Environmental science
chapter 6 and 7
Communities,
Biomes, &
Population Biology
I. Limiting Factors
- factors that affect an
organism's ability to
survive in its environment
- temperature, rainfall, fire,
food, predators, etc.
A. Optimum Range:
- area with fewest limiting
factors
B. Range of Tolerance:
- area with a few limiting
factors
C. Zone of Stress:
- area with several limiting
factor
Optimum Range
Optimum Range
Range of Tolerance
Distribution of
Douglas-fir
*
Microclimate
II. Ecological Succession
Mount St. Helens
explosion, 1980
Same view,
20 years later
II. Ecological Succession
- the replacement of one
community by another over
time
- one community changes the
physical environment so that it
can't survive but another
community can
A. Primary Succession:
- succession on land that has
not been previously occupied
- ex. lava, ash, bare rock
- Pioneer species:
mosses, lichen - build soil
Primary Succession
Succession in a Pond
(c)
(a)
(b)
B. Secondary Succession
- reestablishing an ecosystem
following disturbance
- ex. mudslides, hurricanes,
flood, ‘cool’ fire, clearcutting,
abandoned fields
Secondary Succession
C. Climax Ecosystem
- a stable,
balanced
community
C. Climax Ecosystem
- occurs at the end of
succession
- can regenerate itself
(plants can tolerate shade)
III. Biomes:
- a large group of ecosystems
with a characteristic climate
and dominant plant life
A. Aquatic Biomes
- supports great variety of life
- limiting factors: light, oxygen,
CO2, nutrients, temperature
1. Marine Biomes:
- vast and varied habitats
- light penetrates only 100 - 600
feet (photic zone)
Intertidal Neritic
Zone
Zone
Open
Photic
Ocean
ZoneZone
Marine
Biomes
Aphotic
Deep-Zone
Sea
Zone
a) Intertidal Zone:
- harsh
environment:
tides, waves,
exposure to
air
b) Neritic Zone:
- between low tide and open-sea
- abundant nutrients
- most productive marine
environment
Coral Reef
Kelp Forest
c) Open-Ocean Zone:
- low nutrients and fewer living
organisms
d) Benthic Zone:
- extremely
harsh
environment
- cold, dark,
high pressure
‘Black
Smoker’
d) Benthic Zone:
- habitat for bizarre fish and
other animals
Fangtooth
Umbrellamouth
Gulper
Deep-sea Anglerfish
2. Estuaries:
- boundary between fresh and
salt water
2. Estuaries:
- boundary between fresh and
salt water
- highly productive habitat for
many animals
- abundant nutrients and light
- "nursery" for many animals
3. Freshwater Biomes:
- rivers, lakes,
ponds, and
groundwater
- < 1% of earth's
water
- drinking water
- dumping ground
for wastes
B. Terrestrial Biomes
- most important limiting
factors are temperature
and precipitation
Terrestrial Biomes
High
(Temperature) Low
Climate Affects Biome Distribution
Dry
(Rainfall)
Wet
Low
(Altitude)
High
Effects of Elevation on
Temperature
Equatorial
(Latitude)
Polar
Olympic/Cascade Rain Shadow
Average Annual
Precipitation (cm)
150
Altitude (m)
5000
4000
100
3000
2000
50
1000
0
West
East
0
Earth’s Curvature and
Tilt Make Seasons
Short days;
Long nights;
Winter
Long days;
Short nights;
Summer
Air Currents & Climatic Regions
Saharan &
Arabian deserts
are @ 30° N
South African
Desert
is @ 30° S
Congo rain
forest is @ 0°
1. Tundra
Tundra
Treeless region < 10 in. rain annually
Permanently frozen soil (permafrost)
Very fragile, scars last for centuries
Biome
Tundra
Climate
Very cold/ Brief summer
Treeless
< 10” Precip. / Permafrost Short Plants
Taiga
Deciduous
Forest
Grassland
Desert
Tropical
Rain
Forest
Dominant Plants
2. Taiga
Taiga
(Northern Coniferous Forest)
Northern Canada
and Eurasia
Winters long & cold
Evergreen
coniferous trees
with needle-like
leaves
Plant & animal
diversity low
Biome
Tundra
Taiga
Climate
Very cold/ Brief summer
< 10” Precip. / Permafrost
Long winter/Short Summer
Low Precip.
