6.3.1 Ecosystems Flashcards
Define ecosystem
all the living organisms found in an area and the non-living aspects of their environment
Define community
all the populations of living organisms in a particular habitat
Define population
a group of organims of the same species that live in the same place at the same time
Define habitat
the natural home or environment of an animal,plant or other organism
Define species
- the smallest and most specific taxonomic group.
- Can breed to produce fertile offspring
Define ecology
the study of the relationships between organisms and their environment
What is meant by ‘ecosystems are dynamic’?
dynamic ecosystems are constantly changing
Define biotic factor
living components of an ecosystem
e.g. species prescence, population size, competition for food source
Define abiotic factor
non-living factors of an ecosystem
e.g. rainfall vol, temp range, light intensity, wind speed
Define edaphic factor
factors to do with soil
What are the 3 main soil types?
1- clay - fine particles, easily waterlogged, forms clumps when wet
2- loam - different sized particles, retains water but doesnt become waterlogged
3- sandy - coarse, well-separated particles allowing free draining, doesnt retain water and easily erodes
Define food web
many interconnected possible routes of energy and biomass through an ecosystem
Define food chain
a single possible route of energy and biomass through an ecosystem
Define trophic level
each stage in a food chain - a feeding level
What do the arrows represent in a food web?
the direction of energy flow
Define heterotroph
another name for a consumer (eats plants + animals)
Define consumer
organisms that their and energy by feeding on other organisms
Define producer
an organism that converts light energy into chemical energy by photosynthesis
- producers are plants
Define primary consumer
animals that eat producers in a food chain
Define secondary consumer
an animal that eats primary consumers in a food chain
Define tertiary consumer
animals that eat secondary consumers in a food chain
Define herbivore
animals that eat plants - primary consumers
Define carnivore
animals that eat other animals - secondary consumer or higher
Define omnivore
animals that eat both plants and other animals
Define detritivore and give 2 examples
detrivore - animals that feed on decaying and dead material
e.g. woodlice and earthworms
Define decomposer
an organism that feeds on dead organic matter, turning the organic molecules into inorganic ones
e.g. fungi and bacteria
What is the role of detrivores in food webs?
detrivores speed up decay by breaking down detritus into smaller pieces
- increasing SA for decomposers to work on
What is the role of decomposers in food webs?
decomposers break down dead organisms releasing nutrients back into the ecosystem
Define biomass
the mass of living material present in a particular place or in particular organisms
Define dry mass
the mass of living material remaining once all the water has been removed
Why is dry mass a better indicator of biomass than fresh mass?
dry mass is a more reliable measure of mass as it excludes fluctuating water concentrations
Explain how to calculate the dry mass of each trophic level in a food chain
1 - organisms are killed and placed in an oven at 80 degrees c until all the water has evaporated
- this point is indicated by at least 2 identical mass readings
Explain how to experimentally measure the energy content of organic matter?
use a calorimeter - burn matter and measure the temperature rise of water
Which units are used for biomass in an ecosystem? - (land and aquatic)
land: gm^(-2) grams per metre squared
aquatic: gm^(-3) grams per metre cubed
Explain how pyramids of numbers, biomass and energy - represent data about an ecosystem and the negatives/positives of each when drawing a pyramid
- pyramids of numbers - show number of each organism in a food chain
- pyramid of biomass - shows mass at each trophic level in a food chain
- food chain almost always pyramid shaped - pyramid of energy - shows energy available frokm each level
- always pyramid - numbers - +easy to count - hard to draw due to variation
- biomass - +easy to draw
- energy - -hard to calculate
Which units are used for the energy at each trophic level in a food chain and explain why these units are appropriate?
- kJm^(-2)yr^(-1) Kilojoules per metre squared per year
appropriate -
per year to account for fluctuations in photosynthetic production and feeding patterns
How is energy transferred from one trophic level to the next?
biomass and the energy contain within its carbon compounds is transferred as…..
….. organisms feed on eachother.
- when animals eat, only a small proportion of the food is converted into new tissue (biomass)
- therefore only a small proportion of the energy is available for the next level to eat
Define ecological efficiency
the efficiency in which biomass/energy is transfered from one trophic level to the next
Write an equation on how to calculate ecological efficiency
calculated by:
- dividing energy/biomass available after the transfer BY the energy/biomass available before the transfer x 100 = %
What are 3 reasons why producers only convert 1-3% of of the sunlight they recieve into chemical energy and hence biomass (tissue)?
