiation and Mass Extinctions The chapter 'Adaptive Radiation and Mass Extinctions' focuses on two main concepts: speciation and extinction. It explains that species evolve or change within a gene pool, a process known as biological evolution. This process leads to the creation of new species, which occurs when one species becomes two through evolutionary change. The chapter also touches on the idea of survival, where some species survive at the expense of others, emphasizing the interplay between survival and extinction.
• 02:30 - 04:00: Stickelback Example of Speciation The chapter discusses the Stickleback as an example of speciation, focusing on how evolution and environmental changes can lead to speciation or extinction. Speciation is described as the formation of reproductively isolated populations, which contributes to biodiversity, whereas extinction reduces it. The dynamics between evolution, environment, speciation, and extinction are highlighted, with emphasis on the rapid rate of speciation in certain cases.
• 04:00 - 05:30: Dragonfly Larvae and Natural Selection The chapter discusses the concepts of speciation and adaptive radiation in the context of evolutionary biology. It highlights how new ecological niches can lead to adaptive radiation, while mass extinctions, of which there have been five significant events in Earth's history, can also pave the way for new species evolution. The example of the three-spine stickleback, particularly studied in Lerg Lake, Alaska, is used to illustrate speciation in action.
• 05:30 - 07:30: Adaptive Radiation in Hawaiian Islands and Extinction The chapter discusses speciation in the three spine stickleback fish, which is taking place in real-time in lakes near Wasilla. There are two phenotypes of stickleback: the low armored type typically found in freshwater environments, demonstrating ongoing adaptive radiation in these fish.
• 07:30 - 09:00: Famous Adaptive Radiations and Extinctions The chapter discusses the phenomenon of adaptive radiations and extinctions, using the example of the Marine stickleback fish that exhibits different physical adaptations based on its habitat. Marine sticklebacks have more armor, including larger and additional spikes, as well as plates on their sides, characterizing them as fully armored sticklebacks. In contrast, others are described as low armored. A natural experiment related to these adaptations was conducted in 1982 at Lerg Lake.
• 09:00 - 10:00: Overview of Mass Extinctions The chapter begins with a discussion on the stickleback fish population in Lerg Lake, noting that the majority were of the low armored freshwater variety. In 1982, a significant event occurred -- the lake was poisoned to eliminate the sticklebacks, despite their ecological purpose, in favor of introducing trout and salmon to promote their growth. This led to the eradication of the stickleback population in the lake, setting the stage for further exploration of the chapter's themes.
• 10:00 - 11:00: The Great Dying Extinction Event The chapter titled 'The Great Dying Extinction Event' describes an experiment involving sticklebacks in a lake. Initially, the lake had no sticklebacks, but over time, fully armored sticklebacks began to populate it. These fish likely traveled through streams from the ocean back into the lake. As their numbers increased, the presence of fully armored sticklebacks in the lake became noticeable, leading to further puzzling observations over subsequent years.
• 11:00 - 12:30: Cretaceous-Tertiary (KT) Extinction Event The transcript discusses a natural experiment illustrating speciation and evolutionary change in sticklebacks. Initially, fully armored sticklebacks were prevalent, but over time, their numbers began to decline while the population of low armored sticklebacks increased. This shift in population dynamics, which can be observed by visiting a place called Lowber, demonstrates the process of speciation. The narrator reflects on this evolutionary trend, pondering why less armor might be advantageous when more armor seems beneficial. This example showcases a real-time evolutionary change in a species.
• 12:30 - 13:00: Conclusion The chapter titled 'Conclusion' discusses a dangerous predator for small creatures: the dragonfly larvae. Dragonflies, known for their beauty, spend a significant part of their life underwater as nymphs or larvae. This chapter likely includes a description of a scene from a David Attenborough movie where the dragonfly larvae is depicted hunting, showcasing its predatory nature.

