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BIOLOGY FOR CLASS IX
Class IX
INVERTEBRATA
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Invertebrates
Phylum Protozoa
Phylum Porifera
Phylum Coelenterata
Phylum Platyhelminthes
Phylum Nematoda
Phylum Annelida
Phylum Arthropoda
Phylum Mullusca
Phylum Echinodermata
 Invertebrates
are animals that do not have a
backbone. Invertebrates are cold-blooded;
their body temperature depends on the
temperature of their environment.
 Some major groups of invertebrates
include:
Protozoans - Very primitive, simple animals
like amoebas, jellyfish, corals, tapeworms,
insects, arachnids, crustaceans, mollusks,
echinoderms, etc
1.
2.
3.
4.
5.
Phylum Protozoa
Heterotrophic or autotrophic
Most motile
Eukaryotes
Unicellular
Movement
1. Flagellates(chlamydomonas)
2. Ciliates(paramecium)
3. Pseudopodia (Amoeba)
 Protozoans
hunt, digest and store food.
Most are heterotrophs. They feed on other
animals to obtain the nutrients they need
to live.
 Waste
materials in protozoan are removed
from the cell by diffusion through the
cell. They are transported out of the cell
by food vacuoles that come in contact with
the surface. This is known as exocytosis.
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Respiration takes place when oxygen
diffuses into the cell, where the food
molecules become oxidized. The energy
produced and the organic molecules are
used for maintenance and building of the
cell. Waste products ,carbon dioxide and
water diffuse out of the cell.
Binary fission, asexual reproduction by a
separation of the body into two new bodies. In
the process of binary fission, an organism
duplicates
its
genetic
material,
or
deoxyribonucleic acid (DNA), and then divides
into two parts (cytokinesis), with each new
organism receiving one copy of DNA.
 In protists, binary fission is often differentiated
into types, such as transverse or longitudinal,
depending on the axis of cell separation.
 Asexual reproduction of protozoans occurs when
the cell divides in half by binary fission. Some
which are parasites multiply within the host.
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Phylum Porifera - Sponges
• Mostly
marine, but include some freshwater inhabitants;
usually found attached to the substratum in shallow or
deep water.
• They are sessile; permanently attached to the substrate
• Obtain their food by filter feeding
General Morphology
• The internal cavity is called the atrium or spongocoel
• Water is drawn into it through a series of incurrent pores or dermal ostia present in the body
wall into a central cavity and then flows out of the sponge through a large opening at the top
called the osculum
The Skeleton
In the mesohyl is the skeleton composed of tiny pointed structures made of silica or calcium
carbonate called spicules.
These structures act as an internal scaffolding, but also function in protection
Among some sponges the skeleton consist of spongin fibers made of collagenous material;
found in many of the commercial sponges
Types of Sponges (Canal
Systems)
A. Asconoid Sponges
• Simple vaselike structure
• This stucture puts limitations on size; (increase in
volume without a corresponding increase in the surface
area of the choanocytes)
Sponge Reproduction
• Most
are hermaphroditic or monoecious.
• Sperm leaves a sponge via the osculum, and enters a sponge by the currents
generated from the choanocytes.
Fertilized eggs develop into ciliated free-swimming larvae called
parenchymula larvae
• Sponges can reproduce asexually by fragmentation
• Many of the freshwater sponges
can produce asexual bodies called
gemmules, aggregations of cells
that are enclosed in hard outer
covering containing spicules
Sponge Taxonomy
Class Calcarea (Calcispongidae)
• Only sponges that possess spicules
composed of calcium carbonate.
• Spicules are straight or have 3-4 rays,
and do not have hollow axial canals.
• Today, their diversity is greatest in the
tropics, predominantly in shallow waters
Class Hexactinellida (Hyalospongiae)
• Glass sponges; characterized by siliceous
spicules consisting of six rays intersecting
at right angles
• Widely viewed as an early branch within
the Porifera
Class Demospongiae
• Greater than 90 percent of the 5,000 known
living sponge species are demosponges.
