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Lecture 17

BIOL215 Lecture 17 Notes.pdf

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McGill University
Biology (Sci)
BIOL 215
Neil Price

BIOL215 Lecture 17 Notes Based on the Rosenzwieg-McArthur model, as you have more and more prey, there is stronger and stronger intraspecific competition, so to stabilize the population of prey, you need less predators which is why the curve goes down Mutualism interaction is when coexistence is beneficial to both species. For the grouper and small fish example, we are not saying that the relationship is an obligatory mutualism; both the small fish and grouper can live apart and do fine. However, they will do better when they are living together • Mycorrhizae as a mutualistic interaction. Mycorrhizae fungi provide plants with greater access to inorganic nutrients and are important to plant performance Herbivory interaction: Herbivore consumes its prey but does not always kill it. Herbivore is a mild form of predation Predation interaction: Predator kills and consumes its prey. The herbivore-plant relation is one of predation There is a high metabolic cost to defend oneself. The production of thorn takes energy, nutrients. Thus, the plant's fitness level overall will decrease. A good example of a plastic functional response in this case to herbivory suggests that herbivore will have a big impact on the growth of plants The hypothesis of overcompensation in plant responses comes from the idea that herbivores may not be all together so negative for plants. It suggests to a certain extent that as grazing pressure increases, it might even be beneficial and lead to an increase in production. This may be due to intraspecific and interspecific competition Serengeti Plains is a good example of the herbivory interaction linked with the overcompensation in plant responses due to grazing (Zebra eat first, then wildebeest, then Thomson’s gazelle) Parasitism interaction: Predators, parasites and pathogens influence the structure, abundance, and distribution of population. It is a form of predation. At times, it may lead to killing the prey, but this does not always happen Parasite: An organism living in with or on another organism, obtaining benefit from it and usually injuring it (i.e. Lamprey) Parasitoid: An insect (wasp) that complete its larval-development within the body of another insect eventually killing it A number of parasites and pathogens will alter the behavior of the hosts to benefits their own life- cycle For simple models of population regulation, if the birth and death rate curves do not cross, the population will either increase to infinity or decrease to extinction Interspecific, intraspecific, and predation is basically density dependent. This suggests that death and birth rate may change as we change population Two general rules for simple models of population regulation: • Populat
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