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Lecture 19

Biology Lecture 19.docx

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Biology 1001A
Tom Haffie

Biology Lecture 19: Evolution/Ecology  Evolution Ecology: o Ecology: Interactions between organisms and their environment  Biotic component: organisms interacting with other living things  Abiotic component: everything else an organism interacts with o Ecological interactions affect evolutionary processes such as the rates of speciation and extinction and patterns of selection and evolution (micro evolutionary processes)  Evolutionary ecology and biodiversity: o Biodiversity: the species richness (the total number of species alive on earth or alive in a particular place at a particular point in time) o Biodiversity is constantly changing and reflects a balance between speciation and extinction, which are constantly occuring o Vast majority of species on the planet that have ever lived are extinct, but these species are constantly being replaced by new species coming into existence  Adaptive radiation: extreme speciation: o Adaptive radiation: an extremely rapid speciation event (in a small period of evolutionary time, one ancestral species diverges into many different descendant species) o Evolutionary innovation: allows a lineage to open up a variety of different ecological niches, then it can undergo adaptive radiation o When an ancestral species colonizes a new area in which it no longer has to compete with other species in its original range, it can result in multiple ecological niches opening up (Example: Darwin's finches) o A release from competition due to mass extinction (for example, asteroid taking out dinosaurs and freeing up mammals) can create adaptive radiation  Extinction: o Background level extinction: extinction are always occurring, but tends to be low o The likelihood of going extinct is not related to the length of time a species has been on the earth (species won't go extinct from old age) o Some groups are more "extinction prone" due to differences in breeding ecology  Mass extinctions: the Big 5: o Usually there is more speciation going on instead of extinction o There have been 5 periods in which the number of species on earth have decreased drastically  A sixth mass extinction: o Approx. 10 000 - 30 000 species in close proximity to extinction at this moment, which far exceed the numbers for background level of extinction o Thus it appears we are at the beginning of the onset for a sixth mass extinction period o Unlike the other mass extinctions, this has mostly to do with human impacts  When two species interact..: o Anytime there is an interaction
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