128 terms

Biology II - Ch. 56 (Community Ecology)


Terms in this set (...)

Hierarchy of complexity
- individual
- population
- community (only biotic)
- ecosystem
- biome/biosphere
Biological communities
species at any particular locality
Community is characterized by:
- species richness
- abundance
- primary productivity
Species richness
- R
- different types of species present
- N
- total number of individuals present
Primary productivity
amount of energy produced
Interactions govern:
ecological and evolutionary processes
Ecological niche
role that an organism plays in the environment
Examples of niches:
- space utilization
- food consumption
- temperature range
- appropriate conditions for mating
- requirements for moisture and more
Types of niches:
- fundamental niche
- realized niche
Fundamental niche
- area that a species can use, based on physiological tolerance limits and resource needs
- anywhere that a particular species can be
- really large area
Realized niche
- actual area where species establishes a stable population
- where the particular species is actually located
- smaller area
Causes of niche restriction:
- competitors
- predator absence or presence
- presence of herbivores
- absence of pollinators
Competitive exclusion principle
two species cannot use the exact same limiting resource
Competitors cause:
directional selection
It's better to use resources that aren't:
subject to competition
Over time, each species evolves to:
divide resources in a way that limits competition
Evolution reduces:
the overlap in resource use
Gause's classic experiment
- 3 paramecium species showed competitive exclusion principle in action (realized niche)
- each of the three species survived well on their own
- however, when two were put together, one survived well, but the other didn't
- when a third species was added, each species developed their own realized niche and learned how to divide resources to thrive well together
Resource partitioning
- promoted by competition
- subdivides niches to avoid direct competition
Resource partitioning is often seen in
similar species occupying the same geographic area
Example of resource partitioning
sympatric lizard species
Resource partitioning can result in:
character displacement
Examples of character displacement
- differences in morphology
- adaptive radiation
Competition is a __________ __________ in nature
diversifying force
Types of biotic interactions
Biotic interactions are based on whether the populations involved:
- benefit (+) from the interaction or
- suffer (-) from it
- +, +
- both benefit
Examples of mutualism
- clown fish and anemone
- ants and plants
- + , 0
- one benefits, other is unaffected
Examples of commensalism
- barnacles and whales
- oxpecker and ungulate
- + , -
- one benefits, other suffers (probably dies)
Examples of predation
- fox and squirrel
- oxpecker and ungulate (out for blood)
- 0 , -
- production of secondary substances to keep others away
Examples of amensalism
- oaks
- penicillin
- - , -
- two organisms exerting energy in fighting over food
Examples of competition
- two birds fighting over the same rodent population
- two fish species fighting over the same algae
two or more kinds of organisms interact in more-or-less permanent relationships
Interactions of symbiosis:
- mutualism
- commensalism
- amensalism
- exception: special case of predation (parasitism - doesn't kill host, so long-term relationship)
Types of symbiosis (competition and predation)
- - , -
- when two or more species or populations use the same limiting resource (competitive exclusion principle)
Both populations have _______ growth rates in the presence of the other
Limiting resource
- resource in short supply
- demand exceeds supply
Examples of limiting resources
- nesting space
- territory area
- food
- anything that both organisms need
Two forms of competition:
- interference competition
- exploitative competition
Interference competition
physical interactions over access to resources
Exploitative competition
- consuming the same resources
- large group comes in and eats everything
Examples of exploitative competition
- blue tangs eating damsel fishes' algae garden food
- swarms of birds eating everything
Competition can also occur _______ or ________ a species
between; within
Interspecific competition
- competition between two species
- inter = between two species
Intraspecific competition
- competition between members of the same species
- intra = within the same species
Competition results
- one population slows growth rates of another by using resources that are in short supply (ex: kudzu vine)
- but both lose out ultimately
- + , -
- interactions in which one species benefits and other suffers
Predation strongly influences:
prey populations
Types of predation:
- carnivory
- herbivory
- parasitism
- parasitoid
when animals (rarely plants) kill and consume other animals
Carnivorous plants
- Venus fly trap
- pitcher plant
when animals consume plants
organism "consumes" another organism (host) without killing it
