1. Concept 52.2: Interactions between organisms and the environment limit the distribution of species
Ecologists have long recognized global and regional patterns of distribution of organisms within the biosphere
Biogeography is a good starting point for understanding what limits geographic distribution of species
Ecologists recognize two kinds of factors that determine distribution: biotic, or living factors, and abiotic, or nonliving factors

2. Kangaroos/km2 0–0.1 0.1–1 1–5 5–10 10–20 > 20 Limits of
Fig. 52-5
Kangaroos/km2
0–0.1
0.1–1
1–5
5–10
10–20
> 20
Limits of
distribution
Figure 52.5 Distribution and abundance of the red kangaroo in Australia, based on aerial surveys

3. Ecologists consider multiple factors when attempting to explain the distribution of species

4. Figure 52.6 Flowchart of factors limiting geographic distribution
Why is species X absent
from an area?
Yes
Area inaccessible
or insufficient time
Yes
Does dispersal
limit its
distribution?
Habitat selection
Yes
Predation, parasitism,
competition, disease
Does behavior
limit its
distribution?
Chemical
factors No
Do biotic factors
(other species)
limit its
distribution?
Water
Oxygen
Salinity pH
Soil nutrients, etc. No
Do abiotic factors
limit its
distribution? No
Temperature
Light
Soil structure
Fire
Moisture, etc.
Physical
factors
Figure 52.6 Flowchart of factors limiting geographic distribution

5. Dispersal and Distribution
Dispersal is movement of individuals away from centers of high population density or from their area of origin
Dispersal contributes to global distribution of organisms

6. Natural Range Expansions
Natural range expansions show the influence of dispersal on distribution

7. Fig. 52-7
Current
1970
1966
1965
1960
1961
1958
1943
1937
1951
1956
Figure 52.7 Dispersal of the cattle egret in the Americas
1970

8. Species Transplants
Species transplants include organisms that are intentionally or accidentally relocated from their original distribution
Species transplants can disrupt the communities or ecosystems to which they have been introduced

9. Behavior and Habitat Selection
Some organisms do not occupy all of their potential range
Species distribution may be limited by habitat selection behavior

10. Biotic factors that affect the distribution of organisms may include:
Interactions with other species
Predation
Competition

11. August 1982 February 1983 August 1983 February 1984
Fig. 52-8
RESULTS
100
Both limpets and urchins
removed 80
Sea urchin
Only urchins
removed 60
Seaweed cover (%)
Limpet 40
Figure 52.8 Does feeding by sea urchins limit seaweed distribution?
Only limpets removed 20
Control (both urchins
and limpets present)
August
1982
February
1983
August
1983
February
1984

12. Abiotic factors affecting distribution of organisms include:
Temperature
Water
Sunlight
Wind
Rocks and soil
Most abiotic factors vary in space and time

13. Temperature
Environmental temperature is an important factor in distribution of organisms because of its effects on biological processes
Cells may freeze and rupture below 0°C, while most proteins denature above 45°C
Mammals and birds expend energy to regulate their internal temperature

14. Water
Water availability in habitats is another important factor in species distribution
Desert organisms exhibit adaptations for water conservation

15. Salinity
Salt concentration affects water balance of organisms through osmosis
Few terrestrial organisms are adapted to high-salinity habitats

16. Sunlight
Light intensity and quality affect photosynthesis
Water absorbs light, thus in aquatic environments most photosynthesis occurs near the surface
In deserts, high light levels increase temperature and can stress plants and animals

17. Fig. 52-9
Figure 52.9 Alpine tree

18. Rocks and Soil
Many characteristics of soil limit distribution of plants and thus the animals that feed upon them:
Physical structure pH
Mineral composition

19. Climate
Four major abiotic components of climate are temperature, water, sunlight, and wind
The long-term prevailing weather conditions in an area constitute its climate
Macroclimate consists of patterns on the global, regional, and local level
Microclimate consists of very fine patterns, such as those encountered by the community of organisms underneath a fallen log

20. Global Climate Patterns
Global climate patterns are determined largely by solar energy and the planet’s movement in space
Sunlight intensity plays a major part in determining the Earth’s climate patterns
More heat and light per unit of surface area reach the tropics than the high latitudes

21. Figure 52.10 Global climate patterns
Fig a
Latitudinal Variation in Sunlight Intensity
90ºN (North Pole)
60ºN
Low angle of incoming sunlight
30ºN
23.5ºN (Tropic of
Cancer)
Sun directly overhead at equinoxes
0º (equator)
23.5ºS (Tropic of
Capricorn)
30ºS
Low angle of incoming sunlight
60ºS
90ºS (South Pole)
Atmosphere
Seasonal Variation in Sunlight Intensity
60ºN
30ºN
March equinox
0º (equator)
June solstice
30ºS
Figure Global climate patterns
Constant tilt
of 23.5º
December solstice
September equinox

