ECOLOGY Flashcards
MODES OF NUTRITION
Autotroph (producer): An organism which uses inorganic raw materials and an external energy source to make up complex organic compounds. Examples may include all plants (i.e. corn), and phytoplankton (algae).
Heterotroph (consumer): An organism that obtains energy and organic matter from other organisms. All animals (i.e. rabbit, lion) are heterotrophs AND some plants also (i.e. dodder)
Detritivore (decomposer-consumer): An organism that ingests (swallows) fresh or decaying dead organic matter and digests it internally. Examples: earthworms, slugs, snails, woodlice.
- COMMUNITIES AND ECOSYSTEMS
Ecology : The study of the relationships between living organisms and between them and their environment.
Species : A group of organisms which could interbreed and produce fertile offspring.
Population: A group of organisms of one species occupying a defined area at the same time and capable of interbreeding.
Community: A group of populations living and interacting with each other in a habitat.
Habitat: The typical environment of a particular organism, population community or ecosystem. On the grand scale, Earth has four major habitats, that is, marine, estuarine, freshwater and terrestrial.
Ecosystem: A community of organisms and their physical environment interacting as an ecological unit. The organisms of the ecosystem make the BIOTIC component of the ecosystem, while the non-living surroundings (soil, water, climate, light) make the ABIOTIC component of the ecosystem.
The different ecosystems are united to form the BIOSPHERE, which includes all the living organisms and the physical environment with which they interact. The biosphere extends about 8km above sea level and 10km below it. It consists of two major divisions, the AQUATIC (freshwater, marine and estuarine) and the TERRESTRIAL (further divided into biomes)
Food Chains: The energy that organisms contain is passed along chains of organisms known as food chains. For example the energy (carbohydrates, proteins, lipids) from grass, passes on to the rabbits and from the rabbits to the foxes that eat them.
Trophic level : The position an organism occupies in a food chain OR a group of organisms in a community that occupy the same position in food webs.
- ENERGY FLOW
The energy flows through an ecosystem by the following way:
3. ENERGY FLOW
• SOLAR energy is converted by PHOTOSYNTHESIS to chemical energy, which is used for growth and respiration (and lost as HEAT).
• CONSUMERS eat the producers, energy lost at each trophic level. Energy is also lost in faeces, urine and after death.
• DETRITUS pathways break dead organic matter, so ALL energy is finally lost as HEAT from the ecosystem.
Pyramids of energy
A pyramid of energy is a diagram, which shows the energy flow from one trophic level to the next for a specific food chain or food web. Pyramids of energy have always the following shape, they can never be INVERTED.
- RECYCLING OF NUTRIENTS IN ECOSYSTEMS
Energy flows though the trophic levels of an ecosystem, but nutrients recycle
between the living and the non-living components of the ecosystem.
Carbon sources in air and water
Carbon is fixed in organic molecules mostly during photosynthesis (by autotrophs).
Most of it is soon released by respiration as carbon dioxide (exhaled by animals or released from stomata by plants).
In the sea, CO2 is dissolved in water as bicarbonate ions (HCO3 -). CO2 + H2O→H2CO3→H+ + HCO3
Carbon fluxes
In the carbon cycle the arrows show FLUXES-transfers of carbon. The thickness of the arrows indicates the size of the flux.
The boxes in the cycle show SINKS-methods of carbon storage in ecosystems.
Carbon fluxes have been estimated by many measurements done in natural ecosystems and in mesocosms. Estimates are in gigatonnes per year(gt yr-1)
The greenhouse effect
The greenhouse effect is a phenomenon which resembles a cultivation greenhouse. The glasses in a greenhouse serve to trap the light from the sun which contains short wavelengths and prevent heat from escaping (long wave radiation). In a similar way gases such a carbon dioxide and others (greenhouse gases) trap the long wavelength radiation from the sun and allow the surface of earth and the atmosphere to warm up. Increased production of greenhouse gases, however, causes the rise of the earth’s temperature in a significant level.
• CARBON DIOXIDE
Sources of CO2 are: combustion of fossil fuels (oil, natural gas), deforestation,
(used to produce more land, or trees for timber), fires of forests • OXIDES OF NITROGEN (NO, NO2) AND SULFUR DIOXIDE (SO2)
Sources are: combustion of fossil fuels-gasoline in cars using organic and commercial fertilizers
• METHANE
Sources are: cattle ranching-from faeces and gases produced by intensive
farming, waste disposal in open landfills, leaks from natural gas distribution • WATER VAPOUR
Coming from natural evaporation
Carbon dioxide and water vapour are the most significant greenhouse gases.
Global temperatures and carbon dioxide concentrations
Carbon dioxide can be measured through drilling ice columns in Antarctica or in Greenland and using ice cores.
Measurements are possible now for a period up to 800,000 years before the present. During this period there has been a repeating pattern of rapid periods of warming followed by much longer periods of gradual cooling, which correlate very closely with changes in CO2 concentrations.
Ice cores contain an abundance of information
about climate. Inclusions in the snow of each year remain in the ice, such as wind-
blown dust, ash, pollen, bubbles of atmospheric gas and radioactive substances.
Global warming and climate change
There has been estimated that the mean temperature of the Earth’s surface would be -18oC without the greenhouse effect. Now it is 30oC so the climate patterns are definitely influenced by greenhouse gases. It is also clear that human activities are causing an increase in the concentrations of carbon dioxide and other greenhouse gases. Furthermore it has been observed that there is an increase in the global temperature over the last 200 years.
What is strongly disputed by some people is whether global warming and other climate changes are due to greenhouse gas emissions from human activity. This claim has been evaluated by many climate change scientists, and almost all have concluded that human activity is indeed influencing the global temperatures and climate patterns.
Coral reefs and carbon dioxide
Since the start of industrial revolution billions of tonnes of CO2 have been dissolved into the oceans changing their pH (it becomes slightly more acidic). Due to changes of carbonate ions into hydrogen carbonate ions, corals and other animals which produce a calcareous skeleton, will not be able to absorb enough carbonates for their skeletons. Building of coral reefs will be threatened and together entire ecosystems which depend on coral reefs.
