MODULE 13: ANIMALS- INVERTEBRATES PART 1

What are the four basic characteristics shared by all animals?

All animals are multicellular, eukaryotic, heterotrophic, and lack cell walls.

Invertebrates

Animals that lack backbones.

Vertebrates

Animals that possess a backbone.

What percentage of all animal species are invertebrates?

About 95%.

Symmetry in animals refers to?

The arrangement of body parts in relation to a central axis.

Spherical symmetry

An organism that can be cut into identical halves by any cut through its center.

Radial symmetry

An organism that can be cut into identical halves by any longitudinal cut through its center.

Bilateral symmetry

An organism that can only be cut into two identical halves by a single longitudinal cut along its central axis.

What is cephalization?

The concentration of sense organs and nerves in the head of an animal.

Phylum Porifera

The phylum that includes sponges, which are asymmetrical.

Epidermis in sponges

The outer layer of cells designed to provide protection.

Endodermis in sponges

The inner layer of cells.

Mesenchyme

The jellylike substance that separates the epidermis from the inner cells of the sponge.

Gemmule

A cluster of cells encased in a hard, spicule-reinforced shell in sponges.

Phylum Cnidaria

Includes organisms like jellyfish and corals, characterized by radial symmetry.

Polyp (Cnidaria)

The sessile, tubular form of a cnidarian with mouth and tentacles at one end.

Medusa (Cnidaria)

The free-swimming, bell-shaped form of a cnidarian.

Mesoglea

The jellylike substance that separates the epithelium cells in a cnidarian.

Nemotocysts

Small capsules that contain toxins used by cnidarians to catch prey.

Phylum Annelida

Known as segmented worms, featuring a segmented body with bilateral symmetry.

Clitellum

Barrel-shaped swelling in annelids that plays a crucial role in reproduction.

Closed circulatory system

A system in which blood stays in vessels designed to transport necessary substances.

Hermaphroditic

An organism possessing both male and female reproductive organs.

Planarians

Flatworms that can reproduce sexually or asexually through regeneration.

Regeneration

The ability to regrow a missing part of the body.

Phylum Mollusca

Includes soft-bodied animals, usually with a shell, such as snails and octopuses.

Open circulatory system

A system in which blood is pumped through vessels into body cavities.

Mantle

A sheath of tissue that encloses vital organs in mollusks and produces shells.

Foot (Mollusca)

A muscular organ used for locomotion, varying in form among different mollusks.

Radula

An organ covered in teeth used by mollusks to scrape food into their mouths.

Gastropods

Mollusks like snails that typically have a single shell.

Bivalves

Mollusks with two shells.