Chapter 32 Vocabulary Flashcards
Cleavage
A succession of mitotic cell divisions without cell growth between the divisions
Tissues
Groups of cells that have a common structure, function, or both
Blastula
Multicellular stage formed after cleavage
Gastrulation
Process during which the layers of embryonic tissues that will develop into actual body parts are produced
Gastrula
The resulting developmental stage during which the layers of embryonic tissue develop into actual body parts
Larva
A sexually immature form of an animal that is morphologically distinct from the adult, usually eats different food, and may even have a different habitat than an adult
Metamorphosis
A developmental transformation that turns the animal into a juvenile that resembles an adult but is not yet sexually mature
Homeoboxes
All animals have developmental genes that regulate the expression of other genes, and many of these regulatory genes contain sets of DNA sequences called homeoboxes
Hox genes
Play important roles in the development of animal embryos, controlling the expression of dozens or even hundreds of other genes that influence animal morphology
Ediacaran biota
An early group of soft-bodied multicellular eukaryotes
Cambrian explosion
A way of animal diversification occurred 535-525 million years ago, during the Cambrian period of the Paleozoic era
Body plan
A particular set of morphological and developmental traits, integrated into a functional whole - the living animal
Plan
Body plans do provide a succinct way to compare and contrast key animal features
Radial symmetry
The type of symmetry found in a flower pot
Bilateral symmetry
A bilateral animal has two axes of orientation: front to back and top to bottom
Dorsal
Top side
Ventral
Bottom side
Anterior
Front end
Posterior
Back end
Cephalization
An evolutionary trend: many animals with a bilaterally symmetrical body plan have sensory equipment concentrated at the anterior end, including a central nervous system (“brain”) in the head
Germ layers
Layers that form the various tissues and organs of the body
Ectoderm
The germ layer covering the surface of the embryo, gives rise to the outer covering of the animal and, in some phyla, to the central nervous system
Endoderm
The innermost germ layer, lines the pouch that forms during gastrulation (the archenteron) and gives rise to the lining of the digestive tract (or cavity) and organs such as the liver and lungs of vertebrates
Diploblastic
Animals that have only ectoderm and endoderm germ layers. Include animals called cnidarians as well as comb jellies, no mesoderm
Mesoderm
A third germ layer which fills much of the space between the ectoderm and endoderm. In bilaterally symmetric animals
Triploblastic
Having three germ layers
Body cavity
A fluid – or air filled space located between the digestive tract and the outer body wall
Coelem
Body cavity between the digestive tract and outer body wall
Coelomates
Animals with a true coelom
Pseudocoelomates
Some triploblastic animals have a body cavity that is formed from mesoderm and endoderm. Such a cavity is called a “pseudoderm” and the animals that have one are called pseudocoelomates
Acoelomates
Triploblastic animals that lack a body cavity altogether
Grade
A group whose members share key biological features
Clade
A group that includes an ancestral species and all of its descendants
Protostome development
In animals, a developmental mode mode distinguished by the development of the mouth from the blastopore: often also characterized by spiral cleavage and by the body cavity forming when solid masses of mesoderm split
Deuterostome development
In animals, a developmental mode distinguished by the development of the anus from the blastopore; often also characterized by radial cleavage and by the body cavity forming as out pockets of mesodermal tissue
Spiral cleavage
Many animals with protostome development undergo spiral cleavage, in which planes of cell division and diagonal to the vertical axis of the embryo; as seen in the eight-cell stage of the embryo, smaller cells are centered over the grooves between larger, underlying cells
Determinate cleavage
Determined developmental fate of each embryonic cell very early
Radial cleavage
Deuterostome development predominantly characterized by radial cleavage. The cleavage planes are either parallel or perpendicular to the vertical axis of the embryo; as seen at the eight-cell stage, the tiers of cells are aligned one directly above the other
Indeterminate cleavage
Each cell produced by early cleavage divisions retains the capacity to develop into a complete embryo
Archenteron
During gastrulation, an embryos developing digestive tube initially forms as a blind pouch, the archenteron, which becomes the gut
Blastopore
The indentation that during gastrulation leads to the formation of the archenteron
Protostome
First mouth
Eumetazoans
“True animals”, a Clade that all animals except a few sponges and a few others belong to
Bilaterians
Bilateral symmetry and the presence of three germ layers are shared derived characters that help define the Clade Bilateria. This Clade contains the majority of animal phyla, and its members are known as bilaterians
Ecdysozoans
Ecdysozoa refers to a characteristic shared by nematodes, arthropods, and some of the other ecdysozoan phyla that are not included in our survey. Member of a group of animal phyla identified as a Clade by molecular evidence. Many are molting animals
Lophotrochozoan
Member of a group of animal phyla identified as a clade by molecular evidence. Lophotrochozoans included organisms that have lophophores or trochophore larvae
Lophophore
A crown of ciliated tentacles that function in feeding
Trochophore larva
Distinctive larval stage observed in some lophotrochozoan animals, including some Annelida and molluscs
Ecdysis
The process of shedding old exoskeleton
