Phylogenetics

Summary

Highlights

• Discover how phylogenetics maps out the evolutionary family tree of life! 🌳
• Learn about the transition of heart structures from fish to mammals. 🦈🦒
• Find out how cladograms illustrate species' shared traits and evolutionary paths. 🗺️
• Explore how DNA evidence reshapes our understanding of species connections. 🧬
• Embrace the dynamic world of phylogenetics—a hot topic in modern biology! 🔥

Key Takeaways

• Phylogenetics creates evolutionary trees showing relationships between organisms! 🌿
• Morphological and molecular data are essential in tracing lineage and evolutionary patterns. 🧬
• Hearts have evolved uniquely across different species from aquatic to terrestrial animals. ❤️🐟
• Cladograms help in identifying and understanding evolutionary relationships of different organisms. 🌳
• The field of phylogenetics is dynamic, constantly shaped by new molecular evidence. 🔍

Overview

Chapters

• 00:00 - 00:30: Introduction to Phylogenetics This chapter introduces the concept of phylogenetics, focusing on the evolutionary history and family tree of organisms. Phylogenetics, also known as phenetics, involves constructing phylogenetic trees, which illustrate the relationships and relatedness among different species. The provided example in the chapter includes images of whales, emphasizing the goal of creating a tree that maps out their evolutionary connections.
• 00:30 - 01:00: Whale Phylogenetic Relationships The chapter discusses the phylogenetic relationships of humpback whales with other whale species such as gray whales, minke whales, and fin whales. Emphasis is placed on the role of DNA evidence in constructing these relationships and the goal of aligning phylogeny with taxonomy, enabling names to be assigned based on genetic relationships. It highlights the complexity and interconnectedness of life forms.
• 01:00 - 01:30: Speciation and Phylogenetic Trees The chapter titled 'Speciation and Phylogenetic Trees' discusses the concept of speciation, which is the process by which a single organism, population, or group diverges to the point where they can no longer interbreed. It introduces phenetics and phylogenetic trees, which require speciation to occur. A type of phenetics tree mentioned is the cladogram, which utilizes clades.
• 01:30 - 03:00: Morphological Evidence: Heart Evolution The chapter delves into the evolutionary history of the heart, examining it through both morphological and molecular lenses. Focus is given to how the structure and complexities of hearts have evolved over time in response to various needs. It also briefly touches upon using DNA (molecular evidence) for understanding evolutionary changes.
• 03:00 - 04:00: The Phylogenetic Tree of Life The chapter titled 'The Phylogenetic Tree of Life' introduces phylogenetic trees and their role in understanding the relationships between different species. The discussion includes the examination of evidence used to determine these relationships. The chapter concludes with a focus on cladograms, including insights into how they are created. It starts from the broadest phylogenetic perspective by exploring the tree of life, which traces all life back to a common origin about 3.6 billion years ago, illustrating the evolutionary diversification into various lineages.
• 04:00 - 05:00: Morphological and Molecular Evidence This chapter discusses the concept of the phylogenetic tree of life, highlighting the idea of common descent as first proposed by Darwin. It emphasizes that bacteria, archaea, and eukarya share a common ancestor, which is depicted by their placement on the phylogenetic tree. Each branch point in this tree represents a divergence where a common lineage separated into distinct groups, such as eukarya and other lineages.
• 05:00 - 07:00: Molecular Data in Phylogenetics The chapter 'Molecular Data in Phylogenetics' discusses the concept of descent and the evidence supporting Darwin's theories. It introduces the idea of determining relationships among species using phylogenetic trees, starting with morphological evidence, which refers to the structures present in organisms. The chapter provides an example involving a phylogenetic tree of vertebrates, tracing the lineage from early vertebrates.
• 07:00 - 10:00: Cladograms and Clades This chapter explores the concept of cladograms and clades in understanding the evolutionary relationships among different organisms. It particularly focuses on mammals and their relations with birds, reptiles, amphibians, and fishes. Scientists determine these relationships by picking a specific characteristic, such as the heart, and tracing its development over time. For instance, the evolution of the heart is traced from its two-chambered beginning in fishes.
• 10:00 - 13:00: Characteristics and Cladistics In this chapter, the discussion revolves around the differences between closed and open circulatory systems, taking examples from various organisms such as insects and fish. It highlights how blood flows through a closed circulatory system, using valves to ensure one-way movement, and details the heart's function in this system. The chapter contrasts this with the open system in insects where blood circulates freely through the tissues.
• 13:00 - 15:00: Purpose and Goal of Cladograms The chapter discusses the purpose and goal of cladograms, focusing on the evolutionary biological context. It explains the function of the two-chambered heart, primarily in fish, which involves a single loop system where blood is oxygenated through the gills and circulates through the body before returning to the heart. This system is suitable for aquatic life but presents challenges when organisms transition to terrestrial environments, prompting evolution and adaptation.

Phylogenetics Transcription

• 00:00 - 00:30 [Music] hi it's Mr Anderson and welcome to biology Essentials video number six this is on phenetics and phenetics is essentially The evolutionary history or The evolutionary family tree of organisms um if you look on this page we've got a number of pictures we've got a number of pictures of saaan so a bunch of whales um so the goal of phenetics is to create a philogenetic tree in other words a tree that shows who's related to
• 00:30 - 01:00 who in other words is the humpback whale most related to the gry whale or to the minky whale or to the fin whale and so phenetics is actually a really fascinating area right now because with all the DNA DNA evidence that we have we're able to put together a wonderful picture and and our goal is that the philogyny will match tonomy in other words we can give names to organisms based on who they're related to um but the more you learn about this the more you realize that all life is very very
• 01:00 - 01:30 similar we have similarities between all of it so let's get going on uh phenetics and so basically speciation is when one organism or one population or one group uh eventually diverges and so they can't interbreed anymore it's the simplest way to think about speciation and so phenetics and philogenetic trees require speciation to have occurred um there are a number of different phenetics trees uh the one that we'll talk a lot about are called cladograms and they use what are called clades um and so it's just a
• 01:30 - 02:00 specific type but a philogenetic tree shows The evolutionary history of an organism now how do we figure that out well we we could use all the tools at our disposal um I'm going to talk about two specifically today one is morphological morphological is the structure that you have and the other is molecular and so morphologically I'm going to talk about hearts and how Hearts have changed over time as they've required more and more things and then the last is molecular uh in other words how do we use DNA to figure who figure
• 02:00 - 02:30 out who's related to whom so those are philogenetic trees this is the evidence that we use to figure it out and then at the end I'm going to talk more about uh cladograms and and how you create a cladogram and so um let's start with the biggest philogenetic tree of all philogenetic tree of life so if this is life down here so if life began you know 3.6 billion years ago it's diverged into all these different lineages and so this right here would be a philogenetic tree
• 02:30 - 03:00 philogenetic tree of life now the one thing I want to point out and Darwin was the first person to do this is that whenever you have a tree that suggests that there's common descent and what does that mean well bacteria archa and ukaria since they're all on the same philogenetic tree it means that they all came from that common ancestor and so every time we have a branch point on here so what does this suggest that Branch point right there suggests where that tree diverged into the ukaria and then the ARA that we we have and so the
• 03:00 - 03:30 idea of of descent is is a long one but the more evidence that we gather the more we realize that that Darwin was right on um now we have to figure out who's related to to who and so let's start at at evidence that we have so the evidence that we can use to make a philogenetic tree let's start with the first one is is morphological morphological are the structures that you uh that you have and so this is a philogenetic tree of vertebrates and so we've got early vertebrates we've got
• 03:30 - 04:00 time periods over on the side but we're most interested uh in the mammals we got birds reptiles amphibians fishes and so how did scientists figure out who's related to who well uh we can we can choose one characteristic and then we can Chas we can trace that through time we can look at one thing and see how it's how it's changed over time so a perfect example would be the heart um the heart began in uh fishes as a two chambered heart um a two chambered heart
• 04:00 - 04:30 uh really just has one valve in other words the blood is going to flow in this direction and then there's a valve that opens in this direction so once the blood moves through it it can't come back in and so it's just a muscle that has a valve on the inside of it and so what's the function of the heart well in a closed circulatory system in other words insects don't use a closed circulatory system they use their blood just goes everywhere in through the tissues but in a closed circulatory system in a fish the blood which in blue in this case just means that it's de oxygenated is going to go through the
• 04:30 - 05:00 gills and then it's going to be oxygenated so it's red and then it's going to go through the body and the tissues in the body and then it's going to drop off that oxygen and then it comes back to the heart again and so a two-chambered heart a better way to think about what a two-chambered heart is is it simply a single Loop so we just have this one Loop through the gills and back to the body and for fishes that works great uh the problem is that as we move on to land there are quite a few more uh constraints As you move
• 05:00 - 05:30 especially as you move towards being like a warm-blooded organism and so the constraints get heavier and heavier and so uh it's okay to have a two-chambered heart works great if you're a fish but as we move on to land then it has to modify itself and so again we just have this one Loop the major problem is that once it goes through the gills you lose a lot of the pressure and so you lose the pressure and so it's hard to move that through the rest of your body it works great if you're floating in water but as you move on to land uh we don't have that pressure okay so let's go to a
• 05:30 - 06:00 three-chambered heart now a three-chamber heart arrives in the amphibians and so uh things like a a frog have a three-chambered heart so they've got three delineations we've still got um that Loop that goes through uh the the lungs and mostly in amphibians that actually goes through the skin where they pick up oxygen but you see that we now have a problem here we're we're not losing that pressure in other words we're able to pump the blood to the the skin and the lung or excuse me we're able to pump it um to this to the skin and the lungs and then we have
• 06:00 - 06:30 a separate Loop that goes through the body so we still don't have we don't have to deal with that pressure but the problem comes in right here uh and that is that we have a mixing of the oxygenated and deoxygenated blood and so it's purple now is that a problem well it's a problem if you are anything uh above or spend more time on land than amphibians do and so it works great for amphibians but you have a mixing of oxygenated and deoxygenated blood and so if you look at this loop it's a double Loop but if you look at it and say okay
