EVOLUTION

-Theory of Evolution-Evidence for Evolution

Part 1

Theory of Evolution and Selection

Evolution is a Theory

In common usage, people use the word theory to mean a guess. In science, does the word theory mean a guess?

Name some additional theories.

Evolution is a Theory

Name some additional theories:Cell Theory-cell is the basic unit of living thingsQuantum Theory-describes very small particlesGerm Theory- microbes cause diseasePlate Tectonics- continental plates are shiftingHeliocentrism-sun is the center of the universe, which

superseded geocentrism

Theory of Evolution

How has evolution risen in status to the level of THEORY, the same level as gravity or plate tectonics?

Through repeated observations from many areas of life sciences.

Charles Darwin (Slide 1)

Who is Charles Darwin?What was his profession?Where did he travel?What did he learn?

What is his famous idea?

Charles Darwin (2)

Who is Charles Darwin? World renowned Naturalist-before there was Biology. Born Feb 12, 1809, same day as Lincoln. What a day!!!

What was his profession? Ship’s NaturalistWhere did he travel? All over the world. He is

remembered most for his observations in the Galapagos Islands.

What did he learn? That organisms change over long periods of time, evolution.

What idea is he famous for? The Theory of Evolution by Natural Selection

Variation among organisms

Describe how each can vary…Tortoises

Saddle shaped shell for reaching higher vegetation or dome shaped shell if vegetation is more abundant. Also an intermediate form

Bird beaksIn finches, many varieties of beak shape to correspond

to habitat.

Lamarck (1)

Describe John Baptiste-Lamarck

Why is he such an important figure in modern biology?

Lamarck (2)

Describe John Baptiste-LamarckHe was a French naturalist. He published his hypothesis the

year Darwin was born. He proposed the concept of Use and Disuse and Inheritance

of Acquired TraitsWhy is he such an important figure in modern biology?

Although his hypothesis hasn’t been supported by data, his groundbreaking thoughts influenced future naturalists like Darwin. Plus, as we learned in “Ghost in Your Genes”, he was not completely wrong.

Selection

Discuss in your own words what is meant by selection.

Give an example of natural selection.

Give an example of artificial selection.

Darwin’s Theory of Natural Selection1. There is variation among organisms2. More offspring are produced than can survive.3. There is competition for limited resources4. Natural Selection: Individuals best suited for their

environment survive and pass down their traits.Descent with modification

Race to the Finish

Alfred Russell Wallace – Was thinking of the very same ideas at the same time.

When Wallace sent him an essay about his hypothesis, Darwin quickly published the work he had been accumulating for 25 years.

Darwin’s Influences

Hutton– Proposed that the earth is in a constant state of change.

Lyell- Proposed that these changes occur as a result of events such as earthquakes and volcanoes.

Artificial Selection

Give 2 examples of artificial selection…Page 379

Selection Ponderables

Does selection act directly on genotypes or phenotypes? Which is more likely to be selected against, deleterious

mutations that are dominant or those that are recessive? Why? Can selection create perfect organisms?

Human’s backs are evolved from 4-legged ancestors and not fully compatible w upright posture, so many [older or very tall] people have back problems).

Humans have a blind spot that even the octopus doesn’t have. -Blind Spot Test

Part 2

Evidence for Evolution

Early Clues

What is probably the first clue that living things have changed over time?

Fossils

Fossil Evidence

There is a story about the history of life written in rock.

Relative dating--layers of rock (index fossils)

Absolute dating--uses radioactive isotopes (half-life)How can the age of fossils be determined?

Carbon dating—all living things made of carbonCarbon-14 has a half-life of 5730 yearsIf a fossil has ¼ of its original C-14, how old is it?

See page 445 for graph and add’l problem

Piecing the evidence together

What other evidence has contributed to our current understanding?

Geographic Distribution

Island PatternsTortoises and finches from mainland are adapted to fit

their new island environment.Ex: necks and shell in tortoises.

