EVOLUTION Evolution: genetic change in a population of organisms over time Macroevolution (large-scale) Macroevolution (large-scale) Origins of new species and life forms as well as extinctions Origins of new species and life forms as well as extinctions Microevolution (small scale) Microevolution (small scale) Changes in gene frequencies within a species Changes in gene frequencies within a species

Jean-Baptiste Lamarck Proposed that variation is created within a species based on life experiences (acquired characteristics) which can then be inherited by offspring EXAMPLE: Key: Change is driven by an inner “need” or desire! If you work hard enough, you will have the trait and pass it on!

Charles Darwin In 1831, Charles Darwin took on the role of naturalist of the ship HMS Beagle In 1831, Charles Darwin took on the role of naturalist of the ship HMS Beagle The Beagle set sail on a five-year navigational trip around the world The Beagle set sail on a five-year navigational trip around the world Charles Darwin ( )

Darwin’s Trip Darwin studied a wide variety of plants and animals across the globe, particularly on the Galapagos Islands Darwin studied a wide variety of plants and animals across the globe, particularly on the Galapagos Islands In 1859, he published his book On the Origin of Species In 1859, he published his book On the Origin of Species In it he proposed that evolution occurs through natural selection In it he proposed that evolution occurs through natural selection

Darwin’s Evidences for Natural Selection Fossils of extinct species resembled living species in the same area Fossils of extinct species resembled living species in the same area Galapagos finches differed slightly in appearance but resembled those on the S. American mainland Galapagos finches differed slightly in appearance but resembled those on the S. American mainland He believed it was “descent with modification” from a common ancestor (AKA evolution!) He believed it was “descent with modification” from a common ancestor (AKA evolution!)

Darwin’s Book & Wallace Darwin drafted a preliminary transcript of his book in 1842 Darwin drafted a preliminary transcript of his book in 1842 However, he shelved it for 16 years, probably because of its controversial nature However, he shelved it for 16 years, probably because of its controversial nature Alfred Russel Wallace ( ) independently developed a similar theory to Darwin’s Alfred Russel Wallace ( ) independently developed a similar theory to Darwin’s Correspondence between the two spurred Darwin to publish his theory in 1859 Correspondence between the two spurred Darwin to publish his theory in 1859

Natural Selection Natural Selection refers to the differential reproduction of genotypes caused by factors in the environment More simply put… factors in the environment, such as climate, competition for food, or predators, affect which organisms will survive and therefore reproduce to pass on their genes

Steps of Natural Selection 1. Gene variation exists among individuals in a population (some are “fitter” than others) 1. Gene variation exists among individuals in a population (some are “fitter” than others) 2. This variation can be passed to offspring (variation is due to differences in DNA) 2. This variation can be passed to offspring (variation is due to differences in DNA) 3. All populations overproduce offspring (not all will live) 3. All populations overproduce offspring (not all will live) 4. Individuals with traits that aid survival and reproduction have a better chance of contributing to the next generation (those that will live will have babies!) 4. Individuals with traits that aid survival and reproduction have a better chance of contributing to the next generation (those that will live will have babies!) 5. Over time, the population changes such that the traits of the more successful reproducers are more prevalent (those that live pass on their traits that made them more successful in the first place!) 5. Over time, the population changes such that the traits of the more successful reproducers are more prevalent (those that live pass on their traits that made them more successful in the first place!)

Natural Selection Adaptation: changes that increase the likelihood of survival and reproduction of particular genetic traits in a population

The Rate of Evolution Different kinds of organisms evolve at different rates Different kinds of organisms evolve at different rates Ex: Bacteria evolve much faster than eukaryotes The rate of evolution also differs within the same group of species The rate of evolution also differs within the same group of species In punctuated equilibrium, evolution occurs in spurts In punctuated equilibrium, evolution occurs in spurts In gradualism, evolution occurs in a gradual, uniform way In gradualism, evolution occurs in a gradual, uniform way

a) Punctuated equilibriumb) Gradualism Scientists still debate as to which happens… there seems to be evidence for both!

