Evolution Video Topic 5 Evolution Main Idea How

Evolution Video

Topic 5 – Evolution Main Idea: How have species changed over time? (long periods of time) [It is important to realize that evolution is a theory based on scientific evidence that may conflict with some religious beliefs]

I. Darwin and Mechanisms of Evolution The 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 bya • Prokaryotes then Eukaryotes then multicellular Eukaryotes • Fossil record determines: • When species appeared • The type of environment • When/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 theory of evolution say? • Theory b/c lots of evidence • Tested and re-tested by many scientists • States that: • Variations in individuals leads to changes in whole species

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. 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). Pg 81 fig 5 -2

Natural Selection: The Idea Behind the Theory brain pop video 3: 44 • Evolution controlled by NATURAL processes • THE PROCESS IS: LIVE + BREED + PASS ON GENETIC INFO = SURVIVAL OF SPECIES • “Survival of Fittest” • Those best ADAPTED will be able to DO THE PROCESS

Results of Natural Selection • Short term result: • Best fit (adapted) will pass on GOOD genes to offspring • Long term result: • Change 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 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. Only some live to reproduce 2. Competition for resources 3. Best 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 • EX: polar bears have black skin; the black skin has adaptive value b/c it helps them survive

Pg 83 fig 5 -5 • 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

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

II. Variation and Evolution Why differences among a population are good!

A. Review of Variation • Order of DNA bases determines traits • Changes can occur that can change individual • Two possible ways changes occur: 1. Mutations 2. Genetic Shuffling (Recombination)

B. Mutations • A change in the base sequence of a DNA molecule • Are random (cannot be predicted) • Caused by radiation and chemicals • To be passed on: • Single celled organisms (mitosis) • Sex cells of multicellular organisms

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

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

Results of Genetic Variation Types: • Structural changes • Functional changes • Behavioral changes

A. Structural Changes • Result of organisms entire history; visible • Ex: polar bears vs other bears

1. Homologous Structures see RB p 88 • Evolution helps explain structural similarities • Ex: (Arm structure) Humans, whales, birds and bats • All have 1 long bone, 2 shorter ones, and 5 digits • Tells us they all had a common ancestor • These are homologous structures!

Embryology

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

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

B. Functional Changes • Affects how an organism works • Molecular change • EX: • All muscles produce tiny electric current • Eels have developed stronger current to help them find food and kill prey

WRITE THIS DOWN DNA SEQUENCING

C. Behavioral Changes • Adaptive changes that increase reproductive success • EX: • Fighting among males to “win” female • Rhythms of bird calls • Rates 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

III. 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 environmental change 2. Rate of reproduction

A. Rate of Environmental Change • Rapid environmental change = rapid change in species • Rapid change • Ex. Modern horse: many changes over past million years • Slow change • Ex. 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. Geographic isolation of squirrels on opposite rims of the Grand Canyon. 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.

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 organisms, 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

Refer to RB page 90 figure 5 -6 http: //www. sumanasinc. com/scienceinfocus/sif_antibiotics. html

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

Brain Pop link Antibiotic resistance Watch the video and complete the quiz

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