• Demosponge skeletons are composed of
spongin fibers and/or siliceous spicules
• Siliceous spicules with one to four rays not
at right angles,
All members express the leuconoid body
form
Yellow sponge growing on a wall
on a Caribbean reef.
The “simplest” of the complex
animals . . .
Sea
Anemone
Jellyfish
Hydras
Sea Coral
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Over 10,000 living species
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Both marine and
freshwater
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Hydras in FW
Corals, jellyfish, and
anemones in marine
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Radial symmetry
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Tissue level of
organization
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Two general body forms
exhibited
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POLYP
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MEDUSA
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Polyp Form
Medusa Form
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Sessile
Cylindrical body
Ring of tentacles on
oral surface
Flattened, mouth-down
version of polyp
Free-swimming
Show the same internal
structure
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Basic body plan of
ALL cnidarians
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Sac with a central
digestive
compartment (GVC)
Single opening serving
as both mouth and
anus
Ring of tentacles on
oral surface
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All cnidarians are carnivores
Tentacles capture and push
food into mouth
Tentacles are armed with
stinging cells
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Cnidoblasts / cnidocytes
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Contain stinging capsules
called nematocysts
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The tentacle is
stimulated
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Nematocyst is
discharged
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Pressure on “trigger”
Thread uncoils
Entangles prey
Some species produce
toxins
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Injects toxin into prey,
paralyzing it!
Cnidocytes cover the length of tentacles
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Food is forced into the
GVC
Extracellular digestion
begins
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Enzymes secreted into
GVC
Intracellular digestion
completes process
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Partially digested food
engulfed by endoderm
cells
 First
true nerve
cells in K. Anamalia
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Nerve net sends
impulses in all
directions
Cells of epidermis
and gastrodermis
arranged into
contractile fibers
 Do
not have a
brain to receive
information!
 Varies among forms
 Hydras, anemones and
corals
 exist only in polyp form
 Asexual reproduction
(conditions good)
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Sexual reproduction
(conditions unfavorable)
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Budding in Hydra
Budding
Zygotes remain dormant
until conditions improve
 Some
colonial polyp
forms have a medusa
phase in their life
cycle
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Specialized
reproductive polyps
produce tiny medusas
by asexual budding
Sexual reproduction by
medusas produce
ciliated larva
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planula
Planula settles and
develops into new polyp
Medusa and polyp
stages
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Separate sexes produce
gametes
Fertilization occurs in GVC
of female
Planula develops and is
free-swimming
Planula settles, develops
into polyp
Polyp produces new
medusas by budding
*Fig. 32-8, PG 690
The cnidarians may be a relatively small group
comprising the Animal Kingdom, but they play
a major role in any marine habitat.
General Characteristics
• They exhibit bilateral symmetry: anterior and
posterior ends are different; so are the dorsal (top) and
ventral (bottom) surfaces
• The platyhelminths also exhibit some degree of
cephalization Commonly referred to as the 'flatworms'
because their bodies are dorsoventrally flattened.
