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AP Bio- Regulation 7: Responses
Transcript of AP Bio- Regulation 7: Responses
How do feedback loops help organisms respond to the environment?
How are behavioral feedback loops coordinated among multiple mechanisms in an organism?
Feedback At Work:
Photo Reponses In Plants
Circadian & Seasonal Responses in Animals
Growth in response to a light source.
Mediated by the hormone
How Auxin Works:
Activates proton pumps, which pump H+ into the cell wall.
, which elongate the cell wall.
Not all wavelengths of light are created equal in plant responses
How can this be explained?
Both Hibernation and Migration are triggered & regulated by changes in physiology & day length.
Why are these responses necessary?
Even absent environmental cues, hibernation occurs in many animals (“
Data from squirrels kept in constant lighting in a lab for two years:
24-hour behavioral cycles are mediated by environmental cues acting on physiology (e.g. melatonin levels)
Jet lag ("desynchronosis") seems to result from confusion between environmental signals (sunrise and sunset) and internal hormonal cues.
Fruiting bodies (spore producing structures) are only created in response to environmental signals (food availability) and signals from other cells.
Quorum Sensing in Prokaryotes
Quorum sensing is a mode of group response that relies upon determined actions once certain thresholds are reached.
Bacterial colonies can change their behavior once certain population densities occur.
The trigger for these responses is the presence of signaling molecules in threshold concentrations in the environment.
These molecules serve as operon regulators
Biofilms are aggregate mats of bacteria held together by secreted polymers.
Your mouth is full of biofilms:
Signaling in Animal Populations
Pheromones are chemical signals that transmit information between organisms.
Widely used in many lineages of animals.
Reproductive responses are triggered by a variety of physiological and environmental cues.
These responses usually involve visually ostentatious displays (“mating behaviors”)
Explain how organisms can incorporate signals from the environment into physiological feedback loops.
Explain how behavioral feedback loops are coordinated among multiple physiological systems.
Make Sure You Can:
controls cell division & differentiation
-growth towards light
asymmetrical distribution of auxin
cells on darker side elongate faster than cells on brighter side (due to auxin accumulation in darker side cells)
Taxis & Kinesis are controlled by negative feedback loops in response to environmental stimuli.
The changes in motility of cells in response to chemical signals.
Taxis & Kinesis
Changes in organism behavior due to the length of day or night.
A Flowering Hormone?
Positive or Negative Feedback?
Can be from:
Tends to involve:
3. Effecting of Response
(Use of sensory organs)
(Use of nervous/endocrine system)
(Use of muscles, glands)
Cellular: Change in Gene Expression, metabolism, transport, etc.
Complexity Will Emerge!
seed germination in response to light
flowering responses in "
" and "
Normal melatonin cycle in humans:
The role of the Superchiasmatic Nucleus (SCN) in controlling CR in mammals
Why feed instead of eat?
Visual Displays in a Human Sub-population
Body Temperature & Metabolism
in Belding's Ground Squirrels
= Actual Rate
= Theoretical (nonhibernatory) rate
Black = Body Temp.
= Burrow Temp.
= Outside Temp
Pheromone-controlled behavior can get wildly complex: