Chapter 13 - Energy and Ecosystems Flashcards
What is the source of energy for an ecosystem?
Sunlight
Define biomass
Total dry mass of living material measured in specific area or over a given time period. Measured in grams per m2 or m3
Define producers
Plants that perform photosynthesis and use light to make biological molecules
Define consumers
Organisms that obtain their energy by feeding on other organisms as they cannot make biological molecules from sunlight. Two types: primary and secondary
Distinguish between primary and secondary consumers
Primary are first consumers in the chain that feed on producers
Secondary consumers feed on primary consumers
Define saprobionts
Also known as decomposers/ Organisms that break down complex materials in dead organisms to simples ones. They include bacteria and fungi and perform saprobiotic decomposition
What is a food chain?
Chain describing feeding relationship where producers eaten by consumers etc. Each stage is called a trophic level
How can the chemical energy in dry biomass be estimated?
- Bomb calorimetry
- Dry material weighed then burnt in oxygen surrounded by water
- Specific heat capacity used
Why do producers need biological molecules?
- Glucose for respiration and make starch/glucose
- Amino acids for proteins
- Fatty acid + Glycerol for triglyceride and membranes
Why do consumers need biological molecules?
- Glucose for respiration and store glycogen
- Amino acids for proteins
- Fatty acid + Glycerol for triglyceride, insulation and membranes
Why do decomposers need biological molecules?
- Glucose for respiration
- Amino acids for proteins
- Fatty acid + Glycerol for membranes
How much energy is harnessed from the sun by producers?
1% - 3%
Why is most of the suns energy not converted into organic matter by producers?
- 90% reflected back into space
- Not all wavelengths of light absorbed
- Light does not fall on chlorophyll molecule
- Limiting factors such as low CO2
What is gross primary production?
Total chemical energy store in plant biomass in a given area or volume
Give the equation for net primary production in plants
Gross primary production MINUS respiratory losses
What are the reasons for low energy transfer between trophic levels?
- Some of organism not consumed
- Some parts consumed by not digestible so lost if faeces
- Some lost in excretory materials
- Energy lost as heat from respiration
What is the equation for the net production of consumers?
N = I - (F+R) N = net production I = Chemical energy of ingested food - F = Energy lost in p=faeces R = Energy lost in respiration
Inefficiency of energy transfer in trophic levels explains what?
- Max four or five trophic levels
- Total biomass less at higher trophic levels
- Total amount of energy available less as trophic levels progress
What is the percentage efficiency equation for energy transfer?
Energy available after transfer divided by energy available before transfer multiplied by 100
How much energy is transferred from producer to consumer?
10%
How much energy is transferred from consumer to consumer?
20%
Why is energy transfer high between consumers?
Consumers more edible and digestible whereas producers made up of cellulose
Describe the path taken by nutrients
- Nutrient taken up by producers
- Producer incorporates nutrient into complex molecule
- Consumer eats producer and nutrients
- Passes along food chain
- When consumer dies, saprobiotic decomposition occurs releasing nutrients
Summarise the WHOLE nitrogen cycle
- Nitrogen in atmosphere as gas N2
- Plants can only absorb NO3-
- N2 converted into ammonium ions NH4+ by nitrogen fixation by nitrogen fixing bacteria (mutualistic in roots of leguminous plants or free living in soil)
- NH4+ converted into NO3- ions by nitrification by nitrifying bacteria
where NH4+ oxidised into NO2- then oxidised into NO3- - NO3- absorbed by plants to make AA/proteins
- Consumers eat plant to obtain AA
- Organic material broken down by saprobiotic decomposers releasing NH4+ into soil (ammonification)
- Nitrate ions (NO3-) converted back into N2 gas by denitrification by denitrifying bacteria
- Denitrifying bacteria work in anaerobic conditions e.g waterlogged fields
Why do organisms need phosphorus substances?
- Phospholipids
- DNA
- ATP
Summarise the WHOLE phosphorous cycle
- Phosphorous present in sedimentary rock as phosphate ions PO4 3-
- Sedimentary rock erodes leaving soil with PO4 3-
- Plants absorb PO4 3- to make phospholipid/DNA/ATP
- Consumer eats plants
- Saprobiotic decomposers releases PO4 3- back into soil
- Mycorrhize fungi in roots of plants support uptake of scarce materials such as phosphate ions by increasing SA and acting like a sponge
What is an agricultural ecosystem?
- Farming ecosystems
- Grows crops and raise animals
How are crops intensively farmed for high yield?
- Suitable location with lots of water, sunlight and minerals
- Clear area of plant and animals (deforestation removes competition and pests)
- Selectively breed crop
- Greenhouse for high levels of light, CO2 and temperature
- Water by irrigation
- Fertilisers
- Control pests
- Crop rotation ensure mineral levels do not deplete
- Ploughing to add air spaces, bacteria involved in nutrient cycles can aerobically respire
Distinguish between natural and artificial fertilisers
Natural = Dead/decaying remains Artificial = Mined from rocks and applied in appropriate balance
What are pests?
Organisms that harm plants/crops as they compete/eat or disease the plant
What are the two ways that pests can be controlled?
Pesticides or biological control
What are pesticides?
Chemical sprays that kill the pest
What are the advantages and disadvantages of pesticides?
Advantages:
Fasting acting and can control area covered
Disadvantages:
Non-specific and nonbiodegradable so bioaccumulation occurs
Pests may be resistant
Reapplication
What is biological control?
Using predators or parasites to control the pest
What are the advantages and disadvantages of biological control
Advantages: Specific No bioaccumulation No resistance and no reapplication Disadvantages: Slow acting May become pest Cannot control area covered
What is bioaccumulation?
Pesticides not biodegradable so remain in organisms tissues. Accumulate along food chain up trophic levels and toxic to consumers on high trophic levels
What three minerals do fertilisers provide?
Nitrate for AA
Phosphate for DNA/ATP and phospholipids
Magnesium for chlorphyll
Debate natural and artificial fertilisers
Natural has reduced risk of eutrophication but slower release
Artificial has faster release but more risk of eutrophication and lowers water potential of soil
What is the benefit of ploughing?
Aerates soil increasing air spaces supporting aerobic respiration (more nitrogen fixation and less denitrifying bacteria)
Summarise eutrophication
- Large amounts of fertilisers
- Leaching into water sources
- Builds up in ponds
- Increased algae growth (algae bloom)
- Prevents light reaching bottom of water
- Plants do not photosynthesis so die
- Saprobiotic decomposers use oxygen in water from respiration
- Fish die
How do the four ways of crop farming affect the environment?
Deforestation reduces species/plant diversity and less habitats/food
Monoculture depletes nutrients
Selective breeding reduces genetic diversity
Pollution causes bioaccumulation and eutrophication
What five ways can we reduce the impact of crop farming?
Native trees for species diversity
Hedgerows for species diversity
Polyculture and crop rotation to prevent depletion of nutrients
Wild crops maintain genetic diversity
Biological control and natural fertiliser
How are animals reared in farming?
- Selectively bred
- Pre digested food with antibiotics and vaccines
- Hormones
- Restricted movement and kept warm