• They are acoelomates
• This phylum (and all remaining phyla) possess 3
germ layers (=triploblastic)
• The mesoderm (third germ layer) gives rise to
muscles, various organ systems, and the parenchyma,
a form of solid tissue containing cells and fibers
Outer Body Covering
• The body of some platyhelminthes (e.g.,
turbellarians) is covered by a ciliated epidermis
• Epidermal cells contain rod-shaped structures
called rhabdites that when released into the
surrounding water, expand and form a protective
mucous coat around the animal
• The outer body covering of other
platyhelminthes (e.g., parasitic forms) is a nonciliated tegument
• The tegument is referred to as a syncytial
epithelium
Organ Systems of the Platyhelminthes
Digestive System
• Some of the flatworms possess a digestive system, with a mouth, pharynx, and a
branching intestine from which the nutrients are absorbed
• The intestine, with only one opening, is a blind system
Excretory System (osmoregulation)
• A network of water collecting tubules adjacent to flame cells or a protonephridia
• When cilia beat they move water into the tubules and out the body through pores
called nephridiopores
Organ Systems of the Platyhelminthes con’t
Muscular System
• Below the epidermis are layers of circular and
longitudinal muscle fibers; used in locomotion
Nervous System
• Includes: anterior cerebral ganglia,
longitudinal nerve cords, and some lateral
nerves
• Most free living planarians and parasitic larval
forms possess a variety of sensory organs (e.g.,
eye spots, statocysts, rheoreceptors)
Reproductive System
• Most are capable of some form of
asexual reproduction (e.g., many
turbellarians reproduce by fission)
• Most flatworms are
hermaphroditic; however, they
often pair with other individuals to
exchange gametes
Class Turbellaria
• Free-living flatworms; mostly marine organisms
• Range in size from microscopic (interstitial species between sand grains) to extremely
large (two feet)
Locomotion
• Most move by means of cilia and
mucous
• Muscle contractions also permit
turning, twisting and folding of the
body
Class Turbellaria con’t
Nutrition
• Turbellarians are carnivores and prey on other animals or eat dead animal remains.
• Planarians have a muscular pharynx that they can insert into their prey and then pump to
bring in food fragments
• These animals have a highly divided gut to greatly increase the surface area for digestion
and absorption
Senses
• They have well developed sensory structures, including eyespots, mechanoreceptors, and
chemoreceptors
Class Turbellaria con’t
Reproduction
• Planarians are capable of asexual reproduction
via fission
• Also capable of regeneration; exhibit both
anterior- posterior and lateral polarity
• They are hermaphrodites but usually exhibit
cross-fertilization
• The penis of some turbellarians is modified as a
hollow stylet; sperm tranfer is by hypodermic
impregnation, in which the copulating partners
stab each other and inject sperm
•Over 80000 species
•Cylindrical pseudocoeloemates
•Have effective hydroskeleton and musculature
•Inhabit aquatic areas. Most are parasitic.
•Most reproduce sexually. Females can produce ~100,000 eggs a
day.
•Tricininella spiralis causes trichinosis in humans from under
cooked pork
•Parasite burrows into muscle tissue forming cysts
•Hookworms and pinworms can parasitize digestive systems
•Others cause heartworm and elephantiasis
Roundworm
Hookworm
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Similar to flat worms
Inclide proboscus worms
Acoelomate, but have functioning digestive tract
Also have a funtioning blood vascular system
•Have an anterior prostomium and posterior pygidium; both
nonsegmented
• Body is divided into a linear series of similar parts or segments, and
each segment is called a metamere
• The pattern of repeated segmentation is called metamerism
• Each metamere is separated from the next by a transverse septum
• Each metamere acts as a hydrostatic skeleton
• Each metamere has longitudinal and circular muscles; longitudinal
muscle contraction causes segments to shorten; circular muscle
contraction causes segments to elongate
• Each segment usually bears one or more chitinous bristles called setae;
help anchor segments
Nervous System
• Consists of a brain, which is connected to
a pair of ventral longitudinal nerve cords,
with a ganglion in each segment
(metameric)
Circulatory System
• Closed circulatory system, in which the blood is
always enclosed within blood vessels that run the
length of the body and branch to every segment
• Several hearts (5 in earthworms) are used to
pump blood through the closed circuit
Excretory System
• Consists of paired (metameric) metanephridia
• Excretory tubes with ciliated funnels that remove
waste from the coelomic fluid; open to the outside via
excretory pores.
Note:
Not all organ systems are metameric
For example, the digestive system extends the
length of the organism and is differentiated
along its length
Reproductive System
• Most annelids are hermaphroditic, but they are usually cross fertilizers.
• Earthworms and leeches form pairs and reciprocally fertilize one another
• Some annelids (e.g. marine sandworms) are dioecious and they release eggs and sperm into
the marine environment, where gametes unite to form trochophore larvae
Polychaetes: General Characteristics cont.
•Prostomium is well equipped with sensory and feeding structures
Polychaetes: General Characteristics cont.
