BIOLOGY EXAM

Heredity

The passing of traits from parents to offspring.

Genetics

A branch of biology that studies heredity.

Monohybrid cross

A cross among one pair of contrasting traits.

True-bred

If an individual is true-bred, all of its offspring will display only one form of a trait.

P generation

The first two individuals crossed in Mendel's experiments.

F₁ generation

Offspring of the P generation.

F₂ generation

Offspring in Mendel's experiments that exhibited a 3:1 ratio of dominant: recessive traits.

Alleles

Different forms of a gene.

Dominant

A form of a trait that overpowers or masks the other.

Recessive

A form of a trait that is not expressed when the dominant form is present.

Homozygous

A genotype for a trait in which the alleles are the same.

Heterozygous

A genotype for a trait in which the alleles are different.

Genotype

The genetic makeup of an individual.

Phenotype

The physical characteristic of a trait.

Law of Segregation

Mendel's law in which the two alleles for a trait separate when gametes are formed.

Law of Independent Assortment

Mendel's law in which the alleles of different genes separate independently of one another during gamete formation.

Polygenic trait

A trait controlled by two or more genes.

Multiple alleles

A gene that has more than two possible alleles.

Codominance

Both alleles are fully expressed at the same time.

Incomplete Dominance

Neither allele is completely dominant, resulting in a blended trait.

X-linked Trait

A trait carried on the X chromosome.

Vestigial structures

The wings of flightless birds, like the ostrich, are an example of this.

Biochemistry

Study of nucleic acids and proteins to show evolutionary relationships.

Gene flow

Migration.

Adaptation

A physical trait that increases an organism's ability to survive in its environment.

Mass extinction

Sudden elimination of a species due to a catastrophic event.

Punctuated equilibrium

Rapid evolutionary change.

Descent with Modification

Biological change over time that causes descendants to be different from their ancestors.

Natural selection

Principle of natural selection that explains how beneficial traits become more common over time, causing a change in allelic frequencies.

Homologous structures

Body structures that are similar in orientation, but different in function due to organisms living in different environments.

Embryology

Study of development in vertebrates that supports common ancestry among vertebrates.

Sexual selection

When traits that favor reproduction become more common over time, even if they decrease survival ability.

Speciation

When isolation causes two populations to become so different they can no longer reproduce viable offspring.

Paleontology

The study of prehistoric life connecting current and extinct species.

Divergent evolution

Evolution that results in the formation of homologous structures.

Convergent evolution

Evolution that results in the formation of analogous structures.

Gene pool

All of the genes available in a population.

Gradualism

Slow change in allele frequencies over long periods of time.

Evolution

Organisms better adapted to their environment survive and reproduce more successfully.

Morphology

Study of body structures to provide evidence of evolution.

Fossil

Remnants of organisms such as imprints and bones.

Gradual extinction

Slow elimination of species caused by small environmental changes over long periods.

Analogous structures

Similar body structures due to organisms living in the same environment, not because of shared ancestry.

Biogeography

Study of the physical distribution of plants and animals.

Succession

A regular progression of species replacement.

Abiotic factors

Nonliving factors, such as weather, that can affect ecosystems.

Ecology

The study of living things and their interaction with each other and the environment.

Pioneer species

Plants or mosses that first grow in a newly formed ecosystem.

Biodiversity

The variety and genetic differences found within an ecosystem.

Ecosystem

An ecosystem consists of a community and all of the physical aspects of the habitat.

Biosphere

The portion of the planet that can sustain life.

Community

All the different species that live together in an ecosystem.

Secondary succession

Succession that occurs in places where there has previously been growth.

Biotic factors

Living factors that are part of the ecosystem.

Primary succession

Succession that occurs where no soil has existed (no previous growth).

Biome

A biome is part of the biosphere that has a specific climate and community.

Example of primary succession

New land formed after a volcanic eruption.

Example of secondary succession

A forest growing back after a wildfire.

Why are producers essential to an ecosystem?

Producers make food through photosynthesis and provide energy for all other organisms in the ecosystem.

Why are decomposers essential to an ecosystem?

Decomposers break down dead organisms and recycle nutrients back into the environment.