Biology Keystone

Energy pyramids describe food and energy relationships within an ecosystem. Which factor most likely limits the number of levels an energy pyramid can have? A. biomass of the top-level organisms B. predation by the top-level organisms C. energy loss between each level of organisms D. chemical energy being decomposed at each level of organisms

C. The number of levels in an energy pyramid is limited by the amount of energy available for the next level of consumers.

Which statement best describes a direct role of ATP in a paramecium? A. ATP provides the energy to move cilia. B. ATP stores the genetic code for replication. C. ATP signals the presence of other nearby organisms. D. ATP senses changes in the surrounding aquatic environment

A. ATP is the primary molecule of energy transfer in a cell.

Plants are dependent on water. In most plants, water is absorbed by the roots and then moves up the stem of the plant and into the leaves by capillary action. Which properties of water are most responsible for the capillary action in plants? A. adhesion and cohesion B. low density and adhesion C. polarity and high specific heat D. high specific heat and cohesion

A. Capillary action is the result of hydrogen bonds forming between water molecules and the water molecules being attracted to the molecules inside the stem.

Which statement best describes how organisms use DNA and amino acids to synthesize a protein? A. DNA is transcribed into mRNA, which is translated by the ribosome to produce an amino acid chain. B. DNA is translated into mRNA, which is transcribed by the ribosome to produce an amino acid chain. C. Amino acids are transcribed into mRNA, which is translated in the nucleus to produce a molecule of DNA. D. Amino acids are translated into mRNA, which is transcribed in the nucleus to produce a molecule of DNA.

A. DNA into mRNA is transcription, and mRNA into amino acids is translation.

chromatin has condensed into visible chromosomes • nuclear envelope has disappeared • nucleolus is no longer visible A student looking through a microscope records observations about a cell. Which stage of the cell cycle has the student described? A. prophase B. anaphase C. interphase D. telophase

A. During anaphase, spindle fibers pull sister chromatids apart toward opposite centrioles. During interphase, DNA is spread out as chromatin, so individual chromosomes are not visible because the nucleolus is clearly visible. During telophase, nuclear envelopes begin to form around the two new nuclei at opposite poles, and evidence of cytokinesis may be visible

Which property of water is most responsible for plants being able to transport water from their roots to their leaves? A. the attraction between molecules B. a capacity to dissolve many substances C. the ability to form a low-density crystalline structure when frozen D. a capacity to absorb large amounts of energy as temperature increases

A. Hydrogen bonds form between water molecules, and capillary action draws the water up the roots and stem to leaves.

How does a mitochondrion facilitate the movement of some materials between cells? A. It supplies the energy needed for moving molecules through membranes. B. It manufactures the proteins needed to form channels in cell membranes. C. It supplies digestive substances that break large molecules into smaller units. D. It produces fibers that attach to molecules and move them through the cytoplasm.

A. Mitochondria convert glucose to ATP, the primary molecule of energy transfer for cells.

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? A. reproductive isolation B. reduction of food supply C. a series of rapid mutations D. large initial population size

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

Which process best describes the assembly of proteins from amino acids? A. Atoms are linked to form a compound. B. Monomers are linked to form a polymer. C. Atoms are added to a monomer until it becomes a polymer. D. Molecules are added to a compound until it becomes a monomer.

B. Amino acids are monomers that link together to form complex protein polymers.

Which statement best describes a function of the proteins embedded in the plasma membrane of cells? A. They provide instructions for the processes in the cell. B. They selectively allow certain particles into and out of the cell. C. They attract charges in the cell's environment to give the cell a net charge. D. They store the energy required by the rest of the membrane to perform its functions.

B. Channel proteins and protein pumps regulate the movement of materials, such as gases and nutrients, across the plasma membrane

Which statement best compares a carbohydrate and a nucleic acid? A. The sequence of monomers in a carbohydrate stores genetic information, and the bonds in a nucleic acid store energy. B. The bonds in a carbohydrate store energy, and the sequence of nucleotides in a nucleic acid stores genetic information. C. A carbohydrate has a unique structure to assist diffusion across a plasma membrane, and a nucleic acid has a unique structure to assist chemical reactions. D. A carbohydrate has a unique structure to assist chemical reactions, and a nucleic acid has a unique structure to assist diffusion across a plasma membrane.

