UNIT 9

Evolution

Darwin and Evolution

Charles Darwin

Naturalist1809-1882Traveled on HMS Beagle for 5 years (22 yrs old)

Galapagos islands- unique animals like the turtles and finches found there

Travel and observations lead to Darwin's ideas………

Influences on Darwin• Hutton: Earth is shaped by geologic forces-older than

millions of years• Lyell-processes on Earth have been happening for a long

time and these processes have shaped the Earth’s geologic features

• Lamark-use and disuse,inheritance of aquirred traits• Malthus-human population will grow faster than raw

materials can be produced

Natural Selection

Explanation of how populations change over time ( a very long time)

Another way to say this:

Survival of the Fittest- those organisms within the group have some sort of variation that allows them to survive and produce offspring with the same variation

For all populations these factors must exist for natural selection:

Organisms overproduce- more babies born than will actually survive

Variations exist within the species- example: fish scale color

Variations passed on to offspring Overtime the population changes to exhibit the favorable

variations

Artificial selection• Humans select desired traits• Dog breeds

• Descent with modification-each living species has desended with changes from other species over time.

• Common descent-all species derived from common ancestor

Evidence of EvolutionSeen in:

Structural changes

a. camouflage- blend into surroundings

b. mimicry- look like another organism with a favorable trait

Physiological changes- metabolism

ex. Drug resistant bacteria

Camouflage Mimicry

We can see the changes by showing relationships between organisms

1.Fossils- a. molds (left behind by

soft tissue)

b. bones

2. Anatomy-look at structures

a. homologous- similar in arrangement and/or function

b. Analogous – similar in function but not in structure

C. Vestigial- organ or structure not used any more like our appendix. Do you know what animal has a working appendix?

RABBITS

Other examples:

Molars in vampire bats

leg bones in snakes and whales

ear muscles in humans

3. Embryology- study of embryos. Look for similarities.

4. Biochemistry-horseshoe crab biochemistry more similar to spiders than other crabs.

5. Geographic distribution-similar animals develop in different areas due to common conditions.

www.ngm.nationalgeographic.com/ngm/0411/feature1/multimedia/index.html

Population Genetics

Gene pool- # or % of alleles in a population Allelic Frequency- % of a specific allele in a gene pool.

(Ex.- how many B’s or b’s in the classroom)

Do populations change? YES!!!! Genetic Equilibrium- no real change in allelic frequency

of population

Ways a Population Can Change

Mutation- (in gametes) Sexual reproduction Genetic Drift- alteration by chance event like an

earthquake, fire, flood-change in allelic frequency Gene Flow- movement in or out of organisms in a

population. Ex. All the people with blue eyes moved to Canada- what would happen to the allelic frequency of b?

Traits controlled by a single gene will have a greater chance of differences in allelic frequency and therefore lead to change.

3 Types of natural SelectionWhich group is favored?

Middle group- STABALIZING SELECTION One extremes- DIRECTIONAL SELECTION Both extremes- DISRUPTIVE SELECTION

Hardy –Weinberg Principle• In order to maintain genetic equilibrium:

1. Random mating

2. Large population

3. No movement in or out

4. No mutations

5. No natural selection

How do new species form?

Speciation- evolution of a new species-new group is unable to breed with old group

Behavioral isolation- wrong mating dance Geographic Barrier- splits group and over time changes

occur in one or both groups that do not allow them to breed with each other.

Reproductive isolation- 2 groups can’t mate with each other –parts don’t fit, different mating cycles (Temporal)

How fast does evolution occur?

Speciation Rate- speed of evolution

Gradualism- speciation occurs gradually over a long period of time

Punctuated- short quick bursts( dinosaurs)

TaxonomyThe Classification of Organisms

• Branch of biology that groups and names organisms based on similarities

Taxonomy

• Aristotle started grouping plants into 3 categories: herbs, shrubs, and trees

Early Classification Systems

• Based his groupings according to physical and structural characteristics

• Had a 2 word naming system like a first and last name called

BINOMIAL NOMENCLATURE• Used Latin because it is universal and it’s a dead

language (it doesn’t change)

Carolus Linnaeus (1707-1778)

• When we name organisms we usually just give the Genus and species name like

• Homo sapien

• Note that the Genus name is capitalized and the species name is in lower case

• In print you will see the Genus and species name in italics.

Biggest to smallest

(Domain)

Kingdom

Phylum

Class

Order

Family

Genus

Species

Kings play chess on fine green sand

Order of classification

• Structural similarities• Breeding behavior• Geographical distribution• Chromosome comparison (how many bases match)• Biochemistry

How are the groups decided?

Domains Bacteria-prokaryotic, cell wall made of

peptidoglycan,common like strep,staph Kingdom-Eubacteria

Archaea-prokaryotic,live in extreme environment Kingdom- Archaebacteria

Eukarya- eukaryotic cells Kingdoms-Protista,Fungi,Plantae,Animalia

Domain Eukarya

Protista-animal like, plant like, fungi like, most single celled, some photosynthetic

Fungi- heterotrophs, decomposerPlantae- multicellular, photosynthetic, cell wall

Animalia- multicellular, heterotroph