Use of biological resources flashcards

Topic 5: Use of biological resources

How do glasshouses increase crop yield?

They let light in and trap heat, protect crops from frost, wind and some pests, and allow control of temperature, CO₂ and water. Burning paraffin or gas supplies both heat and CO₂.

Why does adding more CO₂ to a glasshouse eventually stop increasing yield?

Another factor, such as light intensity or temperature, becomes limiting. Too high a temperature also denatures photosynthesis enzymes.

Pesticides vs biological control

Pesticides: fast and kill most pests, but kill non-target species, build up along food chains, and pests become resistant. Biological control: specific, no residues, no resistance, but slow, does not remove all pests, and the control organism may become a pest.

How does yeast make bread rise?

Yeast respires anaerobically: glucose → ethanol + carbon dioxide. Bubbles of CO₂ make the dough rise. Baking kills the yeast and evaporates the ethanol.

Making yoghurt

Pasteurise milk to kill unwanted bacteria and cool it; add Lactobacillus; incubate warm. The bacteria ferment lactose to lactic acid; the pH falls, milk proteins clot and the yoghurt thickens and tastes sour.

Conditions controlled in an industrial fermenter, and why

Aseptic (steam, filtered air): no contaminants. Nutrients: for respiration and growth. Temperature (water jacket): respiration releases heat; keep enzymes at the optimum. pH: optimum for enzymes. Oxygen: aerobic respiration. Paddles: mix evenly.

How are fish farms managed to increase yield?

Keep water quality and oxygen high; separate fish by size (intraspecific predation) and keep one species (interspecific predation); control disease and density; remove waste; high-protein food little and often; selective breeding. (Paper 2 only)

Selective breeding: the steps

Choose parents with the desired characteristic; cross them; select the offspring showing it most strongly; cross these; repeat for many generations.

Transgenic

Genetic material has been transferred from one species to a different species.

Restriction enzyme, ligase and vector

Restriction enzyme: cuts DNA at a specific base sequence, leaving sticky ends. Ligase: joins pieces of DNA. Vector: a plasmid or virus that carries DNA into a cell.

Producing human insulin with bacteria

Cut the insulin gene out with a restriction enzyme; cut a plasmid with the same enzyme (matching sticky ends); join with ligase to make recombinant DNA; insert into bacteria; grow them in a fermenter; extract and purify the insulin.

Cloning Dolly the sheep: which sheep is the clone identical to?

A diploid body-cell nucleus from sheep A goes into an egg from sheep B whose nucleus was removed; an electric shock makes it divide; the embryo is implanted in surrogate C. The lamb is a clone of sheep A, the nucleus donor. (Paper 2 only)