Transcript PPT File

Evolution and Darwin
Evolution is surrounded by
controversy
• Why?
• People have religious beliefs
• People don’t like the idea that “Human’s
came from monkeys”
• There is a lot more to evolutionary
theory than monkeys.
The Camps surrounding Evolutionary
Theory
• Creationists- believe a supreme being (God,
Allah, Great Spirit etc.) created everything as
it is today
• Intelligent Design-followers believe the living
world is too complex for it to just happen.
Some intelligent form had to be behind
making the blue prints.
• Evolutionists- believe organisms changed
over time to their present forms.
What do you need to do to be
successful with Unit #4?
• You do not have to believe Evolutionary
Theory.
• You only have to understand its
principals and concepts that we learn in
our future lessons
Old Theories of Evolution
• Jean Baptiste Lamarck (early 1800’s) proposed:
“The inheritance of acquired characteristics”
• 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.
“The Inheritance of Acquired
Characteristics”
• 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.
Would these acquired characteristics
get passed on to their offspring?
Of course not. The acquired characteristics did not
cause changes in the sex cells
Larmarck’s Theory
• Use and Disuse
-Fish in caves don’t use their eyes so
they disappear
-Elephants use their trunks a lot so they
get longer
• Although false, his theory was the first
attempt to explain how organisms
adapted to their environment over time
Charles Darwin
• Influenced by Charles Lyell who published
“Principles of Geology”.
• This publication led Darwin to realize that
natural forces gradually change the Earth’s
surface and that the forces of the past are still
operating in modern times.
Charles Darwin
• Darwin set sail on the H.M.S. Beagle (1831-1836)
to survey the south seas (mainly South America
and the Galapagos Islands) to collect plants and
animals.
• On the Galapagos Islands,
Darwin observed species
that lived nowhere else in
the world.
• These observations led
Darwin to write a book.
HMS Beagle and
its route
California Academy of Sciences in
San Francisco
• I spent the day there on a summer trip to visit
my son and daughter
• The CAS had an incredible Darwin Exhibit
You will use
this chart
for Beaks of
Finches
Lab
Darwin’s Finches
Charles Darwin
• Wrote in 1859:
“On the Origin of Species
by Means of Natural Selection”
• Two main points:
1. Species were not created in their present
form, but evolved from ancestral species.
2. Proposed a mechanism for evolution:
NATURAL SELECTION
Natural Selection
• Individuals with favorable traits are more
likely to leave more offspring better suited for
their environment.
• Also known as “Differential Reproduction”
• Example:
English peppered moth (Biston betularia)
- light and
dark phases
Artificial Selection
• The selective breeding of domesticated
plants and animals by man.
• Selective Breeding is also called
Artificial selection
• Question:
What’s the ancestor of the domesticated dog?
(Canis familiaris)
• Answer: WOLF (Canis lupus)
My dog Clancy
at 6 weeks old
Both of these trees are in my yard and are
the same species (Thuja occidentalis)
Which one looks better? Why?
A
B
They are both in the same
environment (water, sun, nutrients
are the same). Why do they look so
different?
Different Traits in their DNA
Which one do you think humans
selected desirable traits in
deliberate plant crosses?
Darwin is the founder of Modern
Evolutionary Theory
• Science attempts to:
-Describe events based on phenomena we
can observe
-Explain events of the past in terms of
events we can observe today
-Make predictions about future events
• A Theory such as Evolution Theory is
supported by a lot of data collected by
thousands of Scientists
• Theories can be discarded
(i.e.Lamarck) or revised as scientist get
new information
• Theories can’t be proven with absolute
certainty (i.e.-Gravitational Theory, Cell
Theory, Contagious Disease, Genetics)
Darwin is the founder of
Modern Evolutionary Theory
• Evolution is the processes that have
transformed life on earth from it’s earliest
forms to the vast diversity that characterizes
it today.
• Evolution results in
A change in the
genes!!!!!!!!
• Darwin never did claim that
humans originated from
monkeys.
• Darwin claimed that humans and
monkeys (well, apes really) have
a COMMON ancestor. That is,
they originated from the same
species many years ago
• Evolution is the process (mutation,
adaptation, natural selection and
extinction) of change in a population through
generations
• Existing life forms have evolved from earlier
life forms.
