Glossary

Allele | A variant form of a gene that is located at a specific position on a chromosome. Alleles can be dominant or recessive and can determine an organism’s physical characteristics.

Analysis | The process of breaking down a problem into its component parts in order to understand it and solve it. Analysis involves identifying the problem, gathering data, and drawing conclusions.

Ancestral Trait | A trait that is shared between two species as a result of common ancestry. Ancestral traits are often used to determine the evolutionary relationships between species.

Autosomes | Chromosomes that are not involved in determining an organism’s sex. Autosomes are numbered according to size, with the largest being chromosome 1 and the smallest being chromosome 22.

Autotroph | An organism that produces its own energy and nutrients through photosynthesis or chemosynthesis. Autotrophs are the primary producers in an ecosystem, and are the basis of all food webs.

Body Cavity | A space in an organism’s body that contains organs and other internal structures. The most common body cavities are the coelom, the pseudocoelom, and the blastocoel.

Body Plans | The fundamental structure of an animal’s body, including its symmetry, body segments, and appendages. Body plans are used to classify animals into different phyla.

Cell Respiration | The metabolic process by which cells break down food molecules to produce energy. Cell respiration involves the breakdown of glucose molecules to release energy in the form of ATP.

Cenozoic | The current geological time period, which began 66 million years ago and continues today. The Cenozoic is divided into three eras: the Paleogene, the Neogene, and the Quaternary

Chromosome | Thread-like structures that consist of tightly condensed DNA (deoxyribonucleic acid), and associated proteins.

Clade | A group of species that share a common ancestor. Clades are used to classify organisms into different taxonomic groups.

Cladogram | A diagram that shows the evolutionary relationships between species. Cladograms are constructed using shared derived traits and can be used to determine the evolutionary history of a group of organisms.

Community | A group of organisms of different species that interact and share a common environment. Communities are composed of populations of different species and can be studied to understand the interactions between species.

Conclusion | A statement that summarizes the main points of an argument or experiment. Conclusions are based on the data collected and analyzed and should be supported by evidence.

Control | An experimental sample that serves as a reference for comparison with a test sample. Controls are used to ensure that the results of an experiment are not due to chance or other factors.

Controlled Variables | Factors that are held constant in an experiment to ensure that only the independent variable is changed. Controlled variables are essential for obtaining accurate results from an experiment.

Convergent Evolution | The process by which unrelated species evolve similar traits in response to similar environmental pressures. Convergent evolution is an example of natural selection and can result in similar adaptations in different species.

CRISPR/Cas9 | A cellular system within bacteria that acts as a defense mechanism to recognize and cleave invading DNA from bacterial viruses. This bacterial system is now used as technology that enables the efficient introduction of mutations into genes and organisms.

Data | Information that has been collected and analyzed. Data can be qualitative or quantitative and can be used to draw conclusions and make predictions.

Decomposer | An organism that breaks down dead or decaying organisms and returns their nutrients to the environment. Decomposers are essential for the cycling of nutrients in an ecosystem.

Dependent Variable | The factor that is measured in an experiment and is affected by the independent variable. The dependent variable is used to determine the effect of the independent variable on the system being studied.

Dichotomous Key | A tool used to identify unknown organisms by asking a series of questions with two possible answers. Dichotomous keys are used in taxonomy to classify organisms into different taxonomic groups.

Dominant allele | An allele that expresses the phenotype displayed in a heterozygous individual. The dominant allele masks the recessive allele.

DTC Testing | Direct-to-consumer genetic testing, which is used to assess an individual’s risk of developing certain diseases. DTC testing can be used to identify genetic variations that may increase the risk of a disease or disorder.

Endothermic | An organism that produces its own heat. Endothermic organisms are able to maintain a constant body temperature and are able to survive in a wide range of temperatures.

Environmental Law | Laws that protect the environment from pollution, destruction, and other human activities. Environmental laws are designed to ensure that the environment is protected from harm.

Eutherians | A group of mammals that includes humans, cats, and dogs. Eutherians are distinguished from other mammals by their placenta and their ability to give birth to live young.

Experiment | A scientific procedure that is conducted to test a hypothesis. Experiments involve manipulating the independent variable and measuring the effect on the dependent variable.

Food web | A network of interconnected food chains in an ecosystem. Food webs are composed of producers, consumers, and decomposers, and can be used to understand the flow of energy in an ecosystem.

Fossil | The preserved remains or traces of ancient organisms. Fossils are used to study the evolution of life on Earth and can provide information about the environment in which the organism lived.

Gel Electrophoresis | A laboratory technique used to separate molecules based on their size and charge. Gel electrophoresis is used to separate DNA fragments, and can be used to identify genetic variations.

Gene | A unit of DNA that contains the instructions for producing a particular protein. Genes are passed from parent to offspring and can determine an organism’s physical characteristics.

Gene therapy | The transfer of recombinant DNA into an organism to cause expression of a protein to treat a disease.

