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Animal Evolution and Diversity

Animal Evolution and Diversity

Animal Evolution and Diversity Terms

Get down with the lingo

Zygote

The cell formed when sperm and egg first meet

Acoelomates

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

Amniotes

Animals whose young develop inside a fluid-filled sac, called an amnion.

Anthropoids

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

Atrium

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

Autotroph

Organism that can make its own food, like plants.

Bipedal

Moving around on two legs.

Biramous

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.

Bilateria

The group of animals with bilateral symmetry.

Blastula

Hollow ball of cells the zygote becomes after going through cleavage.

Cephalization

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.

Chordate

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

Cilia

Long, thin part of a cell that sticks outward and generally helps in movement. Similar to a flagella, but has a different structure and cilia are usually shorter and numerous, where flagella are longer and there are fewer to a cell.

Cladogram

A family tree showing the relationships between organisms.

Cleavage

The process of a zygote dividing into more cells.

Coelom

Internal space in an animal that forms in the embryo.

Coelomates

Animals without a coelom.

Deuterostomes

One of two kinds of bilateria. Deuterostomes: 1) go through indeterminate cleavage; 2) have a blastopore that becomes the anus (versus mouth) and 3) form a coelom that remains part of the mesoderm.

Diapsid

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.

Diploblastic

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

Diploid

Cell with two sets of chromosomes.

Ectotherms

Animals that get body heat from their surroundings.

Embryo

Multicellular early form of an organism in development.

Endotherms

Animals that can produce their own body heat.

Eukaryotes

Single-celled or multi-celled organisms whose cells have a nucleus and other organs enclosed by a membrane.

Eumetazoa

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

Eutherians

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

Evolution

The process of change organisms go through over time, leading to changes in organisms and to new organisms.

Exoskeleton

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

Flagella

Extension of a cell that looks like a little whip and can be used in movement or to move fluid

Fusiform

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

Gametes

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

Ganglia

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 layers of the blastula. "Germ" means the beginning of something and each of these layers is the beginning of specific tissues.

Gestation

The process of an organism developing until birth.

Haploid

Cell with one set of chromosomes.

Hermaphrodite

Animal with both male and female reproductive organs.

Heterotroph

Organism that eats other organisms, like animals.

Hominids

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

Hydrostatic Skeleton

Firm internal surface where muscles attach. This skeleton has no bones—the hard part is produced by internal water pressure.

Invertebrates

The group of animals without a backbone. This is the majority of animals.

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.

Marsupials

Mammals that carry their young internally for only a short time, after which the rest of development happens in an external pouch.

Medusa

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.

Metamere

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

Metamorphosis

Process of changing from one form to another. This is part of the life cycle of some animals, for example frogs, which change from water-breathing tadpoles into air-breathing adult frogs.

Monotremes

Mammals characterized by not having a placenta and instead laying eggs.

Nephridia

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.

Parapodia

Feet-like extensions on some annelids.

Parazoa

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.

Pheromones

Chemicals produced by an organism that cause a behavioral response in members of the same species.

Phylum (plural = Phyla)

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

Placenta

An organ created along with the embryo. It connects the developing animal to the mother's bloodstream, providing food and oxygen.

Prokaryotes

Single-celled organisms without organs or a nucleus separated by membranes.

Prosimians

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

Protostomes

One of the two kinds of bilateria. Protostomes: 1) go through determinate cleavage; 2) have a blastopore becomes the mouth (versus anus) and 3) form a coelom that splits off completely from the mesoderm (middle germ layer).

Pseudocoelomates

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.

Radiata

The main branch of animals with radial symmetry.

Radula

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

Septa

Walls that divide the segments of an animal like a worm.

Sessile

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.

Setae

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

Tagmata

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

Synapsid

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.

Tetrapods

Animals with four limbs.

Therapsids

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.

Trachea

A tube that carries air inside the body.

Triploblastic

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

Ventricle

Chambers of the heart that receive blood from atria and send it out.

Vertebrate

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

Zygote

The cell formed when sperm and egg first meet

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