6.3.1 ecosystems Flashcards
define ecosystems
a biological community of abiotic and biotic factors interacting in their physical environment
population
all the organisms of a single species in a habitat
community
all the organisms of all the species in a habitat
niche and examples
the role of a species in a ecosystem
e.g. what it feeds on, what it excretes
tropic level
each stage of the food chain
producer
makes their own organic molecules
consumer
cannot make their own organic molecules, have to eat another organism
decomposer
lives on DOM and waste materials
why is it impossible for 2 species to occupy the same niche in the same ecosystem?
- the competition would be too strong
- one species would out compete the other
what does it mean by ecosystems are dynamic?
- they are constantly changing due to factors affecting the populations of different organisms and environmental changes
what are the 3 types of changes that cause ecosystems to be dynamic?
- cyclic
- directional
- erratic/ unpredictable
what is a cyclic change?
- changes repeat in a rhythm
e.g. movement of tides, predator-prey numbers, seasons
what’s is a directional change?
- changes in 1 direction that last a long time
e.g. erosion of coastline
what is an erratic/ unpredictable change?
- no rhythm/ particular direction
e.g. hurricanes, storms, erupting volcanoes
6 examples of biotic factors
- producers
- consumers
- decomposes
- diseases
- competition
- human activity
what is a producer?
AUTOtroph ( can make own organic molecules)
- self feeding level
- convert sole energy into chemical (bio mols)
what is a consumer?
HETEROtroph (cannot make own organic molecules)
- primary = herbivore
- secondary + tertiary = carnivore
what is a decomposer?
SAPROtroph (cannot make own organic molecules)
- bacteria and fungi which feed on DOM + waste products
examples of abiotic factors
- temp
- pH
- oxygen conc
- co2 levels
- wind speed
- light intensity
- salinity of water
- humidity
organisms can only tolerate a certain range of abiotic factors. what do extreme values cause?
- can cause species to perform better/ worse/ die
- called lethal extremes
what does energy leave an enter an ecosystem in the form of?
- enters via sunlight
- leaves via heat
how are nutrients different to energy?
they are constantly recycled within an ecosystem
define biomass
all of the organic molecules and inorganic substances ( excluding water) in an animal / plant
- represents chemical energy passed along food chain as organisms are eaten
what is passed along a food chain?
biomass and energy
describe plants as producers
photoautotrophs
- use light energy and inorganic mineral ions to produce organic molecules by photosynthesis
describe producers at bottom of deep ocean vents
- no sunlights
- called CHEMOautotrophic bacteria
- use energy from chemical reactions to produce organic molecules for growth
- if these bacteria are consumed, energy is passed up the food chain
what are pyramid of numbers?
- where the NUMBERS of organisms at each trophic level are counted and represented as a”pyramid”.
- The AREA of each bar is proportional to the numbers of organisms at that tropic level at THAT POINT IN TIME
How would you collect the data to plot a pyramid of numbers?
-collect all of the living organisms in a given area,
-sort them into trophic levels ,
- count the NUMBER of organisms in each trophic level.
what units are pyramids of numbers usually presented in?
m-2
advantages of pyramids of numbers?
- simple and easy method
-quick - can compare changes in number over time
disadvantage of pyramid of numbers?
- small organisms are harder to count
- difficult to sort into trophic levels (consumers feed on a variety of food)
- doesn’t take in account size of organism
what is a pyramid of biomass?
dry mass of all organisms at each trophic level in a food chain at ONE PARTICUALR POINT IN TIME
how would you collect the data for pyramid of biomass?
- collect and sort organisms into trophic levels
- put in oven at 180 degrees celsius
- keep weighing until no further change in mass
units for pyramid of biomass
land - gm-2
water - gm-3
or kgm
advantages of pyramids of biomass
- takes into account organisms are diff sizes
- more likely that pyramid is not inverted
- more accurate representation of energy at each trophic level
disadvantages of pyramid of biomass
- destructive/ involves killing organisms
- difficulty sorting organisms into trophic levels (consumers feed on a variety of things)
what is a pyramid of energy?
represents how much energy is present at each trophic level/ flow of energy between trophic levels over a period of time
what are pyramids of energy always?
always pyramid shaped
how would you collect data for a pyramid of energy?
- collect dry mass
- burn organisms in a calorimeter to see how much heat they release
units of a pyramid of energy
Kjm-2yr-1
advantages of a pyramid of energy
- most accurate representation of energy flow between trophic levels
- pyramids never inverted
- solar energy included in diagram
disadvantages of pyramid of energy
- destructive
- hard to sort into trophic levels
equation for ecological efficiency
EE = energy or biomass available after transfer / energy or biomass available before transfer
x100
it is a percentage
whag do plants convert sunlight energy to?
chemical
why do plants only cover 1-3 percent of sunlight to chemical energy?
- some light is the wrong wavelength, so it is not absorbed by chloroplasts, light is reflected
- some is transmitted through leaf, doesn’t hit chloroplasts
- some is used to make more sugars, some released as heat
- other factors like O2 conc and H2O availability
equation for net productivity
NP = gross productivity- respiration
what is NP
what is passed onto next trophic level
what is gross productivity?
all the sugars made
what do consumers convert the biomass in food they eat to?
into their own biomass
why do consumers only covert 10-20 percent of biomass in food to their own biomass?
