Energy and ecosystems Flashcards
What is the source of energy for ecosystems
sunlight
How do plants use sunlight to produce energy
By photosynthesis, they use sunlight in producing organic compounds such as glucose
Biomass
total mass of living material in a specific area at a given time
producers
photosynthetic organisms that manufacture organic substances using light energy, water and carbon dioxide
consumers
organisms that obtain their energy by feeding on other consumers rather than using the energy of sunlight directly
What organisms are consumers
Animals
Primary consumers
Those that directly eat producers- first in the chain of consumers
Secondary consumers
Animals that eat primary consumers
Tertiary consumers
Animals that eat secondary consumers
Saprobiants
a group of organisms that break down the complex materials in dead organisms into simple ones. In doing so they release valuable minerals and elements in a form that can be absorbed by plants and contribute to recycling
Food chain
describes a feeding relationship in which the producers are eaten by the primary consumers. These in turn are eaten by secondary consumers and in turn tertiary consumers.
Trophic level
Each stage in a food chain
what do the arrows in a food web/chain show
direction of energy flow
Food webs
most animals do not rely on a single food source and within a single habitat many food chains will be linked together to form a food web
how is biomass measured
using dry mass per given area in a given time
Calorimetry
a sample of dry material is weighed and is then burnt in pure oxygen within a sealed chamber called a bomb. The bomb is surrounded by a water bath and the heat of combustion
How much of the sun’s energy is converted by plants into organic matter
1-3%
Why is most of the sun’s energy not converted into organic matter
-90% of the suns energy is reflected back into space by clouds or absorbed by the atmosphere
-not all wavelengths of light can be absorbed and used for photosynthesis
-light may not fall on chlorophyll molecule
-a factor such as low carbon dioxide levels might affect the rate
Gross primary production (GPP)
The total quantity of the chemical energy store in plant biomass in a given area or volume in given time
How much GPP is used in respiration
20-50%
net primary productivity (NPP)
The chemical energy store that is left when the losses to respiration have been taken into account
What is NPP available for
plant growth and reproduction
How much NPP is used by primary consumers
10%
How much NPP is used by secondary and tertiary consumers
20%
What is the reason for a low % of NPP being transferred
-some of the organism is not consumed
-some parts can be consumed but not digested (faeces)
-some energy is lost in excretory materials (urine)
-energy lost as heat from respiration
How is net production of consumers calculated
N=I-(F+R)
What does the inefficiency of energy transfer between trophic levels explain
-most food chain only have 4 or 5 trophic levels because insufficient energy is available to support a large enough breeding population
-the total mass of organisms in a particular place is less at higher trophic levels
-the total amount of energy available is less at each level as one moves up the food chain
Summarise the common features of all nutrient cycles
- Nutrient taken up by producers as simple inorganic molecules
- Producer incorporates nutrient into complex organic molecules
- Nutrient passed on to consumers when producer is eaten
- Nutrient passed along food chain to other consumers
- When organisms die the complex molecules are broken down by saprobiontic microorganisms (decomposers) and nutrient is released in it’s original simple form to be recycled
Describe the features of the nitrogen cycle
-Living organisms required source of nitrogen to manufacture proteins and nucleic acids, most are unable to access the nitrogen from the atmosphere.
-Plants obtain nitrogen by active transport from nitrate ions in the soil
-Animals obtain nitrogen containing compounds by consuming other organisms
-Microbes return nitrate ions to the soil through decomposition
process of the nitrogen cycle
-few organisms can convert nitrogen gas into compounds useful to other organisms in a process known as nitrogen fixation
-These organisms can be free-living or live in a relationship with certain plants
-Most plants obtain their nitrogen by absorbing nitrates from the soil through their root hairs by active transport.
-They then convert this to proteins which is passed to animals when they eat the plant
-On death, sabrobiants break down these organisms releasing ammonium which can then be oxidised to form nitrite ions by nitrifying bacteria.
