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Transcript
Evolution Also, many plants, and some animals, form hybrids in nature. Hooded crows and carrion crows look different, and largely mate within their own groups—but in some areas, they hybridize. Should they be considered the same species or separate species? • If two lineages of oak look quite different, but occasionally form hybrids with each other, should we count them as different species? There are lots of other places where the boundary of a species is blurred. It’s not so surprising that these blurry places exist—after all, the idea of a species is something that we humans invented for our own convenience! gene pool - collection of genes for all traits in a population contains all the alleles • allele frequency- • Genetic equilibrium - How do the three terms relate??????? Hardy- Weinberg Principle A. conditions for genetic equilibrium page 302 list the five • The Hardy-Weinberg equation is a simple but powerful tool for predicting the allele frequencies within a population. Its prediction of genetic equilibrium or no frequency change under a specific set of conditions also serves as strong evidence for microevolution. As long as a population does not meet all the prerequisite conditions for genetic equilibrium, allele frequencies must change over time, and this is the primary process of evolution. Mutations Sickle cell anemia is the result of a point mutation, a change in just one nucleotide in the gene for hemoglobin. This mutation causes the hemoglobin in red blood cells to distort to a sickle shape when deoxygenated. The sickle-shaped blood cells clog in the capillaries, cutting off circulation. Cancer usually results from a series of mutations within a single cell. Often, a faulty, damaged, or missing p53 gene is to blame. The p53 gene makes a protein that stops mutated cells from dividing. Without this protein, cells divide unchecked and become tumors Genetics of Huntington’s disease Caused by a “stutter” or repeat of three bases, CAG, that are normally in a repeat of 11-29 copies; the mutation is an increase to 37-100 copies “Good Mutations” • Scientists believe that the reason for their survival was a genetic mutation found in descendents of the survivors. The gene is called CCR5-delta 32, or Delta 32 for short. Delta 32 is a gene that codes for a protein on the surface of white blood cells which acts as a receptor for other molecules involved in inflammation. Essentially, since the CCR5 Delta 32's receptor's are "turned off", it makes a person resistant or immune to certain viruses because they cannot latch onto the receptors. People who have two copies of the Delta 32 mutation were virtually immune to The Black Death, one from each parent. Those who only had one copy of the mutated gene were resistant to it. The Delta 32 mutation is more common in people of Northern European descent. Smallpox - not The Black Plague - is thought to be the reason for this gene mutation. Smallpox epidemics were common in Europe and so some people developed this mutation. • Since the CCR5 Delta 32's receptor's are "turned off", it makes a person resistant or immune to certain viruses because they cannot latch onto the receptors. Migration • Genetic drift affects the genetic makeup of the population but, unlike natural selection, through an entirely random process. a.An ant gets stepped on. b.A rabbit gets swept up by a tornado. c.An elephant drinks up a protozoa living in a puddle. d.A plane crashes killing a Nobel Laureate. Bottleneck effect – sudden events that drastically reduce the population size. Example: natural disasters, chance event *survivors are usually not selected based upon genotype but rather by chance. Effects gene pool???? Founder effect A small group of females is separated from the original population and establishes a new population. ( isolated from original & caused by chance) Birds from mainland area move to an isolated island far out to sea Example: Many of the bird species found on Galapagos Islands Non random mating Natural Selection Natural selection at work Orchids fool wasps into "mating" with them. Katydids have camouflage to look like leaves. Non-poisonous king snakes mimic poisonous coral snakes The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby, thus reducing competition for nutrients and water. Artificial selection Long before Darwin and Wallace, farmers and breeders were using the idea of selection to cause major changes in the features of their plants and animals over the course of decades. Farmers and breeders allowed only the plants and animals with desirable characteristics to reproduce, causing the evolution of farm stock. This process is called artificial selection because people (instead of nature) select which organisms get to reproduce. As shown below, farmers have cultivated numerous popular crops from the wild mustard, by artificially selecting for certain attributes. • Artificial selection is the process of changing the characteristics of animals by artificial means. For example, animal breeders, are often able to change the characteristics of domestic animals by selecting for reproduction those individuals with the most desirable qualities such as speed in racehorses, milk production in cows, trail scenting in dogs. Golden saddleback only about 150 years old. 