This document summarizes key characteristics of animals and describes experiments on invertebrates including sponges, cnidarians, flatworms, and parasitic worms. It discusses that animals are multicellular and heterotrophic, and most have digestive cavities. It also describes animal development including the zygote, blastula, and gastrula stages. Classification is based on characteristics like body plan, symmetry, germ layers, and presence of organs or tissues. Specific phyla discussed include Porifera, Cnidaria, Platyhelminthes, Trematoda, and Cestoda.

1. Experiment #6
Kingdom Animalia
Invertebrates

2. Introduction- Animals
• All animals are members of the Kingdom Animalia, also called
Metazoa.
• All members of Animalia are:
- multicellular
- heterotrophs.
• Most ingest food and digest it in an internal cavity.
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3. Introduction- Animals
• Animal cells lack the rigid cell walls that characterize plant cells.
• Most animals are capable of complex and relatively rapid movement
compared to other organisms.
• Most reproduce sexually, by means of differentiated eggs and sperm.
• Most animals are diploid.
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4. Introduction- Animals
• The development of most animals is characterized by distinctive
stages, including:
- a zygote, is the product of fertilization;
- a blastula, which is a hollow ball of cells formed by the
developing zygote;
- a gastrula, which is composed of three germ layers:
- ectoderm
- endoderm
- mesoderm.
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5. Animals- classification
• The classification of animals is based on:
• body plan
• Symmetry
• germ layers
• level of organization
• coelom (cavity lined by epithelium)
• segmentation.
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6. Animals- Body Plans
• A sac body plan: is one in which the
mouth is used as both an entrance for
nutrient molecules and an exit for waste
molecules.
• A tube-within-tube body plan: Animals
with a mouth and an anus have this body
plan. This plan allows specialization of
parts along the digestive canal to occur.
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7. Animals- Symmetry
• Radial symmetry means that any
longitudinal cut that passes through a
midpoint gives two equal halves.
• Bilaterally symmetrical animals can
be cut into right and left halves and
generally have well-developed head
regions.
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8. Animals- Number of Germ Layers
• During the embryological development, there may be only
two germ layer, ectoderm and endoderm; or three germ
layers, ectoderm, endoderm, and mesoderm.
• The presence of mesoderm is associated with the development of
internal organs associated with higher animals such as skeletons
and reproductive organs.
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10. Animals- Level of Organization
• Some animals do not have organs and instead have a tissue level of
organization.
• Most animals have the organ system level of organization.
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11. Animals- Coelom
• Is the body cavity in which
the internal organs are found.
• Acoelomates: are animals that
do not have a coelom.
• Pseudocoelomates: have a
body cavity incompletely lined
by mesoderm.
• True coelomates: have a body
cavity completely lined by
mesoderm.
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12. Animals- Segmentation
• When an animal is segmented, it has repeating parts like the
vertebrae in the human backbone. Segmentation has led to
specialization of parts in advanced animals.
• Cephalization, having a well-developed head, is also a characteristic
of the most advanced animals.
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13. Phylum Porifera (Sponges)
• The name stems from the meaning of ("pore bearers").
• are multicellular
• Still, they have a very simple grade of organization
• the body consists of a loose aggregation of cells embedded in a gelatinous
matrix.
• They lack any real organs or true tissues,
• Nonetheless, they do contain different types of cells.
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14. Sponges- Structure
• Cells include:
• epithelial-like cells called pinacocytes that cover the
exterior and non-flagellated interior surfaces
• flagellated cells called choanocytes that line inner
chambers and canals
• amoeboid cells called archeocytes that move about in the
mesohyl (the gelatinous matrix within a sponge).
• They can differentiate into other types of cells that form parts
of the skeleton
 composed of collagen and/or spongin fibers often
embedded with calcareous or siliceous crystalline spicules).
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16. • Sponges show radial symmetry or none.
• A spongocoel is the large, central cavity of sponges.
• Water enters the spongocoel through hundreds of tiny pores (Ostia)
• Water exits the spongocoel through the larger opening (osculum).
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17. Sponges: Ecology
• Most species are marine
• a few are found in freshwater.
• few animals appear to eat sponges, probably
because a mouth full of spongin and spicules is
not too appetizing!
• However, a few reef fish and the hawksbill turtle
feed exclusively on sponges.
• Sponges provide homes for many organisms,
particularly those anchored to coral reefs.
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18. Phylum Cnidaria
• Cnidarians are radially symmetrical animals that have a circle of
tentacles surrounding the mouth.
• Cnidarians are characterized by the presence of stinging cells called
cnidocytes that are used for the capture of prey and defense.
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19. • Cnidarians have two true tissue layers:
• an outer epidermis
• an inner gastrodermis.
• A connective tissue layer called the mesoglea separates the two tissue layers.
• The basic body plan includes a mouth that opens into a blind
gastrovascular cavity, which is lined with the gastrodermis.
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20. Cnidarians can be:
- Sessile polyps in which the
mouth points upwards
(hydra and sea anemones)
- swimming medusas in
which the mouth points
downwards (e.g., jellyfish)
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21. Phylum Platyhelminthes (Flatworms)
• Members of this phylum are bilaterally symmetrical and dorsoventrally
flattened.
• They have three embryonic body layers: ectoderm, mesoderm, and
endoderm.
• The gut is a gastrovascular cavity and has the functions of both digestion
and circulation;
• the mouth serves as both entrance and exit from the gut.
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22. • These animals are the simplest form of animal life to have organ systems, a
central nervous system, and a well-defined rostral or head end, with an
opposite caudal or tail end.
• Flatworms are acoelomate, i.e., the outside of the gut wall is directly
continuous with the mesoderm; there is no coelomic cavity and so the gut
is not free inside the body.
• The mesoderm is muscular and is used for movement.
• Ectodermal cells may be ciliated and provide another means of
locomotion.
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23. Flatworms- Classes
• Three classes of the phylum Platyhelminthes exist:
- class Turbellaria
- class Trematoda
- class Cestoda.
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24. Class Turbellaria
• Members of the class Turbellaria are free living (not parasitic).
• Planaria lives in fresh water ponds
• is a carnivore (animal eating).
• The diet consists of such foods as insect larvae, small crustaceans, and
other small living and dead animals.
• Planarians reproduce asexually and sexually; individuals have both ovaries
and testes. 24

