Campbell Biology Chapter 32

Points of Agreement

1. All animals share a common ancestor 2. Sponges are basal animals 3. Eumetazoa is a clade of animals with true tissues 4. Most animal phyla belong to the clade Bilateria 5. Chordates and some other phyla belong to the clade Deuterostomia

Cambrian explosion

A burst of evolutionary origins when most of the major body plans of animals appeared in a relatively brief time in geologic history; recorded in the fossil record about 535 to 525 million years ago.

larva

A free-living, sexually immature form in some animal life cycles that may differ from the adult in morphology, nutrition, and habitat.

Ecdysozoans

A major lineage of protostomes (Ecdysozoam) that grow by shedding their external skeletons (molting) and expanding their bodies. Includes arthropoda (insects) and nematoda (roundworms).

indeterminate cleavage

A type of embryonic development in deuterostomes, in which each cell produced by early cleavage divisions retains the capacity to develop into a complete embryo.

determinate cleavage

A type of embryonic development in protostomes that rigidly casts the developmental fate of each embryonic cell very early.

Sponges are basal animals

Among the extant taxa, sponges branch from the base of both animal trees.

coelomates

An animal that possesses a true coelom (a body cavity lined by tissue completely derived from mesoderm). - ex. earthworm

pseudocoelomates

An animal whose body cavity is lined by tissue derived from mesoderm and endoderm. ex. round worm

Ediacaran biota

An early group of soft-bodied, multicellular eukaryotes known from fossils that range in age from 565 million to 550 million years old.

trochophore larva

Distinctive larval stage observed in some lophotrochozoan animals, including some annelids and molluscs.

lophophore

In some lophotrochozoan animals, including brachiopods, a crown of ciliated tentacles that surround the mouth and function in feeding.

Lophotrochozoans

One of the two groups of protostomes identified as a clade by molecular evidence. Lophotrochozoans include organisms that have lophophores or trochophore larvae.

triploblastic

Possessing three germ layers: the endoderm, mesoderm, and ectoderm. Most eumetazoans are triploblastic.

Deuterostome development

Radial and indeterminate cleavage, folds of archenteron form coelom, anus develops from blastopore.

Hox genes

Series of genes that controls the differentiation of cells and tissues in an embryo

Protostome development

Spiral and determinate cleavage, solid masses of mesoderm split and form coelom, mouth developes from blastopore.

diploblastic

Term for animals with just two germ layers - the ectoderm and endoderm. Include Cnidarians and comb jellies.

archenteron

The endoderm-lined cavity, formed during gastrulation, that develops into the digestive tract of an animal.

blastula

The hollow ball of cells marking the end stage of cleavage during early embryonic development

endoderm

The innermost of the three primary germ layers in animal embryos; lines the archenteron and gives rise to the liver, pancreas, lungs, and the lining of the digestive tract

ectoderm

The outermost of the three primary germ layers in animal embryos; gives rise to the outer covering and, in some phyla, the nervous system, inner ear, and lens of the eye

cleavage

The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane; specifically, the succession of rapid cell divisions without growth during early embryonic development that converts the zygote into a ball of cells.

ventral side

The underside, belly, or the lower body surface

body cavity

a fluid- or air-filled space between the digestive tract and the body wall

gastrula

a stage of embryonic development characterized by the differentiation of the cells into the ectoderm and endoderm germ layers and by the formation of the archenteron

Eumetazoa is a clade of animals with true tissues

all animals except for sponges and a few other groups belong to a clade of eumetazoans(true animals). Basal eumetazoans are diploblastic and generally have radial symmetry

acoelomates

animals, such as flatworms, that do not have a body cavity

coelom

body cavity

radial symmetry

body plan in which body parts repeat around the center of the body; characteristic of sea anemones and sea stars

bilateral symmetry

body plan in which only a single, imaginary line can divide the body into two equal halves; characteristic of worms, arthropods, and chordates

All animals share a common ancestor

both trees indicate that animals are monophyletic, forming a clade called Metazoa

choanoflagellets

closest living relatives to the animalia

cephalization

concentration of sense organs and nerve cells at the front of an animal's body (head and brain)

sessile

describes an organism that remains attached to a surface for its entire life - radial animals

gastrulation

developmental process in which three distinct cell layers form in an embryo: the endoderm, mesoderm, and ectoderm

planktonic

drifting passively with currents - radial animals

Germ layers

ectoderm, endoderm, mesoderm

blastopore

in a gastrula, the opening of the archenteron that typically develops into the anus in deuterostomes and the mouth in protostomes.

animals

multicellular, heterotrophic eukaryotes with tissues developed from embryonic layers

anterior end

the end of an animal that contains its head

posterior end

the end of an animal that contains its tail

metamorphosis

the marked and rapid transformation of a larva into a juvenile, which resembles the adult but is not yet sexually mature.

mesoderm

the middle germ layer that develops into muscle and bone and cartilage and blood and connective tissue

collagen

the most abundant structural protein that helds together the animal cells

dorsal side

top side, back of an animal - the spine side, away from the abdomen