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Lecture 6

Biology Lecture 6 Article 2.docx

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Scott Browning

BIOLOGY LECTURE #6 Causes and Consequences of Dispersal in Plants + Animals Dispersal: movement of individual away from pop where they were bon to diff location where they will settle + reproduct - Common forms: NATAL OR DISPERSOAL - NATAL: first movement ever from its birth site to the site it first attempts to reproduction - ADULT DISPERSAL: changing location in space after reaching repro maturity and moving from one habitat patch to another - *GAMETE DISPERSAL: non-motile adults (plants) - Relocation to a new site = adaptive trait Active vs Passive Active: movement of the entire organism on its own (adult + juvenile animals) - Vary among species depending on factors like social structure Ex) social systems that rely on only one adult male for R force younger males to disperse - Density-dependent process where magnitude depends on a local pop size, resource competition, and habitat quality/size - Local pop conditions may affect juvenile + adult DIFF, so vary between age groups - Highly vagile = most efficient at active dispersal= greatest cap for long distance dispersal - Animals that can’t fly also considered highly vagile Ex) large aquatic animals + some terrestrial can disperse large distance on foot - Habitat is a factor because there can be restrictions - Flying animals less affected cause can fly past barriers - Not many barriers in ocean - Dispersal by land animals considered less effective/energy efficient…. Forced to travel thru unfavorable habitats with potential barriers Passive: plants + animals that can’t move but use dispersal unites AKA DISSEMINULES to aid in repro/exploitation of new habitats - DISS adapted for movements by specific agents in enviro: wind, water, animal, OR may have motile larval stage - Sessile adult animals (sponges + marine invert) use passive: DISS are used in repro Ex) corals sexually repro by releasing gametes into water, male’s are motile but eggs move passively by ocean currents - OR… use natal dispersal: free-living, aquatic juvenile stage, larvae drift near surface and passively carried by water to other places - Plants, diss = seeds, spores, fruits, all with mods for movement away from parent thru enviro’s KE - Velocity + dir of movement of dispersal agent = distance travelled - Wind, flying animals, water current = SUCCESSFUL LONG DISTANCE PASSIVE DISPERSAL AGENT Ex) Mod in Hypo radicata lets it move in a fragmented landscape and counteract negative effects of pop isolation with lots of gene flow - Hairs… sticky… barbed seeds - Some diss released over short distances and other fall to ground at base - Scattered during feeding and distributed in poop - Seeds adapted to resist digestive juices - Distance indefinite + depends on dispersal behavior of host (nomadic vs. brief dispersal trajectory) To Disperse or Not to Disperse… That is the Question Bitch Influences: - Local pop conditions (crowding + food availability) - Climate Change - General warming trend because of global climate change will cause specie’s range to shift - Areas outside range will be more suitable now… BUT MAY BE BEYOND REACH - Environmental unknowns (weather, species interaction) - Contributes to conditions in local enviro + effects changes in dispersal + behavior (phen like migration) - If you emigrate because of enviro conditions you might get better conditions in a new place - Avoidance of inbreeding + inbreeding depression - Small pops can become inbred = decreased fitness, BUT DISPERSAL CAN COUNTERACT NEGATIVE EFFECTS - Dispersal can reduce competition for resources + mates = INCREASING INDIVIDUAL FITNESS - Local Scale: inclusive fitness benefits by decreasing comp among
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