Which part of a DNA molecule is responsible for the direct coding of specific traits in an organism?

Differences in traits such as hair texture are determined by differences in -

How is information for a specific protein carried on a DNA molecule?

How does DNA in cells determine an organism's traits?

The arctic fox inhabits northern areas of North America. The same arctic fox is shown in the drawing at different times of the year. What causes this change in fur color?

Mice have two unlinked allele pairs that affect fur color. The table shows how allele pairs affect fur color. The term "agouti" describes fur with pigmentation that changes in each hair from the shaft to the tip, giving the fur a banded appearance. Mice with the aa allele pair are albino, regardless of the second allele-pair combination.

What is the probability of albinism in the offspring of a cross between two mice with AaBb alleles?

A segment of DNA is represented in the illustration.

How is information for a specific protein carried on the DNA molecule?

During secondary succession, which of these best describes why decomposing pioneer plants give way to larger, more complex plant species, such as hardwood trees?

Grassland ecosystems in Texas have evolved to depend on periodic fires to return nutrients to the soil and encourage plant reproduction. Humans have prevented fires in many of these grassland areas, resulting in plant and animal communities with little diversity. Wildlife biologists often recommend purposefully starting fires called prescribed burns, which are monitored and controlled, in grassland ecosystems every 3 to 4 years. These biologists observe greater diversity in plant and animal life in the years following a prescribed burn. What natural processes are the biologists attempting to imitate?

A small town in the piney woods of East Texas has a soccer field composed of native grasses. The soccer field is mowed once a week. What effect does continual mowing have on the ecology of the field?

Enchanted Rock State Natural Area is located in Central Texas. Enchanted Rock is a dome of granite. The area contains four easily identifiable communities. The table describes characteristics of each type of community in the area.

A student studying primary succession should focus on which of these communities?

An estuary collects sediments from teh ocean and rivers that feed into it. The sediments swirl around and then settle to form a medflat. Eel grass is then established on the mudflat. The ecosystem changes over time and ultimately develops into a salt marsh that contains mangrove trees. Which of the following is likely NOT involved in this example of ecological succession?

Which statement describes the differences in species diversity between an ecosystem beginning the process of primary succession and one beginning the process of secondary succession?

The ocean sunfish is a large, flat fish that spends most if its time in deep water feeding mainly on jellyfish. Sunfish often have many species of copepods, small crustaceans, that bury their heads into the soft tissue of the sunfish. Sunfish will swim to the surface of the water and lie sideways, allowing seabirds to eat the copepods from their skin. Which list describes the types of relationships the sunfish has with other marine organisms?

Which of these best demonstrates mutualism between certain types of bacteria and humans?

A partial Texas food web is shown. The populations of which organisms will most likely increase as a result of a disease that suddenly reduced the population of Texas horned lizards?

A biomass pyramid of an ecosystem is shown. Which statement provides the best explanation for the difference in biomass of organisms found at each trophic level?

A partial meadow food web is shown. Based on this food web, which organisms are direct sources of energy for secondary consumers?

The Texas blind salamander lives in the Edwards Aquifer region around San Marcos. The table lists some of the organisms that live with the salamander in this environment and their food sources. In an energy pyramid for these aquifer cave dwellers, which of the following would be placed at the bottom?

Which of the following is most likely to cause the greatest disruption to an ecosystem?

Which molecule synthesized by plants is a major source of energy for cellular processes in both plants and animals?

Parrotfish are herbivores that are found in coral reefs. To escape predation, a parrotfish will graze with a rabbitfish, which has venomous spines at the end of its pelvic fins. The rabbitfish does not benefit from this relationship. Which type of relationship do the parrotfish and the rabbitfish have in the coral-reef environment?

Frogs and toads belong to the order Anura. The smallest organism in this order is about 7 millimeters long, while the largest is about 30 centimeters long. Which of these lists best describes this order?

Two populations of mice living in the same forest are separated by a large water-filled ditch. After a rainstorm, flooding brings several mice from one population to the other population. When the mice from the first population reproduce with members of the second population, which of the following will likely occur?

The food web shows the flow of energy through a sagebrush-steppe ecosystem. Which of these organisms are in a trophic level that receives a larger percentage of the energy captured by the producers than the percentage received at the bats’ trophic level?

An analysis of DNA and RNA sequences can be used to classify organisms. A dendrogram, such as the one shown, is based on molecular data. It can be used to represent evolutionary relationships within a group of organisms that are hypothesized to have descended from a common ancestor. Which statement is best supported by the information in this dendrogram?

All the animals to the right of the hagfish would have the common characteristic of

The differences between two molecules include the type of sugar that forms a section of the molecules and the identity of one of the four nitrogenous bases that make up another section of the molecules. These two molecules are

A student is asked to draw a food web in which the same organism is a primary consumer as well as a secondary consumer. How should the organism be represented in the food web?

Which organisms can be found at the first, or lowest, trophic level?

Which statement best describes the relationship that exists among proteins, DNA, and cells?

Some organisms that share a common ancestor have features that have different functions, but similar underlying structures. These are known as

The green frog (Lithobates clamitans clamitans) is found in many parts of the United States. The table contains some information about this frog. Why does the ability to lay 1,000 to 5,000 eggs increase the fitness of the species L. clamitans clamitans?

Surtsey is an island located south of Iceland. The island was formed by a volcanic eruption and first appeared in 1963. The table contains descriptions of changes in the population and diversity of species on Surtsey. Which of these lists the descriptions in the correct order of ecological succession on Surtsey?