1. Unit 8: Organism Regulation, Physiology and Development

2. 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.

3. Feedback Loops Used at all levels of organization in living systems.
Two types:
Negative Feedback
Positive Feedback

4. 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

6. 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

7. 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

9. 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.

10. Otherwise, disease, degradation and death are unavoidable. 
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. 

11. 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

12. Animal systems evolved to support multicellular life
CHO aa CH
CO2
NH3
single cell aa
CO2
NH3 O2 CH
CHO
intracellular waste
but what if the cells are
clustered?
extracellular waste
Diffusion too slow!
for nutrients in & waste out

13. Circulatory systems Basic structures needed:
circulatory fluid = “blood”
tubes = blood vessels
muscular pump = heart
open
closed
hemolymph
blood

14. Vertebrate circulatory system
Adaptations in closed system
number of heart chambers differs 2 3 4
high pressure & high O2 to body
low pressure to body
low O2 to body
What’s the adaptive value of a 4 chamber heart?
4 chamber heart is double pump = separates oxygen-rich & oxygen-poor blood; maintains high pressure

15. Gas exchange in many forms…
one-celled
amphibians
echinoderms
cilia
insects
fish
mammals
size •
water vs. land •
endotherm vs. ectotherm

16. Evolution of gas exchange structures
Aquatic organisms
external systems with lots of surface area exposed to aquatic environment
Terrestrial
Constantly passing water across gills
Crayfish & lobsters
paddle-like appendages that drive a current of water over their gills
Fish
creates current by taking water in through mouth, passes it through slits in pharynx, flows over the gills & exits the body
moist internal respiratory tissues with lots of surface area

17. Nitrogen waste Aquatic organisms Terrestrial Terrestrial egg layers
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
least toxic
Mode of reproduction appears to have been important in choosing between these alternatives.
Soluble wastes can diffuse out of a shell-less amphibian egg (ammonia) or be carried away by the mother’s blood in a mammalian embryo (urea).
However, the shelled eggs of birds and reptiles are not permeable to liquids, which means that soluble nitrogenous wastes trapped within the egg could accumulate to dangerous levels (even urea is toxic at very high concentrations).
In these animals, uric acid precipitates out of solution and can be stored within the egg as a harmless solid left behind when the animal hatches.

18. why selective reabsorption & not selective filtration?
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 of valuable solutes & H2O back into bloodstream
greater flexibility & control
Each nephron consists of a single long tubule and a ball of capillaries, called the glomerulus.
The blind end of the tubule forms a cup-shaped swelling, called Bowman’s capsule, that surrounds the glomerulus.
Each human kidney packs about a million nephrons.
why selective reabsorption & not selective filtration?
“counter current
exchange system”