To understand evolution you have to first have an understanding of the age of the Earth. The Earth is estimated to be approx. 4.6 billion years old. The first fossil record is believed to be about billion years old This is a very long time, and Earth has changed tremendously since its origin.

 What were some events that led to the development of Darwin’s theory of evolution? ◦ Lamark- inheritance of acquired traits through use and disuse, 1 st theory of evolution ◦ Malthus- write an essay “Principles of Population” the idea that people compete for a limited number of resources, and population growth rates depend on this flux in resources ◦ Lyell- wrote “Principles of Geology” established that the Earth has undergone tremendous changes, making it much older than once believed ◦ Wallace- through his own research came to the same conclusion as Darwin about Natural selection  Who was Charles Darwin? ◦ Lived from ◦ Developed the theory of evolution by means of natural selection

 Look for references to ◦ 1. Charles Darwin’s grandfather Erasmus Darwin, and Darwin’s brother as an influence ◦ 2. Darwin’s religious beliefs and changes in his belief system ◦ 3. Geological time, Lyell’s work on changes in geological features ◦ 4. Common ancestor ◦ 5. Malthus’ writings about population

Define Evolution: Cumulative change in groups of organisms through time or- descent with modification - differential reproductive success Principles behind evolution: 1. Individuals in a population show variation among others in the same species 2. Variations are inherited 3. Animals have more young than can survive on the available resources 4. Variations that increase reproductive success will be more common in the next generation

The theory of evolution is supported with the following evidence (see handouts for more explanation) 1. Fossil record- using relative dating and carbon-14 dating to determine age of extinct and extant groups of organisms. 2. Biogeography- comparing differences in groups of organisms in line with the migration of continents and other changes in geography 3. Comparative Anatomy- looking at common anatomical structures (homologous or vestigial features) 4. Comparative Embryology- looking at common tissue development 5. Molecular Biology- comparing the DNA and protein sequencing of extant organisms and determining the accumulation of mutations since they shared a common ancestor (phylogeny- an evolutionary tree)

Darwin’s theory was based on Natural Selection  Natural Selection: differential reproductive success; the result of selective pressures from the environment, that favor one phenotype over another  Artificial Selection: a man made selection of a phenotype, like selective breeding of agricultural plants and animals, horses, or dogs. This is also the case with antibiotics or antiviral medicines that change the body’s internal environment.

 Natural selectionthree modes  Natural selection has three modes of action: 1.Stabilizing selection 2.Directional selection 3.Diversifying selection Number of Individuals Size of individuals Small Large

 Actsextremesfavors intermediate  Acts upon extremes and favors the intermediate. Number of Individuals Size of individuals Small Large

 Favorsone extreme  Favors variants of one extreme. Number of Individuals Size of individuals Small Large

 Favorsopposite extremes  Favors variants of opposite extremes. Number of Individuals Size of individuals Small Large

evolution  The evolution of new species due to a barrier, either geographical or reproductive.  What is a species: organisms that can and will mate to form a fertile offspring.

Geographical Barrier: Any geographical formation that physically separates a population. Ex river, mountain range, valley mechanism impedesfertile and/or viable hybrid offspring Reproductive Barrier: Any mechanism that impedes two species from producing fertile and/or viable hybrid offspring.  Two type of reproductive barriers: 1.Pre-zygotic barriers- before fertilization 2.Post-zygotic barriers- after fertilization

a. Temporal isolation: Breeding occurs at different times for different species. *Often controlled by hormones that are sensitive to temperature and light availability. b. Habitat isolation: Species breed in different habitats. *Habitats are dictated by the adaptations organisms have for shelter, food, and protection. c. Behavioral isolation: Little or no sexual attraction between species. *Behaviors can be different without the organisms physical features being different

d. Mechanical isolation: Structural differences prevent gamete exchange. This can be true also with the pollinator that a plant employs. e. Gametic isolation: Gametes die before uniting with gametes of other species, or gametes fail to unite.

a. Hybrid inviability: the Hybrid zygote fails to develop or fails to reach sexual maturity. b. Hybrid sterility: the Hybrid fails to produce functional gametes. Ex. Mule a hybrid of horse and donkey, all mules are male and sterile c. Hybrid breakdown: Offspring of hybrids are weak or infertile.

