Animal Form and Function. Vertebrate Animals. Kingdom Animalia. A combination of features distinguish the Animalia from all other Kingdoms

Transcription

1 Animal Form and Function Kight Vertebrate Animals Kingdom Animalia A combination of features distinguish the Animalia from all other Kingdoms 1. Eukaryotic cells. 2. Heterotrophic Thought Question: What eukaroytes are autotrophic? Are they animals? 3. No cell walls Thought Question: What eukaryotes have cell walls? Are cell walls pleisiomorphic or apomorphic for animals? For eukaryotes? 4. Animals are motile in at least part of the life cycle 5. Animals are multicellular. Thought Question: What does this do to the Protozoa? Should they be classified under the Kindom Animalia (they possess all of the other animal characteristics!)? If not, where? Thought Question: For the Kindom Animalia, are these characters apomorphic or pleisiomorphic? Does your answer change if we are considering all organisms?

2 Sub-Kingdom Eumetazoa - Sponges (discussed later) Sub-Kingdom Metazoa - all other multicellular animals There are several grades of multicellular organization: - cellular grade of organization - tissue grade of organization - organ grade - organ system grade Thought Question: Which grade of organization is pleisiomorphic within the Metazoa? Thought Question: Due to structural contraints, metazoans have extracellular spaces! Is this just wasted space? Discuss with examples from your own body. Super-Phylum Protostomia (most non-chordate animals) United by four developmental features: 1. Blastopore fate 2. Spiral Cleavage 3. Coelom schizocoelous 4. Mosaic Embryo Protostomate Phyla (most non-chordates - discussed later)

3 Super-Phylum Deuterostomia United by four developmental features: 1. Blastopore fate 2. Radial Cleavage 3. Coelom. enterocoelous 4. Regulative Embryo Thought Question: Note the points of divergence of the Deuterostomia and the Protostomia in the phylogenetic tree inside the front cover of your textbook. If this tree is correct, is mesoderm homologous in animals? Is the coelom homologous or homoplasious in animals? How must the tree be revised if mesoderm is homologous? Thought Question: Is it possible that the Kingdom Animalia is polyphyletic? Explain. Phylum Chordata Four features, in combination, distinguish chordates from all other animal phyla. 1. Notochord Thought Question: Notochord is the first part of endoskeleton to appear in the embryo. What does this imply about the evolution of the endoskeleton? Thought Question: What function does a notochord serve? Thought Question: Humans are chordates. Do you presently have a notochord? How can we be sure we are related to the chordates?

4 Chordata (continued) 2. Dorsal Tubular Nerve Cord Thought Question: Is your nerve cord (spinal cord) presently hollow? How can we be sure we are related to the chordates? Thought Question: Note that your skin is derived from ectoderm (the outer of three embryonic tissue layers). How can something inside your body (spinal cord) be derived from the same embryonic tissue? 3. Pharyngeal Pouches Thought Question: What is the function of pharyngeal slits? Thought Question: Do you presently have pharyngeal slits, grooves or pouches? How do you know you are a chordate? 4. Post-Anal Tail Thought Question: Can you think of an exception? Thought Question: What do the exceptions indicate about the function of a post-anal tail? Thought Question: What is the evolutionary relationship between chordates and non-chordates with post-anal tails? Do they share a tail gene from a common ancestor? Convergent Evolution Mole v. Mole Cricket Fish v. Dolphin Thought Question: How can zoologists avoid polyphyletic classification of convergently evolved organisms? Thought Question: Do you presently have a post-anal tail? How do you know you are a chordate?

5 Sub-Phylum Urochordata (tunicates - discussed later) Sub-Phylum Cephalochordata (lancelets - discussed later) Sub-Phylum Vertebrata Unifying feature: Anterior end of nerve cord becomes enlarged to form the brain. Brain encased in protective structure = cranium Major Evolutionary Innovations of Vertebrates 1. Living Endoskeleton Thought Question: An endoskeleton has allowed vertebrates to evolve large body size, while exoskeletons have constrained other animals (i.e. insects) to smaller body sizes. Why? Answer lies in the physics of a cylinder! Thought Question: Why might an endoskeleton be more advantageous for small animals? Thought Question: At least two parts of the vertebrate endoskeleton are functionally exoskeletons. What are they, and why are they adaptive? 2. Pharynx leads to highly effecient respiration Thought Question: Is an endoskeleton enough to favor large body size? Is efficient respiration also necessary? If so, why? 3. Complex Nervous System Thought Question: Can you think of any non-vertebrate mobile predators? What predictions do you make about their nervous systems? Cephalopods Homology or homoplasy?

6 Vertebrata (continued) 4. Paired Limbs Thought Question: Why are jointed limbs better than nonjointed limbs for land-dwellers? Thought Question: Can you think of any non-vertebrate animals with jointed appendages? What predictions can you make about where such animals live? Vertebrate Phylogeny Thought Question: Compare Figure 15-3 with Figure In one cladogram, the vertebrates contain at least one polyphyletic and the other represents the same organisms as paraphyletic. Which is which? Which do you think is more accurate? Why are the two figures different? What does this imply about the nature of science? Thought Question: What will have to be done to make the vertebrate classes monophyletic? Thought Question: Remember that vertebrates are deuterostomes (remind yourself of what that means). However, vertebrates exhibit schizocoelous (splitting) coelom formation. What does this imply about the evolution of the coelom in Kingdom Animalia? Express your answer using any of the following concepts: homology, homoplasy, monophyly, polyphyly. Super-Class Agnatha (jawless fishes - discussed later)

7 Super-Class Gnathostomata (gnatha=mouth, stoma=mouth) Cartilaginous or bony vertebrae form from the sheath around notochord, subsequently replacing notochord as chief mechanical axis of body. Thought Question: Note that not all Vertebrata have vertebrae! What feature truly unites all organisms in the Vertebrata? Modern taxonomy assigns a different name to the Vertebrata. Can you guess what it is? Class Chondrichthyes (sharks, rays - discussed later) Class Osteichthyes (bony fishes - discussed later) Class Amphibia (salamanders, caecilians, frogs - discussed later) Amniote Gnathostome Classes (amniotic eggs - discussed later) Class Reptilia (paraphyletic - turtles, snakes, lizards - later) Class Aves (birds - discussed later) Class Mammalia (mammals - discussed next)