I. Concept 52.2: Interactions between organisms and the environment limit the
distribution of species
a. Ecologists have long recognized global and regional patterns of
distribution of organisms within the biosphere
b. Biogeography is a good starting point for understanding what limits
geographic distribution of species
c. Ecologists recognize two kinds of factors that determine distribution:
________________________, or living factors, and ________________________, or
nonliving factors
d. Ecologists consider multiple factors when attempting to explain the
distribution of species
i. Dispersal is movement of individuals away from centers of
________________________________________________or from their area of
origin
1. Dispersal contributes to global distribution of
organisms
e. Natural range expansions show the influence of dispersal on
distribution
f. Species ________________________include organisms that are intentionally
or accidentally relocated from their original distribution
i. Species transplants can disrupt the communities or ecosystems
to which they have been introduced
g. Some organisms do not occupy all of their potential range
h. Species distribution may be limited by habitat selection behavior
i. Biotic factors that affect the distribution of organisms may include:
i. Interactions with other species
ii. Predation
iii. ________________________
iv. Abiotic Factors
1. ________________________
2. Water
3. Sunlight
j.
4. ________________________
5. Rocks and soil
a. Most abiotic factors vary in space and time
Environmental temperature is an important factor in distribution of
organisms because of its effects on biological processes
i. Cells may freeze and rupture below 0°C, while most proteins
________________________above 45°C
ii. Mammals and birds expend energy to regulate their internal
temperature
k. Water availability in habitats is another important factor in species
distribution
i. Desert organisms exhibit adaptations for water conservation
l. Salt concentration affects water balance of organisms through
________________________
i. Few terrestrial organisms are adapted to high-salinity habitats
m. Light intensity and quality affect photosynthesis
i. Water absorbs light, thus in aquatic environments most
photosynthesis occurs ______________________________________________
ii. In deserts, high light levels increase temperature and can
stress plants and animals
n. Many characteristics of soil limit distribution of plants and thus the
animals that feed upon them:
i.
ii.
iii.
iv.
________________________________________________
pH
Mineral composition
Climate
1. Four major abiotic components of ________________________
are temperature, water, sunlight, and wind
a. The long-term prevailing weather conditions in
an area constitute its climate
2. Macroclimate consists of patterns on the global,
regional, and local level
3. ________________________consists of very fine patterns, such
as those encountered by the community of organisms
underneath a fallen log
o. Global climate patterns are determined largely by solar energy and
the planet’s movement in space
p. Sunlight intensity plays a major part in determining the Earth’s
climate patterns
i. More heat and light per unit of surface area reach the tropics
than the high latitudes
ii. Seasonal variations of light and temperature increase steadily
toward the poles
iii. Global air circulation and precipitation patterns play major
roles in determining climate patterns
1. Warm wet air flows from the tropics toward the poles
2. Air flowing close to Earth’s surface creates predictable
global wind patterns
q.
r.
s.
t.
u.
v.
3. Cooling trade winds blow from east to west in the
tropics; prevailing westerlies blow from west to east in
the temperate zones
Proximity to bodies of water and topographic features contribute to
local variations in climate
Seasonal variation also influences climate
The Gulf Stream carries warm water from the equator to the North
Atlantic
i. Oceans and their currents and large lakes moderate the climate
of nearby terrestrial environments
ii. During the day, air rises over warm land and draws a cool
breeze from the water across the land
iii. 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
Mountains have a significant effect on
i. The amount of sunlight reaching an area
1. Local temperature
2. Rainfall
3. Rising air releases moisture on the windward side of a
peak and creates a “rain shadow” as it absorbs moisture
on the leeward side
The angle of the sun leads to many seasonal changes in local
environments
i. Lakes are sensitive to seasonal temperature change and
experience seasonal turnover
ii. Microclimate is determined by fine-scale differences in the
environment that affect light and wind patterns
Global climate change will profoundly affect the biosphere
i. One way to predict future global climate change is to study
previous changes
1. As glaciers began retreating 16,000 years ago, tree
distribution patterns changed
2. As climate changes, species that have difficulty
dispersing may have smaller ranges or could become
extinct
Lecture Questions
52.2 Interactions between Organisms and the Environment Limit the Distribution of Species
1. Explain how dispersal may contribute to a species’ distribution.
2. Describe, with examples, how biotic and abiotic factors may affect the
distribution of organisms.
3. Describe how an ecologist might predict the effect of global warming on
distribution of a tree species.