Genetic Disease | A disorder caused by a mutation in a gene. Genetic diseases can be inherited or acquired and can range from mild to severe.

Genetic Testing | Testing of a person’s DNA to identify genetic variations that may cause or increase the risk of a disease or disorder. Genetic testing can be used to diagnose genetic diseases and to determine an individual’s risk of developing certain diseases.

Genetically Modified Organism | An organism that receives recombinant DNA or whose genetic material has been altered, usually to cause expression of a protein from another organism.

Genome | The entire set of genetic information contained in an organism. The genome contains all of the genetic information necessary for an organism to function.

Genotype | The genetic makeup of an organism. The genotype is determined by the combination of alleles at each gene locus.

Heterotroph | An organism that must obtain its energy and nutrients from other organisms. Heterotrophs are the consumers in an ecosystem and include animals, fungi, and some bacteria.

Heterozygous | Having two different alleles at a particular gene locus. Heterozygous individuals have one dominant and one recessive allele, and the dominant allele is expressed in the phenotype.

Homologous chromosomes | In diploid organisms this is a pair of chromosomes that are the same length and contain the same genes in the same order on the chromosomal arms. One chromosome from the homologous pair was inherited from the mother and one chromosome from the homologous pair was inherited from the father.

Homozygous | Having two identical alleles at a particular gene locus. Homozygous individuals have two copies of the same allele, and the phenotype is determined by the allele.

Hydrophilic | Molecules with ionic or polar charges that dissolve easily in water.

Hypothesis | A proposed explanation for a phenomenon that can be tested through experimentation. Hypotheses are based on observations and can be tested using the scientific method.

Independent Variable | The factor that is changed in an experiment in order to observe the effect on the dependent variable. The independent variable is the variable that is manipulated in an experiment.

Linnaean System | A system of classification devised by Carl Linnaeus in the 18th century that organizes organisms into hierarchical categories based on their shared traits. The Linnaean system is still used today to classify organisms.

Mammal | A group of animals that are warm-blooded, have hair or fur, and feed their young milk. Mammals are divided into three groups: monotremes, marsupials, and eutherians.

Marsupials | A group of mammals that carry their young in a pouch. Marsupials are found mainly in Australia and South America and include kangaroos, koalas, and opossums.

Mesozoic | The geological period between 66 and 252 million years ago. The Mesozoic is divided into three periods: the Triassic, the Jurassic, and the Cretaceous.

Microarray | A laboratory tool that allows the detection of gene expression of thousands of genes simultaneously. Microarray slides (gene chips) contain DNA sequences that act as probes that will bind to complementary nucleotide sequences if the gene is expressed in the cells.

Monotremes | A group of mammals that lay eggs. Monotremes are found only in Australia and New Guinea and include the platypus and the echidna.

Mummification | The process of preserving a dead organism by exposing it to extreme drying. Mummification was practiced by the ancient Egyptians and was used to preserve the bodies of the deceased for the afterlife.

Paleozoic | The geological period between 541 and 252 million years ago. The Paleozoic is divided into six periods: the Cambrian, the Ordovician, the Silurian, the Devonian, the Carboniferous, and the Permian.

Phenotype | The physical and observable characteristics of an organism resulting from the interaction between its genetic makeup and the environment.

Pheromones | A chemical released by an individual of a species to communicate with or affect the behavior of other members of the same species.

Phylogenetic Tree | A diagram that illustrates the evolutionary relationships among a group of organisms, based on their similarities and differences in genetic, morphological, or behavioral traits.

Phylogeny | The evolutionary history and relationships among species or groups of organisms.

Pipette | A laboratory tool used to measure and dispense small volumes of liquid accurately.

Population | A group of individuals of the same species living in a particular geographic area and potentially interbreeding.

Primary consumer | An organism that feeds directly on producers in an ecosystem.

Producer | An organism that synthesizes organic compounds from simple substances and serves as the primary source of food for other organisms in an ecosystem.

Recessive Allele | An allele that is masked by the presence of a dominant allele and only expressed in the phenotype when paired with another recessive allele.

Recombinant DNA technology | Laboratory methods that enable one to join together DNA fragments from multiple organisms or multiple sources.

Scientific Method | A systematic and logical approach used by scientists to investigate phenomena, including making observations, formulating hypotheses, conducting experiments, and analyzing data.

Secondary consumer | An organism that feeds on primary consumers in an ecosystem.

Shared Derived Traits | Traits that are present in a group of organisms and inherited from a common ancestor but not found in more distantly related organisms.

Taxonomy | The branch of biology that deals with the identification, naming, and classification of organisms.

Tetrapod | A vertebrate animal with four limbs, or that descended from four-limbed ancestors.

Variables | Factors or conditions that can be changed or manipulated in an experiment.

Vertebrates | Animals with a backbone or spinal column, including fish, amphibians, reptiles, birds, and mammals.