Kingdom Animalia

Zoology: The Study of Animals

Characteristics of the Animals

1. Animals are multicellular ………………..

Except for sponges, animal cells are arranged into tissues (a tissue is a group of cells alike in structure and function… such as muscle tissue or brain tissue). Tissues are necessary to produce organs and organ systems.

2. Animals are eukaryotic, heterotrophs

Heterotrophs consume their organic food. Heterotrophs are not capable of making their own foods.

3. Animals are motile

Heterotrophy often requires motility to acquire food. Animals have motility during at least some part of their life cycle.

Motility is accomplished by a coordinated effort of muscles and nerve cells.

4. Animal cells lack cell walls

Therefore a skeleton is necessary to support the tissues of large animals.

5. Animals have a period of embryonic development

•

During embryonic development, cells “Differentiate” and become specialized leading to the “Division of Labor”.

Types of Animals

Animals are classified into 2 general groups 1.Invertebrates – animals which lack a backbone or vertebral column… currently grouped into 33 phyla.

2.Vertebrates - animals with a backbone or vertebral column… all are found in Phylum Chordata

Members of the Phylum Chordata have 4 general characteristics

1. A Dorsal, Hollow Nerve Cord

•

A dorsal hollow nerve cord forms the basis of the nervous system. In some chordates, the nerve cord becomes the brain and spinal cord.

2. A Notochord

A notochord is a flexible cord located on the dorsal surface. In most cases, the notochord is replaced by bone during development. Notochord

3. A Muscular Tail

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A muscular tail extends beyond the digestive system. In many chordates, such as humans, the tail is lost during embryonic development.

4. Pharyngeal Gill Slits (pouches)

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Pharyngeal Gill Slits provides channels across the pharynx to the outside of the body. In some chordates, the slits become gills for oxygen exchange, or for filter feeding, while in others, the slits disappear during embryonic development.

Evolutionary Trends Simple organisms Complex Organisms An increase in “Cell Specialization” and “Division of Labor” Classification of the Kingdom Animalia Protozoans Asymmetry * No Body Plan Radial Symmetry

•

Body Radiates from a Central Point Protostomes

•

Mouth forms at the Blastopore Deuterostomes

•

Anus forms at the Blastopore Radial Symmetry Bilateral Symmetry 1. Phylum Porifera (Sponges) 2. Phylum Cnidaria (Jellyfish, Sea Anemone) Phyla 1-9 are Invertebrates “Animals without backbones” Acoelomates Bilateral Symmetry Body Plan Includes Anterior and Posterior Ends Dorsal and Ventral Surfaces “Right” and “Left” sides are mirror images Coelomates Coelomates 9. Phylum Echinodermata 10. Phylum Chordata (Starfish, Sea Urchins) *Class Ichthyes *Class Amphibia *Class Reptilia *Class Aves *Class Mammalia Pseudocoelomates Coelomates 6. Phylum Annelida 3. Phylum Platyhelminthes (Flatworms) 4. Phylum Nematoda (Roundworms) (Segmented Worms) 7. Phylum Mollusca Coelom: body cavity found between two layers of mesoderm.

5. Phylum Rotifera (Rotifers) (Snails, Clams) 8. Phylum Arthropoda (Insects, Spiders)

Animal Diversity

The key to the success of the Animal Kingdom ** Diversity is defined as the presence of a wide range of variations.

The Diversity of the Animals originates from the variations that occur in their:

• 1. Tissue Complexity • 2. Body Symmetry • 3. Cephalization • 4. GastroVascular Cavity (GVC) • 5. Coelom • 6. Segmentation, and • 7. Protostomes and Deuterostomes.

1. Tissue Complexity

Eumetazoans are animals that are composed of several types of have closely functioning tissues. Parazoans (sponges) are animals that are not organized into true tissues and lack organs.

Embryonic Germ Layers

Tissues that become established during early embryonic development are called “germ layers”.

The three “ germ layers” ectoderm , mesoderm and are the endoderm .

Some organisms are diploblastic , their embryos have two cell layers… hydra and jellyfish….. they lack mesoderm. Some organisms are triploblastic , their embryos have three cell layers…the ectoderm , mesoderm and endoderm

Embryonic Germ Layers

A blastula is a hollow sphere of cells, surrounding an inner fluid-filled cavity called the blastocoele.

Gastrulation occurs when a blastula folds inward and enlarges to create a gastrula.

Embryonic Germ Layers

The

ectoderm

forms from the outer layer of cells. It gives rise to the skin and nervous system.

