One Week of BIOEE 1780 Notes
One Week of BIOEE 1780 Notes BIOEE1780: Evolutionary Biology
Popular in Biology: Evolution and Biodiversity
Popular in Biological Sciences
This 3 page Class Notes was uploaded by Carly Siege on Wednesday March 16, 2016. The Class Notes belongs to BIOEE1780: Evolutionary Biology at Cornell University taught by Dr.Sarvary in Spring 2016. Since its upload, it has received 15 views. For similar materials see Biology: Evolution and Biodiversity in Biological Sciences at Cornell University.
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Date Created: 03/16/16
a metapopulation is a group of population that are connected by gene ﬂow phylogenetic species concept: focuses on the phylogenetic history of organisms biological species concept: deﬁnes species as a group of actually or potentially interbreeding populations that are reproductively isolated from other such groups general lineage species concept: species are metapopulations of organisms that exchange alleles frequently enough that they comprise the same gene pool and the same evolutionary lineage the biological species model particularly helps us focus on the process of speciation- the splitting of one group of interbreeding lineages into two - by an isolating barrier Barriers to Gene ﬂow geographical barriers (extrinsic) mountains rivers, oceans, deserts physical separation that prevents gene ﬂow Allopatry - occurs when populations are in separate, nonoverlapping geographic area Physical isolation by vicariance Dispersal and Colonization reproductive barriers (intrinsic) mating preferences, hybrid incompatibilities evolutionary divergence prevents gene ﬂow Prezygotic isolating barriers that impeded gene transfer before sperm or pollen can be transferred to other species behavioral isolation: diﬀerences in behaviors that prevent members of diﬀerent species formatting, such s lack of attraction ecological isolation: isolating barriers that are by products of the ecology of diﬀerent species Mechanical Isolation: reproductive structures (genitalia, pollination structures) do not ﬁt together mechanically making it diﬃcult for fertilization to occur post mating: gametic isolation: Postzygotic isloating barriers that impeded gene transfer after spermor pollen has been transferred to other species hybrid availability: hybrids die before or shortly after birth hybrid sterility physiological sterility: hybrids suﬀer problems in the reproductive system or gametes behavioral sterility: hybrid suﬀer neurological or physiological defects that prevent them from ﬁnding mates Ecological speciation - the evolution of reproductive barriers between population by adaptation to diﬀerent environment or ecological niches AKA Sympatric speciation Hybrid Zones A hybrid zone exists where the ranges of two forms meet, interbreed, and create hybrid oﬀspring. These forms are populations that are genetically diﬀerentiated to some degree. Types of hybrid zones Secondary hybrid zone: Arises from secondary contact between two previously allopatric populations Primary hybrid zone: A primary hybrid zone is formed by selection on a previously homogeneous species across an environmental gradient Hybrid zones will create a cline in allele frequencies There will be a transition in the frequency of alleles, genotypes, or phenotypes along a geographical transect Clines can distinguish primary and secondary hybrid zones Clines for diﬀerent traits will not be concordant Clines will reﬂect diﬀerent types of ecological gradients, which are unlikely to overlap exactly Neutral traits will not show a cline Reinforcement - the increase of reproductive isolation between hybridizing forms through selection against hybrid oﬀspring Ecomorph: species with the same structural habitat/niche, similar in morphology and behavior - do not cluster together, meaning that they are not closely related - species on the same island generally cluster together, meaning they are closely related For a species to arise, something has to prevent or strongly limit between populations (extrinsic or intrinsic) changes in some traits keep species reproductively isolated one such trait is the anole’s dewlap, the colorful ﬂab of skin under the lizards throats Adaptive Radiation: when an ancestral species diversiﬁes into many descendant spaces that occupy diﬀerent environment habitats can be triggered by: - evolution of a new adaptation - vacated niches - specialization absorptive heterotrophy: a process that involves secreting digestive enzymes into the environment Convergent evolution – Diﬀerent groups of organisms can independently evolve similar traits by adap7ng to similar environments Fungi Paraphyletic: Eukarya that aren’t animals, fungi, or plants. Saprobic Fungi take up nutrients from non living organic matter important decomposer enzymes digest cellulose, lignin, keratin Parasitic Fungi take up nutrients by parasitic interactions obligate facultative plants are hosts of choice cordyceps create zombie ants Predatory Fungi fungi can be active predators by secreting digestive enzymes from their hyphae adhesive constricting ring Mutualistic Fungi symbiotic mutualism: when two species are in close association and both parties beneﬁt fungi (and photobiont) and lichen Microsporidia unicellular, tiniest eukaryotes Highly reduced fungi No functional mitochondria called mitosomes Intracellular parasites of animals Insects, crustaceans, ﬁshes chytrids paraphyletic group aquatic single or multicellular chytrids funges: responsible for amphibian population crashes Dikarya sac fungi (Ascomycota) morels, most yeasts, lichen synapomorphy: the ascus (cell where meiosis occurs) contains several fungal rock stars morel mushrooms Saccharomyces cerevisiae: baking and brewing industries (not to men7on molecular developmental biology) Penicillium chrysogenum, producer of penicillin Candida albicans, cause of thrush, diaper rash Cryphonectria parasitica, chestnut blight Club fungi (Basidiomycota) true fungi: mushrooms … edible and poisonous synapomorphy: the basidium (cell in which meiosis occurs) Arbuscular mycorrhizal crucial economically for plants world wide Arbuscules: site of nutrient exchange have infected 90% of plants penetrate cell wall but not plasma membrane fungus gets the products of photosynthesis plant gets increased surface area for soil nutrients/moisutre
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