ecology and the environment Flashcards
4.1 what does the term population mean?
the total number of individuals of one species in a particular habitat at a particular time
4.1 what does the term community mean?
it’s formed of the populations of all the species present in an ecosystem at a particular time
4.1 what does the term habitat mean
the places where specific organisms live
4.1 what does the term ecosystem mean?
an easily described system or area where organisms interact with their physical environment
4.2 practical: investigate the population size of an organism in two different areas using quadrats
- calculate the area of the habitat
- measure number of individuals in 1 quadrat & repeat many times to check result is reliable (at least 10 quadrats needed) - random sampling to make sure data is valid
- calculate avg no. of individuals in a quadrat
- calculate how many quadrats fit into total area
- how many quadrats fit into total area x avg number of individuals in a quadrat
- repeat this in another area
4.2 practical: what do you do if an individual is on the edge of a quadrat?
so either count them as half or count those on top & left edges only to make data consistent
4.2 practical: if it’s difficult to count individuals for chosen species (e.g. grass) what do you do?
estimate the % of the quadrat area covered by the species, some quadrats divided into grids to help with this
4.2 practical: why do we do random sampling & how?
to make sure our data is valid, so avoiding choosing areas which may be interesting as it would bias our result
- lay out 2 tape measures at right angles to make 10m by 10m set of axes. generate pairs of random numbers between 0-10 (coordinates)
- use coordinates to place quadrat
4.5 what are some abiotic factors that affect the population size and distribution of organisms?
- light intensity
- one area may be trampled
- temperature
- CO2 and O2 concentrations
- minerals in soil
4.5 what are some biotic factors that affect the population size and distribution of organisms?
idk fill this in later
4.6 what does producer mean?
organisms which make their own food (e.g. photosynthesising plants)
4.6 what are consumers?
organisms which eat other living things (e.g. animals)
4.6 what are decomposers?
organisms which secrete digestive enzymes to decay (breakdown) dead organic matter to obtain their food; they help to recycle nutrients
4.6 what are primary, secondary and tertiary consumers?
the first animal in a food chain/web is the primary consumer, it usually eats the producer; the secondary is the second; tertiary is the third
what are the trophic levels?
the stages in a food chain/web
4.7 what are pyramids of number?
these are drawn to show the number of each organism counted in the ecosystem. they can be odd shapes due to the different masses of organisms
4.7 what are pyramids of biomass?
- these are drawn to show total mass of organisms in each trophic level (i.e. mass of an individual x number of individuals)
- they’re a more accurate way of looking at the relative amounts of organisms.
4.7 what are pyramids of energy transfer?
- these are drawn to show total energy available in each trophic level per square metre per year
- there should be a decrease in energy between each trophic level
4.9 why is only about 10% of energy transferred from one trophic level to the next?
- some parts of organisms not eaten (so the biological molecules not available for respiration)
- some parts not digested & absorbed, they’re egested as faeces (so biological molecules not available for respiration)
- some materials are respired to release energy - the energy is used for: muscle contraction (movement & breathing), maintaining constant body temp (mammals/birds), synthesising biological molecules (including excretory products), movement of molecules (active transport), cell division
what is the least efficient energy transfer from?
light energy to the producer, because:
- some light will miss plant/plants chloroplasts
- some light will be reflected by cuticle
- some light has wrong wavelength to be absorbed by chlorophyll
4.11B describe the stages in the nitrogen cycle
- nitrogen fixing bacteria in soil & roots of legume plants absorb nitrogen and reduce it to make ammonia, this process called nitrogen fixation
- ammonia converted to nitrates & nitrites by nitrifying bacteria, process called nitrification
- plant roots can only absorb the nitrates. they’re combined with carbs (from photosynthesis) to form amino acids which then made into proteins, and nucleotides which are joined to make DNA and RNA
- animals eat plants. they digest the proteins & DNA, absorbing the small soluble molecules (amino acids & nucleotides). these are used by the animal to synthesise (make) new proteins and DNA (assimilation)
- when a plant/animal dies its tissues decomposed by bacteria & fungi (saprotrophic feeding)
- molecules containing nitrogen such as proteins are broken down by bacteria & fungi and ammonia released into soil
- some nitrates converted into N2 by denitrifying bacteria. this process is denitrification
4.11B what is decomposition in the nitrogen cycle, and what bacteria is involved?
- protein in dead plants & animals broken down
- ammonia released into soil
- decomposing bacteria
4.11B what is nitrification and what bacteria is involved?
- ammonia converted to nitrites, and nitrites converted into nitrates
- nitrifying bacteria
4.11B what is denitrification and what bacteria is involved?
- nitrates are converted to nitrogen gas (denitrification reduces amount of nitrate in soil & therefore makes soil less fertile)
- denitrifying bacteria
4.11B what is nitrogen fixation and what bacteria are involved?
- nitrogen gas converted to ammonia in bacteria which is used to make proteins, when bacteria die their proteins decompose, releasing ammonia back into soil
- nitrogen fixing bacteria found in soil and in root nodules of plants
4.11B what is the mutualistic relationship between some nitrogen fixing bacteria and the legume plants?
- the bacteria receive glucose from plant
- plant absorbs ammonia from bacteria in nodule
4.11B why do farmers rotate the crops they grow in each field?
when the nitrogen fixing bacteria in the nodules of the roots of legume plants decompose they make soil much more fertile by releasing ammonia which can be converted into nitrates
4.1B what does the term biodiversity mean?
the variety of living organisms in an ecosystem
4.12 what are the biological consequences of pollution of air by sulphur dioxide & carbon monoxide?
sulphur dioxide:
- combines with water vapour to form acid rain, damaging plants, aquatic life, and soil
- causes respiratory problems in humans
carbon monoxide:
- binds to haemoglobin irreversibly, reducing oxygen transport in blood
- can lead to suffocation & death in high concentrations
4.13 what are examples of greenhouse gases?
water vapour, carbon dioxide, nitrous oxides, methane, and CFCs
4.14 how do human activities contribute to greenhouse gases?
CO2: burning fossil fuels, slash & burn forest clearance
methane: generated by bacteria in anaerobic condition, for example:
- ruminants such as cattle produce large volumes of methane from anaerobic activity of bacteria in their gut, this largely comes out of their mouths
- bacteria in waterlogged paddy fields for rice cultivation give off methane
nitrous oxides: burning fossil fuels
CFCs: until 1990s CFCs used as solvent for aerosols such as deodorants; they were also used in fridges & freezers. CFCs were blamed for the hole in the ozone layer (don’t confuse this w greenhouse effect)
4.15 how does an increase in greenhouse gases result in an enhanced greenhouse effect
- sun emits radiation, which travels through space. some reflected by earths atmosphere, but some passes through & absorbed by earth’s surface. this warms earth, which then emits IR radiation
- some IR radiation passes through atmosphere into space, but some gases in atmosphere absorb it, preventing it from escaping back into space
- this leads to more energy being held by atmosphere, heating it
- gases which cause this effect are water vapour, CO2, methane, nitrous oxides and CFCs
