Evolution before Darwin

Transcription

1 Charles Lyell and Geology Geological forces could account for the differences in the world Con7nental Dri9 and Plate Tectonics Only book that Darwin took with him on his voyage Georges Cuvier and Ex7nc7on Discovered that different rock layers held fossils of different organisms Organisms go ex7nct and new organisms arise %3AY3JpcGVjQGxjc2MuazEyLmluLnVz/ EarSci jpg jpg 1

2 Jean-Bap7ste de Lamarck and Evolu7on Organisms change form over genera7ons through inheritance of acquired traits Believed that animals acquired traits and passed them on to their offspring Jean-Bap7ste de Lamarck and Evolu7on Organisms change form over genera7ons through inheritance of acquired traits Believed that animals acquired traits and passed them on to their offspring Jean-Bap7ste de Lamarck and Evolu7on Organisms change Not what form happens. over genera7ons through inheritance of acquired traits Believed that animals acquired traits and passed them on to their offspring Charles Darwin Hypothesized the idea of Evolu7on via Natural Selec7on (which is now a theory well known to occur in biology) 2

3 Charles Darwin Joined the Voyage of the HMS Beagle in 1831 Collected organisms Galapagos Islands Stopped here in 1835 No7ced varia7ons in organisms from island to island Learned later that these were different species, not variants of one species and were related to finch species found on mainland South America Common descent with modi>ication Par7cular groups, or species, of living things can undergo modifica7on in successive genera7ons, with such change some7mes resul7ng in the forma7on of new species Common descent with modi>ication Par7cular groups, or species, of living things can undergo modifica7on in successive genera7ons, with such change some7mes resul7ng in the forma7on of new species This is possible because of Natural Selec7on which Darwin hypothesized a9er his voyage 3

4 Alfred Russel Wallace Also hypothesized Natural selec7on at the same 7me, but Darwin published first (a9er Wallace contacted Darwin for his opinion). Radiometric da7ng a technique for determining the age of objects by measuring the decay of the radioac7ve elements they contain Half-life Fossils looking at sediment layers worldwide, there are similar fossils that are found in the same or similar geologic layers Morphology the study of the physical forms that organisms take 4

5 Homologous characters characters that are the same due to inheritance from a common ancestor All mammals have the same bones in forelimbs Ves0gial character a trait that an organisms has that has minimal func7on compared to that of the ancestor or other related organisms. Example: nic7ta7ng membranes in you vs. rep7les Ves0gial character a trait that an organisms has that has minimal func7on compared to that of the ancestor or other related organisms. Ostrich Wings Microevolution Microevolu7on a change in allele frequency in a popula7on over a rela7vely short period of 7me Gene pool the alleles that exist in a popula7on Popula7ons members of species that live in a defined geographic region at a given 7me 000/006/cache/ostrich_653_600x450.jpg 5

6 Agents of Evolution Mutations Muta7ons: a permanent altera7on of a DNA base sequence Point muta7ons are those that happen at a single nucleo7de base pair Mutations Muta7ons: a permanent altera7on of a DNA base sequence Point muta7ons are those that happen at a single nucleo7de base pair All cancers are caused, ul7mately, by muta7ons Most muta7ons occur in soma0c cells Others occur in the cells that become eggs and sperm Gives offspring diseases that parents do not have Defini7on alterna7on in an organisms DNA Point muta7ons Dele7ons Mutation 6

7 Mutation Defini7on alterna7on in an organisms DNA Can cause differences in organisms which can lead to evolu7on in a popula7on Gene >low (migration) Defini7on the movement of alleles from one popula7on to another Migra7ons the movement of individuals from one popula7on into the territory of another popula7on Gene >low (migration) All plants in Hawaii are descendents from species introduced to the islands All plants have come to the islands via migra7on or introduc7on Wind, water, animal dispersal Human introduc7on Genetic drift Defini7on chance altera7ons of gene frequencies in a popula7on Usually occurs in small popula7ons 7

8 Genetic drift Defini7on chance altera7ons of gene frequencies in a popula7on Usually occurs in small popula7ons Genetic drift Two ways this type of gene7c dri9 can happen: Bo_lenecks survival of a few Founder Effects migra7on of a few Genetic drift - Bottlenecks Bo_leneck effect a change in allele frequencies in a popula7on due to chance following a sharp reduc7on in popula7on size Usually due to death of much of the popula7on Genetic drift Founder Effect Founder Effect when a small subpopula7on migrates to a new area to start a new popula7on Only happens when they only bring part of the gene pool Chapter22/founder.jpg 8

9 A process through which traits that confer a reproduc7ve advantage to individuals organisms grow more common in popula7ons of organisms over successive genera7ons These traits are adapta7ons modifica7ons in the form, physical func7oning, or behavior of organisms in a popula7on over genera7ons in response to environmental change) Depend on fitness the success of an organism in passing on its genes to offspring rela7ve to other members of its popula7on at a par7cular 7me More offspring = higher fitness 9

10 Darwin s Finches on Galapagos Islands ON Daphne Major (Is) Geospiza for,s Drought in 1977 led to 85% pop decline Only birds with large beaks that could crack tough seed survived Led to a change in the alleles of the popula7on Sexual selection (preview for next time) h_p:// v=e1zmftr2d4c bowerbird-5-vogal.jpg 10

11 Types of selection Stabilizing selection Directional selection Disruptive selection Selec7on for red chest birds OR brown birds Intermediate birds are not selected for. 11