Individual organisms contribute to nutrient cycling in ecological systems, which is shown to be a mechanism of homeostasis at that level. The phosphorus and nitrogen cycles are used to illustrate effects of changes in populations or communities on the cycling of these nutrients. Major disturbances such as deforestation and global climate change disrupt nutrient cycles and ecological system homeostasis. Data are examined to determine effects of deforestation on nutrient cycling. Increasing atmospheric carbon dioxide and global climate change are disrupting ecological systems' homeostasis, and...

This book describes and analyzes genetic and environmental factors that cause variation in individuals and populations. Data will be used to evaluate the processes by which variation is generated in organisms and how variation affects natural selection. Genetic factors include mutation, independent assortment, crossing over, and recombination. Environmental factors include gradients and differences in abiotic conditions. Genotype frequencies can be used to determine allele frequencies and this information can be used to determine whether a population is evolving at a genetic locus. The...