lec 18 Flashcards Preview

Bio 121 > lec 18 > Flashcards

Flashcards in lec 18 Deck (19)
Loading flashcards...

Tolerance model: _________
later successional stage species can ________
become ________
independent of
modification of environment has little to do with ______
early species are eliminated through

species in earlier successional stager neither aid nor inhibit later successional species
- can invade a newly exposed site,
- established and reach maturity
- the species that come before or after
- subsequent recruitment of later successional spp.
- competition for resources


Two factors that impact divesity in relation to succession

1. time
2. frequency of disturbance


frequency of disturbance

can also impact diversity by resetting succession


if an area is frequently re-disturbed

pioneering species will never give way to climax species
- with each disturbance succession starts again


when eastern N.A. was first colonized by europeans
American aboriginals did
Europeans cleared forests on a

- forest dominated the landscape
- use fire to clear areas for crops or to make habitat for game species but had a minimal impacts
- much larger scale for agricultural and forest products


Dust Bowl period

during the 1930s, was the beginning of the decline in small family farms in agricultural areas west of the mississippi


rise of large-scale agriculture in the west hastened _____
resulting in a pattern of ________ in the eastern united states on a ________
(_________ to ________ to ________)

- agricultural decline the east
- secondary succession
- regional scale
- agricultural lands to old fields to forests


succesion and siturbance

plant and animal populations that depend on forest increased (succession towards its original state
- however, this trend began to reverse
- from 1973 to 2000, there was a decline of 4.1 percent in forest area in the eastern u.s.
- forestes were being harvested, some are being converted to pine plantations
- urban areas was expanding
- this trend in now reversing


Like many areas in biology the study of succesion

has been diverted to conservation and the meditation of human impacts
- key area of study is the loss of lcimax communities around the globe
- these communites tak the longest to recover and due to emerging threats may not recover to their original state


Facilitation model: ___________
Only certain species can ________
So you must start with these species because ________
Early species are eliminated through ________
This sequence continues until ____________

- early successional species invade an environment making it more suitable for later successional species to invade and grow
- establish
- habitat is not suitable for later species
- competition for resources by later arrivals
- the current residents no longer facilitate invasion and growth of next species


Inhibition model: ____________
No species is completely
These species maintain position as long as ___________
and can only be replaced if _________
by early occupants,
makes __________
for _______
_____ are held back by _______

- involves strong competitive interactions
- superior to another
- it lives and reproduces
- it is injured or dies
- modification of the environment
- less suitable
- recruitment of later successional species
- climax species
- pioneer species


transition period: ______
The rate of displacement is influenced by ____

- climax species have arrived but transition species have not yet been replaced
- The growth rates of the species involved in succession (if the growth rate of competitors to successional species is slow then the rate of coexistence is extended)


Intermediate disturbance hypothesis

highest species diversity is seen at intermediate frequencies of disturbance


The occurrence and distribution of animals in succession directly correlates to ___________
- as this community undergoes succession the changes in ________________ affects all animals
- as the ____________ and __________ change, animals can gain or lose habitat
- complexity of the _________ increases through succession

- the plant community
- the structure and composition of the vegetation
- species composition
- structure of vegetation
- vertical structure


changes in the earths history have affected the ____
in turn affecting the _________

climate and environmental conditions
distribution and abundance of species


At glacial maximum ice covered

30% of the earths surface


The north american ice sheet reached maximum size about ____________

18,000 years ago


a band of tundra bordered the

ice sheet boreal forest areas covered to the south


By 8000 years ago ice was restricted to _______
pollen from tree species settled into _________
__________ can be used to map the northward advances of different genera of trees
By present day the result was ______

- restricted to northern Canada
- lake sediments
- cores from these sediments
- essentially a mixed hardwood community, or traditional climax community