Chapter 6 Flashcards
Biomes
geographic regions that contain communities composed of organisms with similar adaptations.
Boundaries between biomes can be unclear.
There is often an association between the plant forms in a biome and the animal forms that live there.
Convergent evolution
a phenomenon in which two species descended from unrelated ancestors look similar because they have evolved under similar selective forces.
Climate diagrams
graphs that plot the average monthly temperature and precipitation of a specific location on Earth.
Growing season
months that are warm enough to allow plant growth (i.e., temperatures > 0°C; see shaded months in diagrams).
Tundras
The coldest biome, characterized by a treeless expanse above permanently frozen soil (permafrost).
Soils are acidic and nutrient-poor.
Plants grow low to the ground to gain protection under snow and ice.
Alpine tundras occur at high elevations in temperate and tropical latitudes; they have a longer growing season.
Boreal forests
A biome densely populated by evergreen needle-leaved trees, with a short growing season and severe winters.
Litter decomposes slowly and accumulates, forming the largest reservoir of organic carbon on Earth.
Soils are acidic and podsolized.
Species diversity is low, but the biome is a major source of lumber and paper.
Temperate rainforests
A biome known for mild temperatures and abundant precipitation, and dominated by evergreen forests.
Warmer conditions are due to nearby warm ocean currents.
These forests typically support low species diversity.
Temperate seasonal rainforests
A biome with moderate temperature and precipitation conditions, dominated by deciduous trees (e.g., maple, beech, and oak).
Conditions fluctuate because forests are not near warm ocean currents.
Soils are podsolized, slightly acidic, and support a layer of small plants beneath the dominant trees.
Warmer and drier parts of the biome are dominated by pines.
Woodlands / shrublands
A biome characterized by hot, dry summers and mild, wet winters, a combination that favors the growth of drought-tolerant grasses and shrubs.
There is a 12-month growing season, but dry summers, cold winters, and frequent fires limit plant growth.
Dominated by schlerophyllous vegetation, which has small and durable leaves that resist dessication.
Temperate grasslands / cold deserts
A biome characterized by hot, dry summers and cold winters; dominated by grasses, non-woody flowering plants, and drought-adapted shrubs.
Soils are low in acidity and nutrient- rich with lots of organic matter.
Tropical rainforests
A warm and rainy (at least 2,000 mm annually) biome, with multiple layers of lush vegetation.
There is a canopy of 30–40 m trees with an understory containing smaller trees, shrubs, epiphytes, and vines.
Species diversity is higher than anywhere else in the world.
Organic matter decomposes quickly; vegetation rapidly takes up nutrients.
Soils are devoid of humus and clay, and retain nutrients very poorly.
Tropical seasonal forests / savannas
A biome with warm temperatures and pronounced wet and dry seasons (due to movement of the intertropical convergence zone), dominated by deciduous trees that shed leaves during the dry season.
Savannas have long dry periods and contain grasses and occasional trees.
Fire and grazing maintain savannas.
Soils do not hold nutrients but the warm climate favors rapid decomposition and fast growth.
Subtropical deserts
A biome characterized by hot temperatures, scarce rainfall, long growing seasons, and sparse vegetation.
Associated with dry, descending air of Hadley cells.
Soils are shallow and devoid of organic matter, and neutral in pH.
Moister sites support succulent cacti, shrubs, and small trees (e.g., mesquite, paloverde).
Lotic
characterized by flowing water.
Stream (or creek)
a narrow channel of fast-flowing fresh water.
River
a wide channel of slow-flowing fresh water.
Riparian zone
terrestrial vegetation alongside rivers and streams that is influenced by seasonal flooding and elevated water tables.
Allochthonous
inputs of organic matter, such as leaves, that come from outside of an ecosystem (e.g., from a riparian zone).
Autochthonous
Inputs of organic matter that are produced by algae and aquatic plants inside an ecosystem.
Much of the organic matter in streams is ____________, whereas organic matter in rivers is ______________.
allochthonous; autochthonous
What may reduce primary production in rivers?
Rivers typically accumulate sediments from land, and high turbidity can block light and reduce primary production.
Why are dams built?
to control flooding, provide water for irrigation, or to generate electricity.
What are 3 disadvantages of dams?
1) Water behind dams often becomes warmer, and the stream bottoms become filled with silt that destroys habitat for aquatic organisms.
2) Water released from the dams has low oxygen concentrations.
3) Dams alter seasonal cycles of flooding and disrupt the natural movement of aquatic organisms upstream and downstream.
Pond
An aquatic biome that is smaller than a lake and is characterized by non-flowing fresh water with some area of water that is too deep for plants to rise above the water’s surface.
Lake
An aquatic biome that is larger than a pond and is characterized by non-flowing fresh water with some area of water that is too deep for plants to rise above the water’s surface.
Littoral zone
the shallow area around the edge of a lake or pond containing rooted vegetation.
Limnetic (pelagic) zone
the open water beyond the littoral zone, where the dominant photosynthetic organisms are floating algae (i.e., phytoplankton).
Profundal zone
the area in a lake that is too deep to receive sunlight; typically has low concentrations of oxygen.
Benthic zone
the area with sediments at the bottom of lakes, ponds, and oceans; is habitat for burrowing organisms.
Epilimnion
the surface layer of water in a lake or pond.
Hypolimnion
the deeper layer of water in a lake or pond; can include the lower limnetic profundal zone.
Thermocline
A middle depth of water in a
lake or pond that experiences a rapid change in temperature over a relatively short distance in depth; slow mixing between the epilimnion and hypolimnion.
Spring overturn
the vertical mixing of lake water that occurs in early spring, assisted by winds that drive the surface currents.
Stratification
the condition of a lake or pond when the warmer, less dense surface water floats on the cooler, denser water below.
Fall overturn
the vertical mixing that occurs in fall, assisted by winds that drive the surface currents.
Fall bloom
a rapid increase in the population of phytoplankton in fall that occurs with the infusion of nutrients from fall overturn.
Freshwater wetland
an aquatic biome containing standing fresh water, or soils saturated with fresh water for at least part of the year; shallow enough for emergent vegetation throughout all depths.
Swamps
contain emergent trees.
Marshes
contain emergent non-woody vegetation.
Bogs
contain acidic water and plants adapted to these conditions.
Salt marshes
a saltwater biome that contains non-woody emergent vegetation.
Where are salt marshes found?
Salt marshes are often found at continental coasts and in estuaries where the mouths of rivers mix with salt water from oceans.
Mangrove swamps
a biome that occurs along tropical and subtropical coasts, and contains salt-tolerant trees with roots submerged in water.
Intertidal zones
a biome consisting of the narrow band of coastline between the levels of high tide and low tide.
As the tide comes and goes, water exhibits widely fluctuating temperatures and salt concentrations.
Coral reefs
a marine biome found in warm, shallow waters that are 20°C year- round.
Corals are tiny animals in a mutualistic relationship with algae; corals produce CO2, and algae produce sugars.
They are hollow tubes with exoskeletons and tentacles that collect detritus and plankton.
Neritic zone
the ocean zone beyond the range of the lowest tidal level and which extends to depths of about 200 m; generally a region of high productivity.
Oceanic zone
the ocean zone beyond the neritic zone; nutrients are sparse and production is limited.
Photic zone
the area of the neritic and oceanic zones that contains sufficient light for photosynthesis by algae.
Aphotic zone
the area of the neritic and oceanic zones where water is so deep that sunlight cannot penetrate; less productive but organisms have adaptations (e.g., chemosynthesis, bioluminescence).
