topic 10 Flashcards
10.1 [the nature of ecosystems]
- What’s an ecosystem?
- Population?
- Community?
- Niche?
- Ecosystem: An environment including all the living + non-living factors with which they interact. can be many sizes (eg as small as a rock pool / very large)
- Population: Group of organisms of the same species that breed together in the same habitat
- Community: A group of populations of different species interacting in the same habitat
- Niche: The role of an organism in its community
Biotic v Abiotic factors
Biosphere?
Biomes?
- Biotic - living elements of a habitat that affect ability of organisms to live there (availability of prey, bacteria)
- Abiotic - non-living elements of a habitat (sunlight, temp, soil pH, rainfall, O2 in water)
- Biosphere - all the areas of the surface of the earth where living organisms survive
- Biome - the major ecosystems of the world
Trophic levels?
Different ways it can be represented?
Trophic levels
- describe the position of an organism in a food chain or web
- +describes its feeding relationship with other organisms
Can be represented by
- pyramids of numbers
- biomass (dry)
- energy
Different trophic levels within a food web
- Producers - make food (plant + algae photosynthesise using sunlight to make food)
- Primary consumers - organisms which eat the producers (herbivores)
- Secondary consumers - animals that feed on herbivores (carnivores)
-
Tertiary consumers - animals that feed on other carnivores
(top predators, unless there’s a quarternary consumer) -
Decomposers - the final trophic level in any feeding relationship which digest dead organic material
(miroorganisms [bacteria/fungi] that break down remains of animals + plants + return nutrients to soil)
+ / - of
pyramids of numbers
(counting)
as representation of ecosystem structure+ how biomass+energy transferred
ADV +
- easiest to measure
DISADV -
- least accurate
+ / - of
biomass
(weighing)
as representation of ecosystem structure+ how biomass+energy transferred
ADV +
- More accurate
DISADV -
- Don’t take into account rate of production of biomass
- using dry mass = dehydration kills organisms
- = use wet mass = less accurate
+ / - of
energy levels
as representation of ecosystem structure+ how biomass+energy transferred
ADV +
- Most accurate
DISADV -
- Hardest to measure
- = rarely used in practice
Abundance?
Distribution?
Ecological techniques of measuring them?
Abundance
- the relative representation of a species in a particular ecosystem
- total number of individuals of a species present in a ecosystem relative to other organisms in same habitat
Distribution
- Where species of organisms are found in the enviornment + how its arranged
- how spread out the organisms are from eachother
Ecological techniques
- Quadrat
- Transect
- ACFOR scales
- Percentage cover
- Individual counts
Unifrom V clumped V random
distribution
Uniform distribution
- resources thinly but evenly spread
Clumped distribution
- Distributed in groups (eg herds of animals)
- groups of animals + plants which have specifc resource requirment = clump in areas where they’re found
Random distribution
- A result of plentiful resources + no antagonism
- ( eg dandelions in field)
Quadrats
- individual counts
- percentage count
- square gridded frames placed at random
- count the number of individual organisms inside (individual counts)
- using divided grid, find area covered by the organism (percentage cover)
- multiple readings = find mean
- Issue about decisions on whether to include organisms partly covered by quadrat
- = need to decide before u start if organisms on sides are in / out
- point quadrat - wooden frame quadrat with holes in it placed and metal pins placed in each hole and count number of organisms which touch each pin
ACFOR scale
- use ACFOR scale to measure abundance of organisms in a quadrat / area
- used to describe abundancy in area as…
A = abundant
C = common
F = frequent
O = occasional
R = rare
ISSUE
- it’s subjective. 2 ppl will not come up with same rating
- No set definition of terms = hom much is ‘common’
Transects
-systemetic sampling method
- line / belt transect which runs across area to be investigated sytemetically
- stretch line transect between 2 points + record the number of each individual plant/animal that touch the tape
- Belt transect = 2 tapes laid out + area between them surveyed using quadrats along a line
- Interrupted belt transect - sample at regular intervals rather than recording a whole belt
Other measures of abundance that can be used
- light traps to attract flying insects
- capture / recapture techniques for animals that move around
- beating of branches to collect what falls out
Making comparisons
Aspects of sampling techniques which can be compared..
