Final Exam: Chapters 30, 31, 32

Question 1

What characters are common to most animals?

Answer 1

Eukaryotic
Multicellular
Heterotrophic
Most have cells specialized for specific functions

Question 2

Animals have diverse body plans.

Answer 2

Most animals:
are capable of locomotion at some time during life cycle
can respond adaptively to external stimuli
can reproduce sexually

Question 3

Explain sexual reproduction.

Answer 3

Sperm and egg unite (zygote)
Zygote undergoes cleavage and cell divisions produce hollow ball of cells (blastula)
Blastula undergoes gastrulation (develops) and forms embryonic tissues

Question 4

Use current hypotheses to trace the early evolution of animals.

Answer 4

Proterozoic eon
most animal clades diverged over long period
based on fossil record and molecular data

Cambrian Radiation (Cambrian Explosion)
> 500 mya
new body plans rapidly evolved among clades
first fossils of these animals

Hox gene group
controls early development in all animal groups (except sponges)
same genes shared among all animals
proposed to have evolved in cambrian 500 mya*

Cambrian period
many Hox genes had evolved
mutations could have resulted in rapid changes in animal body plans

Question 5

Can biologists use structural characters (variations in body symmetry, number of tissue layers, type of body cavity) and patterns of early development to infer relationships among animal phyla?

Answer 5

Cnidarians and ctenophores are closely related because they share radial symmetry and most other animals exhibit bilateral symmetry.
Cephalization (development of head) evolved with bilateral symmetry.
Relationships can be based on level of tissue development and type of body cavity.

Question 6

Explain the germ layers.

Answer 6

Outer layer (ectoderm): gives rise to body covering, nervous system
Inner layer (endoderm): lines the gut and other digestive organs
Middle layer (mesoderm): gives rise to most other body structures

Question 7

Define cephalization.

Answer 7

Cephalization (development of head) evolved with bilateral symmetry.

Question 8

Explain body cavity: acoelomate, pseudocoelomate, (“true”) coelmate

Answer 8

Coelom: fluid filled space between body wall and digestive tube. “tube within a tube”
Acoelomate: no body cavity
Pseudocoelomate: body cavity not completely lined with mesoderm
Coelomate, (animal with true coelom): body cavity completely lined with mesoderm

Question 9

What are the two major evolutionary branches of bilateral animals?

Answer 9

Protostomia: mollusks, annelids, arthropods
Deuterostomia: echinoderms, chordates

Question 10

Explain coelom formation.

Answer 10

picture?

Question 11

Explain blastopore.

Answer 11

Opening from embryonic gut to outside.
In protostomes: develops into the mouth
In deuterostomes: becomes the anus

Question 12

Explain cleavage in protostomes.

Answer 12

undergo spiral cleavage
early cell divisions diagonal to polar axis
undergo determinate cleavage
fate of each embryonic cell is fixed very early

Question 13

Explain cleavage in deuterostomes.

Answer 13

undergo radial cleavage
early cell divisions either parallel or at right angles to polar axis
cells lie directly above or below one another
undergo indeterminate cleavage
fate of each embryonic cell is more flexible

Question 14

What are three major contributions to animal phylogeny made by molecular systematics?

Answer 14

Confirmed much of animal phylogeny based on structural characters; including axiom that animal body plans usually evolved from simple to complex.
Provided evidence for exceptions to “simple-to-complex” rule. Example: molecular data indicate flatworms and ribbon worms evolved from more complex animals, became simpler over time
Molecular data suggest pseudocoelomate animals do not form natural group; probably evolved from coelomate ancestors and are not monophyletic.
2 clades based on molecular data: Lophotrochozoa and Ecdysozoa (animals that molt)

Question 15

Identify the three major clades of bilateral animals.

Answer 15

Lophotrochozoa: flatworms, ribbon worms, mollusks, annelids, lophophorate phyla, rotifers
Ecdysozoa (animals that molt): nematodes and arthropods
Deuterostomia: echinoderms and chordates

Question 16

What are the distinguishing characteristics of phylum Porifera?

Answer 16

Sponges: animals characterized by flagellate collar cells (choanocytes). Similar to Choanoflagellates. The only members of the Parazoa
Sponge body: sac with tiny openings for water to enter, central cavity (spongocoel), open end (osculum) for water to exit
Sponge cells: loosely associated and do not form true tissues
Sponges (phylum Porifera) are characterized by collar cells and by loosely associated cells that do not form true tissues.

