5.3-4 energy in ecosystems Flashcards
define producer
autotrophs - make their own food from photosynthesis
define primary secondary and tertiary consumer
primary - animals that eat the producer
secondary - usually eat anima material
tertiary - eats secondary consumers
define tropic level
the positions occupied by a species in a food chain
define biomass
a chemical store of energy and the total mass of living material
3 steps of measuring dry mass
- try a tissue in an oven set to 40-80 degrees as too high could burn sample
- weigh the samples at regular intervals until the mass becomes constant
- once the mass becomes constant all the water will have evaporated
how to measure biomass
mass of carbon present in the biomass can be calculated using a calorimeter.
burning the biomass and measuring the energy given off as heat tells you how much energy is in the biomass
define productivity of an ecosystem
the rate of generation of biomass
define GPP
gross primary productivity is the total amount of chemical energy converted from light energy by plants
4 reasons why not all the light energy from the sun is converted to chemical energy
- reflected
- transmitted through the leaf
- the wrong wavelength
- hits parts of the plant that cannot photosynthesis
how much os the GPP is approximately lost to the environment when plants respire and what it is known as
50%
respiratory loss (R)
what is NPP
net primary productivity is the energy available to the plant for growth and reproduction
how to calculate NPP
NPP = GPP - R
how much % of energy is passed to the next trophic level
10%
why is only 10% of energy passed to next trophic level (3 points)
- not all food is eaten such as plant roots/bones
- some parts are indigestible so the energy in these parts are returned to the environment as faeces
- some energy is lost to the environment as heat produced during respiration and during excretion of unrine
define the net secondary production
the energy that is left and stored in the consumers biomass which is available in the next trophic level N = I(F+R)
how to work out the % efficiency of energy transfer
(net production of trophic level / net production of previous trophic level) x100
2 ways to increase NPP of crops and NP of livestock by increasing yeilds
- reducing energy lost to pests by simplifying food webs
- reducing respiration of livestock so more energy used for growth so more food is produced in less time
3 ethical reasons to not increase NPP and NP
restricts the natural behaviour causing pain through discomfort issues
disease could spread more likely
using pesticides can have a negative impact of the surrounding environment
4 steps of the nitrogen cycle
- nitrogen fixation
- ammonification
- nitrification
- denitrification
explain nitrogen fixation
nitrogen gas is reduced by adding H2 to form ammonia
catalysed by nitrogenous enzyme in bacteria
explain ammonification
microorganisms that feed on the remains of dead animals and plants known as saprobiotic nutrition
they secrete enzymes breaking down organic molecules which they then absorb (extracellular digestion). Break down amino acids in organic matter converting them into ammonium compounds forming ammonium ions in soil
explain nitrification
carried out by specialised bacteria where is converts ammonium compounds into nitrates (oxidised)
energy is released in reactions and bacteria used this to carry out chemiosmosis
(oxidised once to nitrites then again to nitrates)
explain denitrification
nitrates are converted into nitrogen gas by bacteria in anaerobic conditions. using nitrate ions as electron acceptors for respiration instead of oxygen which produces nitrogen gas which is released into the atmosphere hence reducing the amount of nitrates in the soil
where is phosphorous mostly stored
as the ion PO43- in sedimentary rocks and released where they weather
