Animal Evolution and Diversity

Flashcards covering animal evolution, symmetry, germ layers, and various animal phyla like Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Mollusca, Arthropoda, and Echinodermata, based on lecture notes.

Cambrian explosion

The radiation of animals (metazoans) began approximately 550 million years ago during this event.

Opisthokont

The evolutionary ancestors to animals were a lineage of single-celled protists in this clade.

Monophyletic Clade

Animals are classified as this, meaning they have a single common ancestor.

Ingestive Heterotrophs

Animals obtain nutrition as this, consuming other organisms.

Asymmetry

The term for animals lacking a fixed point of symmetry.

Spherical Symmetry

The type of symmetry where body parts radiate from a central point, allowing for an infinite number of planes of symmetry.

Radial Symmetry

Animals with this type of symmetry have one main oral-aboral axis, common in diploblastic animals.

Bilateral Symmetry

Animals with this type of symmetry have one plane of symmetry along the body axis.

Cephalization

The evolutionary trend associated with bilateral symmetry, involving the concentration of nervous tissue and sensory organs at the anterior end.

Ectoderm

The outer germ layer in animal embryos, forming the skin and nervous system.

Endoderm

The inner germ layer in animal embryos, forming the lining of the gut and digestive organs.

Mesoderm

The middle germ layer in triploblastic animals, allowing for a diversity of tissues like muscles and skeletal elements.

Porifera (Sponges)

Animals in this phylum lack true tissues, organs or organ systems and filter feed using choanocytes.

Choanocytes

Specialized cells in sponges that use flagella to move water and capture food particles.

Spicules

Supportive endoskeletal structures found in sponges.

Nematocyst

The defining synapomorphy of cnidarians; a specialized stinging organelle.

Polyp and Medusa

The two body forms exhibited by cnidarians.

Pseudocoelomate

A body cavity not fully lined by mesoderm.

Coelomate

A true body cavity completely lined with mesoderm.

Acoelomate

Bilaterians without a body cavity.

Protostomes

These bilaterians development have the 'mouth first'.

Deuterostomes

These bilaterians development have the 'mouth second'.

Platyhelminthes

Phylum containing flatworms that are acoelomate.

Nematoda

Phylum containing roundworms that are pseudocoelomate.

Annelida

Phylum containing segmented worms that are coelomate.

Mollusca

Phylum that is characterized as soft-bodied.

Arthropoda

Phylum that is the most abundant and diverse.

Molting/Ecdysis

The periodic shedding of the exoskeleton of arthropods

Chelicerata

These arthropods include spiders, ticks, and scorpions.

Crustacea

These arthropods include crabs, lobsters, and crayfish.

Hexapoda

These arthropods include insects.

Myriapoda

These arthropods include centipedes and millipedes.

Echinodermata

Deuterostomes characterized by calcareous plates and a water-vascular system.