Transcript Evolution IS

Evolution
Introduction
Science vs. non-science
Common Misconceptions
Definition of evolution
Let’s eliminate
the Non-Science
Evolution
& Science
vs. Non-Science
•
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Who?
What?
When?
Where?
Why?
How?
• Is there a force (God) governing
evolutionary processes?
• What is evolution?…factual (evidence)
• When has evolution occurred?
…factual (evidence)
• Where has evolution occurred?
…factual (evidence)
• What is the motivation behind evolution
(if it is governed by God)?
• How can biodiversity be explained by
evolution?
...evolutionary theory
The differences between the two can
be accounted for in the approach;
life’s diversity is one topic viewed
from two different perspectives.
What is evolution?
Evolution is NOT:
• the idea that people are descended from
monkeys
• “EVILution” / science vs. religion
• an idea created by Charles Darwin
– Darwin contributed the theory of natural selection as a
model for HOW evolution takes place
• an organism gaining a trait and passing it on
to its offspring
– Logic and genetics refute this position
Evolution IS:
• any change in traits
• within a group of organisms
• over multiple generations
• which has been confirmed
by biological studies
Science is not asking IF evolution happened, or IF
it is happening.
Science is searching for evidence to support an
evolutionary picture of biodiversity.
Evolution Unit Overview
I. History of Evolutionary Theory
II. Evidence Supporting Evolutionary
Theory
III. History of Life
IV. Patterns in Evolution
I. History of Evolutionary Theory
Ch 10.1-10.3, Ch. 12
A. Earlier published scientists (all in 1700s):
− Linnaeus: grouped organisms according
to similarities
− Georges Louis Leclerc de Buffon:
species shared ancestors; rejected idea
of 6000 yr-old Earth
− Erasmus Darwin: all from common
ancestor; more complex arises from
less complex
B. Hutton (mid-late 1700s) & Lyell (early
1800s):
− An ancient, slowly changing Earth
− Earth is millions of years old
− the processes that changed Earth in the
past are the same processes that operate
in the present
Darwin’s conclusion from Hutton/Lyell: :
(mid 1800s)
If the earth could change, then so could
the life which depends on the earth.
Life changes in response to a changing
environment.
Such a change, however, would take
many years (that’s why the earth’s age
is significant).
C. Lamarck’s (1809)Theory of Evolution:
– By selective use or disuse of organs,
organisms either acquired or lost
certain traits during their lifetime.
– Acquired traits would then be passed
on to the next generation
– e.g.—fiddler crab,
giraffe, duck
Lamarck’s Theory of Evolution:
Inheritance of Acquired Characteristics
Darwin’s conclusion from Lamarck: (mid
1800s)
Organisms can pass only inherited traits.
For example, in artificial selection,
humans can select the most beneficial
traits (selective breeding)
There are differences in populations
across time and even across
geographic regions.
…but how?
D. Malthus (early 1800)
Population Growth:
If the human population continued to
grow unchecked, sooner or later there
would be insufficient space and food
for all
Darwin’s conclusion: (mid 1800s)
Other animals and plants reproduce in
greater numbers than humans; their
populations were not overrunning the
world
There must be factors that determine
whether or not organisms survive and
or reproduce
Hutton & Lyell:
Lamarck:
Early scientists:
Malthus:
Darwin
Hutton & Lyell:
ancient
earth
Lamarck:
acquired
traits
Early scientists:
past vs.
present
organisms
Malthus:
population
growth
Darwin
Natural Selection
E. Darwin’s Case
Ideas in Darwin’s book, On the Origin of
Species:
1.
Variation in populations is a major
feature of life
−
new traits are the result of
spontaneous mutations
−
the variation must already be present
before the population experiences a
challenge
−
natural selection acts on existing
variation
2.
Large numbers in a population are
trimmed by competition for
resources (overproduction)
−there is a struggle for existence
based on the natural competition
within a population
−as in artificial selection, “good”
traits are passed to the next
generation
−difference: nature selects the
survivors… survival of the fittest
3.