• Evolutionary theory is a unifying principle for
the biological sciences. ( Genetics,
Biochemistry, Anatomy, Physiology etc.)
• Evolution Theory provides
an explanation for the
differences/ similarities in
structure, function, and
behavior among life forms.
Evidence of Evolution
Cladograms or
phylogenetic trees are
graphic representations
of species relationships.
Common Ancestor
Evidence of Evolution
1. Geographical distribution of species. Alfred Russell
Wallace was also known as the "father of biogeography.
• Biogeography -the study of the past and present
geographical distribution of organisms.
Reproductive Isolationprevents mating with birds
on the other islands. Two
populations develop
independently
2. Fossil Record:
Fossils and the order in which they appear in
layers of sedimentary rock (strongest evidence).
Younger Fossils
Older Fossils
Evolution of the horse
What changes do you
notice in moving from
the bottom to the top?
Increase in size
Changes in the leg
bones
• Relative Dating-In relative dating, something is
determined to be older or younger than something
else by using the laws of superposition.
-Layers (strata) close to the surface are younger
-Deeper Layers contain the oldest strata
• Absolute Dating-dating determines the actual age
of artifacts
-One of the most widely used
and well-known absolute dating
techniques is carbon-14
dating, which is used to date
organic remains.
Evidence of Evolution
3. Taxonomy-classification of organisms into
different categories based on their physical
characteristics and presumed natural
relationships (remember Did King Philip Come
Over………..?)
• In 1735, Carolus Linnaeus
published a book in which he
outlined his scheme for classifying
organisms and is still in use today
The Linnaean system uses two Latin name
categories, genus and species , to designate
each type of organism.
4. Homologous structures:
Structures that are similar because of
common ancestry (comparative
anatomy)
• Homologous Structures- structures shared
by related species because they have been
inherited from a common ancestor.
(flipper of a whale and hand of a human)
• Analogous Structures- Analogous structures
serve the same function in different species but is
not a result of sharing a common ancestor. (wing
of a butterfly and wing of a bird)
• Vestigial Structures- organ or structure
that once was useful in an animal’s
evolutionary past, but that now is useless
or very close to useless. (wing of an ostrich)
My favorite Vestigial Structures
Snake
Whale
Plica Semilunaris -it is the “crusty” factory. It secretes a sticky
mass that collects any foreign materials. All this trash is
surrounded by the sticky gook so that it does not scratch the
sensitive cornea.
Darwin’s point is found in the majority of mammals, and
humans are no exception. It is most likely used to help focus
sounds in animals, but it no longer has a function in humans.
Wisdom Teeth - Early humans ate a lot of plants – and they
needed to eat them quickly enough and eat a sufficient amount
in one day to get all of the nutrients they needed.
Evidence of Evolution
5. Comparative embryology:
Study of structures that
appear during embryonic
development.
Any ideas on why the
embryos are so similar?
Scientist believe that
mutations at early stages
result in death or
spontaneous abortion.
6. Molecular biology: DNA and proteins
(amino acids)
• Diagram shows chromosome
1 next to the human chromosome 1.
• The A-T bases are black and
the G-C bases white.
Blue areas in the rendered chromosomes identify
bases not known yet.
• DNA Analysis can show us
how closely related different
organisms are.
-There is no thought involved in Natural selection
-There are no choices in Natural Selection
-It is all about the genes an organism is born with
Concepts of Natural Selection
• 1. Overproduction -- Within a population,
more offspring are born than can possibly survive.
These are tadpoles
that hatched from one
female toad. Do you
think many will
survive?
• 2. Competition – Over production results in struggle
for space, water, food, light, mates or other limited
resources
• 3. Variations-Members of populations show
variations (differences in traits) that make certain
individuals better adapted to survive
• 4. Natural Selection-Some variations are more
helpful than others, there is a natural selection
against organisms that can’t adapt.
• 5. Organisms that can’t adapt DIE and
some populations may become extinct
• 6. Survival of the Fittest -- The individuals who
survive are the ones best adapted.
• 7. Inheritance of variations-Organisms with helpful
variations survive and live long enough to
REPRODUCE.
• 8. The best adapted individuals survive and
reproduce, passing on the favorable variations
to their offspring (& population ). These changes
improve the fitness of a species (population) in
its environment
• 9. If an organism does not live long enough to
reproduce it has NO EFFECT ON THE
EVOLUTION OF THE POPULATION.
