Move System Reviewer: Phylum
Protozoa/ Protista and Porifera
Protozoa/Protista
Protozoa are economically important parasites
which live in or upon the bodies of other animals
or plants. Every species has a definite form and
the size of the individuals vary within definite,
usually narrow, limits.
→ They possess a single nucleus, if is
spherical.
→ Contractile vacuoles, food and stationary
vacuoles containing fluid may be present
in the bodies of protozoa.
→ Phylum protozoa are heterogeneous
assemblage of some 50,000 cellular or
single- cell organism found worldwide in
most habitats.
→ Protozoa means ‘first animal’ the
simplest form of animal life.
→ Protozoa are unicellular microorganisms
(eukaryotes) that lack cell walls.
→ They are found in marine habitat or soil,
in fresh water bodies, symbiotic, some
forms are parasites in other organisms.
→ Protozoa
depends
on
nutrition,
temperature, pH, and some depends on
sunlight.
Locomotory Organ
1. Cilia
➢ tiny hair-like appendages
➢ The term ‘cilia’ is a Latin term
meaning eyelash indicating the
tiny eyelash-like appearance.
2. Pseudopod
➢ from the Greek words pseudes
and podos, meaning “false” and
“feet” respectively.
➢ These projections extend and
contract.
➢ For locomotion and capture of
prey.
3. Flagellum
➢ The word “flagellum” means
“whip”.
➢ a whip-like appearance that
helps to propel a cell through the
liquid
The different protozoans commonly seen in
hay infusion:
1. Ciliophora
➢ Moves with cilia
➢ Paramecium
2. Mastigophora
➢ Moves with flagellum
➢ Euglena
3. Sarcodina
➢ Moves with pseudopods
➢ Amoeba
4. Chilomonas
➢ Has 2 flagella
Parts of a protozoan
Economic importance of Protozoans:
Divided into two:
1. Beneficial Protozoa
2. Harmful Protozoa
Beneficial Protozoa
1. Food
➢ Provide food for insect larvae,
crustaceans and worms, which
are taken by large animals like
fishes, lobsters, clams, and crabs,
which are eaten by man. Thus,
they form sources of food supply
to man both directly and
indirectly.
2. Symbiotic Protozoa
➢ live in the gut of termite, which
help in the digestion of cellulose.
The digested cellulose is utilized
by the host.
➢
3. Insect Control
➢ control harmful insects by
persisting their bodies.
4. Helpful Sanitation
➢ living in polluted water feed
upon waste organic matters and
thus purify it. Many protozoa
feed upon bacteria and play
important role in the sanitary
betterment and keeping water
safe for drinking.
5. Industry
➢ The skeletal deposits of marine
protozoa (Foraminifera and
Radiolaria) from oceanic ooze at
the sea-bottom. About 30% of
oceanic bed is covered with the
Globigerina ooze. These skeletal
deposits are put to many uses.
Some are employed as filtering
agents; others are made into
chalk and still others are used for
abrasives.
6. Building Material
➢ The skeletal deposits in due
course of time change into the
limestone rock. Limestone is
provided by the Globigerina
ooze, such as that of cliffs of
Dover, which have played an
important role in the defense of
England.
7. Oil Exploration
➢ Petroleum is organic origin. The
skeletal deposit of Foraminifera
and Radiolaria are often found in
association with oil deposits.
8. Scientific Study
➢ Many protozoa are used in
biological
and
medical
researches.
A
Holotricha.
Tetrachymena geleii is used in
nutritional research. The effects
of various foods and poison have
been investigated on this
protozoan.
Harmful Protozoa
1. Pollution of Water
➢ Drinking water in natural
condition is made unpalatable by
2.
3.
4.
5.
the reproduction of some freeliving protozoa in it
Destruction of Animals of Food Value
➢ dinoflagellates like Noctiluca
and Gonyaulax, when become
abundant, are responsible for
turning the ocean red. The water
becomes foul and cause toxic
reaction to molluscs like clam
oysters and mussels and they
become unfit for eating by
human beings.
Destruction of Wooden Articles
➢ Some
flagellater
like
Trichonympha and Colonympha
live in the gut of termites and
help in the process of cellulose
digestion. In the absence of these
flagellates the termites will die or
change their diet. Thus such
protozoa indirectly help in
distraction of wooden articles
and books.
Reduction in Fertility of Soil
➢ These protozoa feed on nitrogenfixing bacteria thus reduce the
fertility of soil.
Parasitic Protozoa
➢ Ectoparasites - when the
parasite lives on the external
surface of the host.
