ANTH 100 Lecture Notes - Transitional Fossil, Species Ii, Selective Breeding

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Published on 27 Jun 2012
School
UBC
Department
Anthropology
Course
ANTH 100A
Professor
Biol 121 225
Freeman 484-490 Mar 8, 10
Evolution 2- Ch. 24, Evidence for Evolution
Main points of Darwin’s theory?
1. Evolution “descent with modification”
-all organisms have a common ancestor Linnanean hierarchy, “tree of life”
-two species in a family are more closely related than those in different families in the
same class
-the environment changes traits in a population over time/over generations (allele
frequency changes in a population)
2. Natural selection the mechanism of evolution
Premises:
-genetic variation exists
-performance affects reproductive success higher fitness
-competition differential survival
-natural selection occurs through interaction between environment and existing
genetic variation in a population
-it causes a change in the population resulting in increase in those better suited for
survival
-variable population because of adaptation of population to environment
variation + selection = adaptation
Evidence for evolution
1) Evidence for change through
time
a) Fossil record
i) Extinctions
-the fossil record
-extinct species can be noticed in fossils containing shells, bones, leaves, bird tracks,
dung, etc
-this was used as evidence by Darwin who then said that species were not static,
immutable entities
-his reasoning: since species have gone extinct, array of species living on Earth
changes over time
ii) Transitional forms
E.g.whales
-when a species evolves over generations, it may enter many transitional forms
-transitional form = fossil species with traits that are intermediate b/t those of older
and young spp.
-was known as the “law of succession” when there were resemblances b/t fossils
found in rocks underlying certain regions and the living spp. found in the same
geographic area
-Evolution of whales: Whales evolved from terrestrial mammals to the aquatic
mammals of today
-transitional forms had shorter legs with time, as well as a flatter body
-eventually, legs disappeared and became small fins
b) Changes in living organisms
i) Vestigial trait
-a vestigial trait is a reduced or incompletely developed structure that has no function
or reduced function, but is clearly similar to functioning organs or structures in closely
related species
-for example, humans have tailbones (coccyx) but we don’t have tails
-also, appendix in human is reduced version of cecum digestive organ in other
species
ii) Artificial selection
-spindly flowering stalk (Brassica aleracea)
-if you select individuals with largest and most compact flowering stalks and breed
them, and do so for a few generations, you will get broccoli
-basically, you can breed/cross individuals that have a specific trait of interest
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Document Summary

Evidence for evolution: evidence for change through time, fossil record, extinctions, transitional forms. E. g. whales: changes in living organisms, vestigial trait, artificial selection, evolution descent with modification . All organisms have a common ancestor linnanean hierarchy, tree of life . Two species in a family are more closely related than those in different families in the same class. The environment changes traits in a population over time/over generations (allele frequency changes in a population: natural selection the mechanism of evolution. Natural selection occurs through interaction between environment and existing genetic variation in a population. It causes a change in the population resulting in increase in those better suited for survival. Variable population because of adaptation of population to environment variation + selection = adaptation. Extinct species can be noticed in fossils containing shells, bones, leaves, bird tracks, dung, etc. This was used as evidence by darwin who then said that species were not static, immutable entities.

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