- transects + random sampling
- belt + interrupted transects
- different quadrat sizes
- types of quadrat
- individual count + percentage cover
statistical tests to analyse data
Statistical tests can indicate if differences in results (from sampling methods) are significant
- observer value on table of critical values?
- null hypothesis?
- observer value on table of critical values = need to look up OV for each test to see which probability value this corresponds with to see if u should accept null hypthesis or not
- significant = less than 0.05
- = corresponds to the p < 0.05 level of significance
- null hypothesis = hypothesis that any differences between data sets are simply due to chance
Statistical test 1
Spearman’s rank correlation coefficient
- Why use it?
- To measure correlation between two variables
- (the extent to which changing one variable affects the other variable)
Spearman’s rank correlation coefficient
- How to do it?
- State null hypothesis
- Give rank to each item in each set of measurements
- Find the differences (D) between ranks for each pair of measurements
- Add all the differences (squared individually) together + use formula to find correlation coefficient (r)
Explain how Spearman’s rank results are interpreted
Find correlation coefficient r between -1 to 1
= size of coefficient indicates how strong correlation is
- Closer to 1= more positive correlation
- Closer to -1= more negative correlation
- Around 0 = no correlation
Deciding whether to accepy null hypothesis or not
- State the null hypothesis (variables do not correlate)
- Calculate ‘r’ coefficient
- Decide whether to accept / reject null hypothesis (by comparing it to 0.05 critical value)
- If more than the critical value at 0.05 = significant = reject null hypothesis = less than 5% due to chance
- If less than 0.05 = not significant
Statistical test 2
Student’s t-test
- why use it?
- to test to see if there’s a significant difference between the means (averages) of two sets of data
Student’s t-test
- how to do it?
- State null hypothesis
- Calculate observer value (t) using formula
- use a table to see if t is above or below p = 0.05
for (n1 + n2) - 2 degrees of freedom
decide whether to accept null hypothesis
explain how t-test results are interpreted
- the t value obtained is compared to a critical value (found in a table) for a particular p value chosen by the researcher
- Find degrees of freedom (total number of data - 2)
- find probability (p) value that relates to observer value + degree of freedom
- if p > 0.05 = difference is significant
- T value should be higher than the critical value at 0.05 to be significant = reject null hypothesis
10.2 [energy transfer through ecosystem]
energy transfer
- Gross primary productivity?
- Net primary productivity?
- Energy is transferred between trophic levels in an ecosystem
Gross primary productivity (GPP)
- The rate at which producers make organic material / biomass through photosynthesis [using light]
- units eg: g m2 year1 (grams of biomass pr area yearly)
- plants use atleast 25% of material they produce for own metabolic needs + respiration
- rest of material is stored as NPP
Net primary productivity (NPP)
- The material produced by photosynthesis stored as new plant body tissues
- NPP of different ecosystems depends on abiotic + biotic factors which affect plant growth
- biomass/energy in producers which transfers to the primary consumers
NPP = GPP - R (respiration)
How is energy transferred between trophic levels?
- source of energy for all living systems is light from sun = light intensity is limiting factor for ecosystems
- Only a small amount of the energy available to an organism is transferred to the next trophic level
- Some is never taken in, some is lost before being transferred
Why is some energy never taken in at each trophic level?
● Some parts of food are not eaten
● Some parts of food are indigestible
● Plants can’t use all light energy as some is in the wrong wavelength
Energy losses along a food chain
- some energy lost as undigested + therefore unused material in the faeces
- much of material is used to drive respiration = exothermic so energy lost to surrounding
- = heat loss + energy used for movement
- some of plant material is lost in metabolic waste products such as urea
=
- only a small amount of chemical store of plant becomes new animal material + therefore part of the energy store of animal
- the rest is dissipated to the surrounidings = increasing internal energy store of universe
- process of making new animal biomass is known as secondary production
Measure of the effeciency of energy transfer
- similiar energy transfer occurs between animal trophic levels from herbivore to primary to secondary consumers etc up the food chain
- energy store in biomass of 1 organism compared with energy store that ends up in organism in next trophic level is measure of effeciency of energy transfer
- effeciency of energy transfer is the proportion of energy in 1 trophic level that is available to the next
- effeciency of energy transfer is around 10% at each level in food chains
- but its’s difficult to measure energy transfers
Nutrient recycling
- the nutrients needed by organisms to build new body cells are returned to the enviornment as waste or by decomposition
- microorganisms are important in the recycling of nutrients within an ecosystem
- plants need inorganic nutrients (CO2/ nitrates) to produce organic molecules
- transferred between biotic + abiotic factors in nutrient cycle
- plants take CO2 from air to use in photosynthesis to produce carbohydrates
- plants take nitrates from soil water to produce amino acids + proteins + nucleotides used to build DNA + RNA
why can’t plants use nitrogen in air?
