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Lecture 16

Ecology Lecture 16.doc

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University of Guelph
BIOL 2060

Ecology Lecture 16 Species Interactions Exploitative Interactions: one species benefits at the expense of the other (1) Predation (2) Herbivory (3) Parasitism Types of Exploitative Interactions (A) Categories of heterotrophic organisms: Carnivore – consumes other consumers Herbivore – consumes producers Omnivore – consumes producers & consumers (B) Functional classifications of predator: True predator – carnivore Grazer/browser – leaves/bark/branches Seed predator/planktivore – entire plants/plankton (anything that eats seeds) Parasite – relies on host for sustenance Parasitoid – parasite that ultimately kills host Types of Exploitative Interactions 1. Herbivores: consumers (primary) of plants; grazer vs. browser 2. Grainivory: seed predators, planktivores 3. Carnivores: consumers/predators (secondary & higher) i. Cannibalism: consumers that prey on the same species ii. Intraguild predation: consumers that compete/prey on each other 4. Parasitoids: parasites that use/kill host to rear young 5. Parasites: consumers that use the host’s resources Paracitism  A non-mutual relationship between species, where the parasite (+) benefits at the expense of the host (-). - Parasites are usually smaller than hosts, which they live on/in for an extended period, & do not kill them. - Parasites show a high degree of specialization, & reproduce at a faster rate than their hosts. - Macroparasites (protozoa, helminths, mistletoe) vs. microparasites (viruses & bacteria) - Host response: inflammatory response (body tissue responds quickly) &/or immune response (attacks foreign cell proteins – can flip coat proteins) Animal Parasitism - Hosts are the habitats for parasites - Ectoparasites are those that live on the host’s skin within the protectivee cover of feathers & hair - Endoparasites live within the host (beneath skin, bloodstream, mouthparts, gills) - Keloptoparasitism: stealing food - Blood parasitism: laying eggs in host’s nest Plant Parasitism - Parasitic plants derive some or all of their nutrition from anothr plant using a modified root (haustorium) that penetrates the host plant (roots, leaves, fruit, etc.) - Hemiparasitic plants are photosynthetic plants that still contain chlorophyll & can undergo photosynthesis (e.g. dwarf mistletoe)  Use water & water-bourne nutrients that are in the host - Holoparasitic plants are non-photosynthetic (e.g. cancer root, dodder, broomrape)  Depends on host for survival  You will never know it’s there unless its flowering Parasitism - Transmission Transmission of a parasite: (1) Direct contact with a carrier, or the parasite can be dispersed through the air, water, or other substrate (e.g. microparasites) (2) Indirect transmission via an intermediate organism or (vector) (e.g. insect vectors also transmit parasites among plants, malaria, etc.) - The definitive host is the host species in which the parasite becomes an adult & reaches maturity - Intermediate hosts harbour some developmental phase Parasitism – Impacts on Host - Parasites do not kill hosts outright but may do so in transmission - e.g. Nematodes – causes ants to turn red & raise gaster (looks like berry) Toxoplasma – causes rats to be attracted to cat urine Dicrocoelium – causes ants to climb to the top of grass blade - Parasites reduce growth/reproduction of the host (male/female) - Increased host mortality from a variety of indirect consequences - e.g. Killfish infected with trematodes exhibit surfacing & jerking swimming behaviour that attracts fish-eating birds (definitive host) Herbivory - Herbivory is a form of predation, though herbivores typically do not usually kill the individuals they feed on. - Grazers consume leafy parts of the plant - Browsers consume bark/woody parts of the plant - Seed predators & planktivores function as the true predators because they kill the plant or algae. - Autotroph–herbivore interactions are a key component of all communities Herbivory – Impacts - Intensity of grazing can be intense at times - Biomass is consume
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