B13 - Energy and ecosystems Flashcards
What is a trophic level?
Trophic levels describe the position of an organism in a food chain, web or pyramid
What is biomass?
The biomass of an organism is:
- The mass of living material of the organism or tissue
- The chemical energy that is stored within the organism or tissue
How is biomass measured?
It can be measured in terms of the dry mass of an organism or tissue which is the mass of the organisms or tissues after all the water has been removed.
Or the mass of carbon that an organism or tissue contains which can be measured through calorimetry which is used to estimate the chemical energy stored in dry biomass
What is gross primary production?
Gross primary production (GPP) is the amount of chemical energy stored in carbohydrates within plants
What is gross primary productivity?
Gross primary productivity (GPP) is the rate at which plants are able to store chemical energy via photosynthesis
What is net primary production and how is it calculated?
Net primary production (NPP) refers to the amount of energy available to herbivores in the plant’s biomass after plant respiratory losses.
NPP = GPP (gross primary production) - R (respiratory losses)
How is the net production for consumers calculated?
Net production for consumers = I - (F + R)
I is the chemical energy store in ingested food
F is the chemical energy lost to the environment in faeces and urine
R is the respiratory losses to the environment
What farming practices can increase the efficiency of energy transfer in order to increase the total amount of energy available for human consumption?
- Reducing the energy lost by crops to other organisms (e.g. pest species that feed on crops)
- Reducing the energy lost by livestock (e.g. cattle) through respiration
- Chemical pesticides (Insecticides & herbicides)
- Biological agents (e.g., ladybugs, which eat aphids…)
How can energy loss from respiration be reduced?
- They can be kept livestock in pens → movement is restricted → less energy lost through respiration
- Keep livestock indoors and in heated pens → reduces respiration rate needed to maintain a body temperature
These practice ensure more chemical energy is stored as biomass and not lost to respiration which increases the net production. However there are ethical concerns
How to decomposers break down dead plant & animal materials to gain the chemical energy?
By secreting digestive enzymes onto the surface of the dead organism → enzymes break down the dead matter into small soluble food molecules → molecules are then absorbed by the decomposers
What is the role of Saprobionts?
Mainly made of bacteria and fungi
Secrete enzymes onto their food → digested externally → Saprobionts absorb the products
Their digestion also releases a lot of useful products -e.g., mineral ions like ammonium or phosphate ions → can be reused by producers
Without these organisms, nutrients in decaying & waste matter would not be available again
What is the role of mycorrihaze?
Plant root + Fungi = Mycorrhizae
Often in symbiotic with plants
Their hyphae interact with plant roots, increase their surface area for the increased uptake of water and mineral ions
Receive organic compounds from the plant, in return
What happens in the first step of the nitrogen cycle (Nitrogen fixation) ?
Atmospheric nitrogen gas (N2) is converted into nitrogen-containing compounds. These compounds can be used by plants. These bacteria are found in root nodules and have a symbiotic relationship with plants
What happens in the second step of the nitrogen cycle (Ammonification) ?
Nitrogen compounds in waste products and dead organisms are converted into ammonia by Saprobionts - a decomposer. The ammonia form ammonium ions in the soil
What happens in the third step of the nitrogen cycle (Nitrification) ?
Ammonium ions in the soil are converted into nitrates by nitrifying bacteria→ nitrates used by plants & denitrifying bacteria
