EVOLUTION SPECIATION VOCABULARY REVIEW EVOLUTION CHANGE OVER TIME

EVOLUTION & SPECIATION

VOCABULARY REVIEW • EVOLUTION – CHANGE OVER TIME • NATURAL SELECTION - INDIVIDUALS BETTER ADAPTED TO THE ENVIRONMENT ARE ABLE TO SURVIVE & REPRODUCE. – A. K. A. “SURVIVAL OF THE FITTEST”

NEW VOCABULARY • POPULATION – GROUP OF INDIVIDUALS OF SAME SPECIES THAT INTERBREED • GENE POOL – COMMON GROUP OF ALL GENES PRESENT IN A POPULATION

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

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

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

• Natural Selection: differential success in reproduction; • adapts a population to its environment

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

Phenotype Expression • Depends on how many genes control that trait

Single-Gene vs. Polygenic Traits Single-Gene: 2 Distinct Phenotypes (EG: tongue rolling) Polygenic: (more than one gene) Many Phenotypes (EG: Height)

Allele Frequencies Natural Selection Single Gene Traits Genetic Drift Polygenic Traits Directional Selection Stabilizing Selection Disruptive Selection

Natural Selection on Polygenic Traits • Shifts to middle range • Shifts to 2 extremes • Shifts to 1 extreme

SPECIATION • THE FORMATION OF NEW SPECIES • AS NEW SPECIES EVOLVE, POPULATIONS BECOME REPRODUCTIVELY ISOLATED • REPRODUCTIVE ISOLATION – MEMBERS OF 2 POPULATIONS CANNOT INTERBREED & PRODUCE FERTILE OFFSPRING.

3 ISOLATING MECHANISMS……. . • BEHAVIORAL ISOLATION- CAPABLE OF BREEDING BUT HAVE DIFFERENCES IN COURTSHIP RITUALS (EX. MEADOWLARKS) • GEOGRAPHICAL ISOLATION – SEPARATED BY GEOGRAPHIC BARRIERS LIKE RIVERS, MOUNTAINS, OR BODIES OF WATER (EX. SQUIRREL) • TEMPORAL ISOLATION – 2 OR MORE SPECIES REPRODUCE AT DIFFERENT TIMES.

Table 23. 1 a

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.

Table 23. 1 b

Fig. 23. 6 Four species of leopard frogs: differ in their mating calls. Reproductive isolation.

These squirrels live on opposite sides of the Grand Canyon. This is an example of speciation.

Hawaiian Honeycreepers An example of adaptive radiation – these species all diverged from a common ancestor (founder species) FOUNDER SPECIES

SPECIATION IN DARWIN’S FINCHES • SPECIAITON IN THE GALAPAGOS FINCHES OCCURRED BY: - FOUNDING OF A NEW POPULATION, - GEOGRAPHIC ISOLATION which led to -REPRODUCTIVE ISOLATION and CHANGES IN THE NEW POPULATION’S GENE POOL due to COMPETITION.

Evidence of Evolution 1. Fossil Record 2. Geographic Distribution of Living Species 3. Homologous Body structures 4. 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

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

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.

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

rd 3 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