Evolution Notes Unit 7

Provide a record of species that lived long ago. Support for Evolution The fossil record Provide a record of species that lived long ago. Show that ancient species share similarities with species that now live. Darwin traveled on HMS Beagle from England-5 yr journey to coast of S America & Pacific Islands. Glyptodont Armadillo

Geographic Distribution Evolution Support for Evolution Geographic Distribution The distribution of plants & animals that Darwin saw first suggested evolution. He found evidence of species changing over time. Fossils of huge animals-giant armadillo. Similar to living species. Noticed island plants & animals looked like but not identical to plants and animals on south American continent. So indv from S. American continent had migrated to islands. Rabbit Mara

Homologous Structures Anatomically similar structures inherited from a common ancestor He compared body parts of diff species. Evidence of homo structures. Appearance across diff species offers strong evidence for common descent Forelimbs of vertebrates-similar bones Homo structures are diff in detail but similar in structure

Same function but different structure Evolution Analogous Structures Same function but different structure NOT inherited from common ancestor. Structures that perform similar function but not similar in orgin.

Vestigial Structures Evolutionary theory Structures that are the reduced forms of functional structures in other organisms. Evolutionary theory predicts that features of ancestors that no longer have a function for that species will become smaller over time until they are lost. No longer serve a purpose. Wings in ostrich-used for balance-not for flight. Large bodies and long fast legs is enough to avoid predators. Genes for coding for larger wings was not preserved. Took many generations for vest structures to shrink

Evidence of Evolution Embryology Closely related species will have more similarities/ less differences in their stages of embryological development.   Distantly related species will show less similarities/ more differences in their Evidence of Evolution

Evidence of Evolution Molecular evidence: DNA The more closely related you are, the more similar the DNA DNARNAPROTEIN!

Evolution Shaping Evolutionary Theory Natural Selection Acts to select the individuals that are best adapted for survival and reproduction

Evolution Stabilizing selection operates to eliminate extreme phenotypes when avg phenotype leads to higher fitness. Ex. Siberian Husky-medium height and build helps them do their job in the snow! Stabilizing selection favors the norm, the common, average traits in a population. Look at the Siberian Husky, a dog bred for working in the snow. The Siberian Husky is a medium dog, males weighing 16-27kg (35-60lbs). These dogs have strong pectoral and leg muscles, allowing it to move through dense snow. The Siberian Husky is well designed for working in the snow. If the Siberian Husky had heavier muscles, it would sink deeper into the snow, so they would move slower or would sink and get stuck in the snow. Yet if the Siberian Husky had lighter muscles, it would not be strong enough to pull sleds and equipment, so the dog would have little value as a working dog. So stabilizing selection has chosen a norm for the the size of the Siberian Husky.

Directional selection makes an organism more fit. Evolution Directional selection makes an organism more fit. Favors the ONE extreme phenotype Ex. Greyhound Dog-bred for extreme speed! Directional selection favors those individuals who have extreme variations in traits within a population. EX: breeding of greyhound dog. Early breeders interested in dog with the greatest speed. Carefully selected from a group of hounds who ran the fastest. From their offspring, the greyhound breeders again selected dogs who ran the fastest. By continuing this selection for those dogs who ran faster than most of the hound dog population, they gradually produced a dog who could run up to 64km/h (40mph). One single phenotype is favored causing the genetic variance to shift

Example: In an environment with BOTH black and white rocks…. Evolution Disruptive selection - process that splits a population into two groups. Example: In an environment with BOTH black and white rocks…. White and Black rabbit lives, but grey rabbit dies Natural Selection can select for two or more phenotypes-both have advantages Population of rabbits were put into an area that had very dark black rocks and white colored stone, the rabbits with black fur would be able to hide from predators amongst the black rocks and the white furred rabbits would be able to hide in the white rocks, but the gray furred rabbits would stand out in both of the habitats and thus would not survive.

Evolution Mechanisms of Evolution Population genetics Hardy-Weinberg principle states that when allelic frequencies remain constant, a population is in genetic equilibrium.

Evolution

Genetic Drift A change in the allelic frequencies in a population due to chance & random mating https://www.youtube.com/watch?v=W0TM4LQmoZY As an analogy, imagine a population of organisms represented as 20 marbles in a jar, half of them red and half blue. These two colors correspond to two different gene alleles in the population. The organisms that are reproduced in a generation are represented in another jar. Each new generation the organisms will reproduce at random. To represent this reproduction, randomly pick a marble from the original jar and deposit a new marble with the same color as its "parent" in the second jar. Repeat the process until there are 20 new marbles in the second jar. The second jar will then contain a second generation of "offspring", 20 marbles of various colors. Unless the second jar contains exactly 10 red and 10 blue marbles there will have been a purely random shift in the allele frequencies. Repeat this process a number of times, randomly reproducing each generation of marbles to form the next. The numbers of red and blue marbles picked each generation will fluctuate: sometimes more red, sometimes more blue. That is genetic drift – random variations in which organisms manage to reproduce, leading to changes over time in the allele frequencies of a population. In smaller populations -effects of genetic drift are more pronounced - chance of losing an allele increases

Often caused by a natural disaster Evolution Bottleneck a significant % of a population or species is killed or otherwise prevented from reproducing and can rebound later Often caused by a natural disaster

Founder Effect Loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population Mainland Island 3 Island 2 Island 1 https://www.youtube.com/watch?v=W0TM4LQmoZY

Nonrandom Mating Promotes inbreeding & could lead to a change in allelic proportions favoring indv that are homozygous for particular traits

What is a gene pool? Gene pool – combined genetic info of all members of a population Contains two or more alleles (genes) for the same trait

Allele frequency - a measure of how common a certain allele is in the population G = Green g = brown

Gene Flow Genes entering or leaving a population AKA. Migration Emigration Genes LEAVING a population Immigration INCOMING genes in a population

Evolution Coevolution Relationship between two species might be so close that the evolution of one species affects the evolution of the other species. Mutualism

Evolution Convergent Evolution Unrelated species evolve similar traits even though they live in different parts of the world.

Behavioral isolation- patterns of courtship may be different. Prezygotic isolation prevents reproduction by making fertilization unlikely. Western & Eastern meadowlarks use different songs for attracting a mate…won’t mate with each other Eastern meadowlark and Western meadowlark Behavioral isolation- patterns of courtship may be different.

Prezygotic isolation Temporal isolation- different groups may not be reproductively mature at the same season, month, or year.

Prezygotic isolation Ecological isolation- not in the same habitat where they are likely to meet.

Prevents offspring survival or reproduction Postzygotic isolation occurs when fertilization has occurred but a hybrid offspring cannot develop or reproduce. Prevents offspring survival or reproduction Liger

Evolution Adaptive Radiation Can occur in a relatively short time when one species gives rise to many different species in response to the creation of new habitat or some other ecological opportunity