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Chapter 52: Intro to Ecology and the Biosphere 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
•
It deals with studying all levels of biological organization that are larger
than an organism (so it doesn’t study cells, organs, or tissues)
•
It is also a rigorous experimental driven science
•
Events that occur in ecological time affect life on the scale of
evolutionary time
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Ecology outline:
•
What do ecologists study/subfields within ecology
•
What factors influence species distribution?
–
How do we study distribution?
–
Species transplants
–
Behavior and habitat selection
–
Species interactions
–
Abiotic (non-living) influences
–
Climate – seasons, earth’s tilt, wind, mountains and lakes
•
Aquatic biomes
•
Terrestrial biomes
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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
•
Ecologists use observations and experiments to test explanations for
the distribution and abundance of species
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Ecologists study the distribution and abundance of species
Kangaroos/km2
0–0.1
0.1–1
1–5
5–10
10–20
> 20
Limits of
distribution
Subfields of Ecology
•
Organismal ecology studies how an organism’s structure, physiology,
and (for animals) behavior meet environmental challenges
Organismal ecology
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Subfields of Ecology
•
Population ecology focuses on factors affecting how many individuals
of a species live in an area
Population ecology
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Subfields of Ecology
•
Community ecology deals with the whole array of interacting species
in a community
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Community ecology
Subfields of Ecology
•
Ecosystem ecology emphasizes energy flow and chemical cycling
among the various biotic and abiotic components
Ecosystem ecology
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Subfields of Ecology
•
Landscape ecology deals with arrays of ecosystems and how they
are arranged in a geographic region
Landscape ecology
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Ecology, the Biosphere and Environmental Issues
•
The biosphere is the global
ecosystem, the sum of all the
planet’s ecosystems
•
Ecology provides the scientific
understanding underlying
environmental issues
•
Most ecologists follow the
precautionary principle regarding
environmental issues: humans
need to be concerned with how
their actions affect the environment
•
Rachel Carson is credited with
starting the modern environmental
movement
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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
•Many naturalists began to identify broad patterns of distribution by naming
biogeographic realms
Palearctic
Nearctic
Tropic
of Cancer
(23.5°N)
Oriental
Ethiopian
Equator
Neotropical
(23.5°S)
Tropic of
Capricorn
Australian
Biogeography is a good starting point for
understanding what limits geographic
distribution of species
Species absent
because
Yes Area inaccessible
or insufficient time
Dispersal
limits
distribution?
No
Behavior
limits
distribution?
Yes
No
Habitat selection
Biotic factors
(other species)
limit
distribution?
Yes Predation, parasitism,
Chemical
competition, disease factors
Water
Oxygen
Abiotic factors
Salinity
No
limit
pH
distribution?
Soil nutrients, etc.
Temperature
Physical Light
factors Soil structure
Fire
Moisture, etc.
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
•
Natural range expansions show the influence of dispersal on
distribution
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Dispersal and Distribution
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
–
Sometimes the transplanted species may not survive in the new
location
–
Sometimes the transplanted species can thrive and become a
pest to other organisms in the new ecosystem
–
The most extreme effects of the new species can be a disruption
of the balance between the different species of organisms that
were originally living in the ecosystem
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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 that affect the distribution of organisms may include:
–
Interactions with other species
–
Predation
–
Competition
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Interactions with other species influence 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 - an important factor in distribution of organisms
because of its effects on biological processes
–
Water - availability in habitats is another important factor in
species distribution as species move based on their needs
–
Sunlight - Light intensity and quality affects photosynthesis. It is
also important to development and behavior of organisms
sensitive to photoperiod
–
Wind - amplifies effects of temperature by increasing heat loss
from evaporation and convection. It can change morphology of
plants
–
Rocks and soil - limit distribution of plants and thus the animals
that feed upon them due to its physical structure, pH, and mineral
composition
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Wind can affect plant morphology
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Climate
•
Four major abiotic components of climate: temperature, water, sunlight,
and wind
•
Climate is the prevailing weather in an area
•
Microclimate consists of very fine patterns, such as those
encountered by the community of organisms underneath a fallen log
–
•
Microclimate is determined by fine-scale differences in abiotic
factors
Macroclimate consists of patterns on the global, regional, and local
level
–
Global climate patterns are determined largely by the intensity of
solar energy and the planet’s movement in space
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The intensity of sunlight greatly influences climate
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 variations of light and temperature
increase steadily toward the poles
60°N
30°N
June solstice:
Northern Hemisphere
tilts toward sun;
summer begins in
Northern Hemisphere;
winter begins in
Southern
Hemisphere.
0° (equator)
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.
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.
Seasonal variation is due to the tilt of the earth!
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
Deserts tend to be around the 30º latitude lines
Global air circulation and wind patterns play
major roles in determining climate patterns
Arctic
Circle
60°N
Westerlies
30°N
Northeast trades
Doldrums
Southeast trades
0°
(equator)
30°S
Westerlies
60°S
Antarctic
Circle
Regional, Local, and Seasonal Effects on Climate
•
Various features of the landscape contribute to local variations in
climate
•
Seasonal variation also influences climate
•
Oceans and their currents and large lakes moderate the climate of
nearby terrestrial environments
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Bodies of Water modulate temperature and climate
Air cools at
high elevation.
Cooler
air sinks
over water.
Cool air over water
moves inland, replacing
rising warm air over land.
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Warm air
over land rises.
Mountains
•
Mountains have a significant effect on
–
The amount of sunlight reaching an area
–
Local temperature
–
Rainfall
Wind
direction
East
Pacific
Ocean
Coast
Range
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Sierra
Nevada
Seasonality
The angle of the sun and how its rays strike the earth leads to many
seasonal changes in local environments
•
Lakes are sensitive to seasonal temperature change and experience
seasonal turnover – because water is most dense at 4ºC and will sink!
Lake depth (m)
0
4
Spring
Winter
O2 (mg/L)
8
12
8
16
2°
4°
4°
4°
4°C
24
O2 concentration
0°
4°
4°
Lake depth (m)
•
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)
O2 (mg/L)
0
4
8
12
8
4°
4°
22°
20°
18°
8°
6°
5°
4°C
4°
4°
4°
4°C
16
24
Autumn
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Thermocline
Summer
Lake depth (m)
Lake depth (m)
Low (<4 mg/L)
O2 (mg/L)
0
8
16
24
4
Long-Term Climate Change
•
One way to predict future global climate change is to study previous
changes – here, predicting the range of a species based on change
Current
range
Predicted
range
Overlap
4.5°C warming over
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next century
6.5°C warming over
next century
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
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Major aquatic biomes
• Lakes
• Wetlands
• Streams and rivers
• Estuaries
• Intertidal zones
• Oceanic pelagic biome
• Coral reefs
• Marine benthic zone
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Aquatic biomes
30°N
Tropic of
Cancer
Equator
Tropic of
Capricorn
Continental
shelf
30°S
Key
Lakes
Rivers
Estuaries
Coral
reefs
Oceanic
pelagic zone
Intertidal
zone
Abyssal zone
(below oceanic
pelagic zone)
Many aquatic biomes are stratified into zones or layers
defined by light penetration, temperature, and depth
Littoral
zone
Limnetic
zone
Photic
zone
Benthic
zone
Zonation in a lake
Pelagic
zone
Aphotic
zone
Many aquatic biomes are stratified into zones or layers
defined by light penetration, temperature, and depth
Intertidal zone
Neritic zone
0
Oceanic zone
Photic zone
200 m
Continental
shelf
Pelagic
zone
Benthic
zone
Aphotic
zone
2,500–6,000 m
Abyssal zone
(deepest regions of ocean floor)
Marine zonation
Lakes
•
Salinity and oxygen content is variable
•
Contain small invertebrates and fish
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Wetlands
•
Are areas of ‘standing water’, or areas commonly flooded
•
One of the most productive biomes on earth
•
Lots of plants, mosses, invertebrates, vertebrates
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Streams and Rivers
•
Most defining feature is that the water carries a current
•
Salinity increases towards ends of rivers
•
Many fishes and invertebrates live here
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Estuaries
•
Transition between
rivers and the
ocean/sea
•
High in sediments and
salinity VERY variable,
even with tides
•
Saltmarsh grasses and
algae, crabs, oysters,
clams, worms and fish
live here
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Intertidal Zones
•
Areas where the tide
covers and then
uncovers the area with
water
•
Usually lots of sand or
very rocky
•
Clams, crustaceans,
sponges, sea anemones,
mollusks live here
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The Oceanic Pelagic Biome
•
Vast, open ocean water
•
Biggest water biome
•
High salinity
•
Invertebrates, zooplankton, large
free swimming organisms live
here
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Coral Reefs
•
Very high oxygen levels
•
Composed of solid calcium
carbonate and coral
skeletons
•
Algae, corals and diverse
fish live here
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The Marine Benthic Zone
•
This is the seafloor
•
Seaweeds live in shallow
water
•
Lots of invertebrates and
fish live here
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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 has a great impact on the distribution of organisms
•
Organism distributions are often depicted on a climograph
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Climographs show climate differences between biomes
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
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 of two biomes, called an ecotone, may be
wide or narrow
•
There are often regions of ‘patchiness’ of vegetation and animal growth
within a single biome
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Major terrestrial biomes
– Tropical forest
– Desert
– Savanna
– Chaparral
– Temperate grassland
– Temperate broadleaf forest (Deciduous Forest)
– Coniferous forest (Taiga)
– Tundra
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Global distribution of Terrestrial Biomes
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
Tropical Forest
•
LOTS of rainfall ~200-400 cM annually in rainforest, 150-200 cM in
tropical dry forests, warm temperatures year around, VERY extreme
temperatures!!
•
Insane amount of plant diversity with many different canopy levels
•
Highest amount of animal diversity of any terrestrial biome live here
–
Amphibians, birds, mammals, insects
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Desert
•
LOW and variable amounts of precipitation, <30 cM per year
•
Located mostly at 30 degrees north and south latitudes, - this is the
same areas where air masses tend to descend!
•
Low, widely dispersed vegetation lives here, mainly succulent plants
(cactus)
•
Snakes, lizards, scorpions rodents live here
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Savanna
•
Seasonal rainfall – has distinct wet and LONG dry seasons, Warm
temperatures, but somewhat seasonal
•
Thorny plants, grasses, small trees
•
Large herbivors live here – zebras, antelope. Also lots of insects.
Predators such as lions and hyenas live here also
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Chaparral
•
Seasonal rainfalls, cool winter and spring, Can be very warm in
summer
•
Shrubs, small trees and some grasses live here
•
Deer, amphibians, birds and reptiles are common
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Temperate Grassland
•
Highly seasonal precipitation with periodic droughts are common. Cold
winters and hot summers
•
Grasses are the DOMINANT plants.
•
Grazing mammals – bison and wild horses, and burrowing mammals –
prairie dogs are found here
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Temperate Broadleaf Forest – aka Deciduous Forest
•
This is here – cold winters, hot and humid summers, but I don’t have to
tell you that!
•
Diverse trees, they lose their leaves in the fall
•
Many mammals, birds, whatever you see outside – squirrels
everywhere!
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Coniferous Forest (Taiga)
•
Long and cold winters (think Siberia) -70 C, summers may be hot,
rainfall is variable
•
Cone bearing trees – pine and spruce here, and some shrubs
•
Lots of birds, moose and bears here
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Tundra
•
This is the Arctic ~20% of the earth’s land surface
•
Variable precipitation, Long and cold winters, Short and cool summers
•
Lichens, mosses, grasses and dwarf shrubs and trees can survive
•
Caribou, reindeer, musk ox, bears, wolves and foxes are here
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