Evolution And Natural Selection

Early Earth Believed to be 4.5 billion years old Thought to have had a very anaerobic atmosphere Earliest organisms were able to survive primitive environments Prokaryotes that resemble today’s bacteria Endosymbiotic theory – says that eukaryotes arose from small prokaryotes living inside of larger prokaryotes Lead to development of double membrane bound organelles like mitochondria and chloroplasts

Older theories of evolution… Darwin wasn’t the only one! Jean Baptiste Lamarck (early 1800’s) proposed: “The inheritance of acquired characteristics” He proposed that by using or not using its body parts, an individual tends to develop certain characteristics, which it passes on to its offspring.

. Thomas Malthus Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone

Wallace Shared ideas with Darwin Formulated his own theory of evolution that it resulted largely from competition among resources – he thought COMPETITION was the driving force behind evolution

Charles Darwin Darwin set sail on the H.M.S. Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals. On the Galapagos Islands, Darwin observed species that lived no where else in the world. - These observations led Darwin to write a book. “On the Origin of Species by Means of Natural Selection”

CHECKPOINT Who believed that acquired characteristics were passed on or inherited? Hand up – Darwin Deuces up – Wallace Thumbs up - Lamark

“Origin of Species” 2 Main points: NATURAL SELECTION 1. Species were not created in their present form, but evolved from ancestral species. 2. Proposed a mechanism for evolution: NATURAL SELECTION Individuals with favorable traits are more likely to leave more offspring better suited for their environment.

Natural Selection

Artificial Selection The selective breeding of domesticated plants and animals by man Humans select variations that are useful Ex: a farmer only breeds his best livestock

CHECKPOINT For the following examples… Thumbs up = natural selection Thumbs down = artificial selection Pesticide (pest killer) resistant insects Dog breeding Mating two quality race horses to get quality offspring Galapagos islands finches Talk to your neighbor and come up with one example of natural selection and one of artificial selection

Summary of Darwin’s Theory 1. Organisms differ; variation is inherited 2. Organisms produce more offspring than survive 3. Organisms compete for resources 4. Organisms with advantages survive to pass those advantages to their children (“Survival of the fittest”)

Evidence of Evolution Fossil record – fossils and the order in which they appear in layers of sedimentary rock Absolute dating: Relative dating: Can determine a fossil’s relative age Performed by estimating fossil age compared with that of other fossils Can determine the absolute age in numbers Is performed by radioactive dating – based on the amount of remaining radioactive isotopes

Evidence of Evolution Biogeography: Embryology: Geographical distribution of living species Similar animals in different locations Embryology: Study of structures that appear during embryonic development

Evidence of Evolution Vestigial Structures: Homologous structures: Body parts of different organisms that have similar structures but may have different functions Analogous structures: Do NOT indicate shared ancestry Body parts with similar functions but not structures Vestigial Structures: Body parts that serve no major or useful role in an organism’s life functions Ex: human appendix

SUMMARY Use the word EVOLUTION to create an acrostic using key words and phrases from our notes and discussions over the last couple days! E V O L U T I N