B. Energy is stored in the bonds of carbohydrates such as glucose. The genetic code of DNA is determined by the sequence of nucleic acid monomers called nucleotides

Lungs and capillaries both have porous linings that allow certain substances to move into or out of the structures. Which function do these porous linings most likely serve in living organisms? A. heat release B. gas exchange C. carbohydrate absorption D. osmotic pressure regulation

B. Oxygen and carbon dioxide molecules are transferred into and out of capillaries in the lungs.

Which sequence best orders ecological categories from the one with the fewest number of individuals to the one with the greatest number of individuals? A. ecosystem, population, community, biome B. population, community, ecosystem, biome C. biome, population, community, ecosystem D. community, biome, population, ecosystem

B. 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.

Each cell in the human body contains thousands of different enzymes responsible for regulating reactions within the cell. Which statement explains why a single enzyme is unable to regulate a variety of reactions? A. The binding of a product and an enzyme is specific. B. The binding of a substrate and an enzyme is specific. C. The enzyme is consumed by the products of the reactions. D. The enzyme is consumed by the substrates of the reactions.

B. The active site on an enzyme fits only a specific substrate.

Which of the following is essential to proper functioning of all prokaryotic and eukaryotic organisms? A. O2 B. CO2 C. ATP D. NaCl

C. ATP-ATP is the essential molecule for transferring chemical energy within all cells.

Which statement best explains how organisms accomplish passing on traits to their offspring? A. Traits are acquired when parents care for their offspring. B. Offspring inherit traits when DNA is replicated during mitosis. C. Traits are inherited by the transfer of genetic material from parent to offspring. D. Offspring acquire traits when cells become specialized for certain functions.

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

What is the main purpose for initiating the production of folding helpers in a cell? A. DNA replication B. forming gametes C. passive transport D. maintaining homeostasis

D. "Folding helpers" ensure the correct folding of proteins to return the plant to normal operating conditions, which is homeostasis.

The element carbon has multiple bonding patterns. Which bonding pattern cannot be formed by carbon? A. C—C B. C—C—C C. C∙C∙C D. C≡C≡C

D. Carbon has only four valence electrons and the pattern shown would require six valence electrons.

Which statement best compares eukaryotic cells and prokaryotic cells? A. Eukaryotic cells are smaller than prokaryotic cells. B. Prokaryotic cells are more complex than eukaryotic cells. C. Prokaryotic cells contain a distinct central organelle, and eukaryotic cells do not. D. Eukaryotic cells contain membrane-bound organelles, and prokaryotic cells do not.

D. Membrane-bound organelles such as the nucleus, mitochondria, and chloroplasts are not found in prokaryotes.

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? A. DNA is located in the nucleus. B. DNA is a large macromolecule. C. DNA is made of repeating sugar-phosphate subunits. D. DNA is made of two strands of complementary nucleotides.

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

Orchids living in tropical rainforests often grow on the branches of trees to access sunlight. The trees are not affected by the orchids. Which term best classifies the relationship between the orchids and the trees? A. predation B. parasitism C. competition D. commensalism

D. The orchids benefit from the trees without harming them.

The diagram shows the forelimbs of three animals. Which statement best describes the bones in the animals? A. All organisms on Earth have the same bones. B. Different bones in similar species serve the same function. C. The species that are the most evolved have the longest bones. D. Similar bones in different organisms may have different functions.

D. This is the definition of homologous structures.

During a cell division cycle, chromosome segments from two homologous chromosomes exchange places. Which result is most likely to occur following this cycle? A. Genetic material will be lost. B. The number of chromosomes will increase. C. The total number of genes in the cell will decrease. D. A change in gene location will occur on both chromosomes.

D. Translocation is an exchange of pieces of homologous chromosomes.