Download Evolution Class Notes

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Unit Learning Goals
a. Trace the history of the theory.
b. Explain the history of life in terms of
biodiversity, ancestry, and the rates of
evolution.
d. Relate
natural
selection to
changes in
organisms.
Cosmos:
Some things
that
Molecules
do
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Age of Earth
Where do I live?
• What type of
environment am I
best “fit” for?
– Hot/cold????
– Wet/dry???
• Why
• Organisms have
traits (GENES) that
help them to
survive in different
environments.
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A variation is a small change in a trait that makes
an individual slightly different from other members
of its species.
• All organisms in a
population are not
the same.
Variation/diversity
exist.
• What causes this
variation??
What is Fitness?
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• Fitness is a measure of
reproductive success.
(survive long enough to
reproduce)
• Reproductive success:
Having traits so that an
organism is able to pass on
genes onto the next
generation (and in a way so
that the next generation can
also pass those genes on)
• Any trait that promotes
survival — at least until one's
reproductive years are over
increases fitness.
• Such traits are called
adaptations.
—
What if an organism has a trait. 6
that makes it impossible to live in
its environment?
• The organism will
not survive.
• If it does not
survive—it
CANNOT
reproduce.
• If it does not
reproduce—its
genes are not
passed to the next
generation.
What if the environment changes? 7
• If they do not have the traits (genes)
that enable them to survive…they die,
and DO NOT reproduce.
• If they do have the traits, then they
survive…and reproduce.
– SO… the next generation has more of the
“fit” traits for THAT environment.
• The population then CHANGES!
– This is a very slow process….does not occur
over night…many generations must past before
any change in the population can be seen.
Natural Selection
Current Theory …
Natural Selection
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•Also know as “survival of the fittest.”
•Only certain members of the
population will survive and reproduce.
•Ones that survive are most suited to
the environment—they are the most
fit!!.
survival of the fittest
Humans have been doing this for 1000s of years!
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Dog Breeds
Corn
Pigs
Humans select and breed for certain traits.
Examples: The largest hog, the cow that gives
the most milk, fastest horse, or cutest dog.
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Where do NEW
traits come
from?
How do new traits arise?
a) Mutations.
b) Sexual Reproduction.
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– Mixing of genes makes new
combinations
– A combo of traits may be necessary
for survival……so… sexual
reproduction and crossing over can
create new combination of traits.
Decent with modifications
These changes increase
a species’ fitness in their
environment.
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THE BASICS: A review
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• ADAPTATIONS (traits) that are
favorable become more prevalent
within that population.
• These traits will be passed on to the
next generation.
• The GENE POOL of a population
CHANGES in favor of the “FITTEST”
phenotype & genotype!!!
nvironment selecting “good” traits for THAT environme
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Example: Peppered Moth
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Sampling the birds that died as well
as those that survived showed that
•the larger birds were favored
over the smaller ones
•those with larger beaks were
favored over those with smaller ones.
Beak length
(mm)
Beak depth
(mm)
Dead birds
10.68
9.42
Survivors
11.07
9.96
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of Small beaks
From 1976 through 1977, a severe drought struck an island in the Galapagos.
Some phenotypes are more fit than others when it comes to
competing for resources. The more “FIT” phenotype will
survive and have the possibility of passing its alleles to the
next generation.
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Review Clip
History
• James Hutton -1785-Proposed
that the Earth is millions of years
old.
• Many land formations took millions
of years to form.
• Known as the founder of modern
geology.
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History
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• Thomas Malthus -1798• Proposed that populations outgrew
their food supplies, causing
competition between organisms and a
struggle for one species to survive against
another
• This "struggle for existence" drives
population change.
History
Jean-Baptiste Lamark
-1809• Believed that all life
forms evolved and that
the driving force of
evolution was the
inheritance of acquired
characteristics.
• He believed that
organisms changed due
to the demands of their
environment.
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What we
understand
now:
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•Charles Lyell -1830-proposed
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that plant and animal species had
arisen, developed variations, and
then became extinct over time.
•He believed that every animal or
plant, including humankind, was
the present is the key to
adapted to the niche in which it
understanding the past
was created.
•He also believed that
the Earth’s physical
landscape changed over
a long period of time.
15.1
• Alfred Russel Wallace -
1858
• Emphasis was based on the
idea of competition for
resources as the main force
in natural selection.
Best known for independently
proposing a theory of natural
selection which prompted Charles
Darwin to publish on his own theory
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• Charles Darwin -1859-
Publishes “On the Origin of
Species”
• Believed that Natural Selection
is the driving force for
evolution.
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Charles Darwin
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Summary of Darwin’s Ideas
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1. Individual organisms differ, and
some of this variation is heritable.
2. Organisms produce more offspring than can
survive, and many that do survive do not
reproduce.
3. Because more organisms are produced than
can survive, they compete for limited
resources.
4. Individuals best suited to their environment
survive and reproduce most successfully.
Summary of Darwin’s Ideas
5. These organisms pass their heritable
traits to their offspring. Other
individuals die or leave fewer offspring.
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6. This process of natural selection causes
species to change over time.
7. Species alive today are descended with
modification from ancestral species that lived
in the distant past.
8. This process, by which diverse species evolved
from common ancestors, unites all organisms
on Earth into a single tree of life.
Review Clip
Review Clip: 10min
Whale Video Clip- Intro to
evidence ( Questions in packet)
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Evidence for Change Over Time
Fossil Record
– Fossils that show
how the same
organism looked
millions of years
ago.
– Paleontology
– Use rock layers
– 1) Isotope dating
Clip
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Fossil Record
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2) Relative Dating
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Homologous structures
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Homologous structures
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Analogous versus Homologous Structures
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Vestigial organs
– Organs or
structures that
do not seem to
be used by the
organism any
longer.
– They are
usually reduced
in size.
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Vestigial Organs
c
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•Things
that
cause
change.
•Why we
are all a
little bit
different
…
Genetic Comparison
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• The numbers
represent the
number of amino
acid differences
between the beta
chain of humans and
the hemoglobins of
the other species.
• In general, the
number is inversely
proportional to the
closeness of kinship.
GEOGRAPHIC DISTRIBUTION
• Organisms that are related change/adapt
according to their environment.
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Adaptive Radiation
• The evolution of many
diversely adapted species
from a common ancestor
– Relatively rapid
• Usually occurs when a
population colonizes an area of
diverse geographic or
ecological conditions.
– New niches
Each species
becomes
specialized for
a different set
of conditions
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Macroevolution
Speciation
How do we get new species?
Where do new species come
from?
Species: population whose members can interbreed in
nature and produce viable, fertile offspring
Evolution: change in the allelic
frequencies in a population
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Speciation
In the physical world, natural barriers form
and cause the breakup of populations to form
smaller populations.
Volcanoes, sea-level changes, and
earthquakes are a few examples of natural
occurrences that affect populations
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Speciation Mechanisms
• Geographic Isolation
– Separated by bodies of water or mountains.
• Temporal Isolation
– Reproduction takes place at different times of the year
– Different Mating seasons
•Overtime they can change so much that they
become unable to breed as they adapt to their
environment.
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•Behavioral Isolation
–Populations are capable of interbreeding, but have
different courtship rituals or other type of behavior.
–Do not recognizes another species as a mating partner.
–Sexual Selection
–Brightly colored male- drab female
– video clip: Dressing fro desire
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VOCAB CHECK
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•A population is a localized
group of individuals that belong
to the same species.
Genetic drift— along with natural selection, mutation, and
migration—is one of the basic mechanisms of evolution. 57
Changes in allele frequency with in a population
Gene Flow
• Immigration
• Emigration
Start Packet #2
• Review Clip
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Divergent Evolution
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Divergent Evolution
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Two or more related species becoming more and
more dissimilar
Convergent Evolution
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Independent
development of similar
structures
Convergent Evolution
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Independent
development of similar
structures
Coevolution
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Coevolution
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Bumblebees & the flowers they
pollinate have coevolved so that
both have become dependent on
each other for survival.
• Some Central American Acacia species have hollow thorns and pores at
the bases of their leaves that secrete nectar. These hollow thorns are
the exclusive nest-site of some species of ant that drink the nectar. But
the ants are not just taking advantage of the plant—they also defend
their acacia plant against herbivores.
Evolution at the species level is
called microevolution.
It results from genetic variation
and natural selection within a
population of organisms.
Small Changes
Macroevolution is evolution that
occurs between different
species.
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Evolution is the
change in a
species over
time.
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Rates of Evolution
Gradualism & Punctuated Equilibrium
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• Two ways in
which the
evolution of a
species can
occur.
• A species can
evolve by
only one of
these, or by
both.
•Species with a shorter evolution evolved mostly by
punctuated equilibrium, and those with a longer
evolution evolved mostly by gradualism.
Gradualism
•Very gradually, over a long
time... Over a short period
of time it is hard to notice.
•Slow Changes
•Small variations that fit an
organism slightly better to
its environment are selected
for: a few more individuals
with more of the helpful
trait survive, and a few
more with less of the
helpful trait die.
•Change is slow, constant,
and consistent.
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Punctuated equilibrium
•change comes in spurts. There
is a period of very little change,
and then one or a few huge
changes occur, often through
mutations in the genes of a few
individuals.
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• STOP HERE>>>>>>>>>>>>>
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Biological Resistance
• When organisms are no longer
affected by a drug.
• First documented around 1952
• Causes: Natural consequence
of selective pressures in the
environment.
Resistance in Bacteria
Read page p403.
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• Bacteria- Antibiotic
resistance
• Many insects have
developed a
resistance to
insecticides. (simple
point mutations)
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The Effects
of Selection
on
Populations
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Types of Selective Processes in Natural Selection
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•
•
•
Stabilizing Selection
Directional Selection
Diversifying Selection
Balancing Selection
–Heterozygote Advantage
–Frequency-dependent
Stabilizing Selection
 Intermediate forms of a
trait are favored and
alleles that specify
extreme forms are
eliminated from a pop.
 Ex: Human birth weight
stay between 6-8 lbs.
Lower or higher has
higher mortality.
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Directional
Selection
 Changing environmental conditions give rise to
directional selection, where one phenotype
replaces another in the gene pool.
 Can produce rapid shift in allelic frequencies.
 Ex: Peppered moth
– peppered moths, pesticide resistance,
antibiotic resistance
Occur in response to:
* directional change in the environment
* one or more new environmental conditions
* a mutation that appears and proves to be adaptive
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Diversifying
 Increases the
extreme types in
a population at
the expense of
the intermediate
forms.
 One population
divided into two.
(bill size in seedcrackers)
(Disruptive)
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Selection
• Diversifying selection can result in balanced
polymorphism.
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• For example, two distinct bill types are present in
black-bellied seedcrackers in which larger-billed
birds are more efficient when feeding on hard seeds
and smaller-billed birds are more efficient when
feeding on soft seeds.
Heterozygote Advantage
• Exists when a heterozygote
(Aa) has a higher fitness than
either homozygote (AA, aa).
• ex: Sickle Cell
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Frequency dependent
• The term given to an evolutionary
process where the fitness of a
phenotype is dependent on its
frequency
• Can arise in systems of mimicry
– ex: Butterflies
• ex: Maintenance of a 50:50 sex ratio:
If one sex becomes more common,
some of its members will not be able
to mate
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• Adaptation is a key concept
in natural selection.
• Natural selection can change
the inherited characteristics in
a population and possibly
even result in a new species.
Two main sources of genetic
variation
1.Mutations
2.Genetic Shuffling (by sexual
reproduction)
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EOCT-
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It is important that you are able to
explain how the concepts of genetics provide the basis
for explaining natural selection and evolution. This will
help you answer questions like this:
What is the end result of natural
selection?
A increased number of offspring of a given
phenotype that survive
B changes in the frequency of alleles in a
population
C fossil formation through extinction
D environmental changes of a habitat
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Although the Arctic fox and the kit fox are closely related,
they look very different because the individuals
A acquired traits during their lifetimes that contributed to
survival
B with traits most suited to their environments reproduced most
successfully
C migrated long distances to environments that most suited
their traits
D passed on to their offspring acquired behaviors that were
helpful
Fossils of Archeopteryx show that this animal had feathers, like 91
a
bird. It also had a bony tail, teeth, and claws on its
wings,
like a reptile. This fossil is evidence that supports the idea that
A. birds and reptiles have a common ancestor
B. birds have changed very little over 150 million
years
C. reptile species are more advanced than bird
species
D. reptiles are warm-blooded like birds
Horses and tapirs have a common ancestor, but now look
very different. Horses now are grassland animals adapted for
grazing on grass and shrubs. Tapirs are jungle animals that
live in dense forests and eat fruit, leaves and aquatic
vegetation. Which of the following led to the development of
such differences in the two species?
A selective breeding
B convergent evolution
C DNA hybridization
D natural selection
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Adaptation is the key
concept in natural
selection.
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