Population Ecology - Principles of Biology - Lecture Slides, Slides of Biology

Download Population Ecology - Principles of Biology - Lecture Slides and more Slides Biology in PDF only on Docsity! • Where have all the sea otter gone? Population ecology Where have all the sea otters gone? – Sea otters are smallest marine mammals – Occur in coastal habitats in northern Pacific Ocean – Feed on variety of fish and marine invertebrates – Gregarious; live in ‘rafts’ of about 100 individuals Docsity.com • Where have all the sea otter gone? Population ecology Where have all the sea otters gone? – In late1700s, Americans, English and Russians hunting sea otters for pelts – By 1911, when International Fur Seal Treaty enacted, sea otters nearly extinct – Currently, about 150,000 sea otters Docsity.com • Population = groups of individuals of a given species that occur together Population ecology Where have all the sea otters gone? – Members of a single species make up a population – But a species may be represented by many populations – Major properties of populations: • Distribution • Demography • Dispersion Docsity.com • Distribution = geographic range of a population Population ecology Where have all the sea otters gone? – Biotic and abiotic conditions determine where a population can survive and reproduce – Population distributions can change over time • Most population distributions are declining because of habitat destruction by humans • Others expand or contract naturally – range shift of red spruce after glacier retreated – range expansion of cattle egret Docsity.com • Distribution Population ecology Where have all the sea otters gone? – Metapopulations = network of populations that interact occasionally by exchanging individuals • Occur when habitat is patchily distributed and separated by unsuitable habitat • Characterized by suitable habitat patches going extinct and getting recolonized over time • glanville fritillary butterfly in Finland Docsity.com • Demography = statistical study of populations Population ecology Where have all the sea otters gone? – Population size = number of individuals – Population growth = size of population over time – Population structure = proportion of individuals in different age classes • Population growth strongly influenced by age structure – Populations with large number of young individuals grow rapidly because an increasing proportion of individuals are reproductive – Populations with equal numbers of individuals in different age classes usually maintain same population size Docsity.com • Demography Population ecology Where have all the sea otters gone? – Population pyramids show age structure Docsity.com • Demography Population ecology Where have all the sea otters gone? – Life tables describe mortality and fecundity of different age classes • Mortality = number of individuals that die in a given period – Survivorship (lx) = proportion of individuals that survive from birth to age x – Mortality (Mx) = proportion of individuals that die between age x and age x+1 • Fecundity = number of offspring produced in a given period – Age-specific fecundity (mx) = average number of offspring produced by females at age x Docsity.com