Download 6.4 The Flow of Energy in Ecological Communities

Chapter 6 – Ecological Communities
6.1 Competition for Shared Resources
• Resources are limited
• Species within ecological community
compete for resources
– Ecological community
• Species that interact within a specific community
© 2013 Pearson Education, Inc.
6.1 Competition for Shared Resources
• Interspecific competition
– Two or more species compete for the same
resource
• Trees vs. shrubs for light and nutrients
• Competitive exclusion principle
– Two species that directly compete for
resources cannot coexist
© 2013 Pearson Education, Inc.
6.1 Competition for Shared Resources
• Ecological niche
– The role an organism fills within its habitat
• Fundamental niche
– Complete range of areas in which an
organism could exist
• Realized niche
– Range in which an organism actually exists
due to competition
© 2013 Pearson Education, Inc.
6.1 Competition for Shared Resources
• Ecological niche
– Niche differentiation
• Division of resources
• Potential competitors may coexist
– Example: Warblers in evergreen forests
© 2013 Pearson Education, Inc.
6.1 Competition for Shared Resources
• Mechanisms of competition
– Exploitation competition
• Consume resource faster
– Interference competition
• Stop competitor from consuming resource
© 2013 Pearson Education, Inc.
6.2 Herbivory, Predation, and Parasitism
• Herbivores
• Adapted to feed on plant material
– Specialized digestive systems
– Ability to detoxify plant chemicals
• Coevolution
– Tit for tat evolution of a prey and species that
consumes it
• Milkweed–monarch butterfly
© 2013 Pearson Education, Inc.
6.2 Herbivory, Predation, and Parasitism
• Predators
– Hunt, kill, and consume prey
– Many predators hunt various species
– Prey switching
• Predators focus on most abundant prey species
– Prey respond by adapting defenses
• Protection
• Camouflage
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
6.2 Herbivory, Predation, and Parasitism
• Parasites
– Depend on living host for nourishment
– Usually do not kill host
– Internal or external
• May be spread by vectors
– Organism that carry parasite but is not itself
affected
© 2013 Pearson Education, Inc.
6.2 Herbivory, Predation, and Parasitism
• Spread of parasite disease governed by 4
factors
– Abundance of hosts
– Accessibility of hosts
– Transmission rate of parasites
– Length of life of an infected host
© 2013 Pearson Education, Inc.
6.3 Mutualism and Commensalism
• Symbioses
– Intimate relationship between 2 species
• Mutualism
– Both species benefit
• Figs and wasps
© 2013 Pearson Education, Inc.
6.3 Mutualism and Commensalism
• Symbioses
– Commensalism
• One species benefit, other unaffected
– Snails and hermit crab
© 2013 Pearson Education, Inc.
6.4 The Flow of Energy in Ecological
Communities
• Energy must flow through ecological
communities
– Energy flow
• Transfer and transformation of energy
– Organisms classified by trophic level
• Based on food source
© 2013 Pearson Education, Inc.
6.4 The Flow of Energy in Ecological
Communities
• Food chains/food webs
– Depiction of feeding relationships among
organisms
• Primary producers/1st trophic level
– Transform energy from sun or chemicals
• Primary consumers/2nd trophic level
– Herbivores
© 2013 Pearson Education, Inc.
6.4 The Flow of Energy in Ecological
Communities
• Secondary consumers/3rd trophic level
– Carnivores
• Tertiary consumers/4th trophic level
– Top carnivores
• Decomposers
– Feed on nonliving organic matter
– Feces/dead organisms
© 2013 Pearson Education, Inc.
6.4 The Flow of Energy in Ecological
Communities
• Biomass energy
– Food that can be consumed by higher trophic
level
• Trophic level efficiency
– Much energy consumed used by organism
– Only ~10% available to next trophic level
© 2013 Pearson Education, Inc.
Food energy lost in
respiration and heat
+ O2
Food energy
lost as waste
© 2013 Pearson Education, Inc.
6.4 The Flow of Energy in Ecological
Communities
• Food webs
• Depicts all of the feeding relationships
– More detailed than food chains
• More complex food webs provide greater
stability
© 2013 Pearson Education, Inc.
6.4 The Flow of Energy in Ecological
Communities
• Keystone species
– Named after wedge-shaped keystone that
holds arched structures together
– Removal causes collapse
• Keystone species are important in stability
of many food webs
– Many plants, but some predators
– Trophic cascade
• Loss of carnivores results in explosion of
herbivores that destroy primary producers
© 2013 Pearson Education, Inc.
FOCUS ON SCIENCE: Trophic Cascades
Across Ecosystems
•
•
•
•
Scientists examined trophic cascades
Compared ponds with fish and without fish
Fish feed on dragonfly larvae
Adult dragonflies feed on pollinators
© 2013 Pearson Education, Inc.
6.5 Disturbance and Community Change
• Ecological disturbance
– Loss of many or all species in community
• Fires, hurricanes, volcanoes, logging
• Ecological legacies
– Resources remaining after disturbance
• Soil, debris
• Succession
• Pattern of change after disturbance
© 2013 Pearson Education, Inc.
6.5 Disturbance and Community Change
• Primary succession
– Virtually all resources removed
– Process can take millennia
• Typically bare rock
– Glacial retreat, volcanic eruption
• Pattern of primary succession
– Pioneer species
– Facilitation and migration of new species
– Climax community
© 2013 Pearson Education, Inc.
6.5 Disturbance and Community Change
• Secondary succession
– Follows disturbances that leave significant
legacy
• Soil, seed bank, wood debris
• Process much faster
– As quick as 70–100 years
• Old-field succession
– Abandoned farm fields
© 2013 Pearson Education, Inc.
6.5 Disturbance and Community Change
• Cyclic succession
– Succession may increase chances of
disturbance
– Buildup of understory leads to intense fire
• Some ecosystems are maintained by
cyclical succession
© 2013 Pearson Education, Inc.
6.5 Disturbance and Community Change
• Importance of place
– Surrounding areas affect successional
change
• Proximity to other systems
• Human influences
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.