➢ EndoparasitesWhen
the
parasite lives inside the body of
the host
a. Coelozoic
i.
When
the
parasite lives in
the alimentary
canal or cavities
of host body.
ii.
Histozok
• Which
occupie
s space
betwee
n
the
iii.
host
cells.
Cytozoic
• These
live
inside
the
host’s
cell.
Porifera
Porifera are also known as “sponges”.
They are primitive, sessile, mostly marine, water
dwelling filter feeders that pump water through
their bodies to filter out particles of food matter.
→ With no true tissues (parazoa),
they lack muscles, nerves and
internal organs.
→ Their similarity to colonial
choanoflagellates
shows
probable evolutionary jump from
unicellular to multicellular
organisms.
→ They are both asexual and
sexual. Their skeleton is made up
of collagen and spicules.
→ Porifera are unidirectional driven
by flagella. They have cellular
level organization.
→ Different cells perform different
functions.
Representative
1. Class Calcarea
➢ They are characterized by
spicules made of calcium
carbonate in the form of calcite
or aragonite. While the spicules
in most species have three
points, in some species they have
either two or four points.
2. Class Hexactnellida
➢ are sponges with a skeleton made
of four- and/or six-pointed
siliceous spicules, often referred
to as glass sponges.
3. Class Demospongiae
➢ They are sponges with a soft
body that covers a hard, often
massive skeleton made of
calcium
carbonate,
either
aragonite or calcite.
➢ They
are
predominantly
leuconoid in structure.
➢ Their "skeletons" are made of
spicules consisting of fibers of
the protein spongin, the mineral
silica, or both.
➢ Where spicules of silica are
present, they have a different
shape from those in the
otherwise similar glass sponges.
Some parts of a Sponge:
1. Spongocoel
→ Large central cavity of Sponges.
→ Water enters the spongocoel
through hundreds of tiny pores
called OSTIA and exits through
a
larger
opening
called
OSCULUM.
→ Depending on the body plan of
the sponge, the spongocoel could
be a simple interior space of the
sponge or a complexly branched
inner structure.
→ Regardless of body plan or class,
the spongocoel is lined with
choanocytes, which have flagella
that push water through the
spongocoel, creating a current.
The spongocoel is lined by a variety of cell
types, each having a unique function:
a. Porococytes
→ These cells line the pores of the
sponge. They are the structure
through which water is taken into
the organism.
b. Choanocytes
→ These cells exhibit flagella that
create inward currents of water
for the sponge's stationary filterfeeding mechanism.
c. Amoebocytes
→ These are motile cells that
perform
various
digestive
functions within the sponge by
transporting/storing food and
excreting waste.
2. Flagellated Chamber
→ one of the outpouchings of the
wall of the central cavity of a
sponge that is lined with
choanocytes and connects with
incurrent
canals
through
prosopyles
3. Prosopyle
→ the aperture between incurrent
and radial canals in some
sponges
4. Apopyle
→ one of the openings by which the
water passes out of a radial canal
or flagellated chamber of a
sponge
5. Ostium
→ a series of tiny pores all over the
body of a sponge that let water
into the sponge.
→ One of these is called an ostium.
→ water flows into a sponge
through cells with pores (these
cells are called porocytes)
located all over its body.
6. Osculum
→ an excretory structure in the
living sponge, a large opening to
the outside through which the
current of water exits after
passing through the spongocoel.
→ Wastes diffuse into the water and
the water is pumped through the
osculum carrying away with it
the sponge's wastes.
7. Cells Present
i.
Pinacocytes
o are thin walled and flat cells.
They line the outer surface
of a sponge.
o Pinacocytes are slightly
contractile.
o Their contraction can change
the shape of some sponges.
o Some pinacocytes forms
tube
like
contractile
porocytes.
o Porocytes regulate water
circulation.
o The openings of the
porocytes are pathways to
water movement of water
through the body wall.
ii.
Mesohyl
o Mesohyl is a jelly like layer
present
below
the
pinacocytes.
o Amoeboid cells are present
in it.
o These cells are called
mesenchyma cells.
o The meseuchyma cells
freely move in the mesohyl.
These cells are specialized
for reproduction, secreting,
skeletal
elements,
transporting and storing food
and forming contractile rings
around openings in the
sponge wall.
iii.
Choanocytes
o Choanocytes or collar cells
are present below the
mesohyl.
o They form the lining of the
inner chamber.
o Choanocytes are flagellated
cells.
o
They have a collar like ring
of microvilli surrounding a
flagellum.
o Microfilaments connect the
microvilli.
o It forms a netlike structure
within the collar.
o The flagellum creates water
currents through the sponge.
o The
collar
filters
microscopic lbod particles
from the water.
o Collar cells arc also present
in a group of protists called
choanollagellates.
o Choanocytes are present in
sponges and choantlagellaes.
