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AP Bio- Regulation 7: Responses

7 of 7 of my Regulation Unit. Image Credits: Biology (Campbell) 9th edition, copyright Pearson 2011, & The InternetProvided under the terms of a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. By David Knuffke
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David Knuffke

on 26 June 2015

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Transcript of AP Bio- Regulation 7: Responses

Responses
Big Questions:
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:
Example 1:
Photo Reponses In Plants

Example 2:
Circadian & Seasonal Responses in Animals

Phototropism
:
Growth in response to a light source.
Mediated by the hormone
auxin
in plants.
How Auxin Works:
Activates proton pumps, which pump H+ into the cell wall.
This activates
expansins
, which elongate the cell wall.
Not all wavelengths of light are created equal in plant responses

How can this be explained?
Hibernation/Migration
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 (“
obligitative hibernation
").
Data from squirrels kept in constant lighting in a lab for two years:
Circadian Rhythms
:
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.
Example 4:
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:
Example 5:
Signaling in Animal Populations

Pheromones are chemical signals that transmit information between organisms.

Widely used in many lineages of animals.
Visual Displays:
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:

Effects
controls cell division & differentiation
phototropism
-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)
apical dominance
Taxis & Kinesis are controlled by negative feedback loops in response to environmental stimuli.
Cellular Level:
The changes in motility of cells in response to chemical signals.
Example 3:
Taxis & Kinesis

Photoperiodism
:
Changes in organism behavior due to the length of day or night.
Phytochromes!
A Flowering Hormone?
Positive or Negative Feedback?
Organism
Environment
Response
Stimulus
Can be from:
Abiotic Source
Biotic Source
Other cells
Tends to involve:
Organism:
1. Reception
2. Integration
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 "
short day
" and "
long day
" plants
Normal melatonin cycle in humans:
The role of the Superchiasmatic Nucleus (SCN) in controlling CR in mammals
Any Questions?
Why feed instead of eat?
Visual Displays in a Human Sub-population
Body Temperature & Metabolism
in Belding's Ground Squirrels
35 C
25 C
15 C
5 C
-5 C
-15 C
June
Sep.
Dec.
Mar
Metabolic
Rate
100
kcal/day
0
kcal/day
Yellow
= Actual Rate
Orange
= Theoretical (nonhibernatory) rate
Temp.
Black = Body Temp.
Green
= Burrow Temp.
Blue
= Outside Temp
Auxin
Pheromone-controlled behavior can get wildly complex:
Full transcript