Transcript Evolution - Greeley Schools

Theories on the Origin of Life
• Spontaneous generation is the theory that life can come from
non-living matter. (Frogs come from mud, flies come from
garbage, etc.)
– Disproved by Redi (1600) – covered materials don’t produce flies.
– Spontaneous generation of microbes was disproved by
Louis Pasteur (1860)
• Heterotroph Hypothesis–life arose
• from a combination of inorganic chemicals methane (CH4)
ammonia (NH3) + water (H2O) that existed in the ancient oceans of earth.
• Miller and Urey experiment (1953) formed amino acids
• Fox – amino acids will form proteins at high temperatures
• Problem – no CELLS have ever been produced in a lab!
Theories of Evolution
• Evolution – slow, gradual change over time.
• Geologic evolution – changes in the non-living planet
over time.
• Biological evolution – changes in living organisms over
time.
Jean Baptiste LaMarck 1809
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Early Theory of Evolution
– (gradual changes in species over time)
Use and Disuse – He hypothesized that organisms
were able to develop new structures as they needed
them and they were able to pass them on to their
offspring. This was called the..
Theory of Inheritance of Acquired Traits
Got evolution right, but got mechanism wrong !!
Inherited Traits – characteristics genetically passed
on the offspring.
Acquired Characteristics – a trait that develops
during an individual’s lifetime.
Charles Darwin
• 1809-1882
• Ships naturalist aboard the HMS Beagle
collected hundreds of specimens and made
extremely detailed observations of the
natural world on the 5 year scientific
expedition. Upon his return and further study
of geology and natural population increase,
he developed his
Theory of Natural Selection
• Wrote (1845) his famous book
“On the Origin of Species”
Darwin’s Theory of Natural
Selection
• #1 Overproduction
• Organisms tend to have many more than two
offspring so at least some will survive (yet
populations usually do not grow rapidly in the
wild)
#2 Competition - Therefore they
must compete for resources
(food, space, mates)
Natural Selection
• #3 Variation - variation
within the population.
• #4 Adaptation Therefore some of them
must be better adapted
to their environment
• #5. Natural Selection- the ability of
organisms that are best adapted to
survive and reproduce . Those that are
less well adapted will not survive.
Speciation
• Eventually, over generations and time,
new species will evolve from older forms
by natural selection of better adapted
forms.
Fitness
Evidence for Evolution
All of the fields of Life Science show evidence of evolution.
• A. The Fossil Record
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Fossil: the remains or evidence of past life recorded in rock.
(molds, impressions, bones, shells, teeth, preserved in ice, etc.)
1. Fossils are found most often sedimentary rock.
2. Relative age can be determined by the fossils position in the
layers. The oldest fossils are found below the younger ones.
– 3. Absolute dating uses the principal of radioactive dating
• The half-life of known radioactive compounds never changes.
• (ex. Carbon 14 found in bones and shells can determine their
actual age in years).
• Ex. Fossil remains clearly show the gradual evolution of the modern
horse.
Fossil Record
B. Comparison of Similar Anatomy
or Structures
1. Homologous structures - those that appear to have
come from a common ancestor. These indicate that
species are related.
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Ex. Bats wing, human arm and whale flipper bones.
2. Analogous structures - those that are used for the
same function but are not similar. These indicate
species are not related.
3. Vestigial structures – those that no longer serve a
useful function
•
Ex. Human appendix, tailbone (coccyx)
Bones of the Mammalian Forelimb
Comparative Anatomy
Comparative Embryology
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Comparative
Embryology –
examination of
differences and
similarities in
embryo
development
(before birth).
•
ex. Comparison of
bird, fish and early
human embryos
E. Behavior Comparisons
F.•
Biochemical Comparisons
Recent developments (Human Genome Project) have
allowed for the comparison of DNA from different
species and groups within species. This new
evidence is the strongest yet that consistently
supports accepted evolutionary theory.
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DNA - our DNA and that of a Chimpanzee is more than 99%
identical. Gorillas and Baboons have somewhat less (9597%) and mice have 80% identical DNA.
Protein and Enzymes
Ex. Cytochrome C, a respiratory enzyme common to all
animals is slightly different in different species. Humans differ
from monkeys by one amino acid in their cyt C. We differ from
pigs by 10 amino acids. Chicken cyt C has 13 different amino
acids and fish differ by 21. This clearly shows the accepted
evolutionary relationship between vertebrates.
Molecular Comparisons
Sources of Variation
• A. Mutation
• A mutation is a change in the DNA of an
organism due to external or internal
factors. (toxins, radiation, random,etc.)
• Most mutations are NOT beneficial to the
organism.
• Some may become beneficial if the
environment changes, provided they do
not harm the individual. (ex. Giraffe’s
neck)
Genetic Recombination
• Sexual reproduction leads
to new combinations of
genes. Genetic shuffling
• Ex. You are not exactly like
either one of your parents.
Genetic Drift = random changes in allele frequencies in
a small population (pg 400)
Gene Flow = genes from one population move to
another population.
Genetic Drift Lab
http://www.biology.arizona.edu/evolution/act/drift/drift.html
Founder’s effect
Bottleneck Effect = genetic drift that happens when
a sudden and severe decrease in population size
results in an extreme reduction in the gene pool.
Selection for polygenic traits
Three ways Natural Selection can effect
phenotypes
• Directional selection
• Stabilizing selection
• Disruptive selection
Directional selection
• Directional selection is
a type of natural selection
that favors one extreme
phenotype over the mean
or other extreme. This
phenomena is usually
seen in environments that
have changed over time.
Changes in weather,
climate, or food
availability lead to
directional selection.
Stablizing Selection
• Stabilizing selection is a type
of natural selection that favors
the average individuals in a
population. This process
selects against the extreme
phenotypes and instead favors
the majority of the population
that is well adapted to the
environment. Stabilizing
selection is often shown on a
graph as a modified bell curve
that is narrower and taller than
the norm.
Disruptive selection
• is a type of natural
selectionthat selects
against the average
individual in a population.
The make up of this type
of population would show
phenotypes of both
extremes, but have very
few individuals in the
middle. Disruptive
selection is the rarest of
the three types of natural
selection
Summary of selection
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C. Speciation
New species will arise more quickly if they are
geographically isolated. Natural barriers such as
mountains, deserts, rivers or landslides can separate
members of a population. If they can no longer
interbreed they may change enough by natural
selection to become a separate species.
(ex. Darwin’s finches)
The loss of the ability to interbreed is called
reproductive isolation. Sometimes this is caused by
changes in reproductive organs such that the offspring
will not survive.
Sometimes this type of isolation is caused by changes
in courtship behavior or the timing of mating cycles.
Speciation
• Geographic isolation of populations
• Can lead to
• Reproductive isolation of population
• Can lead to
• Temporal Isolation of populations
Can lead to
New Species
(unable to breed when together)
Geographic Isolation
• Members
of a
population
may
become
isolated
from one
another by
geographic
boundaries
like
mountains,
rivers or
even
oceans
Reproductive Isolation
Adaptive Radiation
New Species Evolve
EVOLUTION OCCURS IN 2
WAYS…
Gradualism
Gradually over long
periods of time.
emc.maricopa.edu
lhs.lps.org
EVOLUTION OCCURS IN 2
WAYS…
Punctuated Equilibrium
In spurts of changes.
lhs.lps.org
crocomania.com
V. Evolutionary Time Frames
A. Gradualism: species descend from a common
ancestor gradually as the change in minor ways
over a long period of time.
B. Punctuated Equilibrium a newer theory
developed by Stephen Jay Gould states that
species remain fairly constant over long periods
of time until a great change in their environment
cause relatively rapid speciation.
Gradualism
• Seen often in
the fossil
record of
marine
invertebrates
like snails.
Punctuated Equilibrium
• Seen in the
evolution of
birds from
dinosaurs
Gradualism
Convergent Evolution
Divergent Evolution
(Adaptive Radiation)
• Evolution is a fact – species do
change over time!!
• Natural Selection is a scientifically
supported theory that explains this fact.
• Decades of experimental and observational
evidence support Darwin’s theory of
Evolution by Natural Selection
EXTINCTION…= the end of a species.
• Environmental changes
occur too fast for the
species to adapt.
• Over 99% of all species
that have lived on Earth
are now extinct.
listsoplenty.com
Bill Nye Evolution: From 24:00 minutes.
http://player.discoveryeducation.com/index.cfm?guidAssetId=AFA8F02E-A881-468E-BA47EBDDFB3A6264&blnFromSearch=1&productcode=US
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