- plants cannot use nitrogen in air as its an inert gas = unreactive
- only nitrogen in form of nitrates useful for plants from soil water
- = taken up to make protein = protein passed along food chain
decay of nitrogen
- nitrates taken up from soil water by plants
- used to make proteins = passed down food chains
- nitrogen passed out through faeces / urea back into soil / when they die = body contains lots of protein
- decomposers break proteins to form ammonium compounds
- amounium compounds then oxidised by nitrifying bacteria = convert them to nitrates = reabsorbed by plants
Nitrogen cycle
- Nitrogen Fixation
- Ammonification
- Nitrification
- Denitrification
1. Nitrogen Fixation
- nitrogen-fixing bacteria in soil convert nitrogen compounds (from animal waste /dead organic matter) into ammonia
- [ Legumes (plants - peas,beans) have nodules in roots with nitrogen-fixing bacteria - Mutualism = bacteria provide the plant with nitrogen compounds + plant provides the bacteria with carbohydrates ]
2. Ammonification
- Saprobionts decompose nitrogenous waste into ammonium compounds
3. Nitrification
- ammonia oxidised by nitrifying bacteria - converted to nitrates + nitrites
4. Denitrification
- Denitrrifying bacteria break down nitrates (to power production of ATP)
- producing nitrogen gas as waste product = making nitrogen unavailable for plants = not useful bacteria
Bacteria in nitrogen cycle
- Nitrogen-fixing bacteria?
- Nitrifying bacteria?
- Denitrifying bacteria?
- Nitrogen-fixing bacteria
- converts nitrogen frm soil into ammonia
- Nitrifying bacteria
- oxidise ammonium compounds to form nitrites + nitrates
- Denitrifying bacteria
- breaks down nitrates to power production of ATP, producng nitrogen gas as waste product
Carbon cycle
- CO2 removed from air by photosynthesis of green plants
- used to make carbohydrates, proteins, fats = make up body of plant = passed through food chain as plants are eaten
- green plants + animals respire = CO2 released back into environment/air/atmosphere
- when plants + animals die = their body (which contains carbon) broken down by decomposers = release carbon into atmosphere as CO2 = cycle repeats
- Combustion - burning of wood.fossil fuels etc - release CO2
Carbon sinks
- a reservoir where carbon is removed from atmosphere + ‘locked up’ in organic / inorganic compounds
- removed from atmosphere through photosynthesis + stored in bodies of plants + animals
- rocks, fossil fuels, chalk - hold carbon
- oceans - massive reservoirs of CO2 - contain ALOT of dissolved inorganic carbon
Human influence of balance of Carbon cycle?
humans use of
- cars, burning of fossil fuels etc releasing alot more CO2 into atmosphere than before
10.3 [changes in ecosystems]
Organisms cause changes to their enviornment = ecosystems develop overtime
Succession?
- The process by which the communities of organisms colonising an area change over time = replaced by more varied + productive communities
Primary succession?
- Starts with an empty inorganic surface, such as bare rock / sand dune
- Occurs when an area previously devoid of life is colonised by communies of organisms
- eg after eruption of a volcano = led to the formation of a rock surface, then algae,mosses,fungi
- = these organisms penterate rock surface + break it
- = these inorganic rock grains start formation of soil
- = soil allows other species (grass/ferns) to establush root systems
Summarise the process of primary succession
● Colonisation - species grow that are capable of survivng difficult conditions of bare rock
● Pioneer species able to survive harsh conditions, colonise the area after colonisers made conditions bit better
● They die, decompose + add nutrients to the ground (add humus = organic component of soil)
● add niches/food/habitat for other organisms = tress grow
● Over time, this allows more complex organisms to survive
● = climax community can form when largest plants are able to grow + there’s no further succession
Climax communities?
