Energy and Ecosystems Flashcards
What is an ecosystem?
All interacting abiotic and biotic factors in an area
What is a habitat?
Where the community is found
What is an omnivore?
An animal that eats both plants and animals, so can be a primary, secondary or tertiary consumer
What is a carnivore?
An animal that eats meat, so can be a secondary or tertiary consumer
What is a herbivore?
An animal that eats plants (producers), so is a primary consumer
What are saprobionts?
Group of organisms that break down complex materials in dead organism into simple ones
What is a producer?
Photosynthetic organisms that manufacture organic substances using light, water CO2, and mineral ions
What is a food chain?
A feeding relationship in which producers are eaten by primary consumers, who are eaten by secondary consumers, and who are eaten by tertiary consumers
How do plants use photosynthesised sugars?
Respiration
Synthesis other biological molecules
What is biomass?
The total dry mass of tissue or mass of carbon (without varying amounts of water) measured over a given time in a specific area
What are the units for biomass?
Kg m*-2
Why is dry mass used as a measure of biomass?
Because living tissue has a varying water content
How do you obtain dry mass?
Heat at 100 degrees in a furnace
Weigh at intervals
When mass constant = H2O removed
How can chemical energy store be calculated in dry biomass?
Energy (J) = specific heat capacity of H2O X vol of H2O X temp increase
Why is bomb calorimetry preferred over simple calorimetry?
Reduces heat loss to surroundings
What is calorimetry?
Process that estimates the amount of chemical energy stored in dry mass
How does calorimetry work?
Sample weighed and burnt in oxygen
Burning heats surrounding water
Temp change used to determine amount of energy
What is gross primary product (GPP)?
The total amount of chemical energy converted from light energy by plants, in a given area
What is net primary productivity (NPP)?
The total chemical energy available for pant growth, reproduction and energy transfer to other trophic levels after respiratory losses
What is the NPP equation for plants?
NPP = GPP - R
What is the net production equation for animals?
N = I - (F+R) I= chemical energy ingested from food F= energy lost as faeces + urine R= respiratory losses
What are respiratory losses?
50% of the GPP that is lost to the environment as heat when plants respire
How is energy lost in food chains?
Not all of organism eaten
Not all digested
Some lost as excretory materials
Heat loss to environment
Why is most of the sun’s energy not converted to organic matter?
Reflected back into space
Can’t absorb some wavelengths of light
Not all falls directly on chlorophyll molecule
Energy lost as heat during respiration
How do farming practices increase efficiency of energy transfer?
Reduce energy loss to other organisms
Reduce energy loss through respiration
What are some common farming practices?
Excluding predators
Artificial heating
Restricted movement
Feeding controlled
Why do farmers try to simplify the food web?
Gets rid of food chains that don’t involve humans - eg. pests
Energy losses reduced
NPP of crop will increase
Why do farmers use pesticides?
Kills pests that damage crops
Less biomass lost from crops so they grow larger = NPP greater
Why do farmers use herbicides?
Kills weeds = removes direct competition with crop for energy
Also removes habitat/food source for pests = further reduced numbers + simplified food web
How do farmers reduce respiratory losses?
Restricted movement
Pen indoor + kept warm
Means more biomass produced + more chemical energy can be stored
Increases NP + efficiency of energy transfer to humans
Why is the length of food chains limited?
Energy lost at each trophic level
So insufficient energy to support higher trophic levels
What are the general stages in the phosphorus cycle?
Weathering Runoff Assimilation Decomposition Uplift
Why is the phosphorus cycle slow?
No gas phase so no atmosphere cycle
Most stores as PO4*3- in rocks
Describe the phosphorus cycle
Rocks weathered
Ions taken in via plant root
Mycorrihazae increase rate of assimilation
Ions transferred through food chain
Ions lost in animal + plant waste
When they die decomposed by saprobionts
Ions released into soil for assimilation by plants
Describe uplift in the phosphorus cycle
Weathered rocks release ions into water Taken up by aquatic producers (algae) Passed along to birds in food chain Guano (sea bird waste) contains PO4*3- Returned back to soil
How does mining affect the phosphorus cycle?
Speeds up uplift
What is the significance of nitrogen to living organisms?
Amino acids
Proteins
NAD/NADP
What are the 4 main stages of the nitrogen cycle?
Nitrogen fixation
Ammonification
Nitrification
Denitrification
Why can’t organisms use nitrogen directly from the atmosphere?
N2 very stable due to strong covalent triple bond
So need bacteria to convert it into nitrogen-containing compounds
What is the role of mycorrhizae?
Mutalistic relationship between pant and fungus Increase SA of root Increases uptake of H2O + mineral ions Drought resistance Fungus gains amino acids + glucose
What happens in nitrogen-fixation?
Nitrogen gas is turned into nitrogen-containing compounds by bacteria
Use the enzyme nitrogenase to reduce gaseous nitrogen into NH3
What is the bacteria in nitrogen-fixation?
Rhizobium in root noodles of legumes
Form mutalistic relationship with plant
What happens in ammonification?
Saprobionts feed on + decompose organic waste containing N2
Forms NH4*+
What happens in nitrification?
NH4*+ changed back to nitrogen-containing compounds
Nitrites are oxidised to nitrates by nitrifying-bacteria
What happens in denitrification?
Anaerobic denitrifying bacteria converts soil nitrates back into gaseous nitrogen
What are the two types of fertilisers?
Natural (organic)
Artificial (inorganic)
What is the difference between natural and artificial fertilisers?
Natural - decaying organic matter + animal waste
Artificial - pure chemicals mined from rocks converted into pellets or powder
What are the 2 main environmental issues caused by fertilisers?
Leaching - nitrates dissolved in rainwater + “runoff” into water
Eutrophication - water source becomes putrid
At a certain point, using fertilisers don’t increase crop yield. Why?
Limiting factor limits rate of photosynthesis so rate of growth can’t increase anymore
How can the risk of eutrophication be reduced?
Sewage treatment marshes on farms
Pumping nutrient-enriched sediment out of water
Using phosphate-free detergent
Describe the process of eutrophication
Mineral ions leached into ponds/lakes Algae bloom grows + blocks light Plants die as unable to photosynthesise Saprobionts feed on dead matter + reduce O2 Dish die due to lack of O2 Water becomes putrid from toxic waste
What are the pros of intensive farming?
Efficient energy cost
Low cost
Safety/easier to control
Uses less land
What are the cons of intensive farming?
Disease Use of drugs - antibiotic resistance Animal welfare Reduction in genetic diversity Pollution - lots of waste Use of fossil fuels
What is a mutalistic relationship?
The way 2 organisms of different species exist in a relationship in which each individual benefits from the activity of the other
What is a food web?
Many food chains linked together, and are very complex
What is a trophic level?
Each stage in a food chain, occupied by a producer or consumer
What is a secondary consumer?
Those that eat a primary consumer
What is a tertiary consumer?
Those that eat secondary consumers
