Download Homeostasis

Unit 8:
Organism Regulation,
Physiology and Development
WHAT YOU MUST KNOW:
1. The importance of homeostasis from a cell
to an organism to an ecosystem.
2. How feedback systems control homeostasis.
3. Examples of positive and negative feedback.
4. How systems are affected by disruptions in
homeostasis.
5. How structures (adaptations) have evolved
to maintain homeostasis showing common
ancestry.
Feedback Loops
• Used at all levels of organization in living
systems.
• Two types:
1. Negative Feedback
2. Positive Feedback
Negative Feedback
• They regulate systems or processes
• Maintains homeostasis at a set point or range
• The response (or feedback) to the stimulus
decreases the occurrence of the stimulus or is
opposite of the stimulus.
– Examples: Lac operon, temperature regulation,
plant responses to water limitations, population
growth, blood sugar and blood calcium regulation
Positive Feedback
• Amplifying in nature
• The response is to amplify or increase the
occurrence of the stimulus.
– Examples: labor, fruit ripening and lactation in
mammals
Effects of Disruptions
• Seen at all levels of organization
• Molecular and cellular level:
– Ex: Response to toxins
• interferes with specific metabolic pathways or cause
cell damage
– Ex: Dehydration
• Too much water loss causes cellular environment to be
too hypertonic. Cellular work stops. Death…
– Ex: pH change in the bloodstream
– Ex: blood sugar concentrations
Ecological Disruptions
• Affects balance of the ecosystems
• Examples:
– Invasive species: outcompetes native species or
places a rapid stress on natives
– Natural disturbances: fires, earthquakes etc.
Note: as long as disruption is not too
large and too rapid for homeostatic
feedback loops to function, rebound
will occur.
Otherwise, disease, degradation and
death are unavoidable. 
Physiological Interactions
• Multicellular organisms are organized into
organ systems, which contain organs that
work together to accomplish life processes.
• Organ systems also interact for life processes
– Examples:
•
•
•
•
•
Stomach and small intestine
Plant organs
Respiratory and Circulatory System
Nervous and Muscular System
Kidney and bladder
Animal systems evolved to
support multicellular life
single cell
aa
O2
CH
CHO
CO2
aa
NH3
CHO
O2
O2
CH
aa
CO2
CO2
aa
NH3
CO2
NH3
CO2
O2
NH3
CO2
CO2
aa
NH3
CH
NH3
NH3
CO2
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CO2
NH3
CO2
intracellular
waste
O2
NH3
but what
if the
cells are
clustered?
CHO
CO2
aa
Diffusion too slow!
extracellular
waste
for nutrients in & waste out
Circulatory systems
 Basic structures needed:
circulatory fluid = “blood”
 tubes = blood vessels
 muscular pump = heart

open
hemolymph
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closed
blood
Vertebrate circulatory system
 Adaptations in closed system

2
low
pressure
to body
number of heart chambers differs
3
4
low O2
to
body
high
pressure
& high O2
to body
What’s the adaptive value of a 4 chamber heart?
4 chamber heart is double pump = separates oxygen-rich &
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Biology
oxygen-poor
blood; maintains high pressure
Gas exchange in many forms…
one-celled
amphibians
echinoderms
insects
fish
mammals
cilia
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•
size
water vs. land
•
endotherm vs. ectotherm
Evolution of gas exchange structures
Aquatic organisms
external systems with
lots of surface area
exposed to aquatic
environment
Terrestrial
moist internal
respiratory tissues
with lots of surface area
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Nitrogen waste
 Aquatic organisms


can afford to lose water
ammonia
 most toxic
 Terrestrial


need to conserve
water
urea
 less toxic
 Terrestrial egg
layers



need to conserve water
need to protect
embryo in egg
uric acid
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 least toxic
Nephron
 Functional units of kidney

1 million nephrons
per kidney
 Function


filter out urea & other
solutes (salt, sugar…)
blood plasma filtered
into nephron
 high pressure flow

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selective reabsorption of
valuable solutes & H2O
back into bloodstream
 greater flexibility & control
why
selective reabsorption
& not selective
filtration?
“counter current
exchange system”