Evolution and Classification BY SUSANA LONDONO LYNNSEY NGUYEN

Evolution and Classification BY: SUSANA LONDONO, LYNNSEY NGUYEN, CAMILLE PAGUINTO AND ALYSSA SILVA

PART 1 A: Darwin’s Principles of Natural Selection 1. Variation 2. Overproduction 3. Competition 4. Differential Survival 5. Differential Reproduction

Variation • Heritable variation within traits - Sexual recombination - Mutation

Overproduction & Competition • Individual organisms produce more offspring than can survive • Therefore, organisms compete for survival

Differential Survival & Reproduction • Survival of the fittest • Survivors reproduce and pass on traits to offspring - Certain allele frequency increases - Population evolves

PART 1 B: Chi – Square Test 1. Decide on a null hypothesis (there is/isn’t a significant difference between specified populations, any observed difference being due to sampling or experimental error) 2. Note your “expected” and “observed” values 3. Calculate the chi-square • 4. Look up the chi-square critical value based on the p-value and degrees of freedom (df) • 5. Add the values for all categories -> sum of (o-e) /e df = number of categories - 1 Determine whether the chi-square value < critical value — if so, the null hypothesis is accepted; if not, the null hypothesis is rejected

PART 2: Selection • Types: Directional, Diversifying and Stabilizing. • sexual selection • -based on variation in sexual characteristics related to competition and attraction of mates • artificial selection • -seek individuals with desired traits to produce more offspring

Causes of Evolution of a Population • Genetic drift: change in a gene pool due to chance • bottleneck effect • founder effect • Gene flow • movement of alleles into and out of a population • increases diversity • Mutations: change in genetic material; considered to be key idea for evolutionary change • Nonrandom mating: specific choosing of mate; eliminate the ones who are less-fit • Natural selection: better adapted=better reproductive success

PART 3: Evidence for Evolution • Fossil Record • Comparative Embryology • -radiometric dating; half-life • -embryonic development • Comparative Anatomy • Molecular Biology • -homologous vs analogous vs • -cytochrome C; universal vestigial genetic code • Comparative Biochemistry • Biogeography • -common ancestors, antibiotic resistance • -Pangea; plate tectonics; continental drift

PART 4: Hardy-Weinberg Equilibrium The Hardy-Weinberg principle: • Describes a population that is not evolving • States that frequencies of alleles and genotypes in a population remain constant from generation to generation

Hardy – Weinberg Conditions 1. Large population 2. Random mating 3. No migration 4. No mutation 5. No selection

1. Large Population • The bigger the better • Necessary to reduce chance occurrences having a significant effect on allelic and genotypic frequencies of a population.

What happens if the “large population rule” is broken? • Genetic drift • Due to chance changes in populations causing genotypic frequencies to change over time • Likely to “lose” less common alleles or at least represent dissimilar gene frequencies relative to the original population • Founder effect: increases genetic drift as a few individuals move to a new, isolated area • Bottleneck effect: increases genetic drift due to drastic population reduction (ie. - natural disaster, loss of habitat)

2. Random Mating • Insures a consistent, random shuffling of genes.

3. No Migration • Individuals who migrate into (immigration) or out of (emigration) existing populations cause the gene frequencies of that population to change. • What happens if the “no migration rule” is broken? • Gene flow: alleles are transferred b/w existing populations b/c of the movement of individuals or gametes

4. No Mutations ins the genotype cause the most direct change in gene frequency.

5. No Selection • Natural / artificial selection ill cause a shift in gene frequencies.

p+q=1 • Percentages are represented as decimal numbers • p = the dominant allele • q = the recessive allele • Accounting for allele frequencies in isolation (p & q)

To get the 2 nd equation: (p + q = 1)^2 Square it (p + q) ^2 = 1^2 Use the “foil method” p^2 + 2 pq + q^2 = 1

p^2 + 2 pq + q^2 = 1 • p^2 = homozygous dominant • 2 pq = heterozygous • q ^2 = homozygous recessive • Accounting for phenotype frequencies • Represents the 3 genotypes of a genetic cross

Part 5 : Speciation Biological Species Concept • “Species are groups of interbreeding natural populations that are reproductively isolated from other such groups. ” – Ernst Mayr

2 Basic Types of Speciation • Allopatric- geographical isolation • Sympatric- populations adjust to accommodate different niches - Adaptive radiation: Galapagos finches

Rate of Speciation • Gradualism: Darwin(non)adaptive changes accumulate • Punctuated equilibrium: Stephen Gould, Niles Eldridge- sporadic changes

PART 6: The Origin of Life There are 4 scenarios that explain the creation of organic molecules 1. Made from inorganic compounds in the atmosphere 2. Came from outer space as rain 3. Made from hydrothermal vents in the ocean floor 4. Made from comets or asteroids that have struck the earth in the very beginning.

Miller – Urey Experiment • Miller, a biochemist, used an apparatus to prove is hypothesis: • The atmosphere of the early earth resembled a mixture of inorganic molecules: • • • Water (H 2 O) Methane (CH 4) Ammonia ( NH 3) Hydrogen (H 2) No oxygen • The mixture was kept circulating, boiling, condensing the water. • The gases passed through a chamber containing electrodes. • By the end of the experiment, paper chromatography was used to show that the flask contained amino acids and other organic molecules.

Protobionts and Protocells Are the origin of cells. • Protobionts - collection of organic molecules produced abiotically. This are surrounded by a membrane-like structure. • Exhibit properties related to life such as metabolism, reproduction, maintenance of chemical environment in the interior, which is different from its surroundings. • Believed to be a key step to the origin of life • Experiment by Sydney Fox and Aleksandr Oparin demonstrated its spontaneous formation and the similarity to conditions in earth. The experiments formed liposomes. • Examples of Protobionts are: nanobes or nanobacteria

Protobionts and Protocells continue • Coacervates were taking new materials from the ocean a degraded material, which contained the basic properties of life. Nucleic acids taking over the coacervates and replication led to the establishment of genetic material and the first living systems.

Protobionts and Protocells • Protocells are large structures enclosed by a membrane. These structures carry out the basic properties of life. • It is suggested that self replicating molecules and metabolism sources appeared together in protocells. • Vesicles, which separate inside from outside. • Abiotically produced vesicles can reproduce on their own and grow, absorb montmotillonite particles, like those on which RNA are attached. They also contain a semipermeable bilayer and carryout metabolic processes.

Free Response : -In terms of climate and geology, Charles Darwin noted that Galapagos Islands are nearly identical to the Canary Islands. Darwin was struck, however, by the fact that the Canary Islands, just off the coast of Africa (200 km or 120 miles), contain very few unique species. Whereas the Galapagos Islands, over 800 km (~500 miles) off the coast of South America, are home to scores of unique species, found nowhere else in the world. Give a concise evolutionary explanation for why remote islands would give rise to unique species, while those relatively close to mainland contain few if any species not found on the mainland.

Answer remote islands are isolated - strong selection pressure to adapt to the environment or not survive. - adaptive radiation colonizing new habitats/niches; first colonizers fill unoccupied niches - founder effect & genetic drift; no gene flow - geographic isolation in allopatric species - nearby islands share migration with mainland -gene flow - migration may mean island population & mainland share gene pool - may have similar selective pressures as mainland - similar niches on mainland & island will be populated by same species so they will experience similar selective pressures therefore few opportunities for the evolution of new or distinct species