Evidence for Evolution Evidence for evolution comes from the following Evidence for evolution comes from the following Fossil record Fossil record Molecular record Molecular record Anatomical record Anatomical record

Fossil Record Fossils are the preserved remains, tracks, or traces of once-living organisms Fossils are the preserved remains, tracks, or traces of once-living organisms They form when organisms become buried in sediment and calcium in hard surfaces mineralizes They form when organisms become buried in sediment and calcium in hard surfaces mineralizes Arraying fossils according to age often provides evidence of successive evolutionary change Arraying fossils according to age often provides evidence of successive evolutionary change

Fossils…how to put in order? Relative Age: Looked at the fossils pulled from the ground…Law of Superposition states that the farther down it is, the older it is Relative Age: Looked at the fossils pulled from the ground…Law of Superposition states that the farther down it is, the older it is Absolute Age: Use radioactive isotopes to find the precise age (fossil dating) Absolute Age: Use radioactive isotopes to find the precise age (fossil dating)

Fossils have been found linking all the major groups Fossils have been found linking all the major groups The forms linking mammals to reptiles are particularly well known The forms linking mammals to reptiles are particularly well known

Embryology All organisms in their early developmental patterns look similar…links to a common ancestor?

Anatomical Record Looking at the anatomy of organisms shows similarities… Looking at the anatomy of organisms shows similarities… Homologous structures Homologous structures Built of the same basic components, but serve different functions Built of the same basic components, but serve different functions

Anatomical Record Analogous structures Analogous structures Different anatomical structures and ancestors, but the structures serve the same purpose Different anatomical structures and ancestors, but the structures serve the same purpose

Anatomical Record Vestigial organs Vestigial organs Structures that are no longer in use, but still present Structures that are no longer in use, but still present

DNA Evidence Evolutionary changes involve a continual accumulation of genetic changes Evolutionary changes involve a continual accumulation of genetic changes Distantly-related organisms accumulate a greater number of evolutionary differences than closely- related ones Distantly-related organisms accumulate a greater number of evolutionary differences than closely- related ones Compare the DNA sequences among organisms! The most closely related organisms have more similar DNA sequences! Compare the DNA sequences among organisms! The most closely related organisms have more similar DNA sequences! **BEST EVIDENCE!!**

DNA Evidence The greater the evolutionary distance The greater the number of amino acid differences

Patterns of Evolution 1. Coevolution: long term, evolutionary adjustment of organisms to each other Example: flowers and their pollinators Example: flowers and their pollinators

Patterns of Evolution 2. Convergent Evolution: organisms that have NO common ancestry look similar due to the environment in which they live Example: sharks and dolphins (analogous structures) Example: sharks and dolphins (analogous structures) 3. Divergent Evolution: organisms that HAVE a common ancestry, but look different due to the environment in which they lives Example: finches! Example: finches!

Back to Natural Selection… Fitness: an organism’s fitness describes how well that organism will survive and reproduce Fitness: an organism’s fitness describes how well that organism will survive and reproduce Artificial Selection: the intentional reproduction of specific individuals in a population Artificial Selection: the intentional reproduction of specific individuals in a population Example: purebred dogs, horses, crops, etc. Example: purebred dogs, horses, crops, etc.

Patterns of Natural Selection Directional Selection: One phenotype is more favorable; allele frequency shifts in one direction Directional Selection: One phenotype is more favorable; allele frequency shifts in one direction Example: Peppered Moth! Light colored was favored before Industrial Revolution. After, there was a lot of soot in the air, darker moths became favored. The gene frequency shifted in favor of dark moths!

Patterns of Natural Selection Stabilizing Selection: population becomes less varied and more normalized Stabilizing Selection: population becomes less varied and more normalized Example: Human birth weights! Babies weighing between pounds at birth have the highest survival rate (98.5%). Anything below or above this drops the survival rate. Birth weight is now stabilized around 8 lbs.

Patterns of Natural Selection Disruptive Selection: extreme values for a trait are favored over intermediates Disruptive Selection: extreme values for a trait are favored over intermediates Example: Think of fish! If you are small, you can hide. If you are large, you can scare away predators or threats. If you are the intermediate size…you’ll be eaten.

