Energy and Ecosystems Flashcards
What is a producer?
A photosynthetic organism that manufactures organic substances using light energy
What is a consumer?
An organism which obtains its energy by feeding on other organisms
What is a primary consumer?
An organism which eats green plants
What is a secondary consumer?
An organism which eats primary consumers
What is a saprobiont?
A decomposed which breaks down complex material of dead organisms into simple ones to be reused
Which organisms work as sapropbionts?
Fungi and bacteria
What is a food chain?
A description of the relationship between producers and consumers
What are the stages of a food chain called?
Trophic levels
What is a food web?
The many chains within a habitat which are interlinked. Shows how an organism may eat or be eaten
What is biomass?
Total mass of living material in a specific area at a given time
Why is fresh biomass not a reliable amount?
Volume of water can vary
What is the measurement of dry biomass?
Dry mass per given area per given time.
How is biomass measured?
Sample is dried in an oven then weighed at regular intervals until the mass is constant
How is the energy stored in biomass estimated?
Calorimeter
How much energy from the sun is typically converted into organic matter?
1-3%
Most of the suns energy is not converted to biomass, why?
- Light wrong wavelength
- Light misses the chlorophyll
- Factor other than light intensity limiting photosynthesis
What is gross primary production?
Total amount of energy converted by plants in a given area at a given time
What is net primary production?
NPP= GPP-R
Why is consumption so insufficient?
Energy is lost as:
- Not all of the organism is consumed
- Lost as faeces
- Lost in excretionary materials
- Energy is lost during respiration as heat
What is the net production in consumers?
N=i-(f+r)
Why is the total mass of organisms in a particular place less at higher trophic levels?
Inefficiency of energy transfer between organisms. Less energy is available for those at higher trophic levels
What is the efficiency of energy transfer?
Net production at a trophic level divided by the net production in the previous trophic level X 100
What is productivity?
Amount of energy available to an organism
Why do organisms require nitrogen?
For protein, nuclei acids
In what form do plants absorb nitrogen?
Nitrate ions
How are nitrate ions absorbed by plants?
Active transport into the roots
How are nitrate replaced in the environment?
The break down of nitrogen containing compounds by decomposers
How are nitrates replaced artificially?
Fertilisers
What are the four stages of the nitrogen cycle?
- Ammonification
- Nitrification
- Nitrogen fixation
- Denitrification
What happens in ammonification?
Ammonia in the soil is converted to ammonium ions
What happens in nitrification?
Bacteria oxidise ammonium ions into nitrite ions and a different bacteria creates nitrate ions
What happens in nitrogen fixation?
Nitrogen gas is converted to nitrogen containing compounds by bacteria
Where are the nitrogen fixing bacteria found?
Free living or mutualistic ( in the root nodules of plants)
What do free living nitrogen fixing bacteria fo?
Reduce nitrogen gas to ammonia which are used to create amino acids released when they die
What do mutualistic bacteria do?
Rescue nitrogen gas into ammonia which create amino acids given to plants so they receive carbohydrates in return
What happens in denitrification?
Anaerobic denitrifying bacteria convert nitrates to nitrogen gas
What are the benefits of ploughing?>
Increases air space, supports aerobic respiration of bacteria
What biological molecules contain phosphorus?
ATP, Phospholipids, and nuclei acids
How is phosphorus general found in nature?
As phosphate ions in sedimentary rock
How are phosphates removed from rocks
Weathering and erosion
How are phosphates incorporated into the food chain?>
Dissolved phosphates are absorbed into plants
How do phosphate ions find their way into animas?
Some animals eat plants and so ingest the phosphate containing molecules
How are phosphate ions released from animals?
Excretion
How are phosphates removed from living organisms?
Upon death, decomposers break down the organism, releasing soluble phosphates which flow into bodies of water
What are mycorrhizae?
Mutualistic fungi’s that live on the roots of plants. Help with the uptake of nitrogen and phosphates whilst receiving carbohydrates in return.
How do mycorrhizae aid absorption of nutrients?
Act as extensions of the roots, increasing surface area for absorption. Also act as a sponge to hold nutrient rich water closer to the roots
What are the two types of fertilisers?
Natural and artificial
Why aren’t fertilisers required in nature?
Plants that remove the mineral ions return them when they are decomposed
Why is it important to replenish the mineral ions in the soil?
They will become a limiting factor in photosynthesis if too low
Why is it important that fertilisers are given in appropriate quantities?
There is a limit. Past a certain point they don’t add to the effectiveness
How do fertilisers increase productivity?
Mineral ions readily available
What are the effects of nitrogen containing fertilisers?
Increase area of leaves therefore increasing rate of photosynthesis and crop productivity
What are the drawbacks of nitrogen containing fertilisers? `
Reduced species diversity, leaching and eutrophication
Why does the use of nitrogen rich fertilisers affect species diversity?
Nitrogen rich soil favours fast growing species which outcompete other species
What is leaching?
Process by which nutrients are washed out of the soil
How are minerals leached from the soil?
Rainwater carries dissolved nutrients deep into the soil away from plant roots. This makes it into water ways and lakes
Why is leaching dangerous to humans?
If the water source is a drinking source it has been linked to stomach cancer and insufficient oxygen transport in babies. Also causes eutrophication.
What happens in eutrophication?
As the nitrate ion concentration increases due to leaching, it no longer is a limiting factor so plant and algae populations will grow. As algae is at the surface, it blocks light from lower depths so light is now a limiting factor. Saprobiontic bacteria population will grow as dead organic material ceases to be a limiting factor and this bacteria requires oxygen so the oxygen concentration decreases becoming a limiting factor for aerobic organisms.
