Transcript Evolution - La Cañada Unified School District

Evolution,
Biodiversity, and
Community
Processes
La Cañada High School
Dr. E
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Evolution – What
Next?
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What types of Life
exist on the Earth?
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Types of Organisms
• Prokaryotic Kingdom: singlecelled organisms containing no
internal structures surrounded by
membranes (therefore there is no
nucleus)
– Monera – bacteria and
cyanobacteria
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Endosymbiotic Theory
Chloroplast
Aerobic
bacteria
Ancient Prokaryotes
Nuclear
envelope
evolving
Photosynthetic
bacteria
Plants and
plantlike
protists
Mitochondrion
Primitive Photosynthetic
Eukaryote
Ancient Anaerobic
Prokaryote
Primitive Aerobic
Eukaryote
Animals, fungi, and
non-plantlike protists
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Types of Organisms
• Eukaryotic Kingdoms: all organisms consisting of
cells which contain membrane-bound nuclei
– Protista - mostly one-celled organisms – have
characteristics of all three other Eukaryote Kingdoms
– Fungi - organisms which decompose stuff
– Plantae - organisms which use photosynthesis to make
their own food
• Annuals complete life cycle in one season
• Perennials live for more than one season
– Animalia - organisms which must get organic compounds
from food they eat - most are able to move
• Invertebrates – no backbone
• Vertebrates – Fish, Amphibians, Reptiles, Birds and
Mammals
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Naming
Species
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EVOLUTION
is
Gradual Change
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How did Life
Originate?
Or
Chemical Evolution
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Biological
Evolution
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Evolutionary Bush
One life-form splits into two
and those branches split
(independently) to make
more.

Phenotypic
‘distance’
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Evolutionary Bush -thousands of earlier and
later branches.
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At any given moment (e.g. the
‘present’), all we see is current
diversity…
all extinct forms are gone (99.9%)
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Charles Darwin
• 1809-1882
• British naturalist
• Proposed the idea
of evolution by
natural selection
• Collected clear
evidence to
support his ideas
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Darwin’s finches
• 13 species of finches in the Galápagos
Islands
• Was puzzling since only 1 species of this
bird on the mainland of South America,
600 miles to the east, where they had all
presumably originated
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Darwin’s finches
• Differences in beaks
– associated with eating different foods
– adaptations to the foods available on their home
islands
• Darwin concluded that when the original
South American finches reached the islands,
they adapted to available food in different
environments
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What did Darwin say?
• Organisms reproduce more than the
environment can support
– some offspring survive
– some offspring don’t survive
– competition
• for food
• for mates
• for nesting spots
• to get away
from predators
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Survival of the fittest
• Who is the fittest?
–traits fit the environment
–the environment can change,
so who is fit can change
Peppered moth
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Adaptive Radiation
• When one species splits into many
species to fill open habitats.
– Darwin’s finches
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Speciation
• One species can evolve into two or
more species
• 2 step process
– Geographical isolation
– Reproductive isolation
When a group becomes
geographically isolated over time
it will become reproductively
isolated = new species formed.
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Ammospermophilus spp
Geographic isolation
•When a population becomes divided by a natural barrier.
•Mountains, river, body of water, landslides
•Groups can’t interbreed or intermix
•Become adapted to a different environment
Harris’s antelope
squirrel inhabits the
canyon’s south rim
(L). Just a few miles
away on the north
rim (R) lives the
closely related
white-tailed
antelope squirrel
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Reproductive Isolation
• Differences in isolated groups become so
great, they can no longer interbreed
– Physical changes
– Behavioral changes
– Biochemical changes
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Stephen Jay Gould (1941-2002)
• Harvard paleontologist &
evolutionary biologist
– punctuated equilibrium
– prolific author
• popularized evolutionary thought
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Punctuated Equilibrium
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Speciation
Evolution of new species
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Four causes of evolutionary
change:
1. Mutation: fundamental origin of all genetic
(DNA) change.
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Four causes of evolutionary
change:
1. Mutation: fundamental genetic shifts.
2. Genetic Drift: isolated populations accumulate
different mutations over time.
In a continuous
population, genetic
novelty can spread
locally.
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Four causes of evolutionary
change:
But in discontinuous
populations, gene
flow is blocked.
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Four causes of evolutionary change
1. Mutation: fundamental genetic shifts.
2. Genetic Drift: isolation  accumulate
mutations
3. Founder Effect: sampling bias during
immigration. When a new population is
formed, its genetic composition depends
largely on the gene frequencies within the
group of first settlers.
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Founder Effect.--
Human example: your tribe had to
live near the Bering land bridge…
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Founder Effect.--
…to invade & settle the ‘New World’!
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Four causes of evolutionary change:
1. Mutation: fundamental genetic shifts.
2. Genetic Drift: isolation  accumulation of
mutations
3. Founder Effect: immigrant sampling bias.
4. Natural Selection: differential
reproduction of individuals in the same
population based on genetic differences
among them.
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Four causes of evolutionary
change:
1. Mutation: fundamental genetic shifts.
2. Genetic Drift: isolation  accumulation of
mutations
3. Founder Effect: immigrant sampling bias.
4. Natural Selection: reproductive race
These 4 interact synergistically
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Modes of
Natural
Selection
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Modes of Action
• Natural selection has three modes of action:
1. Stabilizing selection
2. Directional selection
3. Diversifying selection
Number
of
Individuals
Small
Large
Size of individuals
1. Stabilizing Selection
Acts upon extremes and favors
the intermediate
Number
of
Individuals
Small
Large
Size of individuals
2. Directional Selection
Favors variants of one extreme
Number
of
Individuals
Small
Large
Size of individuals
3. Diversifying Selection
Favors variants of opposite
extremes
Number
of
Individuals
Small
Large
Size of individuals
Evidence of
Evolution
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1. Biogeography:
Geographical distribution of species
2. Fossil Record:
Fossils and the order in
which they appear in layers of
sedimentary rock (strongest
evidence)
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Half-life for a given radioisotope is the time for half the
radioactive nuclei in any sample to undergo
radioactive decay
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3. Taxonomy:
Classification of life forms.
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Mammal Family
Tree
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4. Homologous Structures:
Structures that
are similar
because of
common
ancestry
Turtle
Alligator
Bird
(comparative
anatomy)
Typical primitive
fish
Mammals
5. Comparative Embryology:
Study of
structures
that appear
during
embryonic
development
6. Molecular Biology:
DNA and proteins (amino acids)
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Bibliography
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Miller 11th Edition
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Biology, 2003, Prentice Hall
http://www.nearctica.com/ecology/habitats/island.htm
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