Transcript Understanding Populations Section 2 Predation

Understanding Populations
Section 2
Objectives
• Explain the difference between niche and habitat.
• Describe the five major types of interactions between
species.
• Explain the difference between parasitism and
predation.
• Explain how symbiotic relationships may evolve.
Understanding Populations
An Organism’s Niche
• unique position occupied by a species
– habitat and ecological function (role)
– ‘job’ of a particular species in an ecosystem
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Understanding Populations
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Ways in Which Species Interact
• Five major types: based on benefit / harm to the other
species
• Competition
• Predation
• Parasitism
• Mutualism
• Commensalism
• Other types of interactions are possible
• Many interactions between species are indirect
Understanding Populations
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Competition
• relationship between two species (or individuals)
– both attempt to use the same limited resource
– both are negatively affected
• members of the same species must compete: same
niche
• different species compete when niches overlap: use
some of the same resources
Understanding Populations
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Indirect Competition
• Use of same resource at different times or without direct
contact
– Ex: Humans and the insects that eat our food crops
Understanding Populations
Adaptations to Competition
• advantageous for species
whose niches overlap to
divide up the niche in time or
space
• Niche restriction: each
species uses less of the niche
than they are capable of
using
– observed in closely related
species in same habitat
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Understanding Populations
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Predation
• an interaction where one species, the predator, feeds on
the other species, the prey
• most organisms have evolved some mechanisms to
avoid or defend against predators
• predators with a specific type of prey tend to increase
and decrease in a linked pattern
Understanding Populations
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Parasitism
• Parasite: organism that lives in or on another organism
and feeds on that organism
– spends some of its life in or on the host
– Ex: ticks, fleas, tapeworms, heartworms, leeches
• Host : organisms the parasite feeds on
– often weakened or exposed to disease as a result
• Parasitism: relationship where parasite benefits, host is
harmed (usually not killed)
Understanding Populations
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Mutualism
• a relationship in which both species benefit
• many species depend on each other for survival
– Ex: bacteria in human intestines
• help us break down food we cannot digest
• we provide food-rich habitat
Understanding Populations
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Commensalism
• relationship in which one organism benefits and the
other in unaffected
• Ex: sharks and remoras (a fish)
– Remoras attach themselves to sharks
– Feed on scraps of food left over from shark’s meals
Understanding Populations
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Symbiosis and Coevolution
• Symbiosis: two different organisms live in close
association with each other
• often used to describe a relationship in which at least
one species benefits
• Coevolution: species evolve adaptations that reduce
the harm or improve the benefit of the relationship