Evolution

EvolutionEvolution

What is Evolution?What is Evolution?

EvolutionEvolution - - how modern day organisms how modern day organisms have changed from ancient have changed from ancient organisms.organisms.

- - gradual gradual “change over time”“change over time”

Charles DarwinCharles Darwin

Collected data and Collected data and observations to create observations to create hypothesis about hypothesis about evolution.evolution.

Published Published On the Origin of On the Origin of SpeciesSpecies containing his containing his theory of evolutiontheory of evolution..

Darwin’s ObservationsDarwin’s ObservationsHe visited many continents while He visited many continents while

serving on the ship H.M.S serving on the ship H.M.S Beagle.Beagle.

He noticed a great He noticed a great diversity diversity (variety)(variety) in in organisms (species)organisms (species) on these different on these different continentscontinents..

Australia – Australia – KangaroosKangaroos

Galapagos – Galapagos – Giant Tortoises and Giant Tortoises and FinchesFinches

SpeciesSpecies

SpeciesSpecies – – a group of organisms that can a group of organisms that can reproduce and create offspring that reproduce and create offspring that can reproduce.can reproduce.

Who Survives?Who Survives?Natural SelectionNatural Selection – – those individuals those individuals

who have favorable variations (from who have favorable variations (from their genes) are able to survive and their genes) are able to survive and reproduce successfully.reproduce successfully.

Conditions for Natural Conditions for Natural SelectionSelection

1.1. Overproduction Overproduction – – every species every species produces more individuals than will produces more individuals than will survive.survive.

Ex: Ex: insects, fish, dandelionsinsects, fish, dandelions

2.2. Struggle for Survival Struggle for Survival – – individuals individuals within a species will compete for within a species will compete for resources.resources.

- Ex: - Ex: environmental environmental conditions: food, conditions: food, space, space, water, etc.water, etc.

3.3. Adaptation (adaptive value) Adaptation (adaptive value) – – any any genetic trait that helps an organism genetic trait that helps an organism survive, compete, and reproduce survive, compete, and reproduce better than others.better than others.

- Ex: - Ex: Grasshoppers with longer legsGrasshoppers with longer legs

Lions with sharper teethLions with sharper teeth

Where Do Variations Come Where Do Variations Come From?From?

Genetic variationsGenetic variations can only be passed can only be passed on if they occur in on if they occur in gametegamete cells cells..

Sources of variation:Sources of variation:

a. Mutationa. Mutation – – change in DNA bases.change in DNA bases.

- - Some are “good” and can be Some are “good” and can be passed onpassed on..

b. Sexual Reproductionb. Sexual Reproduction – – crossing crossing over of chromosomes and sexual over of chromosomes and sexual recombination (fertilization) recombination (fertilization) increases variety in offspring.increases variety in offspring.

Mutations occur at random – “good” Mutations occur at random – “good” ones will become popular and ones will become popular and passed on.passed on.

4.4. Survival of the FittestSurvival of the Fittest – – individuals who have certain individuals who have certain variations will be able to survive if variations will be able to survive if environment changes.environment changes.

- Ex: - Ex: Disease and Disease and resistance/immunityresistance/immunity

5.5. Speciation Speciation – – those individuals that those individuals that survived to reproduce, may develop into a survived to reproduce, may develop into a new species.new species.

How does it happen?How does it happen?

Reproductive isolationReproductive isolation – – a population may a population may become separated by a geographical become separated by a geographical barrier.barrier.

- Ex: - Ex: River, mountain range, earthquake, River, mountain range, earthquake, oceanocean

Many new species of finches develop from Many new species of finches develop from isolation.isolation.

Differences in beak sizes/shapesDifferences in beak sizes/shapes result result from different environments (food from different environments (food sources).sources).

Examples of Natural Examples of Natural SelectionSelection

1.1. Peppered Moth EvolutionPeppered Moth Evolution

Change in moth color from white to black Change in moth color from white to black due to change in their environment from due to change in their environment from white to black.white to black.