22. Low angle of incoming sunlight
Fig b
90ºN (North Pole)
60ºN
Low angle of incoming sunlight
30ºN
23.5ºN (Tropic of
Cancer)
Sun directly overhead at equinoxes
0º (equator)
23.5ºS (Tropic of
Capricorn)
30ºS
Figure Global climate patterns
Low angle of incoming sunlight
60ºS
90ºS (South Pole)
Atmosphere

23. Seasonal variations of light and temperature increase steadily toward the poles

24. 60ºN 30ºN March equinox 0º (equator) June solstice 30ºS
Fig c
60ºN
30ºN
March equinox
0º (equator)
June solstice
30ºS
Figure Global climate patterns
December solstice
Constant tilt
of 23.5º
September equinox

25. Global air circulation and precipitation patterns play major roles in determining climate patterns
Warm wet air flows from the tropics toward the poles

26. Global Air Circulation and Precipitation Patterns
Fig d
Global Air Circulation and Precipitation Patterns
60ºN
30ºN
Descending
dry air
absorbs
moisture
Descending
dry air
absorbs
moisture
0º (equator)
Ascending
moist air
releases
moisture
30ºS
60ºS
30º
23.5º 0º
23.5º
30º
Arid
zone
Tropics
Arid
zone
Global Wind Patterns
66.5ºN
(Arctic Circle)
60ºN
Westerlies
Figure Global climate patterns
30ºN
Northeast trades
Doldrums 0º
(equator)
Southeast trades
30ºS
Westerlies
60ºS
66.5ºS
(Antarctic Circle)

27. Arid zone Tropics Arid zone
Fig e
60ºN
Descending
dry air
absorbs
moisture
Descending
dry air
absorbs
moisture
30ºN 0º
(equator)
Ascending
moist air
releases
moisture
30ºS
60ºS
30º
23.5º 0º
23.5º
Figure Global climate patterns
30º
Arid
zone
Tropics
Arid
zone

28. Air flowing close to Earth’s surface creates predictable global wind patterns
Cooling trade winds blow from east to west in the tropics; prevailing westerlies blow from west to east in the temperate zones

29. 66.5ºN (Arctic Circle) 60ºN Westerlies 30ºN Northeast trades Doldrums
Fig f
66.5ºN
(Arctic Circle)
60ºN
Westerlies
30ºN
Northeast trades
Doldrums 0º
(equator)
Southeast trades
30ºS
Figure Global climate patterns
Westerlies
60ºS
66.5ºS
(Antarctic Circle)

30. Regional, Local, and Seasonal Effects on Climate
Proximity to bodies of water and topographic features contribute to local variations in climate
Seasonal variation also influences climate

31. Bodies of Water
The Gulf Stream carries warm water from the equator to the North Atlantic
Oceans and their currents and large lakes moderate the climate of nearby terrestrial environments

32. Labrador current Gulf stream Equator water Warm Cold water Fig. 52-11
Figure The great ocean conveyor belt
Cold water

33. During the day, air rises over warm land and draws a cool breeze from the water across the land
As the land cools at night, air rises over the warmer water and draws cooler air from land back over the water, which is replaced by warm air from offshore

34. Warm air over land rises.
Fig
Air cools at
high elevation. 2
Cooler
air sinks
over water. 3
Warm air
over land rises. 1
Cool air over water
moves inland, replacing
rising warm air over land. 4
Figure Moderating effects of a large body of water on climate

35. Mountains have a significant effect on
The amount of sunlight reaching an area
Local temperature
Rainfall
Rising air releases moisture on the windward side of a peak and creates a “rain shadow” as it absorbs moisture on the leeward side

36. Wind direction Mountain range
Fig
Leeward side
of mountain
Wind
direction
Mountain
range
Figure How mountains affect rainfall
Ocean

37. Seasonality
The angle of the sun leads to many seasonal changes in local environments
Lakes are sensitive to seasonal temperature change and experience seasonal turnover

38. Microclimate
Microclimate is determined by fine-scale differences in the environment that affect light and wind patterns

39. Long-Term Climate Change
Global climate change will profoundly affect the biosphere
One way to predict future global climate change is to study previous changes
As glaciers began retreating 16,000 years ago, tree distribution patterns changed
As climate changes, species that have difficulty dispersing may have smaller ranges or could become extinct

40. Current range Predicted range Overlap (a) 4.5ºC warming over
Fig
Current
range
Predicted
range
Figure Current range and predicted range for the American beech (Fagus grandifolia) under two scenarios of climate change
Overlap
(a) 4.5ºC warming over
next century
(b) 6.5ºC warming over
next century