Estimating total populations - formula
Total number = (number counted x total area)/ area sampled
Estimating population density - formula
Density = Total number counted/Area sampled (no. area-n)
Quadrat sampling
is a method by which organisms in a certain proportion (sample) of the habitat are counted directly.
Calculating Abundance (total number) - formula
Calculating Estimated Average Density - formula
What are the three types of transect sampling?
Point sampling
Continuous belt transect
Interrupted belt transect
Zonation
changes in community composition along an environmental gradient.
Pros/Cons of transect sampling (Recognition)
ī¨ Advantages ī¤Good for showing zonation ī¨ Disadvantages ī¤Low density organisms may not be sampled ī¤Larger organisms have a greater chance of being sampled by a line transect
Capture Recapture method
ī¨ Used for counting organisms that move, or for monitoring populations over time. ī¨ A sample of organisms are captured, marked and released. At a later point in time, another sample is captured, and the number of marked organisms in the second sample is counted and recorded.
Capture recapture cons (Recognitions)
Accuracy depends on capturing a fairly large proportion of the population. ... Many study populations are not geographically closed because only a part of a population's range is included in the study area.
Lincoln index
Total population = (# of marked in 1st sample X total # in 2nd sample)/# of marked in 2nd sample
or
N = (n1 x n2)/n3
Indirect sampling - Advantages and disadvantage (Recognition
ī¨ Trails, droppings, burrows etc ī¨ Camera traps ī¨ Advantages ī¤ Good for individuals that are difficult to physically count ī¤ Doesnât harm organism ī¨ Disadvantages ī¤ You have to know a relatively large amount of background information. E.g. how many individuals per burrow ī¤ Less accurate
Species richness
is a measure of the number of different species found in a sample.
Species evenness
a measure of the relative abundance of the different species making up the richness of an area.
Species diversity
takes into account both the numbers of species present and the dominance or evenness of species in relation to one another.
Diversity Index - Simpson's diversity index - formula
A diversity index is a measure of the number of different organisms in an ecosystem.
DI = (N(N-1))/(ÎŖn(n-1))
DI=Diversity Index N=total number of individuals from all species n=number of individuals of each species
Chi squared analysis - formula
ī¨ X2 = is the Chi value ī¨ â = sum ī¨ o = observed value ī¨ e = expected value
Degrees of freedom - formula
DF = (Column - 1)(Row - 1)
Testing for independence/ Association - method
Determine null hypothesis
Enter observed results in a contingency table
Calculate the expected values ī¤ For each category divide the row total by the grand total and multiply by the column total.
Calculate Chi-value
Calculate the degrees of freedom and look up the chi-value on a probability table, and accept or reject the null hypothesis.
Population
the number of inhabitants in a given place
Community
All populations of different species living in an area
Ecosystem
All of the biotic (living) and abiotic (non-living) factors in an area.
Population distribution + Abundance
ī¤Density - number/area or number/volume ī¤Distribution - location within area ī¤Size/abundance - total number of individuals
Name and describe the 3 types of distribution
[Random distribution] ī¤ The spacing between individuals is irregular. The presence of one individual does not directly affect the location of any other individual. Commonly seen in plants.
[Clumped distribution] ī¤ Individuals are grouped together in certain areas, often around a resource. e.g. a waterhole. ī¤ Also when living in large groups is beneficial.
[Uniform distribution] individuals are evenly and regularly spaced in an area.
Explain what population density tells us about the species
ī¨ Low density - only a few individuals per unit area. Often highly territorial, solitary mammalian species such as tigers. ī¨ High density - individuals are crowded together, many individuals per unit area. Often colonial organisms, such as corals or insects.
