Chapter 6

Question 1

Biomes

Answer 1

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.

Question 2

Convergent evolution

Answer 2

a phenomenon in which two species descended from unrelated ancestors look similar because they have evolved under similar selective forces.

Question 3

Climate diagrams

Answer 3

graphs that plot the average monthly temperature and precipitation of a specific location on Earth.

Question 4

Growing season

Answer 4

months that are warm enough to allow plant growth (i.e., temperatures > 0°C; see shaded months in diagrams).

Question 5

Tundras

Answer 5

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.

Question 6

Boreal forests

Answer 6

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.

Question 7

Temperate rainforests

Answer 7

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.

Question 8

Temperate seasonal rainforests

Answer 8

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.

Question 9

Woodlands / shrublands

Answer 9

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.

Question 10

Temperate grasslands / cold deserts

Answer 10

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.

Question 11

Tropical rainforests

Answer 11

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.

Question 12

Tropical seasonal forests / savannas

Answer 12

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.

Question 13

Subtropical deserts

Answer 13

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).

Question 14

Lotic

Answer 14

characterized by flowing water.

Question 15

Stream (or creek)

Answer 15

a narrow channel of fast-flowing fresh water.

Question 16

River

Answer 16

a wide channel of slow-flowing fresh water.

Question 17

Riparian zone

Answer 17

terrestrial vegetation alongside rivers and streams that is influenced by seasonal flooding and elevated water tables.

Question 18

Allochthonous

Answer 18

inputs of organic matter, such as leaves, that come from outside of an ecosystem (e.g., from a riparian zone).

Question 19

Autochthonous

Answer 19

Inputs of organic matter that are produced by algae and aquatic plants inside an ecosystem.

Question 20

Much of the organic matter in streams is ____________, whereas organic matter in rivers is ______________.

Answer 20

allochthonous; autochthonous

Question 21

What may reduce primary production in rivers?

Answer 21

Rivers typically accumulate sediments from land, and high turbidity can block light and reduce primary production.

Question 22

Why are dams built?

Answer 22

to control flooding, provide water for irrigation, or to generate electricity.

Question 23

What are 3 disadvantages of dams?

Answer 23

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.

Question 24

Pond

Answer 24

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.

Question 25

Lake

Answer 25

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.

Question 26

Littoral zone

Answer 26

the shallow area around the edge of a lake or pond containing rooted vegetation.

Question 27

Limnetic (pelagic) zone

Answer 27

the open water beyond the littoral zone, where the dominant photosynthetic organisms are floating algae (i.e., phytoplankton).

Question 28

Profundal zone

Answer 28

the area in a lake that is too deep to receive sunlight; typically has low concentrations of oxygen.

Question 29

Benthic zone

Answer 29

the area with sediments at the bottom of lakes, ponds, and oceans; is habitat for burrowing organisms.

Question 30

Epilimnion

Answer 30

the surface layer of water in a lake or pond.

Question 31

Hypolimnion

Answer 31

the deeper layer of water in a lake or pond; can include the lower limnetic profundal zone.

Question 32

Thermocline

Answer 32

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.

Question 33

Spring overturn

Answer 33

the vertical mixing of lake water that occurs in early spring, assisted by winds that drive the surface currents.

Question 34

Stratification

Answer 34

the condition of a lake or pond when the warmer, less dense surface water floats on the cooler, denser water below.

Question 35

Fall overturn

Answer 35

the vertical mixing that occurs in fall, assisted by winds that drive the surface currents.

Question 36

Fall bloom

Answer 36

a rapid increase in the population of phytoplankton in fall that occurs with the infusion of nutrients from fall overturn.

Question 37

Freshwater wetland

Answer 37

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.

Question 38

Swamps

Answer 38

contain emergent trees.

Question 39

Marshes

Answer 39

contain emergent non-woody vegetation.

Question 40

Bogs

Answer 40

contain acidic water and plants adapted to these conditions.

Question 41

Salt marshes

Answer 41

a saltwater biome that contains non-woody emergent vegetation.

Question 42

Where are salt marshes found?

Answer 42

Salt marshes are often found at continental coasts and in estuaries where the mouths of rivers mix with salt water from oceans.

Question 43

Mangrove swamps

Answer 43

a biome that occurs along tropical and subtropical coasts, and contains salt-tolerant trees with roots submerged in water.

Question 44

Intertidal zones

Answer 44

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.

Question 45

Coral reefs

Answer 45

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.

Question 46

Neritic zone

Answer 46

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.

Question 47

Oceanic zone

Answer 47

the ocean zone beyond the neritic zone; nutrients are sparse and production is limited.

Question 48

Photic zone

Answer 48

the area of the neritic and oceanic zones that contains sufficient light for photosynthesis by algae.

Question 49

Aphotic zone

Answer 49

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).