ANIMAL CLASSIFICATION, PHYLOGENY, AND ORGANIZATION

I. So, how do we go about organizing the study of zoology?

A. About 1.4 million species have been identified and named.

1. _______________________ of the named species are animals.

2. 4-30 million species remain undescribed.

B. Each species is given a genus and species name: _______________

_______________________.

1. Binomial nomenclature was developed by _________________

_______________________ (Karl von Linné) in 1735.

C. _______________________ – the description of species & the

classification of organisms into groups that reflect evolutionary

relationships. Taxonomic categories above the species level are based

on the idea of shared ancestry (and therefore shared characteristics).

1. Currently, the major groups recognized are…

a. domain – e.g. Eukarya

b. _______________________ – e.g. Animalia

c. __________________ – there are 36 extant animal phyla

d. _______________________

e. _______________________

f. _______________________

g. _______________________

h. _______________________

2. Closely related species are placed in the same genus; closely

related genera are placed in the same family, and so on.

3. A _______________________ is a general term used to

represent a name-bearing group of animals at any level of the

classification scheme.

a. Animals are placed within a taxon based upon shared

traits.

1) Traits used may be morphological or molecular

(DNA and proteins of presumed related organisms

are compared).

D. _______________________ is the arrangement of organisms based

on evolutionary relationships indicated by shared characters.

1. Modern zoologists attempt to correlate taxonomy and

systematics and both disciplines often support each other.

2. The groups formed in modern systematics are designed to be

monophyletic (in a perfect world, all groups would be

monophyletic, but we still have a lot to learn about the animal

kingdom).

a. _______________________ groups include all

organisms that have arisen from a single ancestral taxon.

b. _______________________ groups are artificial

groupings whose members have arisen from separate

ancestors

c. _______________________ groups include only some of

the members of a lineage due to incomplete knowledge of

the entire group.

II. What are the evolutionary trends in the animal kingdom?

A. Body Symmetry

1. _______________________ – without a balanced

arrangement of similar parts on either side of a point or axis.

a. Found in many protists and sponges

b. such animals lack complex sensory and locomotory

functions.

2. _______________________ symmetry occurs when any plane

passing through the longitudinal axis divides the body into mirrored

halves, as in cutting a pie. These animals are examples of the

Radiata.

a. the Cnidaria (e.g. hydra, jellyfish, and corals)

3. In _______________________ symmetry, an organism can be

cut in a sagittal plane into two mirror halves.

a. this usually provides for a head (___________________)

in bilateral animals classified in the ___________________.

b. Terms of direction…

1) _______________________ indicates the head

end; the opposite or tail end is __________________.

2) _______________________ is the back side and

_______________________ is the front or belly side.

3) _______________________ is on the midline of

the body; _______________________ is to the sides.

4) _______________________ parts are far from the body; _______________________ parts are near.

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c. Planes of direction…

1) A _______________________ plane divides the

body into dorsal (back) and ventral (front) halves.

2) A _______________________ plane divides an

animal into right and left halves.

3) A _______________________ plane (or cross

section) separates anterior (head) and posterior (tail)

portions.

d. Terms of body region…

1) In vertebrates, _______________________ is the

chest region or area supported by the forelegs.

2) _______________________ refers to the hip

region or area supported by the hind legs.

ed by the hind legs.

B. Levels of cellular organization

1. Unicellular _______________________ groups are the simplest

animal-like organisms.

a. Within the cell, they perform all basic functions.

b. Exhibit the _______________________ level of

organization.

c. They do not form tissues.

2. The _______________________ includes all multicellular

animals. Some zoologists subdivide the metazoans into three

groupings….

a. the Mesozoa (an odd group of organisms not typically

covered in introductory classes)

b. the _______________________ (a group that includes

the cnidarians e.g. sponges)

1) Show radial symmetry

2) Have a _______________________ grade

organization with cells working closely together as a

unit.

c. the _______________________ (this group includes

everything else called an animal)

1) Show bilateral symmetry and are known as the

Bilateria.

2) Have an _______________________ level of

organization – many tissues working together in an

organ.

C. Complexity and Body Size

1. Small animals

a. BENEFITS –

b. COSTS –

2. “______________________________________________”

noted that lineages began with small individuals and eventually

evolved toward giant forms; it holds for nonflying vertebrates and

many invertebrates.

3. More complex grades of metazoan organization permit and

promote evolution of large body size.

a. Surface area increases are the square of body length,

volume is the cube of body length.

b. A large animal has ___________________ surface area

compared to its volume, than does a smaller animal.

c. Flattening or infolding the body increases surface area, as

in flatworms.

d. Most animals had to develop internal transports systems

to shuttle nutrients, gases and waste products, as they

became larger.

4. Benefits of Being Large

a.

b.

c.

d.

E. The presence of a body cavity (not the gut cavity, but a cavity external

to the gut):

1. The Coelom

a. The major evolutionary innovation of Bilateria is the

coelom.

b. The _______________________ is a fluid-filled space

around the gut; it provides a tube-within-a-tube arrangement

with greater flexibility.

c. A coelom provides more space for organs, a greater

surface area for exchange, and an increase in body size.

d. Worms rely on the coelom for a _____________________

_______________________ to aid in burrowing.

2. _______________________ Bilateria – 3 phyla, the flatworms,

ribbon worms, & jaw worms - often called the “solid worms.”

a. Acoelomate animals lack a body cavity surrounding the

gut.

b. Internal regions are filled with mesoderm and a spongy

mass of parenchyma from ectodermal cells.

3. _______________________ Bilateria – 9 phyla including

rotifers & nematodes

a. Nematodes and some others have a cavity around the gut

but it is derived from the _______________________ of the

embryo.

b. It provides a tube-within-a-tube but it is not derived from

mesoderm.

4. _______________________ Bilateria – all other complex

animals

a. A true coelom is lined with mesodermal peritoneum.

F. _______________________ (Segmentation)

1. Metamerism is serial repetition of similar body segments.

2. Each segment is a metamere or _______________________.

3. True metamerism is found in Annelida, Arthropoda and

Chordata; other groups show a superficial segmentation.

G. _______________________

1. Differentiation of the head, or cephalization, is mainly found in

bilaterally symmetrical animals.

2. Concentrating the sense organs at the head, as well as the

mouth, is efficient for sensing and responding to the environment

and food.

3. Polarity is the gradient in activities between anterior and

posterior ends.