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Transcript
Evolution
Charles Darwin
At age 22 traveled around the world on
the ship called H.M.S Beagle. 1831-1836
Galapagos Islands
• Off the coast of South America
• Found many species never seen before
• Darwin wanted to know why these
species were only found on these
islands
Finches
• Finches had
different beak
shapes on the
different islands.
• Beak shape was a
result of the
different seeds on
the islands
Tortoises
Ideas that shaped Darwin’s
thinking
1. Lyell and Hutton:
• Geologists
• Proved that the features of Earth took
millions of years to form
Shows that Earth
is extremely old
Ideas that shaped Darwin’s
thinking
2. Lamarck:
• Biologist
• Inheritance of acquired traits Wrong
• 1st to come with an idea about how
animals change
Ideas that shaped Darwin’s
thinking
3. Malthus:
• Economist
• Predicted that population size will
outnumber available resources
• Individuals will have to compete b/c
there is not enough for everyone
Putting the ideas together
Charles Darwin and Alfred Wallace
formed a theory to explain how
evolution may take place.
Darwin publishes:
On the Origin of Species
by Means of Natural
Selection
Darwin’s description of evolution:
Descent with modification:
-All organisms (species) had
descended from one form of life
-little changes occur over time
Example
Finches from the Galapagos:
Descent with modification is
accomplished through the process of
natural selection
Process of natural selection as
presented by Darwin
1. Overproduction:
Each species produces more
individuals than can survive to
maturity
Process of natural selection as
presented by Darwin
2. Struggle for survival:
Individuals compete for resources and
with predators
Process of natural selection as
presented by Darwin
3. Genetic variation:
Individuals in a population are all
different
Process of natural selection as
presented by Darwin
4. Differential reproduction:
Some individuals have better genes
and can compete better and produce
more offspring
• Adaptations
animal survive
Live longer
-traits that help an
more offs
Example of natural selection
Just because you want it doesn’t
mean your gonna get it
Homework
Pick one of the following animals and describe
(in words or a drawing) how that animal could
have evolved through natural selection.
Elephant
Leaf bug
Bellwork
How would Lamarck and Darwin
explain how an elephant got its long
trunk?
Evidence for
Evolution
1. Fossils
The ancient remains of
animals and
plants
1. Fossils
• Fossils show that different types of
organisms appeared at different times
and places
• Show extinct species
• Shows earlier forms of modern
organisms
Dating fossils
Rock strata
2. Transitional species
Organisms that
have features of
modern organisms
and extinct
species
3. Biogeography
Organisms with similar traits that
evolved in different regions
4. Anatomy
a. Homologous structures
4. Anatomy
b. Analogous structures
• Similar function but not structure
• Independent evolution
Homologous
Analogous
4. Anatomy
c. Vestigial organs
5. Embryology
6. Biological molecules
All organisms have the same genetic code
DNA
RNA
Protein
Same amino acids
Population
Genetics
Population genetics
Study of evolution from a genetic point
of view.
Microevolution- changes in
genetics of a population.
Population- organisms of the same
species that live in the same area
Species- organisms that are able to
breed and produce fertile offspring.
Individuals in a population vary in
observable traits
Causes of Variation
1. mutations
a random change in DNA that can be passed
from parents to offspring.
2. Recombination
reshuffling of genes during meiosis
3. Random pairing of gametes
each organism produces large number of
gametes. Which gametes combine is pure
chance
4. Polygenic traits
variation in one trait
Gene Pool
• Describes the total
genetic information
available in a
population.
• Knowing the available
alleles you can predict
the genotypes and
phenotypes.
Genetic Equilibrium
Hardy-Weinberg- showed that allele
frequencies in a population tend to
remain the same from generation to
generation unless acted on by outside
influences.
Hardy-Weinberg Equilibrium
P2 + 2PQ + Q2= 1
No Evolution When:
1.No mutations
2.No immigration or emigration
3.The population is large
4.Individuals mate randomly
5.Natural selection does not occur
Disruption of genetic equilibrium
When genetic equilibrium is
disrupted and allele
frequencies change then
evolution will occur
1. Mutations
Can create totally new alleles
3 Types:
a. harmful
b. neutral
c. beneficial
2. Gene Flow
The process of genes moving from one
population to another.
Immigration- movement into a population
Emigration- movement out of a population
2. Gene Flow
Movement of seeds by
air, water, insects
Male animals
leave one group
at adulthood
to another
group
3. Genetic Drift
Change in allele frequency due to
random change.
Most obvious in small populations
2 types
3. Genetic Drift
Founder Affect- small group leaves a
larger population
Amish Founder Affect
3. Genetic Drift
Bottleneck effect- a large number of
individuals are removed or killed
from the population
Over Hunting:
Northern Elephant Seal
Discussion Question
How can the founder affect and
bottleneck affect harm a population?
4. Nonrandom Mating
• Mating based on location
-inbreeding
• Mating with individuals with similar
traits
-assortative
mating
• Sexual selection
5. Natural Selection
Population
Can Evolve Through
Mutation Gene Nonrandom Genetic Natural
Flow
Mating
Drift Selection
Timber wolf
Canis lupus
Husky
Canis lupus familiaris
Arctic fox
Vulpes lagopus
Bull dog
How many species are shown below?
Brassica oleracea.
broccoli
Brussels
sprouts
cauliflower
cabbage
“mutant” flowers:
“mutant”
buds:
“mutant”
leaves:
How many species are shown below?
Panthera onca
Jaguar
Neofelis nebulosa
Clouded leopard
Panthera pardus
Leopard
Cheetah
Acinonyx jubat
SPECIATION
Speciation
Existing species are changed versions
of older species.
Speciation- the process of species
formation
Species
• Morphologically similar
• Can interbreed to produce fertile
offspring
Speciation begins with the isolation of
a formally interbreeding population
2 important ways of isolation:
Physically
Biologically
Geographic Isolation
Allopatric
-physical separation
-gene flow stops
-natural selection and genetic drift
change the populations
Examples of geographic isolation
Reproductive Isolation
Sympatric
-Organisms are unable to breed and
produce fertile offspring
Populations breed at different time
periods.
Different mating rituals.