Energy And Ecosystems Flashcards
Define producers
Photosynthetic organisms who manufacture organic substances
Define consumers
Organisms that gain energy from consuming other organisms
Define saprobionts
Decompose waste and remains of dead organisms
What is the difference between food chains and webs
Food chains show one organism at each trophic level
Food webs show complex interrelations of many food webs
Pros and cons of food webs
Show more realistic consumption as organisms will have more than one food source
Can get very complex
Define trophic level
Stages of food chain
What do arrows in food chains depict
Transfer of energy along chain
Define biomass
Mass of living material
Why is dry material used not fresh
Fresh will vary due to water availability
Dry is more accurate
What are the cons of using dry mass
Have to kill organisms so only small sample obtained which is not representative
What are the units for biomass
Grams per metre squared
Describe. How to use a calorimeter
Weigh the sample and place in cup in chamber
Ignite using ignition wires
Record initial temp
Heat from combustion heats water
Record max temp
What temp is used for calculating dry biomass, why
100
Water evaporates and biomass doesn’t burn
When does all the energy in an ecosystem originate and end up
From the sun
Ends up are heat energy
What is the major difference between the transfer of energy and nutrients in an ecosystem
Nutrients can be recycled
Energy cannot
Why is only 1% of the sun’s energy transferred by plants
Rays reflected back into space via clouds and dust
Not all wavelengths used in Photosynthesis
Other factors are limiting (co2)
Light may not land on a chlorophyll
How and why can net primary production be used to compare ecosystems
Allow comparison between efficiency of energy storage
Define net primary production
The rate at which plants store energy
Define the gross primary production
The energy converted into biomass
Why is there a low percentage of energy between trophic levels
Not all of organism is consumed
Some parts can’t be consumed
Energy lost via excretion and movement
Heat energy lost via Respiration
Why is there a higher percentage energy transfer between 2 and 3 trophic levels
Carnivores use more of there food than herbivores
In what instances is energy transfer lower
Older animals
Mammals (heat lost to maintain temp)
Primary consumers
What are the results of inefficient energy transfer
Food chains have few trophic levels
Total biomass at higher trophic levels is less
Less energy available for higher trophic levels
Why do organisms require nitrogen
Amino acid, protein and nucleic acid synthesis
What form of nitrogen do plants absorb
Nitrate ions
How are nitrates absorbed by plants
Active transport
Why do nitrates need regular replenishment
They are leached (because soluble) and used up
What are the processes in the nitrogen cycle
Nitrogen fixing
Ammonification
Nitrification
Denitrification
Describe nitrogen fixing
Nitrogen gas from atmosphere converted into ammonia
In what ways can nitrogen be fixed
Atmospheric (lightning)
Industrially
Biologically
What types of nitrogen fixing bacteria are there
Free living and mutualistic
Describe how mutualistic nitrogen fixing bacteria interact with plants
Assimilate ammonia into Amino acids and exchanged for carbohydrates
Describe how nitrogen fixing bacteria work
Reduce nitrogen to ammonia
Aerobic Respiration
Describe the process of Ammonification
Saprobionts convert ammonia to ammonium ions
From what does Ammonification take place
Waste and dead material
Urea
Protein
Nucleic acids
Vitamins
Describe Nitrification
Conversion of ammonium ions to nitrite ions then nitrate ions by aerobic bacteria
Describe nitrifying bacteria
Chemotrophs= use chemical to produce food not light
Aerobic
Describe Denitrification
Conversion of nitrate ions into nitrogen gas by anaerobic denitrifying batería
Describe denitrifying bacteria
Anaerobic
Use nitrate ions instead of oxygen.
Describe denitrifying bacteria
Anaerobic
Use nitrate ions instead of oxygen.
How can to productivity of soils be improved other than fertilisers
Aerate soils= more oxygen= more nitrification= more nitrate ions
More DOM= more Ammonification
What forms of nitrogen can plants use
Ammonia
Nitrate ions
Describe how saprobionts work
Secrete enzymes for extracellular digestion
Macro molecules hydrolysed to micromolecules which diffuse into bacteria
Aerobic Respiration
In what form is phosphorus found in the phosphorus cycle
Phosphate ions
What are the differences between the phosphorus and nitrogen cycle
Phosphorus is never gaseous
Nitrogen is fast
Phosphorus can be found in skeletons and shells
Phosphorus is released from rocks via Weathering
What is phosphorus used for
DNA
Phospholipids
ATP
Describe the phosphorus cycle
Phosphates in rock are released due to Weathering and erosion
Phosphate ions are in the sea and rivers
Absorbed by plants and move along food chain
Waste and dead material contain phosphates which are broken down by saprobionts
Phosphates released into rivers where they sediment to form rocks
Describe the nitrogen cycle
Nitrogen gas is converted into ammonia by nitrogen fixing bacteria
Ammonia is absorbed by plants and passed along food chain
Waste and dead matter contain ammonia compounds which are converted into ammonium ions via saprobionts
Ammonium ions converted into nitrite and then nitrate ions by nitrifying bacteria
Nitrates absorbed by plants
Denitrifying bacteria convert nitrates into nitrogen gas
What microbe is involved in the phosphorus cycle
Mycorrhizae fungi
Describe the interaction between the micorrhzae and plants
Fungi grows in and around plant tissue
Highly specific to species
Coevolution
Increase surface area for absorption of water and mineral ions
Act like sponge so plant is drought resistant
Exchange mineral ions for carbohydrates
What type of organism are micorrhzae
Saprobionts
Why do we need fertilisers
Intense farming disrupts nutrient cycles depleting soils of nutrients
Biomass removed so no decomposition
Increases productivity
What needs to be ensured for fertilisers to have maximum effect
Applied at right time and right amount
What types of fertilizers are there
Natural and artificial
What are artificial fertilizers made of
NPK
mined from rock deposits
What are the benefits of artificial fertilizers
Immediate source of mineral ions
Guaranteed composition
More concentrated= less needed= cheaper (transport and supply) and less damage done by machines
Clean and convenient
What are the cons of artificial fertilizers
Leaching and eutrophication
Mining causes damage
What are natural fertilisers made of
Dead matter and waste
Bone meal
Urea
Manure
Compost
What are the pros of using natural fertilisers
Lasts longer
Longer release
May contain important trace elements
Improve soil structure (reduced erosion and better at holding water)
How do fertilizers increase crop yield
Provide vital mineral ions
Converted into Amino acids, lipids and DNA
Larger biomass= Larger leaves
Large SA for Photosynthesis= more carbohydrates = taller
What are the environmental effects of fertilisers
Reduced species diversity
Leaching
Eutrophication
How do fertilizers lead to reduced species diversity
High N conc favours grasses and nettles which outcompete other species
Describe leaching
Rainwater dissolves nitrate ions
Carries them far down into soil
Roots are unable to reach ions
Found in rivers and lakes and drinking water
Why is leaching bad
Nitrates end up in drinking water
Can cause stomach cancer
Prevent efficient oxygen transport in babies
Eutrophication
Describe how eutrophication occurs an dits effects
Nitrates are usually limiting factor in lakes
N conc increases, no longer limiting so algal bloom
Light doesn’t reach lake floor
Photosynthesising plants lower down die
Less oxygen produced
Decomposition increases so more saprobionts
Oxygen is limiting for aerobic organisms
Aerobic organisms die so less competition between aerobic and anaerobic organisms
More decomposition so more nitrates and toxic substances (hydrogen sulphide) = putrid water
