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Evolution BI30-LE2 Examine the significance of evolution as a key unifying theme in biology through the principles processes and patterns of biological evolution. Evolution – what is it? • Key Principles • Common misconceptions • OpenStax Ch. 18-1 as a guiding tool or use your devices to pursue the following information. Key Principles and Processes of Evolution • Descent with Modification • Fitness as a result of adaptation and struggle for existence. • Natural selection (need variation – genetic diversity) • Genetic drift • Selective breeding • Divergent/Convergent evolution. Descent with modification • Over time and generations the traits providing reproductive advantage become more common within the population. • Our descendants become modified or changed. • Example: if being hairy kept you warm in a constantly cold environment, you’d be more likely to reproduce and pass on this modification to your descendants in the population. “Fitness” • Result of adaptation and the struggle for existence. • Adaptation – a heritable trait that helps the survival of an organism in its present environment. • Fitness does not necessarily mean strength – it could be smarts, camouflage, or other traits that allow an organism to survive. Natural selection • the process whereby organisms better adapted to their environment tend to survive and produce more offspring. • Nature selects “for” or “against” a particular trait. • Hair analogy in a cold environment – hair would be selected for. No hair would be selected against. Genetic drift • variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce. • Do we remember/know what a genotype is? This can lead to the disappearance of a particular genotype/allele. Selective breeding • Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics). They do this by choosing a specific animal or plant males and females to sexually reproduce and have offspring together. • This is how GMOs are everywhere. Divergent/Convergent Evolution • Divergent evolution – when two species evolve in diverse directions from a common point. Can be observed in cladistics. • Convergent evolution – two similar traits may evolve despite a nonsimilar ancestry. Evolution Importance • Ultimately, all of these different aspects of evolution help us establish potentials links and ancestry between species. • But what’s the point of that? Why bother? What benefits could be gained? • From studying organisms evolution, we try to classify them into similar groups based on certain characteristics – these groups (getting more specific) are called Kingdom, Phylum, Class, Order, Family, Genus, Species. Divergent – Classifying - Cladistics A particular system of phylogenetic (genetics and traits) classification is called cladistics. Cladistics uses shared derived characters to establish evolutionary relationships. Cladistics A shared derived character is a feature that apparently evolved only within the group under consideration. Creation of a Cladogram Make your own! • Create a Cladogram Assignment • Complete the front page – making a tree from the chart given. • Create your own chart and tree on the back page. Select six organisms and five traits that will separate them from one another. • Which organisms are most closely related, which are least closely related? Why are cladograms important? • When looking at creatures through the scope of divergent/convergent evolution… we can begin to see organismal ancestry and how organisms relate to one another and when certain shared derived characteristics came into existence. • Different types of evidence that scientists gather helps us create cladograms and can separate some domains/species from one another and paint a picture as to the origins of life and a Last Universal Common Ancestor (LUCA). Human Evolution • https://en.wikipedia.org/wiki/Human_evolution • Family ______________ = adaptation that sets it apart is bipedalism • Homo _______ (skillful human) – 2.8 million years ago. A mutation occurred in which the SRGAP2 gene doubled – a gene responsible for the wiring of our frontal cortex (large part of learning)… so they started becoming bigger (more processing power = smarter = evolutionary advantage) • Homo _______ (upright man)– using fire and tools 1.3 million years ago. • Homo _______ (wise human) eventually evolved form a branch of this and began replacing branches of this around the world _______-________~ years ago. Over that time gradual changes in behaviour occurred coinciding with subtle changes to societies and some changes to our species as a whole. Human Evolution • https://en.wikipedia.org/wiki/Human_evolution • Family: Hominidae/hominini = adaptation that sets it apart is bipedalism • Homo habilis (skillful human) – 2.8 million years ago. A mutation occurred in which the SRGAP2 gene doubled – a gene responsible for the wiring of our frontal cortex (large part of learning)… so they started becoming bigger (more processing power = smarter = evolutionary advantage) • Homo erectus (upright human) – using fire and tools - 1.3 million years ago. • Homo sapiens (wise human) eventually evolved form a branch of this and began replacing branches of this around the world 250,000-400,000~ years ago. • Over that time gradual changes in behaviour occurred coinciding with subtle changes to societies and some changes to our species as a whole. Human Evolution Theory • _____ ___ _________ Hypothesis – small group of Homo sapiens evolved out of Africa. _______________ ____– mitochondrial