Communities: How Do Species Interact?

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Communities How Do Species Interact?

• Chapter 26

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Overview

• Community Interactions
• Abiotic Factors
• Predator/Prey Relationships
• Defense Mechanisms
• Symbiotic Relationships
• Competition
• Succession

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Communities

• Charles Darwin- The flowering of clover in the
  English countryside depended on the local
  residents affection for cats
• The First Law of Ecology
• every species ultimately affects every other
  species
• As iron sharpens iron, so one man sharpens
  another- Proverbs 2717

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What Determines the Types of Organisms Found in
Communities?

• Abiotic Factors

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Predator/Prey Interactions
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The Consumer and the Consumed

• Predators- usually kills its prey and consumes
  most of its body
• Parasites- consumes only part of the blood or
  tissues and does not necessarily kill the host
• Herbivores?

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Predators

• Usually larger than prey
• Examples?
• Counterexamples?
• General Characteristics?
• swiftness
• intelligence
• acute senses
• sharp teeth

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Parasite Characteristics

• Generally Smaller than Hosts
• Often attack hosts in large numbers

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The Consumed Defenseless?

• Camouflage
• Examples?
• Chemical Defense
• plant secondary metabolites
• animal defense chemicals examples?
• Warning Coloration

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Warning Coloration

• If a skunk looked like a rabbit, it would be
  attacked over and over again, in spite of its
  potent defense.- adaptive?
• Generally involves vivid shades of red, yellow,
  orange, and white combined with a contrasting
  shade of blue or black
• Mimicry- evolution in action?
• Batesian (painted mealworms)
• Mullerian (Monarch and Viceroy)

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Symbiosis
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What is Symbiosis?

• Parasitism Example?
• Mutualism Example?
• Commensalism Example?

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Coevolution

• Adaptive evolution that appears to result from a
  long and mutual evolutionary history in which the
  needs of each species exert selective pressure on
  the other
• Biologists love to suggest likely examples of
  coevolution.
• Examples?

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Competition
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Competition Defined?

• Hypothetical Examples?
• Competition in the Lab
• Paramecium caudatum and Paramecium aurelia

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• Competitive Exclusion Principle
• if two species compete directly for exactly the
  same limiting resource, the more efficient
  species will eliminate the other
• Which species will win?

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Competitive Exclusion

• Habitat and Niche?
• Does Competitive Exclusion Occur in Natural
  Communities?

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Does Competitive Exclusion Occur in Natural
Populations?

• Barnacles
• Balanus balanoides (lowest intertidal rocks)
• Chthamalu stellatus (higher rocks)
• Remove each- what do you expect if competition
  were occurring?
• Fundamental Niche
• Realized Niche

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Ecosystems and Species Richness/Diversity

• Species Richness
• Species Diversity
• General Trends in Species Diversity (Abiotic)
• increases from the poles to equator
• increases from high to low elevations
• increases as physical variation increases
• increases with size of ecosystem
• no direct correlation between productivity and
  diversity

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Species Diversity What Determines it?

• Island species diversity depends on immigration
  of new species and extinction of old species
• Theory of Island Biogeography (Robert MacArthur
  and Edward O. Wilson)
• Exterminated all arthropods on small islands near
  Florida keys (Table 26-2)

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Succession

• The change in the numbers and kinds of organisms
  in a community over time
• primary
• secondary
• Pioneer Community
• Successional Community
• Climax Community

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Pioneer vs. Climax Communities

• Pioneer
• quick breeding species
• species that flourish in disturbed areas

• Climax
• slow breeding
• gradually take over undisturbed areas

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Succession in Animals

• Short-lived communities
• rotting deer
• dung
• rotting tree

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Succession and Forensics

• Forensics and Entomology

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Why Does Succession Occur?

• Early Communities may
• facilitate succession
• tolerate succession
• inhibit succession (birch and aspen no spruce)
• In primary successions, pioneering communities
  always facilitate succession
• Secondary succession

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What Determines the Characteristics of the Climax
Community?

• Abiotic Factors
• Specific History of Area