January 21

Science 171 with Barry at University of Michigan - Ann Arbor

About this deck

By: Ali Van Belkum
Created: 2011-01-23
Size: 52 flashcards
Views: 11

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Types of predation

-predator-prey interactions

-parasitoid-host interactions

-parasite-host interactions

-plant-herbivore interactions

Predator-prey interactions

sometimes lethal

- example = lions eating zebra

sometimes non-lethal

- example = sea slugs eating coral (partial consumption of Marine Animals by some Nudibranchs -- sea slugs)

Parasitoid-host interactions

almost always lethal

(parasitoid attacking aphids)

Parasite-host interactions

often with vectors, intermediate hosts, and quite complex, usually non-lethal

Effects of predators on prey

- BIDE: predators can influence death rates of their prey and therefore influence rates of population growth

- Predation is a +/- interaction and can be a source of negative feedback (density dependence)

Predators have the potential to...

regulate prey populations around and equilibrium

Predators can...

Generate equilibria!

-resource limitation can generate an equilibrium called carrying capacity through intraspecific competition

-predation can also generate a different equilibrium that occurs below carrying capacity

Predators and equilibria graph

E1 = resource limitation (carrying capacity)

E2 = predation

x-axis = time

y-axis = prey density

Population cycles (example)

changes in the density of larch budmoth in Europe are drive largely by density-dependent mortality imposed by parasitoids

Population cycles (another examples)

- lynx are specialist predators on hares

-cycles occur in part because the population size of the predator influences the population growth rate of the prey and vice versa

Cycles graph (hare and lynx)

left y-axis = hare population in thousands

right y-axis = lynx population in thousands

x-axis = year

(there are far more snowshoe hares than lynx)

Interactive effects

-changes in the abundance of snowshoe hare over time are influenced both by predation and by the availability of food for hares

-the forces of predation by lynx and competition for food interact to drive the population dynamics of hare

Population cycles experiment: (q, hypoth, null hypoth)

Question: What factors control the hare-lynx population?

Hypothesis: Predation, food availability, or a combination of those two factors controls the hare-lynx cycle

Null hypothesis: The hare-lynx cycle isn't driveby predation, food aval, or combo of 2

Experiment setup (what type of forest? how large? how long?)

-boreal forest

-1km^2

-11 years (duration of one cycle)

Study 7 plots (3 unmanipulated, 1 electrified fence excludes lynx and free access by hares, 2 plots extra food, 1 plot extra food + fence so no lynx)

Predictions (of each hypothesis)

Prediction: hare populations in at least one type of manipulated plot will be higher than the average population in control plots

Prediction of null hypothesis: hare populations in all of the plots will be the same

Results (graph)

y-axis: average hare population during declining years of cycle

x-axis: control/predators excluded/food added/predators excluded, food added

Conclusion:

Hare populations are limited by both predation and food availability. When predation and food limitation occur together, they have a greater effect than either factor does independently.

Effects of predators on prey

- don't just influence prey death rates

- can also influence the other vital rates (immigration, emigration, birth)

When can all vital rates change?

When prey change their behavior in response to the presence of a predator

Example of all vital rates changing

-Bluegill sunfish (Lepomis macrochirus and largemouth bass)

-Sunfish swim away (emigration) from patches with bass and forage at the edges of ponds & lakes (immigration to edge populations)

Example continued

-Sunfish feeding rates are lower in edge populations because the food source is poorer

-Sunfish birth rates then decline as a result of lower feeding rates

Species diversity in communities (example and graph)

Predator = pisaster ochraceous

Prey = mytilus californianus

y-axis = number of species present

x-axis = year

around 20 different species when pisaster present, less than 5 when not

Pisaster/mytilus experiment

-Classic experiment by Paine

-Sea star Pisaster maintains high species diversity in the shore invertebrate community

-when pisaster is removed, the mussel Mytilus outcompetes most other species and species diversity declines

Keystone species (and example)

-Pisaster is an example of a keystone species

-Keystone species have a dramatic influence on the diversity of species in their community

-The effects of keystone species are disproportionately high in comparison to their abundance (or biomass)

Herbivory

-predation on plants

-many different kinds of organisms attack plants

In herbivory, we usually distinguish between...

