Chapter 13 - Energy and ecosystems Flashcards
What is the initial source of energy for most organisms?
Sunlight
How is energy passed between organisms?
Biomass
What are producers?
Photosynthetic organisms that manufacture organic substances using light, water, CO2 and minerals
What are consumers?
Organisms that get their energy from feeding on other organisms
What are primary consumers?
Consumers that eat producers
What are secondary consumers?
Those that consume primary consumers
What are saprobionts?
Organisms that break complex material in dead organisms down into simple molecules
What is a food chain?
A feeding relationship in which producers are eaten by primary consumers, they are eaten by secondary consumers, who are eaten by tertiary consumers
What is each stage in a food chain called?
A trophic level
What is a food web?
Many overlapping food chains
What is biomass?
The total mass of living material in a specific area at a given time
Why is it better to measure the dry mass?
The presence of water in an organism varies dependent on conditions
Describe the process of calorimetry
A sample of dry material is weighed and burned in pure oxygen. The ‘bomb’ is surrounded by a water bath and we measure the change in temperature of this water
Why is such a small percentage of the suns energy used in photosynthesis?
Reflected by clouds
Not all wavelengths of light can be used in photosynthesis
Light may not fall on chlorophyll
Limiting factors may reduce photosynthesis
What is gross primary production?
The total quantity of chemical energy stored in plant biomass at a given time
What is net primary production?
The chemical energy that remains when the loss of energy used in respiration has been accounted for
What is the equation for net primary production?
Net primary production = gross primary production - respiratory losses
Why is such a low percentage of energy transferred between trophic levels?
Not all of the organism is consumed
Some parts are consumed but can’t be digested so are lost in faeces
Urine
Heat is lost through respiration
Why are fertilisers needed especially in agricultural settings?
Normally, plants would die and decompose, returning their nutrients to the soil. In agriculture, the plants are removed before they can decompose so the nutrients must be returned in another way
What are natural fertilisers?
Consists of the dead and decaying parts of plants and animals
What are artificial fertilisers?
NPK fertilisers!
Mined from rocks and deposits and combined to produce the right ratio for the crop
How do fertilisers increase productivity?
Plants grow healthier and photosynthesise more
What is nitrogen used for?
DNA, amino acids, ATP
What are some of the detrimental effects of nitrogen fertilisers?
Leaching, eutrophication, reduced species diversity (nitrogen favoring species out-compete others so diversity decreases)
What is leaching?
The process by which nutrients are removed from the soil
Describe the process of leaching
Rainwater dissolved minerals and leaches it into water courses and drain into fresh water lakes. This can cause eutrophication and illness in humans if water is contaminated
Describe the process of eutrophication
In most lakes, nitrate ions act as a limiting factor for algal growth
Leaching increases the concentration of nitrate ions so they are no longer limiting
An algal bloom develops
This prevents light from reaching lower depths
Plants and algae at these depths die
Saprobionts break down dead plant matter
Saprobionts use up oxygen and release co2
Oxygen becomes limiting for aerobic respiration and so fish and plants die
There is less competition for anaerobic organisms who decay the material, turning the water putrid
Describe the phosphorus cycle
Phosphate ions in rocks are released by weathering
Plants absorb phosphorus through their roots
Mycorrhizae increase the rate of absorption
Phosphate ions are transferred through the food chain as organisms consume one another
Phosphate ions are lost from animals in waste products
When these animals and plants die, saprobionts break down complex material into the soil to be absorbed by plants
Weathering rocks releases phosphate into the water sources, which is taken up by aquatic producers
What is the role of mycorrhizae in the phosphorus cycle?
It forms a mutualistic relationship with plants - plants benefit from the increased uptake of phosphorus and the mycorrhizae benefit from organic materials from the plant
What is denitrification?
Nitrates in the soil are converted into nitrogen gas by denitrifying bacteria under anaerobic conditions
What is nitrogen fixation?
Nitrogen gas in the atmosphere is converted into nitrogen-containing compounds by bacteria
What are the two microorganisms involved in nitrogen fixation?
Free-living bacteria (Reduce nitrogen gas into ammonia, which they use to produce amino acids) Mutualistic bacteria (
What is nitrification?
Ammonia is oxidised to nitrite ions which are oxidised to nitrate ions
What is ammonification?
Saprobionts turn nitrogen compounds in dead organisms into ammonia
Why do nitrogen compounds easily leach through the soil?
They are very soluble
