BIOL 202 Lecture 20: biol 202 ecol and evol 4/3 lect. density-dependent, allee effect, communities
8 Apr 2017
School
Department
Course
Professor
Document Summary
Density-dependent regulation: larger population size results in decreased number of resources and smaller population size. Large population of deer in us because of decreased predators compared to. Larger deer population leads to overgrazing (causes poor habitat quality) Large population downside is decreased number of females get pregnant and producing less embryos sometimes better to have few individuals that are healthier. Negative density-dependent: population decreases survival and birth rate in response to decreased density. Deer, birds on ram island that ran out of nesting sites. Positive density dependent- increased survival and birth rate in response to increased density. Shape of curve associated with population growth (or caring capacity): sigmoid (s- shaped) Curve from positive density-dependence and negative density-dependence. Bottom of curve= population growth slow= positive density-dependence. Top of curve= growth slow again= negative density-dependence. Allee effect: small population makes it hard to find a mate.
