EvolutionEvolution

EvolutionEvolution

• The processesprocesses that have transformed life on earth from it’s earliest formsearliest forms to the vast diversitydiversity that characterizes it today.

• The first life on Earth was most likely simple single cell organisms that appeared about 3 to 3.5 billion years ago.

Evidence of EvolutionEvidence of Evolution

1. Fossil Record:1. Fossil Record:Fossils and the order in which they Fossils and the order in which they

appear appear in layers of sedimentary rock.in layers of sedimentary rock.2. DNA2. DNA

Studying the DNA of different organisms Studying the DNA of different organisms allows scientists to compare those allows scientists to compare those organisms relationship to each other. The organisms relationship to each other. The more similar DNA organisms contain the more similar DNA organisms contain the more closely related they are.more closely related they are.

Fossil Record

• Going down the fossils get older.

• Oldest on the bottom, youngest on the top.

• Can be dated with radioisotopes.

• Because many species become extinct, the only way to see the evolution of a species is through the fossil record.

• The evolution of the horse can be seen through leg and tooth fossils.

60 mya

40 mya

25 mya

7 mya

3 mya

Old Theories of EvolutionOld Theories of Evolution

• Jean Baptiste LamarckJean Baptiste Lamarck (early 1800’s) proposed:

““The inheritance of acquired characteristics”The inheritance of acquired characteristics”

• He proposed that by using or not using its body parts, an individual tends to developdevelop certain characteristicscharacteristics, which it passespasses on to its offspringoffspring.

““The Inheritance of Acquired The Inheritance of Acquired Characteristics”Characteristics”

• Example: Example: A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.

Charles DarwinCharles Darwin

• Influenced by Charles LyellInfluenced by Charles Lyell who published “Principles of Geology”.“Principles of Geology”.

• This publication led DarwinDarwin to realize that natural forces gradually change Earth’s surface and that the forces of the past are still operating in modern times.

Charles DarwinCharles Darwin

• Darwin set sail on the H.M.S. BeagleH.M.S. Beagle (1831-1836) to survey the south seas (mainly South America (mainly South America and the Galapagos Islands)and the Galapagos Islands) to collect plants and animals.

• On the Galapagos Islands, Galapagos Islands, Darwin observed species that lived no where else in the world.

• These observations led Darwin to write a book.

Charles DarwinCharles Darwin• Wrote in 1859Wrote in 1859: “On the Origin of Species by “On the Origin of Species by

Means of Natural Selection”Means of Natural Selection”

• Three main points:Three main points:1.1. Complex organisms develop from Complex organisms develop from simple organisms over a long period of time.simple organisms over a long period of time.2.2. Present day species develop from Present day species develop from earlier species.earlier species.3.3. Some species die out (become extinct) Some species die out (become extinct) when environmental changes occur.when environmental changes occur.

Natural SelectionNatural Selection• IndividualsIndividuals with favorablefavorable traitstraits are more

likely to leave more offspring better suited for their environment.environment.– ““Survival of the Fittest”Survival of the Fittest”

• VariationVariation (genetic difference) (genetic difference) occurs occurs among individuals in a population.among individuals in a population.– Due to meiosis and fertilizationDue to meiosis and fertilization

• More individuals are produced than will More individuals are produced than will survive.survive.– Some organisms produce thousands of Some organisms produce thousands of

offspringoffspring

There must be competition between organisms for natural resources (food, water, space)

These are needed for survival.

Competition keeps the population under control and is a driving force of evolution.

Competition

Highest Rate of Highest Rate of Natural SelectionNatural Selection

• In a changing environment, organisms that exhibit genetic differences due to mutation and genetic recombination show the highest rate of natural selection.

Lowest Rate of Natural Selection

• In a stable environment, organisms tend to exhibit less genetic differences due to mutation and genetic recombination because there is little reason to evolve.

Artificial SelectionArtificial Selection

• The selective breedingselective breeding of domesticated plants and animals by man.

Evidence of EvolutionEvidence of Evolution

1. Taxonomy:1. Taxonomy:

Classification of life forms.Classification of life forms.

2. Homologous structures:2. Homologous structures:Structures that are similar because Structures that are similar because

of of common ancestry common ancestry (comparative (comparative anatomy)anatomy)

Evidence of EvolutionEvidence of Evolution

3. Comparative embryology:3. Comparative embryology:

Study of structures that appear Study of structures that appear during during embryonic development.embryonic development.

4. Molecular biology:4. Molecular biology:

DNA and proteins (amino acids)DNA and proteins (amino acids)

Population GeneticsPopulation Genetics

• The sciencescience of genetic changegenetic change in population.

PopulationPopulation

• A localized group of individualsindividuals belonging to the same speciessame species.

SpeciesSpecies

• A group of populationspopulations whose individualsindividuals have the potential to interbreedinterbreed and produce viableviable offspring.

Gene PoolGene Pool

• The total collection of genescollection of genes in a population at any one time.

MacroevolutionMacroevolution

• The origin of taxonomic groups higher higher than the species levelthan the species level.

MicroevolutionMicroevolution

• A change in a population’s gene poolpopulation’s gene pool over a secession of generations.

• Evolutionary changesEvolutionary changes in species over relatively brief periods of geological timegeological time.– Insects in reaction to pesticides

– Bacteria in reaction to antibiotics

Mechanisms of MicroevolutionMechanisms of Microevolution

Gene Flow:Gene Flow:

TThe gain or loss of genesgain or loss of genes from a population by the movementmovement of individuals or gametes.

• Immigration or emigrationImmigration or emigration.

Mutation:Mutation:Change in an organism’s DNA. Change in sex cells Change in an organism’s DNA. Change in sex cells are passed down to next generation. Change in are passed down to next generation. Change in body cells are not passed down.body cells are not passed down.

- random chance- random chance- mutating agent, ie., chemicals or - mutating agent, ie., chemicals or

radiationradiation

Non-random mating:Non-random mating:The selection of mates other thanThe selection of mates other than by by

chance.chance.- mating behaviors- mating behaviors