• 10. Individuals can’t evolve, only populations
can evolve. (make sense because genes have to
be passed on to offspring for evolution to take
place.
• 11. Evolution of New Species-Over long periods of
time, so many variations may accumulate that a
population may become a new species. This
process is called Speciation
Some Sources of Variation in Modern
Natural Selection Theory
• 1. The genetic basis for variation within a species
is provided by mutations and
sexual reproduction. (crossing over
and recombination)
• 2. Mutations are spontaneous
and provide the raw material for
evolution.
Modern Natural Selection Theory
• 1.) All species have the potential to increase in
numbers.
• 2.) There is a finite amount of resources for any
species. Species tend to make too many
organisms for these resources.
• 3.) Species will show genetic variability due to
mutation, crossing over, and genetic recombination
(during fertilization) of genes.
• 4.) The scarce finite resources of the environment
will select those offspring better able to survive and
less fit offspring may die.
• 5.) Variations within a species increases the
likelihood that at least some members of the
species will survive under changed environmental
conditions.
-Traits which are beneficial to the survival of an
organism in a particular environment tend to be retained
and passed on, and therefore, increase in frequency
within a population.
-Traits which have a low survival value to
organisms tend to diminish in frequency from
generation to generation.
-If environmental conditions change, traits that were
formerly associated with a low survival value may, in a
changed environment, have greater survival value and
increase accordingly.
Population Genetics
• The science of genetic change in
population.
• Hardy-Weinberg equation is important
and will be discussed shortly.
Vocabulary
• Population- A localized group of individuals
belonging to the same species.
• Species- A group of populations whose
individuals have the potential to interbreed
and produce viable offspring.
• Gene Pool-The total collection of genes in
a population at any one time.
Hardy-Weinberg Principle
• The concept that the shuffling of genes that
occur during sexual reproduction, by itself,
cannot change the overall genetic makeup
of a population.
Hardy-Weinberg Principle
• This principle will be maintained in nature
only if all five of the following conditions are
met:
1.
2.
3.
4.
5.
Very large population
Isolation from other populations
No net mutations
Random mating
No natural selection
Hardy-Weinberg Principle
• Remember:
If these conditions are met, the population is at
equilibrium.
• This means “No Change” or “No evolution”.
• The Hardy–Weinberg equilibrium is impossible in
nature. Genetic equilibrium is an ideal state that
provides a baseline to measure genetic change
against.
Macroevolution
• The origin of taxonomic groups higher than
the species level.
• Involves very long periods of time
• Grand scale changes in organism
• Scientists can see changes in fossils of
Intermediate species
• Sea cow (manatee)
ancestor with legs
Microevolution
• A change in a population’s gene pool
over a secession of generations.
• Evolutionary changes in species over
relatively brief periods of geological time.
Five Mechanisms of Microevolution
1. Genetic drift:
Change in the gene pool of a small
population due to chance.
• Two examples:
a. Bottleneck effect
b. Founder effect
a. Bottleneck Effect
• Genetic drift (reduction of alleles in a population)
resulting from a disaster that drastically reduces
population size. (result are similar to inbreeding)
• Examples of disasters:
1. Earthquakes
2. Volcano’s
3. Droughts
b. Founder Effect
• Genetic drift resulting from the colonization of
a new location by a small number of individuals.
• Founder populations are
often found on islands
• Results in random change
of the gene pool.
• Mutiny on the Bounty (1789): Population of 9
mutineers, 8-9 Tahitian females and 6 Tahitian
males to uninhabited Pitcairn Island.
Five Mechanisms of Microevolution
2. Gene Flow:
The gain or loss of alleles from a
population by the movement of individuals
or gametes.
–Immigration- movement out/away
–Emigration- movement in
Five Mechanisms of Microevolution
3. Mutation:
Change in an organism’s DNA that
creates a new allele.
4. Non-random mating:
The selection of mates
other than by chance.
5. Natural selection: Differential reproductioncompetition for mates, those best adapted
survive and produce more offspring.
Modes of Action
• Natural selection has three modes of action:
1. Stabilizing selection
2. Directional selection
3. Diversifying selection
Number
of
Individuals
Small
Large
Size of individuals
1. Stabilizing Selection
• Acts upon extremes and favors the
intermediate.
