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 StructuresRelated 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

Convergence among fast-swimming predators

Convergent Evolution

Divergent evolution describes evolution toward different traits in closely related species.

ancestor

red fox kit fox

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Vestigial structures: have no apparent function, but resemble structures their ancestors possessed

Comparative embryologyDevelopment of embryo tells an evolutionary story

– similar structures during development

all vertebrate embryos have a “gill pouch” at one stage of development all vertebrate embryos have a “gill pouch” at one stage of development

Molecular record

100 20 30 40 50 60 70 80 90 100 110 120

LampreyFrogBirdDogMacaqueHuman

328 45 67 125

Comparing DNA & protein structure– everyone uses the same genetic code!

• DNA

compare common genes compare common proteins

compare common genes compare common proteins

number of amino acids different from human hemoglobinnumber of amino acids different from human hemoglobin

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

DNA evidence20

DNA evidence

Geographic Distribution of Organisms• 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.

American Beaver: Lives in North America

Muskrat: Lives in the North and Central America

Capybara: Lives in South AmericaCoypu: Lives in South America

Building “family” trees

Closely related species are branches on the tree — coming from a common ancestorClosely 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. Gregor Mendel

B. Watson and Crick

C. Charles Darwin

D. 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