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Taxonomy Terms

Taxonomy Terms

Get down with the lingo

Autotrophs

Organisms that can create complex organic molecules from simple inorganic molecules found in their environments. They are also called producers, meaning they produce their own food. Think of them as producing from scratch the bricks and boards needed to build a house, which is our analogy here for a cell. Based on their energy source for completing this task, they are categorized as photoautotrophs or chemoautotrophs. Contrast autotrophs with heterotrophs.

Binomial Nomenclature

The system we use to identify each unique species by a distinct, two-word name. The name is always italicized and written in Latin. The first word is the genus of the organism and is capitalized; the second word designates the particular species. Don't be fooled. The species name is actually both words together, not the second word alone. (Compare species identifier and species name below.) You are a member of the species Homo sapiens. Another member of our species, Carl Linnaeus, developed this system.

Blastospore

The opening in an embryo created very early in development through a process called gastrulation. Before gastrulation, the embryo is called a blastula and consists of a ball of cells of two types: cells on the outside (ectoderm) and cells on the inside (endoderm). Some of the cells in the outer layer of the blastula move inward. (Imagine pushing your finger into a poorly inflated balloon.) This creates a tube with an opening. This opening is the blastopore. Groups of animals are defined by whether their blastopore becomes their mouth or their anus later in development. It will become the mouth in protostomes and the anus in deuterostomes.

Blastula

An early stage in animal development. After an egg is fertilized, the single cell that results (a zygote) begins to divide. At first, it is a solid ball of cells. Then it becomes a hollow sphere as the inside becomes filled with fluid (a.k.a. blastocoel). This hollow sphere of cells is the blastula. Its next stage of development is gastrulation. In mammals, the blastula is a little bit different and is called a blastocyst.

Chemoautotrophs

Autotrophs that get their energy through chemical reactions that use inorganic molecules.

Chemoheterotrophs

Heterotrophs that get their energy through chemical reactions that use inorganic molecules.

Chemotrophs

Organisms that get their energy through chemical reactions that use inorganic molecules, like ammonia, iron, and sulfur. Think of them as batteries. Contrast them with phototrophs.

Chordata

A class of animals that are deuterostomes. At some point in their development, they have a notochord, which is where the word chordate comes from. A notochord is a rod made of cartilage that runs the length of the animal and acts as a skeleton. In vertebrates, it is replaced by bony vertebrae later in development. Chordates also, at some point in their lives, have a nerve cord located towards their backs (dorsally), pharyngeal (gill) slits, and a tail. Yes. We're chordates. You'll have to study developmental biology to learn more about your former tail.

Clade

A group of related organisms and their common ancestor. Clades are often diagrammed in cladograms.

Cladistics

Also known as phylogenetic systematics—a way of classifying organisms based on how recently they evolved from their most recent common ancestor. It does not take into account the similarities between organisms' physical/structural characteristics but relies heavily on genetic/molecular information.

Cladogram

A type of phylogenetic tree that shows taxonomic relationships based on organisms' most recent common ancestor. If phylogenetic trees are like family trees, with each new species being another family in the tree, a cladogram is a family tree with a single couple at its base.

Class

A taxon (or group of organisms) made of related orders

Classification

The act of placing things into related groups based on their similarities and differences; a grouping.

Coelom

(Pronounced "see- lum") an inner, fluid-filled space between the digestive tube and the outer wall of an organism. In humans, this space is where our inner organs (for example, kidneys) "float."

Common Ancestor

A species of organisms from which two or more other species have developed or descended, making them all related to each other genetically.

Convergent Evolution

A process that can create confusion for taxonomists because it involves the evolution of similar structures in two or more distantly related species that can make them look like they share a recent common ancestor. Often, it happens when the two (relatively) unrelated species are living in and adapting to similar environments. The fins of fish and whales are an example.

Domain

The highest, most inclusive level in the hierarchical organization of life. Domains are made up of kingdom(s). The hierarchical structure that is currently in use contains 3 domains.

Domain Archaea

The taxon (group of organisms) containing prokaryotic, unicellular organisms whose cell walls do not contain peptidoglycan (a protein or peptide with a sugar molecule attached). They are all autotrophs. Evolutionarily, this was thought to be the oldest domain; its name means "ancient things." This domain contains just one kingdom of the same name: Kingdom Archaea.

Domain Bacteria

The taxon (group of organisms) containing prokaryotic, unicellular organisms whose cell walls contain peptidoglycan (a protein or peptide with a sugar molecule attached). Most are decomposers; some are parasites that can cause disease; and some are autotrophs. This domain contains just one kingdom of the same name: Kingdom Bacteria.

Domain Eukarya

The taxon (or group of organisms) that includes all eukaryotic organisms. This domain contains the Kingdoms Protista, Fungi, Plantae, and Animalia.

