Category: Cycles

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Subterranean superheroes

Leaf fall in Nowhere Wood. [Photograph: Neil Ingram]
The leaves covering the floor of Nowhere Wood are slowly disappearing in the mild December nights. Fog hangs in the air. The wood is preparing for winter and everywhere is quiet and still. Most of the real action is taking place below the ground, but what is making the leaves disappear?

 

Earthworm [Photograph: Shutterstock 1596740926, licensed to NI]
The culprits are earthworms, the little subterranean superheroes that do most of the heavy lifting in Nowhere Wood. There is about 45 million earthworms underground in the wood, with a total biomass equal to about twenty elephants. They are easily the most abundant animal in the wood, but they are so rarely seen.

 

Earthworm. [Photograph: Shutterstock 171009224, licensed to NI]
Earthworms tunnel into the soil making the burrows that are their homes. At night, they come to the surface to drag fallen leaves back down into their burrows. The burrows are also perfect homes for bacteria and fungi.

 

 

Fungi mycelia. [Photograph: 159740926, licensed to NI]
The bacteria and fungi  feed on the leaves, turning them into nutrients that they use as food. This is humus. Earthworms eat the fungi and the humus-rich soil. As they do so, they glue the soil particles together into small clumps. This improves the quality of the soil, making it a perfect environment for plant roots.

 

Plant roots in Nowhere Wood. [Photograph: Neil Ingram]
Plant roots need plenty water, air and nutrients, all of which are given to the soil by the fungi and earthworms. We can think of earthworms as the soil’s farmers, ploughing the soil for the plants. Without their work, no life could exist in Nowhere Wood.

 

Charles Darwin. [Shutterstock 252138244, licensed to NI]
The famous scientist Charles Darwin studied how plants, earthworms and fungi work together to keep woods alive, and he wrote a famous book about it in 1881. He wrote about earthworms: “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organised creatures.”

  1. In what ways do you think that soil is alive?
  2. Think about how the trees, fungi and earthworms work together to keep the wood alive.

Today, Friday 4th December 2020, is World Soil Day 2020. Here is a video celebrating our dependence on soil:

Notes on the story

Spring is coming!

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A year in the life of a sugar factory

The leaves of plants are everywhere in Nowhere Wood, helping to keep the wood alive. Leaves are organs: collections of living tissues and cells, having adventures in time and space. This is the story of a year in the life of an oak leaf.

Leaves are factories for making sugar from sunlight, water and carbon dioxide from the air. No human factory can do this, which is why we, and all other organisms, are so dependent on plants. Leaves are the producers of food.

Buds of the English oak.
Buds of the English oak. [Photograph: https://commons.wikimedia.org/wiki/File:English_Oak_(Quercus_robur)_buds_(8535459373).jpg]
In is late November and the cells that will divide to make the new leaf are protected safely inside the scales of the bud. Early in March, when the days warm and get longer, stem cells within the bud start to divide many times, producing all of the cells of the new leaf. To start with, the cells are very small and all look the same.

Emerging leaves. [Photograph: shutterstock_244078297, licensed by NI]
Soon, the cells take up water and get much larger. They escape the protection of the bud and the new leaf emerges. The new cells no longer look the same: they are on different journeys of development, becoming all of the different cells and tissues that make up the leaf.

 

New leaves. [Photograph: Stutterstock 671376856, licensed by NI]
The leaf is a factory for making sugar. Like any factory, it has a source of energy and transport systems to get the raw materials into the factory.  It also moves the manufactured sugar out to the places in the plant where it is needed. The heart of the factory is the production line where sugar is made. These are called chloroplasts and the leaf has millions of them, all making sugar whenever the sun shines. The Spring and Summer are sugar making seasons.

Oak leaves in autumn. [Photograph: Neil Ingram]
Gradually, in the autumn, when the days get cooler and shorter, the sugar factories are shut down and abandoned. The chloroplasts lie in ruins as everything useful is recycled back into the branches of the tree. All that remain are the frameworks of cell walls, turning brown as they dry in the autumn air.

 

Dead leaves
Dead leaves. [Photograph: Neil Ingram]
Finally, the oak tree makes a special layer of cells that separates the old leaf from the stem, and the leaf is ready to fall when the wind blows strongly. The fallen leaves are not wasted, becoming energy stores for the organisms that feed on them. Next year’s buds are forming and wait for spring and the production of new leaves.

If leaves are factories form making sugar, then trees are factories for making leaves.

Everything has its own season in Nowhere Wood.

  1. Think about how the leaf is a factory for making sugar. Where does its energy store come from? How do the raw materials get to the production line?
  2. The production of leaves is sustainable in Nowhere Wood. What do you think this sentence means?

Notes on the story

Subterranean superheroes

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All change!

[Image: https://www.clipartof.com/portfolio/sajem/illustration/happy-moodie-character-looking-at-his-reflection-in-a-mirror-227335.html]
When you next look into a mirror ask yourself if you are the same person as you were yesterday. Well, of course you are.

Even people who last met you ten years ago can still recognise you and call you by your name. Although they might add, “My, how you have grown!”

