stimulus & response. stimulus achange in organism’s environment a change in organism’s...
TRANSCRIPT
Stimulus & Stimulus & Response Response
StimulusAA change in organism’s environmentchange in organism’s environment
Types of Stimuli A stimulus can either be external or internal.
External stimuli- come from factors found in the environment.
Examples- temperature, predators, presence of water or food, etc
Internal stimuli- come from factors within an organism
Examples- germs, dehydration, lack of energy, pain
Stimulus
Is this stimulus external or internal?
Response
An organisms reaction to change.
Response
HomeostasisHomeo- sameStasis- state of balance
The purpose of response to stimuli in organisms is to maintain homeostasis, a balance within it’s internal systems.
ExamplesExamples
StimulusStimulus = =
Is this internal or external?Is this internal or external? ResponseResponse = =
StimulusStimulus = =
Is this internal or external?Is this internal or external? ResponseResponse = =
Lack of water
Wilting
Bacteria or Virus
Fever
TropismsTropisms Tropism Tropism = plant’s growth response = plant’s growth response
toward or away from a stimulustoward or away from a stimulus
TropismsTropisms Tropism Tropism = plant’s growth response = plant’s growth response
toward or away from a stimulustoward or away from a stimulus
Positive tropismPositive tropism
Negative tropismNegative tropism
TropismsTropisms Tropism Tropism = plant’s growth response = plant’s growth response
toward or away from a stimulustoward or away from a stimulus
Positive tropismPositive tropism = plant grows toward = plant grows toward a stimulusa stimulus
Negative tropismNegative tropism
TropismsTropisms Tropism Tropism = plant’s growth response = plant’s growth response
toward or away from a stimulustoward or away from a stimulus
Positive tropismPositive tropism = plant grows toward = plant grows toward a stimulusa stimulus
Negative tropismNegative tropism = plant grows away = plant grows away from a stimulusfrom a stimulus
HydrotropisHydrotropismm
HydrotropismHydrotropism = a plant’s = a plant’s
rootsroots grow toward watergrow toward water
Is this positive or negative?Is this positive or negative?
PhototropismPlants grow toward a source of light
Animation:
http://botanical-online.com/animation8.htm
Examples
ThigmotropismA plant grows toward or away from pressure
Positive turns toward pressure
Negative turns away from pressure
Geotropism A plant grows with or against gravity Also called Gravitropism
Negative- A plant’s stems or trunk grow up, against the pull of gravity.
Positive- A plant’s roots grow down, with the pull of gravity
Animation:
http://botanical-online.com/animation4.htm
Regardless of the slope of the land, the tree grows up against gravity.
Regardless of the position a seed is planted in, the roots grow down with gravity and the stem up against gravity.
Working Together
Plant tropisms work together to maintain homeostasis within the plant
- geotropism
+ phototropism
+ geotropism
+ hydrotropism