Chapter 7 Chapter 7 Animal Classification, Animal Classification, Phylogeny, and Phylogeny, and organizationorganization

Ms. K. Cox, Zoology

Classification page 97Classification page 97

• A.We have identified about 1.4 million species on earth; three-fourths of these species are animals.– 1. Each species is given a genus and

species name according to the taxonomic system based on the work of Karl von Linnè.

– 2. The binomial (genus and species names) nomenclature is universal, and follows rules from the International Code of Zoological Nomenclature

• 3. Closely related species are placed in the same genus; closely related genera are placed in the same family, and so on.

• 4.Taxon is a general term used to represent a group of animals at any level of the classification scheme.

• B. To decide how closely related one taxon is to another, biologists compare the characters or traits present across groups. – 1.The traits used may be morphological- physcial

features (fur,no fur, brown eyes, green eyes, scales)– or– 2. molecular- DNA or genes that they have in

common– (exact genes they have in common, for example

Down Syndrome is caused by 2 copies of chromosome 21)

•C. Classification of organisms into higher level taxa has changed recently.

•1. A 5 kingdom scheme based on cellular properties and mode of nutrition was designed by Whittaker in1969: Monera, Protista, Plantae, Fungi, and Animalia. Bacteria were placed in the kingdom Monera

ChangesChanges

• 2. But new rRNA studies (rRNA changes very slowly, so it offers conserved characters for the phylogeny of ancient groups) indicate that bacteria is a polyphyletic group.

• 3. Bacteria now belong in two groups: Archaea and Eubacteria. These two groups replace the previous Kingdom Monera.

•4. Living things are commonyly grouped into a 3 domain, 6 kingdom system.

•(This is new) Domains: Archaea, Eubacteria, Eukarya

6 Kingdoms6 Kingdoms• 1. Plantae• 2. Animalia• 3. Protista• 4. Fungi• 5.

Archaebacteria • 6. Eubacteria

5 Kingdoms

1. Monera 2. Protista3. Plantae 4. Fungi 5. Animalia

Domains: Archaea, Eubacteria, Eukarya

• 5. The new taxonomy system.• Domain-3 groups• Kingdom-6 groups• Phylum• Class• Order• Family• Genus• Species

• D. Systematics is the arrangement of organisms based on evolutionary relationships indicated by shared characters.

• 1. The groups formed in modern systematics are designed to be monophyletic; polyphyletic groups are avoided.

• 2. Monophyletic groups include all organisms that have arisen from a single ancestral taxon;

• 3. polyphyletic groups are artificial groupings whose members have arisen from separate ancestors.

• E. There are 3 main schools of systematics that differ in their goals and approaches:

• 1. Evolutionary systematics is a traditional approach which looks for similar characters and homologies to group organisms into taxa.

• 2. Numerical taxonomy is based on a quantitative analysis of characters to determine taxa and does not attempt to distinguish between shared states due to common ancestry and shared states due to convergence.

• 3. Phylogenetic systematics (cladists) analyzes both symplesiomorphies (shared ancestral characters) and synapomorphies (shared derived characters) to determine cladograms.

Invertebrate or VertebrateInvertebrate or Vertebrate

What are Invertebrates?Invertebrates are a broad collection of animal groups (they do not belong to a single subphylum like the vertebrates) all of which lack a backbone. Some (not all) of the animal groups that are invertebrates include:-Sponges (Phylum Porifera)-Jellyfish, hydras, sea anemones, corals (Phylum Cnidaria)-Comb jellies (Phylum Ctenophora)-Flatworms (Phylum Platyhelminthes)-Molluscs (Phylum Mollusca)-Arthropods (Phylum Arthropoda)-Segmented worms (Phylum Annelida)-Echinoderms (Phylum Echinodermata)

VertebrateVertebrate

• bilateral symmetry• body segmentation• endoskeleton (bony or

cartilaginous) (they have a backbone)

• pharyngeal pouches (present during some stage of development)

• complete digestive system• ventral heart• closed blood system• tail (at some stage of

development)

The animal classes that are vertebrates include:

Jawless fish (Class Agnatha)Armored fish (Class Placodermi) - extinctCartilaginous fish (Class Chondrichthyes)Bony fish (Class Osteichthyes)Amphibians (Class Amphibia)Reptiles (Class Reptilia)Birds (Class Aves)Mammals (Class Mammalia)

F. Symmetry F. Symmetry

• 1. The basic body plans of animals may be analyzed to illustrate evolutionary trends. The first consideration is body symmetry:

• Animals may be asymmetrical, as in many protists and sponges; such animals lack complex sensory and locomotory functions.

2. 3 Types of Symmetry2. 3 Types of Symmetry

•A. asymmetry•B. bilateral symmetry

•C. radial symmetry

3. asymmetry3. asymmetry

•The arrangement of body parts without a central axis or point.

• (such animals lack complex sensory and

locomotory functions)

Illustration of difference Illustration of difference between symmetrical and between symmetrical and

asymmetrical.asymmetrical.

Tube SpongeTube Sponge(Callyspongia vaginalis)(Callyspongia vaginalis)

The Tube Sponge is one of the most common varieties of sea

sponge to be found on the reef. It is distinguished by its long tube-shaped growths, and ranges in

color from purple to blue, gray, and gray-green. Filtered water is

ejected through the large openings on the ends. This is one of the few

reef invertebrates that is blue in color.

