Animal Form and Function ch 40

What problems do all three share? Differences?

Animals come in a variety of sizes and shapes yet all share similar problems – obtain oxygen, food, get rid of waste (exchange with environment) – fight infection – reproduce – homeostasis

I. Correlation between Animal Form and Function Form fits function at all the levels of life, from molecules to organisms. What limits animal form? – Physical laws that affect strength, movement, heat exchange, diffusion

A. Exchange with the Environment Exchange of nutrients, waste, gases occurs at the cell membrane of all cells Cell membrane MUST be bathed in aqueous environment for diffusion What constrains this diffusion? – Surface area to volume ratio of cells

1. Single celled organisms Enough surface area in contact with environment to service cytoplasm

2. simple animals with gastrovascular cavity (cnidarians, flatworms) body walls only 2 cell layers thick so enough surface area in contact with environment

3. more complex and larger animals have organ systems for exchange – respiratory – digestive – excretory have highly folded internal surfaces for exchange these are evolutionary adaptations for increased size and help animals in variable environments maintain steady internal conditions

II. Coordination and Control organ system activity is under control of nervous and endocrine systems these involve cell communication and help keep an organism in homeostasis

What do these 2 have in common?

III. Feedback Control Maintains Homeostasis A. Regulators and Conformers Regulators – Use internal mechanisms to maintain homeostasis Conformers – Internal conditions change along with external environment

Explain the graph:

Animals can be regulators for one stimulus and conformers for another (fish and water)

B. Homeostasis ability of an organism to maintain constant internal conditions body temp, blood pH, blood glucose etc in humans involves feedback loops

1. Negative feedback loop Most homeostatic control mechanisms Control mechanism that moves AWAY from the stimulus Ex: body temp Explain:

2. Positive feedback loop Only stressful situations Control mechanism that moves TOWARDS the stimulus Ex: childbirth

IV. Homeostatic control of thermoregulation involves form, function and behavior Thermoregulation = process by which animals maintain an internal body temp within a specific range All enzymatic and physiological processes are sensitive to changes in temp

How do these animals regulate body temp?

A. Endothermy and Ectothermy Endotherms: gain heat thru metabolism Ectotherms: gain body heat externally Endotherms must consume more food than ectotherms Ectotherms can tolerate greater fluctuations in body temp than endotherms

Graph body temp as a function of external temp for endotherms and exotherms

B. Poikilotherms vs Homeotherms Poikilotherms body temp changes with environment Homeotherms body temp is relatively constant

Is an angelfish that inhabits the waters of the Caribbean a poikilotherm or homeotherm? Endotherm or ectotherm?

Is a hibernating chipmunk a poikilotherm or homeotherm? Endotherm or ectotherm?

C. Exchanging Heat with the Environment In order to thermoregulate, organisms must gain or lose heat with the environment Which way does heat move?

Which mechanisms result in heat loss? Which mechanisms result in heat gain?

What must occur in order to maintain constant body temp? In order to maintain body temp, heat loss to environment and heat gain from environment must be balanced

B. Mechanisms that Regulate Body Temp 1. Insulation (endotherms) Hair, fur, feathers, fat layers Raised fur and feathers traps heat near skin Excess fat near surface prevents core body heat loss in marine mammals Oily secretions in many birds and mammals that spend time in water prevents heat loss

2. dilating or constricting blood vessels (endotherms and a few ectotherms): Vasodilation increases the diameter of the blood vessels. This increases vessel surface area and allows excess heat to be lost Vasoconstriction constricts the diameter of blood vessels. This decreases vessel surface area and prevents heat from being lost

What do they have in common?

3. evaporative cooling (endotherms): Humans lose excess heat thru their skin (sweating) Furry mammals lose excess heat thru panting. This is due to the excess heat absorbed to evaporate water. Why?

4. Adjusting metabolic heat production (endotherms and a few ectotherms ) Thermogenesis: adjustment of metabolic heat production to maintain body temp Shivering thermogenesis: increased muscle contraction due to increased metabolic activity Nonshivering thermogenesis: hormonal increase in metabolism in brown fat cells with the production of heat vs ATP

Graph O2 consumption as a function of external temp for endotherms and exotherms. What does O2 consumption measure?

5. Behavioral changes Ectotherms change locations Hibernation/migration

V. Hormonal Control of Thermoregulation Under control of hypothalamus

VI. Energy requirements are related to size, activity, and environment Bioenergetics = flow and transformation of energy in an animal determines how much food is needed and relates to animal’s size, activity, and environment

metabolic rate: amount of NRG animal uses in a given time how can metabolic rate be measured? basal metabolic rate: minimum metabolic rate of endotherm in fasting, nonstressed, nongrowing, constant temp conditions standard metabolic rate: minimum metabolic rate of ectotherm in fasting, nonstressed, nongrowing, constant temp conditions

1. Thermoregulation and metabolic rate Who has a higher minimum metabolic rate, endotherm or ectotherm? Why?

2. Size and metabolic rate What is this graph telling?

Smaller mammals have a higher metabolic rate per gram of body and therefore a higher breathing rate, heart rate Who consumes more food per unit body mass?