Similar EnvironmentsOrganisms that live in similar environments often come to

have similar adaptations. These are called analogous structures.

Darwinian Prediction

Darwin found an orchid whose reproductive organs were 30 cm deep inside the flower.

Darwin postulated that a pollinator would be found with a 30 cm proboscis.

It took 40 years, guess what scientists found!...

Darwinian Prediction

Xanthopan morganii praedicta– The Hawk Moth

– Guess the length of the proboscis?

– Notice its last name?

– What kind of logic?

• Inductive or deductive?

Anatomical Evidence

Homologous structuresStructures that have different functions but arrived from

same body part.Human arm, bird wing, turtle leg, alligator leg derived

from an ancient, lobed fish (page 384)

Evidence- Homologous Structures

Anatomical Evidence

Embryological DevelopmentDeveloping human embryo displays features from ancestors

• Gill pouches• Tail• 3 sets of kidneys in humans

http://www.pbs.org/wgbh/nova/odyssey/clips/

http://www.exploratorium.edu/exhibits/embryo/embryoflash.html

Which Embryo is Which? Click Link:

Anatomical Evidence

Did you know there are pelvic bones in snakes? In whales? Why?

They are vestigial structures

What vestigial structures do humans have?

Appendix

Analogous Structures

The wing of a bird and the wing of an insect are not homologous. They do not arise from a common structure.

They are analogous structures. They are two structures that have evolved

separately to do the same job. Ex: Bird’s wing; insect’s wing Pouch of kangaroo; pouch of oppossum

Piecing the evidence together

What about our new understanding of genetics? How does this impact our model of evolution?

Molecular Record Evidence

The more amino acid (or DNA base pair) differences, the greater the evolutionary distance.

Cladogram

Cladogram (page 384, page 660) Evolutionary Tree--The ‘trunk’ of the tree represents similar traits or molecules (depending on how

tree was made). Each branch represents a divergence.

See page 452-- CLADOGRAM

What is the common ancestor for the crab, barnacle and the limpit?Which of the above animals are most closely related, according to the cladogram (not the appearance).

Modern Examples

Are there any real life examples of evolution in modern time?

Peppered moth storyBacteria superbugs (MRSA and TB)Human size and developmentResistance to pesticides.

Remember DDT? There are rats in England that no longer even get sick

from 5 times the dose of pesticide that once killed most rats

Industrial Melanism

Peppered moth story See peppered moth simSee details of how the experimental method was

implemented.How does this relate to the Clean Air Act?What types of selection can you attribute this to?

Where did life come from?

First- read pages 424-428 First Organic Molecules Puzzle of Life’s Origin Free Oxygen Origin of Eukaryotic Cells

Origin of Life

Miller-Urey Experiment

Conditions of Early Atmosphere of Earth (Before Life)

Products of Experiment

Origin of Life

Miller-Urey Experiment

Conditions of Early Atmosphere of Earth Before Life

Products of Experiment

Flask with H, methane,

ammonia, H20 (no free

oxygen! O2)Spark (to represent lightning)

Some amino acids, and cytosine and uracil

Miller-Urey Conclusion

What is the main idea of this experiment?

How organic molecules (ex: protein or DNA) might have arisen from simpler molecules

Biogenesis

This is a good time to review Biogenesis.

Compare biogenesis to abiogenesis.

Describe the experiments that proved biogenesis.Redi, Pasteur

Building Complexity

How might cells with organelles have first come about?

What is the evidence that some cell parts arose in this way?

Building Complexity

How might cells with organelles have first come about?

Endosymbiosis-one prokaryotic cell engulfed another, and they remained in this symbiotic relationship.

What is the evidence that some cell parts arose in this way?The membranes, circular chromosomes, ribosomes

and cell division by binary fission of mitochondria and chloroplasts resemble today’s prokaryotes.