6.5 Flashcards
what is an ecosystem
any group of living and non-living things and the interrelationships between them, thye can be on large scale (african grassland), medium scale (playing field) or smaller scale (rock pool or laqrge tree)
what are 3 components to an ecosystem
habitat, population, community
what is a habitat
place where organism lives
what is population
all of the organisms of 1 species, who live in the same place at same time and who can breed together
what is community
all the populations of different species, who live in same place at same time, and who can interact w each other
what is a niche in terms of ecosystems
the role if each species in an ecosystem
Why is it hard to define niches specifically
esch organism interacts with both living and non-living things
what may a description of a niche include
how and what it feeds on, what it excretes, how it reproduces
can 2 species occupy the exact same niche in the same ecosystyem
no, 1 would out compete the other
what are biotic factors effecting ecosystems
producers, consumers, decomposers
what are producers
plants (and some photosynthetic bacteria) which supply chemical energy to all other organisms
what are consumers
primary consumers are herbivores which feed on plants, these can be eaten by carnivorous secondary consumers which can be eaten by carnivourous tertiary consumers
what are decomposers
decomposers (bacteria, fungi and some animals) feed on waste material or dead organisms
how do biotic facotrs effect an ecosystem
as these components of ecosystem require their own source of materials and energy they can effect other organisms’ food supply, they can also be responsible for predation asnd disease
what are abitotic factors in ecosystems + examples
effects of non-living components on an ecosystem: pH, relative humidity, temperature and polluatnt concentration
How do abitoic facotrs vary
they can vary in space and time
give an example of how abiotic facotrs can be effected by biotic factors
in rainforest, forest canopy infulences temp and hunidity of ecosystenm
What would a graph looking into the intensity of abotic facotrs and species peformance look like
bell shaped curve, at extreme values species may perform better, worse or even die, but every species for every abiotic factor has an optimum level and extremes on both ends can be lethal
what is an example of an abitoic factor only being lethal at 1 extreme and what would a graph for this look like
pollutant concentration only lethal at extreme high, extreme low will not effect species, so graph would be a straight line and then a rapid decline when concentration too high
why are ecosystems refered to as dynamic
as they change, non-living elements change and living elements grow and die, with populations of certain species rising and falling
why are ecosystems dynamic either very slightly or very noticeably
as living things in an ecosystem interact with each other and their physical environment, an small change in 1 can effect the other
what is an example of how ecosystems are dynamic
id predtor population size goes up, prey population will decrease as more eaten more quickly
what are the 3 changes to ecosystems that affect population size
cyclic changes, directional changes, erratic changes
what is a cyclic change
these changes repeat themselves in a rhythm, e.g. movement of tides. Way in which predator and prey species flucuate is cyclic
what is a directional change
non cyclic, go in 1 direction and tend to last longer than the organsisms within the ecosystem. Within this change, particular variables continue to increase or decrease. e.g. errosion of coastline
what is a erratic change
have no rhythm and no constant direction. e.g. effects of lightening or huurricanes
what is an example of how living things respond to changes in ecosystem
small mammals hibernate rhythmically to avoid cold temps in winter
what is constantly being recycled in ecosystems, give examples and what is not recycled
materials, e.g. nutrient cycles like nitrogen and carbon cycle, energy is not recycled but flows through the ecosystem
All living things need energy and materials, what do plants use it for
energy is captured by plants in photosynthesis to produce organic molecules like glucose from water and carbon dioxide, this energy is release from glucose during respiration, products of photosynthesis are used immediately for respiration and are also incorporated into tissues and organs (cellulose for cell walls). Mineral ions are absorbed through plants roots
what is a plants biomass made up of
organic components like glucose molecules and inorganic components like mineral ions (not water).
