Evolution vs. Creationism Here are a few websites you can look at to inquire further into the arguments for both creationism and evolution. Creationism http://www.talkorigins.org/faqs/wic.html http://www.creationism.org/ Evolution (and creationism) http://www.talkorigins.org/origins/faqs-mustread.html http://www.bcholmes.org/wicca/evolution.html
The Universe Big Bang Theory 15 bya Things cooled Atoms formed Planets, stars and solar systems formed More on the Big Bang Theory http://www.umich.edu/~gs265/bigbang.htm
The Earth About 4.5 bya Formed from collecting dust, gases, etc. Atmosphere of CO2, H2O, N2, CO and NH3 Earth cools Liquid water – needed for life 3.8 bya More information http://mediatheek.thinkquest.nl/~ll125/en/bigbang.h
First Organic Compounds H2 + CH4 + NH3 + heat + lightening = simple organic compounds Amino acids Monosaccharides Miller and Urey (1950’s) Tested Oparin’s hypothesis Meteorites? More information http://www.chem.duke.edu/~jds/cruise_chem/Exobiolo gy/miller.html
First Cell-like StructuresProtobionts Microspheres Proteins organized as a membrane Coacervates Droplets of organic compounds So what? Life-like Grow in size Take in substances from surroundings Bud in two (reproduce) Catalyze reactions Maintain membrane potential Spontaneous Could lead to first cells
First “Cells” RNA considered key Many forms Simpler than DNA Ribozymes RNA can act as an enzyme!!!! Mechanism for self-replication Maybe . . . Self-replicating RNA ended up inside a coacervate or microsphere creating first cell- like structure
First Prokaryotes 3.5 bya Very simple single-celled organisms Similar to some of today’s prokaryotes Chemoautotrophs first Break down inorganic compounds for energy Archaebacteria Photoautotrophs evolve Create oxygen Changed everything
Definition of Evolution The processes that have transformed life on Earth from its earliest forms to the vast diversity that characterizes it today Mechanism for Evolution Natural Selection Two types of evolution Intraspecies Single species evolves Interspecies New species evolves
Historical Context Aristotle For 2000 years -- species are perfect, they don’t evolve Religion Creationism – same idea, God created all life Most Scientists (1700’s) Natural Theology dominated – again, same idea Lamarck (1809) Organisms evolve from ancestors-(1 st to say) Use and disuse Acquired characteristics Darwin (1859) “The Origin of Species” Few people held similar beliefs at that time
The Voyage of the Beagle Darwin’s observations One – Species fertility = exponential growth Two – Populations generally stable Three – Resources limited Leads to competition Four – Individuals vary Five – Much of this variation is heritable If variation is beneficial, variation will flourish (lots)
Darwin’s Conclusion Evolution through adaptation due to natural selection i.e. Some individuals (because of variation) in a population will have better success at surviving and reproducing; therefore, the heritable traits of those organisms will be passed on while the heritable characteristics of less successful individuals will not.
Darwin’s Overall View Unity in life – all organisms relate back to an unknown original ancestor New species arise through evolution Depicted by a phylogenetic tree Shows evolutionary history
“The Origin of Species" Two main points States the occurrence of evolution (descent with modification) Natural selection is the mechanism for evolution
Things to Note A population is the smallest unit that can evolve (a population is a group of interbreeding individuals belonging to a particular species in a given geographical area). Only heritable characteristics can be amplified or diminished through natural selection Generally, natural selection leads to evolution slowly over a long period of time.
EVIDENCE OF EVOLUTION One – BIOGEOGRAPHY Geographical distribution of species Example Kangaroo Armadillo Question: Why are tropical animals of South America more closely related to species of South American deserts than to species of the African tropics?
EVIDENCE OF EVOLUTION Two – FOSSIL EVIDENCE Fossil age can be determined through radioactive dating Similarities in anatomy/morphology can be compared between fossils and similar extant organisms Often supports and is supported by other evidence.
EVIDENCE OF EVOLUTION Three – COMPARATIVE ANATOMY Homologous Structures Vertebrate forelimbs Vestigial Structures Tailbone in humans Pelvic bones, hind legs of whales
EVIDENCE OF EVOLUTION Four – COMPARATIVE EMBRYOLOGY A study of embryos and how they develop. Closely related organisms go through similar stages of embryonic development. Example All vertebrates (birds, snakes, mammals, fish, frogs) go through an embryonic stage where they have gill pouches on the sides of their throats Figure 15-9, page 291
EVIDENCE OF EVOLUTION Five – MOLECULAR BIOLOGY compare amino acid sequences of proteins compare DNA/RNA Mitochondrial, ribosomal All organisms have nucleic acids made up of the same kinds of molecules, universal!!! Humans and even the simplest prokaryotes share some genes/proteins in common. Example – Cytochrome C, a protein involved in aerobic respiration. NOTE: very similar DNA = very closely related
Direct Evidence of IntraspeciesEvolution Selective breeding in animals Selective breeding in plants, especially crops Guppies (Poecilia reticulata) of South America and Trinidad http://www.pbs.org/wgbh/evolution/sex/guppy/low_bandwidth.html
COEVOLUTION Species closely associated with each other evolve together Example Long-nosed fruit bat and the flowers on which they feed
CONVERGENT EVOLUTION Distantly related species evolve in similar ways due to similar environment. Example – Sharks and Porpoises Morphologies are adapted to life in the water and are very similar. Analogous structures are associated w/ convergent evolution
DIVERGENT EVOLUTION Closely related species become more and more dissimilar Can result in a new species ADAPTIVE RADIATION Many related species evolve from a single ancestor Galapagos Finches – likely related to food ARTIFICIAL SELECTION (selective breeding) Domesticated dogs
Genetic Equilibrium Population Genetics Study of evolution from a genetic point of view, i.e. traits POPULATION-smallest unit which may evolve Bell curves When graphed, many traits within a species take on the shape Indicates high # of individuals in the middle (average) with fewer #’s at either extreme (high or low) for a given trait. Many polygenic, quantitative traits show this type of distribution
Genetic Equilibrium Punnett’s square’s allow genotype and phenotype predictions for a new generation of offspring from a parent gene pool Recall that from one generation to the next genotype and phenotype (gene pool) vary greatly. In nature, gene pools tend to remain stable more than in the finite example we have looked at.
Genetic Equilibrium Hardy-Weinberg Genetic Equilibrium Allele frequencies in a population tend to remain the same from generation to generation unless acted on by outside influences Based on an “ideal” population (hypothetical)
Hardy-Weinberg Equilibrium1. No net mutations occur (no change due to mutation)2. Individuals do not enter or leave population3. Large population (infinitely)4. Random mating required5. Selection does not occur More than anything, allows us to consider forces which may disrupt equilibrium and as a result, drive evolution
Disruption of Genetic Equilibrium Mutations Caused by outside factors Migration No immigration or emigration from population Genetic Drift Random chance affects allele frequency (more likely in small populations) Nonrandom Mating Humans violate with assortative mating Animals violate by mating by geographic proximity
Disruption of Genetic Equilibrium Natural Selection Stabilizing selection – individuals with average form of trait have highest overall fitness for environment Directional selection – individuals with an extreme form of a trait have better fitness for environment Disruptive selection – individuals with either extreme of a trait have better fitness than individuals with average form Sexual selection – mating based on certain traits , only genes of reproducers are important in evolution
Speciation The process of species formation Species – single type of organism capable of producing fertile offspring in nature Occurs with a disruption in genetic equilibrium, often a form of isolation Geographic isolation Physical separation Reproductive isolation Prezygotic isolation Postzygotic isolation