Chapter 30- An Introduction to Animals

Epithelium

is a layer of tightly joined cells that covers the interior and /or exterior surface of the animal.

Viviparous

" (live- bearing) "species such as humans and most other mammals nourish embryos inside the body and give birth to live young.

Metamorphosis

is a drastic change of form from one developmental stage to another.

Lophotrochozoans

grow continuously when conditions are good.

Spicules

are stiff spikes of silica or calcium carbonate (CaC03) that, along with collagen fibers, give structural support to the ECM.

Ectoparasites

live on the outside of their hosts.

Oviparous

" (egg- bearing) "species such as chickens and crickets deposit fertilized eggs.

Ecdysozoans

grow by shedding their external skeletons or outer coverings and expanding their bodies.

Cephalization

is the evolution of a head, or anterior region, where structures for feeding, sensing the environment, and processing information are concentrated.

Colonies

are groups of individuals that are attached to each other.

large mass of neurons

The that is located in the head, and that is responsible for processing information to and from the body, is called the cerebral ganglion or brain.

sessile polyp

Many cnidarians have a life cycle that includes both a(n) form that reproduces asexually and a free- floating medusa that reproduces sexually.

Herbivores

that feed on plants or algae.

indirect development

During , embryogenesis produces larvae.

evolution of αnimαls

The is more complicated than α smooth transition from simple to complex.

Ovoviviparous

" (egg- live- bearing) "species such as guppies and garter snakes retain eggs inside the body during early development, but the growing embryos are nourished by egg yolk instead of by nutrients transferred directly from the mother, as in viviparous species.

germ layer

In triploblasts, however, there is a(n) called mesoderm " (middle- skin) "between the ectoderm and endoderm.

multicellular eukaryotes

All animals are whose cells lack cell walls but have an extensive extracellular matrix (ECM)

Sponges

do not have complex tissues, groups of similar cells that are organized into tightly integrated structural and functional units.

Endoparasites

live inside their hosts and usually have simple, wormlike bodies.

Cnidarians

have nerve cells at are mostly organized into a diι fuse arrangement called a nerve net.

Segmentation

is defined as the division of the body or a part of the body into a series of similar structures.

radiation of animals

The began around 550 million years ago during an event called the Cambrian explosion.

embryonic tissues

The are organized in layers, called germ layers.

diploblasts

In 1ese germ layers are called ectoderm " (outer skin) "and endoderm ("inner- skin)

Cambrian explosion

The radiation of animals began around 550 million years ago during an event

benthic

they live at the bottom of aquatic environments

sessile

adults live permanently attached to a substrate rather than moving freely