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Kinds of Selection, evolution evidence
Natural Selection
Both Lamark and Darwin stated that species change
over time
Lamark hypothesized that environment causes the
changes in the organism
Darwin hypothesized that environment chooses
favourable variations, and that variation exists
because of the different genetic composition of the
Aritificial Selection
Using the principles of natural selection to
domesticate wild organisms
Chosing desirable characteristics and selectively
breeding organisms
Ex: dog varieties for hunting, racing, herding etc.
Ex: plants selected for pest resitance, productivity
Accidental Selection
Humans create unintentional changes in the genetic
characteristics of organisms
Ex: DDT resistant insects
Ex: antibiotic resistant bacteria
Evidence that organisms evolve over
Direct Evidence: Fossils
Provide evidence for how organisms have changed
Many fossils represent species that have gone
Others have undergone little change
Indirect Evidence: Looking for patterns such as
similarities and differences in species that are still
a) Embryology
b) Anatomy
c) Vestigal structures
d) Physiological evidence
e) Biochemical evidence
Study of organisms in the early stages of
ex: what do the eggs look like? *see page 69
Homologous structures
Similar structure, different function
Seal flippers and human arms have a different
function but similar origin
Analogous structures
Similar function, different origin of structures
Bat and insect wings perform the same function but
have different origins
Vestigal structures
Structures or organs which no longer have a function
(ex: human tailbone, male nipples)
Physiological evidence
Hormones which are the same between species
Hormones such as progesterone and estrogen for
human birth control pills come from horses
Biochemical Evidence
Similarities or differences between DNA
Our DNA has some similarities to primates
Patterns of evolution: Divergent
When one species can evolve to give rise to many
different species
Ex: One ancestor species diverges into two new
species due to structural, behavioural or
physiological changes to adapt to various
Homologous structures provide evidence for
Patterns of evolution: convergent
When unrelated species develop similar
characteristics because of adaptations to a similar
environment and way of life
Ex: tasmanian wolf (marsupial from australia) and
Timber wolf (placental mammal from N.A.) Both
are predators that look similar
Analagous structures provide evidence for
convergent evolution (*see pg 78, fig 2.19)