Chapter 54 Community Ecology
Dec 19, 2015
Chapter 54Community Ecology
Community Ecology
• The study of the interactions between the species in an area.
Interspecific Interactions• Interaction between species.• May be positive, negative, or
neutral (in regards to fitness)• Ex:
Predation Mimicry Competition Symbiosis
Predation (+/-)
• Predator and prey relationships.
• Ex – Lynx and Hares
Herbivory (+/-)
• When an organism eats parts of a plant or algae.
• Herbivore – may have special adaptations to find their prey.
• Plants – may have adaptations to avoid being eaten.
Predation/Herbivory
• Often results in interesting defenses or adaptations.
• Ex:• Cryptic coloration• Aposematic coloration
Cryptic Coloration
• A passive defense where the prey is camouflaged against its environment.
Aposematic Coloration
• The use of conspicuous colors in toxic or unpalatable organisms to warn off predators.
poison arrow frogs
Mimicry
• Defense mechanism where the mimic has a resemblance to another species, the model.
• Types:• Batesian• Müllerian
Batesian Mimicry
• Palatable species mimics an unpalatable model.
Hawk moth larva Snake
Müllerian Mimicry
• Two unpalatable species resemble each other.
Cuckoo Bee Yellow Jacket
Competition
• When two species rely on the same limiting resource.
• Intraspecific competition usually more severe than Interspecific competition.
• Why?
Competitive Exclusion Principle
• Predicts that two species with the same exact requirement cannot co-exist in the same community.
• The better adapted species will survive and the less adapted will go extinct.
Think, Pair, Share
• Discuss if the Competitive Exclusion Principle explain the spacing of fast food restaurants on the “strip” in most towns.
Ecological Niche• The sum of a species’ use of
the biotic and abiotic resources in its environment is called the species’ ecological niche.
• How a species “makes its living” in its ecosystem.
• Species can not have niche overlap, the Competitive Exclusion Principle
Niche Types
1. Fundamental - what a species is theoretically capable of using.
2. Realized - what a species can actually use.
Think, Pair, Share
• Again in terms of fast food restaurants, explain the concept of a fundamental vs. realized niche.
Resource Partitioning
• A way that species avoid niche overlap by splitting up the available resources.
• Ex: Anolis lizards
A. distichus A. insolitus
Symbiosis
• When two different species live together in direct contact.
• Types:1. Parasitism
2. Commensalism
3. Mutualism
Parasitism (+/-)
• Parasite harms the host.• Parasites may be external or
internal.• Well adapted parasites don't kill
the host.
• https://www.youtube.com/watch?v=uvdiYg6ZN-U Sci-Show Parasites
Commensalism (+/o)
• One partner benefits while the other is unchanged.
• Ex. – Cattle and Egrets
Mutualism (+/+)
• Both partners benefit from the interaction.
• Ex: Pollinators and flowers
Acacia Tree and Ants
Species with large impacts
• Some species have larger impacts on a community structure than others.
• Ex:• Dominant Species• Keystone Species• Foundation Species
Dominant Species
• A species that is the most abundant or has the highest biomass in a community.
• Has a major effect on a community both biotically and abiotically.
Reason for Dominance?
• Best Competitor?
• Best in avoiding predators and disease?
• Invasive species may fit the last explanation.
Example
• Chestnuts – used to make up to 40% of the forest.
• Lost between 1910-1950 because of fungus disease.
• Major impact on wood and nut industries.
Response
• Some tree species increased in abundance to fill the gap.
• Mammals and birds did OK.
• 7 species of insects went extinct.
Keystone Species
• Not a dominant species, but has a major impact in the community structure.
• Often a top predator that controls the numbers of other species.
• Ex. Sea Otters
Foundation Species
• Species that cause physical changes in the environment that affect others.
• Ex. Beavers, Bison, Black Rush
• https://www.youtube.com/watch?v=ysa5OBhXz-Q
• How wolves change rivers
Succession
• Changes in species composition over time.
Succession Stages
• Climax Community - An ecological community in which populations of plants or animals remain stable and exist in balance with each other and their environment.
Succession Types
1. Primary
2. Secondary
Primary Succession
• Succession with only abiotic materials as the starting substrate
• Ex: volcanic islands glaciated areas road cuts
Secondary Succession
• Succession with biotic materials (living or dead) as the starting substrate
• Ex: • Cutting down a forest• Forest fire• Tornado/storm damage
Steps of Succession
• Pioneer Species – the first organisms to appear in the area in primary succession
• Usually moss or lichens
What do Pioneer Species Change?
• Enrich the soil – as generations die, their remains decompose and add nutrients to the soil (often N).
• The soil is now able to support a greater variety of species such as grasses and small shrubs.
• Which occurs faster, primary or secondary succession?
• What can you do to speed up succession?
Point
• If you understand the causes and controlling factors of succession, you can manipulate them.
Some points about Succession
• The Organisms are changing in the area over time. General pattern is an increase in biodiversity.
• The Climate of the area is NOT changing over time.
Other Changes
• Soil – becomes richer in N, more depth, better water retention etc.
• Light – can decrease at ground level because of shading by taller plants.
Summary
• Know the various types of interspecific interactions.
• Know the Competitive Exclusion Principle and Niche Concept.
• Know Species with large impacts.
Summary
• Know some examples and causes of succession.