Chapter 4: Coping With Environmental Variation

Front 1

The Liebig Law of Minimum

Back 1

under stable conditions, the essential constituent available in amounts most closely approaching the minimum need tends to be the limiting one

Limiting Factor / Condition

factor substitutions / modifications can offset minor deficiencies

Front 2

Shelford Law of Tolerance

Back 2

not only too little, but too much of a limiting factor may be harmful

more tolerant organisms more widely distributed

unfavorable effects from one factor may reduce other factors tolerance

a factors net effect may be a combination of factors

life stage changes can change factor tolerances

Front 3

Ecotypes

Back 3

genetically different subspecies populations adapted to specific environment

Front 4

Organisms have two options for coping with environmental variation

Back 4

1.) Tolerance

2.) Avoidance

Front 5

Physical environment influences an organism’s success

Back 5

Availability of energy and resources - impacts growth and reproduction

Extreme conditions can exceed tolerance limits & impact survival

Energy supply

Geographic distribution of a species - disturbance and competition

Front 6

Why are plants good indicators of the physical environment?

Back 6

Do Not move

Front 7

Climate envelope

Back 7

range of conditions over which it occurs

useful tool for predicting its response to climate change

Front 8

Consequences of ranging outside optimum envelope

Back 8

Stress (environmental change)

results in decreased rates of physiological processes, lowering survival potential, growth, or reproduction

Front 9

Acclimatization

Back 9

adjusting to stress through behavior or physiology

usually a short-term, reversible process

Front 10

Soil

Back 10

weathered layered of earth’s crust with living organisms intermingled with products of their decay

depends on climate

Front 11

Benefits of soil

Back 11

site of decomposition

liberated chemicals become available to primary producers

Front 12

Rhizospheres

Back 12

aggregations of microbes around pellets, patches of organic matter, & mucus secretions

account for 90% of metabolic activity in soil

account for 10% soil volume

Front 13

Soil structure

Back 13

A Horizon - top soil, organic rich layer

A0 - detrital layer

A1 - humus layer

A2 - leached layer

B Horizon - fine particle size mineral rich layer

C Horizon - unweathered parent rock material

Front 14

Factors that influence soil structure

Back 14

Climate

Topographic features (forest vs. grassland)

Texture - grain size distribution (sand, slit, clay)

Organic content - proportion of organic matter

Exchange capacity - amount of exchangeable nutrients (availability)

Front 15

2 groups of soils

Back 15

mature soil - flat land soil controlled by climate & vegetation

immature soil - topographically, water, or source rock controlled

Front 16

Soil erosion

Back 16

loose soil faster than it is formed

from natural and anthropogenic means

movement of material from one area to another by the action of water or wind

Front 17

Consequences of soil erosion

Back 17

decrease in soil productivity

increase in pollution

decrease in crop production

Front 18

Temperature variation

Back 18

temp. of organisms is determined by exchanges of energy with external environment

Organism must tolerate temp. change or modify their physiological, morphological, or behavioral tactics

Enzymes/proteins denature & become nonfunctioning - inhibits cellular processes, leading to stress in organism

Front 19

3 ways energy exchange btw organism & environment occur

Back 19

1.) Conduction - transfer energy from warmer to cooler molecules

2.) Convection - heat energy is carried by moving water or air

3.) Radiation - transfer of energy associated with electromagnetic energy

Front 20

Factors of temperature change in plants

Back 20

Control transpiration rates - varying degree of opening & # of stomates

Shed leaves during dry seasons

Pubescence hairs - leaf surfaces structures that reflect solar energy

Heat lost by convection so plants hug the ground

Front 21

Ectotherms

Back 21

regulate body temp. via energy exchange with external environment

can move to adjust temp. (+ temp. regulation, - exposure to predators)

Front 22

Endotherms

Back 22

maintain constant body temp. independent of external environment

high demand for energy (food) to support metabolic heat production

insulation - feathers, fur, and fat; limits conductive and convective heat loss

Front 23

Surface area to volume ratio ectotherms

Back 23

important energy exchange potential

as body size increases, surface area to volume ratio decreases (large ectotherms improbable)

Front 24

Surface area to volume ratio endotherms

Back 24

small endotherms with large surface area to volume ratio = higher metabolic rates, & require more energy, and higher feeding rates than large endotherms

Front 25

Torpor

Back 25

Short hibernation period; dormant state

allows small mammals that have thin fur & little fat for energy storage survive in cold climates

Front 26

Hyperosmotic

Back 26

more saline than an organism’s cells

terrestrial organisms - lose water to dry atmosphere

Front 27

Isoosmotic

Back 27

same salinity as an organism’s cells

marine organisms (water balance not a problem)

Front 28

Hypoosmotic

Back 28

less saline as an organism’s cells

freshwater organisms - lose solutes to & gain water from environment

Front 29

3 factors that compromise water potential

Back 29

1.) Pressure - from area of high pressure to lower; associated energy is pressure potential (turgor)

2.) Osmotic potential - water flows from region of high concentration to a region of low concentration (low solute concentration to high solute concentration)

3.) Matric potential - energy associated w/ attractive forces on surfaces of large molecules inside cells or on surface of soil particles

WATER POTENTIAL = SUM OF THESE ENERGY COMPONENTS

Front 30

Terrestrial plants strategies of coping with water variation

Back 30

barriers impede water loss (waxy,thicker cuticle)

take up water from soil to replace water lost to atmosphere

some form resistant spores to tolerate low water / dry habitats

Front 31

Water loss regulation in plants

Back 31

Shed leaves in dry seasons to reduce transpirational water loss

Hormonal signals to signal stromates to close

Acclimatize by altering root growth to match soil moisture & nutrients

Front 32

Water balance in animals

Back 32

specialized organs for gas exchange, excretion, solute retention (lessens water loss)

move to environments to maintain water balance

Front 33

Marine plants strategies for coping with water variation

Back 33

take up water from sources with higher water potentials

Front 34

Freshwater plants strategies for coping with water variation

Back 34

solutes in cells create the water potential gradient

Front 35

Water variation marine animals

Back 35

tend to be isoosmotic to seawater

some exchange solutes with the environment to retain osmotic balance (marine bony fishes have blood that is hypo osmotic to seawater so tend to loose water and gain solutes)

Front 36

Water variation freshwater animals

Back 36

hyperosmotic to the water so tend to gain water and lose salts

Front 37

Water variation terrestrial animals

Back 37

exchange gases with a dry environment

evaporative water loss is minimized by skin resistance and/or by living in moist environments

amphibians - moist habitats; gas exchange through skin

reptiles - thick skin with layers of dead cells, fatty coatings, and plates/scales to minimize water loss

Fur/feathers minimize water loss