High School Biology Study Guide for the STAAR test

Page 1

General Information

Before graduating from high school in the state of Texas, you must pass several end-of-course tests and Biology is one of them. To pass, you must receive a II or III on each test. These are the possible score-level designations:

  • III—Advanced Academic Performance
  • II—Satisfactory Academic Performance
  • I—Unsatisfactory Academic Performance

For best results, you are advised to take the Biology I test immediately following your Biology I class completion. This study guide will help you review the concepts covered in the course, and our practice questions and flashcards will help to see how much you remember before test day.

Basic Test Information

  • The STAAR Biology I test contains a total of 54 questions covering the first five major areas of Biology shown in this study guide.

  • The last category in this guide contains a list of the Scientific Process Skills you will be expected to use in answering about 40% of the questions.


All functions in living organisms are performed by cells, and all structures are composed of cells. Cells are the building blocks of organisms and, in turn, biomolecules are the building blocks of cells. This section covers the material assessed in 11 of the 54 questions on the test.

Cell Structure

Cells have specialized parts, called organelles, that keep the cell alive and enable it to perform its role in the function of the entire organism. Organelles are surrounded by a membrane and include the nucleus, mitochondria, endoplasmic reticulum, and, in plants, chloroplasts. Membranes are the structures that define the boundaries of the organelles and the cell itself.

Prokaryotic vs. Eukaryotic Cells

Organelles are found in eukaryotic cells. Prokaryotic cells lack a nucleus and other organelles. In prokaryotic cells, genetic material is concentrated near the center, and there are ribosomes throughout the cell. Prokaryotic cells are surrounded by a plasma membrane and a cell wall. The cell wall differs chemically from the cell wall found in eukaryotic plant cells.

Cellular Processes

Cells carry out processes that keep them alive and enable them to perform functions that help sustain the entire organism.

  • Homeostasis—Homeostasis refers to processes that help the cell (and the entire organism) maintain constant conditions, such as osmotic balance, pH, or temperature.

  • Energy conversions—All cells use cellular respiration to convert chemical energy in sugars into energy available for cellular processes. Plant cells use the process of photosynthesis to convert sunlight energy into sugars.

  • Transport of molecules—Some transport of molecules in or out of a cell occurs by diffusion. Cells can also use energy, in a process called active transport, to move molecules in a direction opposite to diffusion.

  • Synthesis of new molecules—Cells synthesize complex molecules from raw materials. These complex molecules are used in the growth or functioning of the cell or are exported to contribute to the survival of the entire organism.

Viruses vs. Cells

In contrast to the complex structure of cells, viruses are very simple, consisting of either DNA or RNA hereditary material contained within a coating of protein. A virus cannot reproduce on its own; it needs to parasitize a cell and use the cell’s structures to reproduce itself. When viruses infect human cells, they cause diseases such as acquired immunodeficiency syndrome(AIDS) or influenza.

Organism Growth and Cell Differentiation

In addition to growing in size and mass, cells also can develop specialized structures and functions. The process of specialization is called differentiation.

The Cell Cycle

As they grow and reproduce, cells go through several identifiable stages known as the cell cycle. The two main stages are interphase, as the cell prepares to divide, and mitosis, the actual process of division. Interphase is divided into several phases: G1, S, and G2. There is also a resting phase called G0. Mitosis is divided into prophase, metaphase, anaphase, and telophase. You should know the distinguishing characteristics of each phase of the cell cycle.

Specialized Cells

Differentiation results in specialized cells with structure and function suited for a single role in maintaining the organism. For example, root cells in plants are specialized to transport water and minerals from the soil into the plant. Blood cells in animals are specialized to transport oxygen throughout the body.

Cell Differentiation

DNA contains the instructions to synthesize the proteins needed in cell differentiation. RNA is the intermediary between DNA and the protein synthesis sites in the cell. Environmental factors, such as the influence of surrounding cells or the presence of toxic substances may trigger or inhibit differentiation.