• 06:30 - 07:00 now let's move up to the reptiles and now we have to move more blood and we don't want as much of this mixing here because we're going to lose a lot of that oxygen well think about it as an engineer how could you solve this well a three chambered heart works like this and what it does is it has a Septa that's built right down here in the middle of the heart and that SEPTA separates the deoxygenated from the oxygenated it still has a little bit of mixing of the blood but that works great because they're cold blooded Critters
• 07:00 - 07:30 and so as they move that body that blood around their body they can actually keep themselves a little bit warmer um but that's a three-chambered heart and as we move on to endothermy as we move on to birds and mammals that just doesn't cut it and so um we think that birds and mammals both evolve this independently and you can see on here that that birds branched off from reptiles and mammals branched off earlier from a from a common ancestor and so we eventually have the arrival of the the four
• 07:30 - 08:00 chambered heart what's the four chambered heart do well you can see that that SEPTA that went right down the middle has completely closed off so we don't have any mixing of the oxygenated and deoxygenated blood and so birds and mammals have this morphological um change uh and they they did it because they're endothermic in other words they require um a constant body temperature and so we can trace this morphological evidence through the uh organisms we can say who's related to whom in other words if we have a
• 08:00 - 08:30 three-chambered heart that's shared by everything above here that means that on our philogenetic tree we want to at least put those on the same Branch next I want to talk about uh molecular data so molecular data is looking at the um DNA so looking at the genetic code and so this is u a study that was done in 2009 and what they were trying to figure out is where metazoans fit and who's related to whom and every time I have a new Biology book I find that this is actually organized a little bit differently but we have this group down
• 08:30 - 09:00 here of the uh so the jellyfish and the sponges down here on the bottom and then we have this group up here which contains uh things like us and so scientists weren't sure if this branched off early or if these branched separately and so what they did is they gathered a huge amount of DNA evidence and so you can see here that this was a a very large study done on a number of different families a number of different groups of animals and they looked at um mitochondrial DNA proteins ribosomal RNA
• 09:00 - 09:30 they looked at a number of different things and they figured out just as very recent that this branch and this Branch are actually uh sister branches the branch up here that makes us and the branch that makes the jellyfish have kind of separated a long time ago and they've been evolving since then and so this is a great way this would be a philogenetic tree that we can use molecular evidence to answer a problem um but you have to gather a huge amount of data before you can actually do that and on here you can see that they actually have an outgroup which is a group group of fungi which is not an
• 09:30 - 10:00 animal but it's a it's a way that we can actually make comparisons to that molecularly and then we can uh figure out the connections okay last thing I said i' talk about are cladograms cladogram uses what is called a clade and a clade if I remember right comes from it's I think Latin it means the branch and so a CLA is simply a group that has an organism and all and I would circle the word all of its descendants and so this right here is a clay because it has this organism and all the all the
• 10:00 - 10:30 descendants that come from that or this the Orange is going to be a clay because it has this organism and it has all of The Descendants that come from that but green right here we would not call this a clay and the reason why is that you would have this organism right here and all these descendants but you're missing a number of them over here and so that's not a a true CLA and so cladograms are going to um it's it's the definitive answer of who's related to whom but you use uh two things you use um molecular
• 10:30 - 11:00 in DNA for sure evidence but the other thing that you're going to use are something called synapomorphies and a synapomorphy is going to be a characteristic is it's shared by all of those in the clay um so a couple of good ones as we look through the fossil evidence of of dinosaurs um we Branch all dinosaurs into two groups the orysia and the cicia and these are all uh cicia if I remember right means bone bird hipped and orysia means uh lizard hipped uh and so it's a way to Branch these
• 11:00 - 11:30 groups and so a synapomorphy would be this characteristic in other words cishan is going to be in this hip structure is going to be shared by everything in this CLA and so the goal is to have a clay that has similar characteristics and it also doesn't leave anything out um a real example that you're probably familiar with would be reptiles um reptiles is a s silly term because reptiles used to be this blue area right here um it contained things like uh turtles it came
• 11:30 - 12:00 crocodiles and and B and and birds we left out of that and so if you look at this this group is what's called paraphyletic and so reptiles as a group was paraphyletic it had all of these descendants but it lacked the birds and we now know that birds are part of this group and so the goal of a cladogram is to create what are called monoptic groups monoptic would be this um yikes would be this yellow group right here
• 12:00 - 12:30 because it contains this and all of the descendants of that that move from here so uh polyphilic means you have groups that come from different areas so if we were to put mammals and birds together in one group that'd be uh polyphilic and paraphilic is when you have some organisms but not others and so what's the goal the GL goal of a cladogram is to figure out all of life so we put all of life on on branches and we figure out who Rel relateded to whom and then uh
• 12:30 - 13:00 hopefully we can use a naming system and and classify all of life it seemed like a daunting task at one time but molecular evidence is giving us an inroads to that and it's a really uh Hot Topic as far as biology goes today so that's phog gentics and I hope that's helpful