Download CHAPTER 3 STUDY GUIDE: ANIMAL ARCHITECTURE

CHAPTER
3.1
2.2
2.3
3.4
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3 STUDY GUIDE: ANIMAL ARCHITECTURE
New Designs for Living
A. Levels of Organization in Organismal Complexity (Table 3.1)
1. Zoologists recognize 32 major phyla of living multicellular animals.
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2. 500 million years ago in the Cambrian, nearly 100 phyla had evolved representing nearly all major
modern body plans.
3. Major body plans are the result of extensive selection and are a limiting determinant of future
adaptation variants.
4. Animals share structural complexities that reflect common ancestry.
The Hierarchical Organization of Animal Complexity
A.
Unicellular versus M ulticellular Organisms
1. Unicellular protozoan groups are the simplest animal-like organisms.
a. W ithin the cell, they perform all basic functions.
b. Diversity is achieved by varying architectural patterns of subcellular structures, organelles and
the whole cell.
2. Metazoa are multicellular animals.
a. Cells become specialized parts of a whole organism; these cells cannot live alone as do
protozoan cells.
b. Simplest metazoans show a cellular grade of organizations and are not strongly associated to
perform a collective function.
3. More complex metazoans have a tissue grade organization with cells working closely together as
a unit.
4. Many tissues work together in an organ; most metazoans operate at the organ system level.
5. Parenchyma are the chief functional cells of an organ; supporting tissues are named stroma.
Complexity and Body Size
A.
Comparisons
1. More complex grades of metazoan organization permit and promote evolution of large body size.
2. Surface-area-to-volume ratios have important consequences for animal respiration, heat, etc.
a. Surface area increases are the square of body length; volume is the cube of body length.
b. A large animal has less 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.
3. “Cope’s Law of Phyletic Increase” noted that lineages began with small individuals and
eventually evolved toward giant forms; it holds for nonflying vertebrates and many invertebrates
(Figure 3.17).
4. Benefits of Being Large
a. Larger size buffers against environmental fluctuations in temperature, etc.
b. Size provides protection against predators and promotes offensive tactics.
c. Cost of maintaining body temperature is less per gram of weight in large than in small animals.
d. Energy costs of moving a gram of body over a given distance are less for larger animals
(Figure 3.18).
Extracellular Components of the M etazoan Body
A. Body fluids and extracellular structural elements are noncellular components of metazoan animals.
1. In contrast to intracellular fluids, extracellular fluids are outside the cells.
2. Blood plasma and interstitial fluid (lymph) are part of the extracellular fluids in open and closed
circulatory systems.
3. Architectural extracellular structural elements include loose connective tissue and bone in
vertebrates, cartilage in mollusks, and cuticles in arthropods, nematodes, and annelids.
Tissues
A.
Types of Tissues
11. Histology is the study of types of tissues (Figure 3.11).
2. Epithelial Tissue (Figures 3.11, 3.12).
a. Epithelium is a sheet of cells that covers an internal or external surface.
b. It provides outside protection and internal linings, often modified to produce lubricants,
hormones or enzymes.
c. Simple epithelia are found in all metazoa.
d. Stratified epithelia are restricted to vertebrates.
3.6
e. All epithelia have an underlying basement membrane.
f. Blood vessels never penetrate epithelial tissues.
3. Connective Tissue (Figure 3.13)
a. Connective tissues are nearly everywhere in the body.
b. It is made up of few cells, many extracellular fibers and a ground substance or matrix.
c. In vertebrates, there are two types of connective tissue proper.
1) Loose connective tissue has fibers and both fixed and wandering cells in a syrupy matrix.
2) Dense connective tissues (e.g., ligaments and tendons) are characterized by densely
packed fibers.
d. Much fibrous tissue is made of protein collagen, the most abundant protein in the animal
kingdom.
e. Connective tissue also includes blood, lymph and tissue fluid.
f. Cartilage is semi-rigid connective tissue with closely packed fibers embedded in a gel-like
matrix.
g. Bone is calcified connective tissue with calcium salts organized around collagen fibers.
