Env. Science/ Ecology 5-3 What limits the growth of populations?

5.3 What limits the growth of populations?
• A population is a group of interbreeding individuals of the same species. Most populations live together in groups (packs of wolves, flocks of birds).
• Variables that govern changes in population size are birth, death, immigration, and emigration. Other factors that affect population size are age structure, range of tolerance, limiting factors, and population density.
• A rapidly growing population of any species eventually reaches some size limit imposed by limiting factors such as sunlight, water, temperature, space, nutrients, or exposure to predators or infectious diseases.
• r-selected species, with short life spans, little parental care, and many offspring, have a capacity for a high rate of population increase. K-selected species reproduce later in life, with greater parental care, fewer offspring, and longer life spans.
• A survivorship curve illustrates the different life expectancies of species, showing the percentages of the members of a population surviving at different ages.