Download 2 Notes (Phylogeny II)

BIOLOGY 110
Lecture 2 (Sept. 13 2013)
J. Greg Doheny
NOTES: Classification of Animals (Chapter 32)
Quiz Questions:
1. What is the name of the clade that all animals are members of?
2. Do humans show a Protostome or a Deuterostome development pattern?
3. Does the blastopore become the mouth in the Protostome or the Deuterostome pattern of
development?
4. Do humans have radial or bilateral symmetry?
5. What is the general name for the class of genes that determine the symmetrical body plan of
animals?
6. What is the name for an internal body cavity formed from folds in the Mesoderm of an animal?
7. A shark had a fin called a ‘dorsal fin.’ Would you expect to find this fin on its back or its belly?
8. Which is the only Phylum in the animal kingdom that has no symmetry and no body plan? What
is the common name for the members of this Phylum?
NOTES:
Common Features of Animals: All are multicellular, eukaryotic, heterotrophs. Not all are motile. All
are ‘diploid’ (having two copies of their genome). All reproduce sexually, but some are capable of
parthenogenesis. All are members of the Domain Eukarya and the Kingdom Animalia (the ‘Animal
Kingdom’). There are several Phyla and thousands of species in the Animal Kingdom. There are also
some classifications in between the Kingdom and the Phyla that aren’t officially part of the Linneaen
classification system, but you’ll have to know them anyway.
GENERAL CLASSIFICATION of ANIMALS
 All are members of the Domain Eukarya
 All are members of the Kingdom Animalia
 All are members of a clade called Metazoa (they are ‘metazoans’)
 Animals have specialized tissues that are formed during development. The tissues are called the
Ectoderm (outside), the Endoderm (inside), and sometimes a third tissue called the Mesoderm
(middle). When at least the Ectoderm and Endoderm are fully differentiated (distinguishable
from one another) the animals are members of the Eumetazoa (they are ‘eumetazoans’).
 If they have ‘bilateral symmetry’ (see below) they are members of the Bilateria.
 All animals develop from a fertilized egg (zygote) into a blastula, and then undergo gastrulation.
(Blastula folds in on itself to form a hollow core (archenteron), with a hole leading to the outside
(blastopore). The inner and outer tissues become the ectoderm, endoderm, and sometimes the
mesoderm.
 After gastrulation, two different patterns of embryonic development separate them into either
the Protostomia or the Deuterostomia. Notable differences: in Protostome development the
blastopore becomes the mouth. In Deuterostome development the blastopore becomes the
anus.
 All animals eat food and excrete waste products. Higher animals have a mouth to eat and an
anus to excrete. Lower animals use the same hole (originally the blastopore) for both purposes.

Classification beyond this is dependent on having or not having individual traits.
Body Plan vs. No Body Plan: (symmetry vs. Asymmetry). Phylem Porifera (‘sponges’) are the only
animals that don’t have a genetically pre-determined body shape. Other animals have some degree of
symmetry. A symmetrical body plan is determined by a special set of genes called Homeotic Genes
(sometimes known as ‘homeobox genes,’ and abbreviated as HOX genes).
EXAMPLES:
Asymmetrical: Phyla Porifera
Symmetrical: all others Phyla
Radial vs. Bilateral Symmetry: Radial symmetry means it has a shape that is symmetrical if you rotate
it 360 degrees (ie-like a Sea Anemone). Bilateral symmetry means the right side and left side are
identical (ie-HUMANS). In addition to a left and right hand side, bilateral organisms also have a dorsal
(back), ventral (front), anterior (top) and posterior (bottom) side. Most show ‘cephalization’ (the
formation of some sort of a head).
EXAMPLES:
Radial Symmetry: Phyla Cnidaria (sea anemones, jellies, hydras)
Bilateral Symmetry: all other Phyla (excluding Porifera) ie-Phyla Chordata
Formation of an alimentary canal: (One hole to eat and excrete vs. two separate holes, connected by an
alimentary canal) Lower animal phyla eat and excrete through the same hole. Higher ones use separate
holes.