2 types?
- The final stage of succession, where the ecosystem is balanced + stable
- It is reached when the soil is rich enough to support large trees / shrubs + the environment is no longer changing
- Climatic climax communities - Initially thought that a given climate could support only one climax community - idea has been discredited
- A Plagioclimax - a stable community where there is human intervention such as grazing, atleast a part is aresult of human intervention
Secondary succession
- development of ecosystem from existing soil that’s clear of vegetation
- occurs after fires + floods / disturbances by humans
- The re-colonisation of a habitat after a disturbance
- similiar to stages of primary succession except soil is already developed
Biotic = living factors
biotic factors which affect population size
- Predator-prey relationships
- availability of reproductive partners
- territory
- Parasites + microorganisms
- Competition - intra v interspecific
Biotic factors
- Predator-prey relationships
- availability of reproductive partners
1. Predator-prey relationships
- Important for both populations
- pop size of prey species affected by amount of predation
- pop size of predators affected by prey availability
- predator + prey populations oscillate as their numbers affect eachother
2. availability of reproductive partners
- Availability of finding reproductive partners can increase/decrease population
- Lack of species in an area = cannot find a mate to reproduce = population falls
- Territory
- Parasites + microorganisms
3. territory
- area held + defended by an animal (or group) from predators
- necessary so breeding pairs have sufficient resources to raise young
- can affect abundancy of organisms in habitat = the territory must be big enough to provide resources for a breeding group
4. Parasites + microorganisms
- parasites + microorganisms that cause disease can affect population sizes
- diseased animals = weak + cannot reproduce successfully
- cannot hunt + more likely to get killed
- parasites feed off living bodies of host + weakening it = can wipe out whole population
- Intraspecific v Interspecific competition
Intraspecific competetion
- competetion between members of same species for a limited resource
- = some individuals may not survive / may not reproduce = population growth slows
Interspecific competetion
- Competetion between different species within a community for the same resource
- will reduce the abundance of the competing species that’s missing out on resource
Abiotic factors = non-living
Abiotic factors which affect population size
- light intensity
- wind + water currents
- temperature
- water availability
- oxygen availability
- Edaphic factors (composition of soil - eg pH)
- light intensity
- wind + water currents
1. light intensity
- Affects plant structure + growth (photosynthesis)
- Indirectly affects consumers = availability of food
- Affect reproductive patterns
- Affect circadian rhythms = controls animald physiology + behaviour
2. wind + water currents
- Affects stability of enviornment
- Wind affects water loss from body+ cooling
- Hurricanes destroy habitats
- water current= organisms have to flow with current, attach to surfaces, or be strong swimmers to survive
- temperature
- water availability
3. temperature
- Affects enzyme controlled reactions
- Most organisms have a limited range in which they can reproduce successfully
- Adaptations enabeling them to cope woth specific temp = those wothout adaptations = cannot survive
4. water availability
- Very low water availabilty (water stress) = organisms will die unless adapted (eg camels)
- Can cause severe change in habitat
- affects photosynthesis
- oxygen availability
- Edaphic factors
(composition of soil - eg pH)
5. oxygen availability
- can be in short supply in water + soil
- if water cold = O2 dissolves in it = support life
- if water temp rises = less O2 dissolves in it = affect ssurvival of populations in it
- O2 in soil for respiration of plant roots
- if derived of O2 (waterlogged) = plant die
6. Edaphic factors
- relates to structure of soil - pH
- Sandy soil = leaches minerals as water passes through quickly + drains quickly
- Clay = gets waterlogged as difficult to drain + take too long to warm + hard to work
- Ideal soil is loam which is a mixture of types
Density dependent factors
Density independent factors
Population size can also be influenced by
density dependent factors:
- predation, parasitism, food source, space and competition
Density independent factors:
- climate, weather and natural disasters
10.4 [human effects on ecosystems]
How have humans influenced ecosystems?
● Increased carbon dioxide and other pollutants causing climate change
● Depleted biological resources (overfishing)
● Destruction of habitats for buildings, farmland, resources
climate change
Global warming?
