What is evolution?• Evolution basically means change.• Several definitions:

1. The process by which different kinds of living organisms are thought to have developed and diversified.

2. The development of new types of organisms from preexisting types.

3. A heritable change in the characteristics within a population from one generation to the next.

Are there different types?• Microevolution- changes in the gene

pool of a population over time which result in relatively small changes to the organisms in the population

• Macroevolution- changes in organisms which are significant enough that, over time, the newer organisms would be considered an entirely new species.

What is a theory?• A conclusion that draws observations,

hypothesis, inferences and laws together to make sense of them

• a well-supported explanation for some aspect of the natural world that incorporates many observations, inferences, and tested hypothesis.– Examples: Cell Theory, Theory of Gravity or Germ

Theory

• Theories are constantly challenged and amended –

Journal Entry

• Tell me what you know…

1. What is a theory?2. What is evolution?

• Write some ideas about both questions.

Chapter 15Theory of Evolution

Evolution

• All the changes that have formed life on earth from its earliest beginnings to the diversity that characterizes today.

• The heritable changes in the characteristics within a population from one generation to the next.

Microevolution vs. Macroevolution

• Microevolution: changes within a subspecies or gene pool of a species.– Small scale changes; studies changes in

populations over a few generations. – These changes may be due to several

processes: mutation, natural selection, artificial selection, gene flow, and genetic drift.

Microevolution vs. Macroevolution

• Macroevolution: Large-scale changes over geological era/time. – a scale of analysis of evolution in

separated gene pools.– Studies evolution ranging from thousands

to millions of years ago.

Geology in the 1800’s

George Cuvier (1769-1875) French Anatomist

Catastrophism-

sudden geologic catastrophes caused the extinction of large groups of animals at certain points in the past.

Geology in the 1800’s

• Charles Lyell (1797-1875) • English Geologist

• UniformitarianismGeologic processes have changed the shape

of the earth’s surface in the past and continue to work in the same ways today

Jean Lamarck• French Scientist (1744-1829)• Proposed that similar species

descended from a common ancestor• To explain how species changed he

hypothesized that acquired traits (not inherited) could be passed on to offspring –

Jean Lamarck

• His hypothesis was fiercely attacked and easily disproved

• But, he was the first to clearly state that types of organisms changed over time and that similar types of organisms are modified descendents of older types.

Charles Darwin

An English Naturalist (1809-1882)• He proposed the hypothesis that

species were modified by natural selection

Darwin

Charles Darwin

• From 1831-1836 he was a naturalist on board the H.M.S. Beagle for a 5 year mapping and collecting expedition to South America and the South Pacific.

• While on board the ship he collected 100’s of specimens and fossils and kept careful records of his observations.

• When he returned he analyzed his data over a period of 20 years and finally published his work on evolution by natural selection.

• He wrote a famous book which was published in 1859 called “On the Origin of Species”

Darwin’s Theories

1. Descent with Modification - states that the newer forms appearing in the fossil record are actually the modified descendents of older species.

(Describes the process of evolution)

Darwin’s Theories2. Theory of Natural Selection -Describes the mechanism or how evolution occurs. It has five important parts:

a) All organisms produce more offspring than can survive. “Overproduction”

b) All organisms within a species vary. “Genetic Variation”

c) Every organism faces a constant struggle to survive.

d) Organisms best suited for their environment survive.

“Survival of the Fittest”e) Organisms that survive pass

their traits onto their offspring.Differential Reproduction

Darwin’s Theories

• **The resulting change in the genetic makeup of a population is Evolution.

• **In an evolving population, a single organism’s genetic contribution to the next generation is termed Fitness.

Who is more likely to survive?

A

B

Favorable Traits• The environment “selects” the traits that will

increase a population. The kinds of traits that are favorable depend on the demands of the environment. A favorable trait is known as an adaptation or it gives an organism an adaptive advantage.

Write this in the margin• Adaptation: A favorable trait that helps an

organism survive.

