ch 4 terrestrial environments

soil

layer of chemically and biologically altered material that overlies bedrock or other unaltered material at Earth’s surface

parent material

the layer of bedrock that underlies soil and plays a major role in determining the type of soil that will form above it

horizon

a distinct layer of soil

leaching

a process in which groundwater removes some substances by dissolving them and moving them down through the soil to lower layers

weathering

the physical and chemical alteration of rock material near Earth’s surface

water potential

a measure of water’s potential energy which indicates its tendency to move from one area to another

matric potential

the potential energy generated by the attractive forces between water molecules and soil particles

field capacity

the maximum amount of water held by soil particles against the force of gravity

wilting point

the water potential at which most plants can no longer retrieve water from the soil

cation exchange capacity

the ability of a soil to retain cations

soil salinization

the process of repeated irrigation which causes increased soil salinity

cohesion

the mutual attraction among water molecules

transpiration

the process by which leaves can generate water potential as water evaporates from the surfaces of leaf cells into the air spaces within the leaves

cohesion-tension theory

the mechanism of water movement from roots to leaves due to water cohesion and water tension

stomata

small openings on the surface of leaves which serve as the points of entry for CO2 and exit points for water vapor

RuBP carboxylase oxidase

an enzyme involved in photosynthesis that catalyzes the reaction of RuBP and CO2 to form two molecules of glyceraldehyde 3-phosphate. Also known as rubisco

C3 photosynthesis

the most common photosynthetic pathway, in which CO2 is initially assimilated into a three carbon compound, G3P

Photorespiration

the oxidation of carbohydrates to CO2 and H2O by rubisco, which reverses the light reactions of photosynthesis

C4 Photosynthesis

A photosynthetic pathway in which CO2 is initially assimilated into a four carbon compound, oxaloacetic acid

Crassulacean metabolism (CAM)

a photosynthetic pathway in which the initial assimilation of carbon into a four carbon compound occurs at night

Negative feedback

the action of internal response mechanisms that restores a system to a desired state, or set point, when the system deviates from that state

radiation

the emission of electromagnetic energy by a surface

independent variable

a factor that causes other variables to change

dependent variable

a factor that is being changed

continuous variable

a variable that can take on any numeric value, including values that are not whole numbers

categorical variable

a variable that falls into a distinct category or grouping. Also known as nominal variable

conduction

the transfer of heat between substances that are in contact with one another

convection

the transfer of heat by the movement of liquids and gasses

evaporation

the transformation of a liquid to a gas with the input of heat energy

thermal inertia

the resistance to change in temperature due to a large body volume

blood shunting

an adaptation that allows specific blood vessels to shut off so that less of an animal’s warm blood flows to the cold extremities