Unit 8 - Organism Regulation, Physiology and Development
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 aa O2 CH single cell CHO
CO2 aa NH3 CHO O2 O2 CH aa CO2 CO2
aa NH3 CO2 NH3 CO2 O2 aa CH NH3 CO2 CO2
NH3 AP Biology CO2 NH3 CO2 NH3 CO2 NH3 CO2 aa
intracellular waste O2 NH3 but what if the cells are clustered? CHO Diffusion too slow! extracellula r waste
for nutrients in & waste out Circulatory systems Basic structures needed: circulatory fluid = blood tubes = blood vessels muscular pump = heart open hemolymph AP Biology 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 Whats the adaptive value of a 4 chamber heart? 4 chamber heart is double pump = separates oxygen-rich & AP Biology oxygen-poor blood; maintains high pressure Gas exchange in many forms one-celled amphibians echinoderms insects
fish mammals cilia AP Biology 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 AP Biology 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 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 AP Biology selective reabsorption of valuable solutes & H2O back into bloodstream greater flexibility & control why selective reabsorption & not selective filtration?
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