Transcript Evolution 4

Other Evidence for Evolution
• Comparative Anatomy
– Examining differences and similarities in
structures
– Homologous structures – same structure,
different purpose
– Analogous Structures – different structures,
same purpose
– Vestigial Structures – non functioning
structures that probably had a function in
the past.
Homologous Structures
Related organisms will share similarities
that are derived from common ancestors.
Similar characteristics due to relatedness
are known as homologies.
Compare the bones
But don’t be fooled by these…
– look similar
• on the outside
– same function
– different structure & development
• on the inside
– different origin
Analogous Structures
The clue to common descent is common structure,
not common function. A bird’s wing and a horse’s
front limb have different functions but similar
structures.
Body parts that share a common function, but not
structure, are called analogous structures. The
wing of a bee and the wing of a bird are analogous
structures.
Convergent evolution
3 groups with wings
– Does this mean they have a
recent common ancestor?
Convergent evolution
The independent
development of similar
structures in organisms that
are not directly related.
Convergent evolution is
usually seen in animals and
plants that live in similar
environments
Convergent Evolution
Convergence among fast-swimming
predators
Divergent evolution describes evolution
toward different traits in closely related
species.
red fox
kit fox
ancestor
Vestigial structures: have no apparent
function, but resemble structures their ancestors
possessed
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Comparative embryology
Development of embryo tells an evolutionary
story
– similar structures during development
all vertebrate embryos have a “gill
pouch” at one stage of development
Molecular record
Comparing DNA & protein structure
– everyone uses the same genetic code!
• DNA
Human
Macaque
Dog Bird
Frog
Lamprey
8
32 45
67
125
 compare common genes
 compare common proteins
number of amino acids different
from human hemoglobin
0 10 20 30 40 50 60 70 80 90 100 110 120
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DNA evidence
Another important line of evidence for evolution comes
from DNA analysis
Any permanent change in form or function of an organism
must be preceded by a change in its DNA
Organisms which have much of their DNA in common must be
closely related, i.e. they have split from a common ancestor
comparatively recently (in geological terms)
For example, humans and chimpanzees have 99% of their DNA
in common which suggests a close relationship and relatively
‘recent’ divergence from a common ancestor
American Beaver: Lives in North America
Coypu: Lives in South America
Muskrat: Lives in the North and Central America
Capybara: Lives in South America
Geographic Distribution of Organisms
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Darwin noticed that organisms in different
regions of the world had similarities in physical
appearance and structure.
As you can see these 4 different species have
similar characteristics such as teeth, limbs, hair,
nose, diet and habitat.
Scientists hypothesize that a common ancestor of
these species settled in different regions and
evolved to suit the different habitats. The result
being the 4 different species seen here.
Building “family” trees
Closely related species are branches on the tree —
coming from a common ancestor
Genetic engineering
Herbicide resistant crops: these resist
weed-killer and are unaffected by it
(allowing only weeds to die, not the
actual crops)
Pest-resistant crops : make a plant lethal
to insect pests.
Manipulating the growth rate of crops : to
produce faster-growing trees for wood.
Improving crop quality : modified
tomatoes ripen more slowly for ease of
transport.
Misconception: “Evolution is a
theory about the origin of life.”
Evolutionary
theory deals
mainly with how
life changed after
its origin.
Misconception: “Evolution is like a climb
up a ladder of progress; organisms are
always getting better.”
It is true that natural selection weeds out
individuals that are unfit in a particular
situation, but for evolution, “good enough”
is good enough. No organism has to be
perfect.
Misconception: “Evolution
means that life changed ‘by
chance.’ ”
• Chance is certainly a factor in evolution,
but there are also non-random
evolutionary mechanisms. Random
mutation is the ultimate source of genetic
variation, however natural selection, the
process by which some variants survive
and others do not, is not random.
What Do You Know About
Evolution?
In a population of antelopes that live on the plains with
a large number of cheetahs (fast predators of
antelopes), which of the following is NOT true:
A. Individual antelopes will develop genes for
speed in order to survive.
