2. Divergent Evolution

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Evolution:
Evidence of Change &
How Change Occurs
Evolution
- Change over time
- Process where modern
organisms have descended
from ancestors with
modifications
Early Evolutionary Ideas
1.Lamarck
- among the
first to
explain how
organisms
change
over time
- later
disproved
Lamarck
- relied on 2 assumptions:
1.Use and disuse
2.Inheritance of acquired
traits
- both later disproved
2. Charles Darwin
(1809-1882)
- developed the
theory of
evolution by
natural selection
- traveled around the world
as a naturalist (1831-1836)
Galapagos wildlife
Darwin’s Finches & their food
Large seeds
Small seeds
Insects
Leaves
Evolution by Natural
Selection
- Natural
Selection is
the result of
3 natural
processes:
1. Natural Variation:
- all organisms produced sexually
are genetically different due to
gene recombination and mutations
Variation in Human Height
2. Adaptation
This natural variation or mutation
may be an adaptation that helps
them outcompete others to survive
and reproduce.
2. Competition
-
resources (food, space, water)
mates
constant struggle for existence
winners reproduce
Gazelles struggling to reach food.
Male caribou competing for mates.
.Natural Selection or
survival of the fittest
- Those best suited will survive
longer and reproduce.
- Those not suited will not
survive or reproduce as often.
3. Heredity
- Those that survive
will pass on the
very traits that
helped it survive.
Woodpecker
Artificial Selection
- similar to
natural
selection
- domestic
crops and
animals
vary a lot
Artificial Selection
Artificial Selection
- only the best animals or
plants are allowed to
produce offspring
Artificial Selection
Recent Examples of
Evolution
1. Peppered Moths
a.Before industrial revolution,
most moths were grayish and
well camouflaged.
b. During the industrial revolution,
soot stained the bark black.
- Rarer dark moths were then
better camouflaged.
- The more common light moths
were easily seen and eaten.
c.Dark moths had greater fitness
and became more common.
2.Resistant Diseases & Pests
a. Increased resistance to
antibiotic by bacteria
b. Insects have become more
resistant to pesticides
Resistant Pests
C. Speciation
- development of one species
from another species
C. Speciation
Kaibab Squirrel
Abert Squirrel
1. Process of Speciation
a. Separation of original population
by a geographic barrier
b. Changed environment
c. Gene pool changes
d. Reproductive isolation
- two populations can no longer
interbreed
e. New species arises
(a)
Single species;
Same habitat
(b)
Speciation
Geographical barrier;
isolated populations
(c)
Genetic drift;
tan vs white mice
Barrier removed;
mix but don’t interbreed
(d)
2. Divergent Evolution
(Adaptive Radiation)
- ancestral population
evolves into several
different species
2. Adaptive Radiation
Hawaiian
Honeycreepers
2. Adaptive Radiation
3. Convergent Evolution
- different organisms evolve
similar adaptations to survive
in similar niches
- develop analogous structures
(similar function with different
underlying anatomy)
3. Convergent Evolution
3. Convergent Evolution
European Hare
(lagamorph))
Patagonian “Hare”
(rodent)
Banded Wallaby
(marsupial)
3. Convergent Evolution
Tasmanian “Wolf”
Coyote
Placentals
Marsupials
Tasmanian
“Wolf”
Wolf
Ocelot
Anteater
Flying
Squirrel
Quoll
Numbat
Flying
Phalanger
Marmot
Wombat
3. Convergent Evolution
American Cactus
African Euphorb
D.Evolutionary Theory Evolves
1. Genetic Drift
- random changes in allele
frequency produce new
traits
D.Evolutionary Theory Evolves
1. Genetic Drift
Masai Giraffe
Rothschild Giraffe
Reticulated Giraffe
D.Evolutionary Theory Evolves
2. Unchanged Gene Pools
- "living fossils": sharks,
horseshoe crabs, coelacanth
Chambered Nautilus
Coelacanth
Horseshoe Crab
3. Gradualism:
- slow change over time
4.Punctuated Equilibrium
- periods of little change,
followed by abrupt change
Gradualism
Punctuated
Equilibrium
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