Health and disease, Year 10: fungi, malaria and the immune system

fungus

提示The same group includes moulds and mildews.

为什么Rose black spot is the fungal disease named at GCSE. Because it is caused by a fungus, it can be treated with a fungicide, a chemical that kills fungi.

Purple or black spots develop, and the leaves often turn yellow and drop early

提示The name tells you half of it; then think about what happens to the whole leaf afterwards.

为什么The spots appear on the upper surface of the leaves. Badly affected leaves yellow and fall well before autumn, so a plant can lose much of its foliage in summer.

It carries out less photosynthesis

提示Count how many healthy green leaves the plant has left to work with.

为什么Spotted, yellowed and fallen leaves cannot absorb light and make glucose as a healthy leaf does. With less glucose, the plant has less energy and less material for making new growth and flowers.

water; wind

提示Think about what a rainy, blustery day does to the tiny spores made on an infected leaf.

为什么The fungus makes spores on the infected leaves. Rain splashes them onto other leaves, and moving air can carry them further. This is why the disease is worse in wet weather.

fungicide; destroying

提示One is a chemical; the other needs only a pair of secateurs and a bonfire or a bin.

为什么A fungicide kills the fungus on the plant. Affected leaves carry spores, so they are taken off and destroyed, not composted or left on the soil, where the spores could infect the plant again.

A vector

提示In maths and physics the same word means a quantity with a direction.

为什么For malaria the carrier is the mosquito. The mosquito does not cause the disease; it picks up the malarial protist when it feeds on an infected person and passes it on when it bites someone else.

protist

提示Members of this group are single-celled, and their cells have a nucleus.

为什么The malarial pathogen needs two hosts to complete its life cycle: the mosquito and a human. Breaking the cycle at the mosquito stage is the basis of malaria control.

It comes in recurrent episodes

提示Notice what happens over days and weeks, not just on the first day.

为什么The fever of malaria comes back again and again, and the disease can be fatal. That repeating pattern is what the word 'recurrent' describes.

Mosquitoes can no longer breed there

提示Ask where the carrier of the disease lays its eggs.

为什么Mosquitoes lay their eggs in still water. With fewer places to breed there are fewer mosquitoes, and so fewer chances for the malarial protist to be passed from person to person.

It stops mosquitoes biting them, so the pathogen cannot enter their blood

提示Think about the one moment at which the disease gets from the insect into a person.

为什么The malarial protist is passed on when an infected mosquito feeds on a person's blood. A net is a simple barrier between the sleeper and the insect; nets treated with insecticide also kill mosquitoes that land on them.

Hairs and mucus trap them

提示One part acts like a filter; the other is sticky.

为什么This is one of the body's non-specific defences: it works in the same way against any pathogen. The trapped particles are then swallowed or blown out, so they do not reach the lungs.

Mucus traps the pathogens and cilia sweep it up to the throat

提示A sticky layer catches them; then tiny hair-like structures on the lining act like a moving staircase.

为什么The lining of the airways makes mucus, which catches dust and microorganisms. Ciliated cells beat in rhythm to move the mucus upwards, away from the lungs, to be swallowed.

hydrochloric

提示It is the same acid found in most school laboratories, formula HCl.

为什么This acid makes the stomach contents strongly acidic. Most microorganisms taken in with food, or swallowed in mucus from the airways, cannot survive there.

Phagocytosis

提示The word starts with the Greek for 'to eat'.

为什么Some white blood cells surround a pathogen, take it in and destroy it. It is one of the three ways white blood cells defend the body, alongside making antibodies and making antitoxins.

antibodies; antitoxins

提示Both names begin with the same four letters, meaning 'against'.

为什么These are two different products. One targets the pathogen itself; the other deals with the poisons that make us feel ill. Together with phagocytosis they are the three roles of white blood cells that GCSE names.