unit 8: organism regulation, physiology and development
TRANSCRIPT
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 Feedback2. 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
AP Biology
intracellular waste
Animal systems evolved to support multicellular life
O2
CHO
CHO
aa
aa
CH
CO2
NH3aa
O2
CH
O2
aa
CO2
CO2
CO2
CO2
CO2
CO2 CO2
CO2
CO2
CO2
NH3
NH3 NH3
NH3
NH3
NH3
NH3NH3
O2
aa
CH
aa
CHO
O2
Diffusion too slow!
single cell
but whatif the
cells areclustered?
for nutrients in & waste out
extracellular waste
AP Biology
Circulatory systems Basic structures needed:
circulatory fluid = “blood” tubes = blood vessels muscular pump = heart
open closed
hemolymph
blood
AP Biology
Vertebrate circulatory system Adaptations in closed system
number of heart chambers differs
4 chamber heart is double pump = separates oxygen-rich & oxygen-poor blood; maintains high pressure
What’s the adaptive value of a 4 chamber heart?
2 3 4
low pressureto body
low O2
to body
high pressure & high O2
to body
AP Biology
Gas exchange in many forms…
one-celled amphibians echinoderms
insects fish mammals
endotherm vs. ectothermsize
cilia
water vs. land ••
AP Biology
Evolution of gas exchange structures
external systems with lots of surface area exposed to aquatic environment
Aquatic organisms
moist internal respiratory tissues with lots of surface area
Terrestrial
AP Biology
Nitrogen waste Aquatic organisms
can afford to lose water ammonia
most toxic
Terrestrial need to conserve
water urea
less toxic
Terrestrial egglayers
need to conserve water need to protect
embryo in egg uric acid
least toxic
AP Biology
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
selective reabsorption ofvaluable solutes & H2O back into bloodstream greater flexibility & control
“counter current exchange system”
whyselective reabsorption
& not selectivefiltration?