Deuterostomes

A clade of animals that share a similar pattern of development in which the blastopore becomes the anus of the adult organism. This group contains the Phyla Echinodermata, Hemichordata, and Chordata. Contrast the deuterostomes with the protostomes.

Echinodermata

A phylum of deuterostomes within the Kingdom Animalia consisting of marine invertebrates with spiny (Greek: echinos) skin (Greek: dermis) and tube feet. They usually have several identical body parts that surround a central axis (they are radially symmetrical). Examples: sea stars and sea urchins.

Eubacteria

An older term for bacteria that you might still find in places. It means "true bacteria" (as opposed to the "weird" bacteria in the Domain Archaea).

Eukaryotes

Organisms whose cells contain nuclei, which contain their DNA, along with other specialized, membrane-bound organelles

Evolutionary Developmental Biology

"EvoDevo"—the study of how natural selection affects the genes that control animal development. At its heart is the understanding that organisms that are related to each other evolutionarily will share similar patterns of development. No, it's not the name of a new rap artist.

Family

A taxon (group of organisms) made up of related genera.

Gastrulation

An early developmental process during which the cells of an embryo move with respect to each other. The embryo begins this stage as a blastula with two types of cells, those on the outside of the ball of cells and those on the inside. Gastrulation involves the some of the outer cells pushing themselves into the ball to form a third layer of cells. (Think about pushing your thumb into an inflated balloon.) Gastrulation forms three germ layers. Watch it happen here.

Genus

(pl. genera) A taxon (group of organisms) made up of related species. An organism's genus name is also the first part of its species name.

Germ Layer

One of two to three layers of cells in an early animal embryo that eventually give rise to all of the different tissue types in the adult animal. The formation of germ layers is one of the first developmental processes that create differences in the embryo between one type of cell and another.

Hemichordata

An animal phylum of deuterostomes made up of immobile wormlike marine organisms with a three-part body plan and cilia around the mouth. Example: acorn worms (see picture).

Heterotrophs

Organisms that rely on other organisms to supply the organic raw materials they need to build their own complex organic molecules. They are also called consumers, because they consume other organisms. In our house analogy (see autotrophs), they break down other people's homes (abandoned or not, depending on the organism) to obtain the bricks and boards needed to build their own homes (or cells). Depending on how they obtain the energy they need to build their cells, heterotrophs are classified as chemoheterotrophs or photoheterotrophs. Contrast them with autotrophs.

Hierarchy

An organization system designed like a pyramid with each rank/level becoming less and less inclusive, more and more specific.

Homology

A similarity between two different species that is found by comparing their DNA or amino acid sequences or their structures and processes. The similarity exists because the species are derived from the same common ancestor and are therefore related evolutionarily. Contrast with homoplasy.

Homoplasy

A similarity between organisms of different species that is independent of a shared ancestry and is therefore due to convergent evolution, usually thanks to adaptation to similar environments. The two species' most recent common ancestor does not share their similarity. For example, hedgehogs and porcupines both have spiny skin but their common ancestor was a smooth skinned mammal. Contrast with homology.

Invertebrates

Animals without bony spines or "vertebrae." Contrast with vertebrates. Kingdom- A large, general taxon (group of organisms) made up of related phyla.

Kingdom Animalia

The eukaryotic taxon (group of organisms) that includes multicellular heterotrophs with complex body plans and diverse lifestyles. Most of them are quite mobile and have a well-coordinated nervous and muscular system, allowing them to react quickly to their environment. They usually reproduce sexually and begin life in an immature form.

Kingdom Archaea

Previously referred to as Kingdom Archaebacteria—the taxon (group of organisms) containing prokaryotic, unicellular organisms whose cell walls do not contain peptidoglycan (a protein or peptide with a sugar molecule attached). This kingdom is the only one in the Domain Archaea.

Kingdom Bacteria

Previously referred to as Kingdom Eubacteria—the taxon (group of organisms) containing prokaryotic, unicellular organisms whose cell walls contain peptidoglycan (a protein or peptide with a sugar molecule attached). Most are decomposers but some are parasites and can cause disease and some are autotrophs. This kingdom is the only one in the Domain Bacteria.

Kingdom Fungi

The taxon (group of organisms) containing eukaryotic heterotrophs that usually get their energy by decomposing dead organic material. They reproduce both asexually and sexually via spores. They can be unicellular or multicellular and their cell walls contain the sugar polymer, chitin. Their most famous member is the mushroom.

Kingdom Plantae

The taxon (group of organisms) that includes non-motile, eukaryotic photoautotrophs. They reproduce sexually, often through seeds. Their most famous member is a tie between the Christmas tree and grass.