Question 17

What are the distinguishing characteristics of phylum Cnidaria?

Answer 17

Characterized by radial symmetry, two tissue layers, and cnidocytes (cells containing nematocysts).
Gastrovascular cavity with single opening for mouth and anus.
Nerve cells form irregular, non-directional nerve nets
connect sensory cells with contractile and gland cells.
Members of phylum Cnidaria (hydras, jellyfish, sea anemones) are characterized by radial symmetry, two tissue layers, and cnidocytes, cells that contain stinging organelles.

Question 18

Describe classes of the phylum Cnidaria. Give examples of animals that belong to each class.

Answer 18

4 Classes (only need to know 2):

1. Class Hydrozoa (hydras, hydroids, Portuguese man-of-war): typically polyps and may be solitary or colonial
2. Class Scyphozoa (jellyfish): generally medusae

Question 19

Explain the Cnidarian life cycle.

Answer 19

Sessile polyp stage form with dorsal mouth surrounded by tentacles.
Free-swimming medusa (jellyfish) stage.

Question 20

What are the distinguishing characteristics of phylum Ctenophora?

Answer 20

Comb jellies:
fragile, luminescent marine predators
biradial symmetry (equal halves cutting through the body axis in two different ways)
eight rows of cilia that resemble combs
tentacles with adhesive glue cells

Question 21

Describe the coelom.

Answer 21

A space in which internal organs develop (including gonads), helps transport materials, and protects internal organs.

Question 22

Characterize the protostomes.

Answer 22

Characterized by spiral cleavage, determinate cleavage, and development of mouth from blastopore.
Monophyletic group that gave rise to two major clades: Lophotrochozoa and Ecdysozoa.

Question 23

Describe protostome two main evolutionary branches. Give examples of animals assigned to each branch.

Answer 23

Lophotrochozoa: platyhelminths, nemerteans, mollusks, annelids, lophophorate phyla, rotifers
Ecdysozoa: nematodes (roundworms) and arthropods

Question 24

What are the distinguishing characteristics of phylum Nemertea and phylum Platyhelminthes?

Answer 24

Phylum Platyhelminthes: Acoelomate animals with bilateral symmetry, cephalization, 3 definite tissue layers, and well-developed organs. Many are hermaphrodites single animal produces both sperm and eggs. Ladder-type nervous system: sense organs, simple brain composed of two ganglia, and 2 nerve cords that extend the length of body. Protonephridia: function in osmoregulation and disposal of metabolic wastes.

Phylum Nemertea: Characterized by proboscis: muscular tube for capturing food, defense. Reduced coelom (rhynchocoel) space surrounding proboscis. Nemerteans have tube-within-a-tube body plan, complete digestive tract with mouth and anus, and a circulatory system.

Question 25

Describe the main classes of phylum Platyhelminthes, giving examples of animals that belong to each class.

Answer 25

Class Turbellaria: free-living flatworms, including planarians
Classes Trematoda and Monogenea: parasitic flukes
Class Cestoda: parasitic tapeworms

Question 26

Explain parasitic flukes and tapeworms.

Answer 26

Typically have suckers or hooks for holding on to their hosts.
Have complicated life cycles, intermediate hosts, and large numbers of eggs.

Question 27

What are the adaptive advantages of cephalization?

Answer 27

Evolution of a head: concentration of sense organs and nerve cells (simple brain) at anterior end
(Flatworms show beginnings of cephalization)
Increases effectiveness of bilateral animal to actively find food, shelter, mates and to detect enemies.

Question 28

What are the distinguishing characteristics of phylum Mollusca?

Answer 28

Soft-bodied animals usually covered by a shell.
Ventral foot for locomotion.
Mantle covers visceral mass (body organs).
Most have open circulatory system. Cephalopods have closed circulatory system.
Most have rasplike radula for feeding. Bivalves are suspension feeders.
Most marine mollusks have free-swimming, ciliated trochophore larva.
The most biologically successful protostomes in terms of diversity and numbers are the mollusks and the arthropods.

Question 29

What are the distinguishing characteristics of phylum Mollusca four molluscan classes discussed?

Answer 29

Class Polyplacophora: Includes marine chitons. Shells consist of 8 overlapping plates.

