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USS · Paper II

Biology

Cells, plant and animal life, nutrition, respiration, and the body.

7 of the 50 questionsWrite this topic →
What the paper asks

Seven questions. Cells, plant life, the human body, nutrition and disease. Deficiency diseases and 'which organ does what' are asked almost every year, and the wrong options are usually true statements about a different organ.

Cells and what is inside them
  • The cell is the basic structural and functional unit of life. Cells → tissues → organs → organ systems.
  • Chloroplast — photosynthesis. Contains chlorophyll. Plant cells only.
  • Mitochondria — release energy from food. The opposite process to photosynthesis.
  • Nucleus — controls the cell.
  • Plant cells also have a cell wall and a large vacuole; animal cells have neither.
Photosynthesis and respiration
PhotosynthesisRespiration
Takes incarbon dioxide + wateroxygen + food
Gives outglucose + oxygencarbon dioxide + water
Energystoredreleased
Whenin sunlightall the time
Wherechloroplastmitochondria
Plants — transport and reproduction
  • Xylem carries water and minerals up from the roots. Phloem carries food made in the leaves to the rest of the plant.
  • Root hairs absorb water — a huge surface area in a small space.
  • Stomata are pores on the leaf for gas exchange; water vapour also escapes through them (transpiration).
  • Pollination is the transfer of pollen from anther to stigma; fertilisation is what happens afterwards.
  • Vegetative propagation — a new plant from a part of the parent, with no seed.
  • Legumes (peas, beans) host Rhizobium in root nodules and fix nitrogen, which is why they are used in crop rotation.
The human body — organ by job
JobOrgan
Pumps bloodHeart — four chambers
Gas exchangeLungs
Filters waste from bloodKidney
Largest organSkin
Largest internal organLiver
Produces insulinPancreas
Starch digestion beginsMouth — saliva
Protein digestion beginsStomach
Blood, and deficiency diseases
  • Red cells carry oxygen using haemoglobin, which contains iron. White cells fight infection. Platelets clot.
  • A shortage of iron causes anaemia.
MissingDisease
Vitamin Anight blindness
Vitamin B1beriberi
Vitamin Cscurvy
Vitamin Drickets — weak, soft bones
Ironanaemia
Iodinegoitre
Proteinkwashiorkor
Microbes, disease and food chains
  • Not every microbe is harmful. Lactobacillus turns milk into curd; yeast is used in bread.
  • Malaria — the female Anopheles mosquito carries the Plasmodium parasite. Only the female bites.
  • Food chain: producers (green plants) → consumers → decomposers.
  • Vertebrates have a backbone — fish, amphibians, reptiles, birds, mammals. Earthworms, insects and jellyfish do not.
  • Mammals feed their young on milk — including whales and bats, which is where the paper sets its trap.
Worked through

Why is a whale a mammal and a shark a fish?

  1. A whale feeds its young on milk and breathes air through lungs.
  2. A shark has gills and does not feed young on milk.
  3. Living in the sea and having a similar shape is not what decides the group.

Which disease is caused by a deficiency rather than a germ: malaria, typhoid, scurvy, cholera?

  1. Malaria comes from a parasite, typhoid and cholera from bacteria.
  2. Scurvy comes from a lack of vitamin C — nothing enters the body to cause it.
Where the marks go

These are the mistakes, not the rules — each one is something a student who knows the topic still does under time pressure.

  1. Naming the liver as the largest organ. It is the largest internal one; the skin is the largest overall.
  2. Saying digestion starts in the stomach. Starch digestion starts in the mouth.
  3. Swapping xylem and phloem. Xylem up with water, phloem out with food.
  4. Choosing mitochondria for photosynthesis. Chloroplast stores energy; mitochondria release it.
  5. Grouping a whale with sharks, or a penguin with mammals.
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Sit 10 questions on this topic

Read the explanation on every one you get wrong — that is where the revision above actually sticks.

 Or the whole paper

Sit Paper II against the clock

Fifty questions in ninety minutes, drawn to the real subject mix. The scorecard will tell you what to revise next.

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