How did the Earth come to be? The three most widely accepted ideas: 1.Spontaneous generation 2.Divine creation 3.Extra-terrestrial (meteor or asteroid)

What was the early earth like?

Cyanobacteria– believed to be responsible for oxygenating the earth

Biogenesis vs. Spontaneous generation Biogenesis Living things come only from other living things Pasteur Redi Spallanzani Spontaneous Generation Living things can arise from non-living things Attempts to explain origin of life on earth Miller & Urey

Pasteur’s experiment (Redi & Spallanzani had similar experiments) was meant to prove that living things cannot spontaneously generate from non-living.

Miller-Urey Experiment (produced molecules of life from a non-living environment)

The Bubble Model– primordial soup

1. Chemical environment (earth is cooling, volcanoes, storms) 2. Primitive proteins are formed. 3. Molecules form into cell structures. 4. Primitive bacteria are formed.

Endosymbiosis– the process that could have resulted in the evolution of prokaryotes to eukaryotes 1) infolding of the plasma membrane became ER & Golgi 2) Engulfing smaller bacteria became organelles like mitochondria & chloroplasts

The Fossil Record How they determine the age of the earth How they track the progression of living things on earth Carbon-14 dating tells the approximate age of fossils (based on half-life) radioisotopes have a known rate of decay, measuring the amount of a radioisotope tells its approximate age Examples: sediments, molds, bones, casts, prints, shells

2 Theories of Evolution Lamarck Proposed that species descended from a common ancestor Believed in acquired traits– not from heredity but from experience and behavior Darwin Proposed the idea of natural selection Believed that genetic traits are passed to offspring Survival of the fittest Jean Baptiste Lamarck ( ) Charles Darwin ( )

Darwin’s voyage on the H.M.S. Beagle, Darwin was the ship’s naturalist, meant to collect specimens & make observations. At some points, the ship left him at ports for months at a time. He trekked hundreds of miles through unmapped territory, and collected fossils and specimens. After extensive study in the Galapagos, Darwin determined that over millions of years, large differences can occur among species

Evolution by Natural Selection (Darwin’s theory) 1.All species have genetic variation 2.Living things face many challenges in the struggle for existence. 3.Individuals of the same species compete with one another for survival. 4.Individuals that are better able to cope with the challenges of their environment tend to leave more offspring than those less adapted. 5.The population changes to reflect the characteristics of the individuals more suited for survival.

The process of natural selection changes a population over time. 1.All species have variety. 2.Organisms struggle for survival. 3.Individuals compete with each other. 4.Individuals who are more fit for survival live longer and reproduce more successfully. 5.The traits of the more fit will be passed down to new generations. Long necks= adaptive advantage

Patterns of Evolution Coevolution– change of two or more species in close association with each other Pollination relationships are very common examples of coevolution. Predator-prey relationships

Patterns of Evolution Convergent evolution– two species appear similar though they have no connection. Phenotypes were selected to suit the environment.

Patterns of Evolution Divergent evolution- two or more related species become more and more dissimilar (due to change in habitat, environmental causes) –Adaptive radiation– many species evolve from a single ancestor (Darwin’s galapagos finches) –Artificial selection– species are bred to emphasize certain traits. (ex. Dogs & race horses)

Darwin’s Theories Descent with modification– newer forms of species appearing in the fossil record are actually modified descendents of older species (organisms give rise to others similar to themselves) Modification by natural selection– since organisms are in competition for resources & space, organisms that are better adapted for survival become prevalent in the population. survival of the fittest adaptive advantage

Evidences of Common Ancestry Anatomy– structures that are similar Embryology– development of embryos is similar Biochemistry– DNA and proteins are the same

Evidence of common ancestry Homologous structures– similar structures across diverse species

NOT evidence of common ancestry Analogous structures– similar functions, look somewhat alike, but have different development & anatomy – implies common adaptive advantages

Evidence of common ancestry Vestigial structures– apparently useless features that may be leftovers from an ancestor appendix tailbone

Evidence of common ancestry Embryological similarity

Evidence of common ancestry Embryological similarity

Evidence of common ancestry Embryological similarity

Evidence of common ancestry Embryological similarity

Evidence of common ancestry Macromolecular similarity– many species share almost the same DNA, and they’re all made of adenine, guanine, cytosine, and thymine.