Biology Final

What will MOST likely happen to a stable ecosystem when a population of animals exceeds the ecosystem’s carrying capacity?

• The ecosystem will improve.

• The ecosystem will degrade.

• The ecosystem will change type.

• The ecosystem will remain unchanged.

A particular species of snake was accidentally introduced into a region where it had no natural enemies. These introduced snakes fed on birds and insects that were the food of native snake species. Over the next few years, the introduced snake population grew rapidly in size. How will the introduced snakes MOST likely impact the native snake population

• Native snakes will mate with the invaders to form a new species.

• Native snakes will adapt to eating different varieties of food.

• The native snake population will increase as it migrates to new areas.

• The native snake population will decrease as competition for food increases.

A plant gets the energy it needs from the Sun. The plant uses about ten percent of the energy to carry on its life functions. The plant transfers approximately another ten percent of the energy to the consumers in a food chain. What happens to MOST of the remaining energy?

• A. It is recycled bydecomposers.

• A. It is reabsorbed by theSun.

• A. It is released into the ecosystem asheat.

• A. It is stored in soil for lateruse.

Predation helps maintain the stability of an ecosystem. Which statement BEST describes how this garden ecosystem can benefit from the presence of snakes?

• A. The snakes provide an energy source for themoles.

• A. The snakes consume the mice best adapted to theirenvironment.

• A. The snakes eat moles, which allows the population of mice toincrease.

• A. The snakes keep the mice from overpopulating, which could deplete plantresources.

Complete the sentences by selecting the correct words in the correct order. The process being modeled ismostlikely following a disturbance. In years 75 to 100, the population can bestbe described ashavingreached .

• A. natural selection, carryingcapacity

• A. ecological succession, carryingcapacity

• A. ecological succession, dangerously low levels oftrees

• A. forest clearing,extinction

Which process that occurs during meiosis contributes to a germ cell having unique genetic material?

• transcription

• A. replication

• A. crossing over

• A. spindleformation

Approximately one out of ten people of European ancestry have CCR5-Δ32, an allele of the CCR5 gene that is very rare among non-European populations. CCR5 codes for a receptor found on the surface of many T cells. This receptor is missing in individuals who are homozygous recessive for the CCR5-Δ32 allele. What is the MOST likely reason this rare allele appears so frequently in Europeans today?

• A. The allele protected Europeans from a deadly diseaseagent.

• A. The allele protected Europeans from a rare and benignvirus.

• A. The allele is a commonly occurring mutation in the Europeans’genome.

• A. ThealleleislinkedtoanothercommonalleleintheEuropeans’genome.

Two heterozygous tall plants (Tt) are crossed. What are the expected genotypes and percentages of this cross?

• A. TT 50%; Tt50%

• B. TT 25%; tt75%

• C. Tt 25%; TT 50%; tt25%

• D. TT 25%; Tt 50%; tt25%

Sickle cell anemia is an autosomal recessive disorder. If each parent carries one sickle cell allele, what are the chances that their child will have sickle cell anemia?

• 1 in 4

• 2 in 4

• None

• 3 in 4

Biologists have found that a form of deafness is a recessive trait in dogs. If a female dog that is heterozygous for the trait mates with a male dog that is deaf, what percent of their offspring will be deaf?

• 100%

• 50%

• 25%

• 0%