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Lecture 16

Biology 2483A Lecture Notes - Lecture 16: Bryozoa, Thatching, Tunicate

Course Code
BIOL 2483A
Hugh Henry

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Unit 5: Communities Lesson 16: Change in Communities (Nov. 7th 2017)
Agents of change act on communities across all temporal and spatial scales:
Temporal scale (time) thousands of years, could also be quick.
Spatial scale space over where it happens.
Abiotic agents of change:
o Mt. St. Helen in 10 mins within 23km was wiped out.
o Increases in sea level
o Warmer temperatures
o Pollution
o Reduced light availability
o Fires
o Floods
o Wind/rain/snow storms
o Volcanic activity
Biotic agents of change:
o Competition
o Mutualism/symbiosis
o Predation/herbivory
o Foundation species
o Keystone species
o Disease/parasitism
o Digging/burrowing
o Trampling
Interactions among abiotic and biotic agents:
o Ecosystem engineers (coral and beaver)
o Stressful environments (Eel River in Cali).
Main flow of energy in winter with ample water, producers insects big
If drought, the abiotic factor causes a shift so that energy from producers go to
the armored insect larvae.
May cause only two trophic levels.
Disturbance an event that directly physically injures or kills some individuals and creates
opportunities for other individuals.
o Can be biotic (grazing, trampling, logging) or abiotic (fires, avalanche).
Stress a factor that reduces the rate of an important physiological process, thereby reducing
growth, reproduction or survival of some individuals.
o Does’t usually outright kill a aial ut ould prologed.
o Drought, unusual cold temperature, pollution, flooding (abiotic).
o Disease or parasite (biotic).
Agents of change vary in their intensity, frequency and extent:
o Intensity (severity) is proportional to the amount of damage or death caused.
High lots of change
o Frequency is a measure of how often the agent of change has an effect.
Low change, high nothing lives there.
o Extent is proportional to the area of land or number of individuals affected
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