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Patterns of Evolution

Patterns of Evolution. The Rate of Evolution. Scientists use two basic terms to describe the rate of evolution: Punctuated equilibrium – describes pattern of long stable periods interrupted by brief periods of more rapid change.

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Patterns of Evolution

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  1. Patterns of Evolution

  2. The Rate of Evolution • Scientists use two basic terms to describe the rate of evolution: • Punctuated equilibrium – describes pattern of long stable periods interrupted by brief periods of more rapid change.

  3. Gradualism – describes a slow, steady change in a population over time http://www.ideacenter.org/stuff/contentmgr/files/34ba8a8b571e676d2e06742b48603094/misc/gradualism.gif

  4. Genus and species A liger can not mate with another liger and have offspring! • Genus: group of closely related species, and the first part of the scientific name in binomial nomenclature • Species: group of organisms that can breed and produce fertile offspring http://www.evcforum.net/RefLib/LigersWolphins_files/223liger.jpg

  5. Review: What is a niche? Niche – the full range of physical and biological conditions in which an organism lives and the way an organism used those conditions. (Where it lives and its role in the environment). An organism’s fitness is higher within its niche than outsideof its niche. Ex.: A penguin’s fitness is higher in Antarctica than in Chapel Hill.

  6. No two species can have the same niche. • Species compete for the food and resources within a niche. • The most competitive species survives and maintains the niche. • The less competitive species either dies out or finds a new niche. http://www.paklinks.com/gsmedia/files/18Plus/2a.jpg

  7. Speciation • Speciation is the development of a new species. • It occurs when a species moves into an unoccupied niche. • Populations evolve and become reproductively isolated from each other. (Cannot interbreed and produce fertile offspring) • Over time, the species evolves adaptations that are more suitable to its new niche. http://taxonomy.zoology.gla.ac.uk/~rdmp1c/teaching/L1/Evolution/l6/speciation.jpg

  8. Different Niches for Different Beaks

  9. When does speciation occur? • Speciation can only occur when populations are reproductively isolated from one another. • Reproductive isolation – means a population can no longer interbreed with a population in another area. • Only happens when the gene pools are separate.

  10. Maintaining Reproductive Isolation • There are three basic factors that maintain reproductive isolation.: • Geographic Isolation: populations separated by physical barriers (rivers, mountains, bodies of water). • Behavioral Isolation: capable of interbreeding, but have different courtship rituals.. • Temporal Isolation: reproduce at different times.

  11. Geographic Barriers • When a land formation, such as a mountain, canyon, river, etc. prevent populations from breeding. • Ex. Beetles divided by a river. http://evolution.berkeley.edu/evolibrary/images/history/geog_isolation.gif

  12. Behavioral Isolation When differences in mating rituals. • Ex.: Peacock mating dance. Temporal Isolation • Ex.: When plants release pollen at different times. http://biology.clc.uc.edu/graphics/bio303/sexualselection.jpg http://pinker.wjh.harvard.edu/photos/cambridge_boston/images/trees%20in%20Cambridge%20Common.jpg

  13. Speciation via Reproductive Isolation Reproductive isolation occurs between two populations of the same species. Populations become adapted to different environments. Separate gene pools become less similar. Eventually reproductive isolation becomes permanent. Two different species form.

  14. Speciation doesn’t always happen. • When the gene pool for a population is very small, there is less variation. • This makes it difficult for populations to adapt to a new niche. • These populations often become extinct.

  15. Patterns of Evolution • There are several different ways that evolution can occur: 1. Adaptive radiation – One species gives rise to several different forms (new species) that appear different externally, live in different ways, but are similar internally. • This is an example of divergent evolution. • Often occurs when there are empty niches in a community, following an event of mass extinction. • The adaptive radiation of mammals occurred after the extinction of dinosaurs.

  16. 2. Convergent evolution – different groups developing similar adaptations because they live in the same type of environment • Ex: sharks, dolphins, and penguins. http://www.dolphindreamteam.com/pictures/pics/swimdolphin.jpg http://www.aqua-firma.co.uk/editorfiles/Image/Antarctica/uw-penguin-upload1.jpg http://www.flmnh.ufl.edu/fish/gallery/descript/TigerShark/scars.JPG

  17. 3. Coevolution – two species evolve together, responding to changes in each other and becoming uniquely adapted to one another • Ex. Mitochondria and the Eukaryotic Cell • Ex. Plants and their Pollinators • Ex. Flowers and plant eating insects. http://www.olympusmicro.com/micd/galleries/darkfield/butterflyproboscis.html http://streaming.wcp.muohio.edu/western/insects/butterfly_proboscis.jpg

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