Class Gastropoda: Largest group of mollusks (snails, slugs, and their relatives). Body undergoes torsion, a twisting of the visceral mass (all organs) that occurs in larval stage; synapomorphy for the group.

Class Bivalvia: Includes aquatic clams, scallops, oysters. Two-part shell hinged dorsally and encloses bodies. Suspension feeders.

Class Cephalopoda: Includes squids, octopods, Nautilus. Active, predatory swimmers. Tentacles surround the mouth, located in the large head.

Question 30

What are the distinguishing characteristics of phylum Annelida and the three annelid classes discussed?

Answer 30

Aquatic worms, earthworms, leeches.
Conspicuously long bodies.
Segmentation both internally and externally.
Large, compartmentalized coelom serves as hydrostatic skeleton.
Class Polychaeta
Class Oligochaeta
Class Hirudinea

Question 31

What are the distinguishing characteristics of the lophophorate phyla?

Answer 31

Marine animals with a lophophore: brachiopods, phoronids, bryozoans
Lophophore: ciliated ring of tentacles surround the mouth and specialized to capture particles in water.

Question 32

What are the distinguishing characteristics of phylum Nematoda?

Answer 32

Highly successful ecdysozoans
Pseudocoelom
Body covered by tough cuticle and helps prevent desiccation
Parasitic nematodes in humans: Ascaris, hookworms, trichina worms, pinworms

Question 33

What are the distinguishing characteristics of phylum Arthropoda?

Answer 33

Segmented animals with paired, jointed appendages.
Armor-like exoskeleton of chitin
Molting necessary for arthropod to grow
Open circulatory system: dorsal heart, pumps hemolymph
Aquatic forms have gills for gas exchange
Terrestrial forms have either tracheae or book lungs
The most biologically successful protostomes in terms of diversity and numbers are the mollusks and the arthropods.

Question 34

What adaptations have contributed to the biological success of insects?

Answer 34

Versatile exoskeleton
Segmentation
Specialized jointed appendages 
Highly developed sense organs
Ability to fly 
The remarkable biological success of the insects can be attributed to the evolution of complex body plans and life cycles, for example, their exoskeleton, segmentation, specialized jointed appendages, ability to fly, and metamorphosis.

Question 35

Explain deuterostomes.

Answer 35

Include echinoderms, hemichordates, chordates
Hemichordates (acorn worms): marine deuterostomes
three-part body (proboscis, collar, trunk)

Question 36

What are the shared derived characters of deuterostomes?

Answer 36

radial, indeterminate cleavage
blastopore becomes anus
larva have a loop-shaped ciliated band used for locomotion

Question 37

What are three shared derived characters of echinoderms?

Answer 37

Marine animals with spiny “skin”, water vascular system, tube feet, and endoskeleton.
Larvae exhibit bilateral symmetry
Most adults exhibit pentaradial symmetry

Question 38

Describe the main classes of echinoderms.

Answer 38

Class Crinoidea: (Sea lilies, feather stars) oral surface turned upward. Some crinoids are sessile.

Class Asteroidea: (Sea stars) central disc with five or more arms and use tube feet for locomotion.

Class Ophiuroidea: (Brittle stars) arms longer, more slender than sea stars, arms more distinct from central disc, use arms for locomotion, and tube feet lack suckers.

Class Echinoidea: (Sea urchins, sand dollars) lack arms, have a solid shell, and are covered with spines.

Class Holothuroidea: (Sea cucumbers) elongated flexible bodies and circle of modified tube feet surrounds mouth .

Question 39

What are five shared derived characters of chordates?

Answer 39

At some time during life cycle have:
flexible, supporting notochord
dorsal, tubular nerve cord 
pharyngeal (gill) slits
muscular postanal tail
endostyle (or thyroid gland)

Question 40

What are the subphylums of the phylum chordates?

Answer 40

Subphylum Urochordata
Subphylum Cephalochordata
Subphylum Vertebrata

Question 41

Explain vertebraes.

Answer 41

Vertebral column: chief skeletal axis of body
Cranium: braincase
Neural crest cells: determine development of many structures
Pronounced cephalization
Complex brain
Muscles attached to endoskeleton for movement

Question 42

What are four shared derived characters of vertebrates?

Answer 42

Shared derived characters of vertebrates include a vertebral column, cranium, neural crest cells, and an endoskeleton of cartilage or bone.