1. Homeostasis

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

3. 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

5. 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

6. 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 ( neurotoxins, poisons and pesticides)
Ex: Dehydration
Too much water loss causes cellular environment to be too hypertonic. Cellular work stops. Death…
Ex: Drugs- signals are blocked
High BP drugs, anesthetics, antihistamines, birth control pills
Ex: Diseases
Diabetes, heart disease, autoimmune disease, cancer

7. 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.

8. 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. 

9. 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

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

11. 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

12. 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

13. Homeostasis: regulation of internal environment
Osmoregulation solute and water balance
Excretion process of removing nitrogen-containing waste
Tardigrades or water bears can dehydrate and rehydrate when conditions are better.

14. Marine Animals
Seawater is saltier than internal fluids so water is lost
Fish drink sea water and dispose of salt through their gills
Kidneys dispose of other ions while excreting only small amount of water

15. Freshwater Fish They gain water and lose salts Drink little water
Uptake salt by gills and from food
Excrete large amounts of water in dilute urine
Record Perch- 50 lbs

16. Land Animals Humans can’t survive a 12% water loss
Water is replaced by eating, drinking and efficient waste removal and metabolic water recovery
Kangaroo rat loses 2 mL/day vs human’s 2500 mL /day

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. Uric Acid and Shelled Eggs
Metabolic waste
must be stored until
birth
Uric acid is not
water soluble or
toxic and needs little
water

19. If abundant water is not available?
UREA- not highly toxic, does not require
as much water