Natural Selection

Survival of the fittest can best be described as - A. the process by which only the strongest of a species will be able to survive and reproduce B. the process in which organisms that are better adapted to their environment will have a better chance of surviving and reproducing C. the reason the strongest of the species will not be able to reproduce as often as others D. the reason weaker organisms in a species will always be killed by predators

B

Antibiotics have been used to treat bacterial infections since the 1940s. In recent years, many antibiotics have become less effective as resistance to these treatments rises. Which statement below best describes how bacterial resistance to antibiotics demonstrates natural selection? A.The bacteria are able to mutate when they are exposed to antibiotics, allowing the next generation of bacteria cells to have immunity from the antibiotics. B.The antibiotics are becoming weaker because it is harder to find sources for the chemicals that are used in their production. C.The human immune system has become desensitized to the chemicals in antibiotics, which causes the antibiotics to be less effective. D.The bacteria cells that are able to survive the antibiotics reproduce while weaker bacteria die, causing the bacteria population to have more antibiotic-resistant individuals over time.

D

Which of the following best describes the possible result of natural selection? A. changes in the acquired characteristics of a species B. unfavorable changes in a population C. immediate changes in an individual in a population D. changes in the inherited characteristics of a population not that of an individual.

D

What is genetic drift?

A change in allele frequencies caused by random events especially apparent within small breeding populations.

The rock pocket mouse is found mainly in rocky areas of the deserts of the southwestern United States. Most of these mice have light brown fur that allows them to blend in with the desert rocks where they live. However, there is an area of New Mexico with black rock left over from old volcanic eruptions. Scientists discovered that many of the rock pocket mice living on the black volcanic rock have dark fur. What is the best explanation for this phenomenon? A. The dark colored mice survived and passed on their genes to their offspring so that, over time, the population became mostly dark colored. B. The light colored mice began expressing the dark fur gene in order to camouflage themselves from predators. C. The dark colored mice were stronger than the light colored mice and were, therefore, able to fight off predators. D. The light colored mice all experienced the same mutation, which caused them to start producing more melanin and turned their fur a darker color.

A

Which of the following outcomes would you predict for a population of mosquitoes exposed to a new pesticide? A. Over several generations, the mosquitoes would become resistant to the pesticide. B. Over several generations, the mosquitoes would evolve into several new species. C. Over several generations, the mosquitoes would all be killed and become extinct. D. Over several generations, the mosquitoes would be more susceptible to the pesticide.

A

What causes genetic drift?

A change in allele frequency within a population due to random chance. For, example; all brown insects die in a a natural disaster due to a bacterial infection. The green insects are unaffected. The allele for brown colored insects are no longer present in the population leading to a sharp decrease in the allele frequency for brown insects.

What is a population?

A group of individuals of the same species living in the same area that can breed and produce offspring.

What is a mutation?

Accidental change in the sequence of an organism's genetic material. Mutations can occur in any cell of in an organism's body. Mutations that occur in the sex cells of an organism may be passed on to their offspring. Mutations lead to greater genetic variation among the individuals of a species.

What is the founder effect?

An extreme example of genetic drift. A relatively small population without genetic variation becomes reproductively isolated. in which the genetic variation remains significantly reduced and members tend to share many of the traits of the founders of that population.

Organism's with favorable traits.

Are more likely to reproduce and pass on their traits than organisms without such traits. These favorable traits determine or select which traits will continue to exist in that ecosystem.

Antibiotic resistance occurs when an antibiotic has lost its ability to effectively control or kill bacterial growth; in other words, the bacteria are "resistant" and continue to multiply in the presence of therapeutic levels of an antibiotic. Which statement best explains this natural phenomenon in terms of Darwin's theory of natural selection? A.The antibiotics caused certain groups of bacteria to suddenly start producing enzymes that destroyed the antibiotic before it could harm the bacteria. B.When an antibiotic is used, bacteria that have a natural variation for resistance to the antibiotic have a greater chance of survival than those that are "susceptible." C.Although susceptible bacteria are killed or inhibited by an antibiotic, any offspring they produced before they died will be resistant to the antibiotic, as will their offspring. D.The need to adapt or die caused some bacteria to become resistant to the antibiotic. This acquired resistance was passed on to future bacteria making them resistant.

