Download Chapter 29 – Invertebrates

Animal Evolution and Invertebrates
Learning objectives
Parazoa
1.
From a diagram, identify the parts of a sponge (including the spongocoel, porocyte,
epidermis, choanocyte, mesohyl, amoebocyte, osculum, and spicule) and describe the
function of each.
Radiata
2.
List the characteristics of the phylum Cnidaria that distinguish it from the other
animal phyla.
3.
Describe the two basic body plans in Cnidaria and their role in Cnidarian life cycles.
4.
List the three classes of Cnidaria and distinguish among them based on life cycle and
morphological characteristics.
5.
List the characteristics of the phylum Ctenophora that distinguish it from the other
animal phyla.
Lophotrochozoa
6.
Distinguish between the following pairs: bilateria and urbilateria, acoelomates and
coelomates, protostomes and deuterostomes, and Lophotrochozoa and Ecdysozoa.
7.
List the characteristics of the phylum Platyhelminthes that distinguish it from the
other animal phyla.
8.
Distinguish among the four classes of Platyhelminthes and give examples of each.
9.
Describe the generalized life cycle of a trematode and give an example of one fluke
that parasitizes humans.
10. Describe the anatomy and generalized life cycle of a tapeworm.
11.
Describe unique features of rotifers that distinguish them from other
pseudocoelomates.
12. Define parthenogenesis and describe alternative forms of rotifer reproduction
13. Define lophophore and list three lophophorate phyla.
14. List the distinguishing characteristics of the phylum Nemertea.
15. Explain the relationship between proboscis worms and flatworms.
16. List the characteristics that distinguish the phylum Mollusca from the other animal
phyla.
17. Describe the basic body plan of a mollusk and explain how it has been modified in the
Bivalvia, Cephalopoda, Gastropoda, and Polyplacophora.
18. Distinguish among the following four molluscan classes and give examples of each:
a. Bivalvia
b. Cephalopoda
c. Gastropoda
d. Polyplacophora
19. List the characteristics that distinguish the phylum Annelida from the other animal
phyla.
20. Distinguish among the classes of Annelida and give examples of each.
21. Describe the adaptive advantage of a coelom and segmentation in annelids.
Ecdysozoa
22. List the characteristics of the phylum Nematoda that distinguish it from other
wormlike animals.
23. Give examples of both parasitic and free-living species of nematodes.
24. List the characteristics of arthropods that distinguish them from the other animal
phyla.
25. Describe advantages and disadvantages of an exoskeleton.
26. Distinguish between hemocoel and coelom.
27. Define and distinguish between the major independent arthropod lines of evolution
represented by:
a. Trilobita
b. Chelicerata
c. Crustacea
d. Uniramia
28. Describe the different views regarding the relationship between arthropods and
annelids.
29. Describe the basic mechanism for the development of segmented bodies.
30. Describe three hypotheses that can account for the scattered distribution of
segmentation in animals.
Deuterostomia
31. List the characteristics of echinoderms that distinguish them from other animal
phyla.
32. Distinguish among the five classes of echinoderms and give examples of each.
33. Explain why the phylum Chordata is included in a chapter on invertebrates.
34. Describe the evolutionary relationships between echinoderms and chordates.
Summary of Key Concepts
PARAZOA

Phylum Porifera: Sponges are sessile with porous bodies and choanocytes. Sponges
lack tissues and organs. They filter-feed by drawing water through pores;
choanocytes (flagellated collar cells) ingest bacteria and particulate food suspended
in the water.
RADIATA


Phylum Cnidaria: Cnidarians have radial symmetry, a gastrovascular cavity, and
cnidocytes. Cnidarians are mainly marine carnivores possessing tentacles armed with
cnidocytes that aid in defense and the capture of prey. Two body forms are sessile
polyps and floating medusas. The digestive tract (gastrovascular cavity) is
incomplete (has a single opening, the mouth, that also functions as an anus). Class
Hydrozoa usually alternates polyp and medusa forms, although the polyp is more
conspicuous. In class Scyphozoa, jellies (medusas) are the prevalent forms of the
life cycle. Class Anthozoa contains the sea anemones and corals, which occur only as
polyps.
Phylum Ctenophora: Comb jellies possess rows of ciliary plates and adhesive
colloblasts. Comb jellies use retractable tentacles to capture food.
PROTOSTOMIA: LOPHOTROCHOZOA





Phylum Platyhelminthes: Flatworms are acoelomates with gastrovascular cavities.
Most flatworms are ribbonlike animals with a gastrovascular cavity. Class Turbellaria
is made up of mostly free-living, primarily marine species. Members of the classes
Trematoda and Monogenea live as parasites in or on animals. Class Cestoidea
(tapeworms), all parasites, lack a digestive tract.
Phylum Rotifera: Rotifers are pseudocoelomates with jaws, crowns of cilia, and
complete digestive tracts. Found mainly in fresh water, many rotifer species are
parthenogenetic.
The lophophorate phyla: Bryozoans, phoronids, and brachiopods are coelomates with
ciliated tentacles around their mouths. The lophophore is a horseshoe-shaped,
suspension-feeding organ bearing ciliated tentacles.
Phylum Nemertea: Proboscis worms are named for their preycapturing apparatus.
The proboscis worms have a unique retractable tube (proboscis) used for defense
and prey capture. A fluid-filled cavity surrounds the proboscis.
Phylum Mollusca: Mollusks have a muscular foot, a visceral mass, and a mantle. Class
Polyplacophora is composed of the chitons, oval-shaped marine animals encased in an
armor of dorsal plates. Most members of class Gastropoda, the snails and their
relatives, possess a single, spiraled shell; sea slugs lack a shell; embryonic torsion of
the body is a distinctive characteristic. Class Bivalvia (clams and their relatives)
have hinged shells divided into two halves. Class Cephalopoda includes squids and

octopuses, carnivores with beaklike jaws surrounded by tentacles of the modified
foot.
Phylum Annelida: Annelids are segmented worms. Class Oligochaeta includes
earthworms and various aquatic species. Members of class Polychaeta possess
paddlelike parapodia that function as gills and aid in locomotion. Class Hirudinea
consists of the leeches.
PROTOSTOMIA: ECDYSOZOA


