50 lectures ppt

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 50
An Introduction to Ecology
and the Biosphere

Overview: Discovering Ecology
• Ecology is the scientific study of the interactions
between organisms and the environment
• These interactions determine distribution of
organisms and their abundance
• Modern ecology includes observation and
experimentation
© 2011 Pearson Education, Inc.

Figure 52.2
Global ecology
Landscape ecology
Ecosystem ecology
Community ecology
Population ecology
Organismal ecology

Global Ecology
• The biosphere is the global ecosystem, the sum
of all the planet’s ecosystems
• Global ecology examines the influence of
energy and materials on organisms across the
biosphere

Landscape Ecology
• A landscape or seascape is a mosaic of
connected ecosystems
• Landscape ecology focuses on the exchanges
of energy, materials, and organisms across
multiple ecosystems

Figure 52.2b
Landscape ecology

Ecosystem Ecology
• An ecosystem is the community of organisms
in an area and the physical factors with which
they interact
• Ecosystem ecology emphasizes energy flow
and chemical cycling among the various biotic
and abiotic components

Figure 52.2c
Ecosystem ecology

Community Ecology
• A community is a group of populations of
different species in an area
• Community ecology deals with the whole array
of interacting species in a community

Population Ecology
• A population is a group of individuals of the
same species living in an area
• Population ecology focuses on factors
affecting population size over time

Figure 52.2e
Population ecology

Organismal Ecology
• Organismal ecology studies how an organism’s
structure, physiology, and (for animals) behavior
meet environmental challenges
• Organismal ecology includes physiological,
evolutionary, and behavioral ecology

Figure 52.2f
Organismal ecology

Earth’s climate varies by latitude and season and is
changing rapidly
• The long-term prevailing weather conditions in an
area constitute its climate
• Four major abiotic components of climate are
temperature, precipitation, sunlight, and wind
• Macroclimate consists of patterns on the global,
regional, and landscape level
• Microclimate consists of very fine patterns, such
as those encountered by the community of
organisms underneath a fallen log

Global Climate Patterns
• Global climate patterns are determined largely
by solar energy and the planet’s movement in
space
• The warming effect of the sun causes
temperature variations, which drive evaporation
and the circulation of air and water
• This causes latitudinal variations in climate

Latitudinal Variation in Sunlight Intensity
• The angle at which sunlight hits Earth affects its
intensity, the amount of heat and light per unit of
surface area
• The intensity of sunlight it strongest in the
tropics (between 23.5° north latitude and 23.5°
south latitude)

Figure 52.3a
Latitudinal variation in sunlight intensity
90°N (North Pole)
60°N
30°N
23.5°N (Tropic of
Cancer
60°S
90°S (South Pole)
0° (Equator)
23.5°S (Tropic of
Capricorn)
30°S
Low angle of incoming sunlight
Atmosphere
Sun overhead at equinoxes
Low angle of incoming sunlight

Global Air Circulation and Precipitation
Patterns
• Global air circulation and precipitation patterns
play major roles in determining climate patterns
• Water evaporates in the tropics, and warm wet air
masses flow from the tropics toward the poles

• Rising air masses release water and cause high
precipitation, especially in the tropics
• Dry, descending air masses create arid climates,
especially near 30°
• 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

Figure 52.3b
Global air circulation and precipitation patterns
Westerlies
Northeast trades
Southeast trades
Westerlies
30°N
0°
ARID
ZONE
66.5°N (Arctic Circle)
30°N
0°
30°S
60°N
60°S
66.5°S (Antarctic Circle)
Descending
dry air
absorbs
moisture.
Ascending
moist air
releases
moisture.

Regional and Local Effects on Climate
• Climate is affected by seasonality, large bodies
of water, and mountains

Seasonality
• Seasonal variations of light and temperature
increase steadily toward the poles
• Seasonality at high latitudes is caused by the tilt
of Earth’s axis of rotation and its annual passage
around the sun
• Belts of wet and dry air straddling the equator
shift throughout the year with the changing angle
of the sun
• Changing wind patterns affect ocean currents

Figure 52.4
March equinox
December
solstice
September equinox
60°N
30°S
30°N
0° (equator)
Constant tilt
of 23.5°
June solstice

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

Figure 52.5
Indian
Ocean
Subtropical
Gyre
California Current
30°N North Pacific
Subtropical Gyre
30°S
Equator
South Pacific
Subtropical Gyre
Labrador Current
Gulf Stream
North Atlantic
Subtropical
Gyre
South
Atlantic
Subtropical
Gyre
Antarctic Circumpolar Current

• 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

Mountains
• Rising air releases moisture on the windward
side of a peak and creates a “rain shadow” as it
absorbs moisture on the leeward side
• Mountains affect the amount of sunlight reaching
an area
• In the Northern Hemisphere, south-facing slopes
receive more sunlight than north-facing slopes
• Every 1,000 m increase in elevation produces a
temperature drop of approximately 6°C

Figure 52.6
Air flow
Ocean
Mountain
range
Leeward side
of mountains

Interactions between organisms and the
environment limit the distribution of species
• Species distributions are the result of ecological
and evolutionary interactions through time
• Evolutionary time spans many generations and
captures adaptation through natural selection
• For example, Galápagos finches with larger
breaks were more likely to survive a drought as
they could eat the available larger seeds
• As a result, the average beak size was larger in
the next generation

• Both biotic and abiotic factors influence species
distribution
– For example, climate, interspecific interactions,
and other factors affect the distribution of the
red kangaroo

Kangaroos/km2
0–0.1
0.1–1
1–5
5–10
10–20
> 20
Limits of
distribution
Figure 52.17

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

Biotic Factors
• Biotic factors that affect the distribution of
organisms may include
– Predation
– Herbivory
• For example, sea urchins can limit the
distribution of seaweeds
– Competition

Both limpets and urchins
removed
Only urchins
removed
RESULTS
Seaweedcover(%)
Only limpets removed
Control (both urchins
and limpets present)
Sea urchin
Limpet
100
80
60
40
20
0
February
1983
August
1983
August
1982
February
1984
Figure 52.20

Abiotic Factors
• Abiotic factors affecting distribution of organisms
include
– Temperature
– Water
– Sunlight
– Wind
– Rocks and soil
• Most abiotic factors vary in space and time

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

Water and Oxygen
• Water availability in habitats is another important
factor in species distribution
• Desert organisms exhibit adaptations for water
conservation
• Water affects oxygen availability as oxygen
diffuses slowly in water
• Oxygen concentrations can be low in deep
oceans and deep lakes

Salinity
• Salt concentration affects water balance of
organisms through osmosis
• Most aquatic organisms are restricted to
either freshwater or saltwater habitats
• Few terrestrial organisms are adapted to high-
salinity habitats

Sunlight
• Light intensity and quality (wavelength) 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

Figure 52.21
Organisms at high elevation are exposed to high UV radiation, freezing temperatures,
moisture deficits, and strong winds that restrict the growth and survival of trees.

Rocks and Soil
• Many characteristics of soil limit distribution of
plants and thus the animals that feed on them
– Physical structure
– pH
– Mineral composition

Why is species X absent from an area?
Does dispersal limit its distribution?
Does behavior limit its distribution?
Do biotic factors (other species)
limit its distribution?
Do abiotic factors limit
its distribution?
No
No
No
Yes
Yes
Yes
Physical
factors
Chemical
factors
Area inaccessible or
insufficient time
Habitat selection
Predation, parasitism,
competition, disease
Temperature, light, soil
structure, fire, moisture,
etc.
Water, oxygen, salinity,
pH, soil nutrients, etc.
Figure 52.UN01

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