Chapter 7: Adaptations to Terrestrial Environments

parent material

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

leaching

groundwater removes some substance by dissolving them and moving them down through soil layers

whats leaching like in places with little rain fall?

parent material breaks down slowly and there’s little organic matter so they have shallow soil with close bedrock

weathering

physical and chemical alteration of rock material near earths surface

when does weathering occur?

whenever surface water penetrates the parent material

rank these in size of largest to smallest:

-clay

-sand

-silt

sand> silt > clay

why do soils with a high proportion of clay particles hold more water on their surfaces?

they have a larger total surface area

why do soils with a high proportion of sand particles tend to dry out?

water drains quickly away leaving air pockets

why does clay make it hard for plants to extract water?

hold water molecules super tight

what is the best soil for plants?

loam which contains clay, silt, and sand

water potential

the force with which a plant tissue attracts water measured in units of pressure

water potential vs. osmotic

osmotic potential is a contributing fcator to water potential

matrix potential

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

is a strong matrix potential positive or negative?

negative

if soil is really dry does it have a negative or positive matrix pull and why?

negative

what does it mean for the matrix potential when water is plentiful?

most of the water molecules are not close to the surface of soil particles therefore they’re held loosley by electrical attraction and roots can take up more water= high matrix potential

what does it mean for the matrix potential when water is used up?

it remains tight to the soil particles so the electrical reaction is strong so its difficult for the roots to take up water

field capacity

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

When does field capacity occur?

after excess water has drained away due to gravity

wilting point

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

stomata

small opening on surface of leaf that is entry for CO2 and exits for water vapor and oxygen

what does the stomata do during the day?

it opens and loss of water causes water potential to become negative which pulls water from soil

when the soil dries to the point of wilting what does the stomata do?

it compeletly closes which protects the plant from losing too much water but also stops photosynthesis

what is this chart explaining?

clay soil holds a lot of water but due to negative matrix potential it has a high wilting point

sand soil doesn’t hold a lot of water so it has a lower field capacity but due to weak matrix potential its easier for plants to access thus giving it a lower wilting point

besides oxygen, carbon, and hydrogen, what other nutrients does soil require?

nitrogen, phosophorous, calcium, and potassium

how are these ions obtained?

they dissolve from water

what kind of charges on clay soil and organic matter allow ions such as Ca2+, Mg2+, K+, and Na+ attract?

negative charges

What happens to water movement if a plant's root cells have a higher solute concentration (giving them a lower water potential) than the surrounding soil matrix?

If a plant is growing in severely dry or highly saline soil, the soil matrix potential becomes extremely low. If this makes the soil's water potential lower than the root cells' water potential, what happens?

To successfully absorb water from the ground, do a plant's roots need a higher or lower water potential than the surrounding soil matrix?

If a soil has a higher water potential than a plant's roots, does the soil have a higher or lower concentration of free, unbound water molecules compared to the roots?

1) water flows into root

2) water flows out from the roots to the soil

3) lower water potential (osmosis)

4) higher concetration of free water molecules

what 2 adaptations do root cells possess that prevent the equalization of solute concentrations in the cell and soil water?

1) semipermeable cell membranes that prevent larger molecules against the concentration gradient into the root cells

2) cell membranes actively transport ions and small molecules against the concentration gradient into root cells

what does the 2nd adaptation allow the plant to do?

have high solute concentration inside the roots to keep osmotic force strong to allow water to move to roots

for plants in the desert that have strong matrix potentials, what adaptations have they evolved?

they can increase the concnetrations of amino acids, carbs, or organic acids

soil salinization

the process of repeated irrigation which causes increased soil salinity

how can soil salinization pose a porblme to plants?

theres more salt in the soil and thus the matrix potential is stronger making it harder to plants to pull water

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 leaves

how is trabspiration used to move water from soil into roots?

Water evaporates from leaf → pulls water upward → more water enters roots from soil

cohesion-tension theory

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

chloroplasts

specialized cell organelles in which photosyntehsis occurs in plants

photosynthesis

process of combining CO2 and H2O and solar energy to produce glucose

light reactions

convert energy from photons into chemical energy

3 steps of light reactions

1) chlorophyll absorbs photons

2) the energy from photons is used to generate ATP and NADPH

3) in the process oxygen in H2O is released as O2

dark reactions

use chemical energy to make sugar from CO2 using energy in ATP and NADPH to convert CO2 into glucose

whats the process in dark reactions called?

calvin cycle

what 3 biochemical pathways have evolved in the calvin cycle?

1) C3

2) C4

3) CAM

C3 photosynthesis

CO2 and 5 carbon sugar known as RuBP produces a 2 molecules of glyceraldehyde 3-phosphate (G3P) known as Rubisco which is catalyzed by RuBP carboxylase oxidase

what 2 disadvantages does C3 photosynthesis have?

