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Chapter 4

BIOL150 Chapter 4: Biol 150 Chap 4 The Terrestrial Environment

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Rebecca Rooney

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Biology 150 Chapter 4 The Terrestrial Environment
Organismal and Evolutionary Ecology Reading notes
4.1 Types of Terrestrial Ecosystems
- Biomes: broad-leaved evergreen forests, deserts, and grasslandsmajoring
groupings of plant and animal communities defined by a dominant vegetation type
- The type of biome depends on climate. (Temperature, moisture, sunlight and wind:
wind increases heat loss due to evaporation and convection, and it increases water
loss due to evaporation and transpiration, is also a physical impact for birds and
- The nature of biome is governed by (1) average annual temperature and
precipitation and (2) annual variation in temperature and precipitation
- Net primary productivity (NPP): total amount of carbon that is fixed per year minus
the amount that is oxidized during cellular respiration, represents the organic matter
that is available as food for other organisms
- Biomass: fixed carbon that is being consumed in cellular respiration provides energy
for the organism but is not used for growth
- Above-ground biomass: the total mass of living plants, excluding roots
- Photosynthesis, plant growth, and NPP are maximized on land when temperatures
are warm and conditions are wet
- Photosynthetic rates are maximized in warm temperatures when enzymes work
efficiently and in humid weather when stomata can remain open and carbon dioxide
is readily available
4.2 Tropical Wet Forest/Tropical Rainforest
- Equatorial regions
- Plants have broad leaves and evergreen. Older leaves are shed throughout the year,
but no complete, seasonal loss of leaves
- Temperature
High average temperature and very low variation throughout the year
- Precipitation
High precipitation, high variationthere are dry months but still have more
rainfall than other biomes like deserts
- Vegetation
High productivity, favourable year-round growing conditions
Structural diversity
Canopy: the uppermost layers of branches; distinctive and continuous
Complex assortments of vines, epiphytes (plants that grow entirely on other
plants), small trees, shrubs, and herbs
4.3 Subtropical Deserts
- 30 degrees latitude, or distance from the equator, both north and south
- Sahara, Gobi, Sonoran Deserts and the Australian outback
- Temperature
High average temperature, moderate variation
- Precipitation
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Biology 150 Chapter 4 The Terrestrial Environment
Organismal and Evolutionary Ecology Reading notes
Very low annual rainfall: 7.5 cm, low variation
- Vegetation
Very dry and limited water for photosynthesis
Low productivity
Individual plants are widely spacedintense competition for water
They species adapt to the extreme temperatures and aridity in one of two
ways: (1) growing at a low rate year-round or (2) breaking dormancy and
growing rapidly in response to any rainfall
Cacti can grow year-round because they possess adaptations to cope with
hot, dry conditions: (1) small leaves or no leaves (photosynthetic cells are
located in stems); (2) a thick, waxy coating on leaves and stems; (3) the CAM
pathway for photosynthesis.
Desert shrubs called ocotillo, are dormant: individuals sprout leaves within
days of a rainfall and drop them a week or two later when soils dry out again.
The seeds of annual plants can also lie dormant for many years then
germinate after a rain
4.4 Temperate Grasslands
- Central North America and the heartland of Eurasia. They are called prairies in North
America, and steppes in Eurasia
- Temperature
Temperate: typically hot summers and cold winters
Moderate annual average temperature
Moderate variation dictates a well-defined growing season
Plant growth is possible only in spring, summer and fall
- Precipitation
Annual precipitation is low83.4 cm, moderate variation
- Vegetation
Grasses are the dominant life form for one of two reasons: (1) conditions are
too dry to enable tree growth or (2) encroaching trees are burned out by fires
Fires are ignited by lightning strikes or by people managing land for animals
that graze on grasses and herbaceous (non-woody) plants
Plant life is dense
Productivity lower than forest communities, but grassland soils are often
highly fertilethe subsurface is packed with roots and rhizomes, which add
organic material to the soil as they die and decay, grassland soils retain
nutrients because rainfall is low enough to keep key ions from dissolving and
leaching out of the soil
Ideal for growing wheat, corn, and other cultivated grasses
4.5 Temperate Forests
- Eastern North America, Western Europe, East Asia, Chile, and New Zealand
- Temperature
Moderate annual average temperature with moderate variation
- Precipitation
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