chapter 4 Flashcards
Effects of Gravity
animals
-internal skeleton
-external skeleton
fungi
-cell walls of chitin
plants
-cell walls of cellulose
Land Constraints
gravity
nutrient acquisition
dessication
thermoregulation
Soil
basis of terrestrial ecosystem
medium for plant growth
initial recipient of water, controlling its fate
recycling system
a habitat
both abiotic and biotic
has depth, length and width
Soil Definition
solid substrate of terrestrial communities resulting from the interaction of weather and biological activities with the underlying geological formation
Soil Layers
Organic Layer
Topsoil
Subsoil
Unconsolidated Material
Organic Layer
O Horizon
-dominated by organic material
-consists of undecomposed or partially decomposed plant materials such as dead leaves
Topsoil
A Horizon
-largely mineral soil developed from parent material
-organic matter leached from above gives the horizon a distinctive dark color
Subsoil
B Horizon
-accumulation of mineral particles such as clay and salts leached from topsoil
-distinguished based on color, structure, and kind of material accumulated from leaching
Unconsolidated Material
C Horizon
-derived from the original parent material from which the soil developed
Weathering
how soils are formed
-process whereby parent rock is broken down by physical and chemical processes
Mechanical Weathering
-results from the interaction of water due to it seeping into crevices
-results from temperature, water freezing and expanding which can break the rock into smaller pieces
-results from wind scouring the surface with dust and sand
-results from organisms’ plant roots splitting rocks
Chemical Weathering
chemically alters and breaks down rock and minerals
-soil organisms activities produce water, oxygen and acids
-organism material from dead organisms or shed tissues
Five Interrelated Factors for Soil Formation
-parent material
-biotic factors
-climate
-topography
-time
Water Potential
capacity to perform work
dependent on free energy content
Water Movement
water potential pie
-reduction in water potential due to dissolved substances
water potential m
-reduction in water potential due to Matric Forces
water potential p
-reduction in water potential due to negative pressure created by transpiration and changed in turgor pressure
-as long as water potential in plants is less than water potential in soil water flows from the soil to the plant
Field Capacity
water held within the soil by internal capillary forces
varies with texture
lower in coarse soils
higher in fine soils
Wilting Point
soil moisture level below which plants can no longer extract water
water present but held too tightly
Soil Texture/Classification
Sand- 0.05 to 2.0 mm which is easy to see
Silt- 0.002 to 0.05 mm which is difficult to see with the naked eye
Clay-less than 0.002 mm which is microscopic
Ideal Soil
50% soil particles, 50% pore space
-pore space includes spaces within and between soil particles
-old root channels
-animal burrows
Clay and Humus
-influence nutrient content
-ability to hold minerals
-attraction to micelle influence leached mineral
-potassium and calcium ions leach easily
Soil pH
-higher H concentration increases leaching
Water Transpiration
-water vapor lost from leaves
-water moves to equalize osmotic pressure
Transpirational Pull
-force or tension in leaves due to transpiration
-affects water column in Xylem
-acts as lower atmospheric pressure
Water Movements in Plants
-movement goes from areas of higher water potential to lower potential
