Introduction to Evolution PDF

## Species Interact in Communities Sometimes, adaptations in one species select for adaptations in another. A genetic change in one species selects for a subsequent change in a different species can occur. The two species evolve together in a process called coevolution. ## Major changes in body fo...

## Species Interact in Communities Sometimes, adaptations in one species select for adaptations in another. A genetic change in one species selects for a subsequent change in a different species can occur. The two species evolve together in a process called coevolution. ## Major changes in body form can result from changes in the sequences and regulation of developmental genes **Evolutionary Effects of Development Genes** * Genes that program developmental control the rate, timing, and spatial pattern of changes in an organism's form as it develops into an adult ## Changes in Rate and Timing * Heterochrony is an evolutionary change in the rate or timing of developmental events * The contrasting shapes of human and chimpanzee skulls are the result of small changes in relative growth rates ## Speciation: Processes and Rates ### Speciation Rates Niles Eldredge and Stephen Jay Gould proposed punctuated equilibrium as a theory of evolutionary biology. **Punctuated equilibrium:** sexually reproducing populations experience little change for most of their geological history, and that when phenotypic evolution does occur, it is localized in rare, rapid events of branching speciation (called cladogenesis). This mode of evolution is rapid and develops few if any intermediate forms. **Phyletic gradualism:** Contrasts with punctuated equilibrium, because it states that evolution generally occurs uniformly and by the steady and gradual transformation of whole lineages (anagenesis). ## Parapatric speciation * Part of a population enters a new habitat bordering the range of the parent species. * The border group possesses a unique combinations of traits. * Little greenbul of Cameroon ## Sympatric speciation * Populations diverge genetically while living in the same physical area. * Cichlids in Cameroon - microenvironments ## Allopatric Speciation **Dispersal:** * A small population diverges genetically from a parent population **Vicariance:** * Separate populations diverge genetically ## The most scientifically useful and the most specific division of classification is the species concept. **Allopatric speciation:** emphasizes disruption of gene flow between populations, usually by some sort of physical barrier. **Sympatric speciation:** involves the rise of a daughter species from a group of individuals within the geographic range of an ancestral species. **Parapatric speciation:** a daughter species might arise through hybridization of two populations. ## What makes a species? * **Species are:** - populations of organisms that interbreed with each other - or could possibly breed, under natural conditions, - and are reproductively isolated from other such groups. ## The Organization of Life * **A paleontological species** use morphology (what it looks like) instead of the basic biological definition. * The **species** is the basic level on which macroevolutionary processes operate ## Domain Eukarya * **Animals** * **Fungi** * **Plants** * **Protista** ## Species and speciation * **Biological species concept:** - Ernst Mayr - Population, or group of populations, whose members can interbreed and produce fertile offspring. - Speciation occurs when some members of a population can no longer interbreed. * Microevolution leads into macroevolution ## Anatomical Record * **Vestigial organs (Vestiges):** Structures that are no longer in use, diminished or reduced during the course of evolution, such as muscles in the ears, wisdom teeth, remnant limbs in snakes and whales, and our tailbone.  * **Atavistic organs (Atavisms):** A reversion to an ancestral character state not evident in recent generations. Structures that existed in organisms anciently, but no longer exist in the modern forms, but the genes for those traits still exist in the genome of those modern organisms. Rarely and occasionally atavisms occur in those modern organisms when a quiescent gene or genes expresses that unique trait. Examples are chicken's teeth, horse's toes and whale limbs that are expressed as visible traits. ## Convergent evolution: many paths to one goal * **Convergent evolution:** organisms have similar characteristics because they evolved in similar environmental conditions, although they are not closely related. Species that live in similar habitats will experience similar selection pressures from their environment, so they may evolve similar adaptations, or converge, coming to look and behave very much alike even though they are unrelated. ## Analogous Structures * Similar adaptations in organisms that do not share the same evolutionary history. * Function not form * Structures evolved independently and structures develop from natural selection and are not from a common ancestral trait. * Resemble each other as a result of parallel evolutionary adaptations to similar environments. * **Due to convergent evolution** Bird wings and insect wings. ## Homologous Structures * Similarity between 2 structures reflect common ancestry * Different modern vertebrates share many anatomical similarities - share common ancestor that originated this organization. * **Form not Function** - Structures may not have the same function ## Evidence of Biological Evolution and Natural Selection * **Homologous structures (form):** Morphological features in biological organisms that have a similar position and evolutionary origin, but not necessarily identical structure or the same function. * **Analogous structures (function):** in organisms have essentially the same function, but different evolutionary origins. Birds, bats, and insects have all evolved wings for flight, but they have done so by different evolutionary means. ## Coywolf * New DNA research shows all eastern coyotes are a combination of coyotes, wolves, and dogs! * There are three distinct species intermingled into the hybrid commonly referred to as the coywolf. * The percentages vary depending on the test and the dog's region. ## The bush dog (Speothos venaticus) * A canine found in Central and South America. * In spite of its extensive range, it is very rare in most areas except in Suriname, Guyana and Peru . * The bush dog is the only living species in the genus Speothos, and genetic evidence suggests that its closest living relative is the maned wolf of central South America or the African wild dog. * Bush dogs have partially webbed toes, which allow them to swim more efficiently. ## The role of small dogs * Popular belief has been that small dogs, such as Pomeranians and Chihuahuas, exist because once dogs were domesticated, humans wanted small, cute companions. * Researchers at the National Institutes of Health (NIH) identify a genetic mutation in a growth hormone-regulating gene that corresponds to small body size in dogs that was present in wolves over 50,000 years ago, long before domestication. ## Artificial selection in plants * **Wild mustard** * **Broccoli** * **Brussels sprouts** * **Cauliflower** * **Kale** * **Cabbage**