And yet, if we could see under your skin, we would find that you are not the same. One of the biggest mysteries in biology is how we can change all of the time, whilst still staying the same.

Your skin cells live for about two weeks, so every month they are completely replaced. Red blood cells live for about 100 days and about two million are made in your body in every second.

Some of the chemicals in your cells exist for only minutes or seconds.

There is an energy store called ATP, which is needed for muscle contraction. ATP is made and broken down within 15 seconds.  Cells need glucose to make ATP and this explains why muscle cells need a continuous supply of glucose to stay alive. This comes from our food.

[Image: https://www.clipartmax.com/middle/m2i8d3m2Z5d3G6d3_hm00260-%5B1%5D-digestive-system-close-up/]
Even large organs, like the liver, are replaced regularly. You grow a new liver every year. The cells in the alveoli of your lungs are renewed every eight days. Even the bone cells in our skeleton are replaced every three months. Your entire skeleton is remade every ten years.

 

[Image: http://halloween.phillipmartin.info/halloween_skeleton.htm]
So, when your friend sees you after ten years and calls out your name, there is not a single part of your body that was the same as when you last met. You have been completely remade and remodelled. And the same is true of your friend.

 

So, how can this be? New cells are made when one cell divides to make two cells. The information in the genome is copied before cells divide, so the new cells always receive the same information as the old cells.

The new cells use this information to grow bigger and to develop. So, you stay the same because of how your new cells use the information in their genomes.

Living organisms are alive because they actively remake themselves. No man-made machine can do this. Which is, perhaps, just as well.

  1. In what ways have you changed in the last ten years?
  2. In what ways have you stayed the same?
  3. Why do need to eat food everyday?

Notes on the story

A year in the life of a sugar factory

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Life is a relay race

This story continues the adventures of the ferns in Nowhere Wood. The first part of the story is Climbing the walls.

The genome of the fern contains essential information that the fern needs to grow and  make new cells. At different times the fern produces spores, sperm and eggs and the two forms of the plant. The genome contains information on the growth of each of these stages.

The information in the genome is the same in every cell of the fern because an identical copy of the genome is found inside the nuclei of all the cells of this fern at every stage of its life.

The genome is found in the nucleus of each cell.

Fern chromosomes

The genome is divided between a number of chromosomes. The diagram shows the genome of the Adder’s tongue fern. It has about 1440 chromosomes. This is the largest number of chromosomes of any organism in the world!

Fern genomes are larger than the genomes of other organisms, because they contain the information the fern needs to grow spores, sperms and eggs as well as the two forms of plant.

The genome contains the secrets of how to be a fern and how to move forward in the adventure. This information has been copied and passed on to each generation of ferns, ever since the first ferns evolved about 390 million years ago.

Life is like a relay race: genetic information is passed on from one generation to the next in the genomes of sperms, eggs and other gametes.

These ferns are having risky and uncertain adventures in time as well as space. If the secret information is not passed on correctly, then the species may become extinct. History shows us that most species that have ever lived on Earth are now extinct.

    1. Why do you think it is essential that the genetic information from parents to offspring is copied accurately?
    2. Why do you think the fern genome is so large, compared with other types of plant?

Notes on the story

All change!

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Climbing the walls

Hart’s tongue fern growing on the sandstone walls of Nowhere Wood. [Photograph: Neil Ingram]
A hundred years ago, Nowhere Wood was a sandstone quarry, and there is still a cliff face at the end of the wood.
How can this hart’s tongue fern grow on a vertical cliff face about two metres from the ground.

That is quite an adventure in time and space. This story explains how this fern can climb walls.


Ferns are an ancient group of plants, first appearing on Earth about 390 million years ago. That’s about 260 million years before the emergence of flowering plants.

Spores on the under surface of a fern leaf. Nowhere Wood. [Photograph: Neil Ingram]
Like fungi, another ancient group, ferns produce spores. They are the brown dots on the underside of this fern leaf. Spores are light and float in the air like particles of dust.

One spore floats up to a small crack in the rock face. Rainwater and the decaying remains of a leaf have formed a sticky, jam-like, humus inside the crack.  The spore sticks to the humus and germinates, developing into a tiny little plant, about 10 mm long.

Drawing of a gametophyte of a fern. [Image: https://picryl.com/media/prothallus-gametophyte-0bab1a ]
This is a fern, but it is not the mature adult form. It has tiny roots that grow into the humus, drawing nutrients from it.
This small plant is called a gametophyte because it makes gametes for sexual reproduction. Gametes are sperm and egg cells. 


These gametes will come together to make the adult fern on the surface of the tiny gametophyte.

Sperm from ferns. [Image: https://upload.wikimedia.org/wikipedia/commons/d/d7/Fern_sperm.jpg]
The gametophyte makes many small sperm that swim in the water on the surface of the plant. They swim towards eggs, which are much larger. This photograph shows a fern sperm fertilising a fern egg.

The sperm and the egg join together. A single cell is produced that will grow into the adult fern. Eventually this fern will make spores of its own.

This may sound like a long-winded and complicated adventure, but it seems to work well, because there are so many ferns in Nowhere Wood.

