Darwin's Theory of Natural Selection: Overview

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Disruptive Selection: Example, Definition & Graph

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
 Replay
Your next lesson will play in 10 seconds
  • 0:03 Natural Selection
  • 0:41 Darwin's Assumptions
  • 2:35 The Elements of…
  • 3:59 Natural Selection Updated
  • 4:53 How Darwin Changed the World
  • 6:09 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Timeline
Autoplay
Autoplay
Speed Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Robert Turner
In this lesson, you'll be introduced to Charles Darwin and his theory of natural selection. You'll also learn a bit about how his ideas impacted science, popular understandings of human origins, and the debate his theories have sparked.

Natural Selection

The theory of natural selection can be summed up in this way: Conditions of a habitat will naturally select individuals who are best adapted to that specific environment. Those individuals are more likely to grow to adulthood and reproduce. In short, sexual selection will vary according to environmental conditions. Charles Darwin is credited with this theory, though you may be amazed at how much work preceded his revolutionary ideas about the origin of species. Darwin chose the term natural selection to differentiate it from artificial selection, or the intentional breeding of animals to favor particular phenotypic traits.

Darwin's Assumptions

A species is a breeding population of any plant or animal that shares common physical traits. In particular, two members of the same species can mate and produce fertile offspring, while members of different species cannot. For example, blue jays and cardinals are both birds because they have a similar anatomy. However, their markings, nesting habits, and vocalizations (songs) are unique. Further, a female cardinal and a male blue jay may admire each other, but they could not mate to produce offspring. And so we say, blue jays and cardinals represent two different species of birds.

All species evolve from common ancestors over very long periods of time. For example, modern science has revealed that humans and chimpanzees have a common ancestor that separated into two distinct breeding populations, or species, some 8 million years ago. Even more amazing to consider, humans, chimpanzees, and whales all have a common ancestor that lived 60 million years ago.

Darwin didn't have access to the findings of modern science. Nor did he or his colleagues understand that Earth is about 4.5 billion years old. They were also unaware of the genetic science underlying our present-day understandings of evolution. However, Darwin and others were increasingly aware that the fossil record revealed a progression from simple and primitive creatures to ever more complex and diverse plants and animals. So the general idea that species have evolved from primitive ancestors was already making the rounds among the scientifically curious - including Charles Darwin.

One basic step in science is carefully and meticulously gathering data. Darwin's theory of natural selection definitely passes the data test. Over a period of five years, partly on shore and partly aboard the specially outfitted sailing ship, HMS Beagle, Darwin gathered information about plants and animals found around the world. The hypothesis he came up with while there shook the world.

The Elements of Darwin's Theory

We noted that blue jays and cardinals are species of birds. However, since most of us are not ornithologists, we are not likely to note that there is always variation within a species. For example, consider the coat markings of a litter of pure bred Siamese cats. You will notice that while the kittens' markings are similar, they are not identical. That's an example of Darwin's idea of natural variation within a species. For another example, consider the case of identical twins. Identical twins develop from a single zygote (fertilized egg). And even though the twins might be very hard tell apart, there will be slight variations between the two.

Another element of Darwin's theory is heritability. Most species' traits are passed on to their offspring. But, due to variation, some offspring will be better adapted to a species' habitat.

Population Dynamicsmeans that more offspring of a species will be born than are likely to survive long enough to reproduce. In general, population growth exceeds the resources of any habitat - or what we would now call an ecological niche.

The resources of a habitat - edible plant leaves, beetle grubs, or acorns - are finite. At the same time, because of excess offspring and natural variation, Darwin put forth the concept of competition, or the idea that some offspring are more likely to survive than others. And so we can say, as Darwin did, that nature features a struggle for survival.

Natural Selection Updated

In terms of the modern science of genetics, a species exhibits a unique genotype. A genotype is an organism's genetic map, which is its genome. The exterior, observable traits of an organism are called its phenotype. In terms of genetics, each species shares a common genotype that produces a common phenotype. So, in fact, we now know that chimp and human genotypes are 99 percent identical. In short, modern genetic theory can be used to support, modify, and extend Darwin's theory of natural selection. For example, psychologists can apply natural selection principles to the evolution of the brain and nervous system.

To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account
Support