River Dell High School Biology ORIGIN OF LIFE Theories Past and Present Nature of Early Cells Evolution of Cells River Dell High School Biology

Main QUESTIONS What is evolution and how do we determine evolutionary relationships? Where does variation come from and what role does it play in evolution? Is there one best way to be? Which wolf activity… Describe your wolf (physically and behaviorally) What is good about it? What are its disadvantages?

EVOLUTION The idea that over time things change in response to the environment. Variation is at the heart of evolution because there is no one best way to be all the time. Where does this variation come from? Meiosis Sexual reproduction Crossing over and independent assortment mutations

EVIDENCE The evidence we gather to determine these evolutionary relationships come from observing the similarities and differences of and today’s living organisms and those that used to be living.

I. Evidence of Evolution A. Fossils 1. Definition - trace or remains of organisms that are preserved 2. types a. mold (rock imprint) b. cast (mold that is filled) c. petrified (converted into stone/mineral) d. preserved in amber or tar pits

Mold Fossil Cast Fossil Fossil in Amber Petrified Wood

Dinosaur Fossils Toe of a Dinosaur

I. Evidence of Evolution A. Fossils 3. location a. sedimentary rock b. amber or tar pits 4. distribution a.Law of Superposition(Steno 1638-1686) 1) relative age 2) absolute age b. Biogeography (study of location of organisms around the world)

Fossils Are Found in Tar Pits

Sedimentary Rock Showing Layers Law of Superposition – younger fossils are closer to the surface – older fossils are deeper Sedimentary Rock Showing Layers

IV. Radioactive Decay and Dating A. Isotope – atoms of the same element that differ in the number of neutrons B. Radioactive decay – process in which unstable nuclei release particles and/or energy until they are stable C. Half-life – the length of time it takes for ½ any amount of a radioactive isotope to decay

Half-lives 256 14C atoms at time 0 --------------------------- 128 14C and 128 14N atoms after 5,600 years or 1 half-life ----------------------------- 64 14C and 192 14N atoms after 11,200 years or 2 half-lives

Half-lives 32 14C and 224 14N atoms after 16,800 years or 3 half-lives ------------------------------ 16 14C and 240 14N atoms after 22,400 years or 4 half-lives ----------------------------- 8 14C and 248 14N atoms after 28,000 years or 5 half-lives

Half-lives 4 14C and 252 14N atoms after 33,600 years or 6 half-lives ---------------------------------- 2 14C and 254 14N atoms after 39,200 years or 7 half-lives

500 C-14 atoms will remain (1/2 original amount) The half-life of C-14 is 5,600 years and a sample today has 1,000 C-14 atoms, after 5,600 years  500 C-14 atoms will remain (1/2 original amount) After two half lives (11,200 years)  250 C-14 atoms will remain (1/4 original amount) Proportion of isotope left 1/4 1/8 1/16 1 1/2 3 4 5 2 Half-lives 1

I. Evidence of Evolution B. Comparative Anatomy 1. homologous structures a. similar structure, evolution, development b. wing, arm, flipper 2. analogous structures a. similar function b. wing of a bird and an insect

Homologous vs Analogous Structures

I. Evidence of Evolution B. Comparative Anatomy 3. vestigial structures a. useful in past organisms but not now b. appendix, tail vertebrae, ear muscles

Vestigial Structures Appendix in Humans Leg Bones in a Whale

I. Evidence of Evolution C. Embryology Similarities 1. Haeckel(1834-1919) [German] a. “ontogeny recapitulate phylogeny” 1) embryo undergoes changes that repeat evolutionary development

Diagram Showing Similarities in Early Stages of Embryo Development

I. Evidence of Evolution D. Biochemistry 1. similarity in amino acids in specific proteins 2. similarity in RNA and DNA base sequences

Comparing Amino Acid Differences of Several Organisms to Humans

II. Theories of Evolution A. Lamark (1744-1829) 1. Acquired traits – traits that develop during one generation can be passed to the next generation 2. Law of Use and Disuse – if a trait is not used it will be lost “use it or lose it” mentality….

