FORM, FUNCTION, HOMEOSTASIS Who’s in charge here?? FORM, FUNCTION, HOMEOSTASIS

More than just a common ancestor All organisms require chemical energy for growth, repair, physiological processes, regulation, and reproduction characteristics of life anyone? The comparative study of animals reveals that form and function are closely correlated The study of bioenergetics tells us much about an animal’s adaptations

The link between form and funciton Size and shape affect how organism interacts with it’s environment how the animal exchanges energy and materials with its surroundings. Convergence occurs because natural selection shapes similar adaptations when diverse organisms face the same environmental challenge, such as the resistance of water to fast travel.

Evolution is NOT perfection! Evolution IS compromise. Warning!!!!! Evolution is NOT perfection! Evolution IS compromise.

“All for One, and One for All!” Animals are complex, multicellular organisms No ONE organ or ogran system can stand alone!!! http://www.comp.dit.ie/dgordon/League/OtherLeagues/c17/threemuskeeters2.jpg

LE 40-4 External environment CO2 Food O2 Mouth Animal body Respiratory system Blood 50 µm 0.5 cm A microscopic view of the lung reveals that it is much more spongelike than balloonlike. This construction provides an expansive wet surface for gas exchange with the environment (SEM). Cells Heart Nutrients Circulatory system 10 µm Digestive system Interstitial fluid Excretory system The lining of the small intestine, a digestive organ, is elaborated with fingerlike projections that expand the surface area for nutrient absorption (cross-section, SEM). Anus Inside a kidney is a mass of microscopic tubules that exchange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM). Unabsorbed matter (feces) Metabolic waste products (urine)

Tissues are classified into four categories Epitheleal Connective Covers the outside of the body Lines organs and cavities Cells are closely joined together Types: Binds and supports other tissues sparsely packed cells scattered throughout an extracellular matrix Types:

LE 40-5_2 Chondrocytes Collagenous fiber Loose connective tissue 120 µm Chondrocytes Collagenous fiber Loose connective tissue Chondroitin sulfate Elastic fiber 100 µm Cartilage Fibrous connective tissue Adipose tissue Fat droplets Nuclei 150 µm 30 µm Blood Central canal Red blood cells Bone White blood cell Osteon Plasma 700 µm 55 µm

Four categories of tissues cont’d Muscle Nervous consists of long cells called muscle fibers contract in response to nerve signals Types senses stimuli transmits signals throughout the animal Types

LE 40-5_3 Multiple nuclei Skeletal muscle Muscle fiber Sarcomere MUSCLE TISSUE 100 µm Multiple nuclei Skeletal muscle Muscle fiber Sarcomere Cardiac muscle Nucleus Intercalated disk 50 µm Nucleus Smooth muscle Muscle fibers 25 µm NERVOUS TISSUE Neuron Process Cell body Nucleus 50 µm

How is homeostasis maintained? Bioenergetics, the flow of energy through an animal, limits behavior, growth, and reproduction Energy-containing molecules from food are used to make ATP to power cellular work After the needs of staying alive are met, remaining food molecules can be used in biosynthesis

LE 40-7 Organic molecules in food External environment Animal body Digestion and absorption Heat Energy lost in feces Nutrient molecules in body cells Energy lost in urine Carbon skeletons Cellular respiration Heat ATP Biosynthesis: growth, storage, and reproduction Cellular work Heat Heat

“I’m not fat, I just have a slow metabolism” An animal’s metabolic rate is closely related to its bioenergetic strategy Basal Metabolic Rate: Metabolic rate is affected by size and activity of the organism maximum metabolic rate is inversely related to the duration of the activity

Bioenergetic strategies Endothermic organisms Ectothermic organisms Example: Birds and mammals Bodies are warmed by mostly by heat generated by metabolism Typically have higher metabolic rates more energetically expensive Example: Amphibians , fish, and reptiles Gain heat from their external environment Have lower metabolic rates tolerate greater variation in internal temperature