Population growth - formula
PG = (births â deaths) + (immigration â emigration) ī¨ Birth rate= births per 1000 per year ī¨ Death rate= deaths per 1000 per year ī¨ Immigration= movement of individuals into the population ī¨ Emigration= movement of individuals out of the population
Population composition
Sex Ratios: Ratio between male and female
Population fertility: Reproductive capacity
Age structure: Number of organisms of different ages
Malthusâs Theory of Population Growth (recognition)
ī¨ Populations increase exponentially, while food production increases arithmetically. ī¨ Hence population growth easily outstrips resource production. ī¨ Thus, populations increase quickly, until competition for resources occur and the carrying capacity is reached.
Exponential growth
J- Shaped curve of population growth
Logistic growth
S - Shaped curve of population growth
Carrying capacity (K)
The carrying capacity is the maximum number of individuals an area can support on a sustained basis given the prevailing resources.
r and K selection
Many organisms fall under two main reproductive strategies, r strategists or K strategists.
r strategists often follow a J-shaped growth curve
K strategists often follow a S-shaped growth curve
Density independent factors
Abiotic factors:
Rainfall
Temperature
Salinity
Terrain
Natural disasters etc
Density dependent factors
Biotic factors: ī¤Food supply ī¤Parasites ī¤Disease ī¤Competition ī¤Predation
Nutrient cycling
a system where energy and matter are transferred between living organisms and non-living parts of the environment.
Role of each in nutrient cycling:
Bacteria
Fungi
Plants
Animals
Bacteria: Act as decomposers and convert nutrients into forms that can be used by plants and animals
Fungi: Saprophytes and decompose nutrients into forms accessible by plants and animals
Plants: Absorb nutrients from the soil to make them available for animals and contribute their decaying matter to solids. Additionally, plants can also consume nutrients via cellular respiration.
Animals: Consume and break down materials from plants, bacteria and fungi and return the nutrients after they die
The carbon cycle
cycling of carbon in an ecosystem
Methanogens
ī¨ Methanogenic bacteria (archaeans) release carbon in the form of methane (CH4). ī¨ This process usually occurs in anaerobic conditions such as swamps and bogs and can cause dead organic matter to not be fully decomposed by saprotrophs. ī¨ It can also occur in the digestive bacteria of ruminant mammals. ī¨ Methane is usually taken up by methane sinks such as soil or can be oxidised to CO2 in the atmosphere
Sink
Storage unit for large quantities of carbon ie the atmosphere/ the ocean
What affects the speed of nutrient cycling?
Environment (ie forest disturbances by rainfall/ weather patterns)
Ecosystem - Competition for resources, community interactions etc
Name the processes that release carbon into the atmosphere
Combustion
Oxidation
Respiration
Decomposition
Name the processes that absorb carbon into sinks
Photosynthesis
Fossilisation
Sedimentation
Dissolving (of CO2 into the ocean)
Describe the biological origin of:
Coal
Oil and natural gas
Limestone
Peat
Due to acidic and anaerobic conditions in some wetlands/swamps, saprotrophs are unable to fully break down organic matter so overtime it forms thick deposits called peat. Layers on top of the peat plus time, pressure and heat and it forms coal. Silt, sediment and organic matter can be deposited in shallow seas but again, the anaerobic conditions can prevent the organic matter from being fully decomposed. The silt converts to rock and organic matter forms coal, oil or gas deposits
Carbon flux
describe the rate of exchange of carbon between the various carbon sinks / reservoirs.
How is carbon stored? (name 4 sinks)
Atmosphere: Atmosphere - Carbon dioxide Hydrosphere: Ocean - Carbonate and bicarbonate Lithosphere: earths crust - Rocks and limestone Biosphere: organisms - methane or hydrocarbons
The nitrogen cycle
Nitrogen fixation
Nitrification
ī¨ Nitrification is the conversion of ammonia to nitrate. ī¨ Two types of soil bacteria are involved: ī¤ Nitrosomonas convert ammonia to nitrite (NO2-) ī¤ Nitrobacter convert nitrite to nitrate (NO3)
Denitrification
ī¨ Denitrification is the conversion of nitrate into nitrogen. ī¨ This process only occurs in the absence of oxygen in the soil by denitrifying bacteria (Pseudomonas).