SpongesSponges

4. bilateral 4. bilateral symmetrysymmetry

•The arrangement of body parts such that a single plane passing between the upper and lower surfaces and divides the animal into a right and left mirror image.(most things fall into this category)

HippopotamusHippopotamus

Hippos are herbivores and their diet consists mainly of grass and some water plants.  Hippos do most of

their eating during the night, while during the day hippos spend most

of their time basking in the sun on a sandbar or floating lazily in the

water with just their ears, eyes, and nostrils, and perhaps their back and top of the head, exposed.  The name

hippopotamus comes from the Greek "hippos," meaning horse.  Hippos were once called "river horses," even though

they are more closely related to pigs than horses.

Big male hippos can tip the scales at over three tons.

The Common DogThe Common Dog

5. radial symmetry5. radial symmetry•The arrangement of body parts such that any plane passing through the oral-aboral axis divided the animal into mirror images.

CnidarianCnidarian

Cnidarians are radially symmetrical. This means that their gastrovascular cavity,

tentacles, and mouth are aligned such that if you were to draw an imaginary line through the center

of their body, from the top of their tentacles through the base of their body, you could then turn the animal about that axis and it would look roughly the same at each angle in the turn. Another way to look at this is that cnidarians are cylindrical and have a top and bottom but

no left or right side.

Echinodermata (e.x. starfish)Echinodermata (e.x. starfish)

Sea stars or starfish are marine invertebrates belonging to phylum Echinodermata, class Asteroidea. The names sea star and starfish

are also used for the closely related brittle stars, which make up the class Ophiuroidea. They

exhibit a superficially radial symmetry, typically with five or more "arms" which radiate from

an indistinct disk (pentaradial symmetry). In fact, their

evolutionary ancestors are believed to have had bilateral

symmetry, and sea stars do have some remnant of this body

structure.

Stopped here on Friday Feb Stopped here on Friday Feb 1111

•1. The second consideration is the level of cellular organization:–A. The single celled organisms, or those formed from aggregates of single cells, exhibit the cytoplasmic level of organization; these cells have very little interdependence and do not form tissues.

G. Unicellular Level of Organization page 105

– Diploblastic Organization.

• These organisms, like the cnidarians, have two tissues layers formed from the embryonic ectoderm and endoderm. The cell layers are interdependent. – Triploblastic Organization.

• These organisms have 3 tissue layers derived from the embryonic ectoderm, mesoderm, and endoderm.

Body CavityBody Cavity• 1.The third consideration is the presence of

a body cavity (not the gut cavity, but a cavity external to the gut):

• 2.The body cavity Functions• A. provide more room for organ

development• B. Provide more surface area for diffusion• C. provide an area for storage• D. often act as hydrostatic skeletons• E. provide a vehicle for eliminating wastes

and for reproduction• F. Facilitate increased body size.

Possibilities in the Triploblastic Possibilities in the Triploblastic OrganizationOrganization

• 1. Triploblastic Acoelomate Pattern• A. see page 106, Figure 7.11 A. Draw this

example in your notes.• B. Description: thin ectoderm, thick

mesoderm, and thin endoderm, with small opening in the middle called a gut. The mesoderm touches the endoderm.

• C. Examples of flat worms, tapeworm. (chapter 10)

-Continued- Possibilities in the -Continued- Possibilities in the Triploblastic OrganizationTriploblastic Organization

• 2. Triploblastic Pseudocoelomate Pattern• A. see page 106, Figure 7.11 B. Draw this

example in your notes.• B. Description: thin ectoderm, thin

mesoderm, thin endoderm, as an extra space between the Mesoderm and the Endoderm called the Pseudocoelom.

• C. Examples: roundworm, filarial worm- causes elephantiasis see page 174 (chapter 11)

– –Continued- Possibilities in the Continued- Possibilities in the Triploblastic OrganizationTriploblastic Organization

• 3. Triploblastic Coelomate Pattern• A. See page 106, Figure 7.11 C. Draw this

example in your notes.• B. Description: Thin Ectoderm, thicker mesoderm

that has space to the left and the right. The mesoderm butts up directly to the Endoderm. In the center there is a small opening.

• C. Example: Nemertea (ribbon worms)

• ,

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Higher Animal TaxonomyHigher Animal Taxonomy

• 1. Animalia are considered monophyletic. Due to cellular organization.

• 2. “The Cambrian Explosion”- about 0.6 billion years ago an evolutionary explosion occurred which resulted in the origin of all modern phyla. (phyla= many groups)

• 3. Three main groups or braches in the animal kingdom.– A. Mesozoa– B. Parazoa (sponges)

ContinuedContinued

• C. Eumetazoa- divided into further groups based on body symmetry.– 1. Radiata– 2. Bilateria

– A. Protostomia –(Platyhelminthes, Nematoda, Mollusca, Annelida, Arthropoda)

»1. Trochophore larva see page 108 figure 7.12 D. draw an example in your notes.

– B. Deuterostomia-(Echinodermata, hemichordata, chordata)

»1. Dipleurula larva see page 108 figure 7.12 H. Draw an example in your notes.

ContinuedContinued

• 4. Scientists use Comparative embryology. (Definition: the observation that embryological events may be similar because of shared ancestry.)