ancestral separatedgeographical barrier.  Induced when the ancestral population becomes separated by a geographical barrier.  If separated for a long period of time they will become reproductively isolated  Example: Grand Canyon and ground squirrels

reproductively isolated sub-population  Result of a radical change in the genome that produces a reproductively isolated sub-population within the parent population (rare).  Example: Plant evolution - polyploid chromosome # A species doubles it’s chromosome # to become tetraploid. reproductive sub-population Parent population

 Two theories: 1.Gradualist Model (Neo- Darwinian): Slow gradual changes accumulate in species overtime. 2.Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change followed by a long period of no change. GradualismPunctuated Equilibrium

 Organisms separated either reproductively or geographically are under different selective pressures and evolve in different directions  This is often called Adaptive radiation ◦ Ex. Darwin’s Galapagos finches who descended from a small group of mainland finches of South America

 Emergence of numerous species common ancestor  Emergence of numerous species from a common ancestor introduced to new and diverse environments, where land formations, food and predators may be different.  Example: Darwin’s Finches of the Galapagos

 Speciesevolutionary branches very similar environments.  Species from different evolutionary branches may come to resemble one another if they live in very similar environments. analogous  These are analogous characteristics  Example: Shark, Dolphin Under similar environmental pressures these two very different organisms have developed similar body styles and predatory habits

 Evolutionary change selective forcesecond first  Evolutionary change, in which one species act as a selective force on a second species, inducing adaptations that in turn act as selective force on the first species.  Example: symbiotic relationships are everywhere. Think “Circle of Life” 1.Acacia ants and acacia trees 2.Humming birds and plants with flowers with long tubes

 Microevolution is change in the allele frequencies of a population over generations. This is on a small scale.  Allele frequencies refer to the actual number of a particular allele within a population’s gene pool ( all the alleles at all loci in all the members of a population)

1. Genetic Drift- loss of variation (allele frequencies) due to a sudden environmental act that reduces the population 2. Gene Flow – change in variation (allele frequencies) due to immigration or emigration, movement of individuals into or out of the population 3. Mutation- introduction of a new allele that becomes established in the gene pool 4. Natural Selection- differential reproductive success, due to environmental pressure on a favorable phenotype 5. Non-Random mating -mate choice is no longer based on equal chance or opportunity. Mate choice has become selective and based on some characteristic

Evolution occurs at the population level, population is defined as a group of the same species that live in the same area and interbreed, producing fertile offspring.  Hardy Weinberg equilibrium theory states that a population’s allele frequencies will remain unchanged generation after generation, no evolution, if the following 5 conditions are held constant:  Mutations do not change gene pool  Mating is random and each organism has equal opportunity  No natural selection, no phenotype is more favorable  Population is large and contains variation  No gene flow (emigration, immigration in/out of population)

p 2 + 2pq + q 2 = 1 p = dominant allele q = recessive allele p 2 = Homozygous dominant genotype (AA) 2pq= Heterozygous genotype (Aa) q 2 = Homozygous recessive genotype (aa) Each letter represents the frequency of a particular allele in the population p+q=1

We can look at a population and identify specific traits or phenotypes. We can actually count the number of individuals with those specific traits. Ex. If there are 100 pigs 25 of them are black and 75 of them are pink, or 25% is black and 75% is pink. What if you knew the black allele was Dominant and the pink allele was Recessive. Could you determine which ones had which genotype?

 If B= Black skin and b= pink skin in a pig  If 25% of the population were black and 75% were pink, how many of them are ◦ Homzygous recessive bb ◦ Homzygous dominant BB ◦ Heterzygous Bb Remember that p is the dominant allele and q is the recessive allele. What does bb, BB, and Bb look like? BB- black Bb- black bb- pink p 2 - black 2pq- black q 2 = pink Can we calculate q? yes if we know q then we can find p

q= 0.6 a. a.0.6, b. 0.4, b. c. AA=.16 and Aa= A randomly mating population has an established frequency of 36% for organisms homozygous recessive for a given trait. What is the frequency of the recessive allele in the gene pool ? 2. You have sampled a population in which you know that the percentage of homozygous recessive genotypes (aa) is 36%. Calculate the following a. The frequency of the a allele b. The frequency of the A allele c. Frequency of AA and Aa