What are zoonotic diseases and what does the destruction of rain forest have to do with it?

Image credit: David DennisFlickr: Bat in a Cave. CC BY-SA 2.0.

Ebola, HIV, rabies and the Corona virus. They all are caused by germs that can spread between animals and humans, also called zoonotic diseases.

HIV most likely originated from chimpanzees that were hunted and eaten for meat.  Similarly, Ebola is linked to the consumption of bush meat, especially bats.

The infamous Corona virus is thought to have jumped species first at a ”wet market” in Wuhan, China. Wet markets are traditional places that sell dead and live animals out in the open. These markets pose a good opportunity for a virus to jump species because hygiene standards are low and they are densely packed with people. However, the exact animal source of the Corona virus is still unknown. But bats are suspected to be involved here as well by infecting chicken, which was then consumed by humans. These winged mammals are often a source of zoonotic diseases because they live in large groups and travel far distances.

Normally, it is not that easy for a virus to jump from one species to another. When an organism gets infected a virus hijacks its cells to make copies of itself. To enter a cell, the virus has a key-like structure on its surface that will only let it into the cells of one single species. However, during the copying process mistakes are made and mutations occur in the key-like structures. With some luck for the virus one of these mutations will enable it to enter the cells of another species, for example humans. The virus has jumped species. This process is easier if hygiene standards are low and places are densely packed.

Research by scientists from the universities of Bonn and Ulm (Germany) also suggests that the destruction of ecosystems like rain forests may enable infections to jump species more easily. The researchers looked at ecosystems in Panama comparing undisturbed rain forest, smaller rain forest islands in the Panama Canal and small islands of rain forest within in an agricultural landscape.

Biodiversity is reduced in these small rain forest islands compared to intact rainforests. For example, there are fewer species of bats and rats. Therefore, individuals of the same species live closer together and are less dispersed. The results of the German research team showed that this also made it easier for different kinds of virus to spread within the populations of the remaining rats and bats giving these germs larger reservoirs. This could in turn make it easier for a virus to jump species and infect humans.

It is quite astonishing that the destruction of ecosystems could indeed influence our health by increasing the risk of zoonotic diseases like Ebola, HIV and the Corona virus.


Active reading exercise: How do muscles work?

Image: D. Keeno, 17 November 2017.

How do muscles work?

Muscles work by getting shorter. We say that they contract.

Muscles are attached to bones by strong tendons. When a muscle contracts, it pulls on the bone, and the bone can move if it is part of a joint.

Muscles can only pull, but not push. This would be a problem if a joint was controlled by just one muscle. As soon as the muscle had contracted and pulled on a bone, that would be it, with no way to move the bone back again. The problem is solved by having muscles in pairs, called antagonistic pairs.

To move the bone back the second muscle of the antagonistic pair contracts. Examples of antagonistic pairs are biceps and triceps.

How does your forearm move?

The elbow joint lets our forearm move up or down. It is controlled by two muscles, the biceps on the front of the upper arm, and the triceps on the back of the upper arm.

The biceps and the triceps are an antagonistic pair.

  • When the biceps muscle contracts, the forearm moves up.
  • When the triceps muscle contracts, the forearm moves down.This solves the problem. To lift the forearm, the biceps contracts and the triceps relaxes. To lower the forearm again, the triceps contracts and the biceps relaxes.


1. Box how muscles work.

2. Circle what attaches muscles to bones.

3. Underline what happens when muscles contract.

4. Underline why muscles need to work in antagonistic pairs.

5. Describe in your own words how antagonistic pairs work.

6. Explain in your own words how your forearm moves.

Reading exercise: Antibiotics and bacteria resistance

The following text is written for pupils with low reading ages to help them study the topic of antibiotics and bacteria resistance.

Before antibiotics

Think back to the last time you cut yourself. Can you imagine that cut becoming infected with bacteria – so seriously infected that you would die?

Before the discovery of antibiotics, there was nothing anybody could do. Bacteria could kill 80 percent of people with infected wounds.

Who would have thought a mouldy plate would lead to this?

In 1928, Alexander Fleming, a doctor at London’s St. Mary’s Hospital, found that a mould on a discarded plate had antibacterial properties. This mould was ‘penicillin’. Penicillin is an antibiotic.

Antibiotics kill bacteria and slow down their growth. A bacterium consists of one single cell and antibiotics disturb their cell functions. Antibiotics do not work against viruses because a virus consists of a DNA fragment instead of a cell.

Human life expectancy increased rapidly by eight years when antibiotics were first introduced in the 1930s.

Bacteria resistance

Within four years of penicillin being introduced onto the market, bacteria resistance was being reported. Bacteria resistance means that an antibiotic no longer kills the bacteria.

Today bacteria resistance against commonly used antibiotics is increasing rapidly around the world and a growing problem.

The Isolation and Detection of Starch – A Practical for Science Lessons

1 Goal

In this lab you will isolate starch from potatoes and investigate if different food samples contain starch. This is done with the help of Lugol’s solution (iodine/ potassium iodide solution).

2 Introduction

Starch is an organic compounds that belongs to the carbohydrates. Carbohydrates are an energy storage for both plants and animals. Starch molecules are very long and the building blocks repeat themselves. They form long chains and belong to the so-called poly saccharides. The two building blocks of starch are amylose which forms spiral chains and amylopectin which forms branched chains. Both are built up from glucose rests which is why the chemical formula can generally be written as (C6H10O5)n. Starch can be found, e.g. in root crops and grains.

The presence of starch can be detected with with the help of Lugol’s solution which is a mixture of iodine and potassium iodide dissolve din water. Potassium iodide is added to increase iodine’s solubility in water. Iodine molecules (I2) are stored in the spiral chains of amylose when Lugol’s solution (brown solution due to the iodine) is added to the starch. This storage compound (”iodine starch”) causes a blue-black colour. A schematic of the compound is shown to the right in the figure above.

3 Materials and Chemicals

  • Two Potatoes
  • Different other foods: Flour, bacon, cheese, apples, pasta and rice are recommended
  • Lugol’s solution (= iodine/potassium iodide solution)
    – Preparation: Dissolve 10 g potassium iodide in 100 ml of distilled water. Then slowly add 5 g iodine crystals, while shaking. Finally, lter and store in a tightly stoppered brown glass bottle.
  • Knife and Spoon
  • Several Test Tubes with Gummy Plugs
  • Mortar
  • One 250 ml-Beaker and one 800 ml- or 1000 ml-Beaker
  • Heating plate
  • Linen cloth
  • Funnel
  • Two Bowls
  • Grater

    4 Implementation

    4.1 The isolation of starch

    First, the potatoes need to be cleaned and peeled. Thereafter, they are grated and put into a bowl. 500 ml of water are added and the mixture is stirred thoroughly with a spoon for at least five minutes. A linen cloth is placed in a funnel and the mixture is pressed through into a large beaker (800 ml or 1000 ml). A part of the grated potatoes, for example the cellulose, will stay behind in the linen cloth. The liquid in the large beaker needs to stand and rest for approximately ve minutes. Then more water is added, approximately 100 – 200 ml. The finely dispersed, solid starch particles will slowly settle at the bottom of the beaker. Afterwards, the
    water is decanted (= poured off). Then 100-200 ml of water are added again to
    the large beaker and decanted when the solid starch particles have settled on the
    bottom a second time. This cleaning step is repeated until the starch particles have
    a completely white colour. Afterwards, the starch is dried in a at bowl in air and
    at room temperature.

    4.2 The detection of starch

    The foods are crushed in a mortar and and small amounts of each are put into their respective test tube. The test tubes are filled up to a third with water and shaken vigorously. In case not all the food particles are suspended, the test tubes are heated in a water bath (water bath = a 250 ml-beaker filled with water and the test tube inside is heated carefully on a heating plate, the test tube is afterwards cooled under owing, cold water). Then one drop of Lugol’s solution is added to each test tube and the test tubes are shaken with a gummy plug on top.

5 Questions for Discussion

1. What is observed macroscopically when iodine is built into starch molecules? What happens when no starch is present?

2. Which function does starch have?

3. In which foods do you expect to detect starch? In which foods should there be no starch?

4. Do the results in the table match your expectations? If not, why could they be different?


Image retrieved from: Petra Mischnick, Skolan för kemivetenskap , Kungliga Tekniska Högskolan, Stockholm, 11 January 2013 (https://www.kth.se/che/archive/arkiv/molnov-1.272910, 30 August 2017).

What is artificial photosynthesis?

Plants are truly amazing. To produce energy they basically ingest sunlight, water and carbon dioxide. As a result energy is chemically stored in sugars like glucose. (Scientists call them carbohydrates.) We all have heard about this process in school, photosynthesis. The carbohydrates can be further modified by the plants into fats or proteins. Animals like humans rely on all three as food, but also on the oxygen produced as a byproduct. In fact, there was no oxygen in the Earth atmosphere before the first cyanobacteria invented photosynthesis. These cyanobacteria later evolved into the chloroplasts inside plant cells where photosynthesis takes place.

Photosynthesis is very effective in transforming the energy of sunlight into chemical energy in sugars without creating any toxic or polluting waste. For this reason scientists today are trying to artificially create photosynthesis. The goal of these systems is to produce hydrogen or other fuels for engines and electricity. Another advantage would be that carbon dioxide released by the use of fossil fuels could be ”mopped up” from the atmosphere by artificial photosynthesis.