'barrel' more rounded than in other breeds • The Labradoodle was first deliberately bred in 1989, when Australian breeder Wally Conron first crossed the Labrador Retriever and Standard Poodle for Guide Dogs Victoria. His aim was to combine the low-shedding coat of the Poodle with the gentleness and trainability of the Labrador, and to provide a Guide Dog suitable for people with allergies to fur and dander. Guide Dogs Victoria continue to breed Labradoodles today and Labradoodles are now often used around the world as Guide, Assistance, and Therapy Dogsas well as being popular family dogs. Disruption of the genetic equilibrium leads to evolution Some evolutionary changes One example is vestigial structures. A vestigial structure is a feature that was an adaptation for the organism's ancestor, but that evolved to be non-functional because the organism's environment changed. Fish species that live in completely dark caves have vestigial, nonfunctional eyes. When their sighted ancestors ended up living in caves, there was no longer any natural selection that maintained the function of the fishes' eyes. So, fish with better sight no longer out-competed fish with worse sight. Today, these fish still have eyes — but they are not functional and are not an adaptation; they are just the by-products of the fishes' evolutionary history. homologous characters — characters in different organisms that are similar because they were inherited from a common ancestor from a common ancestor that also had that character. Birds, bats, mice, and crocodiles all have four limbs. Sharks and bony fish do not. The ancestor of tetrapods evolved four limbs, and its descendents have inherited that feature — so the presence of four limbs is a homology . Biologists use a few criteria to help them decide whether a shared morphological character (such as the presence of four limbs) is likely to be a homology Same basic structure The same bones (though differently shaped) support the limbs of mice and crocodiles. In the illustration of forelimbs at left, homologous bones are colored alike. Bird and bat wings are analogous — that is, they have separate evolutionary origins, but are superficially similar because they evolved to serve the same function. Analogies are the result of convergent evolution. Interestingly, though bird and bat wings are analogous as wings, as forelimbs they are homologous. Birds and bats did not inherit wings from a common ancestor with wings, but they did inherit forelimbs from a common ancestor with forelimbs. Formation of Species • Read article Geographic isolation The Satin bowerbird builds a channel between upright sticks, and decorates with bright blue objects MacGregor’s Bowerbird builds a tall tower of sticks and decorates with bits of charcoal. The evolution of different mating location, mating time, or mating rituals: Genetically-based changes to these aspects of mating could complete the process of reproductive isolation and speciation. For example, bowerbirds (shown above) construct elaborate bowers and decorate them with different colors in order to woo females. If two incipient species evolved differences in this mating ritual, it might permanently isolate them and complete the process of speciation. pre zygotic different mating times different mating call post zygotic offspring die early healthy but not fertile Types of evolution: Coevolution The term coevolution is used to describe cases where two (or more) species reciprocally affect each other's evolution. So for example, an evolutionary change in the morphology of a plant, might affect the morphology of an herbivore that eats the plant, which in turn might affect the evolution of the plant, which might affect the evolution of the herbivore...and so on. • Hummingbirds and ornithophilous flowers have evolved to form a mutualistic relationship. It is prevalent in the bird’s biology as well as in the flower’s. Hummingbird flowers have nectar chemistry associated with the bird’s diet. Their color and morphology also coincide with the bird’s vision and morphology. The blooming times of these ornithophilous flowers have also been found to coincide with hummingbirds' breeding seasons This system is probably the product of coevolution: the plants would not have evolved hollow thorns or nectar pores unless their evolution had been affected by the ants, and the ants would not have evolved herbivore defense behaviors unless their evolution had been affected by the plants. Convergent evolution Convergent evolution represents a phenomenon when two distinct species with differing ancestries evolve to display similar physical features. Traits arising through convergent evolution are termed analogous structures, in contrast to homologous structures, which have a common origin Convergent Evolution A small mantispid and a preying mantis. Although they differ greatly in size, these two insects are remarkably similar in appearance. They both have triangular heads with large eyes and a pair of raptorial (grasping) front legs. Their other two pairs of legs are used for walking. They belong to two very different insect orders. Although mantids were once placed in the order Orthoptera along with grasshoppers, crickets and cockroaches, they are now placed in the separate order Mantodea. Mantispids belong to the order Neuroptera, along with lacewings, snakeflies and antlions. Their remarkable adaptive similarity is an example of convergent evolution. Divergent Evolution • group from a specific population develops into a new species. In order to adapt to various environmental conditions. • Divergent evolution is the process of two or more related species becoming more and more dissimilar. The red fox and the kit fox provide and example of two species that have undergone divergent evolution. The red fox lives in mixed farmlands and forests, where its red color helps it blend in with surrounding trees. The kit fox lives on the plains and in the deserts, where its sandy color helps conceal it from prey and predators. The ears of the kit fox are larger than those of the red fox. The kit fox's large ears are an adaptation to its desert environment. The enlarged surface area of its ears helps the fox get rid of excess body heat. Similarities in structure indicate that the red fox and the kit fox had a common ancestor. As they adapted to different environments, the appearance of the two species diverged. Kit Fox Red fox • What can speed up divergent evolution? The next slides are cladograms Look up the definition