The

endoderm

made of cells that form the tube-like structure in the gastrula. These cells will form the lining of the digestive system and the majority of the respiratory system.

The

Mesoderm

forms between the ectoderm and endoderm. It becomes the muscles, connective tissues, skeleton, kidneys, circulatory and reproductive organs.

2. Body Symmetry

Body Shapes

Asymmetry

•

Asymmetrical

animals have no pattern of symmetry. The simplest animals (sponges) are asymmetrical.

Radial Symmetry

The body parts of a radially symmetrical animal are arranged around a central axis so that each part radiates from the center.

Animals that exhibit radial symmetry tend to be sessile (immobile). Radial symmetry allows them to reach out in all directions.

Bilateral Symmetry

Only one cut along the longitudinal axis will produce identical halves of a bilaterally symmetrical animal. Bilateral symmetry is best for motile animals.

• • •

Body Plan Includes Anterior and Posterior Ends Dorsal and Ventral Surfaces “Right” and “Left” sides are mirror images

Evolution of Symmetry

Larval stage only The evolutionary sequence progressed from asymmetrical animals to radial and then to bilaterally symmetrical animals.

3. Cephalization

The term “Cephalo” means “head”.

As animals with bilateral symmetry evolved, there was a greater increase in nerve tissue (brain cells) concentrated in the anterior end (the head)….this is called “cephalization”. As brains formed, accessory organs for seeing, hearing, tasting, also formed.

4. Gastrovascular Cavity (GVC)

G

astro

V

ascular

C

avities (GVC) are areas where food is digested. If an animal has only one digestive opening, processing food is limited….like in a jellyfish, or flatworm Animals with two digestive openings, a designated

digestive tract,

digest food more thoroughly and can exact more energy.

Gastrovascular cavity

5. The Coelom: Body Cavity

The coelom is a body cavity which is lined with mesoderm.

The cavity also enables the internal organs to grow and move independently of the outer body wall….. If it were not for your coelom every beat of your heart would ripple throughout your entire body.

Arrangement of Ectoderm, Mesoderm, and Endoderm

An

acoelomate

animal does not have a body cavity.

Digestive cavity (Gut)

Flatworms: Tapeworms

A

pseudocoelomate

animal has a body cavity (called a

pseudocoelom

) located between endoderm and mesoderm.

Digestive cavity (Gut)

pseudocoelom

Roundworms

The body cavity of a

coelomate

animal (called a

coelom

) is located within the mesoderm.

The mesentery is a membrane that holds the gut in place.

Coelom Digestive cavity (Gut) Mesoderm

Earthworms and You

6. Segmentation

Many animals have segmented body parts. In some cases the parts repeat over and over again, as with earthworms.

An Earthworm segmentation In other animals, the segments are modified, such as with insects… insects essentially have 3 segments…. the head, thorax and abdomen.

7. Body Plans:

Protostomes and Deuterostomes

Embryonic Development

•

During early development, the fertilized egg divides, or cleaves , to produce a solid ball of cells.

Embryonic Development

Next, some of the cells of the blastula migrate inward producing a

gastrula

.

The opening is called the

blastopore

. The internal cavity is called the

archenteron

.

Archenteron Gastrulation: The Development of Germ Layers Archenteron Blastopore Blastopore ( Blastopore becomes the mouth) ( Blastopore becomes the anus)

Summary of Evolutionary Trends

Symmetry Asymmetry Radial Bilateral GVC No GVC Saclike GVC Complete GVC Coelom Acoelomate Pseudocoelomate Coelomate Embryonic Germ Layers None 2, (tissues, no organs) 3, (tissues and organs)

Phylum (common name) Porifera (sponges) Cnidaria (jellyfish, hydra) Platyhelminthes (flatworms) Nematoda (roundworms) Rotifera (rotifers) Mollusca (clams, snails) Annelida (earthworms) Arthropoda (insects, spiders) Evolutionary Trends Tissue Complexity Germ Layers Body Symmetry Gut Openings parazoa

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asymmetry 0 eumetazoa 2 Radial symmetry 1 eumetazoa 3 1 eumetazoa 3 Bilateral Symmetry Bilateral Symmetry 2 eumetazoa 3 2 eumetazoa 3 Bilateral Symmetry Bilateral Symmetry 2 eumetazoa 3 Bilateral Symmetry 2 eumetazoa 3 2 Echinodermata (starfish, sea urchins) eumetazoa 3 Bilateral Symmetry Radial Symmetry 2 Chordata eumetazoa 3 Bilateral Symmetry 2 Coelom -