DNA is passed from mother to offspring without recombination (apart from mutations stays the same). Human Evolution Theory • Out of Africa Hypothesis – small group of Homo sapiens evolved out of Africa. “Mitochondrial Eve” – mitochondrial DNA is passed from mother to offspring without recombination (apart from mutations stays the same). Evidence for evolution • Fossils • Anatomy and embryology – homologous analogous structures. • Biogeography • Molecular biology Fossils • Fossil record often provides clues to evolutionary relationships. • The fossil record may provide the framework of a phylogenetic tree, but a systematic taxonomist would seek to confirm the information it provided with other lines of evidence. • As we find fossils – we can infer when that organism existed and compare its structure to that of other fossils or existing organisms. Anatomy (Morphology) and Embryology • Some organisms upon comparison have homologous and analogous structures. • What do these terms mean? • Some organism follow similar embryological processes. Anatomy - Homologous • Homologous features, features that have similar structure and come from similar embryonic layers but have completely different functions Anatomy - Analogous • Analogous features are ones that come from different embryological development but look similar and perform similar functions, like the wings of bats and the wings of insects. • Which one (analogous or homologous) connects to divergent evolution, which one to convergent? Embryology • Early patterns in embryological development provide evidence of phylogenetic relationships • They also provide a means of testing hypotheses about relationships that have been developed from other lines of evidence. • Seeing similarities in embryological development helps us make inferences about ancestry. Embryology • The fertilized egg is known as a zygote which undergoes several cell divisions to become a hollow ball of cells called a blastula • A small indent on the blastula develops, this is the blastopore. • The order in which organisms develop in early stages of life is a big part of classification. • Look up phyla of organisms (just a list) – which one do you think we’re most closely related to and why? Embryology • The blastopore will develop into an opening of the digestive tract. • In echinoderms and chordates the blastopore becomes the anus. • In all other animals the blastopore becomes the mouth. This leads to the conclusion that vertebrates and echinoderms are more closely related. Biogeography • Locations of plants and animals. Similar locations similar adaptations required similar organisms. • Pangaea – marine fossils at the top of the Rockies (old glaciers). Molecular biology • Certain organisms share common proteins, amino acids and segments of DNA… observing similarities between these in organisms help us define how closely related they are. Chromosomes & Macromolecules • Taxonomists use comparisons of macromolecules such as DNA, RNA, and proteins as a kind of “molecular clock” • Scientists compare amino acid sequences for homologous protein molecules of different species. • The number of differences is a clue to how long ago two species diverged from a shared evolutionary ancestor. Common Misconceptions of Evolution (Ch 18.1 will help!) With a partner, discuss why these are wrong. You have ten minutes. • Individuals evolve. • Natural selection is evolution. • Evolution is random. • Evolution is just a theory. • Evolution explains the origins of life. • Organisms evolve on purpose. Selective Pressures Selective Pressures are OR Types of Pressures • • • • • Selective Pressures Selective Pressures are any phenomena which alters the behavior and fitness of living organisms within a given environment.(1) OR Anything that can impact the life of organisms. Puts “pressure” on organisms and will cause selection to take place. Types of Pressures • Competition • Predation • Changes in climate • Parasitism • Pollution Example of Selective Pressure • Create an example of each selective pressure on a particular species and what trait may help one get past this versus others in the species. • • • • • Competition – Predator – Change in climate – Parasitism – Pollution – Example of Selective Pressure • Create an example of each selective pressure on a particular species and what trait may help one get past this versus others in the species. • Competition – Two tigers, fightin’ over bread, stronger one lives and eats and then can reproduce! • Predator – Eagles are attacking rodents, porcupines who have sharper spikes live – eagles don’t like sharp spikes. • Change in climate – drought – Gazelle with better internal compass live. • Parasitism – caterpillar with thicker skin – wasp can’t inject parasitic larvae • Pollution – mammal with hairier nostrils filters out air pollutants on the way in. Example of Selective Pressure • In a cold climate, animals need certain characteristics to survive, like a warm furry coat, the ability to make burrows to live in and the ability to collect and store food for the winter. The selective pressure of cold weather means that animals that don't have these characteristics and are less likely to survive and reproduce. In a hot, dry climate, plants will have an advantage if they have phenotypes such as the ability to store water, large root systems to absorb what little water is in the soil, and perhaps ways to prevent water loss even at high temperatures. Source: Study.com Speciation • What is it? • What does it involve? • Why