Maximum metabolic rate LE 40-9 500 A = 60-kg alligator A H 100 H A A = 60-kg human 50 H Maximum metabolic rate (kcal/min; log scale) 10 H 5 H A 1 A 0.5 A 0.1 1 second 1 minute 1 hour 1 day 1 week Time interval Key Existing intracellular ATP ATP from glycolysis ATP from aerobic respiration

Bioenergetic strategies Regulators Conformers uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation allows its internal condition to vary with certain external changes The term “internal environment” is in reference to the interstitial fluid

LE 40-10 Endotherms Ectotherm 800,000 340,000 8,000 4,000 438 Human Reproduction Basal (standard) metabolism Temperature regulation Growth Activity Annual energy expenditure (kcal/yr) 340,000 8,000 4,000 60-kg female human from temperate climate 4-kg male Adélie penguin from Antarctica (brooding) 0.025-kg female deer mouse from temperate North America 4-kg female python from Australia Total annual energy expenditures. The slices of the pie charts indicate energy expenditures for various functions. 438 Human Energy expenditure per unit mass (kcal/kg•day) 233 Python Deer mouse Adélie penguin 36.5 5.5 Energy expenditures per unit mass (kcal/kg•day). Comparing the daily energy expenditures per kg of body weight for the four animals reinforces two important concepts of bioenergetics. First, a small animal, such as a mouse, has a much greater energy demand per kg than does a large animal of the same taxonomic class, such as a human (both mammals). Second, note again that an ectotherm, such as a python, requires much less energy per kg than does an endotherm of equivalent size, such as a penguin.

Mechanisms of homeostasis receptor control center effector Negative Feedback Positive Feedback buildup of the end product shuts the system off Allows certain internal environmental conditions to be maintained within a range For Example? change in a variable triggers mechanisms that amplify rather than reverse the change Pushes a system further until the stimulus is removed For Example?

This guy’s got it easy! Thermoregulation….. Radiation Evaporation LE 40-13 Radiation Evaporation Convection Conduction Thermoregulation….. This guy’s got it easy!

…a delicate balance between heat loss and heat gain Five general adaptations help animals thermoregulate: Insulation Circulatory adaptations Cooling by evaporative heat loss Behavioral responses Adjusting metabolic heat production

Back to that “All for One” philosophy Insulation Circulatory adaptations Integumentary system reduces heat flow between an animal and its environment Structures of the skin Circulatory system alter the amount of blood flowing between the body core and the skin Vasodilation Vasoconstriction *Countercurrent heat exchanger

Back to that “All for One” philosophy Cooling by evaporative heat loss lose heat through evaporation of water in sweat Bathing moistens the skin Aaaahhhhh….muuuuuch better!

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Back to that “All for One” philosophy Some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat Some animals can regulate body temperature by adjusting their rate of metabolic heat production

Internal body temperature LE 40-21 Thermostat in hypothalamus activates cooling mechanisms. Sweat glands secrete sweat that evaporates, cooling the body. Blood vessels in skin dilate: capillaries fill with warm blood; heat radiates from skin surface. Increased body temperature (such as when exercising or in hot surroundings) Body temperature decreases; thermostat shuts off cooling mechanisms. From simple to complex Homeostasis: Internal body temperature of approximately 36–38°C Body temperature increases; thermostat shuts off warming mechanisms. Decreased body temperature (such as when in cold surroundings) Blood vessels in skin constrict, diverting blood from skin to deeper tissues and reducing heat loss from skin surface. Thermostat in hypothalamus activates warming mechanisms. Skeletal muscles rapidly contract, causing shivering, which generates heat.

Negative feedback and appetite? Neuronal pathways that control energy balance and their regulation by hormonal signals such as insulin and leptin Negative feedback and appetite? http://www.medscape.com/viewarticle/448465

The Stork….or Positive Feedback? Childbirth is the best example of the positive feedback mechanism at work Fever is also considered http://www.sciencedaily.com/images/2007/04/070402215329.jpg