Download Ch. 13 and 14 - ltcconline.net

Ecology
Fall Quarter
Lake Tahoe Community College
Instructor: Sue Kloss
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Chapter 13, 14
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Competition
Intro - A.G. Tansley did a classic experiment in competition. He grew two different species of the same genus (Gallium bedstraw) together on different soils. He found that each species outcompeted the other on soils where it is naturally found,
even though each alone was capable of growth on both soils. Competition, either among members of the same or different
species, may have broad effects on plant community structure.
The more crowded a population, the more resource limitation there is, the more intense the competition for resources.
I. Consumers compete for resources
A. Competition - any use/defense of resource by an individ that reduces availability of resource for other individs.
1. Competition is one way that activities of individuals affects the well-being of others.
a. interspecific
b. intraspecific
2. Competition within species
3. competition btn different
4. superior competitors can persist at lower resource levels;
5. Competition occurs in plants as well
a. David Tilman
b. as a stand of trees develops, the biomass of the forest increases and the numbers decline.
B. Competition may occur through exploitation or interference
1. resource or exploitation competition
2. interference competition
C. resource
1. resources are consumed, and amount can be reduced
2. consumer uses a resource for its own maintenance and growth
3. when resource availability is reduced, biological processes are affected in such a way as to
reduce population growth
D. Renewable and nonrenewable resources
1. nonrenewable resources 2. renewable
E. limiting resources
1. Liebig’s law of the minimum
2. Most times, there are more complex interactions
F. Competitive exclusion principle - Gauss
1. competitive exclusion is expressed when consumption depresses resource limiting population growth.
2. similar species do coexist in nature
a. fundamental vs realized niche
Lesson Objectives for Competition
1. Describe Tansley’s experiments on competition and the conclusions he formed about how competition affects
community structure.
2. Define competition generally, and then define the 2 general forms of competition that exist (inter and intraspecific), and
provide examples of each.
3. Describe Tilman’s experiment on plant density and the conclusions he drew from his experiments.
4. Describe Toumey and Kienholz’ research experiment that investigated how roots of forest trees compete with and limit
understory plant growth.
5. Choose 2 competing species of plants or animals that you are familiar with. Explain how one species can eliminate
another if it is a better competitor.
6. Define resource and provide some examples.
7. Describe Liebig’s Law of the Minimum. Explain the more modern interpretation of resource limitation. Provide examples.
8. Define Gauss’s theory of competitive exclusion and provide examples. How does this concept relate to fundamental and
realized niche?
9. Distinguish between interference and exploitation competition and provide examples.
Ch 14 Molles – Predation, Herbivory and Parasitism
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Intro: Prickly pear cactus (Opuntia) was introduced into Australia as an ornamental, but became an overwhelming,
unchecked member of the ecosystems. A few unsuccessful attempts were made to eradicate it; eventually, the cactus
moth (Cactoblastis cactorum) was introduced from S. America.
The larvae of this moth feeds on growing shoots of the prickly pear and quickly destroys the plant - nipping off the bud, and
inoculating it with various pathogens. After they became established in Australia, cactus moth effectively controlled prickly
pear, but did not eradicate it. The cactus can infiltrate moth-free areas and get a start, so that there is a constant check and
balance between the 2 species “ low level equilibrium in a constantly shifting mosaic of isolated patches”. The moth
population remains at low levels in remaining stands of cactus today.
The balance between the two depends in part on the adaptations evolved by both predator and prey over generations of
interaction.
A. all life forms are both consumers and victims of consumers. Predation, herbivory, parasitism are so common bc
everybody’s got to eat.
1. Consumer-resource interactions
2. Paine – starfish predation maintains tide pool diversity - keystone species
3. Consumer benefits, resource population is typically diminished
4. Populations are controlled from below by food availability and resources, and from above by consumers.
5. Consumers
a. predator
b. parasite
c. parasitoid
d. herbivores
e. Detritivores
B. Predators have adaptations for exploiting prey
1. prey sizes vary
2. as prey size increases relative to predator size, prey become more difficult to capture.
3. A predator’s form and function are closely tied to its diet
C. Mammalian predators and prey size
1. Chris Carbone of Zoological Society of London - predators weighing less than 45 lbs
D. Prey have adaptations for escaping predators
1. hiding, escape and active defense
2. swiftness
3. plants
4. where animals are able to hide or seek refuge
5. Where prey cannot hide, they adopt protective defenses
6. slow moving animals also protect themselves
7. crypsis and warning colorations
8. Mimicry - animals mimicking unpalatable animals
a. Batesian mimicry
b. Mullerian mimicry –
E. Parasites have adaptations to ensure dispersal between hosts
1. parasites are usually much smaller than hosts and live either on surface (ticks, mites, fleas, lice) or in body
2. parasite-host systems feature adaptations for virulence and resistance
F. Plants have chemical and structural defenses against herbivory
1. plant defenses include
2. structural defenses include
G. Herbivores effectively control some plant populations
1. European Klamath weed
2. in grasslands, native herbivores typically consume above ground biomass.
Ch. 17 Lesson Objectives
1. Describe 3 different types of resource-consumer relationships
2. Describe the effects on the populations of each of these relationships
3. Define the following:
predator
parasite
parasitoid
herbivore
detritivore
4. Describe how predation affected competition in Paine’s classic tidepool study
5. Describe the effect of predator size on prey size
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6. Describe how form is related to function in predators in dentition and digestive tract structure.
7. Describe adaptations of prey to avoid predation.
a. when is it effective for prey to run vs. hide?
b. what effect does hiding have on prey?
c. what possibilities are there other than running or hiding?
8. Describe and give examples of 2 different types of mimicry.
9. Define crypsis and warning coloration and give examples.
10. What are adaptations of parasites to get from one host to another?
11. How are parasites and hosts adapted to each other?
13. What types of plants are preferred by herbivores?
14. What are inherent plant defenses, and what defenses are adaptations developed by various plants? List 3 different
classes of plant defenses and give examples
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