what happens when a plant is eaten by primary consumer
its biomass is consumed and when secondary consumer eats primiary consumer it will consume its biomass and so on
what is a trophic level
each level of the food chain
What does tracking how biomass changes in a food chain help
us to track movement of materials and energy through food chain, we do that for one food chain or whole food web in an ecosystem
whar happens to biomass at each new trophic level
some biomass is lost from food chain and therefire unavailable to organism at next trophic level
How is some biomass lost at each tropic level (1)
living organisms need energy to carry out life processes, respiration releases energy from organic molecules like glucose. Some of this energy is eventually converted to heat and materials are lost in carbon dioxide and water
How is some biomass lost at each tropic level (2)
biomass also lost from a food chain in dead organisms and waste materials which is then only avaliable to decomposers like fungi and bacteria, this waste material also includes parts of animals and plants that can’t be digested by consumers like bones and hair
what does the loss of biomass mean as trophic levels increase
biomass is less at higher level of food chain, when organisms in food chain are about same size, means there will be fewer consumers at higher levels
what did ecologists draw to show the loss of biomass higher up food chain
a pyramid of numbers, area of each bar in pyramid is proportional to number of individuals, as an aproximation for total biomass at that level, pyrimids can be drawn for individual food chains or whole ecosyste
does pyramid of numbers always work
no, counting number of organisms doesn’t always provide an accurate picture of how much biomass exists at each level
what is better than a pyramid of numbers
pyramid of biomass, where area of each bar is proportional to dry mass of all organisms at that trophic level
how is pyramid of biomass calculated
collect all organisms and puts them in oven at 80degreesC until all water in them has been evaporated, check this by periodically finding mass of the organisms. Once mass stops reducing they can be certain all water removed.
what is an issue with calculating biomass by removing water from all organisms
it is very destrucitve to an ecossytem
what is a less destructive way of calculating biomass
calculate wet mass and then calcuklate dry mass from this based on reviously published data
how do you calculate efficiency of biomass transfer between trophic levels
ecological efficiency=(biomass at higher trophic level/biomass at lower tropic level) x 100
what is a measure of somethings productivity
the rate at which energy passes through each trophic level in food chain
what is gross primary productivity
rate at which plants convert light energy into chemical energy by photosynthesis, even at start of food chain this is inefficient.
why is gross primary productivity inefficient even at start of food chain
as photosynthesis produces glucose, entry of biomass into food chain is also inefficient, in optimal conditions only 40% of light energy from sun enters light reaction of photosynthesis and only half of this involved in glucose production, only 2/3 of this glucose is then used for production of starch, cellulose, lipids and proteins, contributing to growth, rest is respired, so only a small portion of energy from the sun remains in the food chain
what is net primary productivity
amount of energy from sun that remians in the food chain
how can humans increase amount of biomass incorporated into plants
manipulating environmental factors, humans make energy conservation more efficient, reduce energy loss and increase amount of biomass incorporated into plants
what is 1 limiting facotr of photosynthesis and what does this mean for production of biomass
light levels limit rate pf photosynthesis which also limits production of biomass, some crops planted early to provide longer growing season to harvest more light and others grown under light banks
how does creating drought resistant plants increase primary productivity
water is reactant in photosynthesis when glucose is produced so drought resistant crops have been bred in North Africa
how does growing plants in greenhouse improve primary productivity
provides warmer temperature, increases rate of photosynthesis and increases rate of production of biomass, planting field crops early to provide a longer growing season helps avoid impact of temp on final yeild too
how have humans overcome lack of avaliabkle nutrients which slows ratre of production of biomass through photosyntheis
crop rotation helps, grow different crop on each field on rotational cycle stops soild reduction of inorganic ions like nitrate
how have humans overcome pest like insect removing biomass from food chain and lowering yield
spraying pesticides or bred plants to be pest resistant
how have humans overcome fungual disease in plants which reduces biomass