Number
of
Individuals
Small
Large
Size of individuals
2. Directional Selection
• Favors variants of one extreme.
Number
of
Individuals
Small
Large
Size of individuals
3. Diversifying Selection
• Favors variants of opposite extremes.
Number
of
Individuals
Small
Large
Size of individuals
Speciation
• The evolution of new species.
Reproductive Barriers
• Any mechanism that impedes two species
from producing fertile and/or viable hybrid
offspring.
• Different species most likely have different
number of chromosomes
• Two barriers:
1. Pre-zygotic barriers
2. Post-zygotic barriers
1. Pre-zygotic Barriers
a. Temporal isolation:
Breeding occurs at different times for
different species.
b. Habitat isolation:
Species breed in different habitats.
c. Behavioral isolation:
Little or no sexual attraction between
species.
1. Pre-zygotic Barriers
d. Mechanical isolation:
Structural differences prevent gamete
exchange.
e. Gametic isolation:
Gametes die before uniting with gametes
of other species, or gametes fail to unite.
2. Post-zygotic Barriers
a. Hybrid inviability:
Hybrid zygotes fail to develop or fail to
reach sexual maturity.
b. Hybrid sterility:
Hybrid fails to produce functional gametes.
c. Hybrid breakdown:
Offspring of hybrids are weak or infertile.
Chromosome numbers (2n) in some animals
Species
#
Species
#
Guinea Pig[19]
64
Chinese hamster (Cricetulus griseus)[20] 22
Garden snail[21]
54
Earthworm Octodrilus complanatus[22]
36
Tibetan fox
36
Domestic cat[23]
38
Domestic pig
38
Laboratory mouse[20][24]
40
Laboratory rat[24] 42
Rabbit (Oryctolagus cuniculus)[25]
44
Syrian hamster[20] 44
Hares[26][27]
48
Human[28]
46
Gorillas, Chimpanzees[28]
48
Domestic sheep
54
Elephants[29]
56
Cow
60
Donkey
62
Horse
64
Dog[30]
78
Kingfisher[31]
132
Goldfish[32]
100-104 Silkworm[33]
Common fruit fly
8
56
Interesting but not Fertile
Lion- 38
Tiger- 38
The liger is a hybrid cross between a male lionl(Panthera
leo) and a female tiger(Panthera tigris)
The tigon is a cross between a male tiger (Panthera tigris)
and a female lion(Panthera leo),
Horse- 64
Donkey- 62
Mule63
Human ChimpanzeesGorilla-
46
48
48
Allopatric Speciation
• Induced when the ancestral population
becomes separated by a geographical
barrier.
The "Albert" squirrel primarily lives at the
South Rim. They are gray with a reddish
back, fluffy white tails and have tufted
ears.
The Kaibab squirrel looks very similar but
without the reddish back and only live at
the North Rim.
Squirrels at the Thousand Islands
Adaptive Radiation
• Is the emergence of "new" species from
single common ancestor that spreads out to
new environments
Interpretations of Speciation
• Two theories:
1. Gradualist Model- Slow changes in
species overtime.
2. Punctuated Equilibrium:
Evolution occurs in spurts of relatively
rapid change.
Convergent Evolution
• Species from different evolutionary branches
may come to resemble one another if they live in
very similar environments.
• Example:
1. Ostrich (Africa) and Emu (Australia).
2.Sidewinder (Mojave Desert) and
Horned Viper (Middle East Desert)
Coevolution
• Evolutionary change, in which one species act as
a selective force on a second species, inducing
adaptations that in turn act as selective force on the
first species.
• Example:
1. Golden Rod Plant and Parasitoid Wasps
Coevolution
2. Humming birds and plants with flowers
with long tubes
What beak size would you expect in humming
birds if the flowers were longer in length?
POPULATIONS
POPULATIONS
• Population-all of the individuals of a species
that live together in one place at one time.
• Demography-the statistical study of
populations. It is used to predict how the
size of a population will change.
KEY FEATURES OF POPULATIONS
1.
Population size
 is the number of individuals in a population.
 has an important effect on the ability of the population to
survive.
 A small population is more likely to become extinct:
 in the case of random events or natural disaster
 due to inbreeding where the population is more genetically
alike. Recessive traits are more likely to appear.
 with reduced variability it is harder to adapt to changes.
