HOMEOSTASIS AND
BEHAVIOR NOTES
EQ: How does an organism’s
behavior help it to maintain
homeostasis?
What is behavior?
■Stimulus:
– Anything that causes a reaction or a
change in an
organism
■Response:
– An organism’s
reaction to a
stimulus
What is behavior?
■Behavior:
– A set of actions taken by an
organism in response to a stimulus
■Homeostasis:
– Maintaining a stable
balance
How are stimuli detected?
■Multicellular organisms have sensory
cells that detect specific stimuli
■Sensory Receptors:
– Found in sensory organs
– Eyes, Nose, Skin, and Ears
Where do responses come
from?
■Sensory Receptors detect stimuli and send
messages through the Nervous System
■Hormones:
– Chemical signal produced in one part of
the organism that affects cell activity in
another part of the organism
What is an External Stimulus?
■Any stimulus that comes from outside
the body of an organism
■Influences the behavior of
the organism
■Examples:
– Temperature, sound, and light
What is an External Stimulus?
■Phototropism:
– Plant’s response to
light
■Geotropism:
– Plant’s response to
gravity
What is an Internal Stimulus?
■Any stimulus that comes from inside
an organism’s body
■Examples:
– Metamorphosis (insects)
– Puberty (humans)
How does homeostasis work?
■Constantly responding to internal and
external stimuli
■If the body cannot
maintain
homeostasis…
– Illness or disease
may occur
What are some behaviors that
improve survival?
■ Fight or Flight Response
– When faced with a threatening stimulus
(predator or natural disaster)…
– Organisms will respond to by either fighting or
running away
■ Organisms need to avoid predators, find food,
and find a place to live in order to maintain
homeostasis
What behaviors help animals
survive environmental changes?
■Migration:
– Helps animals avoid harsh
conditions that can come with
seasonal changes
– They move to more
favorable conditions
What behaviors help animals
survive environmental changes?
■ Hibernation:
– A deep sleep during which an
animal slows down its body
processes to save energy
– Heart rate, body temperature,
and nutritional needs are lowered
– Energy is conserved during periods of
unsuitable weather or food shortage
What behaviors help plants survive
environmental changes?
■Dormancy:
– Plants cannot move to another location
– Have specialized
structures to
store food
– Conserve energy
and stops growing
Define the following vocabulary
words…
■ Stimulus
■ Effector
– A thing or event that evokes a
specific functional reaction in
■ an organ or cell that acts in
an organ or organism
response to a stimulus
■ Receptor
– an organ or cell able to respond ■ Response
to light, heat, or other external
■ a reaction to the stimulus
stimulus and transmit a signal
to a sensory nerve
■ Negative Feedback
■ Integrating Center
■ a reaction that causes a
– receives information from the
decrease in function
sensors and initiates the
because of some kind of
response to maintain
stimulus
homeostasis