Natural Selection ACP Review

Natural Selection

Descent with Modification and Common Descent

● Offspring descent with modifications from their

parents

● Differences found in offspring are partially due to

random mutations

● All living things are related

Multiple Choice

Mutations are important because they bring about

• death of the organism in which they develop
• genetic variation needed for a population to evolve
• benefits for the individual, not for the population
• Hardey-Weinberg equilibrium within a population

Multiple Choice

Which best describes the role of mutations in natural selection?

• Mutations help an organism to better survive in their environment

• An organism may acquire a helpful mutation by interacting with the environment

• A mutation may result in a beneficial trait that makes an organism more likely to survive and reproduce

• Organisms with certain traits are more likely to win competitions for mutations

Charles Darwin (1809-1882)

● Naturalist/explorer
● Came up with the concept of NATURAL

SELECTION

● Noticed that island species were unique to their island

but similar to their mainland

● Darwin believed that similarities could be best

explained through common descent

● Island species were specially adapted for island life

Multiple Choice

Charles Darwin observed that finches of different species on the Galápagos Islands have many similar physical characteristics, this supports the hypothesis that these finches

• are twins

• acquired traits through use and disuse.

• all eat the same type of food.

• descended from a common ancestor.

Selective (artificial) Selection

● Farmers select for certain “desirable” traits to be

continued onto the next generation

● Small selection of traits over many years/ long period

of time will accumulate and create a “new” variation,
traits, or adaptations for that species (plant, animal,
living organism)

● “New” species will emerge(over time) with those specific

traits that are best suited for that environment

Natural Selection

● Parents will randomly produce a variety of offspring

(only some will survive)

● Nature by being hard to live in “decides”/SELECTS

which organisms live or die

● Organisms that survive will reproduce and pass on those

beneficial traits (adaptations) onto the next generation

● “Survival of the fittest” (the most “fit” survive and

reproduce)

Multiple Choice

A large population of rock pocket mice with various fur colors lives in a designated area. Soon after a volcanic eruption, the number of mice with dark-colored fur in the population increased. Which statement BEST describes the reason for the change in fur color?

• Mutations for dark-colored fur were passed down within the somatic cells, resulting in more mice with dark-colored fur.

• Mice with light-colored fur selected mutations that allowed their fur to become darker

• The fitness of mice with dark-colored fur increased, so they became more abundant.

• Mice with light-colored fur began feeding in the daytime to stimulate the release of a pigment for dark-colored fur.

Multiple Choice

Where the better adapted organisms survive to pass traits along to offspring.

• Evolution
• Natural Selection
• Extinction
• Artifical Selection

Multiple Choice

Why are advantageous traits more likely to be passed onto offspring?

• Because they are more likely to survive and reproduce.
• Because they come from dominant alleles.
• Because they come from recessive alleles.
• Because the trait is an acquired phenotype.

Natural Selection Definition

The process by which random evolutionary changes are
selected for by nature in a consistent, orderly, non-random
way

Adaptations are ALWAYS good !!!= SURVIVAL

Multiple Choice

Definition: adaptation

• inherited characteristic that increases chances of survival
• organisms with traits well suited to their environment survive and reproduce at a greater rate
• a growing population causes a scarcity of resources
• differences in the DNA sequence

Multiple Choice

The white cattail is a hybrid species of plant that is a result of the cross between the broad-leaved cattail and the narrow-leaved cattail. Over time, the white cattail has established itself in the wetlands of Midwestern states. Which of these explains the success of the white cattail?

• Favorable genes from parental generations provide advantageous characteristics to the hybrid species.

• Hybridization produces offspring traits that allow different species to survive in extreme environments.

• Inherited traits passed on from parental generations make hybrid species more susceptible to disease.

• Hybrid species display more adaptations due to their reduced genetic diversity.

Multiple Choice

Organisms of the same species can no longer interbreed therefore creating two species.

• Gene Pool

• Genetic Drift

• Gene Frequency

• Speciation

Multiple Choice

A student compares two different species of fox as shown in the table.The student wants to explain why the two species are so different even though they have a common ancestor. Which statement BEST explains the differences between the two species?

• Different environments led to different adaptations

• The same environment led to different adaptations

• Each species developed the same adaptations to different environments

• Each species migrated to environments that matched their adaptations

Types of Natural Selection

● Disruptive
● Stabilizing
● Directional

Disruptive Selection

● Extreme variations of the traits are selected for (by nature)
● The “average” or “moderate” traits are selected against

Extreme Trait

Extreme Trait

Red line- Before the selection
Blue line- AFTER the selection

Stabilizing Selection

● Opposite of disruptive selection. Favors

(nature)the middle traits

Red line- Before the selection
Blue line- AFTER the selection

Directional Selection

● One of the extreme traits is selected for, moving

the population toward that phenotype

Red line- Before the selection
Blue line- AFTER the selection

Extreme Trait

Multiple Choice

Average phenotypes are favored in the environment, while extremes have lower survival rates.

• seasonal selection

• distruptive selection

• directional selection

• stabilizing selection

Multiple Choice

Over the years, white mice became extinct and darker mice survived. This is

• stabilizing selection

• directional selection

• disruptive selection

• due to exercise

Multiple Choice

Starting in 1954, commercial fishers in the northwest Pacific were paid by weight, rather than by the individual fish, for pink salmon. The fishers increased the use of a type of net that selectively catches larger fish.  Which of the following effects did this change in fishing technique most likely have on the salmon population over the next 20 years?

• The average body size of the salmon population decreased significantly.
• The average body size of the salmon population increased significantly.
• The average body size of the males in the salmon population increased, and the females stayed the same.

Multiple Choice

Robins typically lay fours eggs. If more then four eggs are produced then the baby chicks are malnourished while smaller egg numbers result in no viable (able to live) baby chicks. This is an example of

• stabalizing
• disruptive
• direction
• none of the above

Last thing…

Multiple Choice

Punctuated equilibrium is a theory of evolution that suggests species experience long periods of stability, interrupted by short, rapid changes. Which of the following statements best describes punctuated equilibrium?

• Evolution occurs slowly and steadily over time, with small changes happening continuously.

• Species remain unchanged for millions of years and then undergo sudden, rapid changes in a short period.

• Evolution happens rapidly in a continuous, smooth process.

• Species evolve due to the gradual accumulation of mutations over time, without any long periods of stability.