BIO342H5 Lecture Notes - Heritability, Phagocytosis, Richard Lenski

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Published on 30 Jan 2013
BIO342 Lecture 2: Evidence for Evolution and Origins of Life
Educational Goals
define "decent with modification" and “phylogeny”
recognize how fossils contribute to our understanding of evolution
homology and its evolution and interpretation
understand the hypothesis for the evolution of early life
Recall from class 1
Evolution is a change in the frequency of an allele or genotype through time
within a population
frequency - population at single locus, two copies of allele, A and B
varies from 0 to 1, if both start at being 0.5, both equally common, A
increase to 1, then B would decrease to 0 because added up together
must equal 1
Phenotypic evolution occurs when a change in the frequency of alleles or
genotypes cause a change in the distribution of phenotypic traits within a
Descent with modification
All organisms present or past are descended from a single common ancestor.
During this time lineages have genetically and phenotypically changed and split
to form many branches.
This is the concept of: descent of modification
Tree of life and phylogenies
The Tree of Life
single lineage, split to more lineage, some went extinct, some continue to present
day to have diversity today
Tree of life = Phylogeny
a phylogeny is a representation of the history of descent and thus common
relationships between organisms
node - single population over 100 millions of years - diversified and split
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Evidence for evolution
What is the evidence that organisms evolve and diversify?
2 forms of evidence:
pattern based evidence: fingerprints of evolution that have been left through
direct evidence (watch it happen)
Where did birds come from and how did they evolve?
common: all have feathers and wishbone - support for ribcage for flight, does not
collapse on them
Paleontology is the study of ancient organisms preserved in the fossil record
like time travellers
Paleontological time travel: 318 mya
no birds, no mammals, no crocodiles, some fish
land ferns
hylonomus, partially aquatic
Paleontological time travel: 235 mya
more diversity of plants
more diversity, -poids
anatomically identical to feathers
bone almost like wishbone
Paleontological time travel: 145 mya
flying, wishbone, feathers, like a bird
10 000 types birds, all with feathers and wishbone
What conclusion can we draw from these data?
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