Review for Exam III
Make sure to cover the various chapters on herbivory, Parasitism, community ecology includes species diversity and diversity indices.
Textbook:
1.
Townsend et al 2008. chapters 8, section 8.5.3 on disease dynamics and cycles, 9, chapter 9:page 309-321, and 10
In bold are chapters that should be completely covered .
Read 2 articles on parasitoids
2.
“Parasitoid secretions provoke ant warfare” by Thomas et al. 2002.
3.
Imported parasitic wasp helps control red gum lerp pysillid Dahlsten et al. 2005
(article available online)
Herbivory
• How do plants deal with herbivory?
chemical and mechanical defenses
• What is the response of herbivores?
strongly influenced by plant defenses, and the amount of nitrogen in the plant
• remove 15-18% of terrestrial plant biomass; over 50% in aquatic systems
•
change plant communities by preferentially eating dominant plant species
Examples of Plant Defenses

Alkaloids

Mustard oils

Terpenoids

Phenylpropanes
Quantitative defenses and Qualitative defenses
Modeling herbivory and Functional response (see your notes)

How an individual predator responds to prey density The three types of functional response

Type I: Individuals consume more prey as prey density increases (linear)

Type II: Predators can become satiated and stop feeding, or limited by handling time.

Type III: Feeding rate is similar to logistic curve; low at low prey densities, but increases quickly at high densities (sigmoid)
Dealing with herbivory Table 1

Pest control techniques: advantages and disadvantages

Pesticides, biological control with predators and parasitoids

Growth regulators chemicals that mimic growth hormones in insects
List 3 main pest control techniques, give advantages and disadvantages of each technique
Why is using biological control methods considered a last resort?

Effects on non-target species

Biological control agents are essentially uncontrollable (most chemicals degrade)

What is an epidemic?
• In studying the spread of a disease what’s the most important parameter? the average number of new cases of a disease

What factors affect Rp ? BNfL

What are the major characteristics for diseases that persist in large populations? give examples

What are the major characteristics for diseases that persist in small populations? give examples

For parasites with an outside vector Rp the number of new cases depends on the ratio of the number of vectors to hosts
Problems

Calculate the number of new cases that can arise if a person with a sexually transmitted diseases has 6 new partners

The host remains infectious for 15 years

The transmission rate is 0.1

N = BfL 6 x 15 x 0.1 = 9 new cases from one infected person

Calculate the critical number of individuals needed for a disease to persist in the population if B = 0.01, f = 5 days, L = 0.0002

Using the equation

N t
= 1/BL

1/0.01 x 0.0002 = 500,000
What are the major steps in the life cycle of the HIV virus?
• Attachment to the Lymphocyte Membrane, entry and release of genetic material.
• Reverse Transcription : Converting viral RNA into DNA
• Integration : the DNA can then be integrated (inserted) into the DNA of the lymphocyte. The virus has its own enzyme called " integrase " that facilitates incorporation of the viral DNA into the host cells DNA. The integrated DNA is called a provirus .
• Transcription : Back to RNA
•
•
Translation :RNA to proteins
Viral protease, assembly and budding
Using diagrams discuss natural resistance to HIV
Entry of the HIV virus into CD4 cells is dependent on a CCR-5 (a special protein) or
CXCR4.
These proteins are the main receptors to which the virus needs to bind in order to enter the cell. People with natural resistance to HIV have mutations in chromosome 3, thus the CCR-5 is either absent or defective.
Some people are heterozygous; i.e. +-CCR-5 (partial protection), others are homozygous
--CCR-5 (full protection from HIV infection) homozygosity for HLA- Bw4 alleles is also associated with the ability to remain AIDS free and to maintain a normal CD4 T cell count
Questions

What is a community?
What are the main characteristics of a community? species composition temporal trophic guilds and niches
Where do we find the highest percentage of threatened species?
Tropical forests and oceanic islands have the highest percentage of threatened species
What are some examples of direct positive and negative interactions?
Give an example of an indirect positive interaction
In communities we find
1.
Direct negative interactions
2.
Direct positive interactions
3.
Indirect positive interactions
Direct negative interactions (give examples)
1. Predation
2. interference competition
3. inhibition of recruitment
4. inhibition of feeding
Indirect effects: Removal of a species from a community does not always lead to the expected result!
Examples of Indirect positive interactions
1.
Habitat facilitation
2.
Cascading trophic interactions:
3.
Keystone predation: By reducing prey population densities, a predator can reduce competition among prey species and promote their coexistence
Predator-mediated coexistence- Keystone predation: By reducing prey population densities, a predator can reduce competition among prey species and promote their coexistence
( examples of species that coexist in the presence of the key stone predator; chitons, limpets, acorn barnacles, bivalves, and whelks)
Habitat facilitation: occurs when one species indirectly improves the habitat of a second species by altering the abundance of a third interactor.
Cascading trophic interactions: predatory effects at one trophic level affect community structure, at trophic levels below the one affected directly
Example: in the salt marsh environment
Bird predation and consequences on 3 limpet species and their algal food
Bird predation:
1.
keeps goose barnacles down

2.
reduces grazing pressure of limpets on fleshy algae
Bird exclusion:
1.
Increased abundance of L. digitalis
2.
decreased abundance of L strigatella (competitively inferior to other limpets)
• L. digitalis (light colored) found on light colored barnacles (for camouflage)
• L. pelta (dark colored) found on dark California mussels (see Figure 9.18, and get more details from page 310).
Be able to explain the difference between top-down and bottom-up control of food webs
Distinguish between the two types of diversity indices emphasized in class. Give equations. Why are diversity indices important?
Type I indices are most sensitive to changes in the rare species in the community example ( Shannon Wiener index)
Type II indices are most sensitive to changes in the more abundant species example
( Simpson's index)
Be able to calculate the Simpson’s and Shannon index for several populations and comment on results.
Diversity among areas can be compared using
• Diversity indices
• Similarity coefficients
– Comparison involve a simple presence-absence matrix for two areas, A and B
• a = number of species common to both sites
• b = number of species in site B, but not in A
• c = number of species in site A, but not in B
Similarity coefficients
Jaccard coefficient
C j
= a / (a + b + c)
Cluster analysis
Types of clustering
• Single linkage clustering (nearest neighbor method )
• Complete linkage clustering (farthest neighbor method)
• Average linkage clustering (avoids extremes introduced by single and complete linkage clustering)
Example of Single Cluster Analysis using the Jaccard similarity coefficient
• Start by calculating the similarity coefficients for the two sites in the oak wood habitat and for the 3 sites in the conifer habitat
• Then arrange the similarity coefficients in a table or matrix

• To build a dendogram , start by finding the greatest similarity coefficient
• The greatest similarity coefficient is between the conifer sites 2 and 3 = 0.7
• The next highest similarity coefficient is between the Oakwood sites 1 and 2 = 0.65
• The next highest similarity coefficient is 0.47 for the conifer sites 1 and 2 etc.
•
The last connection to make is between the oak cluster and the conifer cluster
Look at other examples of cluster analysis
THIS IS JUST A GUIDE: QUESTIONS WILL MAINLY BE FROM THIS STUDY
GUIDE BUT MIGHT ALSO INCLUDE QUESTIONS FROM ELSEWHERE. YOU
ARE STRONGLY ENCOURAGED TO READ YOUR LECTURE NOTES AND
TEXTBOOK