Energy transfers in and between organisms Flashcards
(48 cards)
Most of the sugars synthesised by plants are used by the plant as what?
Respiratory substrates
Fill in the blanks:
NPP = ___ - R
GPP
NPP stands for what?
Net primary production
What is net primary production?
Net primary production (NPP) is the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.
How do you calculate net production of consumers (N)?
N = I - (F + R) where
I represents the chemical energy store in ingested food
F represents the chemical energy lost to the environment in faeces and
urine
R represents the respiratory losses to the environment.
Give the definition of a producer.
Organisms that can manufacture organic compounds from simple inorganic molecules
Give the definition of a saprobiont.
A decomposer - an organism that breaks down and feeds on dead decaying matter
Give the definition of a food web.
A way of showing feeding relationships within an ecological community
Give the definition of a trophic level.
It describes the stage an organism occupies in a food chain
Give the definition of biomass.
The total dry mass of living matter in a specific area at a given time (gm-2)
Give the definition of gross production
The total quantity of energy that the plants in a community convert to organic matter during photosynthesis
What would the units be if you were measuring biomass in an area over the period of a year?
kJm-2y-1
Why is not all of the sun’s energy absorbed?
Goes through leaves Wrong wavelength to be useful May not hit chlorophyll Converted to heat during reactions May be a limiting factor present
How do you calculate energy transfer efficiency?
energy transfer = energy available AFTER transfer / energy available BEFORE transfer x100
A wolf ingests 193 kJm-2y-1, has a net production of 77 kJm-2y-1 and respiratory losses equaling 48 kJm-2y-1. What does F equal?
N = I - (F + R) 77 = 193 - (F + 48) F + 48 = 193 - 77 F = 193 - 77 - 48 F = 68
What can we measure biomass in terms of?
Mass of carbon or dry mass of tissue per given area per given time
How can we estimate the chemical energy store in dry biomass?
Calorimetry
Nitrifying bacteria do what?
Oxidise ammonia (NH3) to nitrite (NO2-) or nitrite to nitrate (NO3-)
Why is such a low percentage of energy transferred at each stage of a food chain?
Some of organism is not consumed
Some parts are consumed but unable to be digested - lost in faeces
Some energy lost in excretory products such as urine
Some energy losses occur as heat from respiration
Why are there usually only 4 or 5 trophic levels in a good chain?
Inefficiency of energy transfer between levels means that there insufficient energy at the higher levels to support large enough breeding population/not enough energy to transfer
Give the general sequence of all nutrient cycles
Nutrient taken up by producers as simple inorganic, molecules
Producer incorporates the nutrient into complex organic molecules
When the producer is eaten, the nutrient passes into consumers
The passes along a food chain
When these organisms die, complex molecules broken down by saprobiontic microorganisms
Nutrients released in original form
What are the 3 ways nitrogen can be fixed?
Nitrogen fixing bacteria
Industrial fixation (Haber process)
Energy from lightning splits N molecules, allowing it to react with O2. It is then washed to the ground by rain
What do denitrifying bacteria do?
Convert nitrate (NO3) into nitrogen (N2)
What conditions do denitrifying bacteria work in?
Anaerobic
