What is Needed for Natural Selection Summary Questions

Be able to answer the following questions:

1. What three things need to be present for natural selection to occur?
2. Why is natural selection called the “survival of the fittest”?
3. Give an example of how camouflage can be advantageous.
4. Construct an explanation for why this population of owls is seeing a rise in brown feathers over gray and compare it to your original explanation.

Natural Selection and Influences

Natural Influences explain how organisms in a population develop traits that allow them to survive and reproduce.

• These traits will most likely be passed on to their offspring.
• Take the giant tortoises on the Galápagos as an example.
  • If a short-necked tortoise lives on an island with fruit located at a high level, will the short-necked tortoise survive?
  • No, it will not, because it will not be able to reach the food it needs to survive.
  • If all of the short-necked tortoises die, and the long-necked tortoises survive, then over time only the long-necked trait will be passed down to offspring.
  • All of the tortoises with long necks will be "naturally selected" to survive.

Every plant and animal depends on its traits to survive.

• Survival may include getting food, building homes, and attracting mates.
• Traits that allow a plant, animal, or bacteria to survive and reproduce in its environments are called adaptations.

Natural selection occurs when:

1. There is some variation in the inherited traits of organisms within a species.
2. Some of these traits will give individuals an advantage over others in surviving and reproducing.
3. These individuals will be likely to have more offspring.

 Survival of the Fittest

Some people refer to natural selection as “survival of the fittest.”

• This does not refer to the fastest, strongest, or biggest but rather to the organism that is most “fit” for their environment.
• Both predators and prey have adaptations that help them survive in their environment.
  • Predator adaptations help them capture prey.
  • Prey adaptations help them avoid predators.
• A common adaptation in both predator and prey is camouflage, the ability of an organism to blend in with its environment because of its inherited traits.

Imagine how in winter, dark fur makes a rabbit easy for foxes to spot and catch in the snow.

• Natural selection suggests that white fur is a beneficial trait that improves the chance that a rabbit will survive, reproduce and pass the trait of white fur on to its offspring.
• Over time, dark fur rabbits will become uncommon. Rabbits will adapt to have white fur.
• In winter, the fur of Arctic hares turns white.
  • The camouflage may make it more difficult for fox and other predators to locate hares against the white snow.

Can you see the crab in the photo on the left? It is camouflaged with algae. The praying mantis in the middle photo looks just like the leaves in the background. Can you tell where one zebra ends and another one begins? This may confuse a predator and give the zebras a chance to run away.

Putting It Together

Think back to the Tawny Owl living in the rising temperatures of Finland.

• Construct an explanation for why this population of owls is seeing a rise in brown feathers over gray and compare it to your original explanation.