Energy flow, pyramids and cyclesIB MYP Sciences: Flashcards
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What is the original source of energy for most food chains?
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- What is the original source of energy for most food chains?
- The Sun.
- Roughly what percentage of energy is passed on at each trophic level?
- About 10 %.
- Name two ways energy is lost between trophic levels.
- Any two of: heat from respiration, movement, waste, uneaten parts.
- Why are food chains short?
- So much energy is lost at each step that little is left after four or five levels.
- What is biomass?
- The mass of living material, measured as dry mass.
- Why is a pyramid of biomass more reliable than a pyramid of numbers?
- Biomass nearly always falls at each level, whereas numbers can give a strange shape, such as one tree supporting many insects.
- Which process removes carbon dioxide from the air?
- Photosynthesis.
- Name three ways carbon dioxide is returned to the air.
- Respiration, decomposition and combustion.
- What are fossil fuels and why do they add carbon dioxide?
- Fuels formed from ancient organisms; burning them releases carbon locked away for millions of years.
- Name the main stages of the water cycle.
- Evaporation, condensation, precipitation and run-off.
- What is transpiration?
- Loss of water vapour from the leaves of plants.
- What do decomposers do for plants?
- They release nutrients from dead material into the soil, so plants can take them up again.
- A producer receives 2000 kJ. How much reaches the secondary consumer at 10 % efficiency?
- 20 kJ (200 kJ to the primary consumer, then 20 kJ).
Exam questions on Energy flow, pyramids and cycles
- In a lake in Uganda, the algae capture 5000 kJ of energy per square metre each year. Tiny animals called zooplankton eat the algae, and small fish eat the zooplankton.Assume that 10 % of the energy is passed on at each trophic level. Calculate the energy available to the small fish per square metre each year.2 marks
- A tree in a tropical forest in Costa Rica takes in carbon for decades as it grows. Eventually it dies and falls to the forest floor. Elsewhere in the world, the remains of ancient forests were buried millions of years ago and slowly turned into coal. Some of that coal is now burned in a power station.Describe how the carbon in the dead tree on the forest floor returns to the atmosphere.2 marks
- An ecology class in Otago, New Zealand, studies a pasture. They collect all the organisms from several areas of 1 m², dry them and find the mean dry mass (biomass) per square metre. They find 1200 g of grass, 90 g of grasshoppers and 8 g of frogs. The grasshoppers eat the grass and the frogs eat the grasshoppers. The class wants to use the results to show how biomass changes along the food chain.Calculate the percentage of the biomass of the grass that is found in the grasshoppers, and the percentage of the biomass of the grasshoppers that is found in the frogs. Comment on your answers.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).