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EVOLUTION SPECIES LINNEAUS’ CLASSIFICATION SYSTEM The process of biological change by which descendants come to differ from their ancestors A group of organisms that can reproduce and have fertile offspring Organisms are grouped according to: physical similarities, species can change 3 IDEAS OF GEOLOGICAL CHANGES FOSSILS CATASTROPHISM 1. Catastrophism 2. Gradualism 3. Uniformitarianism Traces of organisms that existed in the past Past natural disasters shaped landforms, and caused species to become extinct in the process GRADUALISM UNIFORMITARIANISM Landforms were shaped by very slow changes over a long period of time, and not by natural disasters (accepted theory) The same processes that shaped landforms in the past also shape landforms today WHAT DID DARWIN OBSERVE? Variation of the traits among similar species VARIATION ADAPTATION WHAT CONVINCED DARWIN THAT EVOLUTION OCCURS? The differences in the physical traits among individuals in a group of organisms among islands Feature that allows an organism to better survive in its environment The variation of similar species among islands Fossil evidence Geologic events DARWIN’S 4 REASONINGS THAT LED HIM TO HIS IDEA FOR NATURAL SELECTION: 1. 2. 3. 4. Artificial selection Heritability Natural selection Struggle for survival (Thomas Malthus- food, water, and shelter are limits to human population growth) ARTIFICIAL SELECTION Humans select and breed individuals with the traits they desire to produce more individuals with those traits HERITABILITY The ability of a trait to be passes down from one generation to the next (Not acquired) NATURAL SELECTION POPULATION FOUR MAIN PRINCIPALS TO THE THEORY OF NATURAL SELECTION (Darwin and Wallace) Process in which individuals that have inherited beneficial adaptations produce more offspring than do other individuals All the individuals of a species that live in an area Variation (genetic) Overproduction (competition) Adaptation Descent with modification FITNESS NATURAL SELECTION ACTS ON EXISTING VARIATION SOURCES OF EVIDENCE FOR EVOLUTION A measure of the ability to survive and reproduce Acts on phenotypes (physical traits), and not on genetic material Changing environments Adaptations as compromises (panda bear’s “thumb”) Fossils Geography Embryologythe study of embryos and their development Anatomy HOMOLOGOUS STRUCTURES ANALOGOUS STRUCTURES VESTIGIAL STRUCTURES Features that are similar in structure, but appear in different organisms and may have different functions (front limbs of humans, bats, and moles) Structures that perform a similar function, but are not similar in origin (wings of birds and butterflies) Small leftover organs or structures that had a function in an early ancestor (pelvic bones in whales or snakes) PALEONTOLOGY The study of fossils or extinct organisms WHERE THE GENETIC VARIATION IS STORED? In a population’s GENE POOL Gene Pool Collection of alleles found in all of the individuals of a population Allele An alternative form of a gene; occurs at a specific place on a chromosome A measure of how common an allele is in a population An allele frequency Two main sources of Genetic variation: Allele frequency = one allele / to the total # of the alleles Mutation Recombination Mutation Recombination Hybridization A random change in DNA a new allele increase the genetic variation in a gene pool New combinations of alleles form during meiosis – the type of cell division that forms gametes (sex cell; an egg or a sperm cell). Many different genetic combinations When organisms breed with organisms of another closely-related species Normal distribution The frequency is highest for the middle, or mean phenotype, and lowest at the two ends, or extreme phenotypes The alleles related to the favorable phenotypes increase in frequency Microevolution Three ways that natural selection can change the distribution of a trait The observable change in the allele frequencies of a population over time Directional Selection Stabilizing Selection Disruptive Selection Directional Selection Stabilizing Selection Disruptive Selection Selection that favors a phenotype at one end, or extreme, of a range (Evolution of antibiotic-resistant bacteria) Selection that favors the middle, or intermediate, phenotype (Middle-sized gall-fly) Selection that favors both extreme phenotypes (Dull brown birds and bright blue birds) Gene flow Genetic drift Two processes that cause genetic drift to occur The movement of alleles from one population to another A change in allele frequencies due to change Loss of genetic variation The bottleneck effect The founder effect The bottleneck effect The founder effect When Sexual selection occurs? Genetic drift that occurs after a population has been greatly reduces in size (Natural disaster) Genetic drift that occurs after a small number of individuals begin to live in a new area Occurs when certain traits increase mating success, and gets passed on to the next generation Five conditions of HardyWeinberg equilibrium Hardy-Weinberg equilibrium describes populations that are not evolving The Hardy-Weinberg equation is used to predict what? What is the formula of genotype frequency in a population? Very large population. No genetic drift can occur. No emigration or immigration. No gene flow can occur. No mutations. No new alleles can be added to the gene pool. Random mating. No sexual selection can occur. No natural selection. All traits must equally help in survival. The Hardy-Weinberg equation is used to predict genotype frequencies in a population p² + 2pq + q² = 1 p – Frequency of the dominant allele q – Frequency of the recessive allele What are the five factors that can lead to evolution? The isolation of populations can lead to what? Speciation Initial population Gene Flow Sexual Selection Genetic Drift Mutation Natural Selection Speciation The process of one species becoming two or more separate species (Last step is reproductive isolation) Reproductive isolation When members of different populations can no longer mate successfully Behavioral barriers Name the three types of barriers to mating Result in behavioral isolation, isolation caused by differences in courtship and mating behaviors. Geographic, or physical Result in geographic isolation, such as when a river or mountain divides a population into two or more groups Temporal barriers Result in temporal isolation, when timing prevents reproduction between populations Convergent evolution (to come together) is when unrelated species Name the two ways that natural selection can direct a population’s traits evolve similar characteristics (Wing on birds and insects) Divergent evolution (to move apart) is when closely related species evolve in different directions, and become increasingly different (kit fox and red fox) The process in which two or more species evolve in response to changes in each other Co evolution Extinction Beneficial relationships (The bull-thorn acacia and stinging ants) Competitive relationships (shells evolved to become thicker and spinier crabs evolved more powerful claws) The permanent loss of species from Earth (Natural process) Name the two categories of extinction? Background extinctions – occur continuously, but at a low rate, one or few species are affected Mass extinctions – destroy many species, often all across Earth, occur suddenly in geologic time, because of dramatic event like as ice age or a asteroid impact Punctuated equilibrium Theory that states that speciation occurs suddenly and rapidly followed by long periods of little evolutionary change Adaptive radiation The rapid evolution of many diverse species from ancestral species. Many different species spread out in different environments