AP Biology · Summary

Unit 8 summary

1. Endotherms make their own body heat and burn more fuel in the cold; ectotherms take heat from their surroundings and control it by behavior.
2. Only about 10 percent of the energy at one trophic level ends up in the next; most is lost as heat. Energy flows one way, while matter cycles.
3. Net primary productivity = gross primary productivity - producer respiration.
4. Exponential growth: dN/dt = rmax x N. Logistic growth: dN/dt = rmax x N x (K - N) / K, fastest at half of K.
5. Density-dependent factors such as competition and disease hit crowded populations harder; density-independent factors such as frost do not.
6. Mutualism is +/+, commensalism +/0, parasitism and predation +/-, competition -/-; removing a keystone species changes a whole community.
7. Simpson’s diversity index = 1 - the sum of (n/N) squared; more species and a more even spread raise it, and diverse ecosystems recover better from disruption.