Classification of Animals

Characteristics Common To All Animals -

Animal Innovations Tissue Layers - Symmetry - Body Cavities - Developmental Patterns -

Animal Classification Parazoa -Eumetazoans

Cnidarians - Ctenophores -

Protostomes Platyhelminthes - Rotifera - Nemertea - Mollusca - Annelida - Nemotoda - Arthropoda -

Deuterostomes Echinodermata -Phyum Chordata

Characteristics - Invertebrate Chordates -Vertebrate Chordates

Agnathans -Jawed Fishes -

Amphibians - Amniotes -

Unit IIIAnatomy and Physiology of

AnimalsLearning Goal 1

Identify the major classification schemes of the kingdom Animalia

Characteristics Common to Animals

Multicellular

Eukaryotic

No cell walls

Heterotrophic

Generally motile

Animal Innovations

• Tissues and Tissue LayersAs embryos of most animals develop they form cell layers.The inner layer called the endoderm becomes the lining of the gut and other organs,The outer ectoderm forms the external covering and nervous system.Between is the mesoderm which becomes the muscles and other structures between the gut and the external covering.

• Radial or Bilateral Symmetry

Animals that exhibit radial symmetry have body parts arranged around a central axis.

This includes two phyla, Cnidaria ( hydras, jellyfishes, and sea anemones) and Ctenophora (comb jellies)

All other animal phyla have bilateral symmetry in which a cut along the midline from head to tail would divide them into mirror images.

• Body CavitiesAcoelomate – animals without a body cavity. Have a continuous mass of tissue between the gut and the body wall. Includes phylum Platyhelmenthes (flatworms).Pseudocoelomate- animals with a fluid or organ filled space between the gut and the body wall. Includes phyla Nemotoda (round worms) and Rotifera.Coelomates – animals with a true coelom, a fluid-filled body cavity lined by a peritoneum.

• Developmental PatternsProtostomesIncludes most invertebrate phyla.As the zygote (fertilized egg) divides by mitosis it exhibits a pattern of spiral cleavage.Cleavage is determinate, meaning that each cell’s development is determined as the cell is produced. In other words it won’t develop on its own.

• DeuterstomesIncludes some invertebrates and all vertebrate phyla.Embryos exhibit radial cleavage.Early cells of the embryo have indeterminate cleavage where an isolated cell can develop into a functional embryo

Animal Classification• Parazoa

Includes only one group, the sponges.Phylum PoriferaLack true tissues with simple body plans.Filters food particles from surrounding water in a central chamber.Most are hermaphroditic with individuals producing both sperm and eggs.Zygotes develop into flagellated larvae that attach to substrates becoming sessile adults.

Eumetazoans• Cnidarians

8900 species, nearly all of which live in the sea.Exhibit radial symmetry with a body plan organized around a saclike gastrovascular cavity.The mouth is ringed with tentacles for food gathering.May exhibit a polyp or a medusa body structure or alternate between both.Major groups include the hydrozoa (hydra), Scyphozoa (jelly fishes), Cubozoa (box jelly fish), and Anthozoa (corals and sea anemones).All have nematocysts which are encapsulated coiled threads containing toxins that can paralyze small prey.

• Ctenophores (comb jellies)

Exhibit radial symmetry.

Lack nematocysts.

Usually transparent and sometimes luminescent.

Live primarily in coastal regions.

Protostomes

• Phylum Platyhelminthes (flatworms)

13,000 species live in aquatic or moist terrestrial environments.

They are acoelomate with no respiratory or circulatory system.

Includes turbellarians, trematodes (flukes), monogenoids, and cestodes (tape worms)

• Phylum Rotifera

Microscopic, freshwater organisms.

Well-developed digestive, reproductive, excretory, and nervous systems.

They are pseudocoelomates.

Have a wheel-like corona lined with cilia to help them move and eat.

• Phylum Nemertea

Also known as ribbon worms.

Mostly marine species from 1cm to 30 meters in length.

Have complete digestive and circulatory systems, with a mucous covered proboscis to catch prey.

