BIOGEOGRAPHY
Dr. Matthew G. Letts
Department of Geography
University of Lethbridge
THE NATURE OF
BIOGEOGRAPHY
BIOGEOGRAPHY
The study of past and
present geographic
distributions of plants,
animals and other
organisms.
Integrates the Four
Spheres of Geography
and Environmental
Science, as well as the
anthropogenic influence
THE FOUR SPHERES
OF GEOGRAPHY
LEVELS OF
ORGANIZATION
Levels of Organization
BIOSPHERE
ECOSYSTEM
COMMUNITY
POPULATION
INDIVIDUAL
COMMUNITIES
Habitat
The type of environment in
which a species resides
Niche
The role or functional position
of a species within the
community of an ecosystem.
Competition
The intraspecific or interspecific relationship that occurs when
commodities are scarce (nutrition, moisture, shelter, mates)
Trophic levels
Levels through which
energy flows from its
initial capture until its
dissipation
Autotrophs are the
foundation of
the trophic hierarchy
(phototrophs and
chemotrophs)
AUTOTROPHS
PHOTOSYNTHESIS
6CO2 + 6H2O + sunlight  C6H12O6 + 6O2
A LEAF IN CROSS-SECTION
cuticle
upper epidermis
palisade mesophyll
spongy mesophyll
lower epidermis
stomate
H20
CO2
Stomata open to maintain internal
CO2 concentrations (ci) during photosynthesis.
Transpiration (E): H20 is lost during this process.
C3 Pathway
C4 Pathway
Crassulacean
Acid Metabolism
CO2 converted to
3-phosphoglyceric
acid
CO2 converted to
4-C malic and
aspartic acid
CO2 absorbed at
night; C3 in day.
Photosynthetic light-response curve
Photosynthesis (mol CO2 m-2 s-1)
20
LIGHT-SATURATION
2400
PPF (mol m-2 s-1)
Lethbridge Ecosystem Flux Site
(PI = Larry Flanagan, Biological Sciences)
CO2 rich
Dry, Cool
Low CO2
Humid, Warm
NEE (mol CO2 m-2 s-1)
Net Ecosystem Exchange of Carbon =
Photosynthesis - Respiration
8
4
CO2 SOURCE
0
-4 0
CO2 SINK
1000
2000
-8
-12
Photosynthetic Photon Flux
(mol m-2 s-1)
Peatland Data from Letts, Lafleur & Roulet (2005)
Source: Dr. Larry Flanagan
HETEROTROPHS
Heterotrophs
• obtain their energy either directly or indirectly
from autotrophs
• energy loss occurs at each level
HERBIVORE
DECOMPOSER
CARNIVORE
FOOD WEBS
Food Web
low trophic level
high trophic level
Bioaccumulation and Biomagnification
of Persistent Organic Pollutants
PCB biomagnification
In the food chain of Great
Lakes herring gulls