Biology STAAR 2017

1 The picture shows a student using a microscope to study a prepared slide of a single-celled organism.

A single-celled organism can be classified as a prokaryote based on the absence of —

• a cell membrane

• ribosomes

• chromosomes

• a nucleus

Different types of mutations can occur in DNA. The diagram represents a type of mutation.

Which statement describes the mutation in the diagram?

• A silent mutation results in the insertion of a different amino acid.

• A substitution occurs with the adenine base.

• A deletion of a cytosine base occurs.

• A base is inserted into one strand of the DNA.

3 A remora is a fish that has an adhesive disk on the back of its head that it uses to attach itself to a large shark. When food floats away from the shark’s mouth as it feeds, the remora collects the scraps. Drawings of a shark with a remora attached and a remora’s adhesive disk are shown below.

The relationship between the remora and the shark is an example of —

• predation

• parasitism

• commensalism

• competition

4 Invasive plant species affect the interactions of living and nonliving components of an ecosystem, so the removal of invasive plants is often necessary. The goal of most plant-control methods is to disrupt or inhibit the function of different plant systems. For example, insects can be used to chew through roots in order to reduce a plant’s ability to absorb water.

Which of these functions would be most immediately affected by a reduction in water uptake by roots?

• Disease resistance

• Seed dispersal

• Sunlight absorption

• Photosynthesis

5 The picture shows a pika, a small mammal found in grassland ecosystems. The vast grasslands of the Tibetan plateau are home to the plateau pika. The numerous pikas are prey for many predators of the grasslands, which serve as a major watershed for much of the area. The watershed drains large quantities of groundwater during the rainy season, or the monsoon season. Pikas have extensive burrows that help drain groundwater rapidly and are used as nesting sites by many bird species. However, many people advocate the eradication of the plateau pikas because they compete with livestock for grass.

Which of these will most likely happen if the plateau pikas are completely removed from the Tibetan plateau grasslands?

• The ecosystem will become unstable because predators will have fewer prey, the birds will have fewer nesting sites, and the area downriver will become vulnerable to flooding without the burrows to aerate the soil and provide drainage for monsoon rains.

• The ecosystem will become more stable because the pika will be replaced by other species of small mammals that can fill the niche, bird species will adapt to nesting aboveground, and the soils will become compacted without the burrows.

• The ecosystem will become unstable because the predators will migrate to nearby ecosystems, the birds will nest in nearby trees, and the soils will be aerated by other small mammals.

• The ecosystem will become more stable because the pika will no longer be there to eat the grasses, the birds will migrate to other ecosystems during nesting season, and the soils will be able to absorb more of the monsoon rains without the pika burrows.

6 Albinism is an autosomal recessive condition. Which circle graph shows the genotype probability when an albino female mates with a male that is heterozygous for the albinism trait?

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7 Part of the cell cycle is shown in this simplified model.

This part of the cell cycle is best described as the process that —

• duplicates the DNA

• completes cell division

• maintains genetic homeostasis

• synthesizes new molecules

8 Taq polymerase is an enzyme used in the polymerase chain reaction (PCR) to replicate fragments of DNA. A study published in 1976 examined the properties of Taq polymerase after the enzyme was isolated from Thermus aquaticus, a thermophilic bacterium that lives in the hot springs of Yellowstone National Park. The graph shows one of the results of the study.

Which statement about enzyme activity is best supported by this graph?

• An enzyme must be composed of multiple polypeptides, or subunits, to be active.

• An enzyme’s rate of activity increases with time until it becomes inactive.

• An enzyme functions best under specific temperature conditions.

• An enzyme works equally well in bacteria that are adapted to high temperatures and in eukaryotic cells such as human cells.

9 The human immunodeficiency virus (HIV) often infects and destroys CD4 T cells. These CD4 T cells are one of many kinds of white blood cells that are an important part of the immune system.

The most common danger related to the destruction of CD4 T cells is —

• an increase in the risk of high blood pressure

• an increase in the threat of diseases caused by microorganisms and viruses

• a decrease in the flow of blood to vital organs

• a decrease in the amount of oxygen being transported to tissues

10 Common baboons live on the savanna in breeding groups called troops. While females tend to stay with the troop, younger or less dominant males may leave to join a neighboring troop. Which of these is a likely outcome of movement by young males?

• Gene flow occurs between populations.

• Allele frequencies suddenly change.

• Relative genotypic frequencies reach a constant state.

• Intermediate phenotypes increase in the species.