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ENV notes 3

by: Hannah Fretheim

ENV notes 3 Env 1301

Hannah Fretheim
Baylor University
GPA 3.8

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Evolution, Natural Selection and Food Webs
Exploring Environmental Issues
Trey Brown
Class Notes
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This 2 page Class Notes was uploaded by Hannah Fretheim on Sunday September 18, 2016. The Class Notes belongs to Env 1301 at Baylor University taught by Trey Brown in Fall 2016. Since its upload, it has received 4 views.


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Date Created: 09/18/16
Environmental Science- Class Notes (09/12- 09/14) Natural Selection: - Common descent- The idea that all life on earth is related through a common ancestor. - Descent with modification- Parents pass traits to their children, but children are different from their parents and from their siblings. - Natural Selection gave credibility to the theory of evolution because it provided a natural mechanism for it. - It is based on the idea that creatures with certain beneficial traits will survive and pass those traits on to their offspring while those who do not have the beneficial traits will die off. Evidence that led to idea of Natural Selection: - Throughout history, people have domesticated animals by breeding them to have the traits that benefit us. - Galapagos tortoises- Tortoises on different islands were similar, but were different enough to be considered separate species. The differences between the species corresponded with what was beneficial to life on the specific island that each species lived on. Evidence for Evolution: - Comparative anatomy, embryology, fossil record, DNA comparisons - Example of cetaceans (whales and dolphins): o Comparative anatomy- Whales have placentas and give live birth like other mammals. They also have blowholes which are like mammal noses and a strange pair of bones where leg bones should be. o Embryology- The embryos of dolphins and humans look similar (as do those of many other animals). o Fossil record- Fossils of whales from long ago had the blowhole closer to the front of their face like a nostril. Other fossils seem to reveal a whale-like species with legs. o DNA comparisons- Whale DNA is very similar to the DNA of hippos. They also have similar features which seem to indicate a common ancestor. o All of these things point to whales descending from a four-legged ancestor. - There are many similarities between bird wings and reptile claws. - There seems to be evidence that mammals descended from reptiles which descended from amphibians which descended from fish. How Evolution Works: - Creatures are of the same species if they can reproduce with each other offspring which can also reproduce. - More offspring are produced than are needed, which creates more diversity within a species. - Recombination- DNA of two parents is combined - Mutation- DNA changes slightly, making offspring different from parents - The offspring with more beneficial traits survive and pass on their traits while those with less beneficial traits die. Darwin and the Gallapagos finches: - One species of finches spread across multiple islands. Those with beaks that were unique, had less competition for food and survived while others died off. Eventually, the finches on each island became so different from those on other islands that they were no longer the same species. - The differences between the species of finches were specific to the individual islands that each lived on. Ways that Environmental Science has connected to Evolution: - Habitat destruction, overharvesting, non-native species - Example: In order to preserve fish populations, people were catching big fish and putting back little ones so that the little ones could grow. The fish then became smaller overall. o Explanation- The adult fish that were naturally smaller had an advantage because they were less likely to be caught. Eventually, the fish population evolved to be smaller. - Example: When HIV was discovered they could not figure out where it came from or how the different strains connected. Eventually, a connection between the strains was found. It was also found that HIV may have spread to humans from the blood of chimps. - Example: Some grasslands have become deserts. o Explanation- When grassland shrinks due to habitat destruction, the animal species that rely on grasslands shrink. Because these animals fertilize the grasslands, the loss of them turns the grasslands into deserts. Food webs - Include producers which make food, primary consumers which consume producers as well as secondary and tertiary consumers which eat other consumers. - There are also decomposers and detritus which break things down. - More biodiversity leads to more possible food paths. Aquatic ecosystems have more biodiversity than tundra or desert ecosystems.


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