Biomes and The Biosphere

Introduction to Ecology• Study of interactions between organisms and

the environment• Abiotic and biotic factors play a role in distribution

and abundance of a species• The Biosphere

• Entire portion of Earth inhabited by life

Climate• Temperature,

precipitation, sunlight, and wind• Most significant

influence on distribution of organisms

• Determined by sunlight intensity, air currents, presence of large bodies of water, mountain ranges• All of these vary mainly

as a factor of latitude and altitude

• Climograph

North Pole60°NLow angle of incoming sunlight

Low angle of incoming sunlight

Sunlight directly overhead at equinoxes

Tropic ofCancer

60°SSouth Pole

30°N

Atmosphere

30°S

Tropic ofCapricorn

0° (equator)

Biomes• Major ecosystem, characterized by a particular climate and type of vegetation

Temperate grassland Tropical forestDesert

Temperatebroadleafforest

Coniferousforest

Arctic andalpinetundra

Annual mean precipitation (cm)

Ann

u al m

e an

tem

per a

ture

(°C

)

400300200100

30

15

0

–15

Climate and Biomes

• Biomes change with altitude and latitude because vegetation is partly determined by temperature (and precipitation).

Terrestrial Biomes• Tropical forests: equator, most complex, constant temperature and rainfall, canopy• Savanna: tropical grassland with scattered trees, occasional fire and drought; large

herbivores• Desert: sparse rainfall• Chaparral: spiny evergreen at midlatitudes along coasts• Temperate grassland: All grasses; seasonal drought; occasional fires; large

mammals• Coniferous forest: cone-bearing trees• Tundra: permafrost; very little precipitation

Temperate grassland

Tropic ofCancer

30°N

Tropic ofCapricorn

30°S

Equator

Tropical forest

DesertSavanna

Key Chaparral

Coniferous forestTemperate broadleaf forest

TundraHigh mountainsPolar ice

Aquatic Biomes• Freshwater or marine (saltwater)• Physically and chemically stratified

• Vertical stratification• Photic zone - light (photosynthetic organisms; phytoplankton)• Aphotic zone - little light• Benthic zone - bottom substrate

• Benthos - community of organisms that live in benthic zone• Detritus - dead organic material

• Distance from shore• Littoral, limnetic• Intertidal, neritic, oceanic

• Open water versus bottom (pelagic vs benthic)• Chemical stratification

• Changes in temperature, oxygen and nutrient content vary with depth• Thermocline - narrow stratum of rapid temperature change that

separates more uniformly warm upper layer from more uniform cold deeper waters

• Turnover

Marine biomes• Intertidal zone -

area where land meets water

• Neritic zone - shallow regions over continental shelves

• Oceanic zone - very deep water past the continental shelves

• Pelagic zone - open water of any depth

• Benthic zone - seafloor bottom

• Abyssal zone - benthic region in deep oceans

Marine zonation

Benthic zone

Aphoticzone

Photic zone

Pelagic zoneCoastal zone

Intertidal zone

Continentalshelf

0

200 m

2,500–6,000 mAbyssal zone

(deepest regions of ocean floor)

Freshwater Biomes• Littoral zone

• Shallow, well lit waters, close to shore, rooted plants

• Limnetic zone• Well-lit, open water,

farther from shore, phytoplankton and cyanobacteria

• Profundal zone• Deep, aphotic waters

• Lake classification• Oligotrophic - deep,

nutrient poor• Eutrophic - shallow, high

nutrient content

Zonation in a lake

Benthic zone

Pelagiczone

Aphoticzone

Photiczone

Littoralzone Limnetic

zone

Turnover in Lakes• Seasonal turnover due to changes in temperature cycles

oxygen and nutrients between photic and aphotic zones

WinterO2 (mg/L)12

Lake

dep

th (m

)

24

16

8

840

O2 concentrationHigh (>8 mg/L)Medium (4–8 mg/L)Low (<4 mg/L)

O2 (mg/L)12

Lake

dep

th (m

)

24

16

8

840O2 (mg/L)

12

Lake

dep

th (m

)

24

16

8

840

O2 (mg/L)12

Lake

dep

th (m

)

24

16

8

840

Autumn Summer

Spring

Thermocline4°C

5°6°

8°18°

20°22°

4°C

4°4°

4°4°

4°

4°C

4°4°

4°4°

4°4°C

4°4°

2°0°

4°