Download Vertebrate Animals

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?
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)
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?
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?
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?
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 26-3. 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)
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)