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 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 ••

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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

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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 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?