Semester Exam Biology

Comprehensive vocabulary flashcards covering biology topics including reproduction, genetics, evolution, ecology, and the central dogma for the 2026 Spring Semester Exam.

Asexual Reproduction

A mode of reproduction requiring only 1 parent, resulting in offspring that are genetically identical to the parent.

Sexual Reproduction

A mode of reproduction requiring 2 parents, resulting in offspring that are genetically describes as a combination of both parents.

Budding

A type of asexual reproduction where a new organism develops from an outgrowth or bud due to cell division at one particular site.

Fragmentation

A type of asexual reproduction where an organism breaks into parts that each grow into a new individual.

Binary Fission

A type of asexual reproduction common in prokaryotes where a cell divides into two nearly equal parts.

Fertilization

The process where male and female gametes (cells) participate and join to create a result, often a zygote.

Internal Fertilization

A type of sexual reproduction where the union of an egg and sperm occurs inside the body of a parent.

External Fertilization

A type of sexual reproduction where the union of an egg and sperm occurs outside the body, typically in an aquatic environment.

Chromosome

A thread-like structure of nucleic acids and protein found in the nucleus, carrying genetic information in the form of genes.

Diploid Cell ($2n$)

A cell containing two complete sets of chromosomes, one from each parent.

Haploid Cell ($n$)

A cell containing a single set of unpaired chromosomes, such as a gamete.

Gamete

A mature haploid male or female germ cell which is able to unite with another of the opposite sex in sexual reproduction.

Meiosis

A type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, used for the production of gametes.

Crossing Over

The exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring; important for genetic variation.

Genetic Variation

The difference in DNA among individuals or the differences between populations; important for the survival and adaptation of a species.

Insertion

A chromosomal mutation involving the addition of one or more nucleotide base pairs into a DNA sequence.

Deletion

A chromosomal mutation in which a part of a chromosome or a sequence of DNA is lost during DNA replication.

Duplication

A chromosomal mutation that involves the production of one or more copies of a gene or region of a chromosome.

Translocation

A chromosomal mutation where a segment of a chromosome breaks off and attaches to another chromosome.

Inversion

A chromosomal mutation that occurs when a section of DNA is reversed or flipped within the chromosome.

Trait

A specific characteristic of an individual.

Gene

A unit of heredity which is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

Allele

One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

Homozygous

Having two identical alleles of a particular gene or genes.

Heterozygous

Having two different alleles of a particular gene or genes.

Dominant

An allele or phenotype that is expressed even when only one copy is present (e.g., associated with the dominant phenotype).

Recessive

An allele or phenotype that is only expressed when two copies are present.

Genotype

The genetic constitution of an individual organism.

Phenotype

The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

Gregor Mendel

The father of the field of genetics who studied pea plants.

Codominance

A non-Mendelian trait where both alleles are simultaneously expressed in the heterozygote (e.g., blood type AB).

Incomplete Dominance

A non-Mendelian trait where the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes (e.g., pink roses from red and white parents).

Sex-linked

Traits that are influenced by genes carried on the sex chromosomes (X or Y).

Karyotype

An individual's collection of chromosomes used to look for abnormal numbers or structures, such as identifying Downs Syndrome or determining sex.

Chargaff's Rule

The rule stating that DNA from any cell of all organisms should have a $1:1$ ratio of pyrimidine and purine bases (specifically, the amount of Guanine is equal to Cytosine and the amount of Adenine is equal to Thymine).

tRNA

Transfer RNA; a type of RNA molecule that helps decode a messenger RNA (mRNA) sequence into a protein.

mRNA

Messenger RNA; a large family of RNA molecules that convey genetic information from DNA to the ribosome.

Ribosome

The cellular structure that serves as the site of protein synthesis.

Codon

A sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule.

Double Helix

The shape of DNA, discovered by researchers like Rosalind Franklin, James Watson, and Francis Crick.

Point Mutation (Substitution)

A type of DNA mutation where a single nucleotide base is changed, inserted, or deleted from a sequence of DNA or RNA.

Frameshift Mutation

A DNA mutation caused by indels (insertions or deletions) of a number of nucleotides in a DNA sequence that is not divisible by three.

Relative Dating

The science of determining the relative order of past events without necessarily determining their absolute age.

Stratification

The process in which sedimentary rocks are arranged in layers.

Homologous Structure

Organ or bone that appears in different animals, underlining anatomical commonalities demonstrating descent from a common ancestor.

Analogous Structure

Features of different species that are similar in function but not necessarily in structure and which do not derive from a common ancestral feature.

Vestigial Structure

Structures that have no apparent function and appear to be residual parts from a past ancestor.

Convergent Evolution

The process whereby organisms not closely related independently evolve similar traits as a result of having to adapt to similar environments.

Divergent Evolution

The process by which a species evolves into two or more descendant or different forms.

Heritable Trait

A characteristic which is influenced by genes and passed from parents to offspring.

Fitness

The ability of an individual to survive and reproduce in its specific environment.

Adaptation

A change or the process of change by which an organism or species becomes better suited to its environment.

Natural Selection

The process whereby organisms better adapted to their environment tend to survive and produce more offspring.

Speciation

The formation of new and distinct species in the course of evolution.

Reproductive Isolation

A set of evolutionary mechanisms, behaviors, and physiological processes critical for speciation that prevent members of different species from producing offspring.

Geographic Isolation

A population of animals, plants, or other organisms that are separated from exchanging genetic material with other organisms of the same species by physical barriers.

Mechanical Isolation

A type of reproductive isolation that occurs because different species are isolated by their mechanics, such as incompatible genitalia.

Behavioral Isolation

Reproductive isolation based on the behavior of species in the context of mating rituals and signals.

Binomial Nomenclature

The two-part scientific naming system (Genus species) formatted in italics or underlined.

Cladogram

A diagram used to show relations among organisms, representing shared characteristics and evolutionary paths.

Biotic

Relating to or resulting from living things, especially in their ecological relations.

Abiotic

Physical rather than biological; not derived from living organisms (e.g., sunlight, temperature).

Autotroph

An organism that is able to form nutritional organic substances from simple inorganic substances such as carbon dioxide (e.g., producers like grass).

Heterotroph

An organism deriving its nutritional requirements from complex organic substances (e.g., consumers).

Herbivore

An animal that feeds on plants.

Carnivore

An animal that feeds on flesh/meat.

Omnivore

An animal or person that eats food of both plant and animal origin.

Decomposer

An organism, especially a soil bacterium, fungus, or invertebrate, that decomposes organic material.

Detritivore

An animal which feeds on dead organic material, especially plant detritus.

Trophic Level

Each of several hierarchical levels in an ecosystem, comprising organisms that share the same function in the food chain.

10% Rule

The principle that only about 10% of the energy in a given trophic level is available for use in the trophic level above it.

Ecological Succession

The process of change in the species structure of an ecological community over time.

Symbiosis

Interaction between two different organisms living in close physical association.

Parasitism

A relationship between two species of plants or animals in which one benefits at the expense of the other, sometimes without killing the host organism.

Commensalism

An association between two organisms in which one benefits and the other derives neither benefit nor harm.

Mutualism

Symbiosis that is beneficial to both organisms involved.

Niche

The role or function of an organism or species within an ecosystem.