APES CHAPTER 8 NOTES - Shirleytempledolls



APES CHAPTER 8 NOTES

Community Ecology: Structure, Species Interactions, Succession and Stability

Case Study: Flying Foxes Keystone Species

a) Durian is a prized fruit growing in Southeast Asian tropical forest.

b) Strong odor- not allowed to transport publically.

c) Pollination of the tree depends on the bats called Flying Foxes. (mutualism)

d) Flying Fox is endangered- habit destruction- deforestation hunting- meat sold in China.

e) Keystone Species- (important to the ecosystem because)

1. Plant species they pollinate.

2. Plant seeds they dispose in the droppings.

3. Many other species depend on them.

f) Economically important because:

1. Durian fruit

2. Medicine

3. Timber- fuel

4. Fibers

5. Dyes

g) Study illustrates:

1. Vague Role (niche) of each species in a community

2. How interactions between species can affect ecosystem structure and function.

I. Role of Species in an Ecosystem- Niche

a) Community Structure: Ecologists usually describe the structure of a community of ecosystem in terms of four characteristics.

1. Physical appearance- size and distribution of population.

2. Species Diversity- number of different species.

3. Species Abundance- number of each individual species.

4. Niche structure- species interactions.

b) Where is most of the worlds Biodiversity Found

1. Tropical Rain Forest

2. Coral Reefs

3. Deep Sea

4. Large tropical lakes

II. General types of Species:

1. Native Species- Indigenous species- species that normally like and thrive in an ecosystem.

a. Raccoon, sea oats

2. Non-native species- Exotics, aliens- species that have been introduced into an ecosystem by humans- some are beneficial most are not because there is no natural control.

a. Ex. Water Hyacinths, Fire ants, Asian clams, zebra mussel’s melaluca, cudzoo and African Bees.

Brazil

1957- imported African bees- increased honey production.

African bees have displaced regular honey- bees and lowered honey production.

- Moved northward to Central America into US Texas, Arizona.

3. Indicator Species- species that serve as early warnings that a community or ecosystem is being damaged.

a. ex. Songbirds, benthic invertebrates, trout, amphibians.

4. Keystone Species- a species that is much more important to ecosystem than the biomass would suggest.

a. Bats, dung beetles, sea otters, gopher tortoise, elephants, rhinos, beavers, flying fox- fruits.

III. Species Interactions

a) Interspecific Competition:

1. Competition among species- when they compete for food, space, or any other unlimited resource.

2. As long as resources are plenty- not much competition.

3. When fundamental niches overlap one species will succeed the other species will need to move or will die out.

b. Interference competition- one species limits another’s access to some resource. – Territories- humming bird defends a patch of flowers.

c. Exploitation competition- both species have access to resources, but differ in how fast or efficiently they use the resource- humans.

d. Competitive Exclusion- once species eliminates the other due to use of limited resources.

Ex. Fire ant- reduced 90% of native ant species.

4. Ways to reduce competition.

a. Resource partitioning

Use resources at different times, different ways or in different places. Negative feedback loops allow them to share the wealth.

Ex. Hawks/ Owls. Warblers- different areas of tree.

b. Character displacement

Use physical or behavioral characteristics to use different resources.

On evolutionary time scale. Ex. Birds on Darwin’s islands.

b) Predation

1. One species feeds directly on all or part of another organism.

2. Predator- prey relationships- positive feedback relationship for predator- until low number of prey cause negative feedback loop.

3. Sometimes helps the prey population by killing the sick, weak or aged members.

4. Predatory- not always the bad guy- cultural impact.

5. Tactics of Predator.

a. Speed

b. Armor

c. Great senses

d. Thorns

e. Camouflage

f. Defensive chemical warfare

g. Warning coloration

h. Mimicry

i. Bluff

j. Schools, flocks, herds.

IV. Symbiosis

1. Living together- long lasting relationship

2. Kinds of symbiosis

a. Parasitism- one species gets nourishment from another species.

- Parasite is smaller, long time relationship, rarely kills host, make host weaker over a long period of time.

- Two types of parasites.

1. Endoparasite- live inside ex. Tapeworm.

2. Exoparasite- live outside ex. Mosquito.

a. Mutualism- interaction where both species benefit

win- win

Ex. Lichens algae. Fungi. Pollen/ Bees. Rhizobiums- a bacteria in the root nodules of legumes that trap Nitrogen in THE SOIL. Termites/ Protozoan. Ants/ acacia trees. Mychorrizae

- Increases when resources get scarce.

C. Commensalisms- interaction where one is benefited and the other is unaffected.

Epiphytes- orchids.

V. Ecosystem Structure and Ecological Succession

a. Communities are in a constant state of change due to changes in vegetation in response to changes in climate.

1. The slow process of change is called Ecological succession.

2. Changes form an unstable (serial community to a stable balanced community called a Climax community. (Mature community)

3. Succession not always predictable.

4. Some communities never reach climax because of reoccurring disasters or due to limiting factors.

5. Two types of succession

a. Primary Succession

- Starts from lifeless area- glacier, volcano

- Must build a soil first

- Soil building is started by pioneer species (lichens, mosses)

- Continued by early successional plant species – nature’s sprinters- ground cover, reproduce fast survive harshness.

- Missuccessional plants- (100’s years) grasses/ shrubs

- Late successional plants- trees

- Rate- faster in humid tropical areas slowest in dry polar

- Also occurs in aquatic ecosystems.

b. Secondary Succession

- Begins in an area where the natural vegetation has been disturbed.

- Ex. Farmlands, burned forest, polluted streams, floods

- Each stage brings its own species diversity, trophic structure, niches, nutrient cycling, energy flow and efficiency.

- Pattern of succession in SW USA is Grasses, shrubs, pines, oaks, magnolias.

5. 3 Factors that affect how and at what rate succession occurs

1. Facilitation- one species makes it possible for another species.

2. Inhibition- one species makes it impossible of difficult for another species. Through competition (interference and exploitation).

3. Tolerance- successional stages occur at the same time esp. in late successional stages. Ex. A Birch tree growing among other trees in a Forest.

6. Disturbance guides succession- caused naturally and by humans Unfavorable changes

a. Not all changes unfavorable- fire maintained ecosystems.

b. Intermediate disturbance hypothesis

- Communities that experience fairly frequent moderate disturbances have the greatest diversity. Allows species of both early stages in openings and late stages.

VI. Biodiversity and Ecosystem Stability

a) Stability- ability of living system to withstand externally imposed changes.

1. Three aspects of stability.

a. Inertia/ Persistence- ability to resist disturbance

- Found in rain forest

b. Constancy- maintains a certain size, keep within limits.

c. Resilience- ability to bounce back

- Found in grasslands (fire adapted)

2. Signs of a stressed ecosystem

a. Drop in primary production

b. Increased nutrient loss

c. Decline of indicator species

d. Larger pop of pest or disease organisms

e. Decline in species diversity

f. Contaminants

3. Precautionary Principal: When evidence indicates that an activity can harm human health or the environment. We should take measures to prevent harm. “Better safe then sorry.”

4. Map page 186-187

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