February 13 B Day Test: Chapters 18, 19, 20 Coming up…………… Parade of Kingdoms due 2/23 - Don’t wait until the last minute, study each chapter – there will be multiple quizzes and a test at the end. Be ready for the Drosophila lab and the Transformation lab so we can start as soon as the live materials are in - highlight important points.

EVOLUTION & SPECIATION

Population: a localized group of individuals belonging to the same species Species: a group of populations whose individuals have the potential to interbreed and produce fertile offspring Gene pool: the total aggregate of genes in a population at any one time Population genetics: the study of genetic changes in populations Modern synthesis/neo-Darwinism “Individuals are selected, but populations evolve.”

Gene Pool Combined genetic info. of all members Allele frequency is # of times alleles occur

Variation in Populations 2 processes can lead to this: Mutations - change in DNA sequence Gene Shuffling – from sexual reproduction

Genetic Drift changes populations……. Random change in allele frequency causes an allele to become common

Microevolution The Bottleneck Effect: type of genetic drift resulting from a reduction in population (natural disaster) such that the surviving population is no longer genetically representative of the original population

Microevolution Founder Effect: a cause of genetic drift attributable to colonization by a limited number of individuals from a parent population

Microevolution Gene Flow: genetic exchange due to the migration of fertile individuals or gametes between populations (reduces differences between populations

Microevolution Nonrandom mating: inbreeding and assortive mating (both shift frequencies of different genotypes)

Microevolution Natural Selection: differential success in reproduction; only form of microevolution that adapts a population to its environment

SPECIATION - formation new species - Anagenesis (phyletic evolution): accumulation of heritable changes - Cladogenesis (branching evolution): budding of new species from a parent species that continues to exist (basis of biological diversity))

Evolution of Populations Occurs when there is a change in relative frequency of alleles

Punctuated equilibrium Tempo of speciation: gradual vs. divergence in rapid bursts; Niles Eldredge and Stephen Jay Gould (1972); helped explain the non-gradual appearance of species in the fossil record

Population variation Polymorphism: coexistence of 2 or more distinct forms of individuals (morphs) within the same population Geographical variation: differences in genetic structure between populations (cline)

Variation Preservation Prevention of natural selection’s reduction of variation Diploidy 2nd set of chromosomes hides variation in the heterozygote Balanced polymorphism 1- heterozygote advantage (hybrid vigor; i.e., malaria/sickle-cell anemia); 2- frequency dependent selection (survival & reproduction of any 1 morph declines if it becomes too common; i.e., parasite/host)

Sexual selection Sexual dimorphism: secondary sex characteristic distinction Sexual selection: selection towards secondary sex characteristics that leads to sexual dimorphism

Natural Selection Shifts to middle range 2 extremes 1 extreme

Fitness: contribution an individual makes to the gene pool of the next generation

Conditions needed for Genetic Equilibrium

Hardy-Weinberg Equation p=frequency of one allele (A); q=frequency of the other allele (a); p+q=1.0 (p=1-q & q=1-p) P2=frequency of AA genotype; 2pq=frequency of Aa plus aA genotype; q2=frequency of aa genotype; p2 + 2pq + q2 = 1.0

AS NEW SPECIES EVOLVE, POPULATIONS BECOME REPRODUCTIVELY ISOLATED (gene pools are isolated) REPRODUCTIVE ISOLATION – MEMEBERS OF 2 POPULATIONS CANNOT INTERBREED & PRODUCE FERTILE OFFSPRING.

Table 23.1a

Table 23.1b

Tigon Result of male tiger and female lion mating incaptivity. Offspring are infertile. Separated both geographically and ecologically.

Liger Result of male lion and female tiger mating in captivity. Offspring are infertile.

Fig. 23.6 Four species of leopard frogs: differ in their mating calls. Hybrids are inviable.

These squirrels living on opposite sides of the Grand Canyon demonstrate allopatric speciation.

Sympatric: reproductively isolated subpopulation in the midst of its parent population (change in genome); polyploidy in plants; cichlid fishes

Evidence of Evolution Fossil Record Geographic Distribution of Living Species Homologous Body structures Similarities in Embryology

Evidence of Evolution Fossil Record provides evidence that living things have evolved Fossils show the history of life on earth and how different groups of organisms have changed over time

Marsupial Mammals Convergent Evolution Placental mammals and Flying Squirrel Sugar Glider Marsupial Mammals Convergent Evolution and Analogous Structures Placental mammals Mammalia Rat like common ancestor

Big Question!!! How did life arise on the big blue planet?? Scientists attempt to answer this question scientifically.

Relative Dating versus Absolute Dating

Relative Dating Can determine a fossil’s relative age Performed by estimating fossil age compared with that of other fossils Drawbacks – provides no info about age in years

Absolute dating Can determine the absolute age in numbers Is performed by radioactive dating – based on the amount of remaining radioactive isotopes remain Drawbacks - part of the fossil is destroyed during the test

Carbon-14 Dating

Fossil Formation

Big Bang Theory A cosmic explosion that hurled matter and in all directions created the universe 10-20 billion years ago Evidence it explains why distant galaxies are traveling away from us at great speeds Cosmic radiation from the explosion can be observed The Big Bang theory probably will never be proven; consequentially, leaving a number of tough, unanswered questions.

What was early earth like? Earth was Hot!! Little or no oxygen Gasses in atmosphere: Hydrogen cyanide (poison to you!) Hydrogen sulfide Carbon dioxide Carbon monoxide Nitrogen water

So how did the earth get oxygen? Some of that oxygen was generated by photosynthetic cyanobacteria Some came from the chemical separation of water molecules into oxygen and hydrogen.

Others evolved ways of using oxygen for respiration Oxygen drove some life forms to extinction Others evolved ways of using oxygen for respiration

How did life begin? Miller and Urey’s Experiment Passed sparks through a mixture of hydrogen methane ammonia and water This produced amino acids – the building blocks of life

Miller’s experiment suggests that lightning could have produced amino acids

How can simple amino acids result in life? There are 3 theories 1. Formation of microspheres Large organic molecules can sometimes form tiny proteinoid microspheres Store and release energy, selectively permeable membranes, may have acquired more characteristics of living cells

2nd Hypothesis for Life Evolution of RNA to DNA RNA was assembled from simple organic molecules in a primordial soup RNA was able to replicate itself and eventually form DNA Not scientifically proven to be possible

3rd Theory of Life Endosymbiotic theory eukaryotic cells arose from living communities formed by prokaryotic organisms Ancient prokaryotes entered primitive eukaryotic cells and remained there as organelles