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Flashcards in Ecology Deck (485)
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451

reestablishing communities in cold/dry climate

~20,000 yrs
Yukon
glaciation

452

secondary growth forests have

almost no predatory insects
~1000 yrs to reestablish insect communities

453

ecological mechanisms for succession

stochastic events
facilitation
inhibition
tolerance

454

stochastic events (ecological mechanisms for succession)

unpredictable, who gets there first

455

facilitation (ecological mechanisms for succession)

species creates conditions favourable for a succeeding species but not itself
major process in early stages
leads to assembly rules

456

facilitation example

clover growth without soil-- clovers produce soil for other plants to grow which shade out clover

457

assembly rules

regular and sequential shift in species
species B cannot establish till species A is present

458

examples assembly rules

predators cannot colonize successfully unless prey are present
pollinators can not colonize successfully unless flowering plants are present

459

inhibition (ecological mechanisms for succession)

species inhibits the colonization of subsequent colonists
slows succession and prolongs a seral stage

460

inhibition examples

allelopathy- plants/corals
competitive exclusion- intertidal communities

461

gigartina abundance

red marine algae- high density if Ulva removed, low if Ulva present

462

tolerance (ecological mechanisms for succession)

members of serial stage are those that co-exist due to use of different resources
combines facilitation + inhibition = ghost of competition past

463

early seral stages

seed dispersal - good
plant efficiency low light- low
resource acquisition - fast
biomass- small
stability- low
diversity- low
species life history - r
seed dispersal- wind
seed longevity - long
shoot to root ratio- high

464

late seral stage

seed dispersal - poor
plant efficiency low light- high
resource acquisition - slow
biomass- large
stability- high
diversity- high
species life history - k
seed dispersal- animals
seed longevity - short
shoot to root ratio- low

465

trophic levels

the sequence of steps in a food chain or pyramid

466

what are the trophic levels from lowest

primary producer-- primary consumer-- secondary consumer-- tertiary consumer

467

why trophic levels (food chains) are unrealistic

because real life situations involve food webs

468

what determines food web complexity

number of trophic levels
chain length
connectance
linkage density

469

what is chain length (in food web complexity)

number of links running from a primary producer to a top predator

470

what is conductance (in food web complexity)

actual number of links in a food web divided by the total number of possible links (N)

471

N = (in food web complexity)

[ n (n - 1) ] / 2

472

linkage density (in food web complexity)

number of links per species

473

has the largest effect on a system (food web)

species with high linkage density

474

types of trophic pyramids

by numbers
by biomass
by energy

475

number trophic pyramids

how many individuals per trophic level- tertiary consumer is on top (1 consumer : 250 prey)
how many individuals are supported- top is biggest level, bottom is small (one tree maybe)

476

dominant species

a species with an effect on the community proportional to its biomass

477

umbrella species (indicator species)

species used for conservation decisions, supporting an umbrella species can save the ecosystem

478

examples of umbrella species

grizzly, panda, spotted owl, Garry oak

479

example of dominant species

cod

480

keystone species

a species with an effect on the community that is disproportional to its biomass or abundance