Deciduous
Forest
Grassland
Desert
Tropical
Rain
Forest
Dominant Plants
Treeless
Short Plants
Conifers
(Spruce/Fir)
3. Temperate Deciduous Forests
Temperate Deciduous Forest
30-60 in. rain
annually, most
during summer
Mostly deciduous
trees, bare in
winter
Leaf litter on soil
High diversity of
animals
Biome
Tundra
Climate
Dominant Plants
Very cold/ Brief summer
Treeless
< 10” Precip. / Permafrost
Short Plants
Taiga
Long winter/Short Summer Conifers
Low Precip.
(Spruce/Fir)
Deciduous Cold winter/Warm summer Deciduous Trees
Forest 30 - 60” Precip.
(Oak, Maple, Elm)
Grassland
Desert
Tropical
Rain
Forest
Temperate Rain Forest
Temperate Rain Forest
Abundant rain
Soil seldom
freezes
Usually coastal
4. Grasslands
Grasslands
10-30 in. rain/year
Usually in centers of
continents
Shortgrass Prairie
No trees except by
rivers
Periodic droughts
Frequent fires
Most fertile soil in
world
Overgrazing problems
Sagebrush Desert or
Shortgrass Prairie
Biome
Tundra
Climate
Dominant Plants
Very cold/ Brief summer
< 10” Precip. / Permafrost
Taiga
Long winter/Short summer
Low Precip.
Deciduous Cold winter/Warm summer
Forest 30 - 60” Precip.
Treeless
Short Plants
Conifers
(Spruce/Fir)
Deciduous Trees
(Oak, Maple, Elm)
Grassland Cold Winter/Warm Summer Grasses, Grains
Desert
Tropical
Rain
Forest
10 - 30” Precip.
Tall wildflowers
5. Deserts
Desert
Usually found
between 20-30°
N & S latitude
Less than 10 in.
rain/yr.
Boom & bust
population growth
after rain
Very fragile
ecology
Biome
Tundra
Climate
Dominant Plants
Very cold/ Brief summer
< 10” Precip. / Permafrost
Taiga
Long winter/Short summer
Low Precip.
Deciduous Cold winter/Warm summer
Forest
30 - 60” Precip.
Treeless
Short Plants
Conifers
(Spruce/Fir)
Deciduous Trees
(Oak, Maple, Elm)
Grassland Cold Winter/Warm Summer Grasses, Grains
Desert
Tropical
Rain
Forest
10 - 30” Precip.
Cold Winter/Hot summer
< 10” Precip.
Tall wildflowers
Sparse Veget.
(Cactus, etc.)
Sonoran Desert
Arizona
Flowers indicate
recent rain
Saguaro cactus
unique to this
desert
Environment Molds Physical Traits
An American
cactus
An African
euphorb
Chaparral
The Chaparral Biome
Often in coastal
regions bordering
deserts
Up to 30 in. rain
annually, but all
during cool months
Summers hot & dry
Small trees & large
bushes
6. Tropical Rain Forest
Tropical Rain Forest Biome
Temp 77-86 °F
Rainfall 100-160 in
Biodiversity: 50-67%
of all Earth’s species
6% of land area
40% now gone
- Losing 70 acres/min
> 25000 species go
extinct annually
Dominated by large,
broadleaf, evergreen,
complex forests
Biome
Tundra
Climate
Dominant Plants
Very cold/ Brief summer
< 10” Precip. / Permafrost
Taiga
Long winter/Short summer
Low Precip.
Deciduous Cold winter/Warm summer
Forest
30 - 60” Precip.
Treeless
Short Plants
Conifers
(Spruce/Fir)
Deciduous Trees
(Oak, Maple, Elm)
Grassland Cold Winter/Warm Summer Grasses, Grains
Desert
10 - 30” Precip.
Cold Winter/Hot summer
< 10” Precip.
Tropical
Rain
No winter
Evergreen,
Forest
Tall wildflowers
Sparse Veget.
Cactus, etc.
Complex,
Broadleaf Forests
Tropical Deciduous Forest
Savanna
The African Savanna
Grasses dominate;
scattered trees
Short rainy season
<12 in. (30 cm)/year
Long, severe
droughts
African savanna with
many large animals
Many species in
danger of extinction
Ecosystem Productivity Compared
(Grams of biomass/meter2/year)
Tundra
(140)
Tropical
Rainforest
(2200)
Open
OceanNeritic
(125) (360)
Estuary
(1500)
Taiga
(800)
Temperate
Deciduous Forest
(1200)
Grassland
(600)
Desert
(90)
The
End