Speciation and Extinction Transcription

• 00:00 - 00:30 hi it's Mr Anderson and welcome to biology Essentials video number s007 uh this video is on speciation and Extinction um and so it's really on just two things in other words it's how we go from one species to two and then how we go from one species to no species and so this right here is a taposa surus uh it's a sorod that was found in Brazil and you can see it right here this
• 00:30 - 01:00 philogenetic tree and so if we trace the philogyny of tapu asaurus what we would find is each of these points here represents a common ancestor of the dinosaurs above it but because it branches in either direction that means we're going from one species into two species and that's called speciation and we'll talk a little bit more about the mechanisms by which we can speciate uh but essentially in speciation you go from one species to two um an Extinction is when you go from one species to zero
• 01:00 - 01:30 species and so where do we find on that on here well on the side you can see we have time so we have time on the side so this is millions of years ago and so you see that some of these will end in other words um nitrosa right here ends and that means that it went extinct in other words this one species became zero species and so in life we go from that first common ancestor of all life but we've gotten a diversity of life through speciation but remember all also along
• 01:30 - 02:00 with that we have a lot of extinctions in other words the survivors uh are surviving on the on the backs of those that that don't survive and so this video is really only about two things but it'll be a little more in detail than that and so how do we get um new species that's through a process called Evolution or uh it's biological evolution or change within a gene pool so there are two things kind of in play with speciation and Extinction in other words when one species becomes two that species is evolving or changing or
• 02:00 - 02:30 separating into two populations that are reproductively isolated um and so Evolution can give us diversity but as that environment changes it can force speciation and that environment can also Force Extinction and so there's this play between evolution environment and then speciation and and Extinction this remember creates more diversity and this actually creates less so taken to these extremes one specific type of speciation where you see incredible a rapid uh rate
• 02:30 - 03:00 of of speciation is called adaptive radiation that usually opens happens when we open up a new Niche and uh likewise when you have a bunch of extinctions at one time we call that mass extinction and we've only had about five of those um through the history of Life on our planet so let's start with speciation and let me give you a real example of that and this is the three spin stickle bag uh three spine stickle back and the study I'm looking at here was in lerg Lake which uh to kind of Orient yourself here's Anchorage right here here so we're in Alaska um lerg
• 03:00 - 03:30 lake is right down the road from Wasilla uh and so uh speciation occurred in uh the stickleback or is occurring right now in the stickleback uh the three spine stickleback has three spines that go out the back but there are actually two different phenotypes or two different varieties of stickleback this would be a low armored stickleback and it's found usually in a freshwater environment but if we were to look at the stickleback uh
• 03:30 - 04:00 the Marine stickleback that spends half of its life in the ocean and then comes back to actually breed it'll have more armor on it so it'll actually have larger spikes it'll have additional spikes down here and then they have plates on the side so there are plates on the side of the stickle back that go all the way back here and so this would be what we call a fully armored stickle back and then if I get rid of the coloring that'd be a low armored stickle bag okay so a natural experiment was done in 1982 so 1982 in lerg Lake we'll
• 04:00 - 04:30 say lerg Lake looks like this almost all the sticklebacks in lerg Lake were of the uh low armored Variety in other words they were just this fresh waterer and so what happened in um 1982 is that they poison the lake cuz sticklebacks don't really have a purpose uh they do but they wanted to put uh trout and salmon back into the lake and they wanted them to grow and so they poisoned everything in the lake so they killed all the the sticklebacks um so there
• 04:30 - 05:00 were no sticklebacks in the lake so it's a great kind of an experiment um what they found is that over the next few years fully armored sticklebacks were making their way into the lake and so they were making their way probably through streams and and out from the ocean and making their way back into the lake and so what we had in here was fully armored sticklebacks and over the next few years their population started to grow eventually they started to notice hey there's fully armored sticklebacks in here and so what they found then over the next few years is is puzzling
• 05:00 - 05:30 in other words the fully armored sticklebacks started to drop off their numbers started to drop off and then they started to see an increase in the low armored stickleback in other words their population started to increase to the point where if you go to lowber like right now you're going to find almost all of the low armored sticklebacks and not many of the fully armored and so this is a kind of a cool experiment where you can actually see speciation taking place now why would you see that if you think about it for me I would think man more armor the better why wouldn't I want as much armor as I can
• 05:30 - 06:00 but the Predator that they were facing was um one of the most scary predators in all of science if if you were small so this right here is a dragonfly larvae and so dragonflies remember are very beautiful but they spent a lot of their life underwater and they form it as a nymph or or a dragonfly nymph and so or or larvae and so this is one hunting this is a video from David aten burough movie so let's watch him feed
• 06:00 - 06:30 wow okay that's a little disturbing and so the uh dragonfly larvae is the U major predator in lurg Lake and so the low armored sticklebacks actually grow faster than the fully armored sticklebacks and so the fully armored sticklebacks were being prayed upon at a greater rate by the dragonfly larvae than the low armored sticklebacks and so we had natural selection taking place and so what we're starting to see is a