Cell Cycle Disruption

The cell cycle is a highly regulated and controlled process, ensuring that an organism has the proper number of specialized cells. Disruptions to the cell cycle will cause diseases such as the uncontrolled runaway cell divisions in cancer.

The Roles of Molecules

Carbohydrate molecules are the fuel for metabolic processes. The energy released by breaking down these molecules is captured and stored by molecules such as ATP. Other molecules, proteins called enzymes, are responsible for facilitating every stage of metabolic processes.


Biomolecules are classified into four general types:

  • Carbohydrates— large molecules containing carbon (C), hydrogen (H), and oxygen (O) atoms

  • Lipids— molecules commonly called fatty acids, oils, and waxes; insoluble in water and are very important in forming cell membranes

  • Proteins— large molecules that contain nitrogen (N) in addition to C, H, and O; they can be either structures or enzymes

  • Nucleic acids— consist of a large chain of nucleotides, each consisting of a phosphate group, a sugar, and a N-containing ring called a base; responsible for heredity

Simple Molecules and Their Organization

There are several hypotheses describing the process of how simple molecules are organized into complex molecules capable of self-replication. Each hypothesis has advantages and problems. A famous experiment supporting the existence of this process was the Miller-Urey Experiment of 1953.


Genetics is the study of DNA and its role in passing traits from one generation to the next. Mendelian genetics describes some mechanisms of how traits are inherited. Your proficiency in this subject is assessed by 11 of the 54 questions on the test.


DNA consists of a chain of individual nucleotides, each containing a sugar molecule, a phosphate group, and a nitrogen-containing base. There are four of these bases: adenine (A), cytosine (C), guanine (G), and thymine (T). The sequence of these bases forms a code that specifies the structure of the proteins that determine the traits of an organism.

The Genetic Code

The genetic code formed by the sequence of bases in a DNA molecule is found across all living things on Earth. All cells use these components; however, each organism has specific sequences of the bases C, G, A, and T that code for structures and functions unique to that organism. Related organisms share similar genetic codes.

Transcription and Translation

Transcription is the process of creating a molecule of RNA that matches the code of a molecule of DNA. It is the RNA molecule that carries this code to the sites where proteins are made. Translation is the process of building a specific protein using the code contained in the RNA. Small RNA molecules called messenger RNA bring in the amino acid building blocks of the protein.

Gene Expression

Genes are segments of DNA that code for a specific trait. The genes for every trait of an organism are present in the nucleus of every cell, but any specific cell produces or expresses only a few of these traits. The process by which traits are expressed in which order is highly regulated and must occur in an exact sequence for the success of the organism.

DNA Changes

There are several ways that the order of bases in a DNA molecule may change. They are substitutions, insertions/deletions, inversions, duplications, and translocations. Collectively, these changes are called mutations. A mutation changes the genetic code. This change may harm, benefit, or have no effect on the organism.

Predicting Genetic Combination Outcomes

Mendel is the scientist who first studied the inheritance of traits and formulated several laws that predict the outcome when parents with different traits produce offspring. Techniques such as Punnett squares help predict the outcome of monohybrid and dihybrid crosses. Although Mendelian genetics is powerful in understanding inheritance, there are also some important non-Mendelian mechanisms.


Every cell of an organism has a double set of chromosomes containing the DNA genetic code. This is the diploid number. The gametes that unite to form a new organism contain only one set, the haploid number. Meiosis is the process of producing haploid gametes from diploid cells. Sexual reproduction would not be possible without meiosis.

Genetic Techniques

DNA is analyzed and manipulated using a variety of technologies. Various enzymes cut DNA into smaller segments in predictable locations. Gel electrophoresis separates the fragments. The polymerase chain reaction duplicates the fragments to produce a large quantity for analysis. DNA fingerprinting identifies specific genetic sequences in an individual. Chromosomes are also analyzed under the microscope to identify potential defects.


All Study Guides for the STAAR test are now available as downloadable PDFs