Thursday, Dec. 18 - Genetics - Natural Selection

Key Terms

Adaption – Any trait that helps an organism survive and reproduce.

Artificial selection – The process by which humans breed other animals and plants for particular traits.

Natural selection – A process by which organisms that are best adapted to their environment tend to survive.

Speciation – The evolutionary process when new biological species arrive.

Natural Selection

So back to Charles Darwin.  From 1831-1836, he traveled the world collecting observations about the plants and animals he saw and their habitats. He ended up in the Galapagos Islands, each of which has different climates and species on it. One thing he studied in particular were the giant tortoises on the islands and how the tortoises on each island had different shells than the tortoises on all the other islands. In his “Origin,” he presented his theory of natural selection.

Natural selection is the idea that most organisms produce more offspring than are able to survive. They must compete for food, water and space. Some offspring have variations, or traits, that make better able to survive. The survivors reproduce and pass these variation on to their offspring. And so on … until this variation is found in more and more members of the species and the species evolves. Hence, the phrase “survival of the fittest.” These variation in a species are called adaptions. Adaptions help an organism survive.

Adaptions can include:

Camouflage – Which helps an animal hide from predators

Mimicry – The ability of a harmless organism to look like a more dangerous organism. For example, king snakes (not dangerous) often have similar markings to a coral snake (extremely dangerous), so predators are less likely to attack.

Protective coating – Think of a porcupine.

Bright colors – Many poisonous organisms have bright colors, which act as a warning to predators not to eat them.

Predators also have adaptations that help them get food – good eyesight, keen sense of smell, heat sensors, etc.

Artificial selection is when humans breed animals and plants for specific traits, such as disease-resistant crops. We’ve also created new breeds of dogs this way. Think of the goldendoodle.

Speciation

Speciation is the process of a new species arising from a parent population. This can happen in multiple ways:

Allopatric Speciation – When populations of a species become isolated from each other and evolve different traits.

Sypatric Speciation – When populations overlap geographically but still evolve into different species.

Adaptive Radiation – The different species have a common ancestor but have adapted to their environments, creating a new species.