Introduction to Animals Invertebrate Evolution and Diversity Chapter

Introduction to Animals Invertebrate Evolution and Diversity Chapter 25 Chapter 26. 1

Introduction to Animals Chapter 25

Characteristics of Animals • • • Kingdom – Animalia Multicellular Heterotrophic Eukaryotic Lack cell wall

Types of Animals • Invertebrates –Lack backbone or vertebral column – 95% of animals –Sea stars, worms, jellyfish, insects

• Chordates Exhibit four characteristics during at least one stage of life – Dorsal, hollow nerve cord – Notochord – Tail that extends beyond anus – Pharyngeal pouches Lancelet

• Chordates with backbones = Vertebrates – Fishes, amphibians, reptiles, birds, mammals

What Animals Do to Survive 1. Maintain homeostasis by gathering and responding to information – Feedback inhibition

2. Obtain and distribute oxygen and nutrients 3. Collect and eliminate CO 2 and waste 4. Reproduce

Animal Development Animals have a wide variety of forms. The following developmental factors determine the body plan: § Levels of organization : cells, tissue, organ systems § Arrangement of Germ layers: § differentiate into different tissue types: • Endoderm (inner): digestive tract • mesoderm (middle): muscles, blood • ectoderm (outer): skin, nervous system

Development, cont. § Overall Patterns of Embryological Development – Protostomes • Blastopore becomes mouth • Most invertebrates – Deuterostomes • Blastopore becomes anus • Chordates, Echinoderms (sea stars)

Development, cont. §Body Cavity Formation Coelom – completely lined with tissue derived from mesoderm Acoelom – lack a body cavity Pseudocoelom – partially lined with mesoderm

Development, cont. § Body symmetry: • Radial – body parts extend from a central point – Divides into equal halves • Bilateral – Right and left sides are mirror images of each other – Distinct anterior and posterior ends and dorsal and ventral sides

§ Segmentation – Repeating Parts – Worms, insects, vertebrates § Cephalization – concentration of sense organs and nerve cells at anterior end (head) § Limb Formation – Legs, Flippers, Wings

Cladogram of Animals • Phyla defined by: – Adult body plans – Patterns of embryological development • Ex. Phylum Arthropoda – Body plan bilateral symmetry – Segmentation – Cephalization – External skeleton – Jointed legs

Invertebrate Evolution and Diversity • Cladogram of invertebrates determined by – evolutionary relationships among major groups – sequence of evolution of important features

• Sponges – Phylum: Porifera (“pore bearers”) – Most ancient member of kingdom Animalia – Multicellular, heterotrophic, lack cell walls, contain few specialized cells – Clade Metazoa

• Cnidarians – jellyfishes, sea fans, sea anemones, hydras, corals – Aquatic, soft-bodied, carnivorous, radially symmetrical, stinging tentacles around mouths – Simplest animals with body symmetry and specialized tissues

• Nematoda (Roundworms) – Unsegmented worms – Pseudocoeloms – Specialized tissues and organs – Digestive tract with two openings

• Platyhelminthes – Flatworms – Soft – Unsegmented – Have tissues and internal organ systems – Bilateral symmetry – Cephalization – Do not have coeloms

• Annelids – earthworms, some marine worms, leeches – Segmented bodies – True coelom lined with tissue derived from mesoderm

• Arthropods – Phylum: Arthropoda – spiders, centipedes, insects, crustaceans – Bodies divided into segments – Exoskeleton – Cephalization – Jointed appendages

• Mollusks – Phylum: Mollusca – snails, slugs, clams, squids, octopi – Soft-bodied – Internal or external shell – True coeloms surrounded by mesoderm and complex organ systems – Free-swimming larva

• Echinoderms – Phylum: Echinodermata – sea stars, sea urchins, sand dollars – Spiny skin – Internal skeleton – Water vascular system – used for walking and gripping prey – Five-part radial symmetry

Other Hexacorallia Order: Class: Other Cnidaria Phylum: Sub-kingdom: Kingdom: Other invert. Chordates Animals Hexacorallia Cnidaria Invertebrates R. daphneae