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Biological Succession. Chapter 34. British Succession. Biological Succession. Helps to explain changes ecosystems go through Gradual replacement of one community for another Slow, orderly, and predictable manner Divided into two categories: Primary succession Secondary succession.
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Biological Succession Chapter 34 British Succession
Biological Succession • Helps to explain changes ecosystems go through • Gradual replacement of one community for another • Slow, orderly, and predictable manner • Divided into two categories: • Primary succession • Secondary succession
Primary Succession • When living organisms first inhabit an area • As time goes by, communities flourish • Slowly replaced by other communities and organisms • Can be seen in wake of retreating glacier • Also known as Bare Rock Succession http://www.geo.arizona.edu/Antevs/nats104/00lect20sucn1.gif
Pioneer Species • The pioneer community is first to be established and consists of pioneer species. • Rapidly growing group of organisms • Exists where no life previously existed • Examples: • Lichen • Moss • Liverworts http://farm1.static.flickr.com/105/288389624_13d12a707a.jpg?v=0
Primary Succession • Lichen establish themselves on barren rock • Create environment for other organisms • Thin layer of soil forms over rocks • Soil thickens—seeds and spores established • Supports grasses, ferns, and small shrubs http://www.prairienursery.com/store/images/00-LowGrowingPrairie-sc.jpg
Primary Succession • Other organisms begin to inhabit area • Insects, rodents, birds, and migrating animals • Rich environment may support trees • After many years—mature forest ecosystem • Shifting rivers/shorelines can cause primary succession http://livelihooddevelopmentafrica.org/nile/mango8.jpg
Secondary Succession • Gradual replacement of one community for another • In a slow, predictable manner • Where life has already flourished • Usually caused by some catastrophic event • Volcanic eruption, forest fire, or flood • Can also include human activity • Also known as “Farmer’s Field Succession” Pine tree growing in ash after Mt. St. Helen’s erupted in 1980 http://www.tdn.com/helens/noFlash/mainpage.php?p=1116270020&w=P
Secondary Succession • When forest fire burns away a forest ecosystems • Leaves nothing behind but burnt debris • Begins almost immediately • Seeds and spores germinate and sprout • Establishes grasses and ferns • Overtake area, give way to sprouting trees Giant Sequoias need fire for germination http://www.nps.gov/archive/seki/fire/images/smoke.jpg
Secondary Succession • Trees shade out grass • Small shrubs become established • Soon harbors life again • Trees grow taller • Birds, insects, and mammals begin to inhabit • 70 to 100 years ecosystem reestablished • Biological succession reclaims disturbed areas