STAAR Biology Review Categories

Students designed an experiment to model the carbon cycle. The students combined water and carbon dioxide-producing disks in a sealed flask. The flask represented Earth’s atmosphere, and the lamp represented the sun. Their design is shown.

Which component can be added to the flask to reduce the concentration of carbon dioxide in the model atmosphere created by the disks?

• Bacteria to use carbon during nitrification

• Plants to absorb carbon in the process of photosynthesis

• Snails to use carbon through cellular respiration

• Mushrooms to absorb carbon during decomposition

Answer explanation

Plants absorb carbon in the process of photosynthesis.

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In a recent study, scientists investigated the effects of microorganisms naturally found in the body. They raised mice in two different environments and compared their immune system functions in response to a bacterial infection. Their data are shown. Which conclusion about the microorganisms naturally found in the body is most likely supported by these data?

• All microorganisms are harmful to the body.

• Microorganisms are important in promoting healthy

  immune systems.

• All bacteria in the body increase the effectiveness of the immune system.

• Bacteria that cause infections decrease the number and variety of immune cells in the body.

Answer explanation

The microorganisms found in the body are important in promoting a healthy immune system because they keep the immune system strong, aid in digestion, and neutralize toxins.

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White clovers, Trifolium repens, are plants that are native to Europe and Central Asia and are able to produce the poison cyanide within their cells. Skunk cabbage, Symplocarpus foetidus, is a plant that is native to eastern North America and can produce a chemical that makes it have a strong, foul odor and bitter taste. The chemicals produced by both the white clovers and skunk cabbages are adaptations that allow them to —

• attract more pollinators

• survive a long-term drought

• protect against herbivores

• grow better in colder habitats

Answer explanation

The chemicals produced by both the white clovers and skunk cabbages are adaptations that deter animals from eating them, and thus increase their chances of survival.

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Which of these explains the relationship between the leaf-cutter ants and the fungi?

• Predation, because the ants feed on the fungi

• Mutualism, because both the ants and the fungi benefit from

  each other

• Competition, because both organisms consume the same resource for energy

• Commensalism, because the ants receive energy from the fungi and the fungi are unaffected

Answer explanation

The relationship between the leaf-cutter ants and the fungi is mutualism. Both the ants and fungi benefit from each other.

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Some relationships between species found in the Texas Gulf Coast are shown in the food web.

Which energy pyramid best models energy flow in the Texas Gulf Coast community?

• 
• 
• 
• 

Answer explanation

Stone crabs consume gulf pipefish, and gulf pipefish consume aquatic plants.

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In some coral reefs, a symbiotic relationship exists between pygmy seahorses and sea fans. The pygmy seahorse can wrap its tail around the branches of the sea fan. This allows the pygmy seahorse to be camouflaged within the sea fan, protecting it from predators. The pygmy seahorse does not harm or benefit the sea fan while it grasps the branches with its tail. What is the correct classification of this symbiotic relationship?

• Predator/prey

• Mutualism

• Commensalism

• Parasite/host

Answer explanation

Commensalism is the symbiotic relationship that exists. The pygmy seahorse does not harm or benefit the sea fan while it grasps the branches with its tail.

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After a wheat field is cleared, wild grasses and weeds begin growing. This process is considered —

• primary succession because pioneer species appear

• primary succession because there are no large trees

• secondary succession because soil is already present

• secondary succession because the field contains inorganic matter

Answer explanation

After a wheat field is cleared, wild grasses and weeds begin growing due to secondary succession, since soil is already present. Primary succession can only occur in areas where life was not previously present e.g., newly formed volcanic rock.

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During an extended dry season in an area, the majority of the ground cover dried up. Which description best explains how this would affect the ecosystem in that area?

• The ecosystem would become less stable because the ranges of many organisms would expand and overlap.

• The ecosystem would become more stable because there would be less competition among canopy plants.

• The ecosystem would become less stable because less energy would be available to it from the decrease in producers.

• The ecosystem would become more stable because organisms in higher trophic levels would be able to find prey more easily.

Answer explanation

The ecosystem would become less stable if most of the ground cover dried up. Less energy would be available to the ecosystem due to a decrease in the number of producers.

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In a Central Texas grassland, the producers incorporate 12,000 kJ of energy from the sun into their tissues. About how much energy would be incorporated into the tissues of herbivores?

• 12,000 kJ

• 1,200 kJ

• 10,800 kJ

• 1,080 kJ

Answer explanation

Twelve thousand kilojoules (kJ) of energy from the sun is incorporated into the tissues of the producers. Only 10 percent, or 1,200 kJ, of energy is incorporated into the tissues of herbivores when they consume producers.

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An illustration of how a particular DNA mutation will most likely affect the polypeptide produced is shown. What type of mutation is illustrated?

• insertion

• translocation

• substitution

• deletion

Answer explanation

The original strand has a GTA coding for His. The mutated strand has a GGA which codes for Pro instead. The T got switched for a G, so this is a substitution.

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