In 1898 Friedrich and Paul Frosch found evidence that the cause of the highly contagious hoof-and-mouth disease in livestock was a microscopic infectious particle. It was discovered that this particle requires a host cell to reproduce.

Which pathogen is most likely responsible for causing hoof-and-mouth disease in livestock?

In the 1880s, Louis Pasteur developed a method of weening viruses. The weakened viruses could be injected into healthy individuals.

How is this method effective in fighting viral diseases?

Which of these describes a difference between viruses and cells?

The picture shows a 3-D model of a virus called a bacteriophage. Bacteriophages can infect bacteria such as E. coli.

In what way are the bacteriophage and E. coli alike?

Models of the human immunodeficiency virus (HIV) and an animal cell are shown. What is the difference in function of the glycoprotein structures of an HIV virion and the cilia of an animal cell?

A person infected with the human immunodeficiency virus (HIV) may not have any symptoms for a period of time. During this period the virus affects the body by doing which of the following?

Severe acute respiratory syndrome (SARS) is an illness caused by a coronavirus. Symptoms including a high fever, headaches, and body aches typically occur two to seven days after infection by the virus. SARS is more serious in elderly patients. This information suggests that the reproductive cycle of the SARS virus is —

A photograph of a virus is shown above.

The projections on the surface of this virus allow the virus to—

Cold sores are caused by the herpes simplex virus type 1. A company that wants to develop antiviral drugs would ask a research immunologist to study —

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--

Viruses can be transmitted through air, water, food, insect bites, and direct skin contact. Once a virus gains entry to the body, it invades a host cell in order to--

The 1918 influenza epidemic killed between 50 million and 100 million people worldwide. This epidemic happened near the end of World War I. More people died from the influenza epidemic than were killed in the war. Which of the following explains why this virus was so deadly worldwide?

H1N1 flu is a highly contagious viral infection caused by the influenza A (H1N1) virus. The symptoms of H1N1 flu are listed in the box below. An antiviral agent administered within 48 hours of the appearance of symptoms can reduce the severity of the illness.

Why is it important to administer an antiviral agent to an infected person within the 48 hours of the appearance of symptoms?

Organisms are classified today using the Linnaean system, and the following table shows the taxonomic classification of two marine organisms living along the Pacific Coast.

Taxonomic classification is important to marine biologists because it provides a way to -

Five general characteristics of organisms in kingdoms Plantae or Fungi are listed in the box. Which table correctly lists the characteristics of the organisms in the two kingdoms?

Having a standard taxonomic system benefits the scientific community by allowing scientists from all over the world to do which of the following?

A student used a microscope to study four members of the phylum Ciliophora. Members of this phylum move when propelled by hundreds of tiny cilia.

Although these organisms belong to the same phylum, they are classified as different

The gray squirrel, Eastern fox squirrel, and red squirrel are all different species of squirrels. Why is having a scientific name for each species of an organism important?

Which list correctly identifies characteristics that protists share with animals?

Simple leaves have a single leaf on petiole, or stem, while compound leaves have more than one leaflet on a petiole. The unknown leaf can be identified using the dichotomous key. Which tree does the unknown leaf come from?

Arthopods are joint-legged animals. Spiders, crabs, pill bugs, centipedes, and millipedes are example of the many types of arthropods. Which of these arthropods are most closely related?

Adult mountain lions (Puma concolor) are almost 2 meters long. They have a black spot over each eye. The common names used throughout the United States for this species are listed above. Why is it best for scientists to use the name from the standardized taxonomic system?

Using a light microscope, a student identified the following characteristics of four organisms found in a sample of pond water. Based on the observations of the student, which organisms most likely belong to the taxonomic group of bacteria?

A student collected the animal shown below on a field trip. The student used a dichotomous key and a microscope to classify the animal.

How should this animal be classified?

The diagram shows taxonomic groups and a major distinguishing characteristic of all but two of them.

Which characteristics will be used to complete the chart?

The diagram shows a dichotomous key and a picture of a fruit.

According to the key, the fruit comes from which species of tree?

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

A cladogram is shown below.

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

A student wants to use the Venn diagram below to show the characteristics of two kingdoms of organisms. The characteristics that the two kingdoms share will be listed in the shaded area where the circles intersect.

Which of these is a characteristic that the student should list in the shaded part of the diagram?

The classifications of four trees are shown in the table.

Which two trees are the most closely related?

The classifications of four trees are shown in the table.

Which two trees are the most closely related?

While visiting a national park, a student encounters an unfamiliar organism in a damp area near a body of water. The student notes that the organism is about 10 cm long, has four legs, and has a tail. The organism is black with small white spots on its smooth, moist skin. It also appears to have an internal skeletal system. To which class does the organism most likely belong?

Based on the Key, which of these best describes the leaves and cones of the longleaf pine?

A team of students encounters an unknown organism in a field while conducting a biodiversity study. Some students think the organism is a plant, while others think it is a fungus.

Which question should the students investigate to classify the organism correctly?

Scientists around the world use a standardized taxonomic system. Why would scientists want to use a taxonomic system that is standardized?

The relationship among different orders of millipedes are shown in the cladogram.

Based on the cladogram, which statement best describes relationships among millipede orders?

A dichotomous key for identifying fish is shown.

Based on this key, which two fish have eyes located on either side of their head and are not spotted?

Many tree frog populations are threatened due to habitat loss. In an effort to promote conservation, tree frogs may be bred in captivity. A zoo acquired male and female tree frogs from two different populations. In the zoo, the tree frogs were able to successfully mate within their own population, but breeding attempts between the two populations were unsuccessful.

Based on this information. which statement correctly describes the relationship between the two populations of tree frog?

The Linnaean taxonomic system classifies organisms into divisions called taxa. If two organisms belong to the same taxonomic group, they are related. If two organisms belong to the same taxonomic group, they are related. Similarity at which of these levels indicates the closest relation ship?

During meiosis, homologous chromosomes exchange genetic material. This exchange of genetic material -

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.

In cattle the allele for cloven hooves (H) is dominant over the allele for mute-foot hooves (h). The phenotype for each trait is shown in this picture.

What is the probability of cloven hooves in the offspring of parents that are heterozygous for the trait?

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?

In Holstein cattle the allele for black hair color (B) is dominant over the allele for red hair color (b) and the allele for polled (P), or lacking horns, is dominant over the allele for having horns (p).

What is the expected phenotypic ratio of the offspring of a BbPp x BbPp cross if these alleles sort independently?

Chickens can have different types of feathers. Frizzled feathers curl towards a chicken's head. Assume that feather type is determined by a single gene and that the allele for frizzled feathers is dominate over the allele for straight feathers. In a cross between two chickens with straight feathers, what percentage of the offspring can be expected to have frizzled feathers?

facial dimples and free earlobes are both considered dominant human traits. What are the expected phenotype of the offspring of a female with dimples and free earlobes (DDFf) and a male with no dimples and attached earlobes (ddff)?

in 1860s Gregor Mendel performed numerous dihybrid crosses between pea plants. Dihybrid crosses involve the study of the inheritance patterns related to two different traits. In guinea pigs the allele for black fur (B) is dominant over the allele for brown fur (b), and the allele for short fur (F) is dominant over the allele for long fur (f). What percentage of the offspring from a BbFf x bbff cross would be expected to be heterozygous for both traits?

Tomato plants usually have hairy stems. Hairless stems are present in tomato plants that are homozygous recessive for this trait. If the stems characteristics are determined by a single gene, what is the expected outcome of crossing two plants that are heterozygous for hairy stems?

If several pea plants with the genotype TTYy are crossed with pea plants with the genotype Ttyy, what percentage of the offspring will be expected to have the TTYy allele combination?

In cocker spaniels the allele for a black coat color (B) is dominant over the allele for brown coat color (b). If a brown cocker spaniel is crossed with a heterozygous black cocker spaniel, which of the following genotypic ratios can be expected?

Which statement is best suppoted by the phenotypes of these offspring?

The inheritance pattern for an autosomal dominant trait is shown in the pedigree. Shaded symbols represent individuals that express the dominant trait.

Based on this pedigree, what are the most likely genotypes of individuals in I-1 and I-2?

In humans blood type is determined by the A, B, and O alleles. The A and B alleles are codominant to each other and dominant over the O allele. An individual with the AO genotype and an individual with the BO genotype can produce offspring with which of the following phenotypes?

