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Chapter 26: Community Ecology (Predator-Prey Interactions (Apparent…
Chapter 26: Community Ecology
Diversity
Diversity and Latitude
Scale
Larger areas are more diverse than smaller ones
Species-Area Relationship
The relationship between area and species richness
Expressed by the formula
S = cA^z
Checklist
A first approach by quantifying community diversity is done by measuring species richness, which is simply a count of the species present
Community
Population biology focuses on the members of a single species
Interbreeding
Survival
Their growth
Because the members of community occur at the same time and place
A community must have boundaries in both
Time
Space
Is a group of species that occur together at the same time and place
Succession
The process by which the structure of a biological community evolves over time.
2 Types
Primary Succession
Regions in which the soil is incapable of sustaining life
Newly formed sand dunes
,Or rocks left from a retreating glacier
As a result of lava flows
Secondary Succession
Occurs in areas where a community that previously existed has been removed
Climax Community
Is the final stage of succession, remaining relatively unchanged until destroyed by an event such as fire or human interference.
Community Restoration
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Such as reintroducing wolves into Yellowstone National Park
And encouraging the migration of bears and mountain lions across the Rio Grande River from Mexico into Big Bend National Park in Texas
Habitat Loss and Habitat Fragmentation
Habitat Loss: Is the process by which natural habitat becomes incapable of supporting its native species.
Habitat Fragmentation: Is a process by which large and contiguous habitats get divided into smaller, isolated patches of habitats.
Predator-Prey Interactions
Competition Between Species
Interference Competition
One organism restricts another organism's access to resource even though the first might not be using it
Exploitation Competition
Thus making it less available for other organisms
Resource competition occurs when the organisms actually consume a shared resource
Apparent Competition
Plants often face the problem that many herbivores will eat a variety of plants
If all prey populations are low, then the population of the predator is probably low also
Because the plants are not actually competing for and using a resource, this is called apparent competition
Predator Selection Among Multiple Prey
Optimal Diet Model
Optimal Foraging Theory
Examine the interactions between these theories in an attempt to understand why herbivores eat the plants they do while ignoring others
Communities have multiple plant species that are prey to herbivorous predators
One Predator, One Prey
2 Fundamental Aspects
Handling time
Refers to the amount of time needed to actually consume the prey
These 2 together constitute the predators
Functional Response
Predator's feeding rate
Feeding rate refers to how quickly a predator find a new prey individual
Prey-Dependent
Feeding rate will be faster if there are more prey individuals available, so the predator's functional response is dependent on prey density
One species of prey, such as a plant (a primary producer), is attacked by only one species of predator, such as an herbivore
(a primary consumer)
Within natural communities, any plant is attacked by multiple predators, and almost every herbivore attacks several species of plants
Zero Growth Isocline
The curved zero growth isocline has unexpected consequences
The line indicating population stability is called zero growth isocline
Illustrates the effect of prey density on predator populations
Paradox of Enrichment
Ex) Eutrophication
In which mineral-rich pollution fertilizes streams and lakes,
causing certain algae to proliferate but untimately resulting in loss of many species
Improving conditions for the prey may lead the predator to overexploit the prey and both species will be lost - this is called the paradox of enrichment
Maximum Sustained Yeild
Theoretically, if we would harvest just enough of species would be stable and we would obtain
The biggest yield that can be taken from a organism's stock over an certain period of time.
Beneficial Interactions Between Species
Nurse Plants
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Seeds that germinate beneath the nurse plant are more likely to survive
These are plants that alter a small area of habitat immediately below themselves
Such that it is more favorable to the survival of seedlings of other plants as compared to other nearby areas not below the nursing plant
Primary Succession
In which organisms become established on newly created substrates
Ex) Volcanoes produce new substrate in the form of lava flows or ash fields that are completely sterile as they cool
Facilitation plays a role in succession, especially primary succession
Facilitation
That is a facilitation, the first organism facilitates the presence of the other
Ex) Beavers building a dam and creating ponds
The ponds are of great benefit to many plants and animals, but none of those really help the beavers
If one organism helps another without receiving any benefit
Mutualistism and Mutualistic Relationships
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Both organisms benefit
Ex) Pollinators and the plants they pollinate
Organisms within a community often interact in ways that are beneficial
