Unit 4 Vocabulary List Biology 150 Fall 2025

A comprehensive vocabulary list covering essential biological terms and concepts for Biology 150.

Precambrian

The earliest time period in Earth's history, encompassing the Hadean, Archaean, and Proterozoic eons.

Hadean eon

The time from Earth's formation to about 4 billion years ago.

Archaean eon

The eon following the Hadean, from about 4 to 2.5 billion years ago, marked by the appearance of the oldest known rocks.

Proterozoic eon

The eon from 2.5 billion years ago to 542 million years ago, leading to significant changes in Earth's biota.

Phanerozoic eon

The current eon, starting about 542 million years ago, known for the abundance of fossil records.

Adaptive radiation

The diversification of a group of organisms into forms filling different ecological niches.

Three domain hypothesis

A classification system that divides life into Bacteria, Archaea, and Eukarya.

Bacteria

Single-celled microorganisms that are prokaryotic.

Archaea

Microorganisms that are similar to bacteria but genetically distinct and often found in extreme environments.

Eukaryotes

Organisms whose cells contain a nucleus and other organelles enclosed within membranes.

Prokaryotes

Organisms that lack a nucleus, typically unicellular, including bacteria and archaea.

Unicellular

Organisms composed of a single cell.

Multicellular

Organisms composed of multiple cells.

Microbe

A microscopic organism, which can be a bacterium, fungus, virus, or even a protist.

Microbiome

The collection of microorganisms living in a particular environment, including the human body.

Extremophile

Organisms that thrive in extreme environmental conditions.

Phototrophs

Organisms that obtain energy from sunlight.

Cyanobacteria

Photosynthetic bacteria known for producing oxygen.

Chemotrophs

Organisms that obtain energy from chemical compounds.

Autotroph

Organisms that produce their own food from inorganic materials.

Heterotroph

Organisms that obtain food by consuming other living things.

Peptidoglycan

A polymer that makes up the cell wall of bacteria.

Gram stain

A laboratory technique used to differentiate bacterial species into two groups based on their cell wall composition.

Gram positive

Bacteria with a thick peptidoglycan layer in their cell wall, retaining the gram stain.

Gram negative

Bacteria with a thin peptidoglycan layer and an outer membrane, not retaining the gram stain.

Pathogen

An organism that causes disease.

Virulence

The degree of pathogenicity or ability of a pathogen to cause disease.

Antibiotics

Medications used to treat bacterial infections.

Virus

A small infectious agent that can replicate only inside living cells.

Capsid

The protein shell of a virus that encases its genetic material.

Mitochondria

Powerhouse of the cell, where ATP is produced.

Chloroplast

Organelles found in plant cells that conduct photosynthesis.

Endosymbiosis

A symbiotic relationship where one organism lives inside another.

Primary endosymbiosis

The process by which a eukaryotic cell engulfs a prokaryotic cell leading to the formation of organelles like chloroplasts.

Secondary endosymbiosis

The process where a eukaryotic cell engulfs another eukaryotic cell.

Cellular respiration

The metabolic process that converts food into energy (ATP) in cells.

ATP

Adenosine triphosphate, the energy currency of the cell.

Photosynthesis

The process by which green plants and some other organisms use sunlight to synthesize foods with carbon dioxide and water.

Glucose

A simple sugar that is an important energy source in living organisms.

Infolding

The process where the cell membrane folds inward to create complex structures in eukaryotic cells.

Nuclear membrane

The double membrane surrounding the nucleus of a eukaryotic cell.

Protist

A diverse group of eukaryotic microorganisms.

Cellulose

A polysaccharide consisting of a linear chain of several hundred to many thousands of linked D-glucose units.

Starch

A storage polysaccharide in plants.

Cuticle

A waxy covering on plant surfaces that helps prevent water loss.

Stomata (stoma)

Small openings on plant leaves that allow gas exchange.

Flavonoids

Plant compounds that affect color and provide protection against UV radiation.

Vascular system

Plant tissues (xylem and phloem) that transport water, nutrients, and sugars.

Lignin

A complex organic polymer that provides strength to plant cell walls.

Tracheid

Long, narrow cells in the xylem that help transport water.

Vessel structures

More efficient conduits for water transport found in angiosperms.

Pollen

The male gametophyte in seed plants, which contains the male gametes.

Seeds

Structures that contain the embryos of seed plants.

Nonvascular plants

Plants that lack a vascular system, such as mosses.

Seedless plants

Plants that reproduce without seeds, such as ferns.

Gymnosperms

Seed-producing plants with unenclosed seeds.

Angiosperms

Flowering plants that produce seeds enclosed in fruits.

Haploid

A cell containing one complete set of chromosomes.

Diploid

A cell containing two complete sets of chromosomes.

Alternation of generation

The life cycle of plants that alternates between haploid and diploid phases.

Spore

A reproductive cell capable of developing into a new organism.

Gamete

A reproductive cell (sperm or egg) that fuses during fertilization.

Sporophyte

The diploid, spore-producing phase in the life cycle of plants.

Gametophyte

The haploid, gamete-producing phase in the life cycle of plants.

Fertilization

The union of male and female gametes to form a zygote.

Zygote

The fertilized egg that develops into a new organism.

Asexual reproduction

Reproduction that does not involve the fusion of gametes.

Sexual reproduction

Reproduction involving the fusion of gametes.

Microspores

Spores that develop into male gametophytes.

Megaspores

Spores that develop into female gametophytes.

Sporophyte-dominant

Plants whose main phase is the sporophyte.

Gametophyte-dominant

Plants whose main phase is the gametophyte.

Flower

The reproductive structure of angiosperms.

Stamen

The male reproductive part of a flower, producing pollen.

Carpel

The female reproductive structure of a flower.

Fruits

Mature ovaries of flowers, often containing seeds.

Pollination

The transfer of pollen from the male anther to the female stigma.

Seed dispersal

The process of spreading seeds away from the parent plant.

Chitin

A polysaccharide that makes up the cell walls of fungi.

Glycogen

The primary storage form of energy in animals.

Yeasts

Single-celled fungi used in baking and brewing.

Mycelia (mycelium)

The network of fungal filaments (hyphae) that absorbs nutrients.

Hyphae

The long, thread-like structures that make up the body of fungi.

Septa

Cross walls in hyphae that separate individual cells.

Coenocytic

Fungi that lack septa and contain many nuclei within a shared cytoplasm.

Plasmogamy

The fusion of cytoplasm from two parent mycelia.

Heterokaryotic

A fungal cell containing genetic material from two different parent mycelia.

Karyogamy

The fusion of nuclei from two parent cells in fungi.

Mating types

Different forms of fungi that allow for sexual reproduction.

Conidia

Asexual spores produced by fungi.

Meiospores

Spores that are produced through meiosis.

Spore-producing body

Structure in fungi that produces spores.

Saprophyte

An organism that feeds on dead or decaying organic matter.

Mycorrhizae

Symbiotic associations between fungi and plant roots.

Endophytes

Fungi that live inside plant tissues without causing harm.

Cambrian Explosion

A period of rapid diversification of life forms on Earth during the Cambrian period.