Part I in .NET framework

Drawing QR Code in .NET framework Part I

volution is the process that explains how organisms change over time It s really as simple and as profound as that And in this part, I begin with the very basics: key evolutionary principles, from Darwin s day to today You ll also find a very brief discussion of genetics Why Because the only changes that are important to evolutionary study are genetic ones

1

Understanding what evolution is Introducing the scientific field of evolutionary biology Realizing why evolution is relevant

volution You ve no doubt heard about it, and you ve probably seen a show or two about it on TV, but its significance likely escapes you Watching a bunch of scientists on the Discovery Channel dig in the dirt with little toothbrushes and get really excited about some little bit of bone or a tooth may leave you thinking, Well, yes, those do look like teeth, and they certainly do seem old, but A tooth, you say to yourself, is hardly reason to trade high fives and uncork champagne bottles At times like these, evolution can seem pretty slippery After all, there s got to be more to it than a stray fossilized tooth or bone fragment Well, there is Evolution explains how we (and I m using we collectively to mean all living organisms: you, me, and all other animals; moss, trees, and the roses in your garden; viruses, amoebas, bacteria, and all the other little critters) came to be in all our complexity and variation The reason scientists get excited about fossilized teeth is because findings like these are consistent with what scientists understand about the evolution of life on Earth That single tooth is just one piece of the evolutionary puzzle; thousands more pieces exist All together, those pieces form a picture of our genetic past and a road map that leads from a common ancestor to who, and what, we are today It s a journey over billions of years This chapter gives you an overview of evolution in all its glory: what it is, how it works, and what it does By the end, you may begin to understand what the great evolutionary biologist Theodosius Dobzhansky meant when he wrote, Nothing in biology makes sense except in the light of evolution

Evolution can be defined simply as change through time, and it can refer to anything that changes Languages evolve; tastes evolve; cultures, art forms, and football offense strategy all evolve This book isn t about evolution in general, though, but about biological evolution: the changes, over time, in organisms Biological evolution deals with a very specific type of change through time changes in the frequencies of different genes throughout an entire species, or within a single population of that species, from generation to generation Evolutionary biologists scientists who study evolution just love that stuff Their mission To understand how evolution works (by figuring out what causes changes in gene frequencies) and what evolution does (by figuring out what sorts of things happen when gene frequencies change) The following sections offer a general overview of how evolution works and what it does Parts II and III delve into these topics in a great deal more detail

Back in Charles Darwin s day, a gene was defined simply as the unit of heredity People knew that specific traits, such as blue eyes or red hair, were passed from parent to child, but they didn t know exactly what a gene was or how the process worked Today, we know a lot more: We know about DNA (deoxyribonucleic acid), which is what gets passed from parent to offspring We know that DNA is a long molecule made up of a string of four subunits (four letters); that the order of these letters, commonly called the DNA sequence, stores genetic information; and that a gene is a particular sequence of a particular piece of an organism s DNA We ve developed the chemical techniques that allow researchers to determine the exact sequence of an organism s DNA As a result of this ability to work with DNA, scientists have a much better handle on the details of the evolutionary process What this means and why it s important enough to include here is that by being able to identify the DNA sequence of a particular gene, scientists can measure exactly what genetic changes occur across generations Being able to measure things, especially things like DNA strands, gets evolutionary biologists all goose-pimply (For more information about genes and DNA, head to 3)