EVOLUTION

EVOLUTION

WHAT IS EVOLUTION?To evolve: to changeA theory stating that all life has changed from simpler life to more complex lifeOccurs over LONG periods of timeEvolution often supports that organisms have evolved from a common ancestor

The theory of evolutionThe most common theory accepted by scientists today was tested in 1953 by Stanley Miller and Harold Urey. Their apparatus simulated conditions on early Earth.It showed that chemical reactions created amino acids (organic compounds represented life).

The theory of evolutionJean-Baptist Lamark was a French naturalist who recognized that things change over time. His explanations were:Tendency towards perfectionUse and disuse= if you use it, you keep it; if you dont, you lose itInheritance of acquired traits= traits are passed down through generations

Problem with his theoryhe didnt understand HOWCharles DarwinDarwin was a naturalist that traveled on the HMS Beagle to the Galapagos Islands in the Pacific Ocean.He observed many different plants and animals to include giant tortoises and finches.He noticed that the birds had different shaped beaks and he hypothesized that this had something to do with their diet.

evolutionArtificial Selection- process by which we select the best organisms to mate and produce offspring; we are selecting for specific traitsEx. Breeding dogs, cats, livestock, etcStruggle for existence- there is regular competition for the resources (food, space, etc.) necessary for living which leads to the concept ofSurvival of the fittest- only the organisms who have the traits that make them better suited for their environment will survive, reproduce and have offspring that survive.EvolutionNatural selection- a.k.a., survival of the fittest, nature (the environment) will select the organisms that will survive through the challenges they face day-to-day.Descent with modification- generations are modified from their ancestors due to natural selection

Theory of natural selectionVariation exists within a populationVariation is inheritedResources are limitedMore organisms are produced than will surviveThe organisms that are best suited for the for the environment will survive and produce offspring.

Support of Darwins Theories1. Fossil record2. Geographic distribution of living things3. Homologous body structures4. Vestigial Structures5. Similarities in embryology6. Biochemical similarities

1. FOSSIL EVIDENCEThe fossil record shows that life HAS changed over time,Fossils: remains of organisms that lived in the pastEx. Imprints/bones/teeth/preserved insectsForm in sedimentary rock and the weight of the subsequent layers turns the organisms into rockIndicate change (see what organism looked like then compared to now; see organisms that lived in past but no longer exist today

Older fossils will be deeper in sedimentLayers are deposited over time on top of the older layerFossils show that organisms have evolved from SIMPLER organisms (bacteria, invertebrates) in the lower layers to more COMPLEX organisms (vertebrates: fishreptilesmammals) in the upper layersEX: a magnolia (flowering plant)would be younger than a fern

A squid (invert) would be older than a lizard (reptile)EVIDENCE FROM FOSSILSHow has the horse changed over time?

How would studying the fossil evidence of the horse support the theory of evolution?

The fossil evidence shows that the horse has changed over time in height, teeth structure, and bone structure12What would this fern fossil tell us about climate?

This fossil was found in Antarctica.

How could Antarctica have the type of climate suggested by this fossil evidence?If it had been closer to Equator;PangaeaAntarctica must have been a warmer climate; ferns are tropical plantsDatingRelative dating- age of the fossil is determined by comparing it to stratified rock around it.Absolute dating- provides a fairly precise date; uses radioactive elements, also known as carbon-14 datingUses the half-life of the element- this is the amount of time it takes for half of the sample to decay

2. Geographic distributionGeographic distribution of living things- similar but unrelated speciesThese 2 crocodiles were found on separate continents.

3. Homologous body structures

Homologous body structures- these are structures that are built the same but may be used differentlySuggests common ancestry Ex. The wing of a bird and the arm of a humanHOMOLOGOUS STRUCTURES

Leg of dogArm of humanWing of birdFlipper of whale

All have similar bone structure, but the function is different (leg-walking; arm-carrying; wing-flying; flipper-swimming)EXAMPLES4. VESTIGIAL STRUCTURES

Structures present, but have no purposeStructures that are incompleteThe presence of these structures indicates the structure once had a purpose (support for evolution)

EX: femur/ pelvis in whales, appendix in humans

Vestigial Structures in Humans

5. EMBRYONIC similarities

EMBRYO: early stage of development of living thingsMany organisms look similar very early in their developmentMore stages similar the more closely related they areSuggests common ancestry (note how similar these different organisms are in early stages)

6. BIOCHEMICAL EVIDENCEBIOCHEMICAL evidence is referring to similarities in DNA, proteins, amino acids, enzymes, etc.The more similar these compounds are in different organisms, the more closely related they areSuggests common ancestryBIOCHEMICAL SIMILARITIES OF ORGANISMS

Comparison of Organisms

% substitutions of amino acids in Cytochrome C

Two orders of mammals

5-10 %

Birds vs. mammals

8-12 %

Amphibians vs. birds

14-18 %

Fish vs. Land vertebrates

18-22 %Insects vs. vertebrates

27-34 %

Algae vs. animals

57 %

Biochemical EvidenceWe are most similar/ most closely related to chimpleast similar/ closely related to chickenHedgehog is most similar to mouse based on the closeness of the DNA similarities3% differenceNatural SelectionHow does natural selection result in a new species?Variation in a population comes from sexual reproduction and from different types within the species mating.Gene pool- all genes that are present in a population

Natural Selection & Polygenic TraitsDirectional Selection- individuals at one end of the curve have a higher fitness than those at any other position

Stabilizing selection- individuals in the middle have a higher fitness

Disruptive selection- individuals at the ends have a higher fitness than those in the middle

Genetic DriftA random change in genetic frequency. Just by chance some organisms will produce more offspring than others; this can lead to a trait becoming more common in the population.

Forming New SpeciesWhat can lead to the formation of a new species?Behavioral isolation- 2 populations do not mate because of differences in courtship behavior, vocalizations, etc.Geographic isolation- 2 populations do not mate because they are separated by a physical barrierImmigration and emigration- individuals are introduced to a new location and are allowed to mateMigration- similar to immigration and emigration; just occurs seasonally and may not result in new mating partnersPatterns of evolutionDivergent evolution (adaptive radiation)- a single species evolves into many through a variety of changes in the environmentSupported by DNA and/or protein structuresEx. Monkey foot and human footConvergent evolution- different organisms become more alike over time due to being in the same environmentSupported by homologous structuresEx. Bird wing and bat wingCo-evolution- organisms need each other for survival therefore will evolve togetherEx. Bumblebees and flowers