Option C Ecology & Conservation

Introduction Community is a group of populations living together in an area. The distribution of organisms within a community is determined by biotic and abiotic factors. Biodiversity is important for survival Soil is important for health and growth of all populations

C.1 Species and Communities Limiting factors determine where and how many organisms live in an area. Abiotic factors: light, atmosphere, water, temperature, salinity, soil conditions (Ph, composition) Biotic factors: other organisms, relationships between other organisms (symbiosis, parasitism, predator-prey etc, competition for resources.

Shelford’s Law of tolerance: distribution od a species in an ecosystem is determined by the limits of physical and chemical factors that can be tolerated. Bell curve – most are in optimum area, as you move towards the extremes (zones of stress), fewer organisms.

Example from book, 3 species of kangaroos, climate is limiting factor Example from book, 3 species of kangaroos, climate is limiting factor. They each have a rainfall and temperature they do best in so they live in different areas. Example from book, plant Genus Encelia. There are 4 different species in southern California, each has an optimum temp and water need and live in different areas.

E. frutescus lives in the hottest and dryest area. Has several adaptations to allow this. High transpiration rate to cool by evaporation. Deep roots for moisture

Keystone species Not necessarily the most abundant, by has strong control over the structure of a community. Removal experiment determines which species this is. Robert Paine experimented by removing starfish from an area, diversity fell from 15-20 species down to 5. Without the starfish, mussels took over.

Habitat is where an organism lives, niche is habitat and what it does there, where it lives, what it eats, interactions with other species. Spatial habitat – every type of organism has a unique space in the ecosystem. Feeding activities – affects ecosystem by keeping populations in check.

Interactions with other species Competition, herbivory, predation, parasitism, and mutualism. Any organism can do more than one. Competition: two species rely on same limited resource, one will be better adapted. Coyotes eat rodents in grasslands, foxes in forests. When in same area, they have problems

Herbivory – primary consumer feeding on producer. Predation – predator is consumer, eating another consumer (prey). They keep each other in check. Lynx and hare are example. Parasitism – An organism that lives on or in a host, depending on the host for food, and possibly harming the host. Ex: plasmodium malaria, leeches

Mutualism – two species living together with both benefiting. Examples: algae/fungus-lichen Rhizobium bacteria and roots of legumes Clown fish and anemone

Competitive Exclusion No two species in a community can occupy the same niche. Fox and coyote example from earlier, one needs to move or become extinct G.F. Gause experiment with paramecium

Fundamental vs realized niche Fundamental niche is the area where an organism could live, where the realized niche is where it does live due to competition. Transect line used to correlate organism with abiotic variable.

C.2 Communities and Ecosystems Energy flow through the ecosystem Food chain producer…cow…human Producers are at the bottom and have the most energy from sun or bacteria w/chemicals Only 5-20% is transferred to primary consumer. Examples use 10% 80-95% lost as heat, or used by the plant

Gross vs net production Gross production is the total amount of energy created by the plant. Net production is when you subtract the amount of that energy the plant uses for respiration. Biomass – the dry weight of all organisms at a certain level of an ecosystem. The higher the trophic level, the lower the total biomass.

Difficulties classifying into trophic levels Food webs – organisms can consume at different trophic levels depending on what they are eating. Omnivores eat everything, anything. Different ecosystems have different numbers of trophic levels, most have 3 or 4, some have 5 but that’s usually the top end.

Feed Conversion Ratio How efficient an animal is in converting food into body mass. Mass of food eaten = FCR lower=more body mass gain efficient Larger animals usually have a higher # Fish farming has very low FCR

Primary Succession Plants begin growing on area that has never had growth before, usually volcanic island. Sand dunes are another example. Usually very little soil Lichens are usually one of the first things and they can break down rock and create soil. Mosses are usually next

Secondary Succession New growth in an area that is starting over, like after a fire. Happens much faster because there is already soil and could still be viable seeds.

Species diversity in Primary Succession Dunes are an example of primary succession Foredune = nearest the beach, no soil, just sand. This is where primary succession begins. Grasses are pioneer plants (first to appear). Not very diverse, mostly Marram grass Yellow Dune = developing a thin layer of soil (humus)from decomposing Marram grass. A few more species of plants, rabbits eat grasses an leave droppings

Grey Dune – layer of humus from years of plant decay. Humus holds water, shrubs begin to grow Mature Dune – supports forests, wild flowers, mosses ferns Cooler than other dune areas

Overall changes to dunes Few species to many Pioneer species to many that compete for nutrients Little diversity to high diversity Simple relationships to complex like mutualism, competition and predation. More and more biomass at each stage. The stable community that will emerge depends on the climate and is called a climax community. (Biome)

Biosphere and biomes Biosphere is the area of the Earth where there is life. Includes under the ground and in the air. Biomes are divisions of the biosphere, defined by its vegetation and community structure, caused by temp and rainfall Tundra, coniferous forest, temperate forest, desert, tropical forest

Tundra High elevations, low temp, low precipitation. Cold and Dry Coniferous forest – High elevations, slightly warmer and slightly more precipitation than tundra. Adapted to conserve water due to frozen ground. Animals have lots of fur in winter lose some in summer.

Temperate Forest – lower elevations, warmer temps and more water Temperate Forest – lower elevations, warmer temps and more water. Much more diversity in organisms, wider range of conditions. Seasons. Desert- lower elevations, warm temperatures, little precipitation. Organisms very specifically adapted to the heat and lack of water.

Tropical forest – lower elevations, warm temperatures, high temperatures. Very high productivity.

Gersmehl diagrams Diagrams that show energy flow and nutrient recycling in a biome. Main location of stored energy is in soil, (biomass) plants, and litter. Arrows show nutrient transfer, circles show stores. Also show input of nutrients, ex: (from weathering of rock), output, ex: (run-off), flows or movement such as leaves falling and changing from biomass to litter.

Humans interfering with nutrient cycle An example is overfishing and habitat loss of the fisheries. Fish help to recycle nutrients such as nitrogen and phosphates to be used by microorganisms and plants. 80 of nutrients used by producers are supplied by fish. Removal of fish impacts producers, nitrogen supplied by fish in unfished areas was found to be 451% higher than fished areas.

Closed ecosystems Most ecosystems are open, exchanging energy and matter into and out of the system. Closed systems exchange energy but not matter. Individual systems are open but the Earth as a whole is considered almost closed. Artificial closed systems have been created: Space station, Biosphere

Disturbances to ecosystems A disturbance is considered a new environmental condition that affects structure and rate of change. Examples: natural – fire, flood, wind, insect invasion. Human – clearing forests, building roads, ploughing fields, building homes

Joseph Connell 1975, Connell proposed that disturbance is common and can be beneficial to species diversity. After a fire, there are more species than before. Low levels and high levels are bad for diversity but intermediate disturbance is good.