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Terms in this set (58)
What are the majority of plants and algae
The majority of plants and algae are autotrophic, meaning they produce their own food through photosynthesis.
What are a small percentage of plants and algae
A small percentage (1%) of plants and algae obtain carbon compounds from other organisms - either by growing on them and stealing the nutrients from the plant they are growing on or by consuming dead organic material.
Since they obtain these carbon compounds from other species and cause them harm, they are considered parasitic.
A group of organisms that share common ancestry and that can interbreed and produce fertile, viable offspring
A group of organisms of the same species who live in the same area at the same time
Two populations of the same species can live in two different areas and are unlikely to interbreed; however, they are still part of the same species if they could potentially interbreed
An organism that synthesizes its own organic molecules (makes their own food eg. carbon, hydrogen, oxygen, nitrogen and phosphorus) from simple inorganic substances in the abiotic environment
Autotrophs are producers.
Usually autotrophs convert light energy to chemical energy through photosynthesis.
An organism that obtains organic molecules from other living organisms or their dead remains.
Obtain sodium, potassium, calcium from inorganic sources
Obtain carbon and nitrogen from organic sources
Heterotrophs consume other organisms because they cannot make their own food.
Some unicellular organisms use both methods of nutrition
Eg. Euglena gracilis - have chloroplasts to carry out photosynthesis when there is enough sunlight; however, they can also feed on detritus (dead or decaying material) or other smaller organisms.
A consumer is an organism that ingests other organic material that is living or has been recently killed.
Consumers feed off other organisms by ingesting their food, then digesting it and absorbing these products of digestion
Primary consumers feed off autotrophs (example: Eastern Grey Squirrel feeds of mostly nuts/acorns)
An organism that obtains food by ingesting non-living organic matter
(They are heterotrophs that specifically obtain their organic nutrients from detritus (waste) by internal digestion.)
Eg. Vultures and earthworms.
Organisms that live on or within nonliving organic matter, secreting digestive enzymes into it and absorbing the nutrients produced by digestion. Saprotrophs help with the decaying or break down of dead organic materials.
(Saprotrophs are heterotrophs that specifically obtain their organic nutrients from dead organisms by external digestion.)
A group of populations living and interacting with each other in an area. Basically it means all living things in a habitat.
A community which consists of all the biotic factors (living things such as plants and animals in an area, functioning together with all of the physical or abiotic (non-living) factors of the environment eg. water temperature, currents, available nutrients.
Ecosystems are largely self-contained and self-sustaining units that can exist over long periods of time.
The environment in which a species normally lives or the location of a living organism
The study of relationships between living organisms and between organisms and their environment
What is meant by a food chain
A food chain shows the linear feeding relationships between species in a community
The arrows represent the transfer of energy and matter as one organism is eaten by another (arrows point in the direction of energy flow)
The first organism in the sequence is the producer, followed by consumers (1°, 2°, 3°, etc.)
What is meant by a food web
A food web is a diagram that shows how food chains are linked together into more complex feeding relationships within a community
There can be more than one producer in a food web, and consumers can occupy multiple positions (trophic levels)
Define trophic level
An organism's trophic level refers to the position it occupies in a food chain
Producers always occupy the first trophic level, while saprotrophs would generally occupy the ultimate trophic level of a given food chain or food web
Reason for the shape of pyramids of energy
A pyramid of energy is a graphical representation of the amount of energy of each tropic level in a food chain
They are expressed in units of energy per area per time
Pyramids of energy will never appear inverted as some of the energy stored in one source is always lost when transferred to the next source
Each level of the pyramid of energy should be approximately one tenth the size of the level preceding it, as energy transformations are ~10% efficient
Main requirements for sustainability in an ecosystem
- Nutrient availability (nutrients such as carbon and nitrogen can be recycled indefinitely as long as the proper conditions exist)
- Detoxification and recycling of waste products
- Energy availability (energy cannot be recycled - must be in constant supply)
Today conservation attempts to manage and sustain the environment so that a balance is maintained, despite human activities. This may include limiting consumption and effective population control in certain areas of the world
Plot-based (quadrat) methods are often used to study populations of different species within a certain area.
Quadrats are generally square sample areas marked out using a framed structure.
