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Evolution Evolution Evolution- change in population over time Evolution- Darwin Darwin father of modern evolutionary theory Galapagos Islands HMS Beagle Scientists who influenced Darwin Lamarck- organisms change due to the pressures of their environment, traits are acquired He proposed that by using or not using its body parts, an individual tends to develop certain characteristics, which it passes on to its offspring. Scientists who influenced Darwin- Lamarck Example: A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring. Scientists who influenced Darwin Lyell Principles of Geology plant and animal species emerged, developed variations and then became extinct Scientists who influenced Darwin Malthus- populations outgrew their food supplies causing competition Essay on the Principle of Population (1798) Natural Selection Natural Selectionorganisms with traits best suited to the environment have a higher survival rate, “descent with modification” Natural Selection 1. organisms produce more offspring than can survive 2. variation (differences) exist in all populations 3. organisms best suited to environments will have more offspring 4. over time organisms with certain advantageous variations make up most of the population Natural Selection Example: Peppered Moths during the Industrial Revolution Natural Selection Fitness- reproductive efficiency of various individuals or genotypes in a population depends on probability that one individual will contribute its genetic information to the next generation Natural Selection Extinction- permanent loss of a species 5 mass extinctions throughout history Permian period96% of marine invertebrates Cretaceous period60-75% of marine species Evidence for Evolution 1. 2. 3. 4. 5. 6. Fossils Comparative anatomy Comparative embryology Biochemistry Genetic evidence Direct evidence Evidence for Evolution 1. Fossils mold or cast of organism left in rock, fossilized bone and teeth life becomes more complex over time record is incomplete Evidence for Evolution Most complete fossil record is for the horse Evidence for Evolution Relative dating layers in rock bed used to date organisms Evidence for Evolution Radioisotope dating- uses half-life of isotope to approximate age of organism Carbon is used frequently Evidence for Evolution Half-life Evidence for Evolution phylogenydescription of the lines of descent of plants and animals as they lived from one to the next Evidence for Evolution 2. Comparative Anatomy- the study of the structures of different organisms homologous parts modified structures among different groups of descendants Evidence for Evolution Comparative Anatomy Evidence for Evolution Comparative Anatomy analogous partsstructures in organisms that have no common origin but serve the same function Example: bird’s wing, bat’s wing and insect’s wing Evidence for Evolution Comparative Anatomy vestigial organs- organs having no functions in the living organism Vestigial toes in the horse Vestigial pelvis and femur in whales Evidence for Evolution 3. Comparative Embryology the study of developing plants and animals Below is the pictures of embryos for a fish, human, rabbit, tortoise, and chicken. Can you guess which one is each type of organism? 1 2 3 4 5 Evidence for Evolution Comparative Embryology Here the pictures of the second set of development is added. Can you tell now? 1 2 3 4 5 Evidence for Evolution How about now? 1 2 3 4 5 Evidence for Evolution Comparative Embryology- The complete picture Evidence for Evolution 4. Biochemistry comparison of DNA and proteins in the body Example: comparison of hemoglobin (blood protein) in human, chimp, and dog. Human and chimp hemoglobin more alike than dog Evidence for Evolution 5. Genetic Evidence Mutations- mistakes in the genetic code Causes changes in populations over time Population genetics- researchers use mathematical descriptions of genetic make ups to help them trace evolutionary trends within populations Selective Breeding- humans choose plants/animals with most desirable traits and breed them to pass those traits to offspring Evidence for Evolution Biodiversity Ecosystem diversity- variety of habitats, living communities and ecological processes in the living world Species diversity- different organisms on Earth Genetic diversity- different forms of genetic information carried by all living things on Earth Example Myosin- protein in muscle cells causing contractions. Also found in yeast cells- used to move cell parts Evidence for Evolution 6. Direct Evidence Rapid Evolution Strains of bacteria becoming resistant to antibiotics Weeds and herbicides Insects and pesticide Adaptations Adaptation- change in a species that makes it better suited to its hump to store nutrition during environment Along trips or when food or water Fur inside the ears to protect inner ear from sand Nostrils that close to keep sand out Calluses on the the knees to protect from abrasion is scarce Long eyelashes to protect their eyes from the sand when the wind is blowing Large feet for standing in the sand Types of Adaptations Structural Changes in structure or anatomy Example: bird’s beak or claws Mimicry- a harmless species resembles a harmful one, predators learn to avoid both species Camouflage- species features blend in with the environment Mimicry Camouflage Types of Adaptations Physiological Changes in chemical makeup Examples: digestion enzymes, snake venom, octopus ink Types of Adaptations Behavioral Responses to the environment Example: bird migration Mechanisms for Evolution Species- group of organisms that can interbreed AND produce viable offspring Populations evolve NOT individuals Origin of a Species Common Misperception: Individuals Evolve Species evolve NOT individuals “And now there go the Wilsons!... Seems Like everyone’s evolving except us!” Mechanisms for Evolution Gene pool- all the alleles for a trait in the population Over time gene pools shift to traits that are best suited to the environment Allelic frequency- the percent of any specific gene in a population Genetic Equilibrium- when the percentage of alleles in a population remains stable over time How does evolution occur? 1. mutation- change in genetic code caused by environmental factors like radiation/chemicals or by chance 2. genetic drift- allelic frequency changes by chance, usually in small populations 3. movement of individuals in and out of populations Genetic Drift Natural Selection acts on variation in a population 1. stabilizing – favors average individual 2. directional – favors one extreme variation 3. disruptive – favors both extremes of variation 4. diversifying- two or more phenotypes develop, different selective pressures operate at the same time 5. heterozygote advantage- heterozygote (Aa) has higher fitness than either homozygote (AA or aa) Example- sickle cell anemia Natural Selection acts on variation in a population Diversifying Selection Heterozygote Advantage In sickle cell anemia, heterozygous individual has normal and sickle cells May be an advantage to surviving malaria Normal (AA)- gets malaria and dies Heterozygous (Aa)- survives malaria Sickle cell homozygous (aa)die from sickle cell Origin of a Species Speciation – formation of a new species, members of similar populations no longer interbreed Origin of a Species 1. Geographic Isolation Physical barrier divides population River, canyon, mtn. splits group Two species of squirrel split by the Grand Canyon Origin of a Species 2. Reproductive Isolation Members in a population can no longer interbreed Caused by seasonal, mechanical, and behavioral differences Origin of a Species 3. Polyploidy Mistakes during mitosis or meiosis results in individuals with multiple chromosomes Is speciation fast or slow? Two hypotheses Punctuated Equilibrium – in rapid bursts Gradualism - slowly ov time Patterns in Evolution Adaptive radiation – one ancestral species evolves into a number of species to exploit a number of habitats. Patterns in Evolution Divergent evolution- one species evolves into two species with different characteristics (get more and more different from each other) Patterns in Evolution Convergent evolution – distant or unrelated species evolve similar characteristics to take advantage of similar environments Example: fish and dolphin