Community and Ecosystem Ecology

1
Community and Ecosystem Ecology

• Chapter 20

2
Community Ecology

• Species living in same vicinity
• Potential interactions will occur
• Interspecific interactions
• Interactions between species
• Classified according to effect on populations
• Helpful ()
• Harmful (-)

3
Community Interactions

• Occurs in a few ways
• Competition
• Mutualism
• Predation
• Herbivory
• Parasites and pathogens

4
1. Competition (-/-)

• Occurs when members of two different species try
  to utilize the same resource
• Competitive Exclusion Principle
• No two species can occupy the same ecological
  niche at the same time

5
Competition Between Two Species of Barnacles
6
Competition

• Competition can lead to resource partitioning
• decreases competition between the two species
• Character displacement is often viewed as
  evidence that competition and resource
  partitioning have taken place

7
2. Mutualism (/)

• Both members of the association benefit

8
3. Predation (/-)

• Predator
• Prey
• 2 ways this regulates population growth
• A. Predator-Prey Population Dynamics
• B. Antipredator Defenses

9
3. Predation

• A. Predator-Prey Population Dynamics
• Cycling of predator and prey populations
• Occurs when either predators overkill prey, or
  when prey overuse resources and their numbers
  crash
• In either case, predator numbers also decrease
  from a decrease in food source

10
Predatory-Prey Cycling of a Lynx and a Snowshoe
Hare
11
Coevolution

• Evolutionary change in one species results in an
  evolutionary change in the other
• Organisms in symbiotic associations are
  especially prone to the process of coevolution
• Also occurs between predators and prey
• Example Cheetah sprints forward to catch prey,
  and this behavior might be selective for those
  gazelles that jump high in the air

12
3. Predation

• B. Antipredator Defenses
• Cryptic coloration
• Camouflage
• Warning coloration
• Association with undesirable consequences

13
3. Predation

• B. Antipredator Defenses
• Mimicry
• One species resembles another species
• Can help capture food or avoid being preyed upon
• Batesian Mimicry
• A prey that is not harmful mimics another
  species that has a successful antipredator
  defense
• Warning colorations
• Mullerian mimicry
• Species that resemble each other all have
  successful defenses

14
Mimicry Among Insects
Mullerian
Batesian
15
Coral snake vs. Milk snake
http//www.youtube.com/watch?vLU8DDYz68kM
16
4. Herbivory (/-)

• Consumption of plants by an animal
• Plant must expend energy to regenerate
• Evolved defenses

17
5. Parasites Pathogens (/-)

• Parasite
• Lives on or in a host
• Endoparasite
• Ectoparasite
• Pathogens
• Disease-causing microorganisms

18
Trophic Structures

• Feeding relationships among species in a
  community
• Determines the passage of energy and nutrients
• Sequence of food transfer is a food chain
• Unbranched

19
Trophic Structure

• Autotrophs (producers)
• Require an energy source and inorganic nutrients
  to produce organic food molecules
• Manufacture organic nutrients for all organisms
• Green plants and algae carry on photosynthesis

20
Trophic Structure

• Heterotrophs (consumers)
• Need a preformed source of organic nutrients
• Herbivores
• Graze directly on plants or algae
• Carnivores
• Feed on other animals
• Omnivores
• Feed on both plants and animals

21
Trophic Structure

• Decomposers
• Heterotrophic bacteria and fungi
• Break down nonliving organic matter
• They release inorganic matter to be used by
  producers
• Scavengers
• Feed on dead remains

22
Ecosystem Ecology

• Possesses both abiotic and biotic components
• Biotic
• The various populations of organisms that form a
  community
• Abiotic
• Includes resources such as sunlight, inorganic
  nutrients, soil, water, temperature and wind
• Two major processes sustain all ecosystems
• Energy flow
• passage of energy through the components of the
  ecosystem
• Chemical cycling
• use and reuse of chemical elements within the
  ecosystem

23
Energy flow
Chemical energy
Light energy
Heat energy
Chemical elements
Bacteria, protists, and fungi
24
Energy Flow

• Biomass
• Mass of living organic material in ecosystem
• Ecological Pyramids
• only about 10 of the energy of one trophic level
  is available to the next trophic level
• Producers at the base
• Most available energy
• Energy is given off in less usable forms as
  producers are eaten by primary consumers, etc.

25
Chemical Cycling

• Biogeochemical cycles
• Biotic and abiotic components of the chemical
  cycles in an ecosystem
• 3 main cycles
• Carbon cycle
• Phosphorus cycle
• Nitrogen cycle

26
CO2 in atmosphere
Burning
Photosynthesis
Cellular respiration
Higher-level consumers
Plants, algae, cyanobacteria
Primary consumers
Wood and fossil fuels
Decomposition
Wastes death
Plant litter death
Decomposers (soil microbes)
Detritus
Figure 20.32