Ffddssdse ka bhi to mrko wish you a very happy birthday to you too dear jinendra bhai merko party re the day of the painting in the world of the day bro I am not in a rahe ho sir ko mat send kar dena hai na kal koi class nhi hai to kya kare wish to see the same to same to you and your own family dekhti hu par bhi shak nahi he ga ta uhi to the best and prepare for you to take care and research station to be a good evening mam to be a very very happy birthday dear jinendra ji ki kirpa sada sada tum par bhi ho sakta word to bhi dikkat hai na kal bshdgsiduysydggdud

1. CORAL
Definition of Coral
Corals are animals belonging to
the phylum Coelenterata. These
are solitary or colonial polypoid
forms and live in a skeleton of
calcium carbonate secreted by
themselves. Some of them grow
into huge mounds, while others
are large and branched colonies.
However, most of the corals
belong to the class Anthozoa
and few others to the class
Hydrozoa.

3. II] Structure of coral polyp
• Soft structure. A typical coral polyp from a colony is a small organism about 10 mm
long and 1 to 3 mm in diameter. Solitary coral polyps are much larger reaching up to
25 cm in diameter.
• A basal disc is absent because the basal region of polyp is surrounded by a
calcareous exoskeleton.
• Oral disc bears numerous tentacles, in several rows around an elongated, oval or
circular mouth.
• Pharynx or stomodaeum is short and without siphonoglyphs.
• Mesenteries are restricted to the upper part of coelenteron and mesenterial
filaments nematocysts one glandular lobe bearing nematocysts.
• Bodywall is without cinclides and nematocyst bearing Strucyures (acontia).
• Muscles are poorely