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30 Cards in this Set
- Front
- Back
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How much rainfall is there in deserts?
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Less than 25 cm per year
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How is the precipitation evaporated?
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High solar radiation
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Why are many animals and plants confined to moist areas?
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Because of their limited capacity to reduce water loss
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How is the life of organisms in deserts controlled?
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By water supply and scarcity of food
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What can be said of the periods of adequate water and food abundance in deserts?
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timing and duration is unpredictable
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What is Liebigs law of the minimum?
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The development of a population in deserts is regulated By the substance occurring in minimal quantity relative to the requirement of the population
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What is Shelfords law of tolerance?
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For each environmental factor, organisms have an ecological minimum and maximum, with a range in between which represents the tolerance of that organism to that environmental factor.
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What does Sub-optimal conditions lead to?
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A reduction in growth and reproduction and an increased chance of mortality
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What is a terrestrial organism`s thermal environment determined by?
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Radiation, Conduction, convection and evaporation
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Are diurnial and seasonal temperatures fluctuations greater or smaller in terrestrial or aquatic environments
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Greater in terrestrial
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What can organisms divided into?
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Endotherms and echtotherms
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What are Endotherms
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They regulate body temparatures effectively
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What are Echtotherms?
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The use less energy, but have activity restricted to periods of suitable ambient periods
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What are the influence of environmental factors on organisms reduced through?
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Structural, physiological and behavioural adaptations
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What is pedogenesis?
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Soils arise from weathering of parent rock material and through the deposition of plant and animal remains.
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What is a soil profile?
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A section through the soil from the surface to the underlying parent rock
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What does the uppermost layer consist of?
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Litter and decomposing organic material
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What is the A-horizon
zone of eluviation B-horizon zone of illuviation |
The topsoil where the products of decomposition are leached down to the B-horizon.
The A-horizon becomes enriched with resistant minerals, ed the B-horizon becomes enriched with the leachates |
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What is the C-horizon
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Weathered rock or sediment that serves as parent material
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What does it mean that soil is saturated
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The pores between soil particles are filled compeletely
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What is water that percolates through the soil called?
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Gravitational water
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What is the field capacity of a soil
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The maximum water content that soil can hold against gravity
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What does most plants obtain from the soil
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the water, mineral and nutrients that are essential for growth and metabolism
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What may an inadeqaute supply of any essential element cause?
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Reduce the growth and may result in deficiancy disease
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How can sessile organisms survive all seasonal changes in their environment?
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Through adaptation or as resistant propagules
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What happens to perennial plant frequency when rainfall becomes more predictable?
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It increases
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What do desert animals tend to be?
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Opportunistic, generalist feeders (Specialists are rare)
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What is desertification
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Form of land degredation that results from clearing natural vegetation for cultivation, harvesting woody species for fuel and overgrazing
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What does the reduction in plant cover cause?
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makes deserts more susceptible to erosion by wind and water (Cultivation results in reduced soil fertility and irrigation raises soil salinity
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