An introduction to animal diversity Flashcards
Hox genes
They control early development in animal groups. Mutations in these genes could have resulted in rapid changes in animal body plans.
Early evolution of animals began in…
The cambrian radiation.
Ectoderm
The outer layer which gives rise to the body covering and the nervous system.
Endoderm
The inner layer, which lines the gut and other digestive organs.
Mesoderm
The middle layer, which gives rise to muscle, skeletal structures and most other body structures.
Acoelomate
Animals that have no cavity.
Coelomate
Animals that have a true coelom, a body cavity completely lined with mesoderm.
Pseudocoelomate
Animal that have a body cavity that is not completely lined with mesoderm.
Protostomes
Mollusks, annelids and arthropods. They undergo spiral cleavage, which is also determinate (the fate of each cell is fixed very early). The blastopore develops into the mouth.
Deutorostomes
Echinoderms and chordates. They undergo radial cleavage, which is indeterminate. The blastopore typically becomes the anus.
Hemichordates
They are marine deuterostomes with a three-part body, including proboscis, collar, and trunk.
Chordates
They include the tunicares, lancelets and vertebrates. At some time in its life cycle, a chordate has a flexible, supporting notochord, a dorsal tubular nerve cord, a muscular postanal tail and an endostyle or thyroid gland.
Vertebrates
They have a vertebral column composed of vertebrae. Neural crest cells are embryonic cells important in the development. They have complex brain, a muscular pharynx and muscles attached to the endoskeleton.
Tetrapods
They give rise to land vertebrates. They include the amphibian clades and the amniote lineage.
Amniotes
Terrestrial vertebrates. Adaptations for life on land include: 1, the evolution of the amniotic egg with its shell and amnion, 2, internal fertilization and 3, a body covering that retards water loss and physiological mechanisms that conserve water.