4. M uscular Tissue (Figure 3.7)
a. Muscle is the most abundant tissue in most animals.
b. Muscle originates from mesoderm.
c. The cell is the muscle fiber, specialized for contraction.
d. Striated muscles include skeletal and cardiac muscles.
e. Smooth muscles lack the alternating bands seen in striated muscle.
f. Myofibrils are contractile elements and the unspecialized cytoplasm is sarcoplasm.
5. Nervous Tissue (Figure 3.8)
a. Nervous tissue receives and conducts impulses.
b. Nervous tissue cell types are neurons and neuroglia that support the neurons.
Animal Body Plans
A. Animal Symmetry (Figures 3.9, 3.10)
1. Spherical symmetry occurs when any plane divides the body into mirrored halves, as in cutting a
globe in half.
2. Radial symmetry occurs when any plane passing through the longitudinal axis divides the body
into mirrored halves, as in cutting a pie; the Cnidaria and Ctenophora are the Radiata.
3. Biradial symmetry occurs in an animal that is radial except for some paired feature that allows
only two mirrored halves.
4. In bilateral symmetry, an organism can be cut in a sagittal plane into two mirror halves; this
usually provides for a head (cephalization) in bilateral animals classified in the Bilateria.
B. Body Regions (Figure 3.11)
11. Anterior indicates the head end; the opposite or tail end is posterior.
2. Dorsal is the back side and ventral is the front or belly side.
3. M edial is on the midline of the body; lateral is to the sides.
4. Distal parts are far from the body; proximal parts are near.
5. A frontal plane divides the body into dorsal and ventral halves.
6. A sagittal plane divides an animal into right and left halves.
7. A transverse plane (or cross section) separates anterior and posterior portions.
8. In vertebrates, pectoral is the chest region or area supported by the forelegs.
C. Patterns of Cleavage
1. The zygote is a fertilized egg (one single cell) that divides into smaller cells named
blastomeres.
2. Radial cleavage (regulative): planes are symmetrical to the polar axis and produce tiers, or
layers (Figure 3.12A).
3. Spiral cleavage (mosaic): cleaves obliquely to the axis and typically produces a quartet of
cells
(Figure 3.12B).
4. Cleavage patterns illustrate a fundamental dichotomy— an early divergence into two
separate
Groups of phyla: Protostomia (“mouth first”) and Deuterostomia (“mouth second”).
5. In regulative development, an early blastomere separated from the embryo develops into a
complete larva.
6. In mosaic development, separated early blastomeres develop into partial defective larva.
7. See developmental tendencies of protostomes and deuterostomes in Figure 3.8.
8. The zygote develops into a multicelled blastula with a fluid filled cavity called a blastocoel.
9. The blastula becomes a two layered stage the gastrula with ectoderm and endoderm layers.
10. The endoderm surrounds an inner body cavity called the gastrocoel which becomes the gut
cavity.
D. Body Cavities and M esoderm and Coelomic Formation (Figures 3.15, 3.16)
1. The Coelom
a. The major evolutionary innovation of Bilateria is the coelom.
b. The coelom 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 and surface area for exchange.
d. W orms rely on the coelom for a hydrostatic skeleton to aid in burrowing.
2. Acoelomate Bilateria
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.
c. Flatworms are acoelomate.
3. Pseudocoelomate Bilateria
a. Nematodes and some others have a cavity around the gut but it is derived from the blastocoel
of the embryo.
b. It provides a tube-within-a-tube but it is not derived from mesoderm.
c. Mesoderm only lines the outer edge of the blastocoel, it lacks peritoneum.
44. Eucoelomate Bilateria
a. A true coelom is lined with mesodermal peritoneum.
b. It is formed in one of two methods but both produce a mesodermal peritoneum.
1) Schizococoelous formation involves splitting of mesodermal bands that originate from
cells in the blastopore region.
2) Enteroceolous formation comes from pouches of the archenteron or primitive gut.
E.
M etamerism (Segmentation)
1. Metamerism is serial repetition of similar body segments.
2. Each segment is a metamere or somite.
3. True metamerism is found in Annelida, Arthropoda and Chordata; other groups show a superficial
segmentation.
F. Cephalization
11. 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.