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GENERAL ECOLOGY - CHAPTER 50
I. The Scope of Ecology
Ecology These interactions determine
II. Organisms and the Environment
A. Short-term (ecological time) interactions of organisms with their environments
could have long-term (evolutionary time) effects through natural selection.
1. Example:
2. The current distribution and abundance of organisms
B. The environment of an organism includes biotic and abiotic factors.
1. Biotic components –
2. Abiotic components –
3. Interactions between organisms and their environments include
a. About three billion years ago, photosynthetic bacteria began to use sunlight for
energy.
• Oxygen, a by-product of photosynthesis, accumulated and resulted in our aerobic
atmosphere.
b. Mature trees shade the forest floor, and this may make the floor unsuitable for
their offspring to grow due to reduced light.
C. Ecology can be divided into five increasingly comprehensive levels of inquiry:
Ecological research ranges from the adaptations of organisms to the dynamics of
ecosystems
1. Organismal ecology -
• Distribution is limited by a species tolerance of abiotic conditions.
2. Population ecology • Questions concern factors that affect population size and composition
3. Community ecology • Questions concern predation, competition, disease, and other ways in which
interactions among organisms affect community structure and organization
4. Ecosystem ecology • Questions concern energy flow and chemical cycling among the abiotic and biotic
components
5. Landscape ecology –
• Questions concern exchanges of energy, materials and organisms between the
ecosystems.
The biosphere is the global ecosystem - the sum of all Earth’s ecosystems. It is a
thin layer consisting of the atmosphere to an altitude of a few kilometers; the land
down to and including water-bearing rocks at least 1500 meters below ground, lakes
and streams, caves; and the oceans to a depth of several kilometers.
Ecological study is multidisciplinary in nature, encompassing genetics, evolution,
physiology, behavior, chemistry, physics, geology, and meteorology.
D. Ecology: a scientific context for evaluating environmental issues
Although distinct, basic ecology and environmental issues have many connections.
1. To properly address environmental problems,
2. Current environmental awareness began with Rachel Carson’s 1962 book Silent
Spring,
The Earth is a finite resource. It is of concern to most of us that pollution,
overpopulation, and habitat destruction are threatening that resource.
III. Interactions between organisms and the environment limit the distribution of
species
There are distinct global and regional patterns of distribution of organisms within
the biosphere.
The six broadly identified biogeographic realms:
Biogeography
A. Dispersion and distribution
Dispersal is the movement of individuals away from centers of high population
density or from their area of origin. Dispersal contributes to the global distribution
of organisms
1. Natural range expansions
2. Species transplants
a.
b.
B. Behavior and Habitat selection
1. Some organisms
2. Species distribution
C. Biotic factors affect the distribution of organisms
These are interactions with other species
1.
2.
3.
A specific case of an herbivore limiting distribution of a food species
(Figure 50.8)
III. Climate and other abiotic factors are important determinants of the biosphere’s
distribution of organisms
Global and regional patterns reflect differences in climate and other abiotic factors.
Different physical environments can produce a patchy mosaic of habitats.
A. Major abiotic factors
Some of the important abiotic factors that affect distribution of species include:
temperature, water, sunlight, wind, rocks and soil, and periodic disturbances.
1. Temperature
Environmental temperature affects biological processes and body temperature.
a. Most organisms
b. Temperature greatly affects metabolism:
c. The actual body temperature of ectotherms
d. Most animals
e. Even endotherms
2. Water
Water is essential for life. Adaptations that allow organisms’ to conserve and
balance water help determine a species' habitat range.
a. Marine and freshwater animals
b. Terrestrial animals
3. Sunlight
Sunlight provides the energy that drives nearly all ecosystems, though only
photosynthetic organisms use it directly as an energy source.
a. Light
b. In aquatic environments, the distribution of photosynthetic organisms is limited by
the intensity and quality of light.
•
c. The physiology, development, and behavior of many animals and plants are often
sensitive to photoperiod.
4. Wind
a. Wind
b.
c. Mechanical pressure
5. Rocks and soil
The physical structure, pH, and mineral composition of soil determine distribution
of plants and also of animals that feed on them.
a. The composition of the substrate
b. The type of substrate
6. Periodic disturbances
Catastrophic disturbances such as fire, major storms, and volcanic eruptions can
devastate biological communities.
a. After the disturbance,
b. Those disturbances that are infrequent
c. Adaptations
B. Climate has a major impact on the distribution of organisms
1. Climate:
•
2. A climatograph –
a.
b. Biomes c. Biomes overlap on climatographs.
C. Global climate patterns explain the geographical distribution of biomes
1. Solar energy input and the Earth's movement in space determine the planet's
global climate patterns.
2. The atmosphere, land, and water are heated when they absorb solar energy.
3. Latitudinal variation in intensity of sunlight results from Earth's spherical shape
–
a. Only the tropics (23.5°N to 23.5°S) receive sunlight from directly overhead year
round.
b. Seasonal variation in light and temperature increases steadily toward the poles;
4. A global circulation of air that creates precipitation and winds results from
intense solar radiation near the equator (Figure 50.6).
a. Evaporation of surface water due to high tropical temperatures –
b. As these warm air masses rise,
c. The cool, dry air masses flow
d. Air mass density increases
e. The air masses absorb water
f. Some of the descending air masses
g. The air flowing toward the poles is warmed and rises again
h. As air from this third cell reaches the higher altitude
D. Local and seasonal effects on climate create regional patchiness in climatic
conditions
Regional and local variations in climate and soil have a major influence on less
widely distributed communities and individual species.
1. Proximity of large bodies of water affect local climates.
a. Ocean currents
b. Coastal areas
c. During warm summer days,
2. Topographical variations, such as mountains, also exert an influence on solar
radiation, local temperature and rainfall.
a. In the Northern Hemisphere,
• The vegetation differs
b. Air temperature declines
i. This parallels the decline in temperature
ii. For this reason, mountain communities
c. When warm, moist air moves over a mountain, it cools with increasing altitude;
i. The cooler, drier air
ii. Deserts 3. Climate also varies on a smaller scale, the microclimate. Microclimate refers to
small areas in a habitat that may have different conditions than the overall area
(under a rock, the forest floor, etc.).
a. Cleared areas in a forest –
b. Low-lying areas –
c. The area under a large stone or log -