Variations that favor reproductive
potential will be passed to future
(adaptation)
generations
−
Reproducing or Surviving = passing on
the traits that made the survivors
successful
−
Fitness: how well-suited an organism is
to compete in its environment
•
Birds select beetles animation
4.
Favorable variations can be inherited
(descent with modification)
– over time, the characteristics in a
population change in response to
a changing environment
– species today have different traits
than past organisms (…because
they lived under different
circumstances)
– Implication: living things are
related to each other (a single
‘family tree’ of life)
Peppered Moth
Example of an organism affected by
Natural Selection
Prior to 1848, was the
dominant species of moth
Typica species
By 1895, 98% of the
moths were this
species
Carbonaria species
An example of natural selection
Evolution in Resistance
Explanation of how resistance happens:
http://www.sumanasinc.com/scienceinfocus/sif_antibiotic
s.html
Explanation of how bacteria transmit resistance:
http://survivalrivals.org/the-x-bacteria/animation
Video about antibiotic resistance:
http://www.youtube.com/watch?v=W-WumllRPLI
Evolution in Resistance Summary
• Bacteria possess a natural immunity to
some antibiotics.
• The immune ones survive and
reproduce.
• The successive generations possess
increasing percentages of the
immunity.
• New drugs push the selective pressure
toward more resistant bacteria.
Relate Adaptations to Changes in
Organisms
Apply the concept of natural selection
to the following new terms (see
adaptation tables).
•Define the terms (first column)
•Relate these traits to (a) increased
survival OR (b) reproductive success
(second column)
II. Evidence Supporting Evolutionary Theory
Ch. 10.4-10.5
A. Fossils
• types of fossils found in certain
rock layers but not others
• fossil organisms in older layers
of rock are more primitive
B. Geography
• Birds on Galapagos were
similar—but not identical—to
those on South American
continent
• Darwin hypothesized that
island species originated from
a common ancestor that
migrated from the mainland
C. Embryology
D. Anatomy
Homologous and Analogous
Structures
Analogous Structures - structures
that can be explained by a
shared way of life
• functional
requirement
Ex. Wings – bats, birds, and
insects
Ex. Body shape of sharks,
dolphins and whales
Analogous structures:
• Look similar on the OUTSIDE
• Do not look similar on the
inside
• Are not evidence of common
ancestry
• Could be evidence of similar
selective pressures in the
environment
Homologous Structures - structures
that are similar in origin but not
necessarily similar in function
Ex. limbs of various animals
Turtle
Alligator
Bird
Typical primitive fish
Mammals
Ex. 5 digit
limbs of
various
animals
Homologous structures:
• Do not necessarily look similar
on the OUTSIDE
• Do look similar on the inside
• Are evidence of common
ancestry
• Could be evidence of
DIFFERENT selective pressures
in the environment
Vestigial Structures
• structures that are present but are
not always used
Ex: whales and snakes have
pelvic girdles but have no
hind limbs
Ex. Human appendix
What would it take for the appendix
to evolve completely out of the
human population?
E. Molecular Data
DNA sequence Analysis &
Protein Comparisons
III. History of Life
Ch. 12
Spontaneous Generation: the idea
that living things can
spontaneously exist from
non-living matter
Redi’s Experiment on Spontaneous
Generation
OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.
HYPOTHESIS: Flies produce maggots.
PROCEDURE
Uncovered jars
Controlled Variables:
jars, type of meat,
location, temperature,
time
Covered jars
Several
days pass
Manipulated Variables:
gauze covering that
keeps flies away from
meat
Responding Variable:
whether maggots
Maggots appear
No maggots appear
appear
CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous
generation of maggots did not occur.
Spallanzani’s Experiment
Gravy is boiled.
Flask is
open.
Gravy is teeming
with
microorganisms.
Gravy is boiled.
Flask is
sealed.
Gravy is free of
microorganisms.
Pasteur’s Experiment
Broth is boiled.
Broth is free of
microorganisms
for a year.
Curved neck
is removed.
Broth is
teeming with
microorganisms.
