Energy transfers in and between organisms Flashcards
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
What is ammonifcation?
The production of ammonia from organic nitrogen-containing compounds
Name a compound that could be classified as an organic nitrogen
CHON Urea Proteins Nucleic acid Vitamins
Name the two main types of microorganisms which carry out nitrogen fixation
Free-living nitrogen-fixing bacteria
Mutualistic nitrogen-fixing bacteria
What is a mutualistic nitrogen-fixing bacteria?
Bacteria that live in the nodules of the roots of plants. Bacteria fix the nitrogen and provide amino acids. The bacteria obtain carbohydrates from the plant in return
Describe the nitrogen cycle
Nitrogen fixation - N2 –> N containing compounds (NH3 often)
Nitrification - Oxidise NH3 to nitrite (NO2), and that to nitrate (NO3)
Taken up by roots (consumed by animal)
Ammonification - org N containing compounds back to NH3
What are mycorrhizae?
The associations b/w certain types of fungi and the roots of a the vast majority of plants
How is the mycorrhizae relationship mutualistic?
Fungi acts as extensions - ++SA so better water and ion uptake for plant
Mycorrhiza acts as sponge and so holds water around roots - good if drought
Fungi receives org compounds (e.g. sugars and amino acids)
What are the two types of fertilisers?
Natural (organic)
Artificial (inorganic
What do organic fertilisers consist of?
Died and decaying remains of plants and animals
Animal wastes e.g. manure, slurry and bone meal
What do artificial fertilisers consist of?
Mined rock deposits which have been converted into different forms and blended to give an appropriate balance
How do fertilisers increase productivity?
By ensuring the minerals necessary for plant growth are readily available
Describe the negative effects of nitrogen-containing fertilisers
Reduced species diversity
Leaching
Eutrophication
Explain how nitrogen-containing fertilisers cause reduced species diversity
N rich soils favour the growth of rapidly growing species, which out compete other species and cause their death
What is leaching?
The process by which nutrients are removed from the soil
Why is leaching bad?
The leached nutrient ions can contaminate watercourses. If the water source is drinking water, it can be bad as v high nitrate ion conc. can affect the health of humans
Eutrophication
What happens in eutrophication?
++ nutrients –> algal bloom
Water surface covered - X light –> plants die
X plants producing –> algae uses all up and dies too
Dead algae and plants broken down by bacteria –> release nutrients –> algal bloom
Bacteria decompose plants - reproduce
Bacteria use up ++O2, and w/ no plants water –> anoxic (X O2)
Non bacterial aerobic repairers die (fish)
Broken down –> ++nutrients released –> algal bloom
What is an advantage of using organic fertilisers?
Cheap
Improves soil structure
Provides ‘food’ for soil
Better for environment
What disadvantage of using organic fertilisers?
Bulky
Need to use more as less concentrated
May contain unwanted substances
Take time - can’t be taken up directly
What is an advantage of using inorganic fertilisers?
Very effective
Inorganic ions - readily available to be taken up
Compact
What are the disadvantages of using inorganic fertilisers?
More expensive
Bad for environment - leaching, eutrophication
Give an example of an abiotic factor
Presence of water Temp O2 conc in water Light intensity Availability of food
Give an example of a biotic factor
Predation
Competition
Disease
Define abiotic factor
Non-living factors which affect living organisms and ecosystems
Define biotic factor
Living factors which affect living organisms and ecosystems
