Chapter 26: Community Ecology

Diversity

Predator-Prey Interactions

Beneficial Interactions Between Species

Diversity and Latitude

click to edit

Community

Population biology focuses on the members of a single species

Because the members of community occur at the same time and place

Is a group of species that occur together at the same time and place

Interbreeding

Survival

Their growth

A community must have boundaries in both

Time

Space

Botany Community Pic 2

Botany Community Pic 3

Botany Community Pic 1

Botany Community Pic 4

Succession

The process by which the structure of a biological community evolves over time.

2 Types

Primary Succession

Secondary Succession

Regions in which the soil is incapable of sustaining life

Occurs in areas where a community that previously existed has been removed

Newly formed sand dunes

,Or rocks left from a retreating glacier

As a result of lava flows

Botany Primary Succession Pic

Botany Primary Succesion Pic 2

Botany Secondary Succession Pic 2

Botany Secondary Succession Pic 3

Botany Secondary Succession Pic 1

Climax Community

Community Restoration #

Is the final stage of succession, remaining relatively unchanged until destroyed by an event such as fire or human interference.

Botany Climax Community Pic 3

Botany Climax Community Pic 2

Botany Climax Community Pic 1

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

Botany Community Restoration Pic 1

Botany Community Restoration Pic 3

Botany Community Restoration Pic 2

Habitat Loss and Habitat Fragmentation

Habitat Loss: Is the process by which natural habitat becomes incapable of supporting its native species.

Botany Habitat Fragmentation Pic 3

Habitat Fragmentation: Is a process by which large and contiguous habitats get divided into smaller, isolated patches of habitats.

Botany Habitat Loss Pic 2

Botany Habitat Loss Pic 1

Botany Habitat Fragmentation Pic 2

Botany Habitat Fragmentation Pic 1

Botany Habitat Fragmentation Pic 4

Botany Habitat Fragmentation Pic 5

Scale

Species-Area Relationship

Checklist

A first approach by quantifying community diversity is done by measuring species richness, which is simply a count of the species present

Larger areas are more diverse than smaller ones

The relationship between area and species richness

Expressed by the formula

S = cA^z

Botany Diversity Pic 1

Botany Diversity Pic 2

Botany Diversity Pic 3

Botany Species Area Relationship Pic

Botany Latitude Pic 5

Botany Latitude Pic 4

Botany Latitude Pic 3

Botany Latitude Pic 6

Competition Between Species

Apparent Competition

Predator Selection Among Multiple Prey

One Predator, One Prey

2 Fundamental Aspects

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)

Botany Predator Prey Pic

Botany Predator Prey Pic 2

Within natural communities, any plant is attacked by multiple predators, and almost every herbivore attacks several species of plants

Handling time

These 2 together constitute the predators

Predator's feeding rate

Feeding rate refers to how quickly a predator find a new prey individual

Refers to the amount of time needed to actually consume the prey

Functional Response

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

Botany Functional Response Pic 2

Botany Functional Response Pic 1

Botany Handling Time Pic 2

Botany Handling Time Pic

Botany Prey Dependent Pic 1

Botany Predator Dependent Pic 1

Botany Predator Prey Pic 4

Botany Predator Prey Pic 3

Botany Predator Prey Pic 5

Zero Growth Isocline

The curved zero growth isocline has unexpected consequences

The line indicating population stability is called zero growth isocline

Botany Zero Growth Isocline Pic 1

Botany Zero Growth Isocline Pic 2

Illustrates the effect of prey density on predator populations

Botany Zero Growth Isocline Pic 3

Botany Zero Growth Isocline Pic 4

Paradox of Enrichment

Ex) Eutrophication

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

In which mineral-rich pollution fertilizes streams and lakes,

Botany Eutrophication Pic 1

causing certain algae to proliferate but untimately resulting in loss of many species

Botany Eutrophication Pic 2

Botany Paradox of Enrichment Pic 2

Botany Paradox of Enrichment Pic 1

Maximum Sustained Yeild

Theoretically, if we would harvest just enough of species would be stable and we would obtain

Botany Maximum Sustained Yield Pic

The biggest yield that can be taken from a organism's stock over an certain period of time.

Botany Maximum Sustained Yield Pic 2

Optimal Diet Model

Optimal Foraging Theory

Communities have multiple plant species that are prey to herbivorous predators

Botany Optimal Diet Model Pic 1

Examine the interactions between these theories in an attempt to understand why herbivores eat the plants they do while ignoring others

Botany Optimal Foraging Theory Pic 1

Botany Optimal Foraging Theory Pic 2

Interference Competition

Exploitation Competition

Thus making it less available for other organisms

Botany Exploitation Competition Pic 1

Resource competition occurs when the organisms actually consume a shared resource

Botany Exploitation Competition Pic 2

Botany Interference Competition Pic 1

Botany Interference Competition Pic 2

One organism restricts another organism's access to resource even though the first might not be using it

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

Botany Apparent Competition Pic 2

Botany Apparent Competition Pic 1

Nurse Plants #

Primary Succession

Facilitation

Mutualistism and Mutualistic Relationships #

Both organisms benefit

Ex) Pollinators and the plants they pollinate

Organisms within a community often interact in ways that are beneficial

That is a facilitation, the first organism facilitates the presence of the other

Ex) Beavers building a dam and creating ponds

If one organism helps another without receiving any benefit

Seeds that germinate beneath the nurse plant are more likely to survive

Botany Nurse Plant Pic 1

These are plants that alter a small area of habitat immediately below themselves

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

Botany Primary Succession Pic

Botany Primary Succession Pic 2

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

Botany Nurse Plant Pic 2

Botany Mutualism Pic

Botany Mutualism Pic 3

Botany Mutualism Pic 2

The ponds are of great benefit to many plants and animals, but none of those really help the beavers

Botany Facilitation Pic 1

Botany Facilitation Pic 2