Further oxidation by the same type of bacteria forms nitrate ions.
-These ions may be converted back to atmospheric nitrogen by the activities of dentrifying bacteria.
Ammonification
Ammonification: production of ammonia from organic nitrogen containing comounds by sapprobiontic organisms.
Nitrification
Nitrification: nitrifying bacteria carry out oxidation reactions to convert ammonium ions into nitrites and then nitrates
Nitrogen fixation
Nitrogen Fixation: nitrogen gas is converted into nitrogen containing compounds in a variety of ways. Haber process, lightening, by nitrogen fixing bacteria. There are two type of nitrogen fixing bacteria: free living bacteria which convert nitrogen gas into ammonia. Mutualistic nitrogen fixing bacteria live in the root nodules of legumes and obtain carbohydrates from the plant whilst providing a supply of amino acids they have fixed from nitrogen gas.
Denitrification
Denitrification: anaerobic denitrifying bacteria reside in waterlogged soil and convert nitrates into gaseous nitrogen
Describe the features of the phosphorous cycle
Phosphorus stored in phosphate ions in sedimentary rock
Weathering and erosion of phosphate in rock, ions dissolved in water
Phosphate ions taken up by plant roots and incorporated into biological molecules
Feeding and digestion by consumers
Phosphate ions in animal waste and remains of animals
Decomposition by saprobionts
Washed back into the sea and incorporated into sedimentary rock
Explain the roles of saprobiontic organisms in nutrient recycling
Saprobiontic organisms (decomposers) break down complex molecules in consumers and producers when they die and release the nutrient in its original simple to be taken up by producers
Why are fertilisers needed
crops are grown repeatedly and intensely on the same area of land and minerals are not returned to the same area of land so can limit the rate of photosynthesis. fertilisers added to the soil to replace the nitrate and phosphate ions lost when plants are harvested to remain productivity.
natural ferilisers
consist of the dead and decaying remains of plants and animals (manure)
strengths of natural fertilisers
they are cheaper because farmers have access to animals
limitations of natural fertilisers
the exact minerals in them cannot be controlled
artificial fertilisers
inorganic chemicals made from the elements nitrogen, phosphorus and potassium
strengths of artificial fertilisers
-created to contain exact proportions
-water soluble so they’re easy to absorb
limitations of artificial fertilisers
-as they’re water soluble more dissolve in the water surrounding the soil so larger quantities are washed away and therefore have a greater effect on the environment
What does research suggest about fertilisers
a combination of natural and artificial fertilisers gives the greatest long-term increase in productivity. However it’s important that minerals are added in appropriate quantities as there is a point at which further increases in the quantity of fertiliser no longer results in increased productivity
suggest a reason why after a certain point the addition of more fertiliser no longer improves the productivity of crops
another factor is limiting photosynthesis such as light or CO2 so only the addition of this factor will increase photosynthesis and hence productivity
How do fertilisers increase productivity
Plants require minerals to grow such as nitrogen which is an essential component of amino acids. Where nitrate ions are available plants are likely to develop earlier, grow taller and have a greater leaf area. This increases the rate of photosynthesis and improves crop productivity
What are the effects of nitrogen-containing fertilisers
-reduced species diversity- nitrogen rich soils favour the growth of grasses, nettles and other rapidly growing species which outcompete many other species
-leaching
-eutrophication
leaching
process by which nutrients are removed from the soil and water soluble compounds are washed away into the rivers or ponds. here they may have a harmful effect on humans if the river or lake is a source of drinking water
eutrophication
the process by which salts build up in bodies of water
process of eutrophication
-nitrates leached from fertilisers field stimulate growth of algae in ponds
-excessive growth of algae creates a blanket on the surface of water which blocks out light
-as result plants cannot photosynthesise and die
-bacteria within the water feed and respire on the dead plant matter
-results in an increase in bacteria which are all respiring and using up the oxygen within the water
