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This 6 page Class Notes was uploaded by Graham Notetaker on Saturday February 13, 2016. The Class Notes belongs to Bio131 at Elon University taught by David Vandermast in Spring 2016. Since its upload, it has received 44 views. For similar materials see Biodiversity in Biology at Elon University.
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Date Created: 02/13/16
Week of Feb 7th Notes, Quiz 2 prep What we’re doing Feb 8th: ● Phylogenetic trees document the evolutionary relationships among organisms ○ Evidence: Fossil record ● Adaptive radiation are a major PATTERN in the history of life ○ Ex. Darwin's finches ● Mass extinctions happen all the time, and provide for a shift in the hierarchy of life Phylogenetic Trees: ● Phylogeny: The evolutionary history of a group of organisms ● Reconstructs the history of life, uses the fossil record. Shows ancestordescendant relationships. ● What makes a phylogenetic tree? ○ Branch: represents a population through time ○ Node: The point where two branches diverge, represents a time when an ancestral species split into two or more descendant species ○ Tip (terminal node): the endpoint of a branch, represents a group that is living today or ended in extinction ● Microevolution: When a population makes small changes over time ● We analyze morphological and/or genetic characteristics to i nfer relationships The cladistic approach: ● A clade includes an ancestor and all its descendants ● Focuses on synapomorphies , or the shared derived characteristics of the species under study ● Synapomorphies allow us to recognize valid clades, or monophyletic groups ● Clades can be nested within a larger clade ● Types of Clades: ○ Monophyletic clade: a collection of organisms, includes a n ancestor and all its descendants ○ Paraphyletic clade: a grouping that consists of an ancestor and some, but not all of the descendants (use pics for the three types here) ○ Polyphyletic clade: grouping that includes numerous types of organisms that lack a common ancestor Evolution of features: ● BIG DIFFERENCE BETWEEN HOMOLOGOUS STRUCTURES, AND HOMOPLASIES . ● Homoplasies: analogous structures...serve the same function, but evolved separately. ○ Ex, wings of a bat and bird ● Homology occurs when traits are similar due to shared ancestry, (wings of a bat, human arm, cat limb) ● Symplesiomorphy: an ancestral character or trait state shared by two ormore taxa. ● A derived trait is one that was modified from the ancestor. ● Convergent evolution: Natural selection favors similar solutions to the problems posed by a similar way of life (dolphins and sharks look alike, but don’t share a common ancestor) Feb 10th Hox Genes ● Homeobox genes: Master regulatory genes. All organisms have this! ● Evidence: ○ Groups of Hox genes are organized in a similar way in many organisms ○ 180 base pair sequence ○ Products of Hox genes have similar functions ○ Messing with these WILL KILL YOU, that’s why no evolutionary mutations or variations iox genes exist today(Highly evolutionary conserved) Fossil Record...in depth ● Tells us about lifestyle, processes that occurred when the organism was alive ● Fossilization ixceedingly rare ○ 1 out of every 200,000,000 fossilized ● Limitations of the Fossil record: ○ Habitat bias: occurs because organisms that live in areas where sediments are actively being deposited are more likely to be fossilized ○ Taxonomic bias : some organisms are more likely to decay slowly/quicker ○ Temporal bias: more recent fossils are more common to find ○ Abundance bias: the abundant and widespread organisms that are present for a long time are more likely to leave a fossil ● Niche: describes the range of resources that a species can use/ tolerate ● Genetic diversity (heterozygous, multiple alleles code for more than one thing?) allows for variation in an organism (Darwin's finches) ● Why does Adaptive Radiation occur? ○ Triggered by morphological innovation ○ New resources/ new ways to exploit resources Cambrian Explosion: 565515 myaish ● Sponges, jellyfish, simple worms, 565 mya end of proterozoic era ● 3 major fossil assemblages:Doushantuo, Ediacaran, Burgess shale The presence of these rich deposits makes the fossil record really complete and accurate. ○ Doushantuo: China. Precambrian. Found sponges, and multicellularity, animal embryos. First animals, sexual reproduction=greater diversity of life. ○ Ediacaran: Australia. small soft bodied, sponges, jellyfish, and other traces of animals. 544565 mya,recambrian ○ Burgess shale fauna: Every living animal group is represented here. Huge increase in size, and diversity. Predatorprey relationships form. ● Punctuated equilibrium: A stable, constant and relatively small rate of change that ipunctuated by a period of great change. Why so much change so fast? 1. Increased oxygen levels made aerobic respiration more efficient. 2. Evolution of predator prey relationships. Exerted more pressure for offenders, and predators to be good at what they do. 3. Snowball earth had just melted. New niches mean more new niches. If you can exploit one new niche, you create a niche for predators/ prey to fill 4. New genes, new body. Mutations increase hox genes that made it possible for larger more complex bodies to evolve. Mass extinction: 60% or more of the species are wiped out within 1 million years. Happens from one dramatic event. Background Extinctions: Normal rate of extinction. Occurs when normal environmental changes, emerging diseases, or competition reduces populations to zero. Results primarily from natural selection. Evidence for the 6th mass extinctio: Current rate is 1001000 times the background rate. Some call it homogenocene. Fun facts: ● Human species are 160,000 years old ● Homo erectus is the ancestor of homo sapien ● Extant: A species that are currently living ● “syn” means shared ● Humans have less than 10% genetic variation ● Beetles and flowers are two the most diverse species on Earth ● EndPermian Extinction: Largest mass extinction. over 80% of all life disappeared
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