EVOLUTION!

Summing it all up!

•In science, theories are statements or models that have been tested and confirmed many times.

What is Scientific Theory?

In science, the term "Theory" does not express doubt.

•They explain a wide variety of data and observations

•They can be used to make predictions

•They are not absolute, can be changed as new evidence is found

The theory of evolution is considered a UNIFYING THEORY of Biology, because it answers many questions and offers an

explanation for observations

•Charles Darwin developed the THEORY OF EVOLUTION BY NATURAL SELECTION

 

•explained how organisms changed over time  (ADAPTED)

History of Evolution

•Lamarke's Theory of Acquired Characteristics

•Some thought that you would gain or lose features if you overused or didn't use them,

• PROVEN TO BE WRONG!

Acquired Characteristics

Macroevolution: Evolution of a New Species

Levels of Evolutionary Study• Microevolution: examines changes to the

genes (alleles) within populations– Population Genetics: studies the changes in

the numbers & types of alleles in a population• Examines evolution within a species.• Small changes that do not lead to new species, but

can lead to new variations.

• Macroevolution: examines the evolutionary changes that create new species– Speciation: the formation of new species

over time

•Species: a group of organisms that can interbreed and produce fertile offspring

•Speciation: the evolution of new speices (by genetic change or change in form)– Occurs when members of a

similar populations can no longer interbreed!

Macroevolution

Methods of Speciation• Geographic Isolation: physical barriers

divide a population and prevent interbreeding

Beetles in Grassland Become Green

Beetles in Woody Habitat Become Brown

Methods of Speciation• Reproductive Isolation--occurs when formerly

interbreeding organisms can no longer mate & produce fertile offspring– Genetic: genetic differences are too great to breed

successfully– Behavioral: mating behaviors or mating seasons

don’t allow for mating• Chromosome Numbers

– Polyploidy: any species with extra sets of chromosomes. Common in plants.• Can interbreed or self-fertilize, forming separate

species– Hybridization: when two closely related species

attempt to mate• Usually results in sterile offspring • Ex: donkey + horse = mule

Speed of Speciation

• Gradualism– Idea that species originate thru a slow,

gradual change of adaptations over long periods of time

• Punctuated Equilibrium– Idea that species can remain stable for long

periods of time until environmental changes cause many new species to appear • Speciation occurs in less than 10,000 years!

• Species diverge or become increasingly distinct from one ancestral species

• Ex: Darwin’s finches

• Also called adaptive radiation

Patterns of Macroevolution: Divergent Evolution

Patterns of Macroevolution: Convergent Evolution• Process by which unrelated species

become similar as they adapt to similar environments

Ostrich

Africa

Emu

Australia

Rhea

South America

Patterns of Macroevolution: Coevolution

• When species who live in close contact evolve adaptations to one another’s existence.

Extinction!• When all the members of a species die

off or fail to reproduce– Estimated that 99% of all species that ever

lived have become extinct– Most extinctions are the

result of environmental change, can cause well adapted species to becomepoorly adapted!

– If the environment changes faster than a species can adapt, extinction can result!

Microevolution

Processes of Microevolution•Microevolution examines the

processes by which inherited traits change over time in a population

– Natural Selection– Migration– Mate Choice– Mutation– Genetic Drift

Processes of Microevolution

• Natural Selection: changes in environmental pressures can cause an increase or decrease in certain alleles (traits) in a population– Favorable alleles stay in population (selected for)– Unfavorable alleles are eliminated (selected

against)

• Migration: as organisms move from one population to another, their genes move with them– Causes the numbers and types of alleles within

each population to change.

Processes of Microevolution• Mate Choice: if parents are selective (picky)

or limited in their choice of mates, only a limited set of traits will be passed on

• Mutation: can add a new allele to a population – Mutations are rare, and must occur in egg or

sperm to be passed on

• Genetic Drift: population sizes affect the change in alleles (traits) in a population– Large populations experience slower changes in

alleles– Smaller populations can change more quickly

Microevolution: Changes within Populations

Populations evolve NOT individuals evolve

Natural selection works on the phenotypes within a population

Individuals cannot evolve within their lifetime, because they cannot evolve a new phenotype due to a change in the environment

Evolution is brought about by breeding that occurs between organisms within a population. Natural selection maintains favorable (useful) genotypes, and eliminates unfavorable (not useful) genotypes.

- Explains how organisms change over time

Natural Selection

1.1.Over ProductionOver Production:: Most organisms produce more offspring than will survive

2.2.VariationVariation:: Members of the population have variations

3.3.SelectionSelection:: Certain variations will increase the likelihood of survival

4.4.AdaptationAdaptation:: Over-time organisms with that variation make up most of the population and may look different than their ancestors

Patterns of Natural Selection

Stabilizing selection:

Favors average individuals; reduces variation

Directional selection:

Favors EXTREME variations; evolution is fast

Disruptive selection:

Favors two extreme variations; no intermediate and eventually two species.

Stabilizing Selection• “Average” individuals are better able to survive

• Alleles for the “extreme” are eliminated

• A narrow range of phenotypes is favored resulting in a narrow bell shaped curve

Directional Selection

• ONE extreme is favorable, but other is not

• Alleles for other extreme and normal phenotypes become less common in the population

• Results in FAST evolution!

• Bell curve is shifted off of center

Disruptive Selection

• BOTH extremes are favorable!

• Results in increasingly distinct phenotypes, the “normal” phenotype is selected against

• Bell curve is‘disrupted’ and pushed apart into two peaks

Evidence for Evidence for EvolutionEvolution

Evidence for EvolutionEvidence for Evolution

• Fossils– provide a record of

early life & evolutionary history

– Currently, the fossil record is incomplete (like a jigsaw puzzle w/ missing pieces)

– The more fossils discovered, the clearer the evolutionary picture becomes!

Evidence for EvolutionEvidence for Evolution

• Biogeography– The study of the locations of

organisms around the world– Organisms in similar

environments have similar adaptations despite being on completely different continents. •Ex: Large, flightless birds

• Anatomy– the way an organism is put

together

– Homologous structures– Analogous Structures– Vestigial Structures

Evidence for EvolutionEvidence for Evolution

Homologous StructuresHomologous Structures

• Parts with a common evolutionary history– Ex: Organisms that have the same basic

skeleton, bones are just modified for different functions

– It would be unlikely for so many animals to have similar structures if each species arose individually!

Analogous StructuresAnalogous Structures

• Body parts that are similar in function, but not evolutionary origin

• Ex: Wings of a butterfly & wings of a bird

Vestigial Structures• Body structure that has no function in

present day organisms, but was probably useful to an ancestor

• Ex: Eyes on Naked Mole Rats, Appendix in humans, Wings on ostrich

Evidence for Evolution• Adaptations: Structural

– Develop over many generations (ex: claw length, fur color, etc)

•Mimicry: enables one species to resemble another species. Monarchs and Viceroys

•Camouflage: enables species to blend in with their surroundings

MonarchTOXIC!

ViceroyTASTY!

Evidence for EvolutionEvidence for Evolution• Adaptations:

Physiological– Changes in an organisms

metabolic processes (occurs more rapidly) • Bacteria’s resistance to

antibiotics

• Insects / weeds resistance to certain pesticides

Evidence for EvolutionEvidence for Evolution• Embryological

– similarities between young embryos suggest evolution from a distant common ancestor

Evidence for EvolutionEvidence for Evolution

• Biochemical– Provides info about

relationships between individuals and species

– Uses RNA & DNA sequences to construct cladograms (evolutionary diagrams)