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CH 46
(OLD BOOK)
Principles of
Ecology
Chapter 50
New Book
An Introduction to Ecology
and the Biosphere
Overview: The Scope of Ecology
• Ecology is the scientific study of the interactions
between organisms and the environment
• These interactions determine distribution of
organisms and their abundance
• Ecology reveals the richness of the biosphere
• The biosphere is the global ecosystem, the sum
of all the planet’s ecosystems
Organisms and the Environment
• The environment of any organism includes:
– Abiotic, or nonliving, components
– Biotic, or living, components
• All the organisms that are part of the
individual’s environment are collectively called
the biota
• Environmental components affect the
distribution and abundance of organisms
LE 50-2
Kangaroos/km2
> 20
10–20
5–10
1–5
0.1–1
< 0.1
Limits of
distribution
Tasmania
• Ecologists use observations and experiments to
test explanations for the distribution and
abundance of species
• Levels of organization in the biosphere:
Species populationcommunityecosystembiomebiosphere
• Two types of research (ways of collecting data):
– Qualitative ( a.k.a. descriptive)
– Quantitative
Subfields of Ecology
• Organismal ecology studies how an organism’s
structure, physiology, and (for animals) behavior
meet environmental challenges
LE 50-3a
Organismal ecology
• Population ecology focuses on factors affecting
how many individuals of a species live in an area
Population ecology
• Community ecology deals with the whole array
of interacting species in a community
Community ecology
• Ecosystem ecology emphasizes energy flow and
chemical cycling among the various biotic and
abiotic components
Ecosystem ecology
• Landscape ecology deals with arrays of
ecosystems and how they are arranged in a
geographic region
Landscape ecology
Ecology and Environmental Issues
• Ecology provides the scientific understanding
underlying environmental issues
• Rachel Carson is credited with starting the
modern environmental movement
• Her book Silent Spring (1962) brought to the
forefront the concerns of widespread pesticide
use and the degradation of the environment
• It states that humans need to be concerned
with how their actions affect the environment
LE 50-6
Species absent
because
Yes
Dispersal
limits
distribution?
No
Area inaccessible
or insufficient time
Behavior
limits
distribution?
Yes
No
Habitat selection
Biotic factors
(other species)
limit
distribution?
Yes
No
Predation, parasitism,
competition, disease
Chemical
factors
Abiotic factors
limit
distribution?
Water
Oxygen
Salinity
pH
Soil nutrients, etc.
Temperature
Physical Light
factors Soil structure
Fire
Moisture, etc.
Biogeography is a good starting point for
understanding what limits geographic
distribution of species
Natural Range Expansions
• Natural range expansions show the influence of
dispersal on distribution
LE 50-7
Spread of breeding grounds of the great-tailed grackle.
New areas
occupied Year
1996
1989
1974
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
• Examples of exotic or non-native invasive
species:
– Purple loosestrife
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:
– Interactions with other species
– Predation
– Competition
Does feeding by sea urchins or limpets affect sea weed distribution?
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
Abiotic Factors
• Abiotic factors affecting distribution of
organisms:
– Temperature
– Water
– Sunlight
– Wind
– Rocks and soil
What factor influenced the growth of this tree?
Rocks and Soil
• Many characteristics of soil limit distribution of
plants and thus the animals that feed upon
them:
– Physical structure (rocky, sandy, thin layer, etc.)
– pH
– Mineral composition
Climate
• Four major abiotic components of climate:
temperature, water, sunlight, and wind
• Climate is the prevailing weather in an area
• 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
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
• Seasonal variations of light and temperature
increase steadily toward the poles
The Earth’s curved shape causes latitudinal variations in the intensity of sunlight.
Where is the most heat and light uniformly delivered?
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
Seasonal variation in sunlight.
60°N
30°N
June solstice: Northern
Hemisphere tilts toward
sun; summer begins in
Northern Hemisphere;
winter begins in
Southern Hemisphere.
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.
0° (equator)
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.
Global air circulation and wind patterns play major roles
in determining climate patterns
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
Regional, Local, and Seasonal Effects on
Climate
• Various features of the landscape contribute to
local variations in climate
• Seasonal variation also influences climate
Bodies of Water
• Oceans and their currents and large lakes
moderate the climate of nearby terrestrial
environments
Air cools at high elevation.
Warm air over land
rises.
Cooler air sinks
over ocean.
Cool air over water
moves inland,
replacing rising
warm air over land.
Mountains
• Mountains have a significant effect on
– The amount of sunlight reaching an area
– Local temperature
– Rainfall
Moist air from
ocean
Rain shadow,
Very dry (arid)
Wind
direction
Pacific
Ocean
East
Deep snow packs.
Redwood forests
Coast
Range
Sierra
Nevada
Desert
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
LE 50-13
4
8
O2 (mg/L)
12
8
16
2°
24
0°
4°
4°
4°
4°C
O2 concentration
4°
4°
Lake depth (m)
Lake depth (m)
0
Spring
Winter
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)
Low (<4 mg/L)
O2 (mg/L)
0
4
8
12
8
4°
4°
20°
18°
8°
6°
5°
4°C
4°
4°
4°
4°C
16
24
Autumn
Thermocline
22°
Summer
Lake depth (m)
Lake depth (m)
O2 (mg/L)
0
8
16
24
4
Abiotic and biotic factors influence the
structure and dynamics of aquatic
biomes
• Varying combinations of biotic and abiotic factors
determine the nature of biomes
• Biomes are the major ecological associations that
occupy broad geographic regions of land or water
• Aquatic biomes account for the largest part of
the biosphere in terms of area
• They can contain fresh water or salt water
• Oceans cover about 75% of Earth’s surface and
have an enormous impact on the biosphere
• Many aquatic biomes are stratified into zones or
layers defined by light penetration,
temperature, and depth
• Know these zones!
LE 50-16a
Littoral
zone
Limnetic
zone
Photic
zone
Benthic
zone
Zonation in a lake
Pelagic
zone
Aphotic
zone
LE 50-16b
Intertidal zone
Neritic zone
0
Oceanic zone
Photic zone
200 m
Continental
shelf
Pelagic
zone
Benthic
zone
2,500–6,000 m
Abyssal zone
(deepest regions of ocean floor)
Marine zonation
Aphotic
zone
• Major aquatic biomes:
– Lakes
– Wetlands
– Streams and rivers
– Estuaries
– Intertidal zones
– Oceanic pelagic biome
– Coral reefs
– Marine benthic zone
Climate largely determines the
distribution and structure of terrestrial
biomes
• Climate is very important in determining why
terrestrial biomes are found in certain areas
Climate and Terrestrial Biomes
• Climate has a great impact on the distribution of
organisms, as seen on a climograph
• Altitude and latitude also play a role in
determining where biomes are located
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
General Features of Terrestrial Biomes
• Terrestrial biomes are often named for major
physical or climatic factors and for vegetation
• Stratification is a key feature of terrestrial
biomes
• Terrestrial biomes usually grade into each other,
without sharp boundaries
• The area of intergradation, called an ecotone,
may be wide or narrow
• Major terrestrial biomes:
– Tropical forest
– Desert
– Savanna
– Chaparral
– Temperate grassland
– Coniferous forest
– Temperate broadleaf forest
– Tundra