Lectures 33 & 34: Ecology 1
Ecology is:
Study of the processes that control the distribution and abundance of species
Study of the relationships organisms have with each other (biotic environment) and abiotic environment
Weather: short term state of atmospheric conditions
Climate: long term atmospheric conditions, extent of variation, at a particular place over time
Microclimate: subset of climatic conditions in a small specific area
Biome: environment that is shaped by its climatic and geographic attributes and characterized by ecologically similar organisms
Habitat: the biotic and abiotic environmental conditions required by a species
Phylogeography: evolutionary history and distribution
Chemoheterotrophs feeding strategies
Herbivores Eat Plants- have adaptations to digest plant material
Predators- capture, kill, eat other animals
Filter Feeders: use straining devices to filter small organisms and organic molecules from air or water
Omnivores eat both plants & animals- often depends on life stage
Parasites live in or on another animal
Detritivores feed on decomposing organic matter
Four Processes control populations
Deaths
Immigration
Births
Emmigration
Population: all the individuals of a species living together in the same area
Population Density: population size (# individuals) per a given sized area
Population Dynamics: changes over time in population size and composition
Exponential Growth: Population grows by a percentage; J curve
Logistic Growth:Population size increases rapidly at first but then slows down as population grows larger; S curve
Carrying Capacity: the maximum number of individuals an area can support
Modeling Population Growth
b = per capita birth rate
d = per capita death rate
N=Population size
r= intrinsic rate of increase-- per capita birth rate - per capita death rate
In logistic growth, K is carrying capacity
Density-Dependent Factors (usually biotic)
Density-Independent Factors (tend to be abiotic)
A k-adapted species has stable population size, fewer offspring, live longer
An r-adapted species lives less long, has many offspring, usually prey
Semelparity- reproduce only once
Iteroparity: reproduce multiple times
Offspring size: Large favored if resources are scarce, small favored if dispersal is important
Overshoot & crash cycles