Category: Biology

An old survivor

Much of the old tree would have survived for while, so the new shoot was shaded and would have grown out at an angle, attracted towards the light. Since then, the new growth has itself become a mature tree.

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Image of the day – 138

What’s in an image? Sometimes quite a lot, more than meets the eye. I’m posting an image every day or so.

Click to enlarge

I spotted this old tree when we visited Blenheim Palace today. It’s probably an ancient oak though I didn’t get close enough to check with certainty.

The thickest part, the lumpy-looking base is the remaining stump, all that remains of the original tree that would have grown from an acorn many hundreds of years ago. That tree was a sapling, then a youthful, vigorously growing tree; eventually if became a mature, majestic oak. But then the rot would have set in – literally. Holes made by a woodpecker, or damage from a storm cracking off a branch, gave access to unprotected wood beneath the bark. Insects may have burrowed into the wood, and eventually fungal spores would have germinated and started the decay process in earnest.

The weakened tree would have lost its vigour and been reduced to a hollow stump and failing branches. But finally, a new shoot must have appeared near the base and formed new, young growth. Much of the old tree would have survived for while, so the new shoot was shaded and would have grown out at an angle, attracted towards the light. Since then, the new growth has itself become a mature tree.

Another possibility is that a branch of the original tree survived, and with the other branches missing, grew into the shape we now see. A careful examination of the tree might reveal the truth. But however this curious old tree survived, it certainly has an unusual story to tell!

Donna and I enjoyed our day at Blenheim and will visit again from time to time this year as the seasons roll by. I’ll probably write about the place again.

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Image of the day – 27

In the natural way of things, each Aloe will produce an average of one new plant, and the population will remain in balance.

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What’s in an image? Sometimes quite a lot, more than meets the eye.

I’m posting an image every day (or as often as I can). A photo, an image from the internet, a diagram or a map. Whatever takes my fancy.

Aloe aristata

Today’s picture is a close up of an Aloe aristata plant with a developing flower bud. All plants, animals, fungi, bacteria and even viruses have ways of reproducing themselves. That’s one of the defining characters of life of any kind. We can be absolutely confident that the same will be true of any life forms anywhere in the universe.

The Aloe flower bud will develop on a tall stalk and if the flowers that form are pollinated they will produce and release seeds that stand a chance of germinating and growing into new, similar, Aloe plants. In the natural way of things, each Aloe will produce an average of one new plant, and the population will remain in balance.

The only choices available to life are to survive for ever with no reproduction, or to live for a limited time and leave behind new versions to carry on the process. What life cannot do is live forever and reproduce: that would lead to overpopulation and catastrophic failure of resources. Even with reduced family sizes, the planet is no longer capable of supporting the billions of people on our planet. We face catastrophic population collapse due to lack of resources at some point unless we can reduce our population size in some other way first. That’s a matter of simple arithmetic, not a political statement or some kind of guesswork. If we don’t face and fix the issue, something else will sooner or later.

Themed image collections

The links below will take you to the first post in each collection

Cirencester, Favourites, Irish holiday 2024, Roman villa

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If you enjoyed this or found it useful, please like, comment, and share below. (If you don’t see those links, click the article’s title above the main photo and they will appear.) Send a link to friends who might enjoy the article or benefit from it – Thanks! My material is free to reuse (see conditions), but a coffee is always welcome and encourages me to write more often!

Image of the day – 23

By cooperation and coordination they manage all the behaviours and activities that we see on the larger scale. 

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What’s in an image? Sometimes quite a lot, more than meets the eye.

I’m posting an image every day (or as often as I can). A photo, an image from the internet, a diagram or a map. Whatever takes my fancy.

The fresh green of spring

There are few things as amazing as life. Perhaps there’s literally nothing as amazing as life in the entire universe! The photo shows the young, expanding leaves of a small-leaved lime tree (Tilia cordata).

Like all deciduous, temperate trees, leaf buds are formed the previous summer and over-winter after the old, mature leaves fall in late autumn. As temperatures increase in springtime, these buds swell and grow and the young leaves appear and expand. At first they’re a beautiful, pale green (lime green) but become a darker and duller shade as the days lengthen and they mature.

These processes all take place naturally in ways that are more complex than most of us might expect. Both plants and animal bodies are composed of countless tiny cells in much the same way that a large building might be made of bricks. Each cell is alive, contains a full copy of the organism’s DNA, and many of them have specialised roles to play. By cooperation and coordination they manage all the behaviours and activities that we see on the larger scale. So in some respects an expanding leaf is a lot like a growing community of people working together as a village or business. Having specialists makes it possible to do so much more, but cooperation becomes essential, not merely optional.

The rioting we’ve seen in some British cities in recent days has been disruptive and damaging to society as a whole. When the cells of an organism behave in uncoordinated and uncontrolled ways we call it a cancer. Rioting is a kind of cancer in a human society. We all know what happens when cancer becomes so widespread that the organism can no longer function. But organisms have ways of dealing with errant cells before they become overwhelming, and so do societies. Both police action and peaceful counter-demonstrations have been effective in controlling the UK riots in recent days.

Themed image collections

The links below will take you to the first post in each collection

Cirencester, Favourites, Irish holiday 2024, Roman villa

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Useful? Interesting?

If you enjoyed this or found it useful, please like, comment, and share below. (If you don’t see those links, click the article’s title above the main photo and they will appear.) Send a link to friends who might enjoy the article or benefit from it – Thanks! My material is free to reuse (see conditions), but a coffee is always welcome and encourages me to write more often!

Image of the day – 21

The plant, on the other hand, is a living organism. Nobody designed or manufactured it – life is much more wonderful than that!

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What’s in an image? Sometimes quite a lot, more than meets the eye.

I’m posting an image every day (or as often as I can). A photo, an image from the internet, a diagram or a map. Whatever takes my fancy.

It’s quite amazing how life clings on, even in the most adverse circumstances. This plant was growing in my front drive, somehow finding a way to get its roots into a narrow gap in the block paving. The blocks were designed by a garden landscaping company and manufactured to particular standards of hardness and resistance to my car rolling over them. They were designed to last.

The plant, on the other hand, is a living organism. Nobody designed or manufactured it – life is much more wonderful than that! The universe we live in is tailored to build ever more complex things from very simple beginnings. A handful of quantum fields is all it takes, and these are exquisitely able to give rise to fundamental subatomic particles. These group together, eventually settling into simple atomic nuclei. As the universe expanded and cooled, atoms of simple elements appeared, almost entirely hydrogen and helium. Stars condensed and formed heavier elements up to iron. I could go on, but it’s a long story! Maybe some other time?

For now, just consider the battle between order (my paving blocks and the urge I have to remove weeds that neither I nor my wife want to see growing there) and disorder (weeds thriving wherever they can, despite my best efforts). Life always wins in the end, it seems!

Themed image collections

The links below will take you to the first post in each collection

Cirencester, Favourites, Irish holiday 2024, Roman villa

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Useful? Interesting?

If you enjoyed this or found it useful, please like, comment, and share below. (If you don’t see those links, click the article’s title above the main photo and they will appear.) Send a link to friends who might enjoy the article or benefit from it – Thanks! My material is free to reuse (see conditions), but a coffee is always welcome and encourages me to write more often!

Human origins

Theorists can move forward again – and the picture seems a little more complicated than we thought.

Where did we come from, and how? We’ve long thought in terms of an evolutionary ‘tree’, but our origins in Africa are more like a braided channel. This idea provides a better fit to the data.

Based on fossil evidence alone, studies of human evolution have long agreed that modern humans evolved in east Africa and radiated out from there. But with the development of cheap, fast and reliable DNA evidence from modern populations, and DNA from fossil teeth and bone samples, it’s becoming clear that theorists can move forward again – and the picture seems a little more complicated than we thought.

Human dispersion, events described in the article all took place in Africa – Image from Wikimedia

On 17th May, Ragsdale and others published a research paper in Nature; ‘A weakly structured stem for human origins in Africa’; their evidence suggests evolutionary connections in populations that were separated for a while before recombining. So instead of an evolutionary tree (which most people were expecting) it seems that our human past is more like a set of braided channels.

Previous views on human evolution proposed a tree structure (branching but not recombining). However, the new ‘weakly structured stem’ model fits the data better than a tree model. It also explains the diversity of genetic forms in modern human populations, and shows that there is no single place in Africa where humans ‘originated’. After this process within Africa, humans spread out as show in the map.

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Elephant hawk moth

The caterpillar did something extraordinary – it mimicked a small snake

Have you ever seen an elephant hawk moth? If you live in Europe or Asia you might have spotted one of these amazing insects. In the United Kingdom they are fairly common, but perhaps not often seen. It’s a real treat to spot an adult or a caterpillar, both are amazing sights.

An elephant hawk moth male (credit: Wikipedia)
The circle marks the spot (credit OpenStreetmap)

Walking in the Cotswold Water Park recently, near the Gateway Centre on Lake 6, we spotted an elephant hawk moth caterpiller crossing the footpath (close to the grey circle in the map.

For a short time we just watched as it made its way across the path. But before it made it to the vegetation on the far side, some people appeared with a dog. The dog ran up enthusiastically to greet us and accidentally kicked the caterpiller before running off again. The caterpillar did something extraordinary – it mimicked a small snake.

Am I a caterpillar, or am I a snake?

The caterpillar crossing a stony path

For perhaps 20 seconds or so it writhed its body in a convincingly snakelike movement, and it pumped up several body segments behind the head, tucking its head down at the same time. With eye spot markings on its flanks, a scaly pattern on the entire body, and by raising up the front part of the body, it really did look the part. I wasn’t fast enough to get a photo, but I did get some video of the recovered caterpillar continuing on its way afterwards.

Searching the internet later, I found several good images of the caterpillar mimicking a small snake. Perhaps the best of these is show below.


The caterpillar looking very much like a snake (credit iSpot)

The natural world is so amazing, and so full of surprises, but mimicry is quite a common feature in both plants and animals. The European white dead-nettle has leaves that cannot sting but match the appearance of the unrelated stinging nettle very closely. Some insects look like pieces of wood, or a leaf, or a patch of white lichen, or a bird dropping. Many slugs look very much like animal droppings of various kinds, and as they move so slowly only an alert predator is likely to notice them. Predators, too, use camouflage which is not truly mimicry, but helps them merge into dappled sunshine and shade. Fish are often dark on top and silvery underneath. Sometimes they are patterned and look like the gravel bed of a stream or river.

Amazing!

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