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Vert Bio Notes Lecture 2

by: Erica Baken

Vert Bio Notes Lecture 2 BIOL 365

Marketplace > Iowa State University > Biology > BIOL 365 > Vert Bio Notes Lecture 2
Erica Baken
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These notes, in conjunction with the slides provided by Dr. Adams, cover all the content discussed in class for lecture 2.
Vertebrate Biology
Dr. Dean Adams
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This 5 page Class Notes was uploaded by Erica Baken on Tuesday August 30, 2016. The Class Notes belongs to BIOL 365 at Iowa State University taught by Dr. Dean Adams in Fall 2016. Since its upload, it has received 4 views. For similar materials see Vertebrate Biology in Biology at Iowa State University.


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Date Created: 08/30/16
8/24 - Day 2: Systematics and Vertebrate Evolution Reading: Chapter 1 of Pough et al • Travis is the SI leader: Fill out survey for times for SI sessions • Free tutoring sessions 3 1-hour sessions every week • • Keep in mind: each phylogeny is a hypothesis • Systematics: a scientific study of the kinds and diversity of organisms and their evolutionary relationships • A systematist will describe, name, and classify organisms • Taxonomy is a related discipline: provides the names and rules for naming/grouping Taxonomy • Binomial nomenclature: the tool used to name every species on the planet. The two latin names (genus, species, example: Homo (genus) sapien (species) Deeper classification is necessary, which is what the deeper classifications are for (kingdom, • phylum, class, order, family, order, genus and species) • Species are main taxonomic units in Linnaean classification • Species are ‘types’ of organisms • Similar characteristics and are reproductively isolated from other groups • Species is a very hard concept to define • Traditional classification • Prior to Darwin, most believed species are eternal (never go extinct), immutable (unchanging), and discrete (clear cut differences between them) • Essentialism leads to the idea that there are specific traits that will clearly distinguish between species • Essentialism describes variation in a species (the fact that humans have different heights, skin colors, hair colors, etc) by saying that they are all imperfections around an idealized form • This, combined with Linnaean hierarchy generated species classifications • Radical shift in 19th century because of new observations contradicting traditional classification: • (1) Species are not eternal: many fossils of extinct forms were discovered • (2) Species are not immutable: humans can change animals with domestication of plants and animals (3) Variation in nature is common and seems important for survival of individuals: not just • mistakes • Darwin: On the Origin of Species: Provided a mechanistic model that explained these observations and demonstrated how new species are generated • Alfred Russel Wallace came up with the same idea, Darwin and Wallace presented the info together Evolution by natural selection • Changes happen in the time unit of generations • The most dramatic shift in biological thinking Happens differently in different populations • • Requirements • (1) More individuals are born each generation that can survive to reproduction • (2) There is trait variation • (3) The trait variation is heritable • (4) Trait differences affect fitness (fitness = survival to reproductive age) • Evolution by natural selection is not random, but MUTATIONS may be random. • Consequences in systematics: Thought changes • Species share traits because of common evolutionary history Implies ‘tree of life’ describing the relationships among species • • Evolutionary tree = phylogeny • This thought process started the importance of analogous vs homologous traits. • Homologous traits are traits that are similar between species because it used to be the same thing in the evolutionary past • Analogous traits are traits that look similar or function similarly because of similar selection pressures but NOT because their shared ancestor had that trait (example: bat wings and bird wings) • Phylogenetics is the modern incarnation of systematics. It is the study of evolutionary relationships among species Shows relationships and outlines traits and when they evolved • • Allows us to group animals together. There are commonly used groupings (reptiles, mammals) but these classifications describe any type of grouping you want to make. 3 different types of grouping: • (1) Monophyletic: All descendants and ancestors of a group • (2) Paraphyletic: All ancestors and SOME BUT NOT ALL descendants of a group (example: reptiles, birds evolved out of reptiles and not included) • (3) Polyphyletic: Descendants but NOT all common ancestors of a group How does speciation happen? What processes allow for speciation? (Speciation song from lecture) • • Reproductive barriers • Physical: streams, mountain ranges, tectonic plates • Sexual: some mutation that stops some from being able to reproduce with others like doubling of genome, differently shaped reproductive organs • Most common types: