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Chapter 50
Introduction to Ecology and
the Biosphere
I. Study of Interactions
Ecology and evolutionary biology
Abiotic/Biotic factors
Subfields
– Organism -> population -> community ->
ecosystem -> landscape -> biosphere
Environmental Issues
LE 50-2
Kangaroos/km2
> 20
10–20
5–10
1–5
0.1–1
< 0.1
Limits of
distribution
Tasmania
LE 50-3
Organismal
ecology
Population
ecology
Community
ecology
Landscape ecology
Ecosystem ecology
II. Limits to Distribution
Biogeographic realms – continental drift
Dispersal and distribution
Behavior and Habitat selection
Biotic factors
Abiotic factors
Climate
LE 50-5
Palearctic
Nearctic
Tropic
of Cancer
(23.5°N)
Oriental
Ethiopian
Equator
Neotropical
(23.5°S)
Tropic of
Capricorn
Australian
LE 50-6
Species absent
because
Yes Area inaccessible
or insufficient time
Dispersal
limits
distribution?
No
Behavior
limits
distribution?
Yes
No
Habitat selection
Biotic factors
(other species)
limit
distribution?
Yes Predation, parasitism,
Chemical
competition, disease factors
Water
Oxygen
Abiotic factors
Salinity
No
limit
pH
distribution?
Soil nutrients, etc.
Temperature
Physical Light
factors Soil structure
Fire
Moisture, etc.
LE 50-8
100
Sea
urchin
Seaweed cover (%)
80
Both limpets
and urchins
removed
Only
urchins
removed
60
Limpet
40
Only limpets removed
Control (both
urchins and
limpets present)
20
0
August
1982
February
1983
August
1983
February
1984
LE 50-10a
North Pole
60°N
Low angle of incoming sunlight
30°N
Tropic of
Cancer
Sunlight directly overhead at equinoxes
0° (equator)
Tropic of
Capricorn
30°S
Low angle of incoming sunlight
60°S
South Pole
Atmosphere
LE 50-10b
60°N
30°N
June solstice:
Northern Hemisphere
tilts toward sun;
summer begins in
Northern Hemisphere;
winter begins in
Southern
Hemisphere.
0° (equator)
March equinox: Equator faces sun
directly; neither pole tilts toward sun;
all regions on Earth experience 12
hours of daylight and 12 hours of
darkness.
30°S
Constant tilt
of 23.5°
September equinox: Equator faces
sun directly; neither pole tilts
toward sun; all regions on Earth
experience 12 hours of daylight and
12 hours of darkness.
December solstice:
Northern Hemisphere tilts
away from sun; winter
begins in Northern
Hemisphere; summer
begins in Southern
Hemisphere.
LE 50-10c
60°N
30°N
Descending
dry air
absorbs
moisture
0° (equator)
30°S
Ascending
moist air
releases
moisture
Descending
dry air
absorbs
moisture
0°
60°S
Arid
zone
Tropics
Arid
zone
LE 50-10d
Arctic
Circle
60°N
Westerlies
30°N
Northeast trades
Doldrums
Southeast trades
0°
(equator)
30°S
Westerlies
60°S
Antarctic
Circle
III. Aquatic Biomes
Freshwater vs. Marine
Zones
– Photic
– Aphotic
– Benthic
Distribution factors
–
–
–
–
Thermocline
Light penitration
Distance from shore
Open water vs. Bottom
Lake depth (m)
0
4
Spring
Winter
O2 (mg/L)
8
12
8
16
2°
4°
4°
4°
4°C
24
O2 concentration
0°
4°
4°
Lake depth (m)
LE 50-13
O2 (mg/L)
0
4
8
12
8
12
8
16
24
4°
4°
4°
4°C
High (>8 mg/L)
Medium (4–8 mg/L)
O2 (mg/L)
0
4
8
12
8
4°
4°
22°
20°
18°
8°
6°
5°
4°C
4°
4°
4°
4°C
16
24
Autumn
Thermocline
Summer
Lake depth (m)
Lake depth (m)
Low (<4 mg/L)
O2 (mg/L)
0
8
16
24
4
IV. Terrestrial Biomes
Climate and climograph
Vertical stratification
Ecotone
LE 50-18
Desert
Temperate grassland
Tropical forest
30
Temperate
broadleaf
forest
15
Coniferous
forest
0
Arctic and
alpine
tundra
–15
100
200
300
Annual mean precipitation (cm)
400
LE 50-19
30°N
Tropic of
Cancer
Equator
Tropic of
Capricorn
30°S
Key
Tropical forest
Savanna
Desert
Chaparral
Temperate grassland
Temperate broadleaf forest
Coniferous forest
Tundra
High mountains
Polar ice