Study Guide

Animal Evolution and Diversity Terms

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Animal Evolution and Diversity Terms


Animals with a coelom. The coelom develops from the mesoderm.


Birds, reptiles, and mammals. Their eggs require special membranes because they develop on land.


Primates that more resemble human form, like monkeys, apes, and humans.


Entry chamber and name for the chambers of the heart where blood first enters.


Organisms that know how to cook for themselves, otherwise known as organisms that can make their own food from sunlight, or from other chemicals like ammonia or hydrogen sulfide.


Moving around on two legs.


Two branches splitting off from one, as in the legs of crustaceans.

Bilateral symmetry

A shape where there are recognizable right and left, top and bottom and front and back. This is like an airplane.


The group of animals with bilateral symmetry.


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.


Increasing tendency to put all the sensory organs and a centralized nervous system at the front end of an organism. Certain branches of the animal tree go this direction.


Animals with: a notochord, a hollow nerve cord, pharyngeal slits and a tail. This includes vertebrates.


(singular: cilium) Medusa-like projections, composed of microtubules in a "9 plus 2" arrangement (9 pairs in a circle surrounding 2 more microtubules) that move fluid around a cell. Prokaryotes have them too, but the "hair" is totally different.


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.


The process of a zygote dividing into more cells.


(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."


Animals without a coelom.


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.


Ancestral reptile whose name is based on its skull having two openings on either side of the head. Dinosaurs and modern reptiles descended from diapsids.


An embryo with two ("diplo-") germ layers.


The characteristic of having two sets of chromosomes. In most cases, with the exception of some plants, all somatic, or body, cells in a sexually reproducing organism are diploid.


Animals which receive heat primarily from external sources (reptiles, amphibians, and fish).


Multicellular early form of an organism in development.


Animals which create their own heat (mammals and birds).


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


The other branch in the animal family tree. It means "true animals," those with all the characteristics of animals.


Mammals whose young complete their entire development internally in a placenta; also called placental mammals.


A gradual change in genotype that happens over numerous generations that results in a phenotypic change.


Hard structure on the outside of many invertebrates, for instance insects, spiders, and crustaceans, that provides support.


The whip-like tail that a sperm has. This powerful engine propels the sperm over huge distances.


Body shape like a fish or dolphin, like a sleek, flattened tube with ends that come to a point.


The single-celled reproductive cells that make a diploid organism. Sperm and eggs are gametes.


Bunch of nerve cells working together to control something gastrulation—process of the single layer of cells that makes up the blastula, dividing into multiple layers of cells.

Germ Layers

The first cells in an embryo that have a destiny. The three layers: ectoderm, endoderm, and mesoderm each have a different future.


The process of an organism developing until birth.


The characteristic of having one set of unpaired chromosomes. Gametes (eggs and sperm) in a sexually reproducing organism are haploid.


An animal that can make both the male and female gametes. A Jack/Jill of all trades.


Organisms that can't cook, and may not even be able to microwave. These cells need to eat other organisms or already-prepared organic matter to survive.


Humans and human ancestors, characterized by being bipedal and having developed brains.

Hydrostatic skeleton

A hydrostatic skeleton is a fluid-filled cavity surrounded by muscles. Muscle constriction changes the animals shape, causing movement. Think jellyfish.


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

Lateral line system

Line of sensory organs down each side of a fish that can detect vibrations and changes in water pressure.

Malphigian tubes

Tubes inside insects that take wastes to the outside.


A special type of mammal that delivers undeveloped young and then carries them in a pouch for further development. Kangaroos and Koala bears are marsupials.


One form of the Cnidarians, which is like a floating sack with tentacles. The medusa is a reverse of the polyp, with tentacles pointing down. Medusas float freely.


A segment of a worm. The metameres are like repeating units that line up to make up a whole organism.


Complete transformation in shape, form, or substance


Special type of mammals that lay eggs, like the platypus.


Excretory tube in earthworms and mollusks polyp—one form of the Cnidarians, which is shaped like a tube with tentacles pointing up. Polyps generally attach to something.


Feet-like extensions on some annelids.


One of the first two branches in the animal family tree. It means "sort-of an animal"—parazoa have most, but not all characteristics of animals.


Chemicals that are released by some animals, often as a part of a courtship ritual. Mmm, smells like someone is available.

Phylum (plural = phyla)

The second level of organization for all life. The first is kingdom.


The connection between mother and fetus in mammals through which the fetus gets nutrition and gas and waste exchange.


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.


A group of tree-dwelling primates that least resemble humans, including lemurs, lorises, and tarsiers.


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


Animals with a coelom that comes only partially from the mesoderm.

Radial Symmetry

A shape where all sides are the same, but there is a distinct top and bottom. This is like a pumpkin.


The main branch of animals with radial symmetry.


Mouthpart in mollusks that is used for scraping food off surfaces.


(singular: septum) In fungi, division between hyphae cells of "septate hyphae" that still have small take-out windows to allow nutrients, like burgers and fries, to be passed between hyphae cells


An animal that doesn't move around. It may have tentacles or other parts that move, but the organism as a whole stays in one place.


Bristles on the outside of some invertebrates like annelids (worms) and insects.


Distinct section of an arthropod body, usually with a unique purpose, for example the head.


Ancestral reptile who name is based on its skull having one opening on either side of the head. A synapsid was an ancestor of mammals.


Animals with four limbs.


Descendants of the synapsids that led to mammals torsion—a special kind of development in snails where the embryo grow unevenly so the tail end finishes up above the head. The tail end makes the shell, which ends up on top.


The windpipe, a tube connecting the mouth to the bronchi.


An embryo with three ("triplo-") germ layers.


The ventricle is where blood exits the heart. This has to be the strongest part of the heart because it needs to provide the force to get the blood where it needs to go and back to the heart again.


Chordate animals that also have a skeletal spine made of parts called vertebrae.


A fertilized egg.

Roots of Common Terms in Animal Evolution and Diversity


G = Greek, L = Latin, F = French

Blastula, Blastopore

blastos = sprout (G), pore = hole, opening


cilia = eyelashes (L)


eu = true (G); karyon = nucleus (G)


evolvere = unrolling (L)


meta = together (G); mere = part (G)


pro = before (G); karyon = nucleus (G)


species = kind (L)


vertebratus = joint of the spine (L)

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