1) rubisco is inefficient since it has a low affinity for CO2 so they must pack their cells with lots of rubisco

2) rubisco also reacts with O2 resulting in photorespiration

photorespiration

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

why does photorespiration become more problematic in hot an dry conditions?

when stomata is partially closed to conserve water CO2 concentrations in leaves will be low making rubisco more likely to bind to O2

what are the solutions to this problem?

C4 and CAM photosynthesis

C4

CO2 is initially assimilated into a 4 carbon compound (oxaloacetic acid) which is catalyzed by PEP carboxylase

why is PEP carboxylase more efficient?

it has a higher affinity for CO2

what do plants in C4 photosynthesis must do?

must move CO2 into the mesphyll cells over to t ebundle sheath cells

where does calvin cycle occur in C4 and whats the benefit?

bundle sheath cells which creates CO2 concnetrations so much higher than C3

what are the 2 disadvantages of C4?

1) fewer leaf cells used for calvin cycle

2) energy produced by light reactions is used in the intitial C4 assimilation step via the CO2 pump

CAM

the initial assimilation of carbon into 4 carbon compound occurs at night

insteas of separaing CO2 assimilation and the Calvin cycle spatially., what does CAM do?

separates the steps into time

what happens to CAM plants during the night?

the stomata opens during the night where cool and humid conditions slow transpiration and then conduct photosynthesis during the day

what photosynthesis is better adapated to warm and arid conditions?

C4 and CAM

what photosynthesis is better adapted to cool, wet conditions?

C3

what are the 2 reasons as to why plants living in arid conditions have either shallow or deep roots?

1) shallow roots, such as cacti, are able to take water rapidly in brief rain events when water doesn’t penetrate soil very far

2) plants with deep roots extend meters down to access water that is far below the surface

what leaf adapations have evolved to trap moisture?

water cuticles, spine and hairs that produce boundary later, deep recessed stomata, subdivided leaves, embolism

embolisms

high density of large veins in small leaves

what happens to veins of leaves in severe drought?

under severe drought stress air can flow into the stomata and travel into large veins causing a bubble to form and block water movement

how does embolism combat this problem?

large density of veins allows water to be sent through adjacent veins

what are the 4 mechanisms in which organisms gain and lose heat from the environment?

1) radiation

2) conduction

3) convection

4) evaporation

radiation

emission of electromagnetic energy by the surfaces

as objects in ladscpe are warmed by solar radiation what happens as result?

then in turn emit lower energy radiation in form of heat

radiation example:

yuh

conduction

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

what 3 factors doe steh rate at which heat moves by conduction rely on?

1) organisms surface area

2) insulation of organism

3) tenmperature difference between substances

the rate is heat loss is higher when what for conduction?

when theres a larger difference between the temp of organism and enviornment

conduction example

lizard basking in sun

convection

the transfer of heat by the movement of liquid and gases

process of convection

boundary layer of air forms over a surface of organism when air isn’t moving but if wind currents disrupt the boundary layer head can be carries away

what do mammals do to thicken boundary layer to retard heat loss?

raise hair

evaporation

the transofrmation of water from a liquid to a gas with the input of energy which removes heat from a surface

evaporation example

kangaroos in hot desert lick their legs such that their saliva can evaporate and have cooling effect

since volume increases fast than surface area, so larger organisms have a higher or lower SA;V ration?

lower

what does a lower SA:V ratio mean for an animal?

they have less surface area relative to amount of tissue inside so heat move in and out more slowly

what conclusion can we draw about larger organisms when it come to heat regulation?

gain and lose heat more slowly

thermal inertia

the resistsance to change in temp due to large body volume

thermoregulation

The process by which an organism controls the temperature of its body

homeotherms

organisms maintain constant temp

example of homeotherms

mammals and humans

poikilotherms

organisms that don’t have constant body temps

poikilotherms example

amphibians who body temps drops in cold water and warms on hot rock

endotherm (EN→ IN→ INTERNAL)

organism that can egenrate sufficient metabolic heat to raise body temo highr than external enviornment

disadvantage of endotherms

sustaining internal temps require slots of energy

ectotherms

organisms with body temps largely determined by external enviornment

what do Hoemotherms vs. poililotherms ask?

does the body temp stay constant or fluctuate?

what do Endotherms vs. ectotherms ask?

where does the heat come from?

homeothermic and ecto thermic

polikiothermic and endotehrmic

blood shunting

blood vessels shut off at extremities so that less of the animals warm blood flows out to extremities and is redirected in the veins to allow core to stay warmer and expend less energy

countercurrent circulation

arterie sthat carry warm blood away from the heart toward extremities are positioned alongside veins that carry chilled blood frm teh extremtities to the heart so that heat from arteries are transfered to veins

what happens if concurrent exchnage happened?

• Initially the temperature difference between arterial blood adjacent venous blood is large so a lot of heat transfer occurs

• However, once the arterial and venous blood temps are the same no more heat transfer occurs

• As a result the venous blood has recovered much less heat than in countercurrent exchange