allopatric (in different places) and sympatric (the same places, needs another type of reproductive barriers) • Allopatric • Vicariant speciation: physical reproductive barriers • Founder effect: a few individuals move out of normal range, far enough so that it doesnt reproduce with the original population. This means that the genes no longer represent the full gambit of genetic diversity. Happens often with Islands • Doesn’t necessarily mean they are two species. They could come back together, and if they can reproduce, there was no speciation. Extreme example: Ring species • Sympatric • Two forms • (1) Ecological: specialize on certain microhabitat, fill different niches • Lizards in caribbean, Cichlids in Lake victoria (?) • (2) Sexual: • Genetic: polyploidy: offspring get one of more extra full sets of chromosomes, immediately unable to reproduce with those that didn’t double • Very common in plants Rules • Bergmann’s Rule: endotherms tend to be larger in colder places • Allen’s rule: extremities of endotherms vary inversely with body size • Gloger’s rule: endotherms living in arid regions tend to be lighter in color • Many others 8/29 - Lecture 4: Origin of Tetrapods • SI sessions: • M 7:10 pm • Tu 6:10 pm • F: 3:10 pm • 0298 Carver Necessary to bring ID • • Origin of Tetrapods is more or less origin of vertebrates Amphibians • 3 orders still alive (7547 species) • Very active discovery of new species • Cryptic species allow for lots of new discovery: look the same but only identified as separate with genetic studies • Amphi = double, bios = life in greek • Refers to the metamorphosis in many amphibians • Odd because both phases are sufficient life styles Larvae body plan is abandoned Very important aspect is their smooth permeable skin • • Gas exchange through skin • Advantages and disadvantages • Disadvantage: tied to water more tightly for their whole life (very humid places or water itself) • Disadvantage: toxins are more easily taken up by these permeable skin • Amphibians are therefore kinda the canary in the coal mine because they’re affected first by toxicity • Mostly all lay eggs, none of the eggs have shells • Most also have external fertilization • Amplexus: frog males grabbing onto the female frog to ensure that both gametes are deposited in the same area Some salamanders have internal fertilization where the male drops a spermatophore • and the female sits on it and takes it into her cloaca Why move to land? • Predation hypothesis • Oceanic seas were filling up, land represents a predator release (safe haven) • Food hypothesis • Plants and invertebrates were already on land, big available food source • Competitor avoidance • Similar to predator hypothesis • We can see this often today Huge increase in amphibians after Devonian (Carboniferous) • After Carboniferous, lost their dominance to reptiles • What did Earth look like during Devonian? • Lots of shallows (lots of contact with land) • Many conditions were getting drier • Lots of plants and insects on land • Lots and lots of tropical areas Problems with transition to life on land • Moving to land is NOT easy • Gravity is strong: need skeleton to support more weight • Locomotion needs to change: limb use Breathing must change: Oxygen is more concentrated in air, but gills don’t work unless • they’re under water • Eating: suction feeding doesn’t work in air • Reproduction: eggs desiccate • Blood: gravity • Sensory systems: refraction is different in water and air, needs to be adjusted for • etc • What organisms were around that could handle these issues? • Sarcopterygiians • Many useful traits • Osteolopiforms (extinct) have cylindrical bodies, shallow water predators, had both gills and nostrils, ALSO nostrils were connected to internal nares, allows air to get back to throat and/or lungs, ossified skeleton, lobe fins, primative pectoral girdle (supports limbs) • internally, you can have moist surface area, allowing for oxygen exchange • Looking at fossils chronologically, you can see the slow transition, little by little from fish to tetrapod • Small degrees of change over time • Acanthostega had 8 toes, this tells us we had elaboration (digits) and reduction (5 in default amphibians) • Ichthyostega: first true land vertebrate • Whatcheeria: early tetrapod from Iowa • Temnospondyls (monophyletic group) • Contains current amphibians AND ancestors Elsmere Island (sp?): area in NW Canada that filled in missing link for terrestrial life • Tiktaalik roseae: mixed features between fish and tetrapods • • Fins with wrists: key innovation, allowing for an explosion of diversity of animals on land (amphibians) • Caecilians • Least known of the 3 amphibian groups • Low population sizes, found in hard to get places • Salamanders • Some salamanders can live up to 20 years • Some species aren’t reproductively mature until age 4 or 5 • Most don’t metamorphose Called direct developers, come out of the egg looking like a mini adult, not a larvae Frogs/Toads • • Live all over in many different microhabitats Not all the problems solved by amphibians, amniotes is the next step in dealing with life on land


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