UBC Bio 111 - Intro to Biology

1. 3.2 Communities of Species and their Distribution
Learning Outcomes:
4. Define the composition of biological communities
5. Describe the effect of changing abiotic factors on the regional or geographic distribution of species.
Reminders: Assignment #1 Digital Collection Due Now.
Deadline to do the Welcome Survey Due before class today
Late assignments policy: -10% per day including weekends. Eg. -10% if the assignment comes in between the time
that class has started (12pm) today until 12pm Thursday. -20% if the assignment comes in between 12:01pm
Thursday and 12pm Friday…..etc…..
Natural Communities:
Marsh alpine forestmeadow desert
Community = all populations of organisms living close enough together in a particular environment to
potentially interact
Plants give communities their structure but animals, fungi, protists, bacteria are also members of a community
(Communities are often named after dominating plants)
What affects community structure?
Global gradients of abiotic factors: (Fig 15.8) “Our weather comes from the west”. Your textbook
explains that this is partially due to the direction of the
rotation of the earth. We can observe that moisture-laden
air tends to come off the Pacific towards Vancouver.
THOUGHT EXPERIMENT:
Imagine Dr. Evil came up with a
way to reverse the rotation of the
Earth. The sun would now rise in
the West and set in the East.
1. In the long term, with the
earth’s rotation changed, what
region might come to resemble
Vancouver in terms of weather
and climate? And what might be
the new climatic conditions of
Vancouver?

2. Climatic regions of the world (biomes) (Fig 15.9): Vancouver lies within
temperate forest according
to the map. To be more
specific it is temperate
rainforest. There are only 7
other regions of temperate
rainforest in the world:
-beside the Caspian sea
(Iran), -beside the Black sea
(Turkey and Georgia),
southwestern S. America, a
region of coastal South
Africa, New Zealand and
Tasmania, SW Japan, small
regions of NW Europe.
QUESTION: 2. What is
common to all regions
besides rain? (Name two
things).
Climatic regions of British Columbia:
Taken from the Tree Book:
http://www.for.gov.bc.ca/hfd/library/documents/treebook/biogeo/biogeo.htm
Biological communities correlate with substratum (types of soils) and climate.
Recognizable differences in plant communities were used to classify communities according to
dominant tree species.
QUESTION: 3. What biogeoclimatic zone to you suspect Kamloops to be in based on what you
learned last class? (Hint: What type of trees are affected severely by mountain pine beetle,
Dendroctonus ponderosae?)
Climate change in British Columbia: http://www.geog.ubc.ca/courses/geog376/students/class05/
skcurtis/

3. The Boreal Forest Community:
Covers 17% of earth’s land surface (300 million ha in Canada, 1.43 billion ha global
-carbon sink 714 billion tonnes of carbon (37% of carbon stored in terrestrial biosphere)
QUESTIONS:
4. How can the carbon stored in trees be returned to the atmosphere? There are several important ways.
5. This community depends on disturbance for renewal. What are two types of disturbances you can think of
which usually occur every 50-100 yrs?
Climate change will cause changes in precipitation, species composition, disturbance
The boreal forest will be more severely affected than tropical or temperate forests.
It has been predicted by IPCC that the frequency and pattern of disturbance may be more important than
increased temperature and CO2
Due to warmer temperatures the boreal forest is moving northward encroaching on the tundra biome but due
to the magnitude of climate change the overall prediction is this biome will decrease in area, biomass, and
amount of carbon stored.
Local Communities reflect gradients of abiotic factors:
Elevation:

4. Differences in precipitation and wind: (similar to Fig. 15.1)
Question: 6. What are some other local examples of abiotic gradients causing variation in communities?
-most aggressive, determines the upper limit of the
yellow pine chipmunk and the lower limit of the
alpine chipmunk
-requires shaded forest because it is vulnerable to
heat stress
-aggressive, determines the upper limit of the least
chipmunk (ie if yellow pine chipmunk is gone then
least chipmunk will move in)
-if least chipmunk gone it does not move into
Sagebrush
-can tolerate all environments
and better than others at
handling heat stress such as
in the Sagebrush
QUESTIONS:
7. If all other chipmunks were gone where would the lodgepole pine chipmunk live?
8. What do you need to know in order to determine where the alpine chipmunk would live if the lodgepole
pine chipmunk were gone?

5. 9. In addition to tolerating the abiotic conditions in a particular environment, what biotic conditions must be
met besides outcompeting other species? (Biotic interactions involve an organism interacting in some way with
other living organisms)
10. Considering what the abiotic conditions must be like in the alpine zone in the winter, what do you predict
the alpine chipmunk does to survive?
TOUGH QUESTION TO CONSIDER:
The ambitious 10 year long Manahatta project http://themannahattaproject.org/
(on the cover of this month’s National Geographic magazine) reconstructs what the natural habitat of
Manhattan (New York City) was like before the arrival of man. There were once 55 different ecosystems there.
How do you think they determined what organisms used to live there?