Animal Form and Function
Animal body plan influences
Physical laws (limited by physics)
Fast swimmers (penguins, seals, etc.) have a streamlined, double tapered body plan
Bigger animals (with more skeleton) need more muscle, and that slows them down
Environmental cellular exchange
Unicellular organisms must be small, simple, and have a high surface to volume ratio
Multicellular organisms require an aqueous environment; as cell count increases, surface to volume ratio decreases
Tissue type and function
Epithelial is tightly packed and present whenever the body is exposed externally or internally; they are constantly sloughing off and regenerating
Connective tissue contains fewer cells and an extracellular matrix; holds tissues and organs together
Muscle tissue is most abundant; specializes in contraction and accounts for energy usage
Nervous tissue sense stimuli and transmits signals via nerve impulses
Coordination and control
Endocrine system
Produces hormones into the animals bloodstream (long lasting)
Nervous system
Fast acting nerve impulses
Homeostasis
Set point
Thermoregulation
Endothermy
Ectothermy
Animals that generate their own heat through metabolism are endotherms
Includes mammals, birds and some fish and insects
Disadvantage: must eat a lot of food Advantage: Can exist in a large temperature range
Animals that get heat from their environment are ectotherms
Includes amphibians, reptiles, many fishes, and most invertebrates
Generate heat through behavior (basking in the sun)
Limited habitats (they don't live in Antarctica) but require less food (10% of what endotherms need)
Don't use the terms "warm-blooded" or "cold-blooded"
Body temperature
Poikilotherms are animals whose body temperatures vary with the environment
Homeotherms can relatively constant body temperatures
No fixed relation between these two and endothermy and ectothermy
Balancing heat gain and loss
Insulation
Includes hair, feathers, fat, and fur
When animals raise their fur or feathers, it traps a thick layer of air, contributing to a higher insulating power
Humans lack feathers and fur, and rely on fat for warmth
Apparently goosebumps are a vestige in humans, but they do actually contribute to warmth
Marine animals have a thick layer of insulating fat, called blubber, which helps keep them warm in frigid temperatures
Circulation
Circulatory systems are a major route for heat flow; blood carries heat
Thermoregulation is maintained via vasoconstriction or vasodilation
Countercurrent heat exchange
In many birds and mammals, veins and arteries run parallel, which conserves heat; warm blood from the core moves to the veins, bringing the heat back into the core
Explains why fingers and toes are the first to get cold
Evaporation
Only way that animals cool down
Panting, sweating, and bathing increase evaporation
Behavior
Primary way for ectotherms to cool down
Includes sun basking, seeking shade,orienting the body to maximize or minimize sun exposure, and huddling together
Long term methods include hibernation and migration
Metabolism
Primary way for endotherms to combat heat loss and utilize thermogenesis
Movement (shivering) generates heat through increased muscle movement
Some animal use hormone to cause mitochondria to create heat instead of energy (nonshivering thermogenesis)
Takes place in brown fat, adipose tissue designed for rapid heat production
In human babies, brown fat accounts for 5% of body weight, although it is present in adults as well
Acclimatization is a physiological adjustment to an environmental factor
Growing more feathers or altering the cell membrane in the cold
Sensors for thermoregulation exist in the hypothalamus
Energy requirements
Bioenergetics is the overall flow and transformation of energy in an animal
Metabolic rate
The amount of energy used in a unit of time
Measured in joules or calories
Measured by heat loss in a calorimeter, by oxygen consumed or carbon dioxide produced, or by food consumption vs. feces (long term monitoring)
The minimum metabolic rate of a nongrowing endotherm at rest is the basal metabolic rate (BMR)
The metabolic rate of a nongrowing ectotherm at rest is the standard metabolic rate (SMR)
Comparision of BMR and SMR shows the high energy cost of endothermy; The BMR for humans is around 1,600-1,800 kcal/day (males) or 1,300-1,500 kcal/day (females) while the SMR for alligators, which are much bigger, is only 60 kcal/day.
The bigger you are, the more energy you need (Metabolic rate = body mass^¾)
The amount of energy required to maintain each gram of weight is inversely related to size
Energy conservation
Tophor is the state of decreased energy and metabolism to conserve energy; bats feed at night and go into tophor in the day time
Hibernation is the state of prolonged tophor, where body temperature and energy requirement decrease (ground squirrels in hibernation only need 5-8 kcal/day as opposed to their regular 150 per day)
Estivation is summer tophor; allows animals to survive long periods of high temperature and little water