Hardy-Weinberg Equilibrium Genetic variation in populations puzzled scientists Genetic variation in populations puzzled scientists Dominant alleles were believed to drive recessive alleles out of populations Dominant alleles were believed to drive recessive alleles out of populations In 1908, G. Hardy and W. Weinberg pointed out that in large populations with random mating, allele frequencies remain constant In 1908, G. Hardy and W. Weinberg pointed out that in large populations with random mating, allele frequencies remain constant Dominant alleles do not, in fact, replace recessive ones Dominant alleles do not, in fact, replace recessive ones

Hardy-Weinberg Equilibrium Hardy-Weinberg Equilibrium: A state in which genotype frequencies and ratios remain constant from generation to generation and in which genotype frequencies are a product of allele frequencies Hardy-Weinberg Equilibrium: A state in which genotype frequencies and ratios remain constant from generation to generation and in which genotype frequencies are a product of allele frequencies A population that is in Hardy-Weinberg equilibrium is NOT evolving, meaning: A population that is in Hardy-Weinberg equilibrium is NOT evolving, meaning: 1. Large population size 2. Random mating 3. No mutation 4. No migration 5. No natural selection

Hardy-Weinberg Equilibrium Let’s look at a gene for cat’s coat color. The cats can either be black or white. There are 2 possible alleles: B or b. Let’s look at a gene for cat’s coat color. The cats can either be black or white. There are 2 possible alleles: B or b. The more common allele (B) is designated p The more common allele (B) is designated p The less common allele (b) is designated q The less common allele (b) is designated q p + q = 1 (Only 2 alleles, must add up to 100%!) p + q = 1 (Only 2 alleles, must add up to 100%!)

Hardy-Weinberg Equilibrium The Hardy-Weinberg equilibrium can be written as an equation The Hardy-Weinberg equilibrium can be written as an equation 1 = p 2 + 2pq + q 2 1 = p 2 + 2pq + q 2 Individuals homozygous for allele B Individuals heterozygous for alleles B and b Individuals homozygous for allele b The equation allows calculation of allele frequencies

Hardy-Weinberg Equilibrium Back to our example, let’s say that out of 100 cats, 16 are white and 84 are black. This gives us some information… Back to our example, let’s say that out of 100 cats, 16 are white and 84 are black. This gives us some information… Frequency of white cats (bb) = 0.16 Frequency of white cats (bb) = 0.16 q 2 = 0.16 q 2 = 0.16 q = √0.16 = 0.4 q = √0.16 = 0.4 p+q=1 Therefore… p=0.6 p+q=1 Therefore… p=0.6 Frequency of homozygous dominant? p 2 Frequency of homozygous dominant? p 2 Frequency of heterozygous? 2pq Frequency of heterozygous? 2pq

Hardy-Weinberg Example If 9% of an African population is born with a severe form of sickle-cell anemia (ss), what percentage of the population will be heterozygous(Ss) for the sickle-cell gene? If 9% of an African population is born with a severe form of sickle-cell anemia (ss), what percentage of the population will be heterozygous(Ss) for the sickle-cell gene?

Why do allele frequencies change? Five evolutionary forces can significantly alter the allele frequencies of a population Five evolutionary forces can significantly alter the allele frequencies of a population 1. Mutation 1. Mutation 2. Migration 2. Migration 3. Genetic drift 3. Genetic drift 4. Nonrandom mating 4. Nonrandom mating 5. Selection 5. Selection

Mutation Errors in DNA replication Errors in DNA replication The ultimate source of new variation The ultimate source of new variation However, mutations are rare…they are only one small factor However, mutations are rare…they are only one small factor

Migration Movement of individuals from one population to another Movement of individuals from one population to another Immigration: movement into a population Immigration: movement into a population Emigration: movement out of a population Emigration: movement out of a population A very potent agent of change A very potent agent of change

Genetic Drift Random loss of alleles Random loss of alleles More likely to occur in smaller population More likely to occur in smaller population Founder effect Founder effect Small group of individuals establishes a population in a new location, those genes take over Small group of individuals establishes a population in a new location, those genes take over Bottleneck effect Bottleneck effect A sudden decrease in population size to natural forces; whoever lives passes their genes on A sudden decrease in population size to natural forces; whoever lives passes their genes on

Nonrandom Mating Mating that occurs more or less frequently than expected by chance Mating that occurs more or less frequently than expected by chance Inbreeding Inbreeding Mating with relatives Mating with relatives Increases homozygosity Increases homozygosity Outbreeding Outbreeding Mating with non-relatives Mating with non-relatives Increases heterozygosity Increases heterozygosity

Selection Some individuals leave behind more offspring than others Some individuals leave behind more offspring than others Artificial selection Artificial selection Breeder selects for desired characteristics Breeder selects for desired characteristics Natural selection Natural selection Environment selects for adapted characteristics Environment selects for adapted characteristics