Lecture 10 BIO 311D 2nd Edition Outline of Last Lecture I Different Definitions of Species II How do new species form Outline of Current Lecture I Review II Reproductive isolating mechanisms III What is a phylogeny IV Interpreting cladograms Current Lecture I 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 to reproductive isolation by habitat I e grass in a mine waste soil vs grass in an uncontaminated patch of soil species may hang out more 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 selffertilization may reproduce asexually which makes it easier for a single mutant individual to pass on their genes II Reproductive isolating mechanisms A Pre Zygotic Premating Isolating Mechanism 1 Habitat isolation 2 Temporal isolation 3 Behavioral isolation many animals have mating signals only recognized by the same species 4 Mechanical isolation the genitals structures just don t fit together 5 Gametic isolation incompatible receptors on sperm and egg receptor B Post Zygotic Isolating Mechanism 1 Hybrids not viable embryo dies 2 Hybrid infertility i e mules its amount of chromosomes differs from both parents hindering its ability to reproduce 3 Hybrid breakdown cannot maintain a new population III IV What is a phylogeny A Terms A phylogeny is an evolutionary history of species of a group of species o 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 relationships o Groups on a branch point together have a shared derived traits Traits two types either ancestral or derived Interpreting cladograms Outgroup a monophyletic group of organisms that 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 node
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