Compared to predation, parasites live in _________ __________ with host
intimate association
Parasites consume their host:
slowly, but without killing it
Example of parasitic plant
- dodder
Parasites can be:
- internal or external
- obligate or facultative
- have to be there
- don't survive without host
Examples of obligate parasites
- tapeworm
- isopod in fish's mouth
if opportunity arises, they can be a parasite, but otherwise they are something else
when organisms lay eggs on or in host and host is eaten when eggs hatch
Is parasitoid symbiosis?
no, because end result is that host dies
Example of parasitoid organism
tarantula hawks
Defenses to predation
- flee
- mechanical defense
- live in groups
- masting (plant version of living in groups)
- camouflage/hide
- aposematic coloration
- secondary plant compounds
- mimicry
- run away
Examples of fleeing
- cockroaches
- antelopes
- birds
Mechanical defense
- shells
- spines
- silica
Examples of mechanical defense
- armadillos (shells)
- cacti, ceiba tree, long-spine sea urchin (spines)
Live in groups
Advantages of living in groups
- more eyes (to see predators or prey)
- confusion (murmuration)
- group defense (mobbing, attack)
- selfish herd (safety in numbers)
schooling effect
Example of murmuration
European starlings
Example of group defense
lion vs. wildebeast
Example of selfish herd
- plant version of living in groups
- masting overwhelms ability of seed predators to find and eat all the seeds
Example of masting
- moth larvae consume 38% of beech seeds in a non-mast year
- but only 3% in a mast year
- cryptic coloration
- deception
Examples of camouflage/hiding
- frogs
- praying mantis
- moth
______ animals have an option for avoiding predators
Aposematic coloration
colors that warn of toxins or potent defense
Examples of aposematic coloration
- poison dart frogs
- butterflies
- bees/wasps
Aposematic coloration and coevolution of snakes and lizards
- snake eats lizard
- snake dies
- but genetic mutations allow snakes to eat lizards and not die
Secondary plant compounds
- plant version of aposematic coloration
- chemicals produced by plants that are not needed for their primary metabolism
- they serve other functions, such as defense
- not directly needed to live
- toxins
Examples of secondary plant compounds
- aspirin
- cocaine
- opium
Mimicry (two types):
- batesian mimicry
- mullerian mimicry
Batesian mimicry
palatable prey species mimics unpalatable prey species
Examples of batesian mimicry:
- palatable milk snakes mimic unpalatable coral snakes
- palatable gopher snakes mimic unpalatable rattle snakes
- hognose snake can flatten head and hiss, have similar coloration to rattle snake, and can throw itself upside down and play dead
- butt end of caterpillar looks like snake
- spider trying to act like an ant
Mullerian mimicry
several unpalatable species resemble each other
Example of mullerian mimicry
several species of butterflies that all look similar and taste equally bad
Predation results
prey populations can explode or crash
Examples of population explosion
- white-tailed deer in Eastern US
- introduction of rats, dogs, and cats on islands
Examples of population crashes
- introduction of rats, dogs, and cats on islands caused other species to go extinct
- Stephen Island's wren in New Zealand went extinct because of one cat
Coevolution produces a strong
selective pressure on prey populations
Features that ________ probability of capture are strongly ________
decrease; favored
Coevolution ______ may ensue
one species trying to outcompete another
Example of coevolution race
bats and moths
Obligate vs. facultative
have to
Mutualism vs. commensalism
Obligate mutualism
- have to have each other
Examples of obligate mutualism
fig wasp
Facultative mutualism
can be in a relationship if opportunity arises
Obligate parasitism
have to be parasitic
Facultative parasitism
may be parasitic if opportunity arises
Example of facultative parasitism
brain-eating amoeba
Species interactions
Ecological processes =
interactive efforts
Predation reduces:
Choice of food supply depends on
abundance of prey
Superior competitors may be _________ by predation
Other species ________ when they could have been ________
survive; outcompeted
Example of predation reducing competition
- starfish eats mussels
- adding barnacles to the environment means that other species thrive, instead of being crowded out
- this means greater diversity of the ecosystem
Indirect effects
when the presence of one species may affect a second species by way of interactions with a third species
Keystone species
species that play a unique and crucial role in the way an ecosystem functions
Keystone predator example
sea star eats mussels, which alters the species richness of a marine ecosystem
Keystone modifiers (ecosystem engineers) example
beavers manipulate the environment, creating new habitats for other species
Keystone mutualist example
hummingbird and cactus relationship prevents invasive grasses from growing and taking over
Keystone species increase: