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AP Biology > Unit 5: Feedback and Response > Flashcards

Unit 5: Feedback and Response Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

regulator

A

an animal who, for a particular environmental variable, uses internal mechanisms to control internal change in the face of external fluctuation

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2
Q

conformor

A

for an environmental variable, the organisms internal condition changes with the environment

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3
Q

homeostasis

A

animals maintenance of internal balance and a relatively constant internal environment even when the external environment changes significantly

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4
Q

set point

A

a particular, healthy value of a variable that is maintained for an animal to achieve homeostasis

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5
Q

stimulus

A

fluctuations in a variable away from the set point which are detected by a sensor

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6
Q

sensor

A

detects stimulus, sends signal to control center which generates an output that triggers a response

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7
Q

response

A

a physiological activity that helps return the variable to the set point

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8
Q

negative feedback

A

a control mechanism that reduces a stimulus, products of a chain inhibit a previous enzyme

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9
Q

positive feedback

A

a control mechanism that amplifies, rather than reduces the stimulus
-does not play a major role in homeostasis but help drive processes (such as childbirth) to completion

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10
Q

regulated changes

A

normal changes in homeostasis that are necessary for normal bodily functions
ex- change in hormones during puberty

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11
Q

circadian rhythm

A

a set of physiological changes that occur roughly every 24 hours
-ex body temp and melatonin

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12
Q

acclimatization

A

the gradual process by which an animal adjusts to changes in its external environment

  • temporary changes during an animal’s life
  • may cause normal range of homeostasis to change
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13
Q

plant hormone

A

a signaling molecule that is produced in tiny amounts by one part of an organism’s body and transported to other parts, where it binds to a specific receptor and triggers responses in target cells and tissue.
-generally control plant growth and development by affecting the division, elongation, and differentiation of cells

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14
Q

tropism

A

any growth response that results in plant organs curving toward or away from stimuli

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15
Q

phototropism

A

plant growth toward or away from light

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16
Q

auxin properties

A
  • synthesized in plant tips and young leaves
  • developing seeds and fruit contain high levels
  • moves only from tip to base
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17
Q

Major Functions of Auxin

A
  • stimulates cell elongation withing developing shoots
  • rapidly alters gene expression and stimulates sustained growth response in region of elongation
  • plays a role in pattern formation (flow of auxin controls development of branches)
  • local peaks of auxin determine the site of leaf formation
  • polar transport from leaf margin directs the pattern of leaf veins
  • controls activity of vascular cambium which produces woody tissues
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18
Q

pattern formation

A

the spatial organization of a developing plant,

-Auxin plays a major role in it

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19
Q

Properties of Cytokinins

A
  • synthesized in roots and actively growing tissues
  • most common is zeatin
  • only have an effect when auxin is present
20
Q

Major Functions Cytokinins

A
  • regulate cell division in shoots and roots
  • plays a role in apical dominance
  • slows aging in plants by inhibiting protein breakdown, stimulating RNA and protein synthesis, and mobilizing nutrients from surrounding tissues
  • slows progress of apoptosis
21
Q

Properties of Gibberellins

A
  • produced in young roots and leaves

- embryo of seed is a rich source

22
Q

Apical Dominance

A

the ability of the apical bud (bud at tip of stem) to suppress the development of auxiliary buds

  • cytokinins, auxins, and strigolactones interact in its control
  • polar flow of auxin down the shoot triggers the synthesis of strigolactones, which repress bud growth
23
Q

Major Functions of Gibberelins

A
  • stimulate stem and leaf growth by enhancing cell elongation and cell division
  • in many plants, must be present along with auxin for fruit to develop
  • release of gibberellins, after water is imbibed, from embryo signals seed to germinate
24
Q

Brassinosteroids

A
  • produced in all plant tissues
  • induce cell elongation and division in stem segments and seedlings
  • slow leaf drop
  • promote xylem differentiation
25
Q

photomorphogenesis

A

the effects of light on plant morphology

  • plants detect the direction, intensity, and wavelength of light
  • red and blue light are most importent
26
Q

Blue-light photoreceptors

A

-initiates phototropism, light-induced opening of stomata, and slowing of hypocotyl elongating in seedlings
-three pigments involved
cryptochromes
phototrophin
zeaxanthing

27
Q

cryptochromes

A

blue light pigments that are involved in the inhibition of stem cell elongation

28
Q

phototrophin

A

-involved in mediating phototrophic curvatures

29
Q

zeaxanthing

A

involved in opening of the stomata

30
Q

Phytocromes and Seed Germination

A
  • a seed may germinate only when light is optimal
  • reverts back and forth between two isomers depending on color of light
  • Pr form absorbs red light maximally (increased germination)
  • Pfr absorbs far red light (inhibits germination, also triggers many of plants developmental response to light
  • ratio of Pfr to Pf increases in sunglight triggering seeds to germinate
31
Q

Phytocromes and Shade Avoidance

A

Pr-Pfr eventually reaches a dynamic equilibrium, with the ratio of each form indicating the relative amounts of red and far-red light

  • shade increases Pr ratio, stimulating a tree to grow taller
  • direct sunlight increases proportion of Pfr, stimulating branching and inhibiting vertical growth
32
Q

circadian rhythms

A

cycles with a frequency of 24 hours which are not directly controlled by any environmental variable

  • if an organism is kept in a constant environment, its circadian rhythm can vary from 21-27 hours
  • 24 period may arise from negative-feedback loops involving the transcription of a few central “clock” genes
33
Q

Effect of Light on Biological Clock

A
  • light is the factor that entrains the biological clock to precisely 24 hours every day
  • in darkness Pr formation is favored but as light increases Pr is suddenly converted Pfr
  • increase in Pfr at dawn resets biological clock
34
Q

Photoperiodism

A

a physiological response to photoperiod (the relative lengths of night and day)

35
Q

short day plant

A

a plant that requires a light period shorter than a critical length to flow
-usually blooms late summer - winter

36
Q

long-day plants

A

flower only when light period is longer than a certain length
-flower in late spring and early summer

37
Q

day-neutral plants

A

unaffected by photoperiod and flower when they reach a certain stage of maturity

38
Q

Critical Night Length

A

flowering responses are actually controlled by night length
-flowering of a short day plant can be stopped if the dark time is interrupted by a flash of light
-red light is the most effective at interrupting
-

39
Q

vemalization

A

the use of pretreatment with cold to induce flowering

40
Q

florigen

A

hypothetical signaling molecule for flowering

-macromolecule

41
Q

phyllotaxy

A

the arrangement of leaves on a stem

42
Q

meristem

A

plant tissue that remains embryonic as long as the plant lives, allowing for indeterminate growth

43
Q

abscisic acid (ABA)

A
  • present in all tissues
  • slows growth
  • play a role in all tissues ( high levels in maturing seeds inhibit germination and increase production of proteins that help seeds withstand dehydration)
  • drought tolerance; ABA accumulates in leaves, causing stomata to close
44
Q

properties of strigolactones

A
  • produced in roots

- upwardly mobile

45
Q

Major Functions of Strigolactones

A
  • stimulate seed germination
  • help establish mycorrhizal associations
  • help control apical dominance
46
Q

Ethylene

A
  • produced in response to stress
  • plays a part in triple response
  • burst of ethylene associated with apoptosis of cells during senescence
  • plays role in leaf abscission
  • a burst often triggers fruit ripening process

AP Biology (17 decks)

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