community ecology
DESCRIPTION
Community Ecology. Communities. A community is a group of organisms of different species that live in a particular area. Individualistic Hypothesis vs. Interactive Hypothesis. Individualistic Hypothesis: - PowerPoint PPT PresentationTRANSCRIPT
Community Ecology
Communities
A community is a group of organisms of different species that live in a particular area
Individualistic Hypothesis vs. Interactive Hypothesis Individualistic Hypothesis:
A community is a chance group of species found in the same area because they have similar abiotic requirements
Interactive Hypothesis: A community is a group of closely linked
species locked together in mandatory biotic interactions that cause the community to function as an integrated unit
Interspecific Interactions
Interspecific interactions are interactions that occur between populations of different species living together in a community
There are 4 major interspecific interactions: Predation (and parasitism) Competition Commensalism Mutualism
Predation (and Parasitism)
(+ -) The interaction is
beneficial to one species and detrimental to the other
Predation: When a predator
eats its prey Example in
picture:
Predation (and Parasitism)
Parasitism: Predators that live
on or in their hosts, usually feeding off their body tissues or fluids
• Usually do not kill their hosts
Examples:
Plant Defenses Against Herbivores
“Plants Fight Back!” Plants have 2
major mechanisms by which they defend themselves against being eaten Mechanical
Defenses• Thorns, hooks,
etc.
Plant Defenses Against Herbivores Chemical Defenses
Produce chemicals that are distasteful or harmful to an herbivore
Morphine (opium poppy)
Nicotine (tobacco)
Animal Defenses Against Predators
Animals defend themselves against predators passively (hiding) or actively (fleeing)
Cryptic coloration (camouflage) makes prey difficult to spot
Aposematic coloration (warning coloration)warns predators not to each animals that may be toxic or may sting.
Animal Defenses Against Predation Mimicry
When one species “imitates” or “mimics” another Batesian mimicry
• When one edible or harmless species mimics an bad-tasting (unpalatable) or harmful species
• Example: hawkmoth mimics a snake
Animal Defenses Against Predation
Mimicry Mullerian mimicry
• Two species, both of which are unpalatable (taste bad) or harmful, resemble each other
• Example: monarch butterfly (unpalatable) and queen butterfly (unpalatable) resemble each other
Symbiosis- close relationship between two organisms.
Parasitism (+,-) Commensalism (+,neutral) Mutualism (+,+)
Parasitism
One organism (the parasite) gets its nourishment from another organism (the host), which is harmed in the process
Endoparasites: Live within host
tissues (tapeworms) Ectoparasites:
Feed on external surfaces (mosquitoes)
Interspecific Competition
Competition between organisms of different species
The Competitive Exclusion Principle:Two species with similar needs for the
same limiting resources cannot coexist in the same place
Niches may overlap but they may not be identical.
Ecological Niches An organism’s niche is the
specific role it plays in its environment All of its uses of biotic and
abiotic resources in its environment
Example: oak tree in a deciduous forest
• Provides oxygen to plants, animals, etc.
• Home for squirrels• Nesting ground for blue jays• Takes water out of the soil• Etc., etc.
Fundamental v. Realized Niche
Fundamental Niche includes resources an organism could theoretically use (if no competition)
Realized Niche includes resources it actually does use given competition from other species.
Resource Partitioning
Similar species develop ways to partition/divide resources in order to coexist.
Commensalism
(+0) relationship One partner benefits, the
other is not affected Examples:
Cattle and cattle egret (birds)
Sea anemone and clownfish
• Clownfish gets a place to live, sea anemone is not affected
Mutualism(++) relationshipBoth partners benefit from the
relationship“You scratch my back, I’ll
scratch yours”Examples:
Ants & acacia treetree provides high
protein food in beltian bodies & habitat for nests inside thorns; ant protects against predators
Mycorrhizae-fungal extentions on plant roots
Plant gets increased water/nutrition, fungi gets food
Hummingbirds & flowersHummingbirds get food,
flowers can reproduce
Dominant & Keystone Species Dominant Species:
Species in a community that have the highest abundance or highest biomass
Sugar maple in eastern North America Keystone Species:
Important to a community because of their ecological roles (niches), not by numbers
Sea otters control sea urchin population, which controls kelp population
Sea stars are keystone predators in many aquatic environments.
Ecological Succession
Ecological succession is a change in the species that live in a given area over a period of time One community replaces another
Primary succession = occurs in places where soil is not yet formed (bare bedrock)
Secondary succession = occurs in places where there is soil, but where some disturbance has eliminated the previous community
Ecological Succession
Ecological Succession
The first organisms to inhabit an area undergoing succession are known as pioneer organisms These are usually small organisms (bacteria,
lichens, algae, etc.) The ecosystem goes through a number of
stages, with each new stage usually consisting of larger organisms than the last one
Once a community has become stable and is not changing much, it is known as a climax community
Causes of Ecological Succession
There are 3 major causes of ecological succession:1. Human Activities
- logging, mining, development, etc.2. Natural Disasters/Disturbances
- fires, volcanic eruptions, etc.3. Natural Competition Among Species
- Fictitious example:- turtles and frogs both eat crickets- frogs are faster, turtles are slower- frogs eat more crickets, turtles starve- turtle population dies out, frog
population gets bigger