B

Two types of sedge plants grow in the region inhabited by the finches. One plant produces very hard seeds, the other a soft seed. Which statement best explains the relationship between the seed size and the bill width? A.There is no relationship between the bill width size and the hardness or softness of the seed. B.The larger bill width would be best for opening the hard seeds and the smaller bill width would be best for opening the soft seeds. C.The smaller bill width would be best for opening the hard seeds and the larger bill width would be best for opening the soft seeds. D.The smaller bill width can only open the soft seeds but the larger bill can easily open either the soft seeds or the hard seeds.

B

Which of the following described the cause of natural selection? A. Individuals within the population acquire traits to adapt to the environment. B. Some members of the population have greater reproductive success than others. C .Disasters, like fires and floods, kill all members of a population in an area. D. Members of a population compete for limited resources in their environment.

B

According to the theory of evolution by natural selection, which of the following is true? A. Genetic traits that aid evolution are not passed on to offspring. B. Variation does not exist between members of the same species. C. Populations will change over time to better fit their environment. D. No more offspring are born into a population than can survive.

C

What is an adaptation?

Favorable traits that increase an organism's chance of survival in a particular environment.

What is genetic diversity?

Having a wide variety of traits in a population.

What would happen to a population if there was no genetic diversity?

If all organisms within the population were identical, then no organism would have a better chance of survival than any other. A population with little or no diversity is less likely to survive changes in an environment.

What occurs if an organism has the ability to reproduce?

If the organism has an adaptation that allows it to survive then these traits are more likely to be passed down through generations and spread throughout a population.

Some other causes of genetic flow are.

Immigration and emigration

What is immigration?

Movement of individuals into a population. The immigration of individuals A of a population will increase genetic diversity of population B.

What is emigration?

Movement of individuals out of a population. will cause the same genetic variation as immigration.

What are two common sources of genetic variation?

Mutations are responsible for introducing new traits and new versions of existing traits. Sexual reproduction results in offspring having a combination of genetic material from both parents which contributes to genetic variation.

Why does natural selection occur over time?

Natural selection results in changes of a species not an individual but within a population. These changes generally develop gradually, over many generations rather than suddenly. Overtime, favorable traits are likely to increase within a population and unfavorable traits are likely to decrease over time. In this way natural selection plays an important role in the way species evolve over time.

What is natural selection?

Organisms with favorable traits are more likely to thrive, reproduce, and pass their traits on to future generations than an organism without such traits.

Natural selection occurs if the following 4 criteria are met.

Overproduction, a species produces more offspring than will survive to maturity. Genetic diversity, individuals within the species population are genetically slightly different from each other. Struggle to survive, individuals of a population must struggle to access resources;such as water, food, or shelter, and must avoid prey. Successful reproduction, individuals that are successful reproduce and pass their genes on to their offspring.

The sharp reduction in populations due to a major event is known as?

Population bottleneck. The loss of the brown insects is an example of genetic drift because there was no selection involved in the removal of that allele from the population.

What are the two basic criteria that fuels natural selection?

The survival of an organism depends on it's ability to sense and respond to changes in their external environment. The second, organisms with similar needs compete for the same resources such as food, water, and shelter.

What occurs if an organism dies before reproducing?

Then it's unique traits would be eliminated from the population.

What is gene flow?

Transfer of genetic information from one breeding population to another. Genetic flow is an important source of genetic variation when unique genetic information from one population is introduced into a different population. For example, a black colored bull breaks through a fence and begins mating with white colored cows.