C. Thomas Malthus (an economist)

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C. Thomas Malthus (an economist) 1. Essay
on the Principles of Population (1798) a.
populations of organisms increase geometrically
b. rate of reproduction too high to be
sustained c. warning against human
overpopulation
2. but in nature, this does not seem to occur 3.
Darwins answer death (selection) limits
population numbers 4. This provided missing
link for Darwin
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D. Alfred Wallace 1. came to same
conclusions while in Indonesia 2. published
his findings along with Darwin (1858-59)
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E. Darwin On the Origin of Species by Means of
Natural Selection 1. descent with
modification 2. closely related species
likely from common ancestor
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Darwins Theory
Hypothesis 1 Every organism has the potential to
leave more than one offspring.
Hypothesis 2 The number of individuals within a
species remains fairly constant over time.
Prediction A If 1 and 2 are true, then not all
individuals realize their reproductive potential.
Hypothesis 3 Individuals within a species vary
in terms of their traits.
Hypothesis 4 At least some of these traits are
inherited.
Prediction B If A, 3, and 4 are true, then some
individuals are better suited for their
environment, leaving more offspring.
Their traits become more common.
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Darwins Theory
Better suited individuals have inherited those
traits, and they pass them on to their offspring.
Survival of the fittest Reproduction of the
fittest.
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What is the evidence for evolution?
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Silurian and Devonian fishes (Modified from
Fenton and Fenton, 1958)
Jurassic and Cretaceous fishes (Modified from
Romer, 1966)
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Radiometric dating (Section 15.5 in the text)
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Half-life of 14C is 5,730 years
(Modified from Bushee and others, 2000)
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(Modified from Bushee and others, 2000)
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Biostratigraphy The science that deals with the
distribution of fossils in the rock record and
organizes strata into units on the basis of their
contained fossils.
The oldest layer is on the bottom. Rocks were
deposited one layer at a time from the bottom up.
(Pojeta and Springer, 2001)
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The combination of strata and radiometric dating
clearly demonstrates progressive change in the
fossil record.
(Modified from Ward and Blackwelder, 1975)
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Organisms have evolved in a historical sequence.
oldest prokaryotes
next early eukaryotes
next fish
next amphibians
next reptiles
next mammals
next birds
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Biogeography
1. geographic distribution of species suggests
evolution from common ancestors
2. Galapagos and South America
3. Australian marsupials
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Comparative Anatomy
1. Homologous structures
from common ancestor
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Comparative Anatomy
1. Homologous structures
from common ancestor
2. Analogous structures (15.14)
similar structures as the result of separate
lineages
flippers of dolphins and penguins
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Comparative Anatomy
3. Vestigial structures
non-functional structure inherited from ancestor
served a useful purpose in the ancestor
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Human Appendix
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Human arrector pili muscles and body hair
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Human Coccyx
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Muscles that move the ears
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Wisdom Teeth
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Wings on flightless birds
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Astyanax mexicanus
Blind cave-dwelling fish
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Dandelions have sex organs, but dont use them.
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Virgin female whiptail lizards (several species)
unisexual all female
will still occasionally mount other females
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Comparative Embryology
1. embryos among some species very similar
2. all vertebrate embryos almost
indistinguishable at certain stages
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Molecular Record
1. as organisms change, so should their genes
2. the more change ? the more alterations in the
nucleotide sequence over time
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3. select a gene to study
a. organisms more distantly related have greater
numbers of differences in their genes
b. closer relatives, fewer differences
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4. molecular family trees
a. support the fossil record
b. confirm the clusters seen in the fossil
record