25. • They glide over surfaces by the action of cilia; muscular contractions
wrinkle or bend the body.
• There is clearly a head end with a pair of black, light sensitive spots.
• The color of planaria would make them blend in and be invisible
among the leaves on the bottom of a pond.
• The gastrovascular cavity is highly branched, because it serves also
for circulation of nutrients to every cell.
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26. • A planarian cross section has
three or four slices through
them.
• Most obvious is the one from
the middle with the great
circular, muscular tube of the
pharynx;
• around it exists a space.
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27. • The gut is continuous with the cells of the surrounding mesoderm.
• the gut is lined with cells of endoderm
• the outside of the animal is covered with ciliated cells of ectoderm.
• The mesoderm is muscular.
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28. Class Trematoda
• Trematodes are commonly called flukes, and they are parasitic.
• The life cycles of parasites are complex, with intermediate hosts and
life stages.
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29. Liver flukes- Opisthorchis
• Opisthorchis is the liver fluke.
• The anterior end has a mouth at the end, a sucker disc for holding on; and
a ventral sucker, which is somewhat farther posterior.
• The intestine divides into two simple tubes near the head end.
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30. • The dark organ (colored) in the center of the body is the uterus and it
is filled with eggs; the ovary is just posterior to it and appears as a
pink mass.
• Flukes have a seminal receptacle at the posterior end. The branched
organ in the posterior part of the body is the testes.
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31. • Trematode life cycle: The liver fluke is an important human parasite
that is widely distributed in the Far East. Human infection occurs due
to eating raw fish.
• The small brown eggs of the fluke exit from a person's body in the
feces. The eggs hatch when they are eaten by certain kinds of fresh
water snails.
• The hatchling is called a miracidium; after several metamorphoses,
the parasite leaves the snail and infects fresh water fish; it encysts in
their flesh. 31

32. • When a person eats these fish uncooked or insufficiently cooked, the
live parasites enter the digestive system and migrate from the small
intestine via the bile duct to the liver.
• There they mature into adult liver flukes and in about 3 weeks begin
to produce eggs. Eggs return via the bile duct to the digestive system
and exit from the body in feces.
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34. Class Cestoda
• The Cestoda are parasitic tapeworms. The life cycles are complex.
• All tapeworms are extremely flat
• the body is divided into segments, and there is no digestive system.
• They absorb nutrients across their body walls.
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35. The scolex
• is the term for the head end of a tapeworm
• it has a disc of hooks at the tip, which anchor it into the lining of the
host's intestine, and four large suckers for holding on.
• New segments or proglottids are generated behind the scolex.
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36. • As you move down the worm away from the head, these segments
get larger. Each is a complete reproductive machine
with testes, ovaries and uterus.
• The figure below shows mature proglottids. You can see a branched
uterus containing hundreds of eggs in each segment.
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