The carbon and nitrogen cycles, why materials are reused in nature, and the benefits and difficulties of recycling manufactured materials.
6 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
The carbon atoms in your body were once in the air — maybe even in a dinosaur. How?
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Copy these into your notebook in your own words — that is how they stick.
Photosynthesis removes CO₂; feeding passes carbon along; respiration, decomposition and combustion return CO₂.
Nitrogen fixation (Rhizobium, lightning) → nitrates → plant proteins → animals → decomposition → ammonium → nitrification → nitrates; denitrification returns N₂.
Part of all organic molecules — carbohydrates, proteins, fats, DNA.
Use less; use again; reprocess into new products.
Conserves finite resources and energy; less landfill; less pollution; creates jobs.
Collection and sorting costs; contamination; small volumes; shipping; lack of public participation; toxic components.
The kind of support a teacher gives after the lesson: worked examples to attempt first, a board illustration, key terms, common misconceptions and memory aids.
Try it in your notebook first, then reveal the solution one step at a time.
Try it in your notebook first, then reveal the solution one step at a time.
| Process | Done by | Change |
|---|---|---|
| Nitrogen fixation | Rhizobium in root nodules; free-living soil bacteria; lightning; the Haber process | N₂ gas → nitrogen compounds (ammonium, nitrates) |
| Absorption and assimilation | Plant roots | Nitrates → plant protein |
| Feeding | Animals | Plant protein → animal protein |
| Decomposition (ammonification) | Putrefying bacteria and fungi | Proteins and urea → ammonium |
| Nitrification | Nitrosomonas, then Nitrobacter (need oxygen) | Ammonium → nitrite → nitrate |
| Denitrification | Denitrifying bacteria (no oxygen) | Nitrate → N₂ gas |
Learn the cycle as a set of processes, each with its own organisms and its own change.
In nitrification, “-ite” comes before “-ate”: you bite before you have ate — ammonium → nitrite → nitrate.
Barbados has long run a deposit-refund scheme on beverage containers, and several Caribbean countries have banned single-use plastic bags or foam food boxes to reduce waste going to landfills and the sea.
For one day, sort your household’s waste into food, paper, plastic, glass and metal. Which items could be composted, reused or recycled? Make a simple bar chart.
3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness.
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better.
Write full answers, then reveal the mark scheme and tick the points you earned (15 marks in total). Your answers are saved on this device.
Question 1 [9 marks]
This question is about recycling in nature and in society.
(a) Name the processes that (i) remove CO₂ from the air, (ii) return CO₂ from animals, (iii) release CO₂ from fossil fuels. [3]
(b) State ONE reason why carbon is important to living things. [1]
(c) Define reuse, reduce and recycle. [3]
(d) Suggest TWO advantages of recycling metals from old cellphones. [2]
Question 2 [6 marks]
Compare recycling cellphones and leftover food.
(a) Explain TWO ways in which recycling cellphones differs from recycling leftover food. [4]
(b) Suggest TWO ways recycling a tree after it is cut down can benefit a community. [2]
Find these in your own past-paper booklets for extra timed practice. The practice above is adapted from them.