The greatest show on earth

A. Opening.

1. Captures audience attention.

This is a toy. It’s a collection of Zoo animals.

Here we have… let’s see… gorillas, lions, tigers, crocodiles; all different animals, the flyers, the runners, the burrowers, the swimmers, all wonderfully adapted to their ecosystem, all depending on each other in so a complex manner.

And here you have me, another animal. Am I not?

How this diversity of animals, doing their own thing in their own way, came about?

¿Were they created as they are by a supernatural being?

Well, yes, that was the belief until late nineteen century.

2. Leads into speech topic

But then, something happened which changed our view of our world forever.

·       a book is published in 1859

·       its title (show the book cover):

·       On the origin

·       of species

·       by means of natural selection

·       or the preservation of favoured races

·       in the struggle for life

by: Charles Darwin

Transition

What is this book all about?

B. BODY

1. Main point: There is no external agent, only natural causes

Darwin rejected the notion of an “external agent”. There was a “natural” explanation to this, what someone has called the greatest show on earth.

The theory he devised was called EVOLUTION BY NATURAL SELECTION.

2. Sub point. Artificial selection

Darwin had evidence of evolution by human selection. Dogs and cabbages, pigs and cows have all been changed in a huge way in a very short time, may be a couple of centuries, may be a couple of millennia.

If that change can be achieved in a couple of centuries, just think what can be achieved in ten million years or a hundred million years. That is the sort of time scale we have to play with in dealing with evolution.

2 Main point. Underpinnings of the theory

This theory is based in the following natural facts

1.  variation

2.  heredity

3.  reproductive capacity

Subpoint

Variation

Variation is a vital ingredient for evolution. If there were not variation, there will be only one species.

All living beings are different, even within the same species. We see it in this room.

This diversity gives some individuals and advantage over others to survive and reproduce.

Support material

Let’s think in a group of birds living in a dry land. The land becomes inundated with water. Some of the birds may have legs somewhat longer than others. These have an advantage. Others have beaks a little bit stronger, or a better sight, all these are favoured in the struggle for life in the changed conditions.

Variations, and Darwin didn’t know this, comes from mutations: errors in the mechanism of DNA copying (random mutations).

Subpoint

Heredity

Natural characteristics are inherited.

Darwin didn’t know the mechanism either, although Mendel, before, had already given some explanations.

So, useful variations are amplified by nature. Form long-legged birds, long-legged chicks will be born.

Subpoint

Reproductive capacity

The reproductive capacity of living beings is far greater than the environment can bear.

Support material

Think of elephants, the slowest breeder of all animals. Darwin calculated that, if elephants reproduced to their maximum capacity, at the end of the fifth century, there would be fifteen million elephants alive which will ate 3 billion kgs. of vegetation per day.

Subpoint

Consequences of the struggle for life.

The struggle for life favours the fittest animals. These live longer, have more offspring and pass their characteristics to the next generation.

Speciation is stronger when environmental pressure is higher.

3. Main Point

Evolution is a fact

Evolution is a theory in the scientific sense: coherent group of propositions meant to explain facts about the world.

An assertion for which there is so much evidence that it would be perverse to deny it. A theory becomes fact.

It is a theory because it makes predictions like:

·       simpler forms of life appear on the older layers (prediction). We have a very good fossil record of the horse and the wale

·       If creatures share a common ancestry, we should be able to find transitional forms (prediction)

Example: reptiles and birds. We have found feathered dinosaurs (before birds appear). The entire sequence of the evolution of whales has been found

Support material

We know evolution is a fact

1.  Evolution occurs, populations change over time

2.  Evolution usually happens gradually (hundred to thousands of years)

3.  Speciation occurs: one species splits into two or more species. There are 10 million to 50 million of species on earth

4.  All species share a common ancestry as a result of splitting

5.  Much of the evolutionary change was caused by natural selection, which is the sole process producing adaptation (appearance of design)

4.  Main point

Why evolution is true?

Support material

1.  Fossil record

2.  Retrodictions: embryology, vestigial organs (there may be vestigial genes behind it)

3.  Biogeography. Oceanic islands there are no endemic mammals but plenty of plants, birds and insects!

4.  Bad design: Prostate gland a miracle of bad engineering like running a sewage through a playground

5.  Examples of natural selection. Evolution in the wild: Darwin finches in the Galapagos.

Conclusion

What I would like you to achieve is that when you  wake up in the morning, you notice how wonderful is that:

“After sleeping through a hundred million centuries we have finally opened our eyes on a sumptuous planet, sparkling with colour, bountiful with life. Within decades we must close our eyes again. Isn’t it a noble, an enlightened way of spending our brief time in the sun, to work at understanding the universe and how we have come to wake up in it?

Note: speech Toastmasters Valencia 19/1/12