Grade 8 Science Vocabulary

Heredity, Reproduction & Change Over Time

How fossils show that species change over time, how organisms reproduce, and how traits pass from parents to offspring.

Ohio science standards in this unit

8.LS.1 · Fossils & change over timeDiversity of species, a result of variation of traits, occurs through the process of evolution and extinction over many generations. The fossil records provide evidence that changes have occurred in number and types of species.
8.LS.2 · ReproductionEvery organism alive today comes from a long line of ancestors who reproduced successfully every generation.
8.LS.3 · HeredityThe characteristics of an organism are a result of inherited traits received from parent(s).

Definitions are written in plain language to support WIDA's Standard 4 (Science) English Language Development standard.

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diversity: Variety; many different kinds.
fossil: The preserved remains or traces of an organism that lived long ago.
trait: A characteristic of an organism, like eye color or leaf shape.
species: A group of organisms that are alike and can have offspring together.
extinction: When every member of a species has died.
fossil record: All the fossils found so far and what they tell us about life in the past.
geologic record: The history of Earth stored in rock layers and fossils.
biodiversity: The variety of different living things in an area.
deposition: The dropping of sediment in a new place. It can bury remains that become fossils.
ancestor: An earlier organism that later organisms came from.
transitional form: A fossil that shows traits of both an older group and a newer group.

reproduction: The process of making new living things.
sexual reproduction: Making offspring from two parents. Each parent gives half the genetic information.
asexual reproduction: Making offspring from one parent. The offspring are copies of the parent.
cell theory: The idea that all living things are made of cells and new cells come from existing cells.
gene: A section of DNA that carries the instructions for a trait.
meiosis: Cell division that makes sex cells with half the usual number of chromosomes.
Mendelian genetics: The basic rules of inheritance first discovered by Gregor Mendel using pea plants.
embryology: The study of how organisms develop before birth or hatching.
egg: The female sex cell.
sperm: The male sex cell.
gamete: A sex cell: an egg or a sperm.
fertilized egg: The first cell of a new organism, made when a sperm joins an egg.

DNA: The molecule in every cell that carries the instructions for how an organism grows and works.
generation: All the offspring born at about the same time.
allele: One version of a gene, such as the version for brown eyes or blue eyes.
law of segregation: Each parent passes only one of its two alleles for a trait to its offspring.
law of independent assortment: Alleles for different traits are passed on separately from each other.
dominant: An allele that shows its trait even when only one copy is present.
recessive: An allele whose trait shows only when two copies are present.
codominant: When two different alleles both show fully, like red and white patches on a flower.
pedigree: A chart that shows how a trait is passed down through a family.
phenotype: The trait you can observe, like purple flowers.
genotype: The pair of alleles an organism has for a trait, like Pp.

Words from earlier grades that help with this unit.

biome: A large region with a certain climate and living things adapted to it.
biotic: Living parts of an environment.
abiotic: Nonliving parts of an environment.
mitosis: Cell division that makes two cells with the same DNA as the parent cell.