AQUATIC HABITATS AND

TERRESTRIAL BIOMES

Fig 50.17 shows the distribution of major aquatic biomes
More than 97% of earth's water is in oceans

Water in the Biosphere (modified from Wetzel 1983). Do NOT memorize.

Location	Volume (km 3 x 1000)	% of total	Renewal time
Oceans	1,370,000	97.61	3100 yrs
Polar ice, glaciers	29,000	2.08	16,000 yrs
Groundwater	4000	0.29	300 yrs
Freshwater lakes	125	0.009	1-100 yrs
Saline lakes	104	0.008	10-1000 yrs
Soil	67	0.005	280 days
Rivers	1.2	0.00009	12-20 days
Atmosphere	14	0.0009	9 days

Fresh Water

Lentic waters

Lakes exhibit thermal stratification (layering) - Fig. 50.15

thermocline
water most dense at 4 o C
turnover
Colder areas, dimictic
In Texas and other warm areas, only one mixing per year - monomictic

Lakes subdivided into three zones by light penetration - Fig. 50.18 - photic vs. aphotic zones

Littoral zone
Limnetic zone
Profundal zone

Benthic zone
Compensation point

Lakes Divided into Productivity Categories

Oligotrophic lakes - Fig. 50.19a
Mesotrophic lakes
Eutrophic lakes - Fig. 50.19b

Lakes temporary
Go through succession
Oligotrophic > mesotrophic > eutrophic > marsh > land
Marshes and swamps (freshwater wetlands) constitute intermediate zones - Fig. 50.21a

Lotic waters - Rivers and streams - Fig. 50.19c

riffles, runs, and pools
erosion and deposition

rivers and streams much older and more permanent

Dams - Fig. 50.20

Marine Habitats - Fig. 50.17

Estuaries - Fig. 50.21b

Two major zones based on light penetration

photic

aphotic

Two major areas

pelagic

benthic

Major Kinds of Oceanic Habitats - Fig. 50.22

intertidal zone Tides - Fig. 50.23a

neritic zone

continental shelf
oceanic zone
abyssal zone

deep sea hydrothermal vents - Fig. 50.23c - a black smoker - Tubeworms - The movie

Coral Reefs - Fig. 50.23b - The Movie

Terrestrial biomes

Biomes are terrestrial communities occurring over wide areas

Recognized by characteristic appearance
Associated with characteristic climates
Classified by vegetation

Distribution - Fig. 50.24 of biomes is a result of: See Fig. 50.10 for a climograph

climate - primarily determined by temperature and precipitation

latitudes and altitudes
precipitation
soil

Tropical Dry Forests

Alternate wet and dry periods - also called seasonal rainforest

Many trees lose leaves in dry period.

Tropical Rain Forests

Richest biome in terms of number of species
Substantial rainfall throughout year

Competition great for sunlight; epiphytes and vines common

Savannas - Fig. 50.25b

Reduced rainfall with prolonged dry seasons
Open grassland with scattered shrubs and trees
Maintained by periodic fires - fire adapted

Large herbivores and their predators dominate

Deserts - Fig. 50.25c

Extremely low rainfall
All great deserts at or near 30 degrees latitude N or S - Map
Other major deserts at continental interiors
Other deserts on leeward side of mountain ranges
Rain shadow effect: drier on leeward side of mountain

Both cold and hot deserts

Special adaptations by both plants and animals

Chaparral - Fig. 50.25d

Spiny evergreen shrubs
Climate dry in summer
Maintained by fire, needed for some seeds to germinate - fire adapted

Temperate Grasslands - Fig. 50.25e

Grasslands also called plains or prairies
Maintained by grazing (large herbivores) and periodic fires or become forest - fire adapted

Most grasslands in US now converted to agriculture

Temperate Deciduous Forests - Fig. 50.25f

Dominated by deciduous trees like oak, hickory, elm, maple, ash - lose leaves in winter
Moderate rainfall

Coniferous forests - also called boreal forests or taiga - Fig. 50.25g

Northern coniferous forests of Eurasia and North America
Long, cold dry winters

Largest terrestrial biome

Very short growning season

Now being logged at a treamendous rate

Temperate Rain Forests - Fig. 50.25g3

Cool weather, dense fog, high precipitation

On coastlines as in northwestern U.S.

Large evergreens, many epiphytes

Very important timber - little old growth left

Tundra - Fig. 50.25h

Bitter cold, high winds
Very low precipitation

Very short growing season
Permanent ice, permafrost, underlying surface

Arctic (far north) and high mountains.

Polar Ice

Ice caps at north (Arctic) and south (Antarctic) poles
No precipitation, fresh water scarce, life limited to coasts
Only bacteria, algae, small insects in Antarctic interior

Texas Ecoregions from Texas Parks and Wildlife