Chapter 2: A Survey of the Animal Kingdom

Homeotic Genes

• Genes that control the early development in animals

• Homeobox or Hox genes - define the head to tail pattern of development in animal embryos.

Bilateral symmetry

• The term ____ is obtained from Latin ‘bis’ meaning ‘two’ and ‘latus’ meaning side.

• However, the word ‘____’ came from Greek ‘syn’ means ‘together’ and ‘metron’ means ‘meter’.

• 99% of animals (belonging to phyla: Chordata, Annelida, Arthropoda, Platyzoa, Nematoda, and most Mollusca) and humans exhibit ____.

Radial Symmetry

is a body shape where parts radiate outward from a central point. This means that if you cut the animal in half through the center from any direction, the two halves will be identical.

Insects

• Most abundant and diverse animals on earth.

• They comprise 75% of all arthropods.

• One of the most successful animals on earth

Parazoans

• near animals

• Animals that do not have tissues and organs, have cellular level organization, and lack symmetry.

• There is only one phylum in the animal kingdom classified under this category, the sponges.

Metazoans

• True animals

• Animals that have tissues and organs truly organized into organ systems and have a definite shape and symmetry (bilateral).

• Include birds, fish, amphibians, reptiles and mammals, etc

Phyla

Animals have been traditionally classified into

• There are more or less 36 ___ (27 minor & 9 major) of the animal kingdom.

• is defined by structural and functional characteristics that are different from every other animal group.

Minor Phyla

• phylum Loricefera, discovered in 1983

• Cycliophora, discovered in 1995

• Microagnathozoa, discovered in Greenland in 2000.

Major Phylum

• Porifera

• Cnidaria

• Platyhelminthes

• Nematoda

• Mollusca

• Annelida

• Arhropoda

• Echinodermata

• Chordata

Phylum

• is a level of classification or taxonomic rank below kingdom and above class

• are organized from the least evolved (porifera) to the most evolved (chordata)

Acoelomate and Coelomate

Most animals can be classified as either ___ (without cavity) or ___ (with cavity).

Phylum Porifera (Poriferans/Pori-pore bearing)

• This group of animals is considered the most primitive on earth, since they exhibit features that are more related to the early multicellular organisms.

• Sponges are said to be the oldest animals on earth.

• They lack neurons and muscles since their body is composed of cells only.

• They are immobile and most often attached to the substrate or rock.

• Types of cells in sponges: Pinacocytes, Choanocytes, Amoebocytes

• Three groups of sponges: Calcarea, Demospongia, Hexactinellida

Phylum Cnidaria

• Unlike sponges, ____ can move, as seen in jellyfish, sea anemones, and the polyps of hard corals.

• Two forms: Medusa and polyp

• Groups: Anthozoa, Hydrozoa, Scyphozoa, Cubozoa

Phylum Platyhelminthes

• These animals have similar free-swimming ciliated larvae called a trochophore and a feeding structure made of hollow tentacles called lophophore; hence, these two groups fall under lophotrochozoa.

• Flatworms are dorso-ventrally flattened, bilateral animals with a solid body and an incomplete digestive system. They do not have circulatory and respiratory systems; hence, their body must always be moist to allow gas exchange.

• Three classes of flatworms: Turbellaria, Tremadota, Cestoda

Phylum Nematoda (Nematodes)

• also called roundworms, are the most abundant and diverse of all the worms. There are about 15,000 species that vary in size, from less than a millimeter to over 10 meters in length.

• They do not have respiratory and circulatory system.

• They have a complete digestive system that includes a mouth, pharynx, intestine, and anus.

• Group: Pinworms, Ascaris, Hookworms, Guinea worms

Acoelomate Animals

Phylum Porifera, Cnidaria, Platyhelminthes, Nematoda

Phylum Mollusca (Mollusks)

• Unlike flatworms, ____ and other bilateral animals have a complete digestive tract.

• They have two openings: the mouth and the anus, found on opposite ends.

• This group is comprises different-looking members (i.e., oyster, squid, and octopus).

• Classes: Gastropoda, Pelecypoda, Cephalopoda, Scaphopoda, Polyplacophora, Aplacophora

Phylum Annelida

• Members of this phylum show a lot of similarity with each other, unlike the mollusks that are very different in forms.

• They are all segmented. Each segment contains part of the digestive tract, nerve cord, and blood vessels that carry blood to all parts of the body.

• Classes: Polychaeta, Oligochaeta, Hirudinae

Phylum Arthropoda (Arthropods)

• are the most diverse and abundant of all the animals on earth.

• They can be found almost anywhere.

• are covered by a chitinous exoskeleton that protects and supports the tissues. Their joint-appendages became very important adaptation during their evolution.

• Groups: Trilobites, Crusctaceans, Chelicerates, Insects, Myriapods

Phylum Echinodermata (Echinoderms)

• Adult ___ are usually slow-moving and with radial type of symmetry.

• They are known for their internal skeleton made up of interlocking calcium-based plates called ossicles.

• Their skin contains calcareous ossicles and spines

• They are exclusively marine.

• They move slowly by concerted action of numerous suctorial tube feet.

• They have no proper circulatory system.

• Five groups: Asteriacea, Echinoidea, Ophioroidea, Crinoidea, Holothoroidea

Phylum Chordata

• This phylum is composed of three groups.

• One group includes all the animals with backbones or vertebrates. The other two groups are tunicates and lancelets; they are sometimes called invertebrates since they do not have vertebral column. They have notochord for support.

• Three Groups: Urochordata (Tunicata), Cephalochordata (Acraniata), Vertebrata (Craniata)

Vertebrates

• comprise only around 5% of all animals on earth.

• possess an endoskeleton.

• The endoskeleton is made up of bones or cartilage. It can be divided into distinct parts, such as the braincase, vertebrae, bones, and gill arches.

• Classes: Agnatha, Chondricthyes, Oesteichytes, Amphibia, Reptilia, Aves, Mammalia

Coelomate Animals

Phylum Mollusca, Annelida, Arthropoda, Echinodermata, and Chordata

Porifera

Sponges are example of ___

Cnidaria

Jellyfish, Corals, and Sea Anemonemes are examples of ___

Nematoda

Roundworms are example of

Mollusca

Snails, clams, and octopuses are example of

Annelida

Earthworms and leeches are example of

Arthropoda

Insects, Arachnids, and Crustaceans are example of

Echinodermata

Starfish and sea urchins are example of

Chordata

Mammals, Birds, Amphibians, Reptiles, Fish are example