How to Ace AP Biology: Speciation and Reproduction

Check out our mobile app. Over 850 AP Biology questions with detailed feedback for every question. It will help you throughout the year. Free to install. https://apps.apple.com/us/app/whipsma... •What is the difference between geographic isolation and habitat differentiation? •How does polyploidy contribute to speciation? •The sympatric speciation phenomenon most commonly occurs through ________. •_______ is the process by which natural selection increases reproductive isolation. •Explain the concept of punctuated equilibrium. Speciation Speciation is the evolutionary process by which populations evolve to become distinct species. This can involve even the most minute changes to a single gene. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within lineages. A phenotypic trait must change in order to produce a different species. Sympatric speciation occurs when populations of a species that share the same habitat become reproductively isolated from each other. This speciation forces the environmental barrier of habitat differentiation. The sympatric speciation phenomenon most commonly occurs through polyploidy, in which an offspring or group of offspring will be produced with twice the normal number of chromosomes (accident during nuclear division). Allopatric speciation, also referred to as geographic speciation, vicariant speciation, or its earlier name, the dumbbell model, is a mode of speciation that occurs when biological populations become geographically isolated from each other to an extent that prevents or interferes with gene flow. The difference between geographic isolation and habitat differentiation is the relative locations of two populations as speciation occurs. Geographical isolation blocks all gene flow between the populations. Habitat isolation, on the other hand, offers the chance of gene flow between populations that are in close proximity. Polyploidy is common among plants and has been a major source of speciation (sympatric) in the angiosperms. Polyploidy is a condition in which the cells of an organism have more than two paired sets of chromosomes. Most species whose cells have nuclei eukaryotes are diploid, meaning they have two sets of chromosomes—one set inherited from each parent. However, some organisms are polyploid, and polyploidy is especially common in plants. The prefix –poly means many. Punctuated equilibrium is a theory that states that evolution occurs primarily through short bursts of intense speciation, followed by lengthy periods of stasis or equilibrium. It postulates that nearly 99% of a species time on earth is spent in stasis. So, if a species appears in fossil records for about 10 million years, it is likely that speciation occurred over the span of fewer than 100,000 years. Reproduction In sexual reproduction, new organisms are formed by the fusion of haploid sperm and eggs. This is the result of two different organisms reproducing to form one organism, resulting in the decline of species diversity. Sexual selection is a type of natural selection that occurs through preference by one sex for certain characteristics in individuals of the other sex. This is the most likely explanation of sympatric speciation because the population would become reproductively isolated from each other. Behavioral isolation is a postzygotic reproductive barrier that is usually in the form of mating signals/rituals. Reinforcement is the process by which natural selection increases reproductive isolation. Therefore, gene flow would decrease because there will be little to no transfer of alleles or genes from one population to another. #apbiology #speciation #reproduction #speciation