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Explore the natural and gradual changes in species composition in an area through ecological succession. Learn about primary and secondary succession, pioneer species, and the formation of climax communities. Discover how succession occurs in aquatic ecosystems, including eutrophication and its impact.
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Definition: • Natural, gradual changes in the types of species that live in an area; can be primary or secondary • The gradual replacement of one plant community by another through natural processes over time
Primary Succession • Begins in a place without any soil • Sides of volcanoes • Landslides • Glaciers receding • Starts with the arrival of living things such as lichens that do not need soil to survive • Called PIONEER SPECIES
Lichens! http://botit.botany.wisc.edu http://www.saguaro-juniper.com/
Pioneer Traits • Generalist- can thrive in a wide range of environments and habitats • Temperatures, Precipitation, pH • Reproduce quickly and often- spread fast • The plants we call “weeds” are pioneers • We try to kill them, but keep coming back
Primary Succession • Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces • When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil • As soil begins to form, more organisms colonize the area.
Next Generation after Lichens – Mosses, small plants (ferns) http://www.life.uiuc.edu
Primary Succession • Simple plants like mosses and ferns can grow in the new soil http://www.uncw.edu http://uisstc.georgetown.edu
Primary Succession • The simple plants die, adding more organic material to the new soil • The soil layer thickens, and grasses, wildflowers, and other plants begin to take over http://www.cwrl.utexas.edu
Primary Succession • These plants die, and they add more nutrients to the soil • Soil can now support shrubs and trees http://www.rowan.edu
Primary Succession • Insects, small birds, and mammals have begun to move in • What was once bare rock now supports a variety of life • Takes a LONG Time= 1000+ yrs http://p2-raw.greenpeace.org
Secondary Succession • Location that has soil but underwent a DISTURBANCE such as • Forest fire • Flood • Human Change- farms, housing, deforestation • Occurs faster and has different pioneer species than primary succession
Nature will return • Evidence of succession is observable in rural, suburban, or urban settings • Humans attempt to stop/hinder succession
Climax Community • A stable group of plants and animals that is the end result of the successionprocess • The “textbook” ecosystem for that biome • Does not always mean big trees • Grasses in prairies • Cacti in deserts
Aquatic Succession • Succession also occurs in aquatic ecosystems, especially lakes and ponds • Primary: Lakes fill in for the first time • Ex: glacier retreats and melts, creating lake • Secondary: Over time, lakes and ponds fill with runoff / sediment and decaying organisms
Eutrophication • Occurs when excessive nutrients enter an aquatic ecosystem and stimulate rapid producer growth • Natural process, but humans ACCELERATE. • Excessive fertilizers (N and P) used on lawns, golf courses, farm fields that runoff into local waterways.
Eutrophication • Excess Nitrogen and Phosphorus enter lake. • Algae LOVE N&P- algae reproduces fast and furiously, called “algae bloom” • As algae take over, they die and sink, decomposers use up oxygen to break down. • Algae mats on surface also block sunlight, killing more organisms, and giving decomposers more to eat. • Over time, water body becomes hypoxic, or starved of oxygen, thus dead and unusable to life • Hypoxic zones harbor bacteria that emit dihydrogen sulfide (rotten-egg gas), a poison for other life. These areas are sometimes called dead zones.
http://youtu.be/L2ImgVwv5qM https://www.youtube.com/watch?v=6LAT1gLMPu4
Summary • Primary vs. Secondary Succession • Change is a certainty in life, even in climax communities • Nature bounces back from disturbances, but it takes a long time • Humans try to prevent succession on land, but promote it indirectly in lakes through eutrophication.
