Evolution Under Pressure: How We Change Nature and How Nature Changes Us
How Selection Drives Evolution Natural and Not-So-Natural Chapter one 4
Evolution is the gradual development of something simple into something more complex like your science project chang ing from a page of notes into a multimedia presentation with slides a light show and an exploding volcano Depending on who you ask you your teacher or the classmate who got covered in a slimy mix of vinegar and baking soda one is not necessarily better than the other but one is definitely more complex You could say the presentation evolved from the notes just like the notes evolved from a blank piece of paper It’s important to remember that the page of notes you worked so hard to create still exists It could survive for a long time as is in a box of school treasures or it could evolve into something else an essay an exam study sheet or the lining of your hamster’s cage When we apply this idea of evolution to the development of life on Earth it’s often seen as a line with a beginning and an end we started as apes monkeys fish choose your ancestor and ended up as perfectly evolved humans The problem It’s not that simple Things actually started way before apes monkeys and fish with a stew of chemicals and molecules most of us would not consider life From there single-celled organisms with the ability to reproduce emerged As these single-celled organisms multiplied changes occurred by random chance This led to variation eventually resulting in every organism we share the planet with today 5
Where do these random changes happen In the genes bits of instruction inside each cell that determine how a living crea ture will develop function and reproduce These instructions are made of DNA deoxyribonucleic acid Just like English is written using a code of twenty-six letters genes are written with four letters or bases of DNA When a living creature reproduces it passes on the genes in its instruction man ual to the next generation by copying and packaging all those DNA bases into the nucleus of a new cell This is how the next generation begins with a single cell and a genetic instruction manual on how it can grow up to be just like its parent by making more and more cells But even the offspring of single-celled organisms can turn out different than their parent Why Mistakes are sometimes made in the copying of DNA Like a spell ing mistake changing one of the letters in a gene’s code often called a mutation can change how the instructions are read Gene Mutations 6 EVOLUTION UNDER PRESSURE