Conclusions from the experiments
of Redi, Spallanzani, and Pasteur:
• Life gives rise to life
• There are living things that
cannot be readily seen, but are
present
• The theory of spontaneous
generation is not supported with
data
Current Theories on the
Origins of Life
General Theory of Progression
1.Nothing -> presence of matter
2.Non-Living matter-> Living things
3.Simple Life-> More Complex Life
4.Radiation of Multicellular Life
2. Primordial Soup Model
• developed by A. I. Oparian –
Russian chemist in 1920
• a theory that states
there was an ocean
filled with primitive
chemicals
• these primitive chemicals were
the ancestor of amino acids
(which are the monomers of
proteins)
• chemist Stanley Miller and
physicist Harold Urey did a
famous experiment in 1950 to
test this theory.
They mixed gases thought to be
present on primitive earth:
Methane (CH4)
Ammonia (NH3)
Water (H2O)
Hydrogen (H2)
No Oxygen
They then electrically sparked the
mixture to signify lightning. The
results were amino acids, the
building blocks of proteins.
• it was later discovered that other
energies also can excite gases
and produce all 20 amino acids
• considered the classic
experiment on the origin of life
3. Endosymbiosis - mutualistic
relationship between one
organism and other that lives
within it
Endosymbiotic Theory:
• The presence of eukaryotes is
because of a primitive
relationship between aerobic and
anaerobic prokaryotes
Endosymbiotic Theory
• Lynn Margulis Explains Endosymbiotic
Theory
• the aerobic prokaryote (inside)
evolved into what is now the
mitochondrion
• This combined cell would have
been the ancestor to the modern
eukaryotic cell
• the chloroplast followed
a similar evolutionary
route to yield in time a
primitive plant-like cell
Mitochondrial DNA as evidence:
• could have been independent
organisms at one time
• DNA replicates independently
from the cell cycle
• DNA is circular in
shape (as in
prokaryotes)
• contains some of its own, unique
genes –different than the rest of
the cell’s genes
4. Radiation of Multicellular Life
Multicellular life appeared in
the Paleozoic Era (544 mya)
First part: Cambrian
Explosion— a huge diversity of
animals species evolved
Life moved from water to land
Mass extinctions were followed by
booms in numbers and varieties
of plants and animals
Appearance of the Hominid Species
Members of the family of humans
Lucy
• Australopithecus
afarensis
• found in 1971 in Africa
• 40% complete skeleton
• 3.5 feet tall
• between 3 - 3.6 million years old
• many propose that she is the
“missing link”
• puzzle has not yet been solved
• First appearance of genus Homo
was 100,000 yrs ago
Phylogeny
Phylogenetic tree – family tree that
shows evolutionary
relationships that are thought to
exist among organisms
—provides a snapshot of
evolutionary history
• based on embryological
development, chromosomal
similarity and biochemical
similarities
Cladistics – type of phylogenetic
classification that establishes
evolutionary relationships by
looking at derived characters
derived characters – features that
evolved only within the
group being examined
Ex: feathers on birds
• the more features in common,
the closer the organisms are in
evolutionary history
Cladogram
IV. Patterns in Evolution
Ch. 11
How Quickly Do Organisms Evolve?
Rate of evolution – statistical
measurement of the changes of
an evolutionary lineage over
time
Gradualism
Punctuated equilibrium
High number of transitional species
Low number of transitional species
Two types of Evolution:
1. Microevolution – small-scale
changes in gene
frequencies in a population
over a few generations
• microevolution could be caused by:
a. mutation,
b. natural selection,
c. artificial selection,
d. gene flow, and/or
e. genetic drift
• microevolution results in changes
in the phenotypic ratios within a
population over time
a. Mutation – a change in DNA
Causes: random error, radiation, etc.
b. Natural selection – the process by
which organisms with
favorable variations
reproduce at higher rates
than those without such
variations
c. Artificial selection – breeding of
individuals by humans to
produce certain phenotypic
characteristics
Ex. all domestic
dogs are
Canis
familiaris
d. Gene flow – the movement of
genes into or out of a
population
e. Genetic drift – a shift in allele
frequencies in a population
due to chance;
Usually an environmental
change
Generic Bell Curve for
Polygenic Trait
Frequency of Phenotype
For a polygenic trait in a population,
characteristics are exhibited with a bellshaped curve: few members on the
extremes and a bulk of individuals with the
intermediate trait.