The fern exists in several different forms during its adventure: spores, eggs, sperm, gametophyte and adult plants. What do they have in common?

Each of these forms is made of one or many cells. Each cell contains a nucleus, and inside each nucleus is a genome. Genomes contain information. The information in the genome is the same in all of the different forms of the fern.

The genome contains the secrets of how to be a fern and how to move forward in the next step of the adventure.

  1. The fern exist in several different forms during its adventure: spores, eggs, sperm, gametophyte and adult plants. Think why is important that the genome in every form is the same? 

Notes on the story

Life is a relay race

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Moving things on

The weather is warm and wet in Nowhere Wood.

These are perfect conditions for growing the fungi that spread  everywhere throughout the soil of Nowhere Wood. Fungi are Nature’s recyclers, feeding on the fallen leaves, fruits and wood.

Mycelia of fungi. [Photograph: Neil Ingram]
Fungi feed on the wood of the dead oak trees, turning it into nutrients that provide energy and chemicals needed  to grow new fungal cells.  (These cells form long threads called hyphae). Some fungi can spread out over really large areas, several kilometres wide.

At this time of the year, the fungi are busy ‘ being’.

Fungi in Nowhere Wood. [Photograph: Neil Ingram]
Then one night, silently and without warning, the fungi do something else.

They produce structures that we call “mushrooms” **.

Mushrooms are  fruiting bodies. They produce thousands of tiny spores.

Spores are small and light. They are carried on air currents to new places in Nowhere Wood, where they will germinate and grow into new hyphae.

Fungus in Nowhere Wood. [Photograph: Neil Ingram]
Spores have often been found in the filters of jet aircraft flying at the edge of the atmosphere, so some spores can travel right round the world. When fungi produce spores they are ‘becoming’ something new: small, light and mobile versions of themselves.

Decaying fungus in Nowhere Wood. [Photograph: Neil ingram]
Then, almost as soon as they arrive, it is all over. The fruiting bodies die and become food for other fungi and bacteria in Nowhere Wood.

This is how it is. The precious molecules are used, recycled and become part of the growth of new organisms. Nothing is ever wasted.

  1. Nearly all of the atoms present on Earth when life began to evolve about 3.7 billion years ago are still found on Earth today. Many of them are found locked inside living organisms. Sooner or later, all of these organisms will die. Imagine what life would be like without Nature’s recyclers.
  2. You are a collection of recycled atoms. Think about how carbon atoms enter and leave your body. [Hint, carbon atoms are found in carbohydrates and in carbon dioxide.]

You can read more about ‘being and becoming’ here.

 

**Some mushrooms are good to eat, others are really poisonous and can kill us. It is hard to tell them apart unless you are an expert, so it is sensible not to touch or eat any mushrooms you find in a wood.

Notes on the story

Climbing the walls

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Squirrel wars

One hundred and fifty years ago, the oak woods near Nowhere would have been home to red squirrels. Now they have all disappeared.

A red squirrel. [Photograph: https://upload.wikimedia.org/wikipedia/commons/e/e1/Red_Squirrel_-_Lazienki.JPG]
The red squirrels have been replaced by grey squirrels that were introduced into the UK from the United States in the 1870s.

Grey squirrels spread to nearly all parts of the UK, replacing the red squirrels wherever they went. Now red squirrels are only found in a few places, where they are protected.

Grey squirrels are 60% better at digesting oak acorns than red squirrels, which seem to prefer hazel nuts. Oak acorns are much more common in Nowhere Wood than hazel nuts, and this favours the grey squirrel.

Grey Squirrel. [Photograph: Gary Helm, https://www.flickr.com/photos/ghelm/8645487905]
The success of grey squirrels at surviving and breeding in Nowhere Wood is due to the production of acorns, which varies from year to year.

Survival is a risky journey for any squirrel: the arrival of new competitors or interruptions to the food supply can pose real challenges.

 

Their lives are  adventures.

The word ‘adventure’ has two parts:

Ad means moving towards something.

Venture means attempting something dangerous or difficult, that is risky, with no guarantee of success.

Put the two together and you get the idea that the lives of all living organisms are risky journeys into the future, with no guarantee of success or survival.

If you like, you can think of life as:

organisms having adventures in time and space

  1. Think about the squirrels and the oak trees. In what ways are their lives adventures?  [Hint: think about what the word adventure means.]

 

Notes on the story

Moving things on

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Being and becoming in Nowhere Wood

 

life cycle of a butterfly. [Image: https://upload.wikimedia.org/wikipedia/commons/thumb/7/78/Butterfly_life_cycle_diagram_in_English.svg/1154px.Butterfly_life_cycle_diagram_in_English.svg.png]
All living organisms are doing two things at the same time. They are:

Being (they are keeping themselves alive) and

Becoming (they are moving towards the next stage of their lives).

The butterfly is being and becoming at each stage of its life.

All of the animals and plants in Nowhere Wood are also “being” and “becoming”.

  1. How are the oak trees in nowhere Wood being and becoming?
  2. How are you being and becoming? 

 

Notes on the story

Organise and stay alive