Transcript Evolution - Effingham County Schools

Evolution
Evolution
Evolution- change in
population over time
Evolution- Darwin
Darwin
 father of modern
evolutionary theory
 Galapagos Islands
 HMS Beagle
Scientists who
influenced Darwin
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Lamarck- organisms
change due to the
pressures of their
environment, traits are
acquired
He proposed that by
using or not using its
body parts, an
individual tends to
develop certain
characteristics, which
it passes on to its
offspring.
Scientists who influenced
Darwin- Lamarck
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Example:
A giraffe acquired its long neck because its
ancestor stretched higher and higher into the
trees to reach leaves, and that the animal’s
increasingly lengthened neck was passed on to
its offspring.
Scientists who influenced
Darwin
Lyell
 Principles of Geology
 plant and animal
species emerged,
developed variations
and then became
extinct
Scientists who influenced
Darwin
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Malthus- populations outgrew their
food supplies causing competition
Essay on the
Principle of
Population (1798)
Natural Selection
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Natural Selectionorganisms with
traits best suited to
the environment
have a higher
survival rate,
“descent with
modification”
Natural Selection
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1. organisms produce more offspring
than can survive
2. variation (differences) exist in all
populations
3. organisms best suited to environments
will have more offspring
4. over time organisms with certain
advantageous variations make up most of
the population
Natural Selection

Example: Peppered Moths during the
Industrial Revolution
Natural Selection
Fitness- reproductive efficiency of
various individuals or genotypes in a
population
 depends on probability that one
individual will contribute its genetic
information to the next generation
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Natural
Selection
Extinction- permanent
loss of a species
5 mass extinctions
throughout history
 Permian period96% of marine
invertebrates
 Cretaceous period60-75% of marine
species
Evidence for Evolution
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Fossils
Comparative anatomy
Comparative embryology
Biochemistry
Genetic evidence
Direct evidence
Evidence for
Evolution
1. Fossils
 mold or cast
of organism left
in rock, fossilized
bone and teeth
 life becomes
more complex
over time
 record is
incomplete
Evidence for
Evolution
 Most
complete
fossil record is
for the horse
Evidence for
Evolution
Relative dating layers in rock
bed used to
date organisms
Evidence for Evolution
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Radioisotope dating- uses half-life of
isotope to approximate age of organism
Carbon is
used
frequently
Evidence for Evolution
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Half-life
Evidence for Evolution
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phylogenydescription of the
lines of descent of
plants and
animals as they
lived from one
to the next
Evidence for Evolution
2. Comparative Anatomy- the study of the
structures of different organisms
homologous parts modified structures among
different groups of descendants
Evidence for Evolution
Comparative Anatomy
Evidence for Evolution
Comparative Anatomy
analogous partsstructures in
organisms that
have no common
origin but serve
the same function
 Example: bird’s
wing, bat’s wing
and insect’s wing
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Evidence for Evolution
Comparative Anatomy
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vestigial organs- organs having no
functions in the living organism
Vestigial toes in the horse
Vestigial pelvis and femur in whales
Evidence for Evolution
3. Comparative Embryology
the study of developing plants and
animals
Below is the pictures of embryos for a fish, human,
rabbit, tortoise, and chicken. Can you guess
which one is each type of organism?
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2
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4
5
Evidence for Evolution
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Comparative Embryology
Here the pictures of the second set of
development is added. Can you tell now?
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5
Evidence for Evolution
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How about now?