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Embryonic Development acoelomate

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pseudo coelomate pseudo coelomate coelomate

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protostome coelomate protostome coelomate protostome coelomate deuterostome coelomate deuterostome

Kingdom Animalia Survey

1. Phylum Porifera

(Sponges)

(exit for water)

Phylum Porifera

(Sponges) (digest and distribute food) (skeleton) Choanaocyte *** Sponges are Parazoans: they contain NO true tissues *** Sponges are filter feeders

2. Phylum Cnidaria

Jellyfish, Corals, and other Stingers

General Characteristics

• Simple body plan…. “bag-shaped” organism • Radially symmetrical • Consists of a mouth and a sac-like cavity, no anus • The mouth is surrounded by a ring of tentacles • The cavity in its center is its

gastrovascular cavity

.

Two Body Forms

Polyps - sessile - ex: sea anemones - mouth points up Medusa - free floating - ex: jellyfish - mouth points down

3. Phylum Platyhelminthes

(Flatworms)

•

Platyhelminthes consists of three kinds of acoelomate flatworms.

• 1.

Free-living Flatworms:

such as planarians, which are carnivorous scavengers.

• 2.

Flukes:

are internal, or external, parasites that suck tissue fluids or blood.

• 3.

Tapeworms

: internal parasites that live in the intestinal tracts of vertebrates.

Planaria

Tapeworm

Scolex (head) Old Proglottids Young Proglottids ** tapeworms appear to be segmented, but they are not true “segmented” worms

4. Phylum Nematoda

(Roundworms) * Mostly found in fresh water, marine, moist soil.

* A complete digestive tract.

•

* Free-living forms are important in decomposition Animal parasitic forms can be hazardous to health.

(Trichinella spiralis in humans via undercooked infected pork)

Nematoda

5. Phylum Rotifera

(Rotifers)

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Rotifers are small organisms found in damp soil.

•

Complete digestive system is present.

Rotifer

6. Phylum Mollusca

(snails, bivalves (such as clams….have a shell which has two parts) , octopuses and squids)

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In Squids, the shell is reduced and is internal.

•

In octopuses, the shell is entirely absent.

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Octopuses have a highly developed nervous system with a large, complex brain.

Snails

7. Phylum Annelid

(Segmented Worms: includes leeches, earthworms and polychaetes) Leeches are freshwater. Many are carnivorous and feed on small invertebrates, while some attach temporarily to animals to feed on blood. Earthworms ingest soil, extract nutrients in the digestive system and deposit undigested material through the anus. Polychaetae drift and swim in the plankton, some crawl along the sea floor, and many live in tubes they construct by mixing sand and shell bits with mucus.

Tube-dwellers include the fanworms that feed by trapping suspended food particles in their feathery filters which are extended from the tubes.

Phylum Annelid

(Segmented Worms: includes leeches, earthworms and polychaetes) Polychaete Worm Fanworm

Open vs. Closed Blood Systems

Annelids are considered to be very advanced in the animal kingdom…. A closed blood system is one of the reasons why.

8. Phylum Arthropoda

( spiders, insects, crustaceans, and various related organisms)

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Arthropods have two kinds of life cycles…(1) complete metamorphosis , (2) incomplete metamorphosis .

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Arthropods have: * jointed appendages, * a well-developed nervous system, * specialized body segments , and * an exoskeleton made of chiton .

** Phylum Arthropoda is the largest and most complex Phylum

The specialized body segments are the: Head, Thorax and Abdomen

Arthropods must shed their exoskeletons in order to grow…. The process is called molting .

Emerging Insect Discarded Exoskeleton

Incomplete Metamorphosis (changing forms) (immature forms are often called nymphs) Nymphs resemble the adult in form except for being smaller and lacking fully developed wings and sexual organs. Life Cycle: Egg nymph adult

Complete metamorphosis Immature forms are called larvae (larva, singular). The pupal stage is a transition stage, when the larva is transformed to the adult. Pupa molts to the adult form. Life Cycle: Egg --> larva --> pupa --> adult

9. Phylum Echinodermata

(sea stars (starfish), sea urchins and sand dollars) Echinoderms are Coelomates, Deuterostomes Echinoderms have complete digestive systems Although some adults exhibit radial symmetry, some features are bilateral, as are the body shapes of their larvae.

10. Phylum Chordata

The Phylum Chordata consists of animals that exhibit the following four features .

In many cases, these features are temporary , appearing only during embryonic development.