• Mouth is located just below the prostomium,
but in front of the modified segments peristomium
• Digestive system includes a muscular
pharynx that can be everted through the
mouth
• Pharynx is equipped with pincer-like jaws
• Although many of the smaller polychaetes lack respiratory structures, the larger one
do possess gills
• Gills are usually modifications of the parapodia
Class Polychaeta: Diversity cont.
• Chaetopterus is tube dweller; lives in a U-shaped tube
• Parapodia are highly modified into 3 fan-like structures that bring water
into the tube
• The notopodium secretes a mucous bag that traps food from the water
flowing through the tube; the bag is periodically passed anteriorly toward
the mouth
Class Polychaeta: Diversity cont.
• Arenicola lives in a J-shaped burrow
• It employs peristaltic movements to generate a water flow
• Food is filtered out from the front of the burrow
Class Oligochaeta cont.
• Earthworms feed on vast quantities of soil that contains living and decaying organic material.
• Digestive tract of the annelids shows specialization along its length: mouth, pharynx, crop
(food storage), gizzard (grinding), calciferous glands (accessory glands that excrete excess
calcium from the food)
• Remainder of the gut is the intestine - for digestion and absorption
• Its surface area is increased because of a dorsal longitudinal fold called the typhlosole
Class Hirudinea cont.
• Leeches
crawl over the surface in a loop like fashion,
with the use of 2 suckers.
• Body is extended due to circular muscle contraction and
the attachment of the anterior sucker to the substrate.
• Posterior sucker is subsequently released, and
longitudinal muscles contract bringing the posterior part of
the body forward.
Class Hirudinea con’t
• Most leeches are active predators; however, some are the parasitic, bloodsucking forms.
• Blood suckers have blade like jaws that they use to penetrate the skin of a host.
• Blood is prevented from
clotting because they secrete a
powerful anticoagulant;
anesthetics are also released
• A muscular pharynx
subsequently pumps blood into
the gut.
 Metamerism-
body is segmented.
Exoskeleton and metamerism causes
molting
 Exoskeleton-
body covered with a hard
external skeleton
 Why an exoskeleton?
 Why not bones? Exoskeleton good for small
things, protects body from damage (rainfall,
falling, etc.).
 Bones better for large things
 Bilateral
Symmetry- body can be divided
into two identical halves
 Jointed
Appendages- each segment may
have one pair of appendages, such as:
 legs
 wings
 mouthparts
 Open
Circulatory System- blood washes over
organs and is not entirely closed by blood
vessels. Our system is a closed one
 Ventral
Nerve Cord- one nerve cord, similar
to our spinal column
Introduction
• Includes
animals such as squids, snails, oysters, clams and slugs.
• Most are marine, but many are freshwater and some live on the
land
• Despite the diversity of form and function among the molluscs, all
members of this group have the same basic body plan.
• This is often indicated by presenting a hypothetical ancestral
mollusc (HAM)
• HAM is hypothetical primitive ancestor that has characteristics that
appear among most members of the mollusca
A Closer look at HAM
The foot - a broad, flat muscular organ that is adapted for locomotion and attachment
The visceral mass - contains the internal organs
The mantle - a fold of tissue that drapes over the visceral mass; space between the mantle
and the visceral mass is called the mantle cavity
The Shell
• The
mantle is responsible for secreting the shell.
• The shell is comprised of three layers:
• The outside of the shell is covered by an organic layer periostracum
• The middle prismatic layer is characterized by densely packed
prisms of calcium carbonate laid down in a protein matrix
• The inner nacreous layer is
composed of calcium carbonate
sheets laid down over a thin
layer of protein
Gills
• The gills of HAM are often indicated as one or more pairs of bipectinate gills, flattened filaments attached to a longitudinal axis on either side
The Radula
• The mouth cavity of HAM possesses a specialized rasping organ called the radula; sits on a
cartilaginous structure - odontophore
• Particles of food brought into the mouth are bound in mucous secreted by the salivary glands
Other Features of HAM
• Nervous system consists of a nerve ring and 2 longitudinal nerve cords
• Coelom is reduced
• Open circulatory system
• The excretory organs of the
molluscs are
metanephridia; inner ends
open into the coelom via a
ciliated funnel called the
nephrostome; wastes leave
the body via the
nephridiopore
Molluscan Larval Stages
• Most molluscs produce a free-swimming ciliated
larvae called the trochophore larvae
• In some molluscs the trochophore develops into the
adult, but in other molluscs (e.g., gastropods) there is a
second larval stage called the veliger
General Characteristics
• Adults
exhibit pentamerous radial symmetry
• Radially symmetry is secondary; larvae are bilaterally symmetrical and
undergo metamorphosis to become radially symmetrical adults.
