Lecture 19: Community Ecology

Question 1

Interspecific Interactions

What is known as the total of an organism’s use of the biotic and abiotic resources in its environment?

Ex: Birches grow in cool, moist habitat.

Answer 1

Ecological niche

Question 2

Competition

Interspecific competition:
- When does it occur?
- (+/-,+/-)?

Answer 2

Interspecific competition:
- Occurs when: diff. species compete for particular resource that is short in supply = niches overlap!
- (-,-)

Question 3

Interspecific interactions

What is characterized as COMPETITIVE EXCLUSION?

In Interspecific competition

Answer 3

Local elimination of one of the two competing species

Ex: 2 bacterias in a jar. One outcompetes the other when “combined cultures”, one dies, one thrives!

Question 4

Interspecific Interactions

Resource partitioning: (-/-)
Individuals of a species can ____ what or when they ____ and where they ____ to ____ competition.
- Its a ____ change!
- ____ niche: range of conditions under which a species…

Answer 4

Individuals of a species can adjust what or when they eat where they live to minimize competition.
- Its behavioral change
- Realized niche: range of conditions under which a species ACTUALLY occurs in natural communities (caused by resource partitioning) - ex: eat sandwich instead of pizza…

Question 5

Interspecific Interactions

Character displacement:
- What causes competition?
- What cause the species to adapt?

Ex: Birds have diff beak depth cause eat diff. food even if really similar species.

Answer 5

• Causes competition: resource partitioning, hence to use DIFF. resources.
• Causes species to adapt: natural selection! = accumulation of adaptative traits!

Ex: Birds have diff beak depth cause eat diff. food even if really similar species.

Question 6

Interspecific Interactions

What is referred to as the INTERACTION where one species, the predator, kills and eats the other, the prey?
What system is it? (+/-,+/-)?

Answer 6

Predation (+/-)

Question 7

Predation

What are 2 predator strategies in predation?
1 - 2?

Answer 7

1. Camouflaged to avoid being noticed (leopord).
2. Attract their prey (flower).

Question 8

Predation

What are 5 prey strategies in predation?
1 - 2 - 3 - 4 - 5?

Answer 8

1. Flee/hide.
2. Live in groups.
3. Have mechanical defenses.
4. Have special coloration.
5. Use mimicry.

Question 9

Predation

Define the following terms:
1. Aposematic coloration
2. Cryptic coloration
3. Batesian mimicry
4. Mullerian Mimicry

Answer 9

1. Aposematic coloration: warning coloration/bright, predators avoid cause coloration signifies chemical defenses or toxicity. Ex: Butterfly.
2. Cryptic coloration: CAMOUFLAGE!
3. Batesian mimicry: A palatable/harmless species mimics an unpalatable/harmful one. Ex: Hoverfly resembles wasp…
4. Mullerian Mimicry: Two unpalatable species resemble each other (analogous/convergent evolution!) Ex: Bee and wasp.

Question 10

Interspecific Interactions

What is known as the process in which an herbivore eats parts of a plant?
- Led to what for the plant?
- (+/-,+/-)?

Answer 10

Herbivory! (+/-)
- Led to evolution of plant mechanical (spines, tough leaves) + chemical defenses.

Question 11

Interspecific Interactions

Wtf is paratism? (+/-,+/-)?
One organism, the ____ derives its ____ from another ____, its ____, which is ____ in the process.

Answer 11

In parasitism (+/-), one organism, the parasite derives its nourishment from another organism, its host, which is harmed in the process.

Question 12

Interspecific Interactions

What is defined as the interspecific interaction BENEFITING both species?

Answer 12

Mutualism (+/+)

Question 13

Interspecific Interactions

Tf is the process where one species benefits and the other is NOT affected?

Ex: Bird on buffalo’s back, bird eats parasites on its back and better for it, buffalo not affected.

Answer 13

Commensalism (0/+)

Question 14

Species in communities

What is:
- Dominant species?
- Keystone species?

+ Give one example for each!

Answer 14

• Dominant species: most abundant/have the most biomass or numbers! Can exert control over distribution/occurence of other species. Ex: ants.
• Keystone species: not most abundant, but very important ECOLOGICAL roles. Ex: castor.

Question 15

Food chains

What is known as the structure defined by the feeding relationships between organisms?