1- factors may limit photosynthesis like water avaliability
2- a proportion of the energy is lost bc its used for photosynthetic reactions
3- not all of the light energy available is used for photosynthesis
- approx 90% reflected - some transmitted through the leaf
- some unusable wavelength
Define gross production
the total solar energy that plants convert to organic matter
Define net production
the amount of energy available to the next trophic level
Define respiratory losses
the energy used in respiration so therefore not available to the next trophic level
Write an equation to link net production, gross production and respiratiory losses
net production = gross production - respiratory losses
Define primary production
generation of biomass in a producer
Define secondary production
generation of biomass in a consumer
Explain 4 reasons why consumers at each trophic level convert only a small amount of the biomass in the tropic level below (their food) to their own organic tissue
1- not all of the biomass of an organism is eaten e.g plant roots not consumed
2- some energy is transferred to the environment as metabolic heat
- bc of movement and respiration
3- some parts of an organism are eaten but are indigestable -
- parts (and their energy) egested as faeces
4- some energy is lost from the animal in excretory materials such as urine
Draw, label and annotate, a diagram showing the flow of energy through trophic levels and out of the food chain.
- energy lost at every level as heat from respiration
- all dead matter through decomposers and detrivores who also produce heat
Why does biomass decrease at each trophic level in a food chain?
- each level recieves less energy than the level before due to energy losses such as in respiration
Why are food chains with more than 4 trophic levels rare?
there is not enough energy available as biomass to sustain another tier of organisms
How have humans manipulated energy transfer through trophic levels in the farming of plants and animals to our advantage?
Plants+Animals
1 -provide with abiotic conditions needed to thrive
e.g. watering+warmth+nutrients (greenhouses+stables)
2 - Remove competition from other species
e.g. using pesticides
3 - remove threat of predators
e.g. barriers like fences
4 - minimise trophic levels so least amount of energy is lost in transfer as possible
e.g. agriculture -
–farming animals (3 trophic levels)
- producers (animal feed) -primary consumers (livestock) - secondary cons(humans)
— human plant consumption (2 trophic levels)
- producers (crops) - primary consumers (humans)
What is the equation for calculating ecological efficiency?
ecological efficiency =
biomass available after transfer/ biomass available before the transfer X100
Compare the movement of energy through an ecosystem, with the movement of nutrients like nitrogen and carbon
- energy moves through ecosytsmes in a linear way + is always replenished at the start by the sun
- nutrients like nitrogen and carbon are recycled round the ecosystem
- bc there is no large external source constantly replenishing them
Draw, label and annotate a diagram of the nitrogen cycle.
snaprevise flashcard
What is the nitrogen cycle? What are the 4 processes called?
- the movement of nitrogen by various processes
(happens as organisms need it but cannot take it up in its natural form)
1- Nitrogen fixation
2- Nitrification
3- Denitrification
4- Ammonification
What is the 1st step of the nitrogen cycle called?
Nitrogen fixation
Explain the first step of the nitrogen cycle?
NITROGEN FIXATION:
1 - nitrogen fixating bacteria AZTOBACTER and RHIZOBIUM contain enzyme nitrogenase which does:
2 - atmospheric nitrogen N2 combines with H2 to produce ammonia (NH3)
2 - ammonia (NH3) can be absorbed + used by plants
What are the 2 nitrogen-fixing bacteria called? where are they found? and which enzyme do they contain?
- Azotobacter - in the soil
- Rhizobium - in root nodules -(grow on roots of legume plants)
- contain enzyme nitrogenase
What is the 2nd step of the nitrogen cycle called?
Nitrification
Explain the 2nd step of the nitrogen cycle?
NITRIFICATION:
- conversion of ammonium compounds in the soil into nitrates and nitrites using nitrifying bacteria
1- nitrifying bacteria like Nitrosomonas oxidise ammonium compounds into nitrites (NO2-)
2- nitrobacter oxidise nitrites into nitrates (NO3-)
In which form does nitrogen enter the plant the most and why?
As nitrate ions e.g. NO2- and NO3- bc they are highly soluble
What is an example of nitrifying bacteria used in nitrification?
Nitrosomonas
What is the 3rd step of the nitrogen cycle called?
Denitrification
Explain the 3rd step of the nitrogen cycle?
DENITRIFICATION:
- if there is absence of oxygen e.g. waterlogged soils
1- denitrifying bacteria covert nitrates in the soil back to nitrogen gas
NO3 –> N2
Under only which state does denitrification happen?
only in anaerobic conditions
How do denitrifying bacteria convert nitrates into nitrogen gas?
by using nitrates as a source of energy for respiration – and nitrogen gas is released
What is the 4th step of the nitrogen cycle called?
Ammonification
Explain the 4th step of the nitrogen cycle?
AMMONIFICATION:
1 - decomposers convert nitrogen-containing molecules (in dead organisms, faeces+urine) into ammonium compounds
What is the importance of decomposers in the recycling of matter in ecosytems ?
- decomposers break down the organic matter into small inorganic molecules - that are then used by producers
C + N elements cant be used directly
What is the importance of detritivores in the recycling of matter in ecosytems ?
