Sister taxa: any taxa derived from a common ancestral node.Lecture 10 BIO 311D 2nd EditionOutline of Last Lecture I. Different Definitions of SpeciesII. How do new species form?Outline of Current Lecture I. ReviewII. Reproductive isolating mechanismsIII. What is a phylogeny?IV. Interpreting cladograms Current LectureI. Review:- If a barrier is removed from two populations that were formed by allopatric speciation, how could you determine if the two populations had become separate species? Inability to interbreed - Adaptation (microevolution) of different subpopulations to slightly different habitats can lead toreproductive isolation by habitatI.e. grass in a mine waste soil vs. grass in an uncontaminated patch of soil; species may hang outmore in one area than another- To determine if speciation occur within plants: try to pollinate the plants with one another based on the biological species concept- Polyploidy occurs more commonly in plants plants produce their own gametes; self-fertilization; may reproduce asexually which makes it easier for a single mutant individual to pass on their genesII. Reproductive isolating mechanismsA. Pre-Zygotic (Premating) Isolating Mechanism 1. Habitat isolation2. Temporal isolation3. Behavioral isolation: many animals have mating signals only recognized by the same species 4. Mechanical isolation: the genitals structures just don’t fit together5. Gametic isolation: incompatible receptors on sperm and egg receptor B. Post-Zygotic Isolating Mechanism1. Hybrids not viable (embryo dies)2. Hybrid infertility i.e. mules (its amount of chromosomes differs from both parents, hinderingits ability to reproduce)3. Hybrid breakdown (cannot maintain a new population)III. What is a phylogeny?A. Terms - A phylogeny is an evolutionary history of species of a group of specieso A phylogeny is built by comparing traits that are present or absent in the groups being studied- Phylogenetic tree: a branching diagram that represents a hypothesis about evolutionary relationshipso Groups on a branch point together have a shared derived traits- Traits: two types either ancestral or derivedIV. Interpreting cladogramsOutgroup: a (monophyletic) group of organismsthat serves as a reference group for determination of the evolutionary relationship among three or more monophyletic groups of organisms.Sister taxa: any taxa derived from a common ancestral node.Polytomy: more than two branches emerging from the
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