fungal infections casn cause damage to roots, xylem, phloem, flowers and fruit. farmers can spray fungiicides or genetically modified or bred to be reisstant to some fugal infections
how have humans overcome competition from weeds for light, water and nutrients which decrease NPP
use herbiicdes to kill weeds
how is secondary producticity inefficient without human manipulation
transfer of biomass between trophic levels is insufficient, primary consumers dont make full use of plants biomass (not every part of plant eaten but it dies), and when food is digested and absorped much is respired with only small amount leading to increased biomass and being avaliable to next consumer in food chain
what are ways humans can manipulate energy transfer (secondary productivity (1 and 2/4)
young animals invests a larger proportion of its energy into growht than an adult, harvesting animals just before adulthood minimises loss of enrgy from food chain, 2. selective breeding used to produce improved animaln breeds with faster growth rates, increased egg and milk production
what are ways humans can manipulate energy transfer (secondary productivity (3 and 4/4)
animals may be treated with antibiotics to avoid unnecessary loss of energy to oathogens and parasites 4. mammals and birds waste energy by grazing, zero grazing reduces this by directly feeding cattle maximal energy allocated to mulch by stopping animals moving and this also maintains a constant temp
what are welfare issues with modern farming practices
animals welfare, fine balance between need for efficient food prodution and modern farming breaching animals welfare
what are decomposers
things that break down dead and waste organic materials, e.g baceria and fungi are decomposers
why are decomposers decribed as saprotrophs
the feed saprotrophically, off other materials
what are the 3 steps in saprotrophic decomposition
- saprotrophs screte enzymes onto dead and waste material 2. enzymes digest material into small molecules which are then absorbed into saprotrophs body 3. having been absorbed, molecules are stored or respired to release energy
what would happen if bacteria and fungi didn’t break down dead organisms
energy and valuable nutrients would remian trapped within dead organisms, by digesting dead and waste material, microorganisms obtain supply of energy to stay alive and tapped nutrients are recycled
what do living things need nitrogen for
making proteins and nucleic acids
what is baceria involved in in recycling nitrogen
ammonification, nitorgen fixation, nitrification, denitrification
can plants use nitrogen gas directly
no, even though it is so abundant it is unreactive, instead plants need fixed nitrogen like ammonium ions or nitrate ions
how is some nitrogen fixed
when lightening strikes or in haber process of making fertiliser
how is most nitrogen fixed
nitrogen fixing bacteria
how does nitrogen-fixing bacteria work
azotobacter live freely in soil adn fix nitrogen gas which is in air within the soil, using it tp make amino acids. nitorgen fixing bacteria have a mutualisitc relationship woth plamnt (bacteria provides plant with fixed nitrogen adn recieves carbon compounds like glucose in return
how are ammonium ions released
through ammonification by bacteria involved in putrefactionof proteins found in dead and waste organic matter, rather than gettin their energy from sunlight, some chemoautotrophic bacteria in soil obtain it by oxidising ammounium ions to nitrates whilst others obtain it by oxidising nitries to nitrates, called nitrification
what does it mean for ammonification and nitrification thatoxidation requires oxygen
these reactions only happen in well-aerated soils, nitrates can be absorbed from soil by plants and used to make nucleotide bases and amino acids
what is dentrification
other bacteria convert nitrates back to nitrogen gas, when bacteria involved are growing inder anaerobic conditions like in waterlogged soils, they use nitrates as a source of oxygen for their respiration and produce nitrogen gas and nitrous oxide
how is carbon similar to nitrogen
they are both cycled through biotic and abiotic components of an ecosystem
what is carbon cycle driven by
processes of respiration and photosynthesis, with carbon dioxide being main vehicle for cycling carbon between biotic and abiotic components of the cycle. animals, plants and microorganisms respire to release carbon dioxide, microorganisms esp important in decomposition of dead organisms and waste
what is the difference in terrestrial plants and aquatic plants use of carbon
t=use gaseous carbon dioxide in photosynthesis a=used dissolved carbonates
how does the carbon cycke work
carbon is exchanged between air and water when carbon dioxide dissolves in water and then reacts to form carbonic acid, carbon also enters rivers and lakes from weathering of limestone and chalk in form of hydrogen carbonate. Combustion of fossil fuels has increased across last century, so balance of carbon cycle has changed and atmospheric carbon dioxide levels are higher, this change is responsible for global warming.
