BISC208 Lecture 3: Lecture 3

• School: University of Delaware
• Department: Biological Sciences
• Course: BISC208
• Professor: Safran Catherine

Document Summary

Evolution of existing species and extinction of species. Organisms belonging to a species have: a unique set of attributes, common evolutionary history, genetic similarity, can intercross and produce a viable and fertile offspring. What should be considered to define species: morphological traits (comparative biology, molecular features. When they become orthologs they are no longer the same species: ecological/environmental factors. Changes in habitat can change morphological features: evolutionary relationships between ancestral and modern species (phylogenetic trees) Gaps in the fossil record: ability to interbreed vs. reproductive isolation. How are individual species maintained: reproductive isolating mechanisms. Temporal isolation: best time to reproduce isn"t always the same. Hybrid sterility (offspring of parents is viable, but is unable to reproduce) male donkey + female horse = mule: equus (genus) asinus (species) , hybrid vigor: advantageous to breed two different species. Hybrid breakdown (a hybrid that is viable and fertile in the first generation, but cannot reproduce in f2)