UNIT FIVE – Evolution Main Idea: How have species changed over time? (long periods of time) Darwin and Mechanisms of Evolution: The theory and why it works The theory and why it worksThe theory and why it works Click on image for Brain pop video on Darwin 4:20

Evidence of Evolution: The Fossil Record Indicates life began 3 byaIndicates life began 3 bya Prokaryotes then Eukaryotes then multicellular EukaryotesProkaryotes then Eukaryotes then multicellular Eukaryotes Fossil record determines:Fossil record determines: When species appearedWhen species appeared The type of environmentThe type of environment When/if species became extinctWhen/if species became extinct

Fossils found in the rock layers are similar in some layers, but different in other layers. This shows us that the species had changed over time. [Remember that the oldest rock layers are below the youngest rock layers] YOUNG OLDER

What does the theory of evolution say? Theory b/c lots of evidenceTheory b/c lots of evidence Tested and re-tested by many scientistsTested and re-tested by many scientists States that:States that: Variations in individuals can lead to changes in whole speciesVariations in individuals can lead to changes in whole species

1. Trunk = an ancestor common to all organisms represented on the tree. 2. Branches = ancestors common to species at the ends of the branches. 3. Buds of the tree = species that are alive today. 4.Branches without buds at the ends = species that have died out (or have gone extinct). It is believed that evolution does not necessarily produce any long-term progress in any one direction. Instead, evolutionary changes appear to be more like the growth of a bush. Turn to pg 81 of your RB

Video : Video : How Does Evolution Really Work? 6 min The theory and why it works The theory and why it works Charles Darwin did not only suggest that species evolved. He also suggested how evolution might have occurred. Let’s travel to Ecuador to see how the process of natural selection operates in populations of rainforest hummingbirds.

Evolution Video (21:22min)

Natural Selection: The Idea Behind the Theory / Evolution controlled by NATURAL processesEvolution controlled by NATURAL processes THE PROCESS IS:THE PROCESS IS: LIVE + BREED + PASS ON GENETIC INFO LIVE + BREED + PASS ON GENETIC INFO = SURVIVAL OF SPECIES = SURVIVAL OF SPECIES “Survival of Fittest”“Survival of Fittest” Those best ADAPTED will be able to DO THE PROCESSThose best ADAPTED will be able to DO THE PROCESS

Results of Natural Selection Short term result:Short term result: Best fit (adapted) will pass on GOOD genes to offspringBest fit (adapted) will pass on GOOD genes to offspring Long term result:Long term result: Change in frequency (number) of certain traitsChange in frequency (number) of certain traits Which do you think will increase in frequency GOOD OR BAD? GOOD OF COURSE! As more individuals have good trait, species is evolvingAs more individuals have good trait, species is evolving

What drives evolution? Interactions between individuals and the environment: 1.OVERPRODUCTION 2.STRUGGLE FOR SURVIVAL 3.GENETIC VARIATION 4.SELECTION BY THE ENVIRONMENT

Evolution Cause #1: OVERPRODUCTION POTENTIAL TO PRODUCE MORE OFFSPRING THAN WILL SURVIVE This means the best “fit” individuals will survive, grow and reproduce. EX: DEER, FISH

Evolution Cause #2: STRUGGLE FOR SURVIVAL Overproduction leads to STRUGGLE within species: 1.O nly some live to reproduce 2.C ompetition for resources 3.B est competitors will live and breed Must STRUGGLE with environment also (disease, predators, temp changes etc) Those that withstand will survive!

Competition: Not all offspring live long enough to reproduce. All the offspring will have to cope with environmental conditions such as temperature, disease, parasites, and predators. If they are to survive, they must compete for limited resources. Those that are best suited for the environment are more likely to survive and pass on their genes.

Evolution Cause #3: GENETIC VARIATION Variation must exist within survivors Ex: Longer legs, bigger claws, diff. fur color Favored traits will stay in population and lead to evolution Adaptive Value: Describes a trait that helps an individual survive in a particular environment value b/c it helps them surviveEX: polar bears have black skin; the black skin has adaptive value b/c it helps them survive

The differences among offspring are due to genetic variation, the unique combination of traits that each organism inherits from its parents. Organisms that reproduce sexually have more variation, than those who reproduce asexually !

Evolution Cause #4: SELECTION BY ENVIRONMENT Traits w/ adaptive value benefit those individuals If reproduce, offspring have traits too Eventually, # of individuals with trait increases, and most all will have it! Therefore, adapting to environment DRIVES EVOLUTION!

Evolutionary (Phylogenic) Trees: Animals = COMMON ANCESTOR

Comparison of Human and Chimp Chromosomes

Variation and Evolution Why differences among a pop’n are good!

