KINGDOM ANIMALIACharacteristics of

AnimalsJanuary 16th, 2007

Characteristics of Life1. Living things are organized.2. Living things are made up of cells.3. Living things metabolize.4. Living things maintain an internal

environment.5. Living things grow.6. Living things respond.7. Living things reproduce.8. Living things evolve.

Seven Levels of

Taxonomic Classificatio

n

Kingdom

Phylum

Class

Order

Family

Genus

Species

Kingdom Animalia

All animals are multicellular, mitochondrial heterotrophs—they have multiple cells with mitochondria and they rely on other organisms for their nourishment.

Most animals ingest their food and then digest it in some kind of internal cavity.

Animal Species

Somewhere around 9 or 10 million species of animals inhabit the earth.

About 800,000 species have been identified.

Animal Phyla

Biologists recognize about 36 separate phyla within the Kingdom Animalia.

Animal Phyla Web Page

Major Animal Phyla

Arthropoda87%

Mollusca5%

Chordata2%

Cnidaria1%

Platyhelminthes1%

Nematoda1%

Annelida1%

Porifera1%

Echinodermata1%

Other12%

Animal Movement

Most animals are capable of complex and relatively rapid movement compared to plants and other organisms.

Animal Reproduction

Most animals reproduce sexually, by means of differentiated haploid cells (eggs and sperm).

Most animals are diploid, meaning that the cells of adults contain two copies of the genetic material.

Animal Sizes

Animals range in size from no more than a few cells (like the mesozoans) to organisms weighing many tons (like the blue whale).

a mesozoan blue whale

Animal Habitats

Most animals inhabit the seas, with fewer in fresh water and even fewer on land.

Animal Cells

Animal cells, like all eukaryotic cells, have internal structures called organelles that serve specific functions for the cell.

Animal cells lack the rigid cell walls that characterize plant cells.

Animal Cell Diagram

Animal Bodies

The bodies of most animals (all except sponges) are made up of cells organized into tissues.

Each tissue is specialized to perform specific functions.

In most animals, tissues are organized into even more specialized organs.

Animal Symmetry

The most primitive animals are asymmetrical.

Cnidarians and echinoderms are radially symmetrical.

Most animals are bilaterally symmetrical.

Radial Symmetry

…applies to forms that can be divided into similar halves by more than two planes passing through it.

Animals with radial symmetry are usually sessile, free-floating, or weakly swimming.

Bilateral Symmetry

Animals with bilateral symmetery are most well-suited for directional movement.

Radial vs. Bilateral Symmetry

Cephalization

Bilateral Symmetry usually has led to cephalization—the process by which sensory organs and appendages became localized in the head end of animals.

Evolutionary Trends

If we analyze the basic body plans of animals, we find that they illustrate evolutionary trends.Four major “advances” (in order):

1. Multicellular body plan2. Bilaterally symmetrical body plan3. “Tube-within-a-tube” body plan4. Coelomate body plan

3 Major Bilateral Body Plans

1.Acoelomates2.Pseudocoelomates3.Coelomates

Each plan consists of 3 cell layers: endoderm, mesoderm, ectoderm

Acoelomates

These animals have no other cavity than the gut.

They are often called the “solid worms.”

PseudocoelomatesThese animals have a

body cavity (the pseudocoelom) which is not completely lined with mesoderm.

The “tube within a tube” body plan.

This category is also composed of mostly worms.

Coelomates

These animals have a “true coelom” lined with mesodermal peritoneum.

Most animals are coelomate.