• 06:30 - 07:00 change in that now eventually if fully armored and low armored sticklebacks can't interbreed then we have those uh as a separate species and so on that tree of life we can go from one branch to two now again taking to its extreme we can have what's called adaptive radiation and so once you have a new environment where species can take off and there's no Predators you get a huge amount of diversity and so when we talk about Evolution we have a tendency to fixate on the galpagos islands and and neglect the Hawaiian islands and so this
• 07:00 - 07:30 is a great picture right here of the Hawaiian Islands um but what we found is that it was hard for a lot of species to get to the islands mammals weren't going to make it but birds could make it easily and so the honey creeper is an example of a bird that just went crazy on the on the Hawaiian islands and so we think the ancestor of modern day honey creepers was a bird that looked like this it was somewhat similar to a finch but once it arrived on the island it was a founding population you got this huge diversity of all these honey creepers
• 07:30 - 08:00 you can see their beaks are each of them adapted probably to a different flower and so we had adaptive radiation so we had this new Niche show up this new environment and they exploited or excuse me we had this new environment show up and they all exploited all these different niches um and so you had this great diversity of of of Honey creepers now a lot of these are pictures and not actual photographs and the reason why is that humans showed up and with humans then we had predators that showed up and they started to uh make a lot of species go away and so Extinction started to
• 08:00 - 08:30 show up as well what's another famous adaptive radiation well I can think of a couple um one would be uh the arrival of um mammals and so once the dinosaurs went extinct and mammals were able to grab a foothold they adaptively radiated to fill a bunch of different uh niches that were once filled by dinosaurs or adaptive radiation we could also see in the galopagos as they move from Island um to Island like the beak of the finch uh which was just one population on the galpagos now this side of this podcast
• 08:30 - 09:00 is the idea of Extinction and I love this quote right here it's the idea that 99.9% of all species that have ever existed are now extinct and so these are some species the Aro the quagga the great o the thyine or the Tasmanian wolf these are all species that have gone extinct uh just in the last few hundred years um and and they did that as a result a lot of these as a result of human pressure this would be a golden toad uh that went extinct in the 1980s and so if we look on this tree of life each of these Branch points here would
• 09:00 - 09:30 be an area of uh speciation but each of these end points would be an area of Extinction in other words that that once you have that last organism die of that species um then you can't pass that on those genes on anymore and so we would say it's extinct now the things that are alive today are called extin but if we look through the history of life we find sometimes that there are massive extinctions extinctions that go across all all right scientists have identified five different mass extinctions uh over
• 09:30 - 10:00 time and they're labeled here with these yellow triangles this would be the ovian Saran Extinction this would be the late devonian um this is the perian Triassic Extinction this would be the Triassic Jurassic Extinction and then this right here would be the Cretaceous tertiary Extinction and so what makes a mass extinction it's a it's an Extinction where the the the the rate of Extinction is just dramatic um and so we also have other Extinction events here within this um this one a couple of of interesting
• 10:00 - 10:30 ones that you maybe know about this right here would be the peran Triassic Extinction this one is known as the um great dying and so of all the extinctions this is the biggest one um during the Great dying something like 70% of all land species and 96% of all marine species uh when extinct um and there are a number of different causes of that probably the one Extinction that almost everybody's familiar with is the KT or Cretaceous Triassic Extinction uh or tertiary Extinction and so that's the
• 10:30 - 11:00 the one where the dinosaurs actually went away and so with all of these extinctions scientists are trying to piece together what actually causes it and so a lot of these are um suspects in other words the great dying formed at the same time when Pangia actually formed and so a scientists think that that had something to do with it but it could have also been volcanoes it could have also been oceans losing their oxygen and so these are all the different types of characteristics that could have led to mass extinction and so
• 11:00 - 11:30 scientists are kind of piecing those together and figuring out which one of those um caused each of these different extinctions the one that uh I want to talk more about specifically is the KT KT Extinction or the Cretaceous tertiary Extinction um and the evidence there is pretty good this is where dinosaurs go away um it's probably not super super accurate to say that there's a lineage of dinosaurs that continues today and those are called Birds um and so birds of it's a it's a lineage
• 11:30 - 12:00 of dinosaurs that continue today but most of the dinosaurs actually disappear at that time and so the point in the fossil record where they disappear is sometimes referred to as the Cretaceous or the KT boundary um and and if we look below that we find dinosaurs and if we live look above that we find no dinosaurs um in the fossil record now you've probably learned that there was a giant asteroid that hit around that time and we think that that it hit in the
• 12:00 - 12:30 Gulf of Mexico we've actually isolated where that um that crater is but what evidence would we have to show that this actually exists why isn't it something else like climate change for example well one piece of evidence is that down here we have uh dinosaurs above here we have no dinosaurs but we also have a level of idium that goes around the planet so a thin layer of aridium that's found along this KT boundary idium is really rare on our planet it's not very
• 12:30 - 13:00 common but in asteroids it's incredibly common and so that's one piece of evidence that suggests that um this asteroid impack could have led to the uh uh The Disappearance of the dinosaurs and so that's an Extinction and so again to to summarize we've got speciation where we make new species extinctions where we uh get rid of those um and they're big at sometimes and their rates are really uh high at sometimes and really low at other times and mostly that has to do with changes in the environment um and so I hope that's helpful