Echinoderm larva
General Characteristics cont.
•Poorly ganglionated; possess few sensory structures
• Body wall contains an endoskeleton of calcareous plates - ossicles
General Characteristics cont.
• Possess a network of canals throughout the body - water vascular
system.
• The canals are connected to extensions called tube feet (=podia),
located on the oral surface
• The water vascular system is important for locomotion, feeding, and
gas exchange.
• Sexes are separate; gametes shed into the water; fertilization is external
Class Asteroidea
• Typically have 5 arms which merge with a central disc
• Mouth is located in the center of oral surface which is directed downward
Water Vascular System
• On the aboral surface is the opening of the water vascular system the madreporite (=sieve
plate)
• Water enters the madreporite and goes through the stone canal canal to the ring canal
• Water then passes through a radial canal extending into each arm
• All along the length of these canals are lateral canals that terminate in a bulb-like structures
called ampullae equipped with tube feet
• Tube feet line the grooves on the oral surface - ambulacral grooves
How the Podia Operate
• Ampulla contract and force fluid into the podia causing it to become extended
• Suckers at the tips of the podia come into contact with the substrate and adhere to the
surface
• Then the podia contract, thereby forcing water back into the ampulla, and the body is
pulled forward
Nutrition
• Mouth leads to a 2-part stomach: a
large cardiac stomach and a smaller
pyloric stomach
• The pyloric stomach connects with
digestive glands (=pyloric cecae) that
runs into each arm
• A short intestine extends from from the pyloric stomach to an anus on the aboral surface
• Associated with the intestine are rectal cecae that pump the fecal wastes out of the anus
Additional Characteristics
• The endoskelton is made up of calcareous plates that often penetrate the dermis as spines
• Between the spines and plates are projections called papulae, which function in gas exchange
and excretion
• Other projections on the body wall include tiny jaw-like appendages called pedicellaria
Class Echinoidea
• Lack arms
• Body is enclosed in a shell or test
• Body surface is usually covered with moveable spines
Sea Urchins
• Spherical body
• Ambulacral plates bearing tube feet that
radiate out toward the aboral surface
• Use podia and spines during locomotion
• The spines are moveable and articulate with
the with the calcareous ossicles
• Sea urchins generally feed by scraping algae off of rocks
• Accomplished via a complex chewing apparatus called Aristotle's lantern
Class Holothuroidea
• Lack arms
• Oral-aboral axis is greatly extended
• Endoskeleton is reduced to a few ossicles scattered over
the surface of the animal making them rather soft bodied
• Some species crawl along the substrate using podia;
others have peristaltic locomotion via muscle contractions
Dermal ossicles
• At the oral end of the body are a group of tentacles (modified podia) that surround the
mouth; used in feeding
• Have a muscular cloaca that is partly used in gas exchange
• The actual gas exchange structures are branching structures called respiratory trees
Class Crinoidea
• Most primitive of the echinoderms
• Unusual in that the oral surface is directed
upward
• Aboral surface is attached to the substrate by
means of a bendable stalk
• The portion of the crinoid body attached to the
stalk is called the crown; bears a number of arms
• Along the length of the arms are branches called
pinnules
• The arms and the pinnules have ambulacral
grooves with suckerless podia (secrete mucus)
• The ambulacral grooves are heavily ciliated and
the cilia is used to direct food to the mouth
(=filter feeding)