Chapter 13 - Energy & Ecosystems Flashcards
Define population
All organisms of a single species in a habitat
Define community
All organisms of all species in a habitat
Define habitat
Where a organism lives
Define niche
The role of the species in an ecosystem and how it interacts
Define trophic level
Each stage of the food chain
Define gross primary productivity
The total amount of energy made my producers per unit of area per unit of time
What is net primary productivity?
The amount of chemical energy a producer stores as biomass per unit of area per unit of time and is the total amount of energy available to the next trophic level
Give the equation for NPP
NPP = GPP - RL
Give the equation for NP
NP = I - (R+F) I = Ingestion R = Respiration F = Shit
Why do trophic levels lose energy?
- Energy lost as heat due to respiration
- Not all is consumed
- Indigestible parts shat out
How do you calculate energy transfer efficiency?
Net productivity/Ingestion X 100
Summarise the general food chain
Sun - Producer - Primary Consumer - Secondary Consumer
How much energy is transferred to the producer from the sun and why?
- Approx 2%
- Not right wavelength
- Does not strike chloroplast
- Reflect by leaf or molecules in air
- Lost as heat
How much energy is transferred to the primary consumer from the producer?
- Approx 10%
- Respiratory loss for metabolism/ATP
- Lost as heat
- Not all plant is eaten
- Some food indigestible and shat out
How much energy is transferred to the secondary consumer from the primary producer?
- 10-15%
- Respiratory loss for metabolism/ATP
- Lost as heat
- Not all of animal is eaten
- Some foot indigestible so shat out
Give reasons as to why energy transfer efficiency is low
- Old animal has stopped growing
- Herbivores so more excretion
- Endotherms lose more energy as heat
How can we increase energy transfer efficiency in plants?
- Shorten food chain to reduce competition so more energy to create biomass
- Fertilisers to add phosphate/nitrogen to stop limiting growth
How can we stop the effect of fungi, weeds and insects and how does this help?
- Herbicide to kill weeds
- Fungicide to reduce fungus
- Insecticide to kill insects (either chemical or biological)
There is less competition so crop receives more light energy and creates more biomass
How can we increase energy transfer efficiency in animals?
- Reduce respiratory and excretion loss (R+F)
- Restrict movement so less respiration/less energy
- Keep warm so less respiration required
- Slaughter animal while still growing
- Keep predators away
- Controlled diet with antibiotics to ensure all digested
- High yield organisms
How can we measure biomass?
Take dry biomass by hearting on a scale until mass becomes constant, but low enough to ensure combustion does not occur (this will lose biomass)
Why do we remove water in biomass samples?
Different plants contain different water amounts and so different samples are not representatives
What is biomass measured in?
KG per M^2
How do we use calorimetry to estimate dry biomass?
- Burn substance completely to heat known volume of water
- Measure temperature change
- Calculate energy released
How do estimate dry biomass using mass of carbon?
- Organisms made from organic compounds with carbon
- Mass of carbon good indicator for biomass
- Difficult to measure but carbon is usually 50% of the dry biomass
Summarise the nitrogen cycle
- Inert N2 gas in atmosphere
- Fixed into ammonium ions (NH4+) by NFB
- Freeliving NFB in soil, mutualistic in leguminous roots
- NH4+ converted into NO3- by nitrification (NH4+ into nitrite ions NO2- into nitrate ions NO3-)
- NO3- absorbed by plants to make AA, proteins and nucleotides
- Consumers eat plant to obtain AA
- Organic material broken down by saprobiotic decomposers that secrete extracellular enzymes
- NO3- converted back into nitrogen gas by denitrifcation in anaerobic conditions
Summarise the phosphorus cycle
- Phosphorus present in rock as phosphate ions (PO4^3-)
- Erodes and leaves PO4^3-
- Plants absorb phosphorus
- Consumers eat plants
- Saprobiotic decomposers break down organic material and release phosphate ions back into soil
- Mycorrhizae fungus help uptake of these minerals
How do microorganisms play a role in the nutrient cycles?
- Saprobionts use extracellular enzymes to break down large organic compounds into smaller ones
- These are absorbed by producers
- Microorganisms also absorb inorganic ions across their membrane
- Mycorrhizae fungi has a mutualistic relationship: fungi increases SA for absorption for plants and the fungi receives organic compounds from plant
How does eutrophication occur?
- Soluble compounds washed off the land by rain
- Runs into water sources
- Algae bloom
- Blocks light so plants underneath cannot photosynthesis
- Plants die, so broken down by sapribioptic decomposers and use oxygen to respire areobically
- Fish die
- Hence bad
Why is fertiliser needed when crops are harvested?
Nitrogen and phosphorus removed from the cycle so replaced with fertiliser
Why is too much fertiliser a negative?
Changes water potential so less water absorbed and harder to absorb other molecules
What is good/bad about natural fertilisers?
- Aerate soil
- Contain wide range of substances
- Less leaching
- Consume less energy to create
- Still require the breaking down by saprobionts so slow release of N and P