what is succession
any change in community of organisms can change their habitat and this can change make-up of community. A gradual directional change in a community overtime is succession
What is island of Surtsey in Iceland formed from volcanic eruption an example of
primary succession, had bare ground and now home to a community of plants
what are 3 stages to primary succession
- algae and lichens begin to live on bare rock (pioneer community), 2. erosion of rock and a build-up of dead and rotting organic material produce enough soil for larger plants like mosses and ferns to grow which replace or succeed algae and lichens 3. larger plants succeed these small plants until a final, stable community is reached (climax community), e.g. woodland community
what is secondary succession
takes place on previously colonised but disturbed or damaged habitat (not always starting from bare ground)
how do sand dunes show all the stages of succession
sea deposits sand on beach, sand nearest sea is deposited more recently than further away meaning sand just above high water mark is at start of process of succession whereas sand much further away already hosts its climax community
what is stage 1 of succession in sand dunes
pioneer species like sea rocket colonise the sand just above high water mark, these can tolerate being sprayed with salty water, lack of fresh water and unstable sand
what is stage 2 of succession in sand dunes
wind-blown sand builds up around the base of these plants, forming a mini sand dune, as plants die and decay, nutrients accumulate in this mini dune, as dune gets bigger, plants like sea sandwort and sea couch grass colonise it. As sea couch grass had underground stems it stabalises the sand
what is stage 3 of succession in sand dunes
with more stability and accumulation of more nutrients, plants like sea spurge and marram grass strat to grow, Marram grass is special: its shoots trap wind-blown sand and the sand accumulates the shoots grow taller to stay above the growing dune, trapping more sand in the process
what is stage 4 of succession in sand dunes
as sand dune and nutrients build up, other plants colonise the sand. Many are leguminous, like hare’s foot clover and bird’s foot trefoil which convert nitrogen to nitrate. With nitrate available, more species colonise the dunes, like sand fescue and viper’s bugloss, which stablisies them further
why is it difficult to work out if some climates have reached climax community
landscapes can be heavily influenced by agriculture, esp in UK
what is deflective succession
when succession is stropped or interfered with, the sub-climax community as a result is called a plagioclimax
what is selected succession example
cutting grass on a golf course keeps land at one stage in succession, if grass wasn’t cut for many years, succession would continue and climax community could be reached (e.g. a woodland)
what are ways succession can be deflected
grazing, burning, fertiliser, herbicides, exposure to excessive wind or human activity
what is sampling
selecting a few samples from a habitat and studying them carefully to get a general idea of the whole habitat
what is the 2 types of data you can collect using a quadratic
presence/absence of species (distribution), number of individuals (abundance) of each species - either estimated (%cover) or counted
how is estimating made more accurate when using quadrat
by using a point frame
what are the 2 most unbiased ways to sample a habitat
randomly position quadrats using random number generator and coordinates of the habitat or take samples at regular distance across habitat (systematic sampling)
how do you know how many quadrates to sample
do pilot study, take random sample from across habitat, making a cumulative frequency table, plot cumulative frequency against quadrant number, the point where curve levels off tells you how many quadrats to use
equation for population size of a species after sampling
mean number of individuals of species in each quadrat/fraction of total habitat area covered by a single quadrat
what are the 2 approaches to using a transect
line transect- at regular intervals make not of what species touch the tape, belt transect- at regular intervals place quadrant next to the line (interrupted belt transect) or place quadrant next to line moving along line after looking at each quadrant (continuous belt transect)
how would you plot data from transects
on a kite diagram