Steven Jay Gould

• American Paleontologist and Evolutionary Biologist (1941-2002)

• He developed the theory called “Punctuated Equilibrium” where evolutionary change occurs suddenly and rapidly followed by longer periods of evolutionary stability.

Who was Charles Darwin?

Shoulder partners - A answer, B restate and add to the answer

• Charles Darwin was _________

Why was Charles Darwin revolutionary?

Face partners - B answer, A restate and add to the answer

• Charles Darwin was considered revolutionary because____________

What was Charles Darwin’s contribution?

Using your notes, discuss this at your table and write out one answer to share.

• The contribution that Charles Darwin made was ______________

Evidence to support Evolution• Any evidence of life from the past• FOSSILS

– A trace of a long-dead organism (most are hard parts such as bones, teeth, shells, and woody stems.)

Where are fossils found?

1. Sedimentary rock layers (strata)

(Grand Canyon, AZ)

2. Frozen in Ice (wooly mammoth)

3. Stuck in tree sap or Amber (insects)

4. Stuck in Tar (Saber Toothed Tigers)

Fossils are not always body parts but:

• Imprints - a film of carbon remains after an organism decays

• Mold - an imprint or impression in a rock of the shape or track of an organism

• Cast - when sediments or hard minerals fill in a cavity left by a fossil mold

• Replacement - when sediments or hard minerals replace the whole organism.ex. petrified wood

Scientists Who Study Fossils…

The Age of Fossils• Relative Age - the fossil’s age

compared or related to another fossil. (because a fossil was found in a rock layer below another fossil, we could say it is older.)

• Absolute Age - can be estimated from the amount of sediment deposited above the fossil. (numerical age)

Radioactive Dating

• The age of fossils can be determined by measuring the amount of a particular isotope it contains. This quantity is then compared with the amount of some other substance in the fossil that remains constant over time.

• Carbon 14 -------------> Carbon 12

The Geologic Time Scale

A time scale for the history of the Earth

Geologic Time Scale– Precambrian

• 4.5 bya-600 mya

– Paleozoic • 600 mya- 225 mya

– Mesozoic • 225 mya-2.5 mya

– Cenozoic• 2.5mya– present

The Fossil Record• Fossil-bearing strata show that

species of organisms appear, existed for awhile, and then disappear or became extinct

• The fossil record indicates that there were several mass extinctions, which are brief periods during which large numbers of species disappearede.g trilobites disappeared during the Permian extinction 245 million years ago.

Evidence for Evolution by Natural Selection

1. Common Ancestry

Some species have evolved

from one common ancestorEx. finches and tortoises

Eastern long neck turtle and desert turtle

COSMOS Episode 2 clip

2. Homologous Structures-

Structures that are embryologically and structurally similar, but have different functions

( SAME STRUCTURE, DIFFERENT FUNCTION)

ex. human arm and bat wing

3. Analogous Structures-

Structures that are similar in their function, but have very different embryological development and different anatomy or structures.

(DIFFERENT STRUCTURE, SAME FUNCTION)

ex. Wings

Insect wings and bird wing

4. Vestigial Structures-

Organs or structures that have no use any more

ex. human tailbone, whale pelvic bone

5. Embryological Similarities-

Similarities in embryos can be considered evidence of common ancestry

6. Similarities in Macromolecules-RNA, DNA, and

proteins (amino acid sequence) from different species are very similar.

Patterns of Evolution

1. Coevolution- the changes of two or more species in close association with each other

ex. Predators and their preyParasites and their hostHerbivores and plants Plants and animals that Pollinate (flower and bee)

Patterns of Evolution

2. Convergent Evolution - unrelated species become more and more similar as they adapt to the same kind of envirnoment.

ex. sharks and dolphins

Patterns of Evolution

3. Divergent Evolution- two or more related populations or species become more and more dissimilar; usually occurs as a response to differing habitats.

Divergent Evolution

a. Adaptive Radiation- many related species evolve from a single ancestral species. (finches – common ancestory)

b. Artificial Selection- breeding of organisms by humans. (dogs)

Industrial Melanism

• During the 1850’s in England there was a species of moth during the time of the industrial revolution – dark moths became more common