- global temperatures are increasing
- will lead to permanent change in earth’s climate
- = sea levels are rising, sea ice is melting, extreme weather conditions more common
Evidence for climate change:
- Records of CO2 levels
= increasing levels of CO2 in the atmosphere contribute towards climate change as CO2 is a greenhouse gas + involved in greenhouse effect
- Temperature records
= enable analysis of changes in temperature
= upwards trend in world temp over years
- Pollen in peat bogs
= Peat blogs preserve pollen to show how vegetation has changed + what kind of plants were present + compare their CO2 + O2 info/requirments
- Dendrochronology
= the study of tree rings as the size of tree rings is affected by temperature
- Ice cores
= reveal perserved of historical CO2 levels trapped in ice
Greenhouse effect?
- process by which gases in Earth’s atmosphere absorb + re-radiate the infrared radiation from the sun, which has been reflected from earth’s surface
- = maintaining temperature at surface of earth which is warm enough for life to exist
- Enhanced greenhouse effect occurs when there’s too many greenhouse gases (CO2, methane, water vapours) = trap too much infrared radiation = temp rises too much
models of future climate change
- data of Co2 + temperature changes can be extrapolated to make predictions
- which can then be used in models of future climate change
- limitation: do not include factors such as reduction in emission of greenhouse gases
- correlation or causation?
Impacts of climate change
- changing rainfall paterns + seasonal cycles
- Changes in distribuon of species – species would move to cooler areas = could potentially lead to the extinction of some species due to competition
- increased risk of flooding from more ice melting = increased sea levels = can destroy habitats
- temp has effect on enzyme activity = affects whole organism
- development of embryos of some reptiles sensitive to temp = temp determines the sex of the crocodile = high temp = more females developing only
depletion of biological resources
- over fishing= fish stock in ocean becoming most depleted biological resource = unsustainable fishing
- too many fished = dont have time to reproduce + replenish population = extinction of some fish species
- Farming = remove crop before plant die + decompose = break nutrient cylce = soil mineral conc falls
- Artificial fertilisers replace lost minerals in soil = soil structure overtime can become infertile even if fertilisers used
Methods of conserving / protecting resources
issue?
- use wide-mesh nets to release young fish
- avoiding fishing during breeding seasons
- imposing fishing quotas (limits)
- encouraging methods that avoid damaging habitat
- Increasing awarness about issues + ways to be more sustainable (provide decent living standards now without compromising need of future generations or ecosystems around us)
- Conflict between needs of humans / growing population / making profit + exploitation of environment
How to reduce CO2 levels in the atmosphere to reduce climate change?
● Growing plants to use as a fuel as biofuels which are carbon neutral
- CO2 released by burning the fuel is removed from atmosphere by the plants its made from (by photosynthesis)
● Reforestation to increase the rate at which carbon dioxide is removed
Endangered + extinction?
Human causes of extinction?
Endangered - species facing high risk of becoming extinct
Extinction - permanent loss of all members of a species
Human causes of extinction
- destroying habitats (deforestation)
- pollution of seas, rivers, lakes with sewage + chemicals
Conservation?
Preservation?
Why have international agreements been introduced?
- Conservation = maintain or increase the biodiversity within a particular habitat by allowing sustainable use of natural resources
- preservation = maintain the biodiversity levels + the habitat intact by minimising the effects of human activities on the particular habitat
International agreements to promote..
- conservaton
- sustainable use of resources
- avoidance of extinction of species
international treaties to support conservation + sustainability
[ CITES ]
Convention on International Trade in Endangered Species of Wild Fauna and Flora
Role of CITES?
- protect endangered animals + plants by regulating trade in living organisms + products made by them
- limits movements of them (imports + exports)
- eg elephant tusks / entire groups of organisms (dolphins)
Success of CITES in conserving biodiversity + preventing extinction?
- banned international ivory trade = poaching levels fallen = elephant numbers increased in areas
- bans on trade of any turtle products (meat / shells) = many turtle species brought back from brink of extinction
Limitations of CITES
- deals with trade only = doesn’t protect ecosystems / protect breeding areas / threatened habitats
- many countries not signed up to CITES
- there are no legal sanctions
- market is still high in demand for these products
human needs V protection of enviornment
How is evidence related to the climate change debate validated + evaluated?
- peer- reviewed - Papers sent to other experts to check for validity = if data + conclusion seem reasonable = results are published in scientific journals
- publication in scientific journals
- debated at scientific conferences
= avoids bias + misleading conclusions
