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Biodiversity, Species Interactions, and Population Control

Chapter 5

Core Case Study: Southern Sea Otters:

Are They Back from the Brink of

Extinction?

• Habitat
• Hunted: early 1900s
• Partial recovery
• Why care about sea otters?
  • Ethics
  • Keystone species
  • Tourism dollars

Species Interact in Five Major Ways

• Interspecific Competition
• Predation
• Parasitism
• Mutualism
• Commensalism

Most Species Compete with One

Another for Certain Resources

• Competition
• Competitive exclusion principle

Most Consumer Species Feed on Live

Organisms of Other Species (2)

• Prey may avoid capture by
  • Camouflage
  • Chemical warfare
  • Warning coloration
  • Mimicry
  • Deceptive looks
  • Deceptive behavior

Science Focus: Why Should We Care

about Kelp Forests?

• Kelp forests: biologically diverse marine habitat
• Major threats to kelp forests
  • Sea urchins
  • Pollution from water run-off
  • Global warming

Some Species Feed off Other Species

by Living on or in Them

• Parasitism
• Parasite-host interaction may lead to coevolution

In Some Interactions, Both Species

Benefit

• Mutualism
• Nutrition and protection relationship
• Gut inhabitant mutualism

5-2 How Can Natural Selection Reduce

Competition between Species?

• Concept 5-2 Some species develop adaptations that allow them to reduce or avoid competition with other species for resources.

Some Species Evolve Ways to Share

Resources

• Resource partitioning
• Reduce niche overlap
• Use shared resources at different
  • Times
  • Places
  • Ways

5-3 What Limits the Growth of

Populations?

• Concept 5-3 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

Populations Have Certain

Characteristics (1)

• Populations differ in
  • Distribution
  • Numbers
  • Age structure
• Population dynamics

Most Populations Live Together in

Clumps or Patches (1)

• Population distribution - Clumping - Uniform dispersion - Random dispersion

Most Populations Live Together in

Clumps or Patches (2)

• Why clumping?
  • Species tend to cluster where resources are available
  • Groups have a better chance of finding clumped resources
  • Protects some animals from predators
  • Packs allow some to get prey
  • Temporary groups for mating and caring for young