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