Download Analogous Structures

What is species?
Species: a group of individuals that look
similar and whose members are capable of
producing fertile offspring in the natural
environment
Tree of Life
These happy face spiders look different, but since
they can _________, they are considered the same
species: Theridion grallator
A.) Dance
B.) Interbreed
C.) Spin a web
D.) Eat bugs
Speciation
A lineage-splitting event that produces two or more
separate species.
Imagine that you are looking at a tip of the tree of life
that constitutes a species of fruit fly.
Move down the phylogeny to where your fruit
fly twig is connected to the rest of the tree.
That branching point, and every other branching
point on the tree, is a speciation event.
At that point genetic changes resulted in two
separate fruit fly lineages, where previously there
had just been one lineage.
How do new species arise?
Would polar bear evolution
create a new species?
Why or why not?
Here is one scenario that exemplifies
how speciation can happen:
The scene: a population of wild fruit flies minding its
own business on several bunches of rotting bananas,
cheerfully laying their eggs in the mushy fruit...
Disaster strikes: A hurricane washes the bananas and
the immature fruit flies they contain out to sea.
The banana bunch eventually washes up on an island
off the coast of the mainland.
The fruit flies mature and emerge from their slimy
nursery onto the lonely island.
At this point, speciation has not occurred — any fruit
flies that got back to the mainland could mate and
produce healthy offspring with the mainland flies.
The populations diverge: Ecological conditions are
slightly different on the island, and the island
population evolves under different selective pressures
and experiences different random events than the
mainland population does. Morphology, food
preferences, and courtship displays change over the
course of many generations of natural selection.
So we meet again: When another storm reintroduces
the island flies to the mainland, they will not readily mate
with the mainland flies since they've evolved different
courtship behaviors. The few that do mate with the
mainland flies, produce inviable eggs because of other
genetic differences between the two populations. The
lineage has split now that genes cannot flow between the
populations.
Differing selection pressures on the two islands can
complete the differentiation of the new species.
EVIDENCE FOR EVOLUTION
Comes from many disciplines!
1.
2.
3.
4.
Fossils
Anatomy
Embryology
Biochemistry
Fossils tell a story…
The Evidence for Evolution
Why is the fossil record
incomplete?
– Only hard parts become
fossilized.
– Not all organisms die in
the right conditions for
fossilization
– Not all fossils have been
discovered
Does this falsify
evolution?!
Whale Evolution
The Fossil Record
• The fossil record may show slow gradual changes
and transitional forms
• It may also show jumps in evolution, either due to
an explosion in life forms or an incomplete fossil
record
We found the fossil
— no joke!
Land Mammal
?
?
?
Complete series
of transitional
fossils
Ocean Mammal
?
Evolution from sea to land
2006 fossil discovery of early tetrapod
4 limbs
Missing link from sea to land animals
Evolution of birds
Today’s organisms
descended from ancestral
species
Fossil of Archaeopteryx
• lived about 150 mya
• links reptiles & birds
claws
wing-like
forelimbs
teeth
thin
ribs
long tail
feathers
Replica of Archaeopteryx fossil;
half bird half reptile
Reptile-like features
Bird-like features
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.
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
30
Adaptation Lab
• Using what you have learned, apply your
knowledge to the lab!
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