Transcript Populations
Warm Up •List the 4 biogeochemical cycles: 1 ECOSYSTEM DYNAMICS •Populations •Symbiosis •Succession http://www.nps.gov/pete/forteachers/life-in-an-ecosystem.htm Populations • Group of the same type of organism living in the same geographic area at a given time. • Limiting Factor – Causes a population to decrease in size. Examples: food, water, shelter, space • Sunlight in a rainforest = limiting factor • Carrying Capacity - maximum population size that an environment can contain Measuring Populations • Census – count all of the organisms in a population • Direct count • Sampling – count a small sample and use it to estimate the total population Techniques for Sampling • Quadrat Method • Good for counting sessile things • Sessile = NON MOVING • Construct a grid • Count several random quadrats http://www.psychology.ex.ac.uk/lundy/images/quad.jpg Capture-Recapture Method • Assumes population remains constant • Capture, mark and release organisms • Capture again, use formula: Mark – Recapture of Snakes https://www.youtube.com/watch?v=5DR50IgvE7g 7 Population Density • Need: population size and area • Ex. 40 oak trees in 10 acres Population Distribution • Clumped • Uniform/Even • Random Symbiosis Species Interaction • Predation • Predator – consumes another individual, the prey • Plants – adaptations to prevent predation (thorns) http://www.public.iastate.edu/~bsbowen/ZOOL-EEOB507/images/predprey-cheetahgazelle.jpg; http://www.bigfoto.com/themes/closeup/thorn-photo_if.jpg; http://www.ndpteachers.org/perit/Tapeworm%5B1%5D.JPG Parasitism • Parasite – feeds on host, harming but not killing it • Ectoparasite – external (ticks) • Endoparasite – internal (tapeworm) http://www.public.iastate.edu/~bsbowen/ZOOL-EEOB507/images/predprey-cheetahgazelle.jpg; http://www.bigfoto.com/themes/closeup/thorn-photo_if.jpg; http://www.ndpteachers.org/perit/Tapeworm%5B1%5D.JPG Competition – species compete for same limited resource (water) • Mutualism – both species benefit • (clown fish, sea anemone) • Commensalism – one species benefits, the other unharmed (human, apple tree) http://www.sandyart.com/Clown_Fish_.jpghttp Symbiosis Examples https://www.youtube.com/watch?v=8rSlA_ywEec 13 Succession • The gradual change in a community over time. • Primary community – development of a community where none existed before. • (Bare rock succession) • Secondary community – reclamation of a previously existing community • (Farmer’s field succession) • Climax community – long-term, generally stable • ( Old forest community)