Predator, prey, frogs and food chains

Most animals in a habitat can be classified as predators, prey or both. A predator is an animal which kills another animal (the prey) for food. For example, a snake is a predator because it eats frogs (prey). However, the frog is also a predator (however unintimidating it seems!) because it eats grasshoppers. With so many animals having differing diets, even a small environment can produce a food web such as this one.

ImageBecause the grass eats no other species, only consuming nutrients from the soil, we call it a producer. The fox and snake are called top consumers because no other species eats them within this habitat. But in certain habitats, large birds of prey eat snakes.

Food webs can be affected by even the most subtle increase or decrease in the number of any species. If, for example, the population of frogs increased in the above food chain, then several changes might take place:

1)       The number of grasshoppers would decrease because there are more frogs to eat them.

2)       More snakes would come to the habitat and prosper because there are more frogs to eat.

3)       Because there are more snakes, the number of rabbits will deplete as they will be eaten by the higher population of snakes.

Consider what might happen if:

a)       The population of mice increased

b)       The population of rabbits decreased

c)       A drought led to a poor crop of grass

Whether their population increases or decreases, each species within a habitat will be affected by changes in population to some degree.

If your class is interested in getting to grips with food chains, our app Pairing for Early Science introduces them with the foundation science vocabulary to get them started!

Below: predator extraordinaire, office cat, aka Mr Worthington

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Comet Ison – will it, won’t it?

There’s been much excitement lately around the possible sighting of Comet Ison next month. But what is a comet and why is everyone so excited about Comet Ison?

Comets are essentially large dirty snowballs, made of water, ice, dust and carbon-based compounds. Like planets, they orbit around the sun. But unlike planets, which are much larger and stay at the same distance from the sun, a comet’s orbit is elliptical (oval-shaped). This means they are sometimes closer to the sun than at other times.

When comets are closer to the sun, and therefore hotter, the material in the comet starts to melt into what is called a coma. This gives the nucleus a fuzzy appearance. Coma being Latin for hair, maybe ancient scientists thought the comet looked like it had a messy hairdo! Solar winds cause the coma to blow into a tail. Despite common depictions, tails don’t trail behind the comets but always away from the sun, blown by its winds.Image

What’s so special about Ison is how close it went to the sun. There had been three main theories about what the fate of this “sungrazer” would be. One, the comet could have exploded under the solar pressure. Two, it could have simply fizzled out. But what many of us hoped was that its closer encounter with the sun would give it a very bright tail. The disappointing initial prognosis on Friday was that Ison had “died” and fizzled out but since then there have been indications it might be brightening. We’re no wiser than we were before its brush with the sun!

If we’re lucky, the once-in-a-lifetime sighting of Comet Ison will begin in early December. Do send us any great pictures you get!

Another well-known comet is Halley’s Comet, which appears every 76 years. The most famous instance was just before the Battle of Hastings (as depicted left, in the Bayeux Tapestry) where William the Conqueror defeated Harold. Harold ignored warnings that it was a bad omen, however the comet became a portent of fortune for the victorious William! We won’t see Halley’s Comet until 2061.Image

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Exploding beans and animal droppings: seed dispersal in four methods

In case you hadn’t noticed, it’s getting colder, leaves are dropping and everything’s looking pretty miserable. But far from going to bed for the year, nature’s at work more than ever. Seed dispersal is a key process in paving the way for new growth next year.

For most plants, autumn’s the time for producing seeds. Conkers, acorns, dead flower heads in the back garden – these seeds are all being shed now. But they also need to be scattered around so that they can start growing roots. There are four main methods of seed dispersal.

Animal dispersal who’d have thought animal droppings were helping to spread plant growth? When birds eat berries, they also eat the seed. Wherever they poo, they’re also dropping seeds for new plants. And it’s not just by eating that animals do their part. Think of those goosegrass seeds (below) which stick to your clothes. Their little spikes can piggy back on birds, squirrels, foxes, even people, and drop off far away.

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Wind dispersalthose chilly breezes aren’t just there to make you shiver. They’re able to blow lighter seeds, sometimes over great distances, allowing new plants to take root far away. Watch how easily these dandelion seeds are swept away. When you’re next outdoors, look out for poppy seeds (very small and light) and sycamore seeds (with their “propeller blades”). These designs make them ideal for travelling further.

Explosive dispersalif you’ve ever sat near gorse on a sunny day, you might have heard mini explosions. When the pods of some plants dry out, they tighten around the seeds until they explode. This shoots seeds around the area, allowing an effective dispersal. Check out these exploding seed pods. You don’t have to go far to find this phenomenon either. Runner beans, broad beans, really almost any beans, explode to shed their seeds.

Water dispersal – rivers and larger bodies of water can deposit seeds miles from their original plant. Similarly to wind dispersal, this is most effective when the seeds are light. That’s one reason why willow and silver birch trees (often found near water) have such small seeds.

For all of these methods, an important goal is to spread the seeds as far as possible. This prevents over-crowding which can seriously affect growth. Ever tried planting seeds too close together on the veg patch? It doesn’t work!

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Shadow play

Shadow puppetry is an ancient form of storytelling through the use of puppets and light. It began about 2000 years ago in China when an emperor’s wife died, and his court created a shadow version of her so that the emperor could see her again.

Shadow theatres are still used today. Check out these people building a car out of just a few props!

You too can do it at home with just a torch and some paper shapes. Ask an adult to point a torch at a wall a couple of metres away. Then hold paper shapes between the torch and the wall to cast shadows on the wall. Here’s a good guide for making shadow puppets.

From animals to trees and smiley, sad and scary faces, you can make all sorts. Even your hands can create different animals – though some are more complicated than others! Can you guess what each animal is?Image

Shadows are made when an opaque (non see-through) object blocks light. The size and shape of the shadow depends on the distance between the light source and the object casting the shadow as well as the distance between the object and the surface on which the shadow is cast. The closer you move an object to the light source the bigger it gets. Try it – if you hold your hand ten centimetres from the torch it blocks out much more light than if you hold it a metre from the torch.

 Good luck casting shadows – let us know if you get any good ones!

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The benefits of being a wall-moth – camouflage and natural selection

While topping up our pumpkins and peppers with water, I came across this camouflaged fellow perched outside our kitchen wall.

ImageAnimals of many shapes and sizes seek to camouflage themselves. This means they are able to disguise themselves in their environments.

One of the most common reasons an animal camouflages itself is to hide from predators. One bird, the Egyptian Nightjar, common to north Africa and the Middle East, uses its sand-coloured plumage and brown specks to hide itself in the desert, as in this image.

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In doing so, potential predators can’t spot it and so our nightjar remains safe. Of course, if this same bird tried the same tactic in, for example, the Arctic or grassy Dorset, it would be in a lot of danger (aside from the chill!), because it would be spotted by predators fairly soon.

But while the likes of the nightjars are using camouflage, so are the wily predators. They’re hiding themselves in order to creep up on prey – what better way than making yourself invisible? Like the Egyptian nightjar, the stonefish also disguises itself in sandy colours but it does so as a predator. Watch this video to see this seamlessly disguised fish surprise its unsuspecting prey.

Good animal camouflage is a result of natural selection, a key part of evolution. All animals produce offspring with genes slightly different to their parents. This variation means that some well-adapted animals (e.g. those that can hide well) are born, as well as poorly-adapted animals (e.g. an unconvincingly coloured nightjar). Hiding themselves well allows an animal to survive or continue being nourished, and so they are able to pass on their genes. Badly adapted animals often die before they are able to reproduce and pass on their genes. And so as a species continues to exist, they should become better and better adapted – both predator and prey.

Here are even more fantastic animal camoflages. The tawny frogmouths’ disguise is truly incredible but we also think the leaf-litter mantid is quite a character! http://kids.nationalgeographic.co.uk/kids/photos/gallery/animal-camouflage/#/tawn-frogmouths-myall-tree-3_24669_600x450.jpg

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The summer solstice is here!

Today is the longest day of the year (aka the summer solstice). This means the sunlight lasts longer than any other day, and the night is shorter. But why do the lengths of days change throughout the year?

The Earth is a sphere and spins on its axis once a day. During the day we’re closest to the sun, while during night we’re further away and therefore without its light and heat. Imagine an apple on a barbeque skewer. Picture the apple rotating around the skewer – this is what the earth does. Sometimes it’s facing the fiery light (whether it’s a barbecue or a sun) and sometimes it’ll be cold.

The seasons occur because the Earth’s axis is tilted by 23 degrees. This means that, as it travels around the sun, either the northern or southern hemisphere is tilted towards the sun. When the northern hemisphere is tilted towards the sun, our relative closeness to it means we get more exposure to daylight. More daylight means longer days.

During the summer, there is daylight for twenty-four hours in the Arctic, which they call Land of the Midnight Sun. Their winters are very dark, however, and people can go for weeks without seeing sunlight.

Many traditions surround the summer solstice. Stonehenge was a place of worship built by Druids thousands of years ago. The stones are aligned to the solstice. People still gather there to see the sunrise. Below is an image from this morning – unfortunately, there was too much cloud cover to see the sun.

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Exactly six months after the longest day is the shortest day (December 21st) where our nights are longest. In Australia, it’s the reverse. This Friday they’ll be closing the curtains earlier than any other day. While we’re (hopefully!) enjoying a bit of sun, our friends Down Under are preparing themselves for weather we’d think of as festive!

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How to make a paperclip float

One of the forthcoming activities we are creating is about testing things that float, so here’s an experiment of how to make something float that normally sinks.

All you need float is a bowl of water, a paperclip and some tissue paper.

If you try making a paperclip float in water simply by dropping it in, the chances are it will sink to the bottom, as in this photo.

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However, follow these steps and you may find it floats on the water for some time.

1)      Fill a bowl with water

2)      Place a single sheet of tissue paper flat on the surface

3)      Very carefully, lay the paperclip on the tissue

4)      Using a pencil or finger prod the tissue paper into the water

5)      Hopefully, the paperclip should rest on the surface

If the paperclip floats, this is because it is lying on the “skin” of the water. Water particles have a positive and negative static charge. Because opposites attract, they stick together and create the skin effect, known as surface tension. Simply dropping the paperclip into the water can disrupt this balance, but the gentle actions of lowering the tissue and then the clip, then removing the tissue, allow the surface tension to be maintained.

ImageIn this image, you can see the gentle imprint the clip makes in the water. You might see a similar effect with water insects, especially now it’s spring time. In the below picture, see how the pond skaters’ legs gently depress the surface. The skater uses the water’s skin to its advantage, enabling it to travel over the surface of the pond without sinking.

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Let us know if you have any luck with it or capture any good pond skater photos!

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Scientist under the microscope: Marie Curie

We Love Science wishes to commemorate an exciting historical scientist – Marie Curie. She’s a well-known figure (she even has a charity shop named after her!) but what exactly did she do?

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Curie was an admirable scientist for many reasons. Not only was she a woman facing great opposition in the male-dominated world of science, her efforts helped save and treat many injured people in the First World War. Curie was the first woman to be awarded the Nobel Peace Prize, and the only person to win it twice.

Working with her husband, Pierre, she discovered that when nuclei break down they produce radiations. This means that they are radioactive, a term the Curies coined. They discovered two radioactive elements – polonium and radium.

Following Pierre’s death and during the First World War, Marie worked to develop mobile X-ray units that could be used to diagnose injuries at the battlefront. The International Red Cross made her head of its radiological service and she held training courses for doctors.

During their research, the Curies fell sick and physically exhausted. These effects have been retrospectively diagnosed as symptoms of radiation sickness. They nonetheless persevered, often with raw and inflamed hands caused by handling radioactive material. Curie herself died of prolonged exposure to radiation.

Because of her research into x-rays and the treatment of cancer, the charity Marie Curie Cancer Care was named after them.

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Nature notes on an Easter walk

Stuffed with roast lamb and trimmings, we braved the cold for an Easter afternoon walk. It’s amazing what you can find outdoors when you scratch beneath the surface.

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Take this stump. The tree itself was dead – perfect for firewood! – but at its base you can see the decomposition process already at work.

Once a plant or animal dies, bacteria, fungi and worms (decomposers) leap onto the remains and eat them. What they leave behind becomes part of the soil. See how already the decomposing tree resembles soil. Before long, new plants will be using this very soil to grow. And so the cycle continues!

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Just centimetres away was this plant. Don’t let its demure appearance fool you. Its smell is overpowering – even ten metres away! Its name – wild garlic, also named bear leek. It’s a firm favourite of bears and boars, though no sign of those in Dorset (as far as we know).

But humans can eat them too, and we found plenty of delicious recipes, like wild garlic pasta and wild garlic mayonnaise. We’ve got a bunch of leaves waiting in the kitchen. Watch this space. But watch you don’t confuse wild garlic with its poisonous lookalikes: the Lily of the Valley, and other similar-looking plants.

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There are a lot of deer in Dorset. We stumbled across this well-trodden deer track. We’re keeping our eyes peeled for antlers on the ground because it’s primetime shedding season now. Following the mating autumn months, when bucks (male deer) fought each other and competed for the roe (female deer), they have no more use for them. We’ll let you know if we see any!

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Creatures that Glow

This week We Love Science tweeted a story from the BBC website where they talked about scientists investigating whether the light given off by some living creatures, such as fireflies and jellyfish, can help us in medical and other areas.

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One of the activities in “Science by Storm” is about sorting sources of light into man-made and natural categories, and one natural sources is the glow worm. We started talking about these unusual creatures that give off light – unusual because they are rarely seen in the UK. I have only once seen red glow worms in a farmer’s field in Dorset one summer night.

The production of light by a living organism is called bioluminescence, which is a compound word: bio for ‘living’ ;and luminescence from the Latin word for light. It is produced as a chemical reaction in cells in part of their bodies. There are a number of reasons creatures give off light:
– glow worms use it to attract moths or other insects, which then get stuck on the sticky skin and get eaten
– fireflies and beetles emit light to attract a partner, with some fireflies having a special flashing signals for courting!
– deep in the ocean some squids squirt luminescence to repel predators

 On coral reefs, coral can be fluorescent, which means they re-emits light when it is shone on the coral. Scientists think this is a way the coral protects itself from sunlight. Sometimes algae is fluorescent and boats may leave behind them a colourful trail.

 

If you know of any creatures that glow near your school, we’d love to hear from you in the comments!

Resources

UK Glow Worms 

BBC Nature

Project to make glow in the dark jars (English and Hungarian)

A collection of references to bioluminescence

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