Quadrats are placed in a marked out habitat according to random numbers obtained using a random number table or a random number generator on a calculator
Positively associated species
If two different species are found in the same habitat and within the same quadrat, they are positively associated. This basically means that one species is more likely to be found, when the other species is also present
Negatively associated species
A negative association is when two species tend not to occur together.
If there is no association between the two species, negative or positive, the species are said to be independent. Basically this means that the location of species A has no effect on species B and vice versa.
One can test these associations using a chi-squared test (called Chi Square Test for Independence)
3 different quadrat methods
1) Estimating percentage cover "by eye"
2) Repeat using 4 square overlay, record each result and mean
3) Record hit or miss for 100 points using the 100 point overlay. (most effective)
Since there is a limited supply of nutrients on earth, chemical elements are constantly recycled after they are used.
Energy enters and leaves ecosystems, but nutrients must be recycled
Energy cannot be recycled and an ecosystem must be powered by a continuous influx of new energy from an external source (e.g the sun)
Nutrients refer to material required by an organism, and are constantly being recycled within an ecosystem as food (either living or dead)
The autotrophic activities of the producers (e.g. plants) produce organic materials from inorganic sources, which are then fed on by the consumers
When heterotrophic organisms die, these inorganic nutrients are returned to the soil to be reused by the plants (as fertiliser)
Saprotrophic bacteria and fungi (decomposers) recycle nutrients
In order for organisms to grow and reproduce, they need a supply of the elements of which they are made
The saprotrophic activity of decomposers (certain bacteria and fungi), free inorganic materials from the dead bodies and waste products of organisms, ensuring a continual supply of raw materials for the producers (which can then be ingested by consumers)
Thus saprotrophic bacteria and fungi play a vital role in recycling nutrients within an ecosystem
Ecosystems require a continuous supply of energy to fuel life processes and to replace energy lost as heat.
In food webs and communities all interactions between the organisms requires energy.
There is a continuous but variable supply of sunlight energy.
Sunlight provides the initial energy source for almost all communities. Sunlight energy is converted to useable chemical energy by autotrophs through photosynthesis.
All green plants, and some bacteria, are photo-autotrophic - they use light as a source of energy for synthesising organic molecules
This makes light the initial source of energy for almost all communities
Autotrophs that harvest the light energy and produce chemical energy through photosynthesis are called producers.
Heterotrophs role in food web
Autotrophs (producers) have converted light energy into chemical energy via photosynthesis
Heterotrophs (consumers) feed on other organisms in order to obtain their energy
Conversion of light energy
Producers absorb light energy using chlorophyll and other photosynthetic pigments
Producers then release chemical energy using cellular respiration and use it for cellular activities; some energy lost as heat. The energy remaining in the cells and tissues is available for consumers
1) Primary consumers consumers feed on the producers. Only around 10%-20% of the energy from the producer is passed on to the primary consumers. The rest of the energy is lost as heat through cell respiration, death and waste.
2) Secondary consumers feed on the primary consumers. Again only 10%-20% of the energy is passed on to the next level, with the rest lost as heat through respiration, death, and waste.
3) Tertiary consumers feed on secondary consumers. 10%-20% is passed on to the tertiary consumer and the rest is lost as heat, death and waste.
ATP provides energy needed for cellular activities.
ATP is produced through cellular respiration, which involves the oxidation of carbohydrates and lipids. These reactions are exothermic.
ATP can be used quickly for the cellular activities eg. protein synthesis, pumping ions or molecules across membranes
These reactions are not 100% efficient, therefore some of the energy produced in these oxidation reactions is lost as heat. Some heat can also be produced during cellular activities
Organisms can perform a variety of energy conversions,
Eg. light to chemical energy during photosynthesis, chemical energy to KE during muscle contractions
Organisms cannot turn heat energy into any other forms of energy
Heat resulting from cellular respiration makes an organism warmer.
Cold-blooded organisms can become more active
Warm blooded animals can increase their rate of heat generation in order to maintain their in internal body temperature
Eventually though, since heat passes from warmer to colder bodies (thermodynamics), all heat is lost from the ecosystem
Limited food chain length
Food chain length is limited by the amount of energy available.
- Most energy in food that is consumed, digested and absorbed by organisms for a certain trophic level is released by them during cellular respiration used in cellular activities and is therefore lost as heat.
