Bio 171 Lecture 6: Species Interactions I: Predation, parasitism, and herbivory

Abdomen:

3rd body segment in shared derived traits for subphylum hexapods.

Arthropod:

Phylum of animals (insects, crabs, and shrimp) contains >1/2 of all known animal species; distinguished by their chitin exoskyloton bilateral symmetry segmented bodies and 6 jointed appendages with complex organs. Dominant herbivores.

Chitin:

Modified strong polysaccharide containing nitrogen that makes up the cell walls of fungi and the hard exoskeletons of arthropods. Gives arthropods their versatility.

Commensalism:

Interaction b/t 2 species where one species benefits and the other is unaffected.

Community:

Set of all pops. found in a particular place at a particular time.

Constitutive defense:

A defense that is always produced; contrast with inducible defense.

Inducible defense:

Defense only produced when a threat is detected; contrast w/ constitutive defense.

Ecdysis (Molting):

Process where arthropods molt their external skeleton during growth, replacing it with a larger one.

Ectoparasite:

Parasite that feeds on external side of host. (ex: ticks, fleas).

Endoparasite:

Parasite that lives within host (ex: measles, HIV).

Facultative:

organism that can survive with or without oxygen

Head:

1st body segment in shared derived traits for subphylum hexapods.

Hexapod:

Insect/closely related wingless, six-legged arthropod.

Herbivory:

Enemy-victim interaction where one species consumes plant tissues.

Insect:

The most diverse of the 4 main groups of arthropods, w/ a head, thorax, and abdomen, and 6 walking legs.

Macroparasite:

Parasites that are macroscopic (ex: worms, arthropods).

Microparasite:

Parasites that are microscopic. Short generation time (ex: bacteria, fungi).

Obligate:

Type of mutualism in which one participant requires the other to survive.

Parasitism:

Enemy-victim interaction b/t smaller organism partially consuming host tissue’s nutrients to live on for a long time.

Predation:

Enemy-victim interaction b/t organisms in which the predator consumes the prey.

Thorax:

2nd body segment of shared traits for subphylum hexapods.

Compare predation and parasitism.

Both predation and parasitism are good for one species (predatorparasite) and bad for the other (prey/host).

Understand what the general term “enemy-victim” means.

Interaction where one organism benefits and the other is harmed.

Explain how plant defenses can be co-opted by their herbivores.

Plant defenses can be co-opted by their herbivores when the herbivores "steal" the plant's defenses and use them to defend themselves.

Describe how predators and parasites can regulate prey/host population sizes.

Parasites can regulate population by density dependent regulation- a population is more likely to be affected if the population is large. Predators can regulate prey population sizes in prey-predator pop. cycles.

Explain how predators can change prey behavior and influence all vital rates, and how they can exert strong selection on prey.

B: predators may decrease if prey lower feeding rates. I: prey may immigrate into lower predation habitats. D: Increases. E: prey may leave to avoid predation.

Explain the distinction between obligate versus facultative parasites and describe the ways biologists categorize parasites.

Obligate parasites can’t complete life cycle w/o suitable host while facultative can. Descriptions: ecto/endoparasite, micro/macroparasite.

Explain how parasites can change host behavior and influence host population size; also explain their importance in food webs and how they can dominate biomass in ecosystems.

To promote transmission of parasite. Parasite may use food web to transfer energy.

Explain how the nature of interactions between species can change as environmental conditions change.

Describe the features that distinguish arthropods from other animals, the diversity of arthropods, and some drivers of arthropod diversity.

Give defining characteristics of Hexapods (insects) and explain their importance in mutualistic and consumptive interactions.

Describe how monarch butterflies co-evolved to be a main herbivore of milkweed.

How is population ecology different from community ecology?

Population ecology is the interaction of many organisms of the same species in their environment hile community is the interaction of a group of species in their environment.

What is an example of how an interaction can affect the evolution of both interacting species?

What interactions are classified as enemy-victim interactions?

Predation, parasitism, herbivory.

In the video, what advantage does the Cordyceps parasite gain from causing an infected insect to crawl upwards? How does the Cordyceps fungus affect the diversity of the jungle?

It’s virulent nature spreading spores in the air can infect insects in the vicinity. Can cause the extinction of many insects.

Describe how hosts and parasites, insects and angiosperms, and predators and prey co-evolve.

How do scientists determine if an interaction is truly parasitic? How does this relate to studies of sea birds?

If there is a decline in a host specie’s fitness. Sea birds were more likely to abandon their nests when there were more ticks.

How did scientists determine that parasites are common and have large biomass in an estuarine food web? How does the log scale on the y-axis of the parasite biomass graph affect how these results are interpreted?

By dissecting and weighing the biomass of infected organisms with uninfected organisms. Signify the large changes in density.

Describe how Cordyceps and Toxoplasma parasites alter host behavior.

Cordyceps… Toxoplasma parasites altered host brain to be aroused by cats.

In the Toxoplasma experiment, why was there a rabbit urine treatment? In the results graph from this experiment, what does the horizontal dashed line represent and why is it marked on the figure?

As a positive control to ensure that it is only cat urine mice are attracted to.

What kind of behavior would you expect a mouse or rat infected with Toxoplasma to exhibit?

What causes the negative effect of herbivory on a plant, beyond the loss of tissue that is consumed?

Influences population size and growth rates, evolution of plants, and community structure.

What information about herbivory can one glean from an exclosure experiment?

Can you put Kingdom Animalia, Subphylum Hexapoda, Domain Eukarya, and Phylum Arthropoda in order from the broadest grouping to the most narrow designation?

Domain Eukarya, Kingdom Animalia, Phylum Arthopoda, Subphylum Hexapoda.

What traits are exhibited by all insects? Do insects have some or all of the traits arthropods have? What about metamorphosis and ecdysis?

Exoskyleton made of chitin, 3-body segments, jointed appendages, ecdysis, not all insects undergo metamorphosis.

How are arthropods used in bio-inspired design?

Arthropods are used as a model for different types of engineering problems due to they’re way of navigating terrain.

What are some reasons insects are important in communities?

Plant mutualists. Herbivory and pollination interactions are part of co-evolution.

What advantage do monarch butterflies gain from feeding on milkweed as

caterpillars?

Gain chemical defense from predators due to toxicity in milkweed.

Can predators maintain prey populations at the prey's carrying capacity? Why or why not?

No b/c it isn’t intraspecific competition; it can maintain the population at an entirely different oscilate equilibrium. Prey-predator pop. cycle.

In a predator-prey population cycle graph, why are there two different y-axes (left and right)? Which population is higher - predator or prey?

In the Krebs, et al. (1995) experiment, why was each test and control group included? Why did the study last for more than 10 years?

To ensure that the same behavior seen in natural environments were still observed in a manipulated one.

What types of defenses have evolved in prey and/or plant populations to help them

avoid predation or herbivory?

Be cryptic (camflouge), poisons, armor (thorns), speed, tolerance.

Why are there two different groups in the experiment testing whether mussels have constitutive or inducible defenses against crab predators? Why were the crabs fed only fish during the course of the experiment?

Why are some defenses constitutive, and some are inducible? Shouldn't there just be one best defensive strategy?