• Phylum MolluscaContain a visceral mass enclosed in a shell with a muscular head-foot for locomotion.Have a true coelom.Mostly marine, but some freshwater,and terrestrial.Contain the groups polyplacophora (chitons), gastropods (snails and slugs), bivalves ( clams, mussels), and cephalopods (octopuses, squids, and nautiluses)

• Phylum AnnelidaHabitats are marine, freshwater, and terrestrial.Highly segmented body divided into repeating units.Digestive and circulatory systems run the length of the body.Contain groups, polychaeta (bristle worms), oligochaeta (earthworms), and hirudinea (leeches)

• Phylum Nematoda (roundworms)80,000 described species, but estimated that more than half a million exist.Many are microscopic, but can be a meter or more long.Have ecological, agricultural, and medical significance. Major decomposers, can be parasitic on crop plants and people.

• Phylum ArthropodaHave segmented bodies with as rigid exoskeleton.Body segments consist of the head, thorax, and abdomen.Consist of subphyla chelicerata (spiders, ticks, mites, and scorpions), crustacea (shrimp, lobster, crab), myriapoda (centipedes, and millipedes), and hexapoda (insects)

Deuterostomes

• Phylum Echinodermata

6600 species of sea stars, sea urchins and others.

Have a well-developed coelom.

Exhibit radial symmetry as adults, with no head or central brain.

Phylum Chordata

Characteristics

Have a notochord, a flexible rod consisting of fluid-filled cells surrounded by tough connective tissue.

Have a segmental body wall and tail muscles.

Contain a dorsal hollow nerve chord with a brain-like structure at the anterior end.

Have a perforated pharynx at some stage of development.

Invertebrate Chordates

• Subphylum Urochordata (tunacates or sea squirts)Water pulled in through an incurrent siphon with a mucous net to trap particulate food.

• Subphylum Cephalochordata (lancelets)Have sense organs on tentacles that grow from an oral hood. Occupy shallow marine habitats.

Vertebrate Chordates

• Agnathans (Jawless Fishes)Phyla Myxinoidea (hagfishes) and Peteroyzontoidea (lampreys).Lack jaws, and have skeletons conposed of cartilage.Hagfishes are scavengers in marine environments and most lampreys are parasites as adults.

Jawed Fishes

ChondrichthyesSkates, rays, and sharksHave cartilagenous skeletonsUse electroreceptors to detect weak electric currents produced by other animals.

Bony Fishes

• Fishes with bony endoskeletons.Have a gas-filled swim bladder to increase buoyancy.

• ActinopterygiiMost primative are sturgeons and paddlefishesTeleosts are the most diverse and successful group of bony fishes.

• Sarcopterygii (lobe-finned and lungfish)

Amphibians

• Carnivorous as adults, but aquatic larvae may be herbivores.

• Have thin, scaleless skin that must remain moist to help with gas exchange.

• Many have life cycles that consist of both larval and adult stages.

• Three major groups:Anura (frogs and toads)Urodela (salamanders)Gymnophiona (caecelian)

Amniotes

• CharacteristicsTough dry skin filled with keratin and lipids.Reptiles and birds produce an amniotic egg able to survive on dry land. Consists of a shell, four membranes for gas exchange, a yolk and albumin for nutrients and water.Mammal embryos have the same four membranes, but no shell and implant in the wall of the female’s uterus to obtain nutrients and oxygen.

Testudines: Turtles

• Have the characteristic bony shell consisting or a dorsal carapace and a ventral plastron.

• Ribs are fused to the inside of the carapace

• Live in terrestrial, freshwater, and marine habitats.

• No teeth, but have a keratinized beak.

• Sphenodontids (tuatara)Only two surviving species that live on islands off New Zealand’s coast.

• Squamata (lizards and snakes)Skin of keratinized scales that sheds as animal grows.Regulate body temperature behaviorally.

• Crocodilians

Aquatic predators on other vertebrates.

Have a four-chambered heart and care for their young more like birds than other reptiles.

Aves: Birds

• Have light weight, strong skeletons with hollow limb bones.

• Possess a keeled sternum (breastbone) to which flight muscles attach.

• Have feathers which provide aide in flight and form an insulating cover.

• Have a high rate of metabolism and maintain a high constant body temperature.

Mammals

• Four Key AdaptationsHigh metabolic rate and body temperature.Specialized teeth and jaws.High degree of parental care.Larger more complex brains.

• Mammal Groups:Monotremes (egg layers)Marsupials (pouched mammals)Placentals (young develop in a placenta)

LG 1 Terms

1. Ectoderm –

2. Mesoderm –

3. Endoderm -

4. Radial vs Bilateral Symmetry –

5. Coelomate –

6. Acoelomate –

7. Pseudocoelomate –

8. Notochord –

9. Protostome –

10. Deuterostome –