is it important? Speciation Dispersal – organisms “disperse” to new locations Vicariance - organisms are separated “river divides the group” • Involves the formation of new and distinct species in the course of evolution. Two types: Allopatric (geographic separation of parents and the creation of new species – dispersal and vicariance) and sympatric (parent species is in same location but changes within population eventually lead to new separate species – ploidy {problems in cell division}) Species – organisms able to mate with their own and have viable, fertile offspring. • It includes natural selection and isolation (reproductive barriers). • It is important because these differences and changes give rise to new species and maintain the differences between others. Visual for Sympatric vs Allopatric Speciation Isolation/Barriers to Reproduction Isolation leads to ____________. Two types of reproductive barriers prezygotic and postzygotic. Prezygotic – Postzygotic – • Different barriers. Behavioural Temporal Geographic Isolation/Barriers to Reproduction Isolation leads to Speciation. Isolation means “reproductive isolation of the species” – what makes that species mate with itself and only itself... There are barriers to reproduction that help this occur. • Two types of reproductive barriers prezygotic and postzygotic. Prezygotic - are those that prevent mating between different species. (Gametic barriers/structural barriers). Postzygotic - are those that reduce the likelihood that an offspring will survive after mating has occurred, but before the offspring is actually born (can also include sterile offspring) Behavioural Isolation • What is it? • What does it involve? • Example: Behavioural Isolation • Evolutionary mechanism of identifying members of same species as proper mates. • It involves a reproductive barrier based on behavior, usually in the form of mating rituals and signals. Signals that attract mates to each other may be one of the most important factors in determining whether closely related species mate with each other or not. • Fireflies – males flash a particular light pattern. Females only recognize that of the same species. Temporal Isolation • What is it? • What does it involve? • Example: Temporal Isolation • Evolutionary mechanism that prevents species from mating because they breed at different times. These differences can be time of day, season, or even different years. • It involves organisms that only mate at certain times – if the times don’t sync up – no mating! • Example – two similar species of frogs, but they mate at different times of the year. Geographic/Habitat Isolation • What is it? • What does it involve? • Example: Geographic/Habitat Isolation • Evolutionary mechanism that refers to a population of animals, plants, or other organisms that are separated from exchanging genetic material with other organisms of the same species. • It involves the physical separation of the species – once isolated they begin to evolve independently. • Example – black cats and white cats are separated by a new river that formed after a flood. No more mixes… Evolution over Generations • Gradualism versus punctuated equilibrium • Divergent/convergent evolution • Coevolution • Adaptive radiation • Mass extinction • Evolutionary arms race Gradualism • Evolution occurs over a long period of time in small steps. • This can happen from environmental changes. The species may not officially change, but subtle changes/trends occur over time. (Humans are getting taller). Punctuated Equilibrium • A particular species undergoes change very quickly from the parent species and then may remain largely unchanged for an extended period of time. • This can happen from environmental changes. • Stasis, change and reintroduction (snail example) • http://evolution.berkeley.edu/evolibrary/article/side_0_0/punctuate d_01 Gradualism vs Punctuated Evolution Coevolution • occurs when changes in species' genetic compositions reciprocally affect each other's evolution. • Can lead to exclusivity of certain plants/animals becoming dependent on one another for survival. Evolved to live with one another. Mass Extinction • An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. • last such extinction was 65 million years ago – three quarters of plant and animal species were wiped out. (Clay from this time period has lots of iridium – uncommon on earth but common on asteroids. With some exceptions many organisms (tetrapods) exceeding 55 pounds did not survive. P-Tr Extinction event. Cause – Anoxia, Meteor, Volcanoes? Evolutionary Arms Race • an evolutionary arms race is an evolutionary struggle between competing sets of co-evolving genes, traits, or species, that develop adaptations and counteradaptations against each other, resembling an arms race, which could be, and often are, described as examples of positive feedback. • Host-parasite – virulence vs resistance. • Adaptations and counter-adaptions (selective pressures). Symmetrical – direct competition. Asymmetrical – counter competition (right) Adaptive radiation • Adaptive radiation is the tendency of beneficial traits in a particular species to radiate out from and to a particular location/ecological niche. • However, when/if they spread out, this is when we observe similar species in different locations that may now be separated by natural or man-made boundaries. Recent Article • Human Evolution Update http://www.sciencemag.org/news/2016/09/almost-all-living-peopleoutside-africa-trace-back-single-migration-over-50000-years