Ch. 19 Descent With Modification
AP Biology Notes

Evolution – descent with modification

“Evolutionary” Scientists
Aristotle – believed things could be arranged on a “scale of nature”, increasing complexity. Organisms were arranged on a ladder.

Linnaeus – developed taxonomy, the study of naming & classifying organisms; binomial nomenclature
Domain, Kingdom, Phylum, Class, Order, Family, Genus species (scientific name) ex. Homo sapiens

Georges Cuvier – father of paleontology, studied sedimentary rocks, believed in extinction and catastrophism. Opposed evolution.

James Hutton – developed Gradualism, change happens by a slow, continuous process.

Charles Lyell – geologic processes have not changed since the beginning of time, rate of erosion has not changed.

Jean – Baptiste Lamarck – published theory of evolution in 1809 (same year as Darwin’s birth). Came up with two ideas:
1) theory of use & disuse: those parts used to cope with the environment become larger/stronger, those not used go away (ex) blacksmith develops larger biceps, giraffes neck stretches to reach trees
2) inheritance of acquired characteristics: changes can be passed on to offspring, dyed hair color
NO evidence that acquired characteristics carried on – blacksmiths arm not passed on

Charles Darwin – (1809-1882) became clergyman, HMS Beagle voyage around the world, collected different specimens & made observations at all stops during trip. Galapagos Islands – finches, mockingbirds,
1836 – returned from voyage
1844 – wrote an essay on natural selection but did not reveal his discovery
1858 – Alfred Wallace wrote telling that he had found the same discoveries as Darwin; Darwin submitted his essay; published it 1859 On the Origin of Species

2 main points in paper: 1) species today came from ancestral species, 2) developed term “natural selection” populations change over time

Darwin uses term descent with modification rather than evolution, he believed that the history of life was like a tree

Darwins Main Ideas
1. Natural selection is differential success in reproduction
2. Natural selection occurs through an interaction between the environment and the variability inherent among the individual organisms making up a population
3. The product of natural selection is the adaptation of populations of organisms to their environment.

Each generation has the environment filter heritable variations – some favorable, some not

Some species showed selection via Artificial selection (breeding domesticated plants & animals)

Darwin felt that if artificial selection could change populations in a short time period, then natural selection could happen over hundreds or thousands of generations; less favorable characteristics disappear.

Natural selection involves heritable characteristics only, not acquired ones
Population is extremely important on natural selection
Population is the smallest unit that can evolve, individuals do not evolve
Natural selection is situational – adaptation that may be positive in one place may be negative in another.

Examples of Natural Selection
1. Insecticide resistant insects – new spray kills 99% of bugs, 1% continue to live and pass on resistant genes, over time few bugs will be resistant
2. Drug resistant bacteria – resistance in individuals occurs early, MRSA

Homology – similarities in characteristics resulting from common ancestors
Homologous structures are those that contain the same bones
but the structures have different functions in different animals.
The same bones make up the forelimbs of mammals.
(bat wing, human arm, whale flipper)

Vestigial organs are those that have little or no value now, but once did. (wisdom teeth, hip bones in snakes, appendix, tonsils)

Embryological homologies – embryos of vertebrates look similar have
pharyngeal pouches in throat area = gills for fish, Eustacian tubes for people

Molecular homologies – comparison of DNA sequences in all organisms

Geographic distribution of species shows evidence for evolution
Islands have endemic species (only found in that place); these may be related or similar to species found on nearby land masses.

Fossil Record – prokaryotes  eukaryotes
Vertebrates: fish  amphibians  reptiles  birds & mammals