- detritvores speed up the decay process by breaking down organic material into smaller pieces (larger SA) for decomposers to work on
Define nitrogen fixation
conversion of nitrogen gas into ammonium compounds
Define nitrification
conversion of ammonium compounds into nitrites and nitrates
Define denitrification
conversion of nitrates into nitrogen gas
Define ammonification
conversion of nitrogen compounds in dead organic matter/waste into ammonium compounds by decomposers
Name the micro-organisms involved in the nitrogen cycle and state the nitrogen-containing molecule they use and the nitrogen-containing molecule they produce.
Nitrogen fixing bacteria (Nitrogen to ammonia) :
- Rhizobium in root nodules
- Azotobacter in the soil
Nitrifying bacteria :
- Nitrosomonas - ammonia to nitrites
- Nitrobacter from nitrites to nitrates
Denitrification
- Pseudomonas denitrificans - nitrates to nitrogen
Draw and label and annotate a diagram of the carbon cycle
snap revise flashcard
What is the carbon cycle?
when carbon is recylced through biotic and abiotic factors of the ecosytem, in the form of CO2/fixed in organic molecules
Why do CO2 levels in the atmosphere vary throughout a 24hr period, seasonally and over many years
- light intensity effects - rate of photosynthesis and therefore rate of use of CO2 varies
- at night CO2 levels higher as respiration continues, photosynthesis doesnt
- CO2 levels lower in summer bc more light more photosynthesis
What are 2 reasons why CO2 levels in the atmosphere have increased significantly over the last 200 years?
1- Industry - increased burning of fossil fuels -more CO2 released
2- Deforestation - fewer large areas of trees - less photosyntheis - less CO2 removed from atmosphere - cleared forest burnt = CO2
How do scientists gather data about the atmospheric carbon dioxide levels and temperature 1000s of years ago?
- look at ice poles formed 1000s yrs ago and never melted
- air bubbles trapped in ice tested
In the carbon cycle what happens to the dead organic matter and where does its carbon end up?
dead organic matter broken down by dcomposers and carbon end up in soil + atmosphere
Define succession
the directional change in communities over time due to habitat changes
Define primary succession
formation of a community on new bare land/no soil/no organic matter
Define secondary succession
formation of a community on land with soul but no plant or animal species
Define deflected succession
when the direction of succession is affected by farming or other human activities
e.g. grazing, mowing, burning crops
Define pioneer species
the first organisms to colonise bare land
e.g. lichen, algae
Define climax community
- the final stage in succession, the community is said to be in stable state
Define plagioclimax
stage in succession where artificial/natural factors prevent the natural climax community from forming
What are 5 adaptations of pioneer species that enable them to colonise bare land?
1- ability to produce lots of speeds/spores - are blown by the wind into the ‘new land’
2- seeds that germinate quickly
3- ability to photosynthesise to produce own energy
4- tolerant to extreme environments
5- ability to fix nitrogen from the atmosphere - adding to mineral content of the soil
What effect do pioneer species have on the environment?
as they die:
their organic matter makes the environment more able to support other species - creates humus for soil (nutrients etc)
How does the conditions of the soil change as succession occurs and why?
- weathering of bare rock produces particles that form basis of soil
- organisms of pioneer species die and decompose releasing small organmic products into the soil - humus
Explain why succession occurs
as a result of changes to the Environment (abiotic factors)
- causes plant and animal species to change
Define dominant species
the most abundant species in an ecosystem
Describe and explain the change in niche number and number of species (and so biodiversity) present as succession progresses
-niche number and biodiversity increase as succession continues
- as succession continues more organisms are available to eat and be eaten
- biodiversity can dip as climax community forms if a dominant species outcompetes others
What does niche mean?
the particular role a species has in its habitat is its niche
Why is secondary succession more likely to occur more quickly than primary succession
soil already present so there is no time spent eroding rock to form any soil
What are 3 reasons why deflected succession may occur?
- grazing + trampling of vegetation by domesticated animals
- removing existing vegetation to plant crops - crop becomes climax /final community
- burning to clear forests - often leads to increase in biodiversity as provides space+nutrient rich ash for other species to grow
How can the abundance of plants be estimated? and how can the population size be calculated from this?
1- sample with quadrats
2- multiply up to the size of the whole area
Describe how the caputre-mark-release-recapture technique can be used to estimate the population size of an animal species
- capture as many possible and mark them
- release and recapture as many as possible
- proportion marked will be same for entire population
What is the equation for the lincoln index to estimate the population size of an animal species
estimate of population size =
(number marked x number recaptured)/number of recaptured marked
What are the assumptions made when using the lincoln index to estimate population size?
- population is closed - no immigration/emmigration
- time between samples must be small compared to life span (no deaths)
- marked organisms must mix completely with the rest of the population between sampling