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2
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5
Evidence for Evolution
Comparative Embryology- The complete picture
Evidence for Evolution
4. Biochemistry
 comparison of DNA and proteins in
the body
 Example: comparison of
hemoglobin (blood protein) in
human, chimp, and dog. Human
and chimp hemoglobin more alike
than dog
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Evidence for Evolution
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5. Genetic Evidence
Mutations- mistakes in the genetic code
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Causes changes in populations over time
Population genetics- researchers use
mathematical descriptions of genetic
make ups to help them trace evolutionary
trends within populations
Selective Breeding- humans choose
plants/animals with most desirable traits
and breed them to pass those traits to
offspring
Evidence for Evolution
Biodiversity
 Ecosystem diversity- variety of habitats,
living communities and ecological
processes in the living world
 Species diversity- different organisms on
Earth
 Genetic diversity- different forms of
genetic information carried by all living
things on Earth
 Example Myosin- protein in muscle cells
causing contractions. Also found in yeast
cells- used to move cell parts
Evidence for Evolution
6. Direct Evidence
 Rapid Evolution
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Strains of bacteria becoming resistant
to antibiotics
 Weeds and herbicides
 Insects and pesticide
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Adaptations
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Adaptation- change in a species that
makes it better suited to its
hump to store nutrition during
environment Along
trips or when food or water
Fur inside the ears to
protect inner ear from
sand
Nostrils that close to
keep sand out
Calluses on the the knees
to protect from abrasion
is scarce
Long eyelashes to
protect their eyes
from the sand when
the wind is blowing
Large feet for
standing in the
sand
Types of Adaptations
Structural
 Changes in structure or anatomy
 Example: bird’s beak or claws
 Mimicry- a harmless species
resembles a harmful one, predators
learn to avoid both species
 Camouflage- species features blend
in with the environment
Mimicry
Camouflage
Types of
Adaptations
Physiological
 Changes in chemical
makeup
 Examples:
digestion enzymes,
snake venom,
octopus ink
Types of Adaptations
Behavioral
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Responses to the environment
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Example: bird migration
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Mechanisms for Evolution
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Species- group of organisms that
can interbreed AND produce viable
offspring
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Populations evolve NOT individuals
Origin of a
Species
Common
Misperception:
 Individuals
Evolve
Species evolve
NOT individuals
“And now there go the Wilsons!... Seems
Like everyone’s evolving except us!”
Mechanisms for Evolution
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Gene pool- all the alleles for a trait in the
population
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Over time gene pools shift to traits that are
best suited to the environment
Allelic frequency- the percent of any
specific gene in a population
Genetic Equilibrium- when the percentage
of alleles in a population remains stable
over time
How does evolution occur?
1. mutation- change in genetic code
 caused by environmental factors like
radiation/chemicals or by chance
 2. genetic drift- allelic frequency
changes by chance, usually in small
populations
 3. movement of individuals in and
out of populations
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Genetic Drift
Natural Selection acts on
variation in a population
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1. stabilizing – favors average individual
2. directional – favors one extreme variation
3. disruptive – favors both extremes of variation
4. diversifying- two or more phenotypes develop,
different selective pressures operate at the same
time
5. heterozygote advantage- heterozygote (Aa)
has higher fitness than either homozygote (AA
or aa)
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Example- sickle cell anemia
Natural Selection acts on
variation in a population
Diversifying Selection
Heterozygote Advantage
In sickle cell anemia, heterozygous
individual has normal and sickle cells
 May be an advantage to surviving
malaria
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Normal (AA)- gets malaria
and dies
Heterozygous (Aa)- survives
malaria
Sickle cell homozygous (aa)die from sickle cell
Origin of a
Species
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Speciation –
formation of a
new species,
members of
similar
populations no
longer
interbreed
Origin of a Species
1. Geographic Isolation
 Physical barrier divides population
 River, canyon, mtn. splits group
Two species of
squirrel split by
the Grand
Canyon
Origin of a Species
2. Reproductive Isolation
 Members in a population can no
longer interbreed
 Caused by
seasonal,
mechanical,
and
behavioral
differences
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Origin of a
Species
3. Polyploidy
 Mistakes during
mitosis or
meiosis results
in individuals
with multiple
chromosomes
Is speciation fast or slow?
Two hypotheses
Punctuated
Equilibrium
– in rapid bursts
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Gradualism - slowly ov
time
Patterns in Evolution
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Adaptive radiation – one ancestral species evolves
into a number of species to exploit a number of
habitats.
Patterns in Evolution
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Divergent evolution- one species
evolves into two species with
different characteristics (get more
and more different from each other)
Patterns in Evolution
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Convergent evolution – distant or
unrelated species evolve similar
characteristics to take advantage of
similar environments Example:
fish and dolphin