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Lecture

Causes and Consequences of Dispersal in Plants and Animals Notes.docx

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Department
Biology
Course
BIO120H1
Professor
Paul Thompson
Semester
Fall

Description
Causes and Consequences of Dispersal in Plants and Animals: - Dispersal – ecological process where individual or multiple individuals move away from the population in which they were born to another location/population, where they settle and reproduce - 2 common forms: o natal dispersal – first movement where it first attempts to reproduce (permanent) o breeding dispersal – changing location in space after reaching reproductive maturity, usually involving movement from one habitat patch to another - another type of dispersal: gamete dispersal (doesn’t fall into these categories) – common for non-motile adults, such as plants ****(relocation considered to be an adaptive trait)**** Active Dispersal:  movement of entire organism through its own ability and is common in both adult/juvenile animals  Degree of dispersal varies among species depending on factors and social structure o Harem Breeding System: social systems that require a single male for reproduction (gorillas/primates) and force most juvenile males to disperse since they aren’t all required  Is density-dependant process - depends on local pop size, resource competition, habitat quality/size  Consist of animals that highly vagile (able to move about or disperse in a given environment)  most efficient at active dispersal (birds, bats, large insects, large aquatic animals, terrestrial animals) o For ex. Monarch butterfly fly many kilometers  Flying animals affected less by habitat changes  they can bypass barriers by flying over them o Fewer barriers on ocean than on land; aquatic animals can disperse better than land animals; land animals expected to travel through unfavourable habitats with geographic barriers = inefficient Passive Dispersal:  involves plants and animals that can’t move themselves but have dispersal units called disseminules to aid in reproduction or the exploitation of new habitats  Many disseminules adapted for movement by specific dispersal agents available in the environment such as wind, water or another animal capable of active dispersal, or species with more motile larval stage o Sponges and corals (immobile marine invertebrates) have disseminules that are buds/cells used in reproduction  Corals reproduce by releasing gametes into water  males gametes are motile and eggs move via ocean currents o Other aquatics have free-living juvenile stage where larvae drift near surface and are passively carried to other locations  Plants disseminules include seeds, spores, and fruits – all move away via environmental kinetic energy o Distance traveled is result of velocity and direction of movement by dispersal agent o Winds, flying animals or water currents most successful long-distance dispersal agents  Seeds and fruits with wings, hairs or inflated processes are carried by wind o others have sticky or barbed seeds, or fruits, that adhere to feathers or fur of mobile animals  some seeds released over short distances or fall to base of plant o on floor, animals compete for fruit/seeds  seeds adapted to resist digestive juices and thus disperse through
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