- At each level, when an organism is consumed some parts might not be eaten or consumed
- Not all food is digested or absorbed fully. Indigestible food is excreted in faeces.
- Some organisms might die before they are eaten or consumed. This waste and dead organic material forms detritus which is non-living particulate organic material.
The detritus is then broken down and the stored energy is used by decomposers or consumed by detritivores.
Some energy can be trapped as fossil fuels or peat.
The units of measurement for a pyramid of energy
(energy per unit area per unit time)
Autotrophs and carbon dioxide
Autotrophs such as plants and algae, convert inorganic carbon dioxide into organic carbohydrates, lipids and all other carbon based compounds through photosynthesis.
This reduces the carbon dioxide concentration in the atmosphere.
Carbon in aquatic ecosystems
Carbon dioxide dissolves in water and some of it will remain as a dissolved gas
Some of the carbon dioxide will combine with water to form carbonic acid
CO2 + H2O <--> H2CO3.
Carbonic acid can then disassociate to form H+ and HCO3-
(H2CO3 <-->HCO3− + H+)
The pH decreases
Autotrophs in water absorb both CO2 and hydrogen carbonate ions, and use them to produce organic compounds
Carbon dioxide concentration gradient
Since autotrophs use carbon dioxide for photosynthesis, as the CO2 is depleted by the autotroph, the concentration of CO2 in the surrounding atmosphere or water is greater than inside the autotroph; therefore a concentration gradient is created
Carbon dioxide diffuses into the autotroph, following the concentration gradient created
Release of carbon dioxide
All organisms carry out cellular respiration and produce carbon dioxide as a waste product
This CO2 will be released by these organisms through diffusion into the atmosphere or water, depending if they are terrestrial or aquatic organisms
Methane is widely produced in anaerobic conditions as a waste product of a certain type of anaerobic respiration called methanogenesis
These reactions occur without oxygen in swamps, wetlands and mangroves, in mud along the banks of rivers and lakes, and in the digestive tracts of mammals and termites.
With large herds of domestic cattle and sheep being raised worldwide, there is concern that all the methane being produced is contributing to the greenhouse effect
Methane in the atomosphere
Methane is the main ingredient in natural gas.
When you burn methane the reaction involves oxygen from the atmosphere which produces carbon dioxide and water
When methane is actually released into the atmosphere through the anaerobic reactions, it can persist in the atmosphere for about 12 years, as it is naturally oxidized by monatomic oxygen (O) and hydroxyl radicals (OH-)
This is why methane concentrations are not very great in the atmosphere, even though large amounts are produced
Peat, which is partially decomposed plant material, is an organic substance that can be used as a fossil fuel.
Many soils, saprotrophic bacteria and fungi digest organic material from dead leaves and plants; however, oxygen (air spaces in the soil) is needed for cellular respiration.
In muddy, water-logged environments, these air spaces might not be present and therefore anaerobic conditions exist - acidic conditions further inhibit decomposers
The organic material is therefore not fully decomposed, as energy rich molecules that would have been fed upon by saprotrophs and methanogens are left behind - peat is formed
Peat conversion into coal
Partially decomposed peat when put under extreme weight, pressure and heat from above sediments can be transformed into coal
This transformation takes place over millions of years
The pressure and heat cause lithification (the transformation of sediments into solid rock)
Oil and gas are formed at the bottom of oceans, seas and lakes over millions of years
Carbon dioxide combustion
Carbon dioxide is produced by the combustion of biomass and fossilized organic matter.
When organic compounds rich in hydrocarbons are heated and reach their ignition temperature in the presence of oxygen they undergo combustion (burning). This is an oxidation reaction.
The products of combustion are carbon dioxide and water
Calcium carbonate in animals
Animals such as coral and mollusca (clams etc.) contain body parts made out of calcium carbonate (CaCO3)
The calcium carbonate from these organisms settle onto the seafloor when they die
Through lithification (the transformation of sediments into solid rock), these sediments form limestone.
The hard parts of many of these animals are visible as fossils in the limestone rock
The greenhouse effect
The greenhouse effect is the earth's ability to use its atmosphere to retain heat and keep warm even when no sun is hitting the surface, due to the the presence of an atmosphere containing eg. CO2 and water vapour that absorb and radiate heat.
