Animal Kingdom

Multicellular organisms

Organisms composed of multiple cells, which work together for the organism's function.

Heterotrophic

Organisms that obtain their nutrients by consuming other organisms.

Nervous system

A system that coordinates body activities by transmitting signals throughout the body.

Muscular system

A system that allows movement through the contraction of muscles.

Sexual reproduction

A method of reproduction that involves the combination of genetic material from two parents.

Asexual reproduction

A reproductive process that involves only one parent, producing genetically identical offspring.

Cleavage

The rapid cell division of a fertilized egg into smaller cells.

Blastula

A hollow ball of cells formed during the early stages of embryonic development.

Gastrulation

The process in which the blastula folds inward to form the gastrula, establishing embryonic germ layers.

Ectoderm

The outermost germ layer that develops into the skin and nervous system.

Mesoderm

The middle germ layer that forms muscles, bones, and the circulatory system.

Endoderm

The innermost germ layer that gives rise to the digestive tract and respiratory system.

Incomplete metamorphosis

A type of development involving three stages: egg, nymph, and adult.

Complete metamorphosis

A type of development involving four stages: egg, larva, pupa, and adult.

Radial symmetry

Body symmetry around a central axis, allowing equal access to the environment.

Bilateral symmetry

Body plan that can be divided into mirror-image halves, facilitating directional movement.

Asymmetry

Lack of symmetry commonly seen in simpler organisms.

Cambrian explosion

A rapid increase in animal diversity and complexity approximately 541 million years ago.

Phylum Porifera

A group of multicellular organisms known as sponges, characterized by a lack of true tissues.

Choanocytes

Specialized sponge cells that create water currents and filter food particles.

Osculum

The large opening at the top of the sponge where filtered water exits.

Spongocoel

The central cavity in a sponge where water enters and is filtered.

Hermaphroditism

Having both male and female reproductive organs.

Cnidocytes

Specialized cells in cnidarians containing stinging structures used for defense.

Polyp

The sessile body form of certain cnidarians.

Medusa

The motile body form of certain cnidarians, typically bell-shaped.

Phylum Mollusca

A diverse group of soft-bodied animals, often with shells, including snails and octopuses.

Gastropoda

A class of mollusks that includes snails and slugs, often characterized by a coiled shell.

Bivalvia

A class of mollusks consisting of clams, oysters, and mussels, typically with two hinged shells.

Cephalopoda

A class of mollusks that includes squids, octopuses, and cuttlefish, known for their advanced nervous systems.

Superphyla Ecdysozoa

A clade that includes organisms that grow by molting their exoskeleton.

Phylum Nematoda

A group of roundworms characterized by cylindrical, unsegmented bodies.

Phylum Arthropoda

The largest animal phylum, characterized by segmented bodies, jointed appendages, and exoskeletons.

Deuterostomia

A clade defined by embryonic development where the anus forms from the blastopore.

Echinodermata

A phylum of marine organisms characterized by radial symmetry and a unique water vascular system.

Chordates

Animals characterized by the presence of a notochord, dorsal nerve cord, and pharyngeal slits at some stage.

Notochord

A flexible rod-like structure that provides support during the development of chordates.

Pharyngeal slits

Structures that may develop into gills or other features in chordates.

Tetrapods

Vertebrates that have four limbs, evolved from lobe-finned fishes.

Amniotes

Animals that have an amniotic egg, allowing for reproduction in terrestrial environments.

Endostyle

A structure in chordates that is involved in filter feeding.

Ectothermy

The dependence on external sources of body heat, characteristic of reptiles.

Synapsids

A group of animals characterized by single temporal fenestra in the skull, including mammals.

Natural selection

The process through which organisms better adapted to their environment tend to survive and reproduce.

Adaptive radiation

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

Hox genes

Genes that regulate the development of body structures and segmentation during embryonic development.

Mass extinction

Events that lead to the rapid loss of a large number of species, impacting evolutionary trajectories.

Morphological data

Physical characteristics used to determine evolutionary relationships.

Molecular data

Genetic information used to clarify evolutionary relationships among species.

Phylogenetic tree

A diagram that represents evolutionary relationships among different species.