Some things to think about… What are some characteristics that allowed animals to move from water to land? What is the name of the super continent that was formed around 220 MYA?

The wonderful world of animals A Brief Intro to Animal Phylogeny

Pill Bug Wood Louse Sow Bug Roly-Poly Doodle Bug Porcellio scaber Potato Bug

Flowchart Linnaeus’s System of Classification Kingdom Phylum Class Section 18-1 Linnaeus’s System of Classification Kingdom Phylum Class Order Family Genus Species

Binomial Nomenclature Use Capitalized Genus and lower case species name. Underline or Italicize

Figure 18-5 Classification of Ursus arctos Section 18-1 Grizzly bear Black bear Giant panda Red fox Abert squirrel Coral snake Sea star KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Ursidae GENUS Ursus SPECIES Ursus arctos

CLASSIFICATION BASED ON VISIBLE SIMILARITIES Traditional Classification Versus Cladogram Section 18-2 Appendages Conical Shells Crustaceans Gastropod Crab Barnacle Limpet Crab Barnacle Limpet Classifying organisms just on physical similarities can lead to problems Molted exoskeleton Segmentation Tiny free-swimming larva CLASSIFICATION BASED ON VISIBLE SIMILARITIES CLADOGRAM

1. Which characteristic unites the horse in a clade with wolves, leopards, and house cats? Which characteristic excludes the horse? hair; carnivorous teeth

2. The crocodile is a scaly, meat eating reptile 2. The crocodile is a scaly, meat eating reptile. Could it be included in the clade with the wolf, leopard, and house cat? Explain. No. The crocodile does not have hair, so it would have been excluded before that point in the cladogram.

So…what is an Animal? Take 3-4 minutes and talk this over with your partner/group. Come up with a definition that YOU think is sufficient for describing the class of organisms we call ‘animals’ Your definition must be able to distinguish between animals and other kingdoms.

Animal Phylogeny – the Major Phyla

Classifying organisms A number of different characteristics are used to classify the animal phyla. We’ll take a look at some of the main examples: Body symmetry Germ layers Body cavities

Presence vs. Absence of Tissues Almost all animals have tissues Remember – a tissue is a group of cells that have a specific and coordinated function. Sponges (phylum porifera) are the one animal phylum that lacks true tissues

Body symmetry Animals typically have either radial or bilateral symmetry. Radial symmetry is exhibited by cnidarians and echinoderms. **However – echinoderms have bilateral larva and so are considered to have ‘readopted’ radial symmetry.

Planes of symmetry in a bilateral organism

Cephalization Bilateral organisms tend to exhibit cephalization – the concentration of nervous tissue toward the ‘head’ – or anterior – end.

Germ Layers Not all organisms have the three germ layers we discussed in development. Some organisms lack mesoderm. Cnidarians are an example of these and are considered ‘diploblastic’ All other phyla are triploblastic

Refresher Don’t forget about your development and embryology. Remember what each part of the embryo becomes!

Body Cavity – the Coelom! The presence of a coelom is another key characteristic used to separate phyla. A true coelom is a body cavity surrounded by mesoderm.

Coeloms galore… Cnidarians and platyhelminthes do NOT have coeloms. Other phyla are known as ‘psuedocoelomates’ because they have a body cavity that is not enclosed by mesoderm – rotifers and nematodes.

Coeloms rule! All other phyla have true coeloms – including us. Where is YOUR coelom? Can you find it? How does the coelom form during embryonic development?

Protostomes vs. Deuterostomes All true coelomates are divided into protostomes and deuterostomes There are several key characteristics that can be used to distinguish between the two

1. Coelom formation Enterocoely vs. schizocoely – two different methods of mesoderm and coelom formation. Protostomes Deuterostomes

2. Cleavage of the early embryo Protostomes – spiral cleavage, determinate cleavage Deuterostomes – radial cleavage, indeterminate

3. Fate of Blastopore Protostomes – Mouth! Deuterostomes – Anus!

Who is who? Protostomes – annelids, mollusks, arthropods Deuterostomes – echinoderms and chordates

Preview As we go throughout the invertebrates, we’ll focus on a few of the major phlya: Cnidaria Platyhelminthes Annelida Arthropoda Mollusca Echinodermata

Vertebrates! When we talk about vertebrates, we’ll discuss: Osteichthyes Chondrichthyes Amphibia Reptilia Mammalia NOTE; these are classes within the phylum chodata!

Things to keep in mind As we go through each phylum, think about the MAJOR characteristics of the organisms we discuss. Don’t get caught up in the minutae. Examples: How do the organisms get food? How do they move around? How do they transport nutrients/gases? How do they coordinate their functions? How do they reproduce? Thinking about these ‘BIG’ things will help you remember the little things.

Phyla Cnidaria and Platyhelminthes Jellyfish, Hydra, Anemones, and Flatworms!!!

But first…Porifera! Organisms from the phylum porifera are commonly known as ‘sponges’

Sponges without squarepants Sponges are sessile (do not move around), organisms that lack true tissues and organs. Their most notable feature are collar cells (choanocytes) which draw in water and filter out food. Many of their cells appear to function independently of each other.

Collar Cells

Cnidarians Organisms from the Phylum Cnidaria are those we think of as anemones, jellyfish, and hydra. They have true tissue, but lack mesodermal tissue. Instead they have a jelly-like matrix called mesoglea. Because they lack mesoderm, they are known as diploblastic. Radial symmetry

Men-o-War We usually think of jellyfish as being able to ‘sting’ us. And they can. All cnidarians are characterized by special cells called cnidocytes. Cnidocytes contain specialized organelles called nematocysts that are capable of ‘stinging’ and injecting toxins. Some jellyfish are very toxic and can kill larger animals. Think ‘Finding Nemo’…

Anatomy of a Hydra Gastrodermis: inner lining of gastrovascular cavity (GVC) that contains specialized cells for digestion. Mesoglea Tentacles: contain cnidocytes with nematocysts

Typical Medusa body plan

Phylum Platyhelminthes Phylum platyhelminthes are commonly known as ‘flatworms’ They include planarians, flukes, and tapeworms. They are triploblastic, but lack a true coelom. Their coelem is NOT surrounded by mesoderm.

Tapeworms!

Blood and Liver Flukes!

Planaria The ‘typical’ example of a flatworm, planaria are used in many laboratory experiments

Flatworm anatomy - digestion

Flatworm anatomy - nervous

Nematodes (roundworms) Found in moist habitats, these are often parasites of animals and plants. One example is the soil nematode C. Elegans – one of our ‘model’ organisms. Remember the vulva development? ‘Pseudocoelomates’ – have a body cavity but it is NOT enclosed by mesoderm.

Phylum Rotifera Small pseudocoelomates that inhabit freshwater. Crown of cilia draw water into mouth and food is ground up by a pair of jaws in the pharynx.

Where we are so far…