Black moth color = Black moth color = “favorable” mutation“favorable” mutation

2.2. Antibiotic ResistanceAntibiotic Resistance

Antibiotics – Antibiotics – kill bacteria with diseases.kill bacteria with diseases.

Through natural selection, some bacteria Through natural selection, some bacteria mutatemutate and become and become resistant (not resistant (not affected)affected) to to antibioticsantibiotics. .

These These resistant resistant bacteria bacteria multiply multiply (asexually)(asexually) and soon become the only and soon become the only bacteria around.bacteria around.

New antibiotics must now be made.New antibiotics must now be made.

http://www.pbs.org/wgbh/evolution/library/http://www.pbs.org/wgbh/evolution/library/10/4/l_104_03.html10/4/l_104_03.html

Red Bacteria have mutation for resistance

After Treated with Antibiotic

Only Red Bacteria survive and pass on good mutation

Evidence of EvolutionEvidence of Evolution

1.1. Similarities in DNA and ProteinsSimilarities in DNA and Proteins Proteins from 2 different species may have Proteins from 2 different species may have

similar amino acid sequences.similar amino acid sequences.- Ex: - Ex: Humans and Chimpanzees share Humans and Chimpanzees share

same protein for blood which differs by only 1-2 same protein for blood which differs by only 1-2 amino acids.amino acids.

2.2. Similarities in Similarities in Embryo DevelopmentEmbryo Development

Early stages of embryos in Early stages of embryos in many animals is very many animals is very similar.similar.- - DifferentiationDifferentiation happens the happens the same way in many organisms.same way in many organisms.

- Suggests we come from a - Suggests we come from a common ancestorcommon ancestor..

3.3. Homologous Body Homologous Body StructuresStructures

Similarities in Similarities in forelimb bones forelimb bones of different animal species:of different animal species: wing of a bat, flipper of a wing of a bat, flipper of a whale, arm of a human.whale, arm of a human.- - Bones are attached in similar Bones are attached in similar placesplaces all came from a all came from a common ancestorcommon ancestor..

Vestigial structuresVestigial structures – – organs that organs that serve no function in an organism.serve no function in an organism.

- may have been useful in the past.- may have been useful in the past.

- Ex: - Ex: human appendix, leg bones in human appendix, leg bones in whalewhale

4.4. Fossil Record Fossil Record – – fossils from different fossils from different layers of the earth show species have layers of the earth show species have changed over time.changed over time.

- The earth is approximately - The earth is approximately 4.7 billion 4.7 billion years oldyears old..

Origin of LifeOrigin of LifeFirst organisms were First organisms were single-celled (bacteria).single-celled (bacteria).

As time went on, more As time went on, more complex multicellular complex multicellular organismsorganisms developed. developed.

Now, the Now, the most complex multicellular organismsmost complex multicellular organisms (humans) have evolved.(humans) have evolved.

ExtinctionExtinction

ExtinctionExtinction - - Disappearance of species Disappearance of species from the earth.from the earth.- Species cannot - Species cannot adaptadapt to to changing changing environmentenvironment..

- Natural disaster (meteor)- Natural disaster (meteor)

- Bottom - Bottom layers=layers=oldeoldest st (simplest)(simplest)

- Top layers - Top layers = = most most recent recent (more (more complex)complex)

Phylogenetic (Family) TreesPhylogenetic (Family) TreesFamily TreeFamily Tree - - Simple diagram used Simple diagram used

to show relationships and common to show relationships and common ancestors amongst species.ancestors amongst species.

A B C D

F

E

G

Past

Present

E is a common ancestor to both B and C!

Family Tree

Punctuated EquilibriumPunctuated EquilibriumPunctuated EquilibriumPunctuated Equilibrium – –

long, stable periods of long, stable periods of equilibrium interrupted by equilibrium interrupted by rapid change (due to rapid change (due to mutations).mutations).

- Different speeds of evolution - Different speeds of evolution for different species.for different species.