Evolution Notes Unit 7

15.2 Evidence of Evolution Support for Evolution The fossil record Chapter 15 Evolution 15.2 Evidence of Evolution 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. Glyptodont Armadillo

Chapter 15 Evolution 15.2 Evidence of Evolution Support for Evolution Geographic Distribution The distribution of plants and animals that Darwin saw first suggested evolution to Darwin. Rabbit Mara

Homologous Structures Anatomically similar structures inherited from a common ancestor

Same function but different structure Chapter 15 Evolution Analogous Structures Same function but different structure NOT inherited from common ancestor.

Vestigial Structures 15.2 Evidence of Evolution Chapter 15 Evolution 15.2 Evidence of Evolution Vestigial Structures 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.

Evidence of Evolution 3. 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 4. Molecular evidence: DNA The more closely related you are, the more similar the DNA DNARNAPROTEIN!

Chapter 15 Evolution 15.2 Evidence of Evolution Comparisons of the similarities in organisms are seen in comparative anatomy and in the fossil record. Organisms with closely related morphological features have more closely related molecular features.

Allows organisms to become almost invisible to predators Chapter 15 Evolution 15.2 Evidence of Evolution Camouflage Allows organisms to become almost invisible to predators Leafy sea dragon

One species evolves to resemble another species. Chapter 15 Evolution 15.2 Evidence of Evolution Mimicry One species evolves to resemble another species. Western coral snake California kingsnake

More Terms Fitness – ability of an individual to survive and reproduce in a specific environment Adaptation – inherited characteristic that increases an organism’s chance of survival Can be physical traits as well as behavioral traits

Chapter 15 Evolution 15.3 Shaping Evolutionary Theory Natural Selection Acts to select the individuals that are best adapted for survival and reproduction

Chapter 15 Evolution 15.3 Shaping Evolutionary Theory Stabilizing selection operates to eliminate extreme phenotypes when the average 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. Chapter 15 Evolution 15.3 Shaping Evolutionary Theory 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. A useful example can be found in the breeding of the greyhound dog. Early breeders were interested in dog with the greatest speed. They carefully selected from a group of hounds those who ran the fastest. From their offspring, the greyhound breeders again selected those 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).

Example: In an environment with BOTH black and white rocks…. Chapter 15 Evolution 15.3 Shaping Evolutionary Theory Disruptive selection is a 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 If this population of rabbits were put into an area that had very dark black rocks as well as very 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.

15.3 Shaping Evolutionary Theory Chapter 15 Evolution 15.3 Shaping Evolutionary Theory Mechanisms of Evolution Population genetics Hardy-Weinberg principle states that when allelic frequencies remain constant, a population is in genetic equilibrium.

15.3 Shaping Evolutionary Theory Chapter 15 Evolution 15.3 Shaping Evolutionary Theory

Chapter 15 Evolution 15.3 Shaping Evolutionary Theory Genetic Drift A change in the allelic frequencies in a population that is due to chance and random mating In smaller populations, the effects of genetic drift become more pronounced, and the chance of losing an allele becomes greater. 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.

Chapter 15 Evolution 15.3 Shaping Evolutionary Theory Nonrandom Mating Promotes inbreeding & could lead to a change in allelic proportions favoring individuals that are homozygous for particular traits

What is a gene pool? Gene pool – combined genetic info of all members of a population Contains two of more alleles (genes) for the same trait Allele frequency – number of times an allele occurs in a gene pool compared to the number of times another allele occurs (expressed in percents)

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

Chapter 15 Evolution 15.3 Shaping Evolutionary Theory Founder Effect The loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population Island 1 Island 2 Mainland Island 3

Evolution 15.3 Shaping Evolutionary Theory Bottleneck a significant percentage of a population or species is killed or otherwise prevented from reproducing and can rebound later Often caused by a natural disaster

Chapter 15 Evolution 15.3 Shaping Evolutionary Theory Coevolution The relationship between two species might be so close that the evolution of one species affects the evolution of the other species. Mutualism

Chapter 15 Evolution 15.3 Shaping Evolutionary Theory Convergent Evolution Unrelated species evolve similar traits even though they live in different parts of the world.

Chapter 15 Evolution 15.3 Shaping Evolutionary Theory Prezygotic isolation prevents reproduction by making fertilization unlikely. In behavioral isolation, patterns of courtship may be different. In temporal isolation, different groups may not be reproductively mature at the same season, or month, or year. In ecological isolation, not in the same habitat where they are likely to meet. Eastern meadowlark and Western meadowlark

Postzygotic isolation occurs when fertilization has occurred but Chapter 15 Evolution 15.3 Shaping Evolutionary Theory Postzygotic isolation occurs when fertilization has occurred but a hybrid offspring cannot develop or reproduce. Prevents offspring survival or reproduction Liger

15.3 Shaping Evolutionary Theory Chapter 15 Evolution 15.3 Shaping Evolutionary Theory 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