The main difference between artificial and natural photosynthesis is that plants produce carbohydrates, fats and proteins while humans are looking for suitable fuels that can power airplanes or cars. These fuels should ideally resemble fossil fuels and thus enable the use of already existing combustion motors. For this reason, chemists are trying to create different end-products than plants while using the same energy source (sun) and building blocks (carbon dioxide and water).

Plants use their chlorophyll to capture the sunlight while a collection of enzymes and proteins uses this energy to split water molecules into hydrogen, electrons and oxygen. Hydrogen and electrons then form carbohydrates (sugars) with the carbon dioxide and oxygen is released.

For artificial photosynthesis, scientists are mainly interested in the first two steps above. Capturing sunlight is the easy part, as there are plenty of solar-power systems available. Splitting water, however, is trickier and the main challenge. Water is a very stable compound and catalysts are required to initiate the splitting reaction. Catalysts are materials that can accelerate chemical reactions, without being depleted in the process. A great amount of research is being carried out  in order to find suitable catalysts for artificial photosynthesis. Among recently published very succesful catalysts were cobalt-based materials. Nevertheless, these systems still require more work and research in order to be optimized for commercialization.

Theoretically, the produced hydrogen could be directly used as a fuel. However, right now it is still more practical to transform hydrogen and carbon dioxide to fuels that closely resemble fossil fuels. This last step can be carried out either with the help of bacteria or other inorganic catalysts like copper. The conversion makes it possible to use the products of artificial photosynthesis in already existing car and airplane engines.

Maybe it will not take too long before we are able to drive cars with fuels directly produced with sunlight and carbon dioxide.

3 Ways You Can Save the Bees

Image: Bumblebee (probably Bombus terrestris) by Tony Wills. CC BY-SA 3.0.

It is a warm, sunny day in May here in Uppsala. When passing the meadows close to my house you can see busy butterflies and bumblebees collecting nectar from the flowers. Watching this scene, it is almost impossible to imagine that many insect species and especially bees are actually in serious trouble. Since 2006 bee keepers in the US and Europe have seen a decline in the numbers of honeybees that is growing more rapid. This phenomenon is called Colony Collapse Disorder (CCD) where adult worker bees disappear from their hives leaving behind the queen, the brood and nursing bees.

Now, you might say: ”I do not like honey anyway. Why should I care about the bees?” Well, bees are not only involved in the production of honey, but most edible plants you can find in your local supermarket. Most agricultural plants, i.e. fruit, seeds and nuts (see here for a complete list),  rely on the pollination by bees, most of all by honeybees. As a consequence, no bees means no food for humans either which is why we should care about the bees.

What happens when bees disappear completely, can already be seen in China. Bees have become extinct in some parts of the country. For this reason farmers have started to manually pollinate fruit trees themselves in order to save their crops and buisenesses.

There are different reasons for the mass extincition of bees that we see today. The main villains are modern agriculture; germs and parrasites, particularly the varroa mite, as well as climate change (yes, the most famous super-villain). I have tried to collect some tips on how you can help to save the bees.

1 Buy Organic Food

I know this sounds very cliché and green millitant. But one huge problem for bees are pesticides, especially so-called neonicotinoids. Pesticides shorten the bees lifespan and damage their ability to reproduce. In addition, neonicotinoids have been shown to impair worker bees orientation abilities which is why many cannot find back to their hives. Also, monocultures that dominate modern agriculture are a huge problem for bees. Monocultures decrease food variety and only bloom during short timespans leaving the bees hungry for the rest of the year. Organic farming renounces the use of pesticides and monocultures, which is why eating organically grown food is a good way to help the bees.

2 Plant Wild Flowers

As mentioned above agricultural monocultures are damaging for bees. But you can do something against this by planting indigenous wild flowers in your garden or on your balcony. This way you can create safe havens for bees offering food with a good variety. In addition, you will also help other struggling insect species, for example butterflies. Be aware, that this effect can not be achieved with ornamental garden flowers like roses or pansies, as these can not function as a food source for bees and other pollinating insects.

3 Fight Climate Change

Climate change is affecting bees in a number of ways. Warm winters, extreme temperature fluctuations and earlier flowering phases cause massive stress, damage their circulation and make them more vulnerable to parasites like the varroa mite. These factors will most likely get more severe in the future with continued global warming. To prevent this you can do, what you might already do to fight climate change: Use the bike or public transport instead of the car. Take the train for long distance travel instead of the plane. Switch to an electricity company that provides you with energy from renewable power plants.

Now, go and save the bees! And your own food…