Cuticle
upper
epidermis
-xylemlcd
palisade
mesophyll
spongy
mesophylla
phloemful
{
aan ea
lower
epidermis
stoma
g uard cells
Stomata are tiny openings found in plant leaves. Specialized cells known as guard cells surround the stomata and open and close
the openings. When it is very hot, plants may close their stomata to prevent water loss. When plants close their stomata, what else
is affected?
Plants cannot take in the carbon dioxide they need for photosynthesis.
Plants cannot take in the sunlight they need for photosynthesis.
Plants cannot release glucose made in photosynthesis.
D)
Plants cannot take in water from the air.

what's the

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).