Ammonification
The nitrogen cycle - processes involved
4 Groups of bacteria involved in the nitrogen cycle and their function
Rhizobium - nitrogen fixation, fix nitrogen (N2) as ammonium (NH4) Nitrosomonas - nitrification, convert ammonium (NH4) to nitrite (NO2-) Nitrobacter - nitrification, convert nitrite (NO2-) to nitrate (NO3-) Pseudomonas - denitrification, convert nitrate (NO3-) back to nitrogen (N2)
Sources of water pollution
sediment
sewage
infectious particles
organic compounds (oil spills)
thermal changes
radioactive pollution
inorganic chemicals
Plastic waste
inorganic plant nutrients
Sources of air pollution
Forest fires, volcanic activity, burning of fossil fuels, industry and vehicles all can produce air pollution. ī¨ In the presence of sunlight, the mixture of pollutants from industry and vehicles reacts to form smog (e.g. ozone, nitric acid, formaldehyde).
Eutrophication
Eutrophication is the enrichment of an ecosystem (typically aquatic) with chemical nutrients (nitrates, phosphates, etc.) The nutrients can be introduced via leaching from soil by rainfall or released as part of sewage
Indicator species - name examples
A species whose presence, absence or abundance reflects a specific environmental condition, habitat or community.
Air pollution:
Clean air: lichen and black spot fungus (roses go brr)
Water pollution: clean water
mussels
mayfly
low pollution - shrimp high pollution - water louse very high - sludge worms and bloodworm
EPT% +
Percent EPT is short for the total number of Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies). Many species within these three groups are sensitive to changes in water quality.
Biomagnification
Biomagnification refers to a pollutants ability to increase in concentration as it moves from one trophic level to the next. It involves an increase in concentration from one link in a food chain to another due to the relative amount each organism in the chain consumes.
Bioaccumulation
Bioaccumulation refers to how pollutants enter a food chain or food web. It involves an increase in concentration of a pollutant from the environment to the tissues of an organism. Smaller, simpler organisms towards the bottom of a food chain will often absorb these pollutants more easily.
Ecological disturbance
Ecosystems change from disturbance ī¤ Land clearing or conversion of ecosystems for urban development, agriculture/farming/plantations, or industry (mining, manufacturing etc) ī¤ Dam creation (for water catchment or electricity generation) ī¤ The introduction of introduced invasive species
HIPPO
H - Habitat loss
I - Invasive species
P - Pollution
P - Population
O - Overuse
Alien / invasive species
An alien species is an organism introduced either intentionally or accidentally by humans to an area where it does not usually occur.
Endemic species
An endemic species naturally occurs in a particular habitat or ecosystem.
Island geography and Nature Reserves - How do we minimise damage to an ecosystem?
Large habitats are better ī¤ More resources, niches, nesting sites etc ī¤ Some migration can occur ī¤ Greater biodiversity
Corridor effect ī¤ Joining regions allows for more migration, foraging, dispersal etc
Edge effect ī¤ Boundaries are not âwallsâ and there is habitat disturbance that extends into the area, particularly in forests. ī¤ If the forest is more fragmented and has more edges, more of the area will be disturbed.
In situ conservation
In situ conservation involve the species remaining in their natural habitat. Often active management is still necessary such as: ī¤ Control of alien/invasive species ī¤ Reintroduction of natives species ī¤ Limiting predators ī¤ Feeding programs ī¤ Limiting access
Ex situ conservation
Ex situ conservation involve the removal of species from their natural habitat. ī¨ This can include botanic gardens, captive breeding programs and zoos.
Greenhouse gas
Gases which contribute to the greenhouse
Water vapour
CO2
Methane
Fluorinated gases
Nitrous Oxides NO2
Greenhouse effect
The greenhouse effect is the way in which heat is trapped close to Earth's surface by âgreenhouse gases.â
Albedo
Why would you use a biotic index regarding pollution?
To compare the relative frequency of indicator species and provide an overall environmental assessment of an ecosystem.