EcoEvo Exam 3

Define community

A group of populations occupying a particular space (or habitat)

Define Symbiosis

A close and long term interaction between species (positive, negative, or neutral).

What are the 5 types of symbiosis?

1. Competition (both harmed)

2. Exploitation (one benefits one is harmed)

3. Mutualism (both benefit)

4. Commensalism (one benefits the other is not affected)

5. Amensalism (one is harmed the other is not affected)

Define exploitation

One organism benefits and the expense of another organism.

Define parasitism

An organism lives in or on another organism.

Define parasite load

The number of parasites an individual host can harbor.

Define infection resistance

The ability of a host to prevent an infection from occurring.

Define infection tolerance

Ability of a host to minimize harm once an infection has started.

What is a parasitoid? What other symbiotic interaction does this encompass and why?

A parasitoid is an organism that lives within and consumes the tissue of a living host, eventually killing the host. Encompasses exploitation and parasitism since both include one organism benefiting and one being harmed.

What are the two main categories of parasites? What are costs and benefits of each?

• Ectoparasite: a parasite that lives on the outside of an organism

Costs = Not as easy to feed on host, more exposed to natural enemies, exposed to external environment.

Benefits = It’s not difficult to move to and from a host, not exposed to the host’s immune system.

• Endoparasite: a parasite that lives inside an organism

What are the 6 types of endoparasites? Name an example of each. Do any “dance the line” of being a true parasite?

• Viruses: tabacco mosaic virus

• Prions: Mad cow disease

• Protozoans: Toxoplasmosis

• Bacteria: Salmonella

• Fungi: Chestnut blight

• Helminths: Liver flukes

Prions dance the line of being true parasites since they’re not actually living just misfolded proteins.

What are the 5 main categories of characteristics that are considered in parasite-host dynamics? Can you name an example?

1. Parasite transmission (Horizontal transmission between individuals other than parent and offspring, vertical transmission from parent to offspring).

2. Modes of entering host (piercing the tissue of the body with leeches)

3. Jumping between species (how HIV jumped from chimps to humans)

4. Reservoir species (Birds giving mosquitoes avian malaria which is then transferred to other organisms)

5. Host’s immune system (HIV can hide from the immune system so it can’t be detected)

How are parasite-host populations modeled? What are the three main components to the model and what do they mean? What does the reproductive rate of infection mean, what is the formula for it, and what does the output tell you about the infection within a population?

1. Susceptible

2. Infected

3. Resistant

or SIR

• Reproductive rate of infection (R₀): Number of secondary cases produced by a primary case.

R₀= (new infections)/(recoveries) = (b*S)/g

Where b = infection rate, S = number of susceptible individuals, and g = recovery rate

R₀ > 1, disease increase

R₀ < 1, disease decreases

What are the 5 primary adaptations of parasites to benefit their fitness? Do hosts have adaptations too? Where is selection pressure highest – on the host or the parasite, and why?

1. Sensory strategies

2. Synchronization of reproductive cycles to that of host

3. Alteration of host behavior to increase chance of transference

4. Alteration of host metabolism to increase host life-span

5. Avoidance of host immune response (molecular mimicry)

• Yes, hosts have adaptions as well, like how some plants and animals can produce antibacterial and antifungal chemicals.

• Pressure is higher on the host because if it fails it could die or fail to reproduce

What is the Red Queen Hypothesis?

Coevolution of predator and prey, in which improvements in one species is countered by evolutionary improvements in the other species so that they are constantly competing but no one ever wins.

Define coevolution

Successive, reciprocal evolutionary change in each of two species in response to selection imposed by the other species.

Define reservoir species

Species that can carry a parasite but do not succumb to the disease that the parasite causes in other species.

Define zoonotic disease

Infection transmitted from an animal to a human.

What is the optimal foraging theory?

A model describing foraging behavior that provides the best balance between the costs and benefits of different foraging strategies.

What are the 4 optimal foraging strategies? Give an example of each

1. Central place foraging strategy (how a bird always returns to its nest after foraging)

2. Risk-sensitive foraging strategy (a fish feeding in a location with enough worms that makes the predator risk worth it)

3. Optimal diet composition foraging strategy (A coyote choosing a jackrabbit over a vole because it provides more energy even though it takes more effort to catch)

4. Diet mixing (Grasshopper nymphs that eat a variety of things grow faster than nymphs who only consume one type of food).

Choose an optimal foraging adaption and name the benefit and cost associated with it.

Diet mixing

Benefit: higher yield and health

Cost: more difficult to obtain

Define competition

Negative species interactions between two species that depend on the same limited resource to survive, grow, and reproduce.

Define renewable resource

Resources that are constantly regenerated.

Define nonrenewable resource

Resources that are not regenerated.

Define Liebig’s Law of the Minimum

Law stating that a population increases until the supply of the most limiting resource prevents it from increasing further.

Define niche

Range of abiotic and biotic conditions an organism can tolerate.

Define allelopathy

A type of interference that occurs when organisms use chemicals to harm their competitors.

What are the terms for competition between individuals of the same species versus
individuals between different species? What are the three types of competition? Can you define and provide an example for each?

• Intraspecifc competition is among the same species

• Interspecific competition is among different species

1. Resource: Individuals consume and drive down the abundance of a particular resource

2. Direct interference: Competition that results in competitors seeking harm (male rams competing for a female).

3. Apparent: Indirect competition between two or more victim species that share a common enemy (Competition for shelter among birds and squirrels in a forest being used for logging by humans).

What do Lotka-Volterra competition equations help estimate? What equation is the basis of their competition equations? What is α and β? Can you determine the outcome of the competition given different placements of isoclines? Are the end points stable or unstable? What does the isocline mean? What are the assumptions of these equations?

• Help estimate the strength of competition and the effects on populations