KEY FEATURES OF POPULATIONS,
2. Population density
• the number of individuals in a given
area.
• if males and females are too far apart
(low density)they may only rarely
encounter one another resulting in little
reproduction.
KEY FEATURES OF POPULATIONS,
con’t
Population size is limited by:
density-dependent factors
•
•
•
•
•
•
Disease
Competition
Predators
Parasites
Food
Crowding
– The greater the population,
the greater effect these
factors have.
– Ex. Black plague in the
Middle Ages – more deaths
in cities
Non Living
density-independent
factors
–
–
–
–
–
–
–
Volcanic eruptions
Temperature
Storms
Floods
Drought
Chemical pesticides
Major habitat disruption
(as in the New Orleans
flooding)
• Most are abiotic factors
KEY FEATURES OF POPULATIONS,
con’t
• 3. Dispersion
 the way in which the individuals are located
or arranged.
Most
common
PREDICTING POPULATION GROWTH
• Model:
• A hypothetical population that has key
characteristics of the real population
being studied.
• Used by demographers to predict how a
population will grow.
PREDICTING POPULATION GROWTH,
• Nearly all populations will tend to grow
exponentially as long as there are resources
available.
• Two of the most basic factors that affect the
rate of population growth are the birth rate,
and the death rate.
• r(rate of growth)= birth rate – death rate
PREDICTING POPULATION GROWTH,
• Exponential growth curve:
population growth plotted
against time.
• As a population gets larger, it
also grows at a faster rate.
• This is the maximum
population growth under
ideal circumstances.
• Includes plenty of room for
each member, unlimited
resources (food, water) and
no hindrances (predators).
FACT: No population exhibits this type of growth for long.
PREDICTING POPULATION GROWTH,
• Logistic model: This model accounts for the
declining resources available to populations as
they grow.
• It assumes the birth and death rates are not
constant.
• As the population grows, births decline and
death rises.
• Eventually birth=death so the population stops
growing.
• Carrying capacity (K): The number of
organisms of one species that an environment
can support indefinitely.
Two modes of population growth.
The Exponential curve (also known as a Jcurve) occurs when there is no limit to
population size.
The Logistic curve (also known as an S-curve)
shows the effect of a limiting factor (in this case
the carrying capacity of the environment).
POPULATION GROWTH STRATEGIES
There are 2 ways a population can
prosper:
1. Depends on the rate of growth (r)
2. Influenced by the carrying capacity (K)
POPULATION GROWTH STRATEGIES,
r-strategists: characterized by exponential growth,
which results in temporarily large populations,
followed by sudden crashes in population size. Ex.
Insects, bacteria, some plants
– live in unpredictable and rapidly
changing environments
– Reproduce quickly when
conditions are favorable
– Many offspring: small, mature rapidly,
no parental care
– r = rate of growth
POPULATION GROWTH STRATEGIES,
K-strategists: characterized by a high degree
of specialization. Ex. Trees, whales, tigers,
etc.
– Live in stable and predictable
environments
– Can compete effectively
– Reproduce late in life
– Few offspring: large, mature slowly, often much
parental care
– K = carrying capacity
POPULATION GROWTH STRATEGIES
•
•
•
•
Human Populations:
K- strategist characteristics
Man has learned to expand
the carrying capacity of his
environment by increasing
food supply, combating pests
and curing diseases.
Can Earth support this increase?
Damage to the planet will eventually reduce the
carrying capacity for humanity and slow the growth
of the human population.
How do Humans and other organisms
fight off disease?
How does the body react to these problems?
First lines of defence
saliva
antibacterial
enzymes
skin
prevents
entry
stomach acid
low pH kills
harmful
microbes
tears
antibacterial
enzymes
mucus linings
traps dirt and
microbes
“good” gut
bacteria out
compete bad
Pathogens- any disease-producing agent
(especially a virus or bacterium or other
microorganism)
• Bacteria (prokaryotes-simple cell structure without a
nucleus
• Virus-mostly just DNA Not alive
• fungi,
• protozoa,
• Parasite
Second lines of defence
• Involves white blood cells
• Non-specific response
– invading pathogens are
targeted by macrophages
produced by the division of
monocytes (phagocytes)
• Specific response
– lymphocytes produce chemicals
called antibodies that target
specific pathogens
Phagocytes are the white blood cells that protect the
body by ingesting harmful foreign particles such as
bacteria
Evidence of phagocytosis are
dead white blood cells that we
call pus.
