Evolution

Do Now: View the finches. What characteristics

do they have in common?

What can you infer from these similarities?

What characteristics are different?

Why do you think they evolved these differences?

Charles Darwin (1809 – 1882) British Naturalist

5 year voyage of HMS Beagle around the world

Credited with the theory of natural selection

Darwin’s Influences Erasmus Darwin

All life was “produced by a simple life filament” Organisms change over time

Jean Baptiste Lamarck Inheritance of acquired characteristics Law of use and disuse Discredited with the discovery of genes

Charles Lyell Principles of Geology – the present is the key to the

past

Thomas Malthus “Essay on the principle of population” Population – a group of individuals that belong to the

same species, live in a defined area, and breed with others in the group

Populations have the potential to increase faster than the available food supply…but this doesn’t occur because of death by disease, war, and famine

Facts About Evolution It is a Scientific Theory (just as Gravity

is) A vast majority of scientists accept it It is supported by a large body of

evidence There is no scientific evidence

contradicting evolution

General Knowledge: Selective Breeding Selective Breeding aka

Artificial Selection Farmers and/or breeders

mate plants or animals with desirable genetic traits to produce offspring with desired traits

Inbreeding Examples:

Dog Breeding Horse Breeding Any domesticated plant or

animal

Darwin’s Observations Found fossils of

extinct armadillos Plants and animals of

Galapagos islands are similar to those in Ecuador

Conclusion: species migrated from S. America to islands and changed after they arrived – “descent with modification”

Darwin’s Theory of Evolution by Natural Selection (1844) Natural Selection:

individuals that posses superior physical or behavioral attributes are more likely to survive, reproduce, and pass on the favorable traits to the offspring1. Overpopulation2. Variation among species3. Competition for resources4. Successful reproduction

Adaptation – the changing of a species in response to its environment

Controversy over evolution Lamarck and other’s ideas of change over time

severely criticized by church and government Alfred Wallace develops same theory (1858) Darwin publishes book in 1859: On the Origin of

Species by Means of Natural Selection People outraged with the idea of being related to

apes Darwin’s theory and evidence (and more recent

evidence) were so compelling they became widely accepted by the scientific community

Darwin’s Ideas have been Updated Microevolution: change occurring within a species over

time Natural Selection causes the frequency of certain genes within

a population to change over time Isolation leads to species formation

Populations of the same species living in different locations tend to evolve in different directions

Isolation – 2 populations of the same species are separated from one another

When individuals of the 2 populations can no longer interbreed, they are considered to be different species

Extinction leads to species replacement Extinct – species permanently disappears usually due to a

change in environment Species that are better suited to the new conditions may

replace those that have become extinct Macroevolution – change creating a new species over time

Geographic Isolation and Evolution

Members of the original species migrated to different areas…one area perhaps had trees, and the other did not. The Tree Finches had to adapt to get insects from the trees. The Ground finches adapted to be able to open seeds. Note the beaks.

Evolution of Antibiotic Resistance

After treatment with antibiotics

The bacteria have EVOLVED to become more resistant (more of the population is resistant). This occurred through NATURAL SELECTION (the ones more equipped to survive the antibiotic treatment were able to reproduce successfully)

Evidence of Macroevolution Fossils

Change over time can be observed in the fossil record

Darwin predicted that “missing links” would eventually be found, and many were!

1990’s fossils linked whales to land mammals

Whale Evolution

Horse Evolution

Radiometric Dating of Fossils

Radioactive isotopes decay at a constant rate called a half life

Different isotopes have different half lives

Ex. C-14 N-14 5,730 years

U-238 Pb-206 4.5 billion years

Calculation Half-Lives

If this chart represents K-40 which has a half life of 1.3 billion years, how old is a sample that contains 25% of its original K-40?