B. Those antelope who are faster are likely to
survive better.
C. Those antelope who have the most fertile
offspring would be considered to be
biologically successful.
D. Some antelopes will be killed by cheetahs.
Which of the following concepts is
NOT a part of evolutionary theory:
A. There are limited resources available to
an organism.
B. Organisms will pass on characteristics
that they develop during their lives to
their offspring.
C. Traits are passed on to offspring via
DNA.
D. Inherited traits may change over time in
a population of organisms.
Within a given species:
A. There is often a great deal of variation.
B. Normally only very little variation.
C. There is an individual or several
individuals that we can say are “normal.”
D. Variation is only something that is visible,
not hidden.
The following is a good example
of biological adaptation:
• It’s cold, so you put on a jacket.
• Your puppy stops urinating inside after you
scold it when it does.
• A strain of Stapholococcus bacteria
appears that is not killed by a dose of
antibiotic that normally kills these bacteria.
• As a young man, you believe that females
prefer well-muscled males, so you start
working out.
In evolutionary terms, the “fittest” in
the phrase “survival of the fittest”
means:
A. Those organisms that produce the most
fertile offspring.
B. Strongest.
C. Fastest.
D. Best able to adapt to the environment.
The theory of evolution by natural
selection was developed most
famously by:
A.
B.
C.
D.
Gregor Mendel
Watson and Crick
Charles Darwin
Rosalind Franklin
The picture most clearly shows
evidence for which of the
following?
A. Certain birds choose to
develop particular beak
shapes.
B. No relationship between
function and form.
C. Evolution has probably
occurred among a group
of birds.
D. Survival of the fittest.
Biology teaches all of the following
EXCEPT:
A. Life began billions of years ago.
B. The first life was single celled.
C. Evolution of life has generally progressed
from simple life forms to more complex
ones.
D. Life began with many complex animals
arising at about the same time.
Thousands of years ago, giraffes with short necks
were common within giraffe populations. Nearly all
giraffe populations today have long necks. This
difference could be due to:
A. Giraffes stretching their necks to keep their
heads out of reach of predators.
B. Giraffes stretching their necks so they could
reach higher food in the trees.
C. A mutation in genetic material controlling neck
size in some skin cells of a giraffe.
D. A mutation in genetic material controlling neck
size occurring in the reproductive cells of a
giraffe.
Scientists have concluded that snakes
evolved from ancestors with legs. Which of
the following statements provides best
evidence for this conclusion?
A. Most species of snakes live on land.
B. Snakes move extremely fast to catch prey.
C. Snakes have a well-developed backbone and
muscular system.
D. Some species of snakes have limb buds
during their embryonic development.
Which of the following best explains
how the fossil record provides evidence
that evolution has occurred?
A. It indicates that forms of life existed on Earth at
least 3.5 billion years ago.
B. It indicates the exact cause of structural and
behavioral adaptations of organisms.
C. It shows how the embryos of many different
vertebrate species are very similar.
D. It shows that the form and structure of groups
of organisms have changed over time.
Evolution is:
A. A theory, and therefore not strongly
supported.
B. Not observable or testable.
C. A process that explains patterns that can
be observed in nature.
D. Undoubtedly true.
Evolution produces organisms that:
A. Are better adapted to a particular
environment than the ones they evolved
from.
B. Are physically stronger than the ones
that they evolved from.
C. Are more complex than the ones they
evolved from.
D. More common than the ones they
evolved from.
During the development of humans,
which of the following is true?
A. A new variation in an individual is a sign
of evolution.
B. The same variation spread through a
population is a sign of evolution.
C. Certain individuals, if they have a useful
enough adaptation, can evolve.
D. The first person who was born with blue
eyes can be said to have evolved.
Mutations may:
A. Have positive effects
B. Have negative effects
C. Have no effect
Variation comes about in all of the
following ways EXCEPT:
A. So an organism can be more successful
in its environment.
B. Through shuffling of genes between
organisms
C. Because of mutations
D. Randomly