Phagocytosis
• Stages in phagocytosis
1. Phagocyte detects chemicals (antigens)
released by a foreign intruder (e.g. bacteria)
2. Phagocyte moves up the concentration gradient
towards the intruder
3. The phagocyte adheres to the foreign cell and
engulfs it in a vacuole by an infolding of the cell
membrane.
4. Lysosomes (organelles which are rich in
digestive enzymes & found in the phagocytes
cytoplasm) fuse with the vacuole & release
their contents into it.
Phagocytosis
5. The bacterium is digested by the
enzymes, and the breakdown products
are absorbed by the phagocyte.
 During infection, hundreds of phagocytes
are needed.
 Pus is dead bacteria and phagocytes!
Pus
An accumulation of : – dead phagocytes
– destroyed bacteria
– dead cells
Lymphocyte
Lymphocytes
Provide a specific immune response to
infectious diseases.
There are 2 types: - T-cells
- B-cells
They produce antibodies in response to
an antigen (An antigen is a molecule
recognized by the immune system)
Antigens
• all cells have surface
markers called
antigens.
• body can recognise
these as self or nonself (foreign)f
• This comes into play
with pathogens and
organ transplants
Specific response
• Lymphocytes detect presence of
foreign antigens
• Stimulated to produce
specific proteins called
antibodies.
• antibodies combine with their specific
antigen (like a lock and key)
• this renders the pathogen harmless.
• = primary response
Immunity -the bodies ability to resist a
particular infection
• Can be natural or acquired
• We can acquire immunity
to diseases by receiving vaccines
HOW DID LIFE ON EARTH BEGIN?
• Earth’s early atmosphere probably contained
hydrogen, cyanide, carbon dioxide, carbon
monoxide, nitrogen, hydrogen sulfide and Water
• The early earth was much
hotter than it is now
• About 4 billion years ago the
earth cooled enough to allow
solid rocks to form
Origin of Life
• 1.) 3 to 4 billion years ago -- it is thought the first
primitive single-celled life appeared on earth in the
water
• 2.) Heterotroph Hypothesis-proposes that the first
living organisms were heterotrophs and did not make
their own food.
• 3.) These original unicellular organisms added
carbon dioxide to the environment.
• 4.) Some autotrophs evolved a means of using
carbon dioxide to do photosynthesis
• 5.) Autotrophic activity added free oxygen to the
atmosphere.
-Some autotrophs and heterotrophs evolved
mechanisms by which they used this oxygen to
derive their energy. (aerobic respiration)
• 6. About a billion years ago, increasingly complex
multicellular organisms began to evolve.
• 7. The process of evolution took it from there.
• 8. The great diversity of organisms is the result of
billions of years of evolution that has filled available
niches with life-forms.
The Miller–Urey experiment[1
• Was an experiment that simulated
hypothetical conditions thought at the time to
be present on the earth
• Specifically, the experiment tested the
hypothesis that conditions on the primitive
Earth favored chemical reactions that
synthesized organic compounds from
inorganic precursors.
• Considered to be the classic experiment on
the origin of life.
The Miller–Urey experiment[1
• Was conducted in 1952
and five amino acids were
created!!!!!!!!!
(remember AA are the
building blocks of protein
• In 2008, a re-analysis of Miller's archived solutions
from the original experiments showed that 22
amino rather than 5 were actually created in one of
the apparatus used.
• Interesting- Scientists repeat experiments
That is the end of the unit on
evolution
• I truly hope that you have learned a lot about
evolution (species change over time) in the
past few weeks
• Hopefully you have more information stored
on your hard drive than just……
Humans evolved from Monkeys
Some people never open their minds to new
information and let go of incorrect information
• Speciation-creation of new species
• Morphology-study of structure
• Geographic Isolation (Reproductive
Isolation)• Divergent Evolution• Convergent Evolution
• Coevolution• Adaptive Radiation• Genetic Drift-
This powerpoint was kindly donated to
www.worldofteaching.com
http://www.worldofteaching.com is home to over a
thousand powerpoints submitted by teachers. This is a
completely free site and requires no registration. Please
visit and I hope it will help in your teaching.