This includes primary producers eaten by primary consumers, etc.

Answer 15

THE TROPHIC STRUCTURE

Question 16

Community Level Processes

How tf would you describe food chains?
- The ____ of ____ ____ up to the ____ levels from its ____ through ____ consumers to ____ consumers.

Answer 16

• The transfer of food energy up to the trophic levels from its source through herbivores consumers to carnivores consumers.

Question 17

Community Level Processes

What is this: multiple food chains diagrammed with arrows linking species according to who eats whom?

Answer 17

Food webs!

Question 18

Community Level Processes

What is the bottom-up model?
- A ____ influence from ____ to ____ trophic levels.

Carnivores (en haut)
|
Herbivores
|
Autotrophs
|
Nutrient levels (en bas)

Answer 18

• A unidirectional influence from lower to higher trophic levels.

Question 19

Community Level Processes

What is the top-down control model?
- ____ controls ____ organization b/c ____ limit ____, ____ limit ____ and limit ____.

Answer 19

• Predation controls community organization b/c predators limit hervivores, herbivores limit plants and limit nutrients.

Question 20

Top-Down control

What is referred to as the increase in primary producers (plants/phytoplankton) due to impact on predators on herbivores?

Answer 20

Trophic cascade

Question 21

Species diversity

Define:
1. Species richness
2. Relative abundance

In next example, what is species richness and relative abundance? Community 1 has 100 individuals, 80 frogs, 5 salamanders, 5 snakes and 10 snails.

Answer 21

• Species richness: number of species present in community/ecosystems.
• Relative abundance: proportion that each species represents of all individuals in community.

Species richness: 4 species
Relative abundances: 80%, 5%, 5%, 10%.

Question 22

Species Diversity and Productivity

What is described here:
“Species with different morphological or physiological characteristics can use different resources thus increasing the overall productivity in species rich systems.”

Answer 22

The biodiversity-productivity in niche partitioning!

Question 23

Species Diversity and Stability

If biodiversity increases, what other 2 factors also INCREASE?
1 - 2?

Answer 23

1. Productivity: rate of generation of biomass.
2. Stability: temporal constancy of a community. (resilience after disturbance)

Question 24

Species Diversity and Stability

What is known as the INSURANCE HYPOTHESIS?
- A group may be more ____ to ____/____ ____ b/c diff. species exhibit diff. ____ +____ to change in environment!

Answer 24

INSURANCE HYPOTHESIS:
- A group may be more resilient to environmental/biological perturbances b/c diff. species exhibit diff. tolerances + responses to change in environment!

Question 25

Community Level Processes

What is known as an event (s.a. storm, fire, flood, human activity…) that changes a community by removing organisms from it/altering resource availibility?

Answer 25

DISTURBANCE

Question 26

Disturbance

State the different effects/consequences of these 3 types of disturbance:
1. Intermediate disturbance hypothesis
2. High-level disturbance
3. Low-level disturbance

Answer 26

1. Intermediate disturbance hypothesis: states that moderate levels of disturbance foster greater species diversity than do low or high levels of disturbance.
2. High-level disturbance: Too much environment stress. Species leave or can’t establish themselves.
3. Low-level disturbance: Competitively-dominant species have the time to outcompete and exclude less competitive ones.

Question 27

Ecological succession

Ecological succession:
- The ____ in species compostion in ____ areas over ____ time.
3 stages:
1. Begins in a LIFELESS area where no soil, s.a. volcanic island. Autotrophic prokaryotes present, mosses and lichens colonize + develop soil and grasses, shrubs and trees sprout = ???
2. Occurs where an existing community has been removed by disturbance s.a. fire, but soil is still intact. Herbaceous species grow first, trees after = ???
3. Climax community = ???

Answer 27

Ecological succession:
- The transition in species compostion in disturbed areas over ecological time.
3 stages:
1. Begins in a LIFELESS area where no soil, s.a. volcanic island. Autotrophic prokaryotes present, mosses and lichens colonize + develop soil and grasses, shrubs and trees sprout = Primary succession
2. Occurs where an existing community has been removed by disturbance s.a. fire, but soil is still intact. Herbaceous species grow first, trees after = Secondary succession
3. Climax community = Stable final stage

Population is now reconstituted!