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Observations of Evolutionary Change

By Preethi Govindarajan

Preethi Govindarajan

on 7 May 2013

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Transcript of Observations of Evolutionary Change

Observations of Evolutionary Change Fossils and Evolutionary Change Biogeography Convergent Evolution Selective Breeding Homologies Why is this important?
Fossil record is incomplete but still useful
Used to observe evolutionary change Broad skull
Eyes mounted on head
Flexible neck
Differences in pectoral fin 4 toes on its front feet and 3 on its hind feet that were enclosed in fleshy pads Was about the size of a dog Teeth were small compared to modern horses How can these changes be explained? Natural selection!
Dense forests were replaced by grasslands
Began eating grass What is convergent evolution? When species from different lineages evolve similar characteristics that are suited for similar environments Giant anteater Giant anteater and Echidna Echidna Both have long snouts and tongues Sea raven and Longhorn sculpin Antifreeze protein rich in cysteine; B-sheet formation Antifreeze protein rich in glutamine; largely a-helices Both produce antifreeze proteins to survive subfreezing temperatures Analogous structures or convergent traits Traits that have emerged independently in different species that occupy similar environments
Long snouts of the giant anteater and the echidna
Antifreeze proteins of the sea raven and the longhorn scuplin What is selective breeding? A human-driven procedure that uses artificial selection to create species that have desirable traits
Also known as artifical selection Wild Mustard Plant What is selective breeding used for? Dog Breeding To obtain domesticated species with desirable traits
Both animal and plant species Can interbreed since they are all of the same species Corn Experiment Began with corn that had an oil content of 4-6%
Divided into 2 groups
High oil content
Low oil content
18% oil in one group
Less than 1% oil in the other group What is a homology? A similarity that has occurred due to common ancestry Anatomical Homologies Developmental Homologies Molecular Homologies Comparing anatomical structures can reveal similarities
These similarities can point towards evolutionary changes The same set of bones is found in all of these structures
Modified to perform differently in different organisms
Indicates that humans, turtles, bats, and whales evolved from a common ancestor Is able to occur due to genetic variation
Differences in alleles that determine the trait Homologous structures are structures that are similar to eachother because the organisms that have the similar structures share a common ancestor. Vestigial structures are anatomical structures that no longer have a function in modern organisms Manatees have fingernails! Similarities in embryonic development that are temporary
Reveals evolutionary history
Species that are closely related share developmental pathways Similarities in organisms at the molecular level
DNA to store information
Biochemical pathways
Genetic sequences What is biogeography? The study of the distribution of both extinct and living species through space and geological time What does biogeography tell us? Past evolution patterns
The role of geography in evolution
How landmass distribution relates to the evolution of major groups of animals Endemic Species Species that are naturally found in particular areas
Usually occurs in islands that are isolated
Endemic island species often have closely related species mainland 3-6 pounds
Feeds on fruits, insects, and mice 7-11 pounds Crossed over to the Channel Islands during an Ice Age when the Santa Barbra Channel froze over Landmass Distribution Mammals arose about 200 mya
Placental mammals arose after continental drift isolated Australia from other continents
Marsupials in Australia Poll! Poll! Poll! Another
Poll! Last
Poll Help support the theory of evolution
Fossil records show successive evolutionary change
Biogeography shows how geographic distributions and barriers impacts evolution
Selective breeding shows that selection (artificial in this case) can lead to the modification of traits in domesticated species
Homologies point towards species that have a common ancestor
Anatomical - Homologous structures
Developmental - Past evolutionary relationships
Molecular - All living species were derived from a common ancestor
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