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Evolution
Evolution
– any process of
change over time.
Geologic Time – A record of
Earth’s history found in rocks
and fossils.
Earth’s age – about 4.6 billion
yrs.
 Relative age of rocks
determined by their position.
Grand Canyon
Older
fossils
show that life
forms started
as simple,
single celled
organisms.
History
of Evolution
 1. Lamarck (1809) –
thought evolution resulted
from striving for
improvement.

- a) organs appeared as
needed and could be
improved with use. Then
passed to offspring.
-b) If not needed, organs
disappeared in next generation.

-c) Transmission of acquired traits.
(lose an arm, offspring could be born
that way)

 Weismann(1870)
– disproved
Lamarck. Cut off tails of mice
and all the offspring still had
tails.
Charles Darwin
The Voyage of the Beagle
 Darwin’s
Theory of Natural
Selection based on:

1. Overproduction – due to
limited space and food, more
offspring produced than can
survive.

2. Competition - members of
a population compete for food
and mates.
 3.
Variation – because of
different characteristics, some
better able to survive.
 4. Survival of the fittest – those
that survive longer will live to
reproduce.
 5. Transmission of favorable
traits – offspring of fittest
parents will inherit their
favorable traits.
 6.
Evolution –
as populations
change due to
these new
favorable traits,
that is evolution
ameoba sisters natural selection
Modern Theory of Evolution
 Variation
– caused by “shuffling” of
genes during sexual reproduction.
Also caused by random mutations
 Natural Selection – due to passing on
of genes for favorable traits.
 Geographic Isolation – 1 species can
become 2 different ones if a
population gets separated by
mountains or plates separating.
 Environmental
Changes – stable
environment = not much change

- changes in the environment
select for different traits to
become successful.

ex: antibiotics lead to resistant
strains of bacteria
Rates of Evolutionary Change
Gradualism – changes occur
little by little over long time.
 2. Punctuated Equilibrium –
things are stable until brief, fast
change occurs. Then stable
again.
 1.

** Species with short life spans and
large numbers of offspring can
change very quickly. Ex: bacteria,
insects
Similarities between related species
1. Comparative Anatomy – similar
body structures
 Homologous
Structures –
same structure
different
function
Analagous
structures –
similar
function but
different
structure.
Not close
relationship
Similar
parts
cell
Similar
embryos