Traits that Affect Survival Summary Questions

Be Prepared to answer these questions:

1. What is natural selection (from last chapter)?
2. What three ways do some scientists use as evidence of change over time (evolution)?
3. Give an example of an organism that is best fit for its environments.
4. Where does much of the variation come from in a population and what three ways can it affect the population?
5. Give examples of both structural (size,shape, or color) and behavioral (actions) adaptations that can help an organism become more fit for the environment.

Unit 6: Changes in Species over Time

Developing Traits that Affect Survival

Genetic variation and the proportion of traits within a population can change over time.

• Additional evidence of change over time can be found in the fossil record, anatomical similarities and differences between modern and ancient organisms and in embryological development.

Temperatures in Finland, a country near the North Pole, have been rising in recent years.

• Tawny Owls in Finland used to be found most often with gray feathers.
• In the last 30 years, brown feathers have become more and more common in the Tawny Owl.

The genetic variation of traits in a population can affect some individuals' probability of surviving and reproducing in a specific environment.

• Over time, specific traits may increase or decrease in populations.
  • Examples could include camouflage, variation of body shape, speed and agility, or drought tolerance.

There are many different environments in which living things inhabit all across the world.

• The environments helped to shape the traits of the organisms that live in them.
  • For example, the harsh heat of the desert influenced the traits of the cactus while polar bears have adapted to living in the arctic.
• In this chapter see if you can identify additional cause and effect relationships between an organism’s traits and the environment in which it lives.

Adaptation and Evolution of Populations

Look at the picture of the moth. (Yes, there is a moth) Why would an organism match its background?

• An organism that blends with its background is more likely to avoid predators.
  • If it survives, it is more likely to pass on this beneficial trait to its offspring.
• This moth appears to be well adapted to its environment.
  • It is less likely to be eaten by a bird than a dark colored moth on the tree.

Variation and Adaptation

Even though they may look very similar, most organisms of the same species have some physical differences.

• This is because their genes are different.
• These differences in traits are called variations.
  • For example, there are lots of variations in the color of human hair.
  • Hair can be blonde, brown, black, or even red.
  • Hair color is a trait determined by genes.
• At some time in the past, a variation probably came from a mutation.
  • Mutations are natural changes to DNA.
• Some are harmful, but many are neutral and some are beneficial.
  • If a mutation is harmful, the organism may not live long enough to reproduce.
  • If the mutation is beneficial, that organism may have a better chance to survive.
• An organism that survives is likely to have offspring.
  • If it does, it may pass the mutation onto its offspring.

Genetic mutation is central to the creation of biological diversity.

Traits that help organisms survive are called adaptations.

• Many adaptations protect organisms from the external environment.

Cacti have thick, water-retaining bodies that help them conserve water.

Poison dart frogs have toxins in their skin.

• Their bright colors warn potential predators not to take a bite!

 How Adaptations Develop

Think about a population of oak trees.

• Imagine that a fungus has arrived from Asia to North America.
  • Most of the North American oak trees are killed by the fungus.
  • But a few oak trees have a mutation in their DNA that gave them the ability to survive the fungus.
• Those oak trees are better adapted to the new environment than the others.
  • Those trees have a better chance of surviving.
• They will probably reproduce and their offspring may inherit that favorable mutation.
  • The other trees that do not have this mutation will die.
• Eventually, the population of oak trees will change so that most trees will have the trait to survive the fungus.
• This is an adaptation.
  • Over time, traits that help an organism survive become more common.
  • Traits that hinder survival eventually disappear.

Other adaptations help an organism move or gather food.

• Reindeer have sponge-like hooves that help them walk on snowy ground without slipping and falling.
• Fish at the bottom of the ocean are tiny and use very little energy because there is very little food.
• Organisms have special features that help them avoid being eaten.
  • Some plants have poisonous or foul-tasting substances in them that keep animals from eating them.
  • Their brightly colored flowers serve as a warning.
  • Skunks release a nasty odor to protect them from predators.