#24 What is Evolution Part 3 of ? What is meant by natural selection?

Evolution is change over time in its most basic description. The first question seems to be how does that change occur. This is where Darwin's Big Idea comes in... Natural Selection.

Natural selection has four main concepts that define how selection happens. Selection is just a fancy word for the species or varieties or populations that survive and continue on. Natural Selection means that those creatures that are best suited based on these four principles will be "selected" to survive and continue on.

Natural selection works on populations and species as well. It can be affected by interactions of members within the same species (say a cheetah who is faster than its neighboring cheetahs may catch more food and therefore more of its offspring survive) or between different species (say competition between two bird species for insects or the faster zebras leaving more offspring because they are better suited to outrunning predators).

1. Struggle for existence.

- More individuals are produced than can survive. All members of a population or species must compete for food, water, space, mates, etc.

This seems logical when you think about it since the same species is looking for the same food, same nest sites or same territories, etc. So which members survive? The members that are best suited for finding food, evading predators, raising young, catching prey, attracting mates or whatever it may be will leave the most offspring. If you leave more offspring more of your genes and genetic material make it to the next generation.

2. Variation

- Variation exists between individuals in a species or population and this variation plays an important role in the struggle for existence.

There are quite a few examples of how variation is helpful. The classic example is the Peppered Moth. Originally, this moth lived on tree that were mottled and greyish white. The white moths blended perfectly into the bark. However, sometimes black individuals were born. These black individuals were very visible on the white tree trunks and therefore eaten by birds. In this situation the white moths are better suited for the environment than the black... the white are better at winning the struggle for existence.

Enter man and the industrial revolution. With the introduction of coal burning soot began to cover and darken surfaces, including the tree bark. Now the black moths were better suited for hiding and the white moths were easy to find. Birds ate the white moths that they could see on the tree bark. The black moths, due to environmental change, had become better at the struggle for existence.

Currently, with clean air technology and laws the surfaces are once again lighter colored. Guess which moth color is better at surviving now? That's right, the white ones.

Prior to the industrial revolution.

During the Industrial Revolution

#3 Adaptation.

- This is a heritable trait, i.e. something in the genetic code, that increases an organisms ability to survive and reproduce.

Lets play a game... which snake pictured below is the venomous coral snake and which is the harmless milksnake?

Would you want to take the time to try and guess if you knew there was a red, black and white/yellow snake around that could kill you? This is a case of mimicry. The non-venomous snake which had a pattern similar to the venomous snake was avoided. That avoidance means it survived longer and its similarly patterned offspring could survive longer and produce more offspring. This adaptation of looking like a venomous or poisonous counterpart is very common in the animal kingdom. There are many kinds of adaptations mimicry is just one of them.

Oh and if you are curious the second one is the non-venomous milksnake. Would your guess have killed you?

#4 Survival of the Fittest

Before we get into survival of the fittest lets define some words:
Fitness is how well an organism survives and reproduces.
Survival is the ability to pass heritable traits to offspring.

So one way to think about Survival of the Fittest is... Individuals with the best adaptations and variations will be the most successful at the Struggle for Existence. The success will give those individuals the highest fitness and the best survival.

Does this mean that an animal is perfectly suited to its environment or perfect for its environment?  

NO. What it means is that of all the possible variations a species could possess the ones we see most commonly are the best for surviving in the current environment. If that environment changes the types of variations and adaptations needed to survive may change. Some people describe it as "just good enough to flourish". Which means the traits an individual, population or species has is just good enough for that species to flourish, continue surviving, in the current environment. The individual has just enough of an edge on the environment to survive.

So what is Natural Selection really?

Natural Selection occurs when there are heritable traits (variations and adaptations) that cause variations in a population that has more individuals born than are expected to survive. (And this survive here usually means surviving to reproductive maturity.)

This is one of the mechanisms for evolution.

What to try your luck at survival of the fittest? Go here and click on Play the Survival Game.

#23: What is Evolution? Part 2 of ? Who was Darwin?

Before we can talk about the theory of evolution I think it is important to address who the man was.

Charles Darwin was a naturalist who loved bird watching. This is one of the reasons that he often studied pigeons during his research. Most of his observations as a naturalist took place while traveling on ships as the ship's naturalist. Traveling as part of a ships crew was a very common way for scientists to get out and see the rest of the world. Darwin's most renowned voyage was from 1831-1836, at the age of 22, on the HMS Beagle.

Map of the Beagle voyage

 While on this voyage Darwin started to ponder many of the thoughts that would later be worked into the theory of evolution. I am not going to go into great detail on Darwin's notes, he was a copious note taker, however, you can read them Here.


For Darwin, seeing the world and all its inhabitants was life changing.  His big revelation was that biology and evolution can explain how modern organisms evolved over long periods of time from a common ancestor. What we call the Theory of Evolution is all the varied pieces of explanation that Darwin deduced as he tried to figure out how the organisms had changed over time.

Darwin's Theory of Evolution is not one theory but a series of theories and laws that support and give proof for the concept that we call evolution. The theory of evolution includes concepts that we are familiar with, or if you are not we will be addressing in upcoming posts, such as Natural Selection, Mutations, Speciation, and many others. We will get into each of these in the next few posts.



More of Darwin's works:
His Manuscripts
His publications
Creation. This movie is a very good piece of historical fiction about Darwin's work on the Theory of Evolution  
The Movie Creation is currently up on Vimeo to watch in full
Stuff on PBS about Darwin

#22: What is Evolution? Part 1 of ? The Scientists

This isn't an easy question to answer especially if you want to address it in full. Instead of jumping into evolution right away I thought it would be good to start with the scientists and science discoveries that lead up to Darwin's theory and/or whose discoveries were integral to the development of the theory of evolution.

James Hutton (1785)
James Hutton was a geologist who studied Earth processes. He discovered that the Earth's surface was capable of twisting and wearing away. In addition, Hutton proposed that this change was slow and over long periods of time due to activity like volcanic eruptions and rain weathering. He was also the first to think of Deep Time or the concept that the Earth is so old that it is hard (impossible?) for a human to imagine. More on James Hutton, considered the Father of Modern Geology.

Thomas Malthus (1798)
Malthus was an economist that reasoned, if human population grew unchecked that there eventually wouldn't be enough resources to survive. Darwin used this concept heavily in his process of defining how populations might exist over time. More about Thomas Malthus.

Jean-Baptiste Lamarck (1809)
Lamarck was a naturalist who believed that organisms could change during a lifetime by using or not using body parts. His paper on how individuals pass on traits to offspring and facilitating change over time was published the year Darwin was born. Lamarck also thought that organisms had an inborn drive to become more complex. More about Lamarck   and About the difference between Darwin and Lamarck's views on evolution.

Charles Lyell (1830-1833)
Lyell developed the concept of Uniformitarianism. This concept is that the laws of nature are constant over time. What this means is that those events we see now; volcanoes, rivers cutting valleys, erosion, etc must have been occurring in the past. Fun fact: Darwin read Lyell's "Principles of Geology" while on the HMS Beagle. About Charles Lyell and how he came to Uniformitarianism