9 Animals Invertebrates.pdf

Biology 2201Unit 2 – Section 2Kingdom Animalia -invertebratesP 182

Kingdom AnimaliaZoology: the study of animalsAnimals are:a) Multicellular and Eukaryotic.b) Heterotrophs– (since they consume organic materials anddigest it).c) Mostly motile, though some are attached to asubstrate (sessile).d) Organisms which often have specialized tissue tobe used for specific functions (muscle tissue,nerve tissue, etc).e) Capable of asexual reproduction in lower formsand sexual reproduction in higher forms.

The Divisions of Kingdom AnimaliaKingdomAnimaliaInvertebrates: Animals “without” abackbone/spinal column.InvertebratesVertebratesVertebrates: Animals “With” abackbone or spinal column.

The Invertebrates

The Invertebrates (p 183-184)Invertebrates• Phylum Porifera – Sponges (Sponge Bob!)Phylum PoriferaPhylum CnidariaPhylum PlatyhelminthesPhylum NematodaPhylum AnnelidaPhylum MolluscaPhylum ArthropodaPhylum Echinodermata• Phylum Cnidaria – jellyfish, hydra, corals• Phylum Platyhelminthes – Flat worms (Tapeworms,planaria, blood flukes)• Phylum Nematoda – Round worms ( Hookworms,pinworms)• Phylum Annelida – Segmented worms (Earthworms,leeches)• Phylum Mollusca – Soft bodied animals (Clams, squids,snails)• Phylum Arthropoda – Jointed appendages (Insects,spiders, lobsters)• Phylum Echinodermata – Spiny skinned animals(starfish, sea urchin, sand dollar)

Characteristics of Various Animal Phyla : (p 182 )The following characteristics of animals will be examined to determinedevelopmental trends.1. Body organization (cells organized into tissues, organs and organ systems)2. Number of germ layers (tissues from which more specialized tissues develop)3. Body symmetry4. A complete or incomplete digestive tract5. Development (or not) of an internal cavity called a coelom

1. Germ Layers– Germ layers refer to the layers of cells anorganism has during its embryonicdevelopment.• The germ layers are:a. Ectoderm – The outer layer of cells – givesrise to skin and nervous system.b. Mesoderm – The middle layer of cells –gives rise to the circulatory, skeletal andreproductive systems.c. Endoderm – The inner layer of cells. givesrise to digestive tract.Note: ALL ANIMALS EXCEPT Porifera and Cnidaria have3 germ layers. Porifera and Cnidarians haveTWO(2) germ layers.

Embryonic Germ Layers

2. Digestive Tract/SystemThe digestive tract is the structurethrough which organisms bring infood and removes waste.a. One or two openings (i.e. mouthand anus)b. One way or two way movement(does food/waste move in twodirections versus moving only inone direction)1. One Opening – Two Ways - Anincomplete digestive system2. Two Openings – One Way - A CompleteDigestive SystemBiology 2201

3. Body Symmetry p 185Body symmetry refers to the basic body plan/shape ofan organism. Symmetry is most closely related to theorientation of the organism in space etc and whetheror not it can move.Kinds of symmetry:1. Asymmetrical:– lack symmetry, cannot be cut into two matchinghalves• (eg.) most sponges2. Radial symmetry:– division into equal halves by passing a planethrough the central axis of the animal in anydirection• (eg.) starfish, jellyfish3. Bilateral symmetry:– division into equal halves only along a singleplane. Each half is a mirror image of the other• (eg.) most animals, humans (not perfect)

Terms Associated with Bilateral Symmetry1. Dorsal• Term meaning the “back” of an organism.2. Ventral• Term meaning the “belly” or “underside” of an organism.3. Posterior• Term meaning toward the “tail” of an organism.4. Anterior• Term meaning toward the “head” of an organism.

• Note:Animals with bilateral symmetry have atrue head. This head region mostalways shows cephalization whichrefers to a concentration of nervetissues and receptors at the anterior(head region) end of the animals body.

4. Coelom p.185• A Coelom is a fluid filled “Body Cavity”surrounded by a mesoderm ( a layer of cellsthat line the body cavity and gut) p 186.• Found in some invertebrates and allvertibratesA. Coelomates - animals having a coelomB. Pseudocoelomates – partial coelmC. Acoelomates - animals without a coelomQ. What is the advantage of having a coelom?• Provides space in which internal organs aresuspended so they are not negatively affected bymuscle pressures.• Provides space for internal organs to develop andexpand.• Contains fluids that assist in maintaining structureand provides mechanism of internal transport andgas exchange.

• The development of a body cavity demonstrates complexity andevolutionary development in animals.• The simplest animals have a single opening that acts as a mouthand anus.• Complex animals have a gut with two openings, a mouth andanus.

5. Reproduction• Refers to the mechanism by which an organism passes on geneticmaterial so as to continue the species.a. Method of Fertilization• Internal Fertilization – fertilization inside the organism.• External Fertilization – fertilization outside the organismb. Type of Reproduction• Sexual ( 2 sets of DNA)• Asexual (1 set of DNA)c. Presence of Sex organs/Sexes• Separate Sexes (male and female)• Hermaphrodites (possessing both male and female sex organs)Biology 2201

Invertebrate Developmental Trends:1. Simple to complex as organisms evolve.2. Simplest have asymmetry, more complex are often radial and most complexhave bilateral symmetry.3. Organisms (from simplest to complex) go from having no cavity, to a falsecavity, to a true body cavity.4. Simple organisms may reproduce sexually and asexually. More complexanimals use only sexual reproduction.5. Simple animals have only two tissue layers (germ layers), complex animalshave three tissue layers.6. Simple tend to be non-motile while more complex animals tend to bemotile (they move around).7. Simple animals have no tissue, more complex animals have tissues (whichcan be specialized) and form systems.Note: Many invertebrates are hermaphrodites (both male and female parts) butrarely can they self-fertilize.

Arthropods:The Most Successful Class of Animal1. Rigid, jointed external skeleton(exoskeleton for protection).2. Well-defined head with jointedappendages.3. Specialized body segments fusedinto distinct regions such as headand thorax.4. Well-developed nervous systemwith large brain.5. Wide diversity of structures andfunctions related to obtainingnourishment.