Protostome vs Deuterostome Development: All animals become a blastula, and undergo gastrulation,
where a hollow center is formed, and a single hole (blastopore). Some animals stop there and use the
same hole to eat and excrete (ie-Phyla Cnidaria). Higher animals form another hole. One is to eat and
the other to excrete. The hollow cavity that connected them (the archenteron) becomes the alimentary
canal. In Protostome development (ie-Phylum Mollusca [clams, snails etc.]) the original blastopore
becomes the mouth. In Deuterostome development (ie-Phylum Chordata) the blastopore becomes the
anus.
Diploblastic vs. Triploblastic: If just two tissue layers form during development (Ectoderm and
Endoderm) the organism is ‘diploblastic.’ If a third layer is formed in between (the Mesoderm) it is
‘triploblastic.’
Triploblastic: Coelomate, Pseudocoelomate, and Acoelomate. The Ectoderm forms the outer layer of
the body, and the Endoderm forms the digestive cavity (alimentary canal). If the Mesoderm is folded in
on itself, leaving a fluid-filled cavity, that cavity is called a Coelom. If the Mesoderm is folded in such a
way that it is in contact with both the Ectoderm and Endoderm, and still forms cavities, the organism is
said to be a Coelomate (ie-earthworms). If the Mesoderm is attached to the Ectoderm but not the
Endoderm, leaving a fluid-filled space in between it is said to be a Pseudocoelomate. If the Mesoderm is
attached to both the Ectoderm and Endoderm, but forms no cavities in between it is said to be an
Acoelomate. (The prefix “A-“ usually means “lack of” in science. Ie-Asymmetry [no symmetry], or
Acoelomate [no coelom].)
PRACTICE QUESTIONS:
1. Describe in point form the defining differences between Protostome and Deuterostome
development.
2. Describe in point form the defining differences between a Radial Symmetry body plan, and a
Bilateral Symmetry body plan in animals.
3. Briefly describe the difference between a diblastic and a triploblastic animal.
4. Briefly describe the difference between a Coelomate, a Pseudocoelomate, and an Acoelomate.
5. Briefly describe the difference between a Metazoan and a Eumetazoan.
Extended Matching: Match the term to the definition.
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
Acoelomate
Alimentary
Anterior
Archenteron
Bilateral Symmetry
Blastopore
Blastula
Cephalic
Coelomate
Deuterostome
Diblastic
Dorsal
Ectoderm
n.
o.
p.
q.
r.
s.
t.
u.
v.
w.
x.
y.
z.
Endoderm
Eumetazoa
Gastrula
Homeotic
Hox
Mesoderm
Metazoan
Posterior
Protostome
Pseudocoelomate
Radial Symmetry
Triploblastic
Ventral
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Anatomical name for the back part of an animal.
Anatomical name for the bottom part of an animal.
Term for an animal that has three tissue types (ectoderm, mesoderm, endoderm).
Name for the gastrulation pattern shown by certain types of animals, including humans.
Anatomical name referring to an animal’s head.
Term for an animal that has only two tissue types (ectoderm and endoderm).
A pattern of development where the blastopore becomes the mouth in the adult animal.
A ball of cells that folds in upon itself early in development.
A type of body pattern where the animal looks the same when rotated through 360 degrees.
A tissue formed early in development that lies between the endoderm and the ectoderm.
Class of genes that is responsible for determining an animal’s symmetrical body plan.
The hole at the bottom of a gastrula.
The type of gastrulation pattern shown by the Phylum Mollusca (clams, snails etc.).
Name for the hollow interior of a gastrula.
Name for a metazoan that has well defined tissues, and an ectoderm can be clearly
differentiated from an endoderm.
16. Name for the tissue on the outside of the gastrula, that eventually becomes the outside of the
animal.
17. Abbreviation for homeotic genes.
18. An animal whose Mesoderm has no pockets in it.
19. Name of the canal (tube) that connects the mouth to the anus, and forms the digestive tract.
20. Name for the top part of an animal.
21. Name for the tissue that lines the interior of the gastrula, and eventually becomes the animal’s
digestive tract.
22. A hollow ball of cells (resembling a soccer ball) that forms in the early stages of development.
23. An animal whose left side is a mirror image of its right side is said to have this.
24. Name of a pocket formed by folds in an animal’s mesoderm.
25. A type of development where the blastopore becomes the anus.
26. Anatomical name for the back of an animal.