- not all of the organisms is eaten (roots, feathers, bones)
- not all the food is digested, plant material is high in cellulose so is removed as faeces, energy lost
- food not all used for growth, some is respired, heat lost
what is the new biomass?
secondary productivity
what happens to the number of levels in a food chain as you move up the food chain and why?
the number of levels are limited as energy is lost between each trophic level
examples of detrivores
earthworms and wood lice
examples of decomposers
saprotrophs
- feed on faeces released by detrivores
- bacteria and fungi
- digest food externally by releasing enzymes onto DOM to break down large organic molecules into smaller, with they reabsorb for energy and growth, they release mineral ions and inorganic elements back into the environment which are re-used
what do detrivores do?
feed on DOM which passes though internal digestive system into smaller fragments, which increases surface area and passes out as as faeces
when an animal eats an animal the energy transfer is 15-20%, when an animal eats a plant the energy transfer is 5-10%. why?
- plant material contains lots of cellulose
- cannot be digested as animal doesn’t have cellulose enzyme
- passes through animal undigested and comes out as faeces
- so energy is lost
- animals easier to digest, have enzymes and less energy is lost
define productivity
rate at which energy passes through each trophic level
define photosynthetic efficiency
measure of how effective crop plants are at converting solar energy into plant growth
photosynthetic efficiency % equation
amount of solar energy converted into carbohydrate/ total solar energy falling onto the top
x100
6 ways to maximize productivity
- max energy input
- max growth
- controlling disease
- controlling predation
- minimizing comp for resources
- minimizing energy losses
how does maximizing energy input maximize productivity?
- crop growth
leave optimum space between crops for light to reach all plants for photosynthesis, artificial lighting can be used if plants are grown in a glass house - livestock farming
provide high quality feed with a high energy content and protein content
how can maximizing growth maximize productivity?
- crop growth
irrigation keeps crops well watered,
you can use fertilizers containing N/P/K, selective breeding - livestock farming
food supplements, like vitamins and minerals, choose a variety of animals that grow quickly and produce a lot of muscle tissue and less fat
how can controlling disease maximize productivity?
- crop growth
fungicides to kill fungi - livestock farming
vaccination and antibiotics
how does controlling predation maximize productivity?
- crop growth
fencing/ netting to keep herbivores and insecticides - livestock farming
fencing around fields, putting them indoors
how can minimizing competition for resources maximize productivity?
- crop growth
herbicides for weeds + don’t plant crops closely together - livestock farming
keep animals out that compete with farm animals for food
how can minimizing energy losses maximize productivity?
- crop growth
choose plants that put more energy into growth of the edible parts - livestock farming
restrict animal movements, keep them in small spaces so they waste less energy
why do humans tend to occupy the 2nd and 3rd trophic levels?
it is beneficial as the lower down in the food chain we are the more energy is available
advantages with maximizing productivity
beneficial as more food is produced in a shorter space of time at a lower cost
disadvantages of maximizing productivity
animals are caused pain and distress and it restricts their natural behaviour
difference between energy flow through an ecosystem and nutrients in a ecosystem
energy flow is linear, nutrients are recycled (no external supply entering system)
The carbon cycle
• Carbon is found in all organic molecules (e.g. carbohydrates, proteins, lipids, nucleic acids)
• It enters food chains via producers, carrying out photosynthesis to convert inorganic carbon (CO2) into organic molecules (initially sugars). The plant can use this to make all of the organic molecules it needs.
• The plant is then eaten by an animal, passing the organic carbon- containing molecules up the food chain
• Carbon is constantly being returned to the atmosphere, in the form CO2, by the process of RESPIRATION (this can be re-used in photosynthesis)
• When an organism dies or sheds material (leaf fall, fur, feathers etc.), they are decomposed. The decomposers use the organic molecules in this DOM for their own growth and also for the process of respiration – so release CO2 back to the atmosphere
• Sometimes, DOM does not decompose, because the conditions are not right.
• If DOM does not decay, it can end up forming fossil fuels. Burning of these returns CO2 back to the atmosphere
Trees can act as “Carbon Sinks” What does this mean?
- trees use CO2 to make organic molecules during photosynthesis which are used for growth. carbon is locked up until the tree dies, once the tree decomposes CO2 is released by decomposers during resp
Peat bogs can act as “Carbon Sinks” What does this mean?
they are acidic and anaerobic, so decomposers can’t survive there, so any DOM remains, so CO2 is not released by respiration of the decomposer
what promotes activity of decomposers and how?
aerating the soil, e.g. digging the soil, ploughing
- aerobic decomposers will respire at a faster rate, so DOM will be broken down faster, and carbon recycled faster
Why are atmospheric CO2 levels higher at night than during the daytime?
At night, there is no photosynthesis occurring, so plants are not removing CO2 from the atmosphere, but they are still respiring – releasing CO2
Why are atmospheric CO2 levels higher on a day in winter compared to a summer day?
The rate of photosynthesis is lower in the winter (lower light intensities, lower temperatures), so less CO2 is used up by plants
why is sampling ice from glaciers done?
bubbles of air trapped show composition of air at that time (deeper sample = older)
Nitrogen gas makes up approximately 78% of the atmosphere, but nitrogen in this form is useless to most organisms
Why?
It is in the form of N2, which has a triple bond and is very stable/unreactive