CO2 and water vapour on the greenhouse effect
The gases that have the greatest impact on the warming effect on earth are CO2 and water vapour
Carbon dioxide is released into the atmosphere by cellular respiration by organisms and combustion of organic materials and burning of fossil fuels. It is removed by photosynthesis and absorption by the oceans
Water vapour is created by evaporation of the water in oceans, seas and lakes and transpiration by plants. It is removed through precipitation.
Methane and nitrous oxide on the greenhouse effect
Methane has the third greatest impact on the greenhouse effect
It is emitted from marches, other water-logged habitats and from landfill sites containing organic wastes
Nitrous oxide, which is another significant greenhouse gas is released naturally by bacteria in some habitats and also by agriculture and vehicle exhaust
All the greenhouse gases together make up less than 1% of the earth's atmosphere
Factors that determine how much of an influence a gas will have on the greenhouse effect
The two factors that determine how much of an influence a gas will have on the greenhouse effect are:
- The ability of the gas to absorb long-wave radiation (heat)
- The concentration of the gas in the atmosphere
Methane actually has the ability to cause much more warming per molecule than carbon dioxide; however, there is a much lower concentration of methane in the atmosphere
Light entering earth's atmosphere
When light (shorter wavelengths) enters the earth's atmosphere, some of the light reflects off the earth's surface back towards outer space.
Some of the light is converted into heat, which in turn warms the surface of the earth.
This heat (longer wavelengths) radiates off the earth back towards the atmosphere.
Longer wave radiation is absorbed by greenhouse gases that retain the heat in the atmosphere.
Greenhouse gases such CO2 and water vapour absorb this heat (infrared radiation) trapping it within the atmosphere, further warming the earth.
70-75% of the solar radiation reaches the earth's surface, with a high percentage of this radiation being converted into heat
As the infrared radiation is reflected back off the earth, a large percentage of this heat is captured by the greenhouse gases in the atmosphere. This energy is re-emitted, thus heating up the earth's atmosphere. This effect is called global warming.
The ability of the earth's surface to reflect light is called the albedo effect.
Light coloured and white objects such as snow and ice, have a high albedo and therefore little light is absorbed and less heat is produced. Black and dark coloured objects like asphalt and pavement have a low albedo, and therefore absorb more light and produce more heat.
With the spread of urban cities and areas, a greater amount of heat is being produced
Recording climate change
Climate refers to the patterns of temperature and precipitation that occur over long periods of time. Climate changes over thousands or millions of years
Climatologists and palaeoclimatologists collect and study data about atmospheric conditions in recent decades and from the distant past in order to infer what the climate was like thousands to millions of years ago
Since greenhouse gases cause the earth to retain heat, one can infer that the more greenhouse gas there is in the atmosphere, the warmer the earth will be.
This does not mean that the amount of greenhouse gas is the only reason for the earth warming and cooling; however, there is a correlation between the earth's temperature and the amount of greenhouse gas
Increasing amounts of CO2
Since the industrial revolution the amount of CO2 has drastically increased, largely due to the increasing quantities of combustion of fossilised organic matter (coal, oil and natural gas)
- One source of carbon emissions due to human activities is through combustion of fossil fuels in automobiles, buses and planes.
- Another source of carbon dioxide is the deforestation through burning large tracks of land and heating homes with fossil fuels, such as natural gas
- Humans demand for meat has led to large numbers of cattle, which is responsible for releasing methane into the atmosphere, which is changed into carbon dioxide
What are mesocosms
Ecosystems have the potential to be sustainable over long periods of time. As long as nutrients are recycled ecosystems only require a supply of energy, usually in the form of light, to continue indefinitely. This can be demonstrated by setting up a mesocosm.
This is a small experimental area set up in an ecological research programme.
Clear glass jar - so light can penetrate.
Seal - to prevent entry or exit of chemical substances
Air - O2 and CO2
Soil - for living organisms
Living organisms in mesocosms
Autotrophs - produce carbon compounds and regenerate oxygen used in cell respiration by organisms in the mesocosm
Saprotrophs - decompose dead organic matter and recycle nutrients
(Autotrophs and saprotrophs are essential to mesocosms, consumers and detrivores aren't)
Consumers and detrivores are normal parts of an ecosystem so are usually included - unethical to include large animals in mesocosm that cannot obtain enough food or oxygen
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