Evidence of Macroevolution Anatomy

Homologous structures: similar structures though functions may vary

Ex. Human arm, bat wing, alligator arm, and penguin arm

Analogous structures: different structure, but similar functions

Ex. Butterfly wings and bird wings

Vestigial Structures: structures that are present but reduced in size or nonfunctional as compared to related organisms

Ex. Coccyx, appendix, ear muscles, wings on flightless birds

Homologous Structures

Analogous Structures Analogous

structures evolve separately in different organisms in order for them to adapt to common functions

Vestigial structures – getting smaller due to lack of use

Evidence of Macroevolution Biochemical Evidence

The species characteristics change as a result of changes in DNA, ultimately as a result of mutations

Therefore changes in DNA should accumulate over time as species become more different

Compare amino acid sequences to test relativity

The molecular record has shown the same relationships indicated by the fossil record

Evidence of Macroevolution Embryonic Development

Vertebrate embryos develop similarly

Suggests that development evolved as new genetic instructions were layered on top of older ones

Tail, limb buds, pharyngeal pouches

Embryonic Evidence of Evolution

New ‘directions’ are carried out over the old ‘directions”. SO – embryos develop similarly at first, then the new directions begin to be carried out, resulting in the differences in embryonic development

Do Now - Journal What does “FITTEST” mean – as in

“survival of the fittest”? Does an individual’s ability or desire to

reproduce make it less fit?

What did Darwin mean? The term ‘survival of the fittest’ was first

coined by Herbert Spencer, not Darwin Darwin did begin using the term to replace

“natural selection”, but not until the 5th edition of Origin of Species

He did not mean strongest, as is sometimes assumed. Any individual that successfully reproduces is contributing to the survival of its species. Therefore, the term “fit” can be considered synonymous with “able to reproduce”

Patterns of Evolution Does evolution occur gradually or in spurts?

Gradualism: Change generally occurs over long periods of time

Punctuated Equilibrium: periods of little or no change are interrupted by periods of rapid change

Biologists disagree, however fossil evidence provides evidence for both! Gaps in fossil record Sudden disappearance of some organisms Some organisms unchanged for long periods of time Some organisms changed gradually

Phylogenic Tree Phylogenic Tree – shows how organism are related

through evolution Each fork in the tree represents a common ancestor

Examples of Microevolution

Industrial Melanism: the darkening of populations of organisms over time in response to pollution Ex. European peppered moth

Biston betularia Dark variety rare until 1850, by

1950 most populations dark Kettlewell tested to see if

natural selection caused changes

Sickle cell Anemia Sickle Cell is advantageous in

central Africa where sickle cell individuals resist malaria

Antibiotic Resistance of bacteria Mutation provides resistance

and easily gets passed to future generations

Patterns of Microevolution Directional Selection:

selects for one extreme trait Ex. Where malaria is not

present, sickle cell allele is selected against

Balancing (stabilizing) Selection: selects for intermediate trait Ex. Human birth weight – too

small is too weak and too large provides complications during birth, therefore an intermediate size is selected for

Disruptive Selection: both extremes are selected for Ex. Shell Color – light shells

blend in with the sand, and dark shells blend in with rocks

Speciation Speciation: the process by which a new species forms; over

time separate populations of the same species become very different from one another

Divergence: the accumulation of differences between groups Ecological Races: populations of the same species that differ

genetically because of adaptations to different living conditions, but not different enough to be considered different species

Ecological races may continue to diverge until they can no longer reproduce…forming a new species

Maintaining a species Reproductive isolation: the prevention of mating between

formerly interbreeding groups Geographical Ecological Temporal Behavioral Mechanical Reproductive failure

Microevolution leads to Macroevolution As changes continue to accumulate over

time, living species may become very different from their ancestors and from other species that evolved from a common ancestor

Biologists agree that changes within a species eventually lead to the appearance of a new species

Do you think… That if evolution is occurring on an

ongoing basis, we would discover new species?

How often do you think new species are discovered? When do you think is the last time a new species was discovered?

New Species Discovered

•Cercopithecus Lomamiensis

•Discovered in the Lomami forest in DR Congo

•Discovered in 2012

New Species Discovered

•Trogloraptor marchingtoni

•Found in an Oregon Cave

•Discovered in 2012