variation and evolution
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Variation and Evolution. Why differences among a pop’n are good!. Review of Variation. Order of DNA bases determines traits Changes can occur that can change individual Two possible ways changes occur: Mutations Genetic Shuffling (Recombination). Mutations. - PowerPoint PPT PresentationTRANSCRIPT
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:
a the as if and of in is a the as if and of in is it so by for to it so by for to