Biology 2B - Ecology

1. Biology 2B - Ecology Communities and biomes

2. Ecosystems Ecosystem is a term that describes ecological systems consisting of interacting organisms and their physical environment Abiotic factor Non living factors eg temperature, rainfall Biotic factor Living factors eg predation, competition Community All the organisms in an ecosystem Environment All the abiotic factors Habitat Particular area in which a population lives Population All the organisms from one species in an ecosystem

3. Aquatic habitats Aquatic habitats come in many forms: lakes, rivers, wetlands, marshes, lagoons, streams, rivers, and swamps. Where freshwater mixes with saltwater you'll find mangroves, salt marshes, and mud flats. Seas and oceans stretch from pole to pole and reach around the globe. They cover more than 70 percent of the Earth's surface and hold in excess of 300 million cubic miles of water. Scattered throughout these vast waters are islands. Coral reefs are made up of millions of tiny coral polyps -- animals that together form vast colonies and secrete the limestone deposits. Reefs form in shallow, warm-water seas around the world. There are several types of reef including barrier reefs, fringe reefs, and atolls. Beaches and coasts lie at the threshold between land and sea where wildlife adapts to a constantly changing coastline and sways to the rhythms of the tides.

4. Terrestrial habitats Deserts and scrublands are landscapes that have scarce precipitation. Scrublands are semi-arid habitats that are dominated by scrub vegetation such as grasses, shrubs, and herbs. Forests and woodlands are habitats dominated by trees. There are many different types of forests—temperate, tropical, cloud, coniferous, boreal. Tundra is a cold habitat characterized by low temperatures, short vegetation, long winters, brief growing seasons, and limited drainage. Arctic tundra is located near the North Pole and extends southward to the point where coniferous forests grow. Alpine tundra is located on mountains around the world at elevations that are above the tree line. Alpine, or montane, habitats occur in highlands and mountain ranges around the world. 

5. Structural classification of communities

6. Biomes Communities with similar abiotic factors have similar characteristics, although they contain different species of plants and animals.

7. Characteristics of terrestrial biomes

8. Changes in communities Ecosystems change: Abiotic factors may vary – eg light, water, temperature, salinity, tides These may vary cyclically eg day/night; monthly, seasonally, over longer periods, or catastrophically (eg fire, flood, volcanic eruption, ice age, etc) Biotic factors may vary – Numbers of • Producers • Prey species (1st order consumers) • Predators(high order consumers)

9. Everything in an ecosystem is linked • A change in one factor can lead to changes in other factors – this is called the domino effect eg decreased rainfall  decrease in vegetation  decrease in herbivores (prey species)  decrease in predators eg removal of predators (hunting or biomagnification)  increase prey species (plague)  decrease vegetation  decrease in herbivores due to no food • Key species a species whose removal negatively affects an entire ecosystem eg otters in kelp forests – when hunted to extinction, sea urchin numbers increased so much that they destroyed the kelp  decrease in the other species depending on kelp for food or shelter

10. Changes in ecosystems – human interference Human presence  disrupts ecosystems in many ways including: • Loss of predators  removal of predators (sg spiders, wolves) can lead to population explosions of prey species • Introduction of new carnivore eg foxes, cats, dogs  loss of native wildlife • Introduction of new herbivore  eg rabbit, sheep, may out-compete natives  loss of native species; may cause over grazing as no native predators erosion • Introduction of new producer  eg brambles, prickly pear,may out compete natives (as often not edible to consumers)  loss of native plant and animal species (now not enough food for them); aquatic plants eg duckweed may block rivers

11. Changes in ecosystems - water • Damschanges distribution of populations in ecosystems – can get animals accumulating around dams  over grazing near the water source; loss of original ecosystem in flooded area • Presence of bores lowers water table; increases number of animals around bore  over grazing near the water source • Tailing dams  kills wildlife that tries to use it as water • Removing water for human use  lowers amount of water in river/streams eg Murray  not enough water to maintain ecosystem • Filling in wetlands  destroys ecosystem; loss of habitat for migrating birds; damage to neighbouring ecosystems as wetlands act as filters to remove pollutants and excess nutrients

12. Changes in ecosystems - clearing Loss of trees  loss of habitat & nesting places as well as the following • Loss of topsoil  (= erosion)loss of fertility  decreased producers  decreased biomass in the whole ecosystem • Rise of water table  water logging in low lying areas, increased soil salinity as salts are brought up with the water • Increased soil salinity  loss of fertility  decreased producers  decreased biomass in the whole ecosystem • Increased water salinity  loss of fertility  decreased producers  decreased biomass in the whole ecosystem; poisoning of consumers, loss of aquatic life

13. Changes in ecosystems -agriculture Farming  agricultural practices include • Monoculture  presence of only one species in the crop, decreases biodiversity, encourages population explosions or plagues of pest species eg mice, locusts, in the long term reduces soil fertility • Killing insects (eg pesticides)  disrupts ecosystems by destroying food source of higher order species (eg owls, wattle birds); can lead to ecological magnification • Loss of dead/decaying matter  loss of fertility, loss of decomposers  soil problems  reduction in producers  reduction in consumers • Fertiliser use  chemical poisoning of plants or animals (eg high phosphate fertilisers kill many native trees; run-off into rivers can cause eutrophication (algal blooms)

14. Changes in ecosystems – climate change Climate change  changes in temperature, rainfall & humidity – also affects water availability • Increased temperature  increased water loss  higher water needs; may cause death of organisms if temperature too high; rising sea levels (thermal expansion of water) and melting of glaciers and polar icecaps may also impact on ecosystems • Decreased rainfall  reduced water availability  decreased biomass (less plants  less animals) • Reduced water table  dries out seasonal water sources (eg swamps, small creeks) and cave systems, less water  decreased biomass (less plants  less animals) • Change in seasons  organisms may not be able to find enough food to survive & raise offspring egbirds breed as light levels change, insects breed as temperature rises