community interactions
DESCRIPTION
Community Interactions. Communities. Habitat is the environment in which an organism lives. A population's niche is its role in the community How it uses the biotic and abiotic resources of its habitat. Community interactions. - PowerPoint PPT PresentationTRANSCRIPT
Community Interactions
• Habitat is the environment in which an organism lives.
• A population's niche is its role in the community– How it uses the biotic and abiotic resources of its
habitat
Communities
• There are five main types of relationships among species within communities– Competition– Predation– Parasitism– Commensalism – Mutualism
Community interactions
Community interactionsInterspecific competition occurs between two populations if they both require the
same limited resource
Intraspecific competition occurs between organisms of the same species.
• The competitive exclusion principle
– Populations of two species cannot coexist in a community if their niches are nearly identical
Figure 36.2
Hightide
Chthamalus
Balanus
Lowtide
Ocean
• Competition between species with identical niches has two possible outcomes
– One population will eventually eliminate the other
– Natural selection may lead to resource partitioning (division)
• Predation is an interaction where one species eats another– consumer = predator– food species = prey
Predation
• Prey gain protection against predators through a variety of defense mechanisms
1. Mechanical defenses, such as the quills of a porcupine
Adaptations are driven by these relationships…COEVOLUTION!
2. Chemical defenses
– Animals are often brightly colored to warn predators
– Example: the poison-arrow frog
Physical/Chemical Combat
3. Camouflage
– Example: gray tree frog
Figure 36.3C
Camouflage
4. Batesian mimicry occurs when a harmless species mimics a harmful one
– mimicry can involve behavior
– hawkmoth larva puffs up its head to mimic the head of a snake
Figure 36.3D
Trickery/Mimicry
• Eliminates weaker individuals• keystone predator maintains
diversity by reducing numbers of the strongest competitors in a community
- Ex. sea star is a keystone predator
How does predation affect the community?
Figure 36.4A
• Predation by killer whales on sea otters, allowing sea urchins to overgraze on kelp–Sea otters represent
the keystone species
Parasitism
• Parasitism is a form of predation– Parasite, host– Not immediately lethal– Example: mistletoe on oaks, tapeworm in human
intestine
• Commensalism - one partner benefits and the other is unaffected
• Examples
- Algae that grow on the shells of sea turtles
– Barnacles that attach to whales
– Birds that feed on insects flushed out of the grass by grazing cattle
• Mutualism:both partners benefit
Examples:
- Nitrogen-fixing bacteria and legumes
– Acacia trees and the ants of the genus Pseudomyrmex
Figure 36.5B
Symbiosis• Any long term biological interaction is known
as symbiosis or a symbiotic relationship• Some biologists only characterize mutualism
and commensalism as symbiosis• Others include parasitism as well• Endosymbiosis is the theory that several
eukaryotic organelles are the result of a symbiotic relationship between specialized prokaryotic cells.
Your task…• Community Interaction comic• Pick one of the types of interactions we discussed.
(competition, predation, parasitism, mutualism, commensalism)
• Draw a comic showing the interaction.• Comic must have at least three panels• No words are necessary, but it must clearly show the
type of interaction• Do not write the type of interaction on your comic or
your name• When it is finished, bring it to me for a number and
further directions.