Kingdom Protista

The taxon (group of organisms) thought to be the oldest kingdom of eukaryotes (evolutionarily). It includes a wide range of varied organisms, most of which are microscopic. They can be autotrophs or heterotrophs; asexual or sexual; unicellular, multicellular, or colonial. They are all mobile but have different forms of mobility, none of which is walking.

Molecular Systematics

A biological field that uses molecular techniques (such as DNA sequence comparison) to study and compare organisms and their evolutionary relationships.

Node

A branching point on a cladogram representing a recent common ancestor shared by all of the organisms branching up from it. It's like a fork in the road. It shows where two or more groups diverged from a common ancestor. The closer a node is to two species, the more recently they shared a common ancestor and vice versa.

Order

A taxon (group of organisms) made up of related families.

Photoautotrophs

Autotrophs that obtain their energy from sunlight.

Photoheterotrophs

Heterotrophs that obtain their energy from sunlight.

Phototrophs

Organisms that obtain their energy from sunlight by absorbing it through various pigments, like chlorophyll. Think of them as solar panels. Contrast them with chemotrophs.

Phylogenetic Tree

A branched, graphical representation of the evolutionary relationships among a group of related species. Think of it as a family tree for non-human organisms.

Phylogeny

The evolutionary path that traces the history of a species. It's the "story" about how a species came to be the way it is.

Phylum

A taxon (group of organisms) made up of related classes.

Population

All of the individuals of a particular species living in the same area, or geographic range, at the same time. For instance, bluegills living in two different lakes would make up two different populations of the one species.

Prokaryotes

Unicellular organisms whose DNA is not contained within a nucleus. They also only have a single copy of their genes (they are haploid) and have no organelles.

Protist

A member of the Kingdom Protista.

Protostomes

Animals whose mouths develop from the first hole (blastopore) created during the early development of the embryo. Compare them to deuterostomes.

Reversal

An evolutionary "just kidding!" It happens when a trait reverts back to an earlier form, creating an example of homoplasy.

Shared Ancestral Character

A plesiomorphic character—a trait shared by a current species and an evolutionarily older one that suggests that they share a common ancestor. For example, we call bony vertebrae a shared ancestral character of all vertebrates because all vertebrates came from the same common ancestor, which also had vertebrae.

Shared Derived Character

A synapomorphic character—a trait shared by two or more taxa (groups of organisms) and their most recent common ancestor but not by earlier ancestors, giving us an idea as to when the trait was derived, or developed. For example, amniotic eggs are found in reptiles, birds, and mammals but not other vertebrates like amphibians and fish. This suggests that amniotic eggs are an evolutionary adaptation that was derived by a common ancestor sometime after amphibians and fish evolved.

Species

A group of organisms that are very similar in the way they look and act thanks to their shared genes and ancestry. It is the narrowest classification of organisms in the hierarchy of life. Members of a species can breed with one another and do not successfully breed with members of other species.

Species Identifier

A specific epithet—in the binomial system of nomenclature, this is the second word in an organism's name. For example, sapiens is the species identifier for our species Homo sapiens. Think of it as an organism's last name.

Species Name

The two-word name for a species. It is composed of the name of the genus to which the organism belongs followed by the species identifier.

Spores

Single cells released by some bacteria and plants and most fungi that can develop into new organisms once the conditions are right. They are an asexual form of reproduction because they do not need to be fertilized to create an adult organism. They are resistant to damage from desiccation (drying out), heat, and many other threats. They allow a population of organisms to be seemingly killed off but to revive again once its spores germinate.

Subspecies

Refers to a taxon/group of organisms that is even more specific than a species. Two subspecies within the same species can be distinguished genetically but they can still interbreed successfully. Example: domestic cats are now thought to be a subspecies of the wild cat (Felis silvestris), changing their official name from Felis catus to Felis silvestris catus.

Systematics

The study of the diversity of organisms and how they are related evolutionarily. Taxonomy is one part of this field. (Comparative genomics is another, for example.)

Taxon

(pl. taxa) A category used to classify a group of organisms.

Taxonomy

The science of naming, describing, and classifying living organisms. Taxonomy is one part of the larger field of systematics.

Tissue

A group of cells within a multicellular organism working together to fulfill a common goal. Skin is the clearest example, but muscles and bones are good examples, too. We are usually talking about an animal when we talk about tissues, but they're also present in plants.

Variety

A category of plants that is even more specific than a species. They are genetically distinct but can interbreed. Beefsteak, plum, grape, and cherry tomatoes, for example, are all different varieties of the same species (Solanum lycopersicum). Does Heinz use 57 varieties of tomatoes in their ketchup? We don't know. You'll have to ask them.

Vertebrates

Animals with bony spines or "vertebrae." Vertebrates are actually a subphylum of the Phylum Chordata. Fish, amphibians, reptiles, birds, and mammals are all vertebrates. That means you.
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