levo

Ecosystems

Ecosystem structure, energy flow and productivity

  • 3 things to know
  • A2 Unit 4

Overview

Trophic level, pyramid of energy and gross primary productivity.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

Define a trophic level.

Key term

Name the trophic levels of a simple food chain.

Numbers

Roughly what proportion of energy is transferred between trophic levels?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define a trophic level.

    Model answer

    A trophic level is a position in a food chain, defined by how many steps an organism is from the original source of energy.

  2. 2

    Name the trophic levels of a simple food chain.

    Model answer

    Producers, primary consumers, secondary consumers and tertiary consumers, with decomposers acting on every level.

  3. 3

    Roughly what proportion of energy is transferred between trophic levels?

    Model answer

    About 10%, the rest being lost as heat through respiration and in material that is not eaten or not digested.

  4. 4

    Explain why food chains rarely have more than four or five levels.

    Model answer

    So little energy remains after successive transfers that a further level could not support a viable population.

  5. 5

    What is a pyramid of energy?

    Model answer

    A pyramid of energy shows the amount of energy passing through each trophic level in a given time, and it always narrows upwards.

  6. 6

    Define gross primary productivity.

    Model answer

    Gross primary productivity is the total rate at which producers convert light energy into chemical energy through photosynthesis.

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book
2Open book
3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Coastal Landscapes
Glaciated Landscapes
Tectonic Hazards
Changing Places

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

Governments must win votes.
ruralurbanelite

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AFew coastal people recognised the signs.
BThe coasts were densely populated.
CMany communities were struck with no notice at all.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

The Mariana Trench reaches almost 11,000 m below sea level.
TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Ecosystems, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Or £46 a year, about £3.83 a month. Cancel anytime.