To evolve, variations must exist in a species BEFORE the environment changes. They do not get a trait just because it is needed. Click on the peppered moth to see how environmental change drives evolution. 2:05 min

A. Review of Variation Order of DNA bases determines traits Changes can occur that can change individual Two possible ways changes occur: 1.M utations 2.G enetic Shuffling (Recombination)

B. Mutations Are random (cannot be predicted)Are random (cannot be predicted) Caused by radiation and chemicalsCaused by radiation and chemicals To be passed on:To be passed on: Single celled organisms (mitosis)Single celled organisms (mitosis) Sex cells of multicellular organismsSex cells of multicellular organisms

Mutations con’t… Most mutations harmfulMost mutations harmful Some are beneficial (have adaptive value)Some are beneficial (have adaptive value) These get passed onThese get passed on Ex: polar bears probably didn’t always have black skin; mutation caused it and it was beneficialEx: polar bears probably didn’t always have black skin; mutation caused it and it was beneficial THIS IS MAIN SOURCE OF NEW VARIATIONTHIS IS MAIN SOURCE OF NEW VARIATION

C. Genetic Shuffling Sorting and recombination of genes = new combos of genesSorting and recombination of genes = new combos of genes Think deck of cards: deck always the same but each hand is differentThink deck of cards: deck always the same but each hand is different Sexual reproduction uses 2 decks so even more variationSexual reproduction uses 2 decks so even more variation THIS IS MAIN SOURCE OF VARIATION WITHIN A SPECIESTHIS IS MAIN SOURCE OF VARIATION WITHIN A SPECIES

Results of Genetic Variation Types: Structural changesStructural changes Functional changesFunctional changes Behavioral changesBehavioral changes

A. Structural Changes Result of organisms entire historyResult of organisms entire history Ex: polar bears vs other bearsEx: polar bears vs other bears Homologous StructuresHomologous Structures Evolution helps explain structural similaritiesEvolution helps explain structural similarities Ex: (Arm structure) Humans, whales, birds and bats (see RB p88)Ex: (Arm structure) Humans, whales, birds and bats (see RB p88) All have 1 long bone, 2 shorter ones, and 5 digitsAll have 1 long bone, 2 shorter ones, and 5 digits Tells us they all had a common ancestorTells us they all had a common ancestor These are homologous structures!These are homologous structures!

Embryology

Structural Changes con’t 2. Vestigial Structures Structures that are present but no longer in useStructures that are present but no longer in use EX: Snakes contain tiny, non- functional leg bones which suggest it evolved from 4- legged lizardsEX: Snakes contain tiny, non- functional leg bones which suggest it evolved from 4- legged lizards

Vestigial Structures (click link) Vestigial Structures (click link) Hind leg limbs in whales Pelvic bone in humans Appendix in humans

B. Functional Changes Molecular changeMolecular change EX:EX: All muscles produce tiny electric currentAll muscles produce tiny electric current Eels have developed stronger current to help them find food and kill preyEels have developed stronger current to help them find food and kill prey

C. Behavioral Changes Adaptive changes that increase reproductive successAdaptive changes that increase reproductive success EX:EX: Fighting among males to “win” femaleFighting among males to “win” female Rhythms of bird callsRhythms of bird calls Rates blinking in lightning bugsRates blinking in lightning bugs

Importance of Variation 1.Environment changes, organisms have to adapt 2.Without variation, species likely to become extinct 3.If diversity lost, difficult to recover 1.Endangered species have small populations with little variation 2.If environment changes, they cannot adapt

The Rate of Evolution and Extinction What affects how fast organisms evolve? What leads to extinction?

Change is Everything! Change in environment = Change in species! Failure to adapt to changes = possible extinction 

Rate of Evolution What affects how fast a species evolves? 1.Rate of environmenta l change 2.Rate of reproduction

A. Rate of Environmental Change Rapid environmental change = rapid change in speciesRapid environmental change = rapid change in species Rapid changeRapid change Ex. Modern horse: many changes over past million yearsEx. Modern horse: many changes over past million years Slow changeSlow change Ex. Horseshoe crab: nearly identical to ancestors from 300 myaEx. Horseshoe crab: nearly identical to ancestors from 300 mya

Environmental Change con’t: Creation of new species can occur if species are separated by geography such as water or land features. Harris's antelope squirrel inhabits the canyon's south rim (left). Just a few miles away on the north rim (right) lives the closely related white– tailed antelope squirrel. Geographic isolation of squirrels on opposite rims of the Grand Canyon.

B. Rate of Reproduction The # of offspring produced can tell us how quickly a species can evolve Few offspring = longer life = slow evolution Ex. Humans, elephants Many offspring = shorter life = quicker evolution Ex. Bacteria, single celled orgs, fish

Let’s look at bacteria Reproduce very quickly See page 90 figure 5-6 Millions exposed to antibiotic Very good chance a few will have resistant gene due to random mutation These will live, THEN pass on resistance Pretty soon, large population that have this resistance If same antibiotic used again, will increase resistance Soon, a SUPER STRAIN of this bacteria has evolved ml

Refer to RB page 90 figure 5-6 Brain Pop link Brain Pop link

Lesson learned: Only use antibiotics when necessaryOnly use antibiotics when necessary Many strains are resistant to penicillin, the first antibiotic usedMany strains are resistant to penicillin, the first antibiotic used Humans are creating Super Strains with continued misuse of antibioticsHumans are creating Super Strains with continued misuse of antibiotics Similar occurrences with insects and insecticidesSimilar occurrences with insects and insecticides

What causes extinction? 1.Death rate higher than birth rate Usually due to rapid env. changesUsually due to rapid env. changes 2.These env. changes cause major drop in pop’n size if species cannot adapt Variation drops!Variation drops! Less variation to pass onLess variation to pass on Offspring essentially inbreeding, variation drops even moreOffspring essentially inbreeding, variation drops even more NO VARIATION = NO ADAPTIVE VALUE = EXTINCTION