Download Habitat Loss and Degradation - Introduction to Conservation Biology - Lecture Slides and more Slides Biology in PDF only on Docsity! Habitat Degradation & Loss Docsity.com Species-Area Curves 0 100 200 300 400 500 0 2500 5000 N o. s pe ci es A very consistent pattern of organismal distribution Area Docsity.com Rare species are especially vulnerable Small populations are especially prone to extinction from both deterministic and stochastic causes Docsity.com E.g., Hawaii’s native bird species Half of the remaining species went extinct soon after Captain James Cook arrived (in 1778) Half went extinct soon after the Polynesians arrived (in ~ 300 A.D. / C.E.) Rare species are especially vulnerable Small populations are especially prone to extinction from both deterministic and stochastic causes Docsity.com ∆N ∆t = B - D Rare species are especially vulnerable In a closed population (i.e., no immigration or emigration) of size N, the change in population size for a change in time, where B = births, and D = deaths, is: Small populations are especially prone to extinction from both deterministic and stochastic causes Remember the “BIDE factors”: birth, immigration, death & emigration Docsity.com Example, r = –0.5 : Population A Population B NA,t = 1000 NB,t = 10 NA,t+1 = 500 NB,t+1 = 5 Nt+1 = Nt + ∆N ∆t Rare species are especially vulnerable Small populations are especially prone to extinction from both deterministic and stochastic causes Docsity.com Deterministic r < 0 Genetic stochasticity Demographic stochasticity individual variability of r (e.g., variance) Environmental stochasticity temporal fluctuations of r (e.g., change in mean) Catastrophes Rare species are especially vulnerable Small populations are especially prone to extinction from both deterministic and stochastic causes Docsity.com Demographic & Environmental Stochasticity Demographic Stochasticity Each student is a sexually reproducing, hermaphroditic, out-crossing annual plant. Arrange the plants into small sub-populations (2-3 plants/pop.). In the first growing season (generation), each plant mates (if there is at least 1 other individual in the population) and produces 2 offspring. Offspring have a 50% chance of surviving to the next season. flip a coin for each offspring; “head” = lives, “tail” = dies. Note that average r = 0; each parent adds 2 births to the population and on average subtracts 2 deaths [self & 1 offspring – since 50% of offspring live and 50% die] prior to the next generation. Docsity.com Pollution is a Form of Habitat Degradation Light pollution Air pollution & acid rain Solid waste & plastics Chemical pollution (e.g., DDT, endocrine disruptors) Docsity.com Pollution is a Form of Habitat Degradation Light pollution Air pollution & acid rain Solid waste & plastics Chemical pollution (e.g., DDT, endocrine disruptors) Excessive nitrogen inputs Eutrophication Etc… Docsity.com Image from www.gulfhypoxia.net Pollution is a Form of Habitat Degradation Excessive nitrogen inputs & eutrophication Docsity.com