It suggests an evolutionary
link between these groups.
Canal System of Poriferans:
→ represents the transitional grade
between the simplest ascon type
and more complex ones.
→ The complication is due to the
out-pushing of the wall into
finger-like projections, called the
radial canals, at regular intervals.
→ In this type of canal system,
choanocytes are only limited to
the radial canals. Their detailed
account has already been
described with the biology of
Sycon.
1. Asconoid Type
→ is re-garded to be the most
simple and primitive grade of
canal system.
→ Asconoid type is present in these
sponges whose body is vase-like
and radially symmetrical.
→ The asconoid type of canal
system is characterised by the
presence
of
a
complete
continuous layer of choanocytes
lining the spongocoel interrupted
only by the porocyte.
2. Syconoid Type
3. Leuconoid Type
→ In this type of canal system, the
choanocyte lining of radial
canals evaginates into many
small chambers which repeat the
same process to give rise to a
cluster of small flagellated
chambers.
→ In many cases dermal pores open
into subdermal spaces.
→ The subdermal space and
incurrent canals lead into the
small
rounded
flagellated
chamber through an opening,
termed as prosophyle.
→ The flagellated chambers open
by apopyles into excurrent
canals which form large tubes.
→ The largest one leads to osculum.
Few gradations of leuconoid
type of canal system are seen in
sponges.
4. Rhagon Type
→ The body is conical with
osculum situated at the summit.
→ The spongocoel is bordered by
oval
flagellated
chambers,
opening into it by wide apopyles.
→ Between the epidermis and the
chambers lies a considerably
thickened mesenchyme which is
traversed by incurrent canals and
subdermal spaces.
→ The rhagon type is a little
complex than the complex
syconoid type and is found in the
larval stage of Demospongiae.
Different type of Spicules:
Spicules are microscopic crystalline structures
which gives the sponges their rigidity and form.
or colloidal silica is deposited. Accordingly,
spicules are of two types:
a. Calcareous spicules:
→ The organic material in this type
of spicules is calcium carbonate
or calcite. This is the
characteristic of the sponges of
class Calcarea.
b. Siliceous spicules:
→ The organics material in this
type of spicules is Colloidal
silica or Silicon. These types of
spicules are the characteristic of
the
sponges
of
class
Hexactanellida.
On the basis of size and
function: Spicules can be of large size or small
size. Accordingly, spicules can be of two types:
a. Megascleres:
→ These are larger spicules
constituting main skeleton of
sponge body.
b. Microscleres:
→ These are the small spicules
occurring interstitially.
On the basis of number of axes and
rays: Spicules may occur in several forms like
the simple rod form or in the form of forks,
anchors, shovels, stars, plumes etc. The spicule
forms depend on the presence of number of axes
and rays. Accordingly, they can be divided into
the following forms:
•
Spicule consists of spines or rays that radiate from
a point. These are secreted by special
mesenchymal amoebocytes called scleroblast
cells.
On basis of type of deposit on core
organic matter:
All kinds of spicules have a core of organic
material around which either calcium carbonate
Monaxon: These kinds of spicules are
formed by the growth along one axis.
They may be straight needle-like or rod
like or may be curved. Their ends may be
pointed or hooked or knobbed.
Monaxons can be both calcareous and
siliceous types.
rays are characteristic of calcareous
sponges.
→ If the elongated ray bears a disc at both
ends, it is called as amphidisc.
•
Triaxon: These spicules have three axes
that cross one another at right angles to
produce six rays. Thus it is also called
hexactinal spicule. These triaxon spicules
are characteristic of glass sponges of the
class Hexactanellida.
•
Polyaxon: These are the spicules with
several equal rays radiating from a
central point. They may be grouped to
give star-like appearance. Polyaxon
spicules are found along with
microscleres.
These monaxon spicules are further divided
into two kinds:
o
o
•
Monactinal- the growth of
spicule takes place only in
direction
Diactinal- The growth of
spicule takes place in both
directions.
the
one
the
the
Tetraxon: These spicules have four rays
each pointing in different direction.
Usually one of the four rays is elongated
giving the appearance of a crown of 3
rays. Such spicules are called as triaenes.
→ Sometimes all the rays are equal, when
all the rays are equal it is termed as
calthrops.
→ When all the four rays persist, it is called
as tetraradiate or quadriradiate.
→ Sometimes one of the rays is lost and then
it is known as triradiate. These triradiate