Download Natural Selection 03.25.04

Evidence for Evolution
(Chapter 18 and…)
The real fossil bones of the walking and swimming whale, Ambulocetus natans, are spread
out in this picture with a sledgehammer for scale. The skeleton was about 12 feet long and
is about 49 million years old. It was found in Pakistan.
Evidence for Evolution
1. Remains of living organisms can be trapped and preserved
in…
• resins that turn to amber
• frozen in ice or snow
• in sediments that produce fossils (most important)
• date rocks and fossils using radioactive isotopes
• whether an organism is preserved greatly depends on the
local environment in which it died
• heated debate exists regarding the species identification
for new specimens based only on fossil record
– therefore, paleoanthropologists often use the term
paleospecies instead of species
– Scientists look for paleontological evidence–
specifically transitional fossils
• example: Archaeopteryx -- transitional form
between birds and reptiles
• microraptor
• Homo habilis
• Lucy
Evolving Ideas: How Do We
Know Evolution Happens?
http://www.pbs.org/wgbh/evolution/library/11/2/e_s_3.html
2. Biography/Geographical Distribution
• the study of the distribution of living things (or
fossils) over the Earth
• a heated debate exists on human evolution
• research based on DNA supports the “Out Of
Africa” hypothesis that all modern humans stem
from a single group of Homo sapiens who
emigrated from Africa 2,000 generations ago and
spread throughout Eurasia over thousands of
years
– these settlers replaced other early humans (such as
Neanderthals), rather than interbreeding with them
3. Comparative Embryology/Anatomy
• embryos of vertebrates look
similar
• useful when don’t have much
of a fossil record
• almost all mammals have seven
cervical (neck) vertebrae and
gill arches
• Ontogeny recapitulates
phylogeny
– the idea that the embryonic
development is similar to
evolution
German biologist, naturalist, philosopher, physician, professor and artist who discovered, described and named thousands of new
species (see below), mapped a genealogical tree relating all life forms, and coined many terms in biology, including phylum,
phylogeny, ecology and the kingdom Protista (details below). Haeckel promoted Charles Darwin's work in Germany and developed
the controversial "recapitulation theory" claiming that an individual organism's biological development, or ontogeny, parallels and
summarizes its species' entire evolutionary development, or phylogeny: "ontogeny recapitulates phylogeny" (see below).
• Homologous structures
– have a common evolutionary origin, but can
look quite different and have different functions
– ex. forelimbs of birds, bat, horse, humans...
• Analogous structures
– have similar functions, may appear similar,
yet presumed to have different evolutionary
origins
– ex. wings of an insect and bird
wings of bat, bird (though the BONES are
homologous!), insect:
4. Biochemistry
• all living organisms use DNA/RNA as
genetic material
• all (except bacteria) use the same 20
amino acids to make their proteins
– differences of a.a. sequences accumulate
(mutations) at a constant rate and therefore
can be used as an evolutionary clock
– the more differences in proteins, the less
likely organisms are “related”
4. Selective Breeding of Domesticated
Animals
• artificial selection
When selective breeding goes too far
The government has confirmed that it will use a report on the
selective breeding of freak pets - including fancy goldfish - to shape
the Animal Welfare Bill.