Normal fruit flies have brownish-yellow bodies, and this body color is dominant. A mutation in the gene for body color can produce flies with an ebony body color. A homozygous normal fruit fly (e⁺e⁺) is crossed with a homozygous ebony fruit fly (ee). What is the predicted outcome of this genetic cross?

Which diagram demonstrates how crossing-over contributes to genetic variety during meiosis?

Sexual reproduction in animals depends on the production of gametes. Which of these processes produce gametes in animals?

Human body cells each have 46 chromosomes in their nuclei. Meiosis is necessary in order to ensure that each gamete produced in the human body has -

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?

A student reads this advertisement for a product containing a plant micronutrient that can be added to soil.

Based on this information, the student can conclude that boron is absorbed by plant roots from soil and then —

Several structures work together to allow flowering plants to reproduce. The diagram shows a typical flower.

Which table correctly identifies the function of each structure or group of structures in the reproduction of the plant?

Plants called sundews have rounded green leaves with many hair-like structures. The ends of these structures contain enzymes in a sticky liquid that looks like nectar or moisture, as shown in the picture. The hairs do not react to dust or nonliving material but will bend inward when insects get caught in the sticky liquid. Sundews digest trapped insects over a period of a few days.

Based on this information, what functions do the specialized leaves of sundews perform?

A student conducted an investigation to study phototropism in grasses. The only difference between the control group and the experimental group was the light conditions. The control group was provided full light, while the experimental group was shaded on one side. The diagrams show the average heights and positions of blades of grass in the investigation. (View Image)

Which statement best explains why the grass tips of the experimental group bent toward the light?

The internal transport of water and minerals in plants requires that two systems work together. Which diagram correctly describes how the two systems accomplish this?

The diagram shows the reproductive system of a plant. Which of the following best describes the interaction that occurs between a plant's reproductive parts during self-fertilization?

Leaves are part of a plant's shoot system. The xylem tissue in leaves transports -

A corn plant produces both male and female flowers. The male flower forms the tassel and the female flower forms the ear of corn. The silks that emerge from the ear are the stigma of the female flower. Each silk leads to an ovule that can become a corn seed.

Which of these must happen for corn seeds to develop on the ear?

10B. Some students are instructed to put a celery stalk in a red dye solution for a lab activity. First the students carefully cut the bottom of the stalk with a scalpel. Then they put the stalk in the beaker with the solution and place the beaker on a shelf in the lab room. The next day they check the stalk and make observations. The students cut across the celery stalk and use a hand lens to see that the small tube openings along the edge of the celery stalk are also red. The cross section is shown below. How do the plant systems work together to make this movement of liquid possible?

10B. An animal can wound a tree by scratching away the bark. The tree can respond to the wound in many ways. Usually sap quickly covers the wound, and then the tree covers the wound with new growth. The diagram shows a cross section of a tree with a healed wound.

Fruits grown in hot climates are usually less sweet than those grown in cooler temperatures. The high temperatures increase the rate of respiration in the plants, thus reducing the sugar content in some fruits. Why does increased respiration in the leaves and stems reduce the sugar content in the fruits of a plant?

Plant roots have extensions called root hairs. These root hairs are important in the homeostasis of the plant. Which statement best explains the importance of the root hairs to the stems and leaves of the plant?

The outermost layer of plant stems in dicotyledons consists of epidermal cells and guard cells that surround openings called stomata. The epidermal cells are usually covered with a waterproof layer that provides protection from injury and water loss. The stomata allow gas exchange. The epidermal cells and stomata have functions similar to those of which two human body systems?

Plant hormones serve as chemical messengers between cells and tissues. Auxin is a plant hormone that causes the cells on the shady side of a plant shoot to elongate. The response enable by auxin is know as -

Copper is a micronutrient that can be found in soil. Copper is important for reproductive growth in plants and plays an indirect role in chlorophyll production. Which statement correctly describes the interaction that occurs between the root and the shoot systems of plants to allow reproduction to occur?

Gametes Produced by an organism contain a combination of genes from that organism. In every gamete, this combination is-

Which statement about the event represented in the diagram is valid?

During meiosis, homologous chromosomes exchange genetic material. This exchange of Genetic material-

Sexual reproduction in animals depends on the production of gametes. Which of these processes produces gametes in animals?

Crossing-over between nonsister chromatids during meiosis is significant in heredity. This process most likely leads to an increase in which of the following?