Biology Keystone Practice - Module 2

A student looking through a microscope records observations about a cell. Which stage of the cell cycle has the student described?

• prophase

• anaphase

• interphase

• telophase

Answer explanation

Prophase is the first step of mitosis. The chromosomes become visible and the nuclear membrane dissolves. As it progresses, the spindle fibers elongate and the chromosomes move toward the center of the cell in preparation for metaphase.

Tags

NGSS.HS-LS1-4

Before cellular division, the cell must duplicate its DNA so that daughter cells will contain complete copies of the DNA. Which characteristic of DNA makes it MOST suitable as a molecule for this role?

• DNA is located in the nucleus.

• DNA is a large macromolecule.

• DNA is made of repeating sugar-phosphate subunits.

• DNA is made of two strands of complementary nucleotides.

Answer explanation

The complementary nature of the two strands allows each strand to serve as a template during replication.

Which statement BEST explains how organisms accomplish passing on traits to their offspring?

• Traits are acquired when parents care for their offspring.

• Offspring inherit traits when DNA is replicated during mitosis.

• Traits are inherited by the transfer of genetic material from parent to offspring.

• Offspring acquire traits when cells become specialized for certain functions.

Answer explanation

DNA is the genetic material transferred from parent to offspring, and it codes for an organism’s inherited traits.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

During a cell division cycle, chromosome segments from two homologous chromosomes exchange places. Which result is MOST LIKELY to occur following this cycle?

• Genetic material will be lost.

• The number of chromosomes will increase.

• The total number of genes in the cell will decrease.

• A change in gene location will occur on both chromosomes.

Answer explanation

According to the Keystone - translocation is an exchange of pieces of homologous chromosomes.

Note: This is incorrect. The question described "crossing over". Translocation occurs between 2 NON-homologous chromosomes.

Although correct, "A change in gene location will occur on both chromosomes" was the BEST choice.

Tags

NGSS.HS-LS3-2

Which statement BEST describes how organisms use DNA and amino acids to synthesize a protein?

• DNA is transcribed into mRNA, which is translated by the ribosome to produce an amino acid chain.

• DNA is translated into mRNA, which is transcribed by the ribosome to produce an amino acid chain.

• Amino acids are transcribed into mRNA, which is translated in the nucleus to produce a molecule of DNA.

• Amino acids are translated into mRNA, which is transcribed in the nucleus to produce a molecule of DNA.

Answer explanation

The first step to protein synthesis is called "transcription". DNA is used as a template to build a complementary strand of mRNA that will take the DNA code to the ribosomes.

Tags

NGSS.HS-LS1-1

Which mutation would most likely affect the organism’s phenotype?

• AUG–GCC–UGU

• AUG–GCG–UGU

• AUG–GCU–UGA

• AUG–GCU–UGC

Answer explanation

The original sequence codes for Cys, while the mutated sequence codes for a stop. This could result in a change in the organism’s phenotype.

Tags

NGSS.HS-LS1-1

NGSS.HS-LS3-1

NGSS.HS-LS3-2

Two closely related shrimp species have habitats and niches that partially overlap. Which factor most likely caused the divergence of the shrimp into separate species?

• reproductive isolation

• reduction of food supply

• a series of rapid mutations

• large initial population size

Answer explanation

Shrimp that occupy separate habitats and niches are more likely to reproduce with nearby shrimp, eventually leading to speciation.

Tags

NGSS.HS-LS4-2

NGSS.HS-LS4-5

The diagram shows the forelimbs of three animals. Which statement BEST describes the bones in the animals?

• All organisms on Earth have the same bones.

• Different bones in similar species serve the same function.

• The species that are the most evolved have the longest bones.

• Similar bones in different organisms may have different functions.

Answer explanation

These are called homologous structures and are evidence that different species share a common ancestor.

Tags

NGSS.MS-LS4-2

Which sequence BEST orders ecological categories from the one with the fewest number of individuals to the one with the greatest number of individuals?

• ecosystem, population, community, biome

• population, community, ecosystem, biome

• biome, population, community, ecosystem

• community, biome, population, ecosystem

Answer explanation

Populations of different species interact in communities, communities of organisms interact with abiotic factors in an ecosystem, and similar ecosystems in a large area make up a biome.

Energy pyramids describe food and energy relationships within an ecosystem. Which factor MOST LIKELY limits the number of levels an energy pyramid can have?

• biomass of the top-level organisms

• predation by the top-level organisms

• energy loss between each level of organisms

• chemical energy being decomposed at each level of organisms

Answer explanation

The number of levels in an energy pyramid is limited by the amount of energy available for the next level of consumers. Only 10% of energy is passed from level to level.

Tags

NGSS.HS-LS2-3

NGSS.HS-LS2-4