Ecology Exam 4 Review

ECCB 205 WKs 13-15

Competition

interaction b/w two or more organisms using the same limited resource (when fundamental niches overlap)

(-/- interaction, affects both population growth)

Fundamental Niche

* environmental conditions under which a species can survive and reproduce
* temp, rainfall, nutrient levels, etc. (abiotic factors)
* not restricted by interactions with other species

Realized Niche

* Environmental condition in which the species is actually found in nature
* A subset of the species’ fundamental niche
* Restricted by BIOTIC interactions (competition, predation, parasitism)

Intraspecific Competition

Competition among members of the same species

Interspecific Competition

Competition between members of different species

What alters competition?

* Disturbances
* Predation and herbivory
* Other interspecific interactions

Amensalism

(-/0) interaction

Commensalism

(+/0) interaction

Mutualism

(+/+) interaction

Competitive exclusion principle

No two species can coexist in the exact same niche

* Does not uphold in all situations (paradox of plankton)

Exploitative (resource) Competition

competition in which individuals consume and drive down the abundance of a resource to a point that other individuals cannot persist

* indirect competition

Interference Competition

when competitors do not immediately consume resources but defend them, preventing est. of a competitor

* Direct competition

Allelopathy

a type of interference competition that occurs when organisms use chemicals to harm their competitors (effective strategy for invasive plants)

Preemption

type of interference competition determines by who finds and occupies a place first (think trees)

Territoriality

Active defense of resources that excludes other organisms

Browsers

eat woody plants

Grazers

eat herbaceous plants (grass, forbs, herbs)

Granivores

eat seeds

Frugivores

eat fruit

Consumer- resource dynamics

* populations of consumers are self-limited: as they grow, their resources become scarcer
* Consumers are limited by density dependent factors

\
* Resource population are limited by consumers
* Resources tend NOT to be limited by density dependent factors

Predator-Prey Cycle

Predator/prey cycles increase and decrease in regular cycles

Lotka-Volterra model

Reproduces cyclic predator-prey interactions

* Period and frequency depend on physical environment
* Stochastic (random) events will alter it and may cause extinction
* Model does NOT include randomness
* Model assumes closed system, no refuge for prey, no handling time for predators, prey grow expo. w/o predators, and predators consume infinite amounts of prey
* Model can have added parameters to fit reality

Lotka-Volterra model equation

rprey: per capita growth rate of prey (intrinsic growth rate)

Nprey: # of prey

Npredator: # of predators

a: search efficiency of predator (attack rate)

b: conversion rate (converts encounter rate to # of new predators produced)

m: mortality rate (of predator in predator eq.)

Parasites

Endo- internal

* runs into hosts immune defenses

Ecto - external

* easier transmission from host to host
* non-steady supply of food
* more variable environment

Nutritional Defense

Nutrients is stored away from available parts of plants. Areas exposed to herbivores are not nutritionally dense (dominantly in plants)

Tolerance Defense

Changes to plant growth in response to herbivory (dominantly in plants)

Behavioral defenses

Alarm calling, reduces activity, mobbing, schooling/flocking, growing/ flowering when herbivores are scarce… etc (predominantly in animals)

Physical Defenses

Physical features to protect animals or plant from being eaten or injured

\*\*\*

Defenses can be phenotypically plastic

Crypsis Defense

(both animals and plants) Cryptic coloration and disruptive coloration to hide animals to avoid predators

Chemical Defenses

(both animals and plants) Ex: tobacco producing nicotine, Bombadier beetle mixing chemicals to spray predators with boiling hot liquid

Aposematic coloration

Conveys chemical defense before attack occurs

* Warning coloration (aposematism) where distastefulness evolves n association with very conspicuous colors and patterns
* Predators can have innate aversions to aposematic colors; others learn to avoid through experience

Mimicry Defense

Individuals without chemical defenses can mimic aposematic species with chemical defenses by copying physical traits

\
* Batesian mimicry: when palatable (eatable) species evolve warning coloration that resembles unpalatable species
* Mullerian mimicry: when two unpalatable species evolve similar warning coloration to reinforce coloration-unpalatability association in predators

Coevolution

when two or more species affect each other’s evolution; mutualistic species evolve mutual adaptations to promote the relationship

* evolve by natural selection imposed by each other, reciprocal adaptation
* may be faster and more evident in antagonistic interactions b/c they directly impact survival (evolutionary arms race)
* selection for prey defenses should favor the selection for counter-adaptation in predators

Costs of sexual reproduction

Evolutionary arms races occur more frequently: sexual organs require considerable energy and resources, mate attraction requires time and energy, copulation exposes disease

Red Queen hypothesis

* Extinction rates (macroevolution-between species): extinction appears to be a random process probably due to COEVOLUTION which forces organisms to constantly evolve
* Sexual reproduction (microevolution-within species): hosts are ablet o present a moving target for evolving pathogens through sex and genetic recombination
* Hypothesis: Species that evolve fast enough to keep up with (or outpace) evolution in their enemies will generally persist longer than those that evolve more slowly/. Thus, like the Red Queen, a species and its enemies continually evolve “to keep in the same place”

Benefits of sexual reproduction

* coping with environmental variation
* coping with parasites and pathogens

(via genetic variation)