Phylum Nematoda: Roundworms are nonsegmented pseudocoelomates covered by
tough cuticles. Among the most widespread and numerous animals, nematodes
inhabit most aquatic habitats. Some species are important parasites of animals and
plants.
Arthropods are segmented coelomates with exoskeletons and jointed appendages.
There are more known species of arthropods than all other phyla combined.
Chelicerates, arthropods with pincer or fanglike feeding appendages, include class
Arachnida (spiders, ticks, scorpions, and mites). A traditional classification scheme
groups the insects (class Insecta), centipedes (class Chilopoda), and millipedes (class
Diplopoda) as uniramians--all with one pair of antennae and unbranched (uniramous)
appendages. Crustaceans (lobsters, crayfish, crabs, shrimps, and barnacles) are
primarily aquatic arthropods with two pairs of antennae and branched appendages.
Research on the origin of segmentation in arthropods and other phyla of segmented
animals will help systematists test hypotheses about phylogeny.
DEUTEROSTOMIA

Phylum Echinodermata: Echinoderms have a water vascular system and secondary
radial anatomy. Sea stars and their relatives make up six classes of the marine
phylum Echinodermata. The radial anatomy of many species evolved secondarily from
bilateral ancestors. The vascular system ending in tube feet is used for locomotion
and feeding. A thin, bumpy, or spiny skin covers a calcareous endoskeleton.
Phylum Chordata: The chordates include two invertebrate subphyla and all
vertebrates. Chordates share many features of embryonic development with the
echinoderms.
Key Terms
ammonites
amoebocyte
antennae
Arthropoda
arthropods
book lungs
bilateral symmetry
blastula
brachiopod
bryozoan
cephalization
chelicerae
chelicerates
choanocyte
class Arachnida
class Chilopoda
cleavage
class Diplopoda
class Insecta
closed circulatory system
cnidocytes
coelom
colloblasts
complete digestive tract
complete metamorphosis
compound eye
copepods
crustacean
cuticle
decapod
echinoderms
ectoderm
endoderm
entomology
eurypterid
exoskeleton
foot
gastrovascular cavity
gatrula
gastrulation
hermaphrodite
incomplete metamorphosis
invertebrates
isopods
lophophorate animals
lophophore
malpighian tubule
mandibles
mantle cavity
mantle
medusa
mesoderm
mesohyl
metanephridium
metamorphosis
molting
nematocysts
open circulatory system
osculum
parthenogenesis
phoronids
phylum Chelicerata
phylum Crustacea
phylum Trilobita
phylum Uniramia
planarians
polyp
psuedocoelom
radula
radial symmetry
spongocoel
torsion
tracheal system
trilobites
trochophore
tube feet
uniramians
urbilateria
visceral mass
water vascular system
QUESTIONS – Reading Chapter 18 and provided lab materials will help!
1.
What are bilateral symmetry and cephalization?
2.
Draw a phylogenetic tree for animals showing sponges, cnidarians, flatworms,
nematodes, molluscs, annelids, arthropods, echinoderms and chordates.
3.
Explain how the animal kingdom is divided on the basis of symmetry, body cavities,
and embryology; list the major phyla within each major subdivision.
4.
Discuss the advantages of bilateral symmetry over radial symmetry.
5.
Describe the differences between the protostomes and the deuterostomes. (Check
out the chart on page 369).
6.
Describe main characteristics of the Porifera (sponges).
7.
Describe the distinguishing characteristics of the Cnidaria (focus in on
gastrovascular cavity).
8.
Describe the major characteristics of the Platyhelminthes.
9.
Describe the tapeworm's special adaptation for parasitism.
10.
List the identifying features of the nematodes and discuss the economic importance
of this phylum.
11.
Why are the annelids, arthropods and molluscs thought to be closely related?
12.
Describe the body plan common to all Mollusca, and indicate the modifications it
exhibits in the Gastropoda (snails), Bivalvia (bivalves), and Cephalopoda (squids and
octopuses).
13.
Describe the distinguishing characteristics of the Annelidia, and compare the
polychaetes, the earthworms, and the leeches with respect to the presence or
absence of a distinct head, the degree of segmentation, the presence or absence of
parapodia, and the presence of setae, or bristles.
14.
Describe the distinguishing characteristics of the arthropods.
15.
Describe the distinguishing characteristics of the Crustacea, Chilopoda, Diplopoda,
Insecta, and Arachnida. List representative examples of each.
16.
Briefly describe the structure of the generalized insect body. (Figure 18.12B)
17.
Contrast complete and incomplete metamorphosis.
18.
Name the two major phyla of the Deuterostomia, and list representative examples
of each.
19.
Describe the distinguishing characteristics of the echinoderms, and list a
representative example of each class.
20.
What four features distinguish Chordata.