Herbivores (insects, mammals, some reptiles, some birds)

AND

diseases (viruses, bacteria, fungi, nematodes)

*Herbivores rarely kill plants whereas diseases often do*

Herbivores can influence...

plant populations and community structure!

Example of this

black-tailed deer

-exclosure of black-tailed deer from a forest in the Pacific northwest

-deer reduce plant abundance

-deer change plant community composition (identity of remaining species)

-black-tailed deer appear to be a keystone species!!

Why is the world green?

-if you go for a walk in the countryside in summer, there is usually an abundance of green plants

-why don't herbivores consume all of the green plant material that is available to them?

Hypotheses about why the world is green

1. herbivore populations are regulated below carrying capacity by predators

2. plants are not good sources of nutrients (nitrogen, phosphorus) and can't support high herbivore populations

Continued...

3. Plants are well defended against herbivores and respond to attack by increasing their defenses

why hypothesis is supported?

-there is support for all three of these hypotheses and they are not mutually exclusive

-it seems very likely that predators, nutritional quality, and plant defense all interact to maintain plant abundance

Example of something being kept below carrying capacity

-Parts of the Midwest and Central States

-grasshopper populations are kept below carrying capacity in grasslands because of high levels of bird predation

Plant tissues...

lower in nitrogen concentration than animal tissues

Plants exhibit...

defenses against herbivory!

-spines & trichomes

-shiny leaves

-trembling leaves

-silica (especially grasses)

Plants can release..

chemical defenses:

-taxol

-caffeine

-salicylic acid

-digitoxin

-oubain

Types of defenses

-Constitutive defenses

-Induced defenses

Constitutive Defenses

-many plant defenses are present at all times, whether herbivores are feeding on the plant or not

Example of constitutive defense

trichomes on common milkweed plants are abundant in the presence or absence of herbivory – they are constitutive defenses

Induced defenses

-common milkweed plants also have inducible defenses

-they make more of the toxin "cardenolide" when attacked by monarch larvae

-they also produce volatile signals to attract predators when attacked by monarch larvae

What else can have induced defenses?

-animal prey

-some crabs feed on mussels, opening them by crushing the shells

-mussels shells grow thicker when mussels detect the presence of crabs in the environment

LOOK AT CRAB/MUSSEL DIAGRAM IN THE BOOK!

don't forget to loooook atttt itttt dipshit.

Evolutionary change

-interactions among species can lead to changes in the abundance and distribution of species as well as evolutionary change in traits such as behavior, physiology and morphology

Evolutionary change continued

-predators and herbivores can cause EC in their prey, leading to greater levels of defense

Examples

-evolved constitutive defenses in animals

-camouflage: blending into the background

-schooling: safety in numbers

-weaponry: fighting back

More evolved constitutive defenses in animals

-müllerian mimics (all 3 species have toxic stings)

-batesian mimics (non-toxic mimic of toxic species)

*mimicry can protect both dangerous and harmless species*

Müllerian mimics

-paper wasp

-bumblebee

-honeybee

Batesian mimics

-hornet moth

-wasp beetle

-hoverfly

Another example of something that mimics?

an octopus that mimics: thaumoctopus mimicus

-appears to mimic at least 15 different species of sea animal

-to confuse potential predators

What happens over time when predators/prey develop new defenses?

-if prey become better defended over evolutionary time, then predators may also evolve better ways to attack

-result = evolutionary arms race = prey become ever better defended while predators become ever better at overcoming those defenses

Example of "arms race"

Recorded in some mollusc species

-mollusc prey become more heavily armored over evolutionary time to protect against their predators

Predators of mollusc

marine whelks (drill holes to reach their prey) and crabs (crush their prey)

-over evolutionary time, whelks have evolved greater drilling ability and crabs more massive claws with greater crushing power

About this deck

By: Ali Van Belkum
Created: 2011-01-23
Size: 52 flashcards
Views: 11

About StudyBlue

“I have used this website for three exams, and I see a huge difference in my test results.”
Naj