Lamarck and Law of Use and Disuse According to Lamarck the giraffes pictured grew longer necks in order to reach the leaves in taller trees The longer necks were then passed to the next generation

II. Theories of Evolution B. Charles Darwin(1809-1882) 1. Biography a. Darwin attended medical school b. studied to be a clergyman c. 22 years old - signed on HMS Beagle 1) collect specimens as a naturalist 2) refined data for 21 years

Charles Darwin Darwin’s Home

HMS Beagle in Sydney Australia Harbor

Darwin’s Voyage

Darwin’s Finches

II. Theories of Evolution B. Charles Darwin(1809-1882) 2. The Origin of Species (1859) a. Descent with modification 1) all species descend from a small number of original types 2) there is variation among organisms http://www.talkorigins.org/faqs/origin.html

II. Theories of Evolution B. Charles Darwin(1809-1882) b. Modification by Selection 1) environment limits growth of populations -competition for life’s necessities -specific traits are selected 2) adaptive advantage - trait favorable for a given environment - adaptations make some organisms more likely to survive than others

II. Theories of Evolution B. Darwin’s terms 3) fitness - ability of an organism to make a genetic contribution to the next generation 4) natural selection allows individuals with survival adaptations to pass traits to offspring

II. Theories of Evolution 5) speciation - formation of new species as favorable adaptations accumulate (butterfly- white/black) 6) “survival of the fittest” - those organisms with favorable traits reproduce and pass their traits to future generations

Darwin’s theory in a nutshell Overproduction of Organisms Variation in organisms Competition to survive Some characteristics increase chances for survival and reproduction These characteristics allow organisms with them (Fit organisms) to reproduce better than others (which will die out and not pass on genes) Good characteristics will get passed on as organisms “evolve” to have the trait. Maybe forms new species? (speciation)

III. Patterns of Evolution A. Coevolution 1. changes in two or more species closely associated 2. examples a. predator and prey b. parasite and host c. plants and plant pollinators

III. Patterns of Evolution B. Convergent Evolution 1. similar phenotypes are selected (b/c of environment) but ancestors are very different a. natural selection of analogous structures because of envir. demands. 2. examples a. wings in insects and birds b. fins & shape of sharks, fish, porpoise

Examples of Convergent Evolution

III. Patterns of Evolution C. Divergent Evolution 1. two or more related populations or species become more dissimilar a. speciation - new species may form 2. example geographic isolation a. brown bear  polar bear

III. Patterns of Evolution C. Divergent Evolution 3. adaptive radiation a. many species evolve from same ancestor 1) ancestor migrates to different environments (example) - Galapagos finches

Adaptive Radiation – Darwin’s Finches

Beak shape Depends Upon Food Source

Adaptive Radiation – Hawaiian Honeycreepers

IV. Variation in Populations A. Distribution of variations 1. graph is a bell curve B. Natural Selection and Changes in Populations 1. Stabilizing Selection – favors average form 2. Directional Selection – average shifts to one extreme or the other 3. Disruptive Selection – extreme forms are favored- number of individuals with the average form is reduced

Stabilizing Selection

Directional Selection

Disruptive Selection

V. Speciation and Rate of Evolution A. Species - organisms that are morphologically similar and can interbreed to produce fertile offspring Speciation - process of forming species

V. Speciation and Rate of Evolution A. Species and Speciation 2. Isolating mechanisms that result in speciation a) geographic barriers separate populations 1) gene flow stops and natural selection and genetic drift result in divergence b) reproductive barriers - prevent breeding of organisms in the same geographic area

V. Speciation and Rate of Evolution B. Rate of Evolution 2. Gradualism (Darwin) - new species arise slowly and continuously through small, gradual changes 3. Punctuated Equilibrium (Steven Gould and Niles Eldredge) - there are long periods (up to millions of years) with little or no change - then there is a short period of rapid change

SO WHERE THE VARIATION EVOLUTION ACTS UPON COME FROM SO WHERE THE VARIATION EVOLUTION ACTS UPON COME FROM??? AND WHAT CAUSES CHANGES IN POPULATIONS OVER TIME??

Variation in Populations C. Genetic Sources of Variation 1. Mutations a) a specific gene mutates in 1/10,0000 gametes b) thousands of genes in each gamete c) some mutations in every zygote d) most mutations are recessive 2. Recombination a) random meeting of sperm and egg b) crossing over during meiosis