Unit 8 Organism Regulation Physiology and Development WHAT

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: p. H 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 O 2 CH single cell CHO CO 2 aa NH 3 CHO O 2 CH aa CO 2 aa NH 3 CO 2 O 2 aa CH NH 3 CO 2 NH 3 AP Biology CO 2 NH 3 CO 2 aa intracellular waste O 2 NH 3 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” u tubes = blood vessels u muscular pump = heart u open hemolymph AP Biology closed blood

Vertebrate circulatory system § Adaptations in closed system u 2 low pressure to body number of heart chambers differs 3 4 low O 2 to body high pressure & high O 2 to body What’s 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 u u can afford to lose water ammonia § most toxic § Terrestrial u u need to conserve water urea § less toxic § Terrestrial egg layers u u u need to conserve water need to protect embryo in egg uric acid AP Biology § least toxic

Nephron § Functional units of kidney u 1 million nephrons per kidney § Function u u filter out urea & other solutes (salt, sugar…) blood plasma filtered into nephron § high pressure flow u AP Biology selective reabsorption of valuable solutes & H 2 O back into bloodstream § greater flexibility & control why selective reabsorption & not selective filtration? “counter current exchange system”