Key Terms
Asymmetrical
No pattern, no symmetry. Example: sponge.
Radial
Up-down orientation; any cut along the longitudinal axis produces equal halves; no defined left or right. Found mostly i
Bilateral
Front-back cut produces defined right and left sides. Found in land and aquatic animals; enables high mobility.
Anterior
Front Posterior: rear Dorsal: toward the back Ventral: toward the stomach
Aquatic animals
Constrained by drag (water has higher viscosity than air). Bilateral aquatic animals often have fusiform shape - tubular
Land animals
Constrained primarily by gravity. Drag is relatively unimportant.
Sphere surface area
4(pi)r^2 Sphere volume: (4/3)(pi)r^3 Surface-to- volume ratio: 3/r
Solution
Multicellularity. Large organisms develop specialized systems (circulatory, respiratory, digestive) to move nutrients an
Endotherm
Internal heat source; maintains constant body temp across varying environments; requires high caloric intake to fuel thi
Ectotherm
External heat source; body temp tracks environment. Also called poikilotherm when temperature actually varies.
Human male BMR
1,600-1,800 kcal/day Human female BMR: 1,300-1,500 kcal/day Alligator SMR: 60 kcal/day
Result
Small endotherms have higher BMR per body weight than large endotherms.
Average daily energy consumption
2-4 times BMR or SMR. Humans are relatively sedentary: ~1.5 times BMR.
Torpor
Reduced activity and metabolism in response to environmental stress Estivation: summer torpor; triggered by heat and low
Hibernation
Long-term torpor during winter.