APES: Chapter 7 & 8 Reading Guides

Terms in this set (41)

Some major impacts of human activities on marine systems:
-Salt marshes, mangrove forests, and sea grass meadows-the seas three great marine nurseries-are being lost and degraded at a high rate to make way for real estate developments, marinas, golf courses, and shrimp farms
-It is estimated that half the world's coastal wetlands and 53% of those in the lower 48 U.S. states (91% in California) have disappeared since 1800, mostly by being filled in for agriculture and coastal development. According to scientists, by 2080 half of the worlds remaining coastal wetlands is likely to be lost to agriculture, urban development, and rising sea levels from climate change.
-At least 35% of the world original mangrove forests have disappeared since 1980, mostly because of clearing for coastal development, rice fields, and agriculture shrimp farms.% of mangrove forest loss> those for tropical rain forests and coastal reefs. Much of the remaining mangrove forests are threatened. The clearing of mangroves also causes erosion that kills coral reefs by smothering the corals in plumes of soil.
-According to a WWF study, almost 70% of the world's beaches are eroding rapidly because of coastal developments and a rising sea level (caused mostly by global warming)
-Ocean bottom habitats are being degraded and destroyed by dredging operations and trawler boats, which drag huge nets weighed down with chains over ocean bottoms to harvest bottom fish and shellfish.
-According to a 2000 report from the Global Coral Reef Monitoring Network, about 27% of the world's coastal reefs have been severely damaged (up from 10% in 1992), 11% have been destroyed, and another 70% could be gone by 2050. In addition to the biodiversity losses, such a collapse would sharply reduce fish harvest and greatly increase storm damage on the coasts of tropical and warm temperate areas.
-Source zone: in this first and narrow zone, head water or mountain highland streams of cold, clear water rush over waterfalls and rapids. As this turbulent water flows and tumbles downward, it dissolves large amounts of oxygen from the air so photosynthesis is a less important source of oxygen than it is in ponds and lakes. Plants such as algae and mosses are attached to rocks and the zone is populated by cold-water fish (trout) which need lots of dissolved oxygen. Many fish and other animals have compact and flattened bodies that allow them to live under stones.
-Transition zone: the headwater streams merge to form wider, deeper streams that flow down gentler slopes with fewer obstacles. The warmer water and other conditions in this zone support more producers (phytoplankton) and a variety of cool-water and warm-water fish species (black bass) with slightly lower oxygen requirements.
-Floodplain zone: streams join into wider and deeper rivers that meander across broad, flat valleys. Water in this zone usually has higher temperatures and less dissolved oxygen than water in the first two zones. These slow-moving rivers sometimes support fairly large populations of producers such as algae and cyanobacteria and rooted aquatic plants along the shores. Because of increased erosion and runoff over a larger area, water in this zone often is muddy and contains high concentrations of suspended particulate matter (silt). The main channels of these slow-moving, wide, and murky rivers support distinctive varieties of fish (carp and catfish), whereas their backwaters support species similar to those present in lakes. At its mouth, a river may divide into many channels as it flows through coastal wetlands and estuaries, where the river mixes with ocean water.
Intraspecific competition:
-Some plants secrete chemicals that inhibit the growth of seedlings of their own and other species
-Other plant species compete with other members of their species for living space and nutrients by dispersing their seeds to other sites by air (wind), water, and animals.
-Territoriality: patrol or mark an area around their home, nesting or major feeding site and defend it against members of their own species.
Interspecific competition:
-With significant niche overlap, one of the competing species must migrate to another area (if possible), shift its feeding habits or behavior through natural selection and evolution, suffer a sharp population decline, or become extinct in that area.
-Interference competition: in which one species may limit another's access to some resource, regardless of its abundance, using the same types of methods found in intraspecific competition. For example, a territorial hummingbird species may defend patches of spring wildflowers from which it gets nectar by chasing away members of other hummingbird species. In desert and grassland habitats, many plants release chemicals into the soil. These chemicals prevent the growth of competing species or reduce the rates at which their seeds germinate.
-Exploitation competition: in which competing species have roughly equal access to a specific resource but differ in how fast or efficiently they exploit it. The species that can use the resource more quickly gets more of the resource, and hampers the growth, reproduction, or survival of the other species.
Ecologists recognize two types of ecological succession, depending on the conditions present at the beginning of the process:
-Primary succession involves the gradual establishment of biotic communities on nearly lifeless ground. Begins with an essentially lifeless area where there is no soil in a terrestrial ecosystem or no bottom sediment in an aquatic ecosystem. Examples include bare rock exposed by a retreating glacier or severe soil erosion, newly cooled lava, an abandoned highway or parking lot, a newly created shallow pond or reservoir. Before a community of plants, consumers, and decomposers can become established on land, there must be soil, which depending on the climate can take natural processes several hundred to thousand years to produce fertile soil. Soil formation begins with hardy pioneer species (lichens and mosses) attach themselves to inhospitable patches of bare rock. The soil formation process starts by trapping wind-blown soil particles and tiny pieces of detritus, producing tiny bits of organic matter, and secreting mild acids that slowly fragment and break down the rock, in addition to physical weathering. Then when the situation becomes suitable enough early successional plant species (small perennial grasses, herbs) which grow close to the ground, can establish large populations quickly under harsh conditions, and have short lives begin to thrive. Eventually, midsuccessional plant species (herbs, grasses, and low shrubs) begin to grow and then late successional plant species (mostly trees) that can tolerate shade. Unless fire, flooding, severe erosion, tree cutting, climate change, or other natural or human processes disturb the area, what was once bare rock becomes a complex forest community.
-Secondary succession, the more common type, involves the reestablishment of biotic communities in an area where some type of biotic community is already present. Begins in an area where the natural community of organisms has been disturbed, removed, or destroyed but some soil or bottom sediment remains. Candidates include abandoned farmlands, burned or cut forests, heavily polluted streams, and land that has been damned or flooded. Due to the presence of some soil or sediment, new vegetation can usually begin to germinate within a few weeks. Seeds can be present in the soils, or they can be carried from nearby plants by wind or by birds and animals. Changes in vegetation affect food and shelter for various types of animals, and as succession proceeds the number and types of animals and decomposers also change.
;