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

Variation and Evolution

Why differences among a pop’n are good!

Review of VariationReview of Variation

Order of DNA bases determines traitsOrder of DNA bases determines traits Changes can occur that can change Changes can occur that can change

individualindividual Two possible ways changes occur:Two possible ways changes occur:

1.1. MutationsMutations

2.2. Genetic Shuffling (Recombination)Genetic Shuffling (Recombination)

MutationsMutations

Are random (cannot be Are random (cannot be predicted)predicted)

Caused by radiation and Caused by radiation and chemicalschemicals

To be passed on:To be passed on: Single celled orgs (mitosis)Single celled orgs (mitosis) Sex cells of multicellular Sex cells of multicellular

orgsorgs

Mutations con’t…Mutations con’t… Most mutations harmfulMost mutations harmful Some are beneficial (have adaptive Some are beneficial (have adaptive

value)value) These get passed on These get passed on Ex:Ex: polar bears prob didn’t polar bears prob didn’t

always have black skin; mutation always have black skin; mutation caused it and it was beneficialcaused it and it was beneficial

THIS IS MAIN SOURCE OF THIS IS MAIN SOURCE OF NEWNEW VARIATIONVARIATION

Genetic ShufflingGenetic Shuffling

Sorting and recombination of genes = Sorting and recombination of genes = new combos of genesnew combos of genes

Think deck of cardsThink deck of cards: : deck always the deck always the same but each hand is differentsame but each hand is different

Sexual reprod. uses 2 decks so even Sexual reprod. uses 2 decks so even more variationmore variation

THIS IS MAIN SOURCE OF VARIATION THIS IS MAIN SOURCE OF VARIATION WITHIN A SPECIESWITHIN A SPECIES

Results of Genetic Results of Genetic VariationVariation1.1. Structural changesStructural changes

2.2. Functional changesFunctional changes

3.3. Behavioral changesBehavioral changes

Structural ChangesStructural Changes Result of orgs entire historyResult of orgs entire history

Ex:Ex: polar bears vs other bears polar bears vs other bears

1.1. Homologous StructuresHomologous Structures• Evolution helps explain structural similaritiesEvolution helps explain structural similarities Ex:Ex: (Arm structure) Humans, whales, birds (Arm structure) Humans, whales, birds

and bats (RB p88)and bats (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!

EmbryologyEmbryology

Structural Changes Structural Changes con’tcon’t

2. 2. Vestigial StructuresVestigial Structures• Structures that are present but Structures that are present but

no longer in useno longer in use• EX:EX: Snakes contain tiny, non- Snakes contain tiny, non-

functional leg bones which functional leg bones which suggest it evolved from 4-suggest it evolved from 4-legged lizardslegged lizards

Vestigial Structures(click link)

Hind leg Hind leg limbs in limbs in whaleswhales

Pelvic Pelvic bone in bone in humanshumans

Appendix Appendix in humansin humans

Functional ChangesFunctional Changes Molecular changeMolecular change

EX:EX: All muscles produce tiny electric All muscles produce tiny electric

currentcurrent Eels have developed stronger Eels have developed stronger

current to help them find food and current to help them find food and kill preykill prey

Behavioral ChangesBehavioral Changes

Adaptive changes that increase Adaptive changes that increase reproductive successreproductive success

EXEX:: Fighting among males to “win” Fighting among males to “win”

femalefemale Rhythms of bird callsRhythms of bird calls Rates blinking in lightning bugsRates blinking in lightning bugs

Importance of VariationImportance of Variation

1.1. Environment changes, orgs have to Environment changes, orgs have to adaptadapt

2.2. Without variation, species likely to Without variation, species likely to become extinctbecome extinct

3.3. If diversity lost, difficult to recoverIf diversity lost, difficult to recover1.1. Endangered species have small pop’ns with Endangered species have small pop’ns with

little variationlittle variation

2.2. If environment changes, cannot adaptIf environment changes, cannot adapt

$2 SUMMARY OF THE $2 SUMMARY OF THE IMPORTANCE OF IMPORTANCE OF VARIATION in EVOLUTIONVARIATION in EVOLUTION

Each word is worth Each word is worth $.05$.05 Freebies:Freebies:

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