Predation Flashcards
In what environments do predator/prey interactions tend to oscillate?
simple environments
Expectations for single predator + prey
- Local extinctions will be corrected by immigration
2. prey population will fluctuate without population changes in predator
4 kinds of predator/prey graphs
- Stable limit cycle
- Stable point
- Dampened oscillation to stable point
- Increasing oscillation to extinction
describe spider mite experiment
see notes
population changes in wood mice, bank vale, and tawny owl
mice and vole populations cycled, but tawny owl didn’t bc it has a diverse diet
Prey refuge characteristics
smaller populations are better at hiding
-only prey above a certain number are subject to predation
Gause’s experiment with Paramecium caudatum and Didinium nasutum
- without refuge, both went extinct
- with refuge, only the predator went extinct
- with refuge and restocking, the populations oscillated
Numerical response to increased prey
predator population rises due to increased birthrate and immigration
Functional response to increased prey
Predation rate of each individual predator increases
Holling’s 4 components of feeding rate
- Searching
- Capturing
- Handling
- Digesting
3 types of feeding rate curves
- filter feeding (steep increase; then plateau)
- general invertebrate (slow upward curve; plateau)
- learning predator (S-shaped curve)
Total predation rate
(numerical response) x (functional response)
Secondary compounds
toxins produced by plants to make them unpalatable to eat
What species make up more than half of known terrestrial species on earth (besides microbes)
land plants (mainly angiosperm) and insects
Ehrlich-Raven theory assumptions
- herbivory harms plants
- plants evolve defenses
- herbivore activities, growth, reproduction, and evolution have been guided by plants’ defenses
Generalists
herbivores that can eat many different types of plants
specialists
herbivores that can only eat one specific species, genus, or family
Allelochemicals
made by plants to eliminate everything around it (e.g. black walnut)
Classes of chemical defense
- Terpenoids
- Glucosinolates
- Alkaloids
- Glycosides
- Phenolics
Terpenoids
formed from acetyl coenzyme A
- built on 5 carbon units assembling into bigger molecules
- menthol, pinene, isoprene, geraniol
Glucosinolates
- Sulfur and Nitrogen containing compounds
- found in Brassica genus (cabbage + mustard)
- bitter tasting
Alkaloids
- nicotine, tobacco, codine, morphine, strychnine
- some steroids
- theobromine in chocolate and caffeine in coffee
Theobromine
- super bitter
- found in cocoa, tea leaves, and kola nut
- causes sleeplessness, tremors, restlesness, anxiety, and increased urination
- dogs + cats metabolize it slowly and can be poisoned by just 50 mg
Caffeine
- in coffee, tea, and kola nut
- causes sleeplessness, tremors, restlesness, anxiety, and increased urination
- paralyzes and kills insects
- surrounds soil of coffee plant –> acts as pesticide and inhibits seed germination
Glycosides
- Cyanogenic (have nitrogen)
2. cardiac (don’t have nitrogen)
Cyanogenic Glycosides
produce hydrogen cyanide when chewed
cardiac glycosides
found in milkweed
- affects the heart
- causes vomiting and death
- milkweed sap is in digitalis, a heart drug
Phenolics
- in ferns, gymnosperms, and angiosperms
- make plant pigments and make bitter flavor in plants
- major component of wood –> lignin
- cause puckering by reducing lubricant action of glycoproteins in saliva
- deactivates digestive enzymes and makes it hard to extract amino acids
- lemons, onions, soy, berries, vanilla, tumeric, tannic acid, citrus fruits
constitutive defense vs induced defence
-always on vs response to stimuli
Physical defenses
- Prickle: sharp outgrowth from epidermis
- Spine: modified leaf or stipule
- Thorn: modified stem