Phenotype (height)
e. Genetic Drift
In isolated samples of an original
population…
Sample of
Original Population
Founding
Population A
Founding
Population B
Descendants
e. Genetic Drift
…individuals that carry a certain
allele may have more descendants.
Over
time, thisFounding
can resultDescendants
in…
Sample of
Original Population
Population A
Founding
Population B
e. Genetic Drift
…the divergence of phenotypes in
the future generations.
Sample of
Original Population
Founding
Population A
Founding
Population B
Descendants
This resulted from chance isolation
of individuals from the original
population.
Summary: Genetic drift—there is a
“random” change in the frequency
of alleles in a population
Example of microevolution: bacteria
that are resistant to antibiotics
• observable, so accepted
• does not give rise to new
species
2. Macroevolution – major
evolutionary changes over
very long periods of time
The creation of new types of
organisms from previously existing,
but different, ancestral types
• eventually gives rise to new
species
• not as accepted as microevolution
because not easily observed
during the typical life span of
humans
Patterns of Evolution
Organism populations must adapt to
changing environment in order to
survive
1. Coevolution – the change of two
or more species in close
association with each other
a. predators and prey
b. parasites and hosts
c. Plants and the animals that
pollinate them
Ex. fruit bats are able to detect
light colored flowers and
fruity smells at night and
pollinate the fruit in return
2. Convergent Evolution – occurs
when the environment
selects similar phenotypes,
even when the ancestral
types are not similar
Ex. Porpoises are mammals and
sharks are fishes, but both
have streamlined bodies and
similar fin structure
3. Divergent Evolution – when two
or more populations or
species become more and
more dissimilar
• usually a response to differing
habitats
• may result in new species
Red fox
(farmlands and forests)
Kit fox
(desert)
4. Adaptive radiation – many related
species evolve from a single
ancestral species,
producing a variety of
characteristics
Ex. finches of the
Galapagos
Generic Bell Curve for
Polygenic Trait
Frequency of Phenotype
Remember the graph…?
Phenotype (height)
5. Other patterns of selection
a. Stabilizing Selection
Stabilizing Selection
Key
Low mortality,
high fitness
High mortality,
low fitness
Selection
against both
extremes keep
curve narrow
and in same
place.
What good
reasons can you
come up with for
this trend?
Human babies that have
a really low birth
weight…
Human babies that have
a really high birth
weight…
Birth Weight
–In stabilizing selection, the bulk
portion of the bell-shaped curve is
favored;
–The average phenotype is favored
b. Directional Selection
Key
Directional Selection
Food becomes scarce.
Low mortality,
high fitness
High mortality,
low fitness
–In directional selection, the one
side of the bell-shaped curve is
favored;
–The one extreme phenotype is
favored over the other, over the
average
c. Disruptive Selection
Disruptive Selection
Low mortality,
high fitness
High mortality,
low fitness
Population splits
into two
subgroups
specializing in
different seeds.
Beak Size
Number of Birds
in Population
Key
Number of Birds
in Population
Largest and smallest seeds become more common.
Beak Size
–In disruptive selection, both end
portions of the bell-shaped curve
are favored;
–Both extreme phenotypes are
favored over the average
Another example to demonstrate these
selection patterns:
http://bcs.whfreeman.com/thelifewire/
content/chp23/2302001.html
d. sexual selection
–In sexual selection, an
‘attractive’ mate is favored
Evolution vs. Genetic Equilibrium
• These are opposites!
• Maintaining genetic equilibrium requires:
– Random mating
– Population must be very large
– No movement of individuals in or out of a
population
– No mutations
– No natural selection
• Is it possible to meet all of these criteria at once?
• If you can’t maintain g.e., then what is
happening?