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Chapter 5

SNES 1101 Chapter Notes - Chapter 5: Parasitoid, Minimum Viable Population, Ecological Succession


Department
Science of Natural & Environmental Systems
Course Code
SNES 1101
Professor
madsen
Chapter
5

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Chapter 5 - Biodiversity, species interactions, population control
5 basic types of interactions between species
1. Interspecific competition - when members of two or more species interact to gain access
to the same limited resources, such as food, light, or space.
2. Predation - when a member of one species (the predator) feeds directly on all or part of
a member of another species (the prey).
3. Parasitism - when one organism (the parasite) feeds on the body of, or the energy used
by, another organism (the host), usually by living on or in the host.
4. Mutualism - an interaction that benefits both species by providing each with food,
shelter, or some other resource
5. Commensalism - an interaction that benefits one species but has little or no impact on
the other
Competition
- most common interaction between species.
- outcome: one species becomes better or fitter
Competitive exclusion principle - no two species can occupy exactly the same niche for a long
time
Predator-prey relationship - predators eat preys
Methods for carnivores to predate:
pursuit
ambush
camouflage
chemical warfare (poison)
Warning coloration - species enable experienced predators to recognize and avoid them
Predation plays a role in evolution by natural selection
- kills the “unfits”, leaves the “fits”
- predators control the populations of preys
Coevolution
- both predators and preys develop counter-strategy/appearance against each other
- one natural way maintaining sustainability
- promote biodiversity by increasing species diversity
Parasites
- promote biodiversity, keep hosts’ populations in check
- host interaction promotes coevolutionary change
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Gut inhabitant mutualism
- bacteria in the digestive system of animals help to break down (digest) their hosts’ food
Resource partitioning
- occurs when species competing for similar scarce resources at different times, in
different ways, in different places
Population dynamics
- a study of how these characteristic of populations change in response to changes in
environmental conditions
3 general patterns of population distribution (dispersion)
- clumping = individuals live in clumps to increase the chance of survival
- uniform dispersion = live in a uniformed pattern
- random dispersion = just random
Population change = (Births + Immigration) - (Deaths + Emigration)
Age structure
- the proportions of individuals at various age
- described in terms of reproductivity:
- pre-reproductive, reproductive, post-reproductive
Stable population - even in all three reproductive ages
Biotic potential - capacity for population growth under ideal conditions
- larger size (of an organism) = small potential
- smaller size (of an organism) = large potential
Intrinsic rate of increase [r]
- the rate at which the population of a species would grow if it had unlimited resources
High rate = reproduce early, produce many times, more offsprings with shorter life span
Low rate = reproduce late, produce less times, less offspring with longer life span
No population can grow indefinitely, because of
- limitation on resources
- competition with other species
- there are always limits to population growth in nature
Environmental resistance
- the combination of all factors that act to limit the growth of a population
Carry capacity (K)
- the maximum population of a given species that a particular habitat can sustain
indefinitely without being degraded
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