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BIOL 103
Peter T Boag

LECTURE 1 Important Terminology (Definitions) Evolution  Accumulation of inherited changes in populations over time, leading to related species. The pattern of evolution is an accepted fact in science. The theory that „evolution by natural selection‟ is the dominant mechanism for evolution acknowledges that other processes contribute to evolutionary change. Darwinian Fitness  An individual‟s ability to survive and reproduce relative to other members of a population Population  Group of individuals of one species in a given area* Species  Groups of populations composed of organisms with common ancestry, sharing similar structures, functions, behaviours, etc. and able to freely interbreed. Community  Group of species that live together & interact in a given area Ecosystem  An interactive system composed of one or more communities and their abiotic (physical) environment Biosphere  All of Earth‟s ecosystems taken together. Lecture 2 Theory of Evolution by Natural Selection  Proposed by both Darwin and Wallace  Based on four observations o Variation in phenotype (size, shape, behaviour) exists among individuals o High reproductive potential means populations increase geometrically o Individuals compete for limited resources o „Fit‟ offspring with characteristics (phenotypes) matching current environment more likely to survive and reproduce  Additional Assumptions: o Natural selection acts on phenotypes within a generation; variation must be at least partly heritable for natural selection to result in evolutionary change between generations (but the mechanism of inheritance was a mystery to Darwin) o Small evolutionary changes in populations can occur rapidly, but complex adaptation require accumulation of multiple changes over thousands of generations; Earth’s vast age makes this feasible  Evidence Supporting Evolution o 90% of supporting evidence is “background material” – contemporary evidence and Darwin‟s evidence in Origin. o Fossil Record  Most direct evidence; back in Darwin‟s time and today.  During Darwin‟s time, Charles Liles who inspired Darwin‟s work  Modern geologists uncovering stratigraphic layers of limestone rock; in the most recent layers that are similar to present day, lower = more different and representing other taxa that are no longer present on Earth.  There is progression from earliest unicellular organisms to complex animals  E.g. – evolution of whales Page 1 of 6  Whales and hippos evolved in parallel from ancient Artiodactyl (cloven-hoofed mammals)  Fossilization is a very rare process; therefore fossil record is “patchy” o Biogeography  Source of information about how evolution worked on a larger scale  Darwin had a bit of awareness, more detail in modern times o Selective Breeding  Darwin was aware of this (living in the rural areas); ability to produce different breeds of livestock, crops etc  Very different phenotypically looking animals, crops etc  Natural selection similar to selective breeding  Selective/Artificial  there is a directed processes “designer”; with a particular goal in mind. Therefore progressive aspect to it.  Natural Selection  “looks like it is becoming more complex & more successful organisms”. It is a random phenomenon and only favours particular individuals that survive best under the given environmental conditions  Ex. Artificial selection on wild Brassica: Process  Wild Brassica oleracea  to Broccoli; (extremely large, compact flowering stalks) o Convergent Evolution  Similar environments can produce organisms with similar abilities, appearances even though starting with completely different genetic background  Unrelated mammals eat ants & termites in similar ways & display many other structural & functional similarities  Anteaters that are not related according to molecular genetics. o Homologies  Anatomical  Developmental  Molecular  *All direct evidence  Deep Time o Impossible for Darwin to grasp vast time spans available for evolutionary change o 1 day = 12.6 million years o 1 second = 143 years  Geographic Distribution & Evolutionary History (linked to biogeography) o Current distribution of flightless „ratite‟ birds best explained by ancient Gondwana & break-up 130 – 80 mya o Darwin was puzzled why similar flightless birds were thousands of miles away o Understanding of plate tectonics, supports the Theory of Evolution o Good example of adaptive radiation, allopatrically  Comparative Anatomy o Homologous features  Derive from same structure in common ancestor  Different organs, bones, features  “Developmental Biology”  *Distinguishing truly homologous features (same embryological origin) and analogous features  Homology in animals  there is gene regulation o Analogous features  Similar functions in distantly related organisms result of convergent evolution Page 2 of 6  Analogous traits: similarities result from convergent evolution o Vestigial structure  Remnants of structures indicate adaptations wax and wane as environments change  Appendix has been preserved: gastro-intestinal disease; acts as a reservoir of beneficial bacteria. o Homology in animal genes  Def: homologous traits: similarities are inherited from a common ancestor  Homeotic genes underlie development of „universal body plan‟ in all animals  Evidence for evolution from developmental & molecular biology o Development reveals ancestral structures no longer obvious in adults o Protein & DNA sequences contain records of evolutionary change o Phylogeny  Evolutionary history of group of related species, displayed as Phylogenetic trees  Diagrams showing lines of descent based on molecular data  Developmental Homology o Species that differ as adults often bear similarities as embryos o Gill ridges in human embryos indicate humans evolved from aquatic animal with gill slits o Human embryos have long bony tails; features distinguishing species often appear later in development o Today, there is a conservation of homeotic genes responsible in part for embryo similarity Closing Notes - Individuals do not evolve; populations evolve as the relative frequency of individuals w/ heritable differences changes - Adaptations are: o Evolved characteristics enhancing an organism‟s survival or reproduction in a particular environment Lecture 3 Variation and Natural Selection in Populations Key Definitions:  Phenotype
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