Category: what is life?

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Time travellers to Nowhere (3)

We are in Nowhere Wood, about 300 million years ago, staring at a forest of tree ferns, watching them make oxygen. Over the years, these tree ferns have made so much oxygen that its concentration in the air has risen to about 35%, (compare that with the 21% found in the 21st century).

There is so much oxygen that the lightning strikes produce frequent explosions in the air, causing forest fires. Nowhere Wood is a dangerous place to be, sometimes.

 

 

The animals are using the oxygen to grown large: some millipedes are 1.5 metres in length and 0.5 metres wide. Some dragonflies have 70 cm wingspans.

 

 

 With all of this food available, there are opportunities for new  carnivorous lizards to appear, including Hylonomus. This is one of the first creatures to have a new  eggs with membranes inside, a characteristic later shown by all birds.

 

 Also the flesh-eating Anthracosaurs first appeared at this time. These are the direct ancestors of the dinosaurs, that appeared millions of years later.

In Nowhere Wood, everything is connected together, in space and in time.

 

So many adventures in space and time, so much opportunity for the evolution of new forms. All of which depends on the formation of sandstone in Nowhere Wood.

  1. Imagine what it was like to live in Nowhere Wood 300 million years ago. What would be the same and what would be different.
  2. How do you think the world will change in the future?

Safety in numbers

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All change!

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.

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.

 

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?

A year in the life of a sugar factory

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Climbing the walls

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.

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.

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.

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? 

Life is a relay race

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Organise and stay alive

Living organisms have very organised structures.

Everything depends upon the way that the different parts of their bodies work together.

The parts of this watch work together, so that the hands of the watch move round in a rhythm that we use to tell the time. The hands do this because of the precise organisation of all of the parts of the watch.

The ability to tell the time emerges from the watch, only when all of the parts move together smoothly. If anything goes wrong, the watch “stops” and the ability to tell the time disappears.

Living organisms are alive because they are organised. Everything depends upon the way that the different parts of their bodies work together.

For an organism, life emerges and exists for only as long as its parts work together smoothly.

If anything goes wrong, the organism becomes ill. If it is very serious, then the organism dies and its life disappears. This is difficult to think about, but it is a fact of life.

  1. One of the important features of human society is that we have learned how to care for the sick and the elderly. Hows does this help the survival of humanity?

Moving things on

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Being and becoming in Nowhere Wood

 

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? 

 

Counting the ways to stay alive

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Counting the ways to stay alive

No one knows how many different kinds of animals and plants are alive today, and, sadly, we never will.

A survey in 2011 suggested that there are nearly 8 million species of animals and nearly 300, 000 species of plants.  Astonishingly, nearly 90% of these species have yet to be discovered, described or named. Many are found in hard-to-reach places, such as tropical rain forests or the deep oceans. Given the rate of man-made habitat destruction, it is possible that many of these species will become extinct before they can be named by scientists.  

These 8.1 million species are, for now, the success stories of evolution. Each is a unique way of solving the problems of surviving and reproducing in an unforgiving and changing environment.

All species, like this humpback whale, have special characteristics that allow them to survive in their chosen habitats.

But if the habitats change too much, such as when when the oceans become acidified, rainforests are cut down or burned, then species may no longer be able to survive and they become extinct. Forever. 

  1. Why does it matter that species of organisms become extinct before scientists can discover them?

Organise and stay alive

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A life well lived

Sir Paul Nurse is one of the most important biologists in the world. He is Director of the Francis Crick Institute in London and has served as President of the Royal Society. In 2001, he shared the Nobel Prize in Physiology or Medicine for his work on the proteins that control the division of cells.

Sir Paul’s first book, ‘What Is Life?’ is one of the must-read books of the autumn. It has an accessible and engaging style and is likely to inspire many young people on a journey into biology.

The book has several themes, some autobiographical, as we follow Sir Paul into his laboratory to share his passion for the ways that “lowly” yeast cells divide. He is disarmingly modest, pointing out that he studied yeasts because he found them interesting. At the start he had no idea that the work would unlock the secrets of cancer and lead to the development of new treatments. He tells of how he almost failed to get into Birmingham University because he could not pass O-level French.

He recalls how once, when he was tired, he threw a contaminated petri dish away before going back to check it again, only to discover the holy grail of yeast cells, the one with the mutated cdc2 gene.

In this regard, his story is similar to the “accidental” discovery of penicillin by Alexander Fleming in 1928.  Fortune favours the prepared, though: both scientists had the foresight and self-discipline to go back their discarded dishes to discover something more valuable than gold.

Sir Paul guides the reader through five steps of biology: the cell, the gene, evolution, life as chemistry, life as information. These are brought together in a glorious conclusion to consider the biggest question” what is life?”

“The answer I got at school was something like the MRS GREN list, which states that living organisms exhibit Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition. It is a neat summary of the sorts of things that living organisms do, but it is not a satisfying explanation of what life is. I want to take a different approach. Based on the steps we have taken to understand five of biology’s great ideas, I will draw out a set of essential principles that we can use to define life.”

Nurse, Paul. What Is Life? (p. 96). David Fickling Books Ltd.

This is what makes the book so special and why it should sneak into the bookshelves of all teachers of biology and their students. It is a glorious and joyous read.

This hardback book is available now from booksellers, and for eager beaver readers, like me, on Amazon Kindle.