The Natural World Series Written and performed by Stephanie Poppins This sleep series has been written to provide an educational transition into deep sleep.
Having taught in high schools for over 20 years,
I have come to understand learning happens in a myriad of ways and sometimes when you least expect it.
It is my pleasure to present to you one of those ways.
But before we begin,
Let's take a moment to focus on where we are now.
Take a deep breath in through your nose and let it out on a long sigh.
It is time to relax and fully let go.
Feel your shoulders melt away from your ears and feel yourself relaxing to the support beneath you as you let all the worries of the day seep away.
You are safe here.
We are all safe here.
Happy listening.
Episode 1.
The Origin of Species Every living thing belongs to a species.
Every plant,
Every animal,
Every fungus,
Every microorganism.
But what exactly is a species and how are new species formed?
The origin of species is as hotly debated today as it was when Charles Darwin first published his theory of evolution by natural selection more than 120 years ago.
In this series we will look at what natural selection is and how it works.
And we will come to appreciate just how amazing we are for having survived for this long.
Episode 1.
It is commonly understood in scientific circles that the living things we see today have all evolved from some distant ancestor by a process of gradual change.
According to Charles Darwin,
This gradual change is called natural selection.
Ever since it was first published,
Darwin's theory of natural selection has been one of the most discussed,
Disputed and misunderstood theories of science.
Yet it is a very simple idea and we can find evidence of natural selection wherever we look in the natural world.
If we were to search in a pond,
We would find many different living things.
But how would we sort them out into groups?
There are many different ways of sorting living things.
We could divide them according to their shape or their size,
Where they live or what we think they might feed on.
But one thing is for certain.
We would group together the ones that have particular features in common.
Perhaps the ones that can move.
Perhaps the ones that we consider to be plants.
As we look,
The more similarities we see,
The smaller our groups become.
The smallest basic group that biologists use is called a species.
The word species comes from a Latin word meaning kind or sort.
When we look at our groups and we see so many features in common,
We recognise them as coming from one species.
Every species has a Latin scientific name,
But many have everyday names as well.
It is important to remember when we sort living things into species,
They may look different at different stages of their lives.
For example,
A tadpole doesn't look like a frog.
An acorn does not look like a tree.
And a caterpillar does not look like a butterfly.
Sometimes it's difficult to decide just how different individuals must be before we recognise them as two different species.
In 1907,
For example,
Alfred Rendell decided that two different but very similar looking dandelions were similar enough for them all to belong to the same species.
But in 1928,
George Drewes decided the plants were different enough to belong to a different species.
In some cases it's impossible to decide,
And the number of species we choose to recognise is therefore a matter of opinion.
Naturally,
Living things will form their own groups.
There are breeding groups which animals form.
This is because of the way they breed.
When a weasel breeds,
It breeds with other weasels,
Never with any other kind of animal.
And when weasels breed together,
They produce more weasels,
Just like themselves.
In most cases,
A breeding group includes all the animals we would recognise,
On the basis of their physical features,
Such as one's species.
So a breeding group is another way to define a species.
Plants also form groups in nature because of the way they breed.
An oxide daisy breeds with other oxide daisies to produce more oxide daisies.
So oxide daisies form a breeding group.
Other plants form breeding groups too.
In most cases,
A breeding group includes all the plants we would recognise,
On the basis of their physical features.
Sometimes barriers between breeding groups occur.
A mule,
For example,
Is a hybrid and can be produced only when a horse and a donkey breed together.
And mules cannot breed together.
So in this way,
They form a kind of barrier between two breeding groups.
There are many other kinds of barrier,
And most living things would not be able to mate with members of other breeding groups or would not try.
Sometimes the line becomes blurred between members of different breeding groups and the word species.
When this happens,
Breeding behaviour is usually the best guide.
For example,
There are two different sorts of foxgloves.
These are smooth-stemmed and hairy-stemmed.
We might think they were two different species,
But they interbreed and are often found in the same population.
In this way,
Their differences are disregarded and smooth and hairy foxgloves are considered to be one species.
The opposite situation occurs when living things look similar but do not interbreed.
For example,
With fruit flies,
They all look so much alike.
They seem to belong to one species,
And yet they do not mate with each other.
These are two breeding groups,
So really they are two different species.
If we were to look very closely at the flies,
We can begin to find very slight differences.
But if we didn't know about their breeding behaviour,
We might have put them in the same species.
So in cases like these,
Breeding behaviour is the best clue to determine the number of species we see.
Of course,
There are always exceptions to the rule.
Sometimes we don't know the breeding behaviour of plants and animals,
So we cannot use this to help us sort them into species.
But often they have so many features in common that we have come to recognise them as one species.
Of course,
We can never have any definite information about the breeding behaviour of extinct living things,
Such as ammonites.
This is true for every fossil,
Even when there are very similar animals alive today.
So breeding behaviour cannot always be used to define species,
But it is the best definition to use,
Because it depends entirely on the way living things themselves behave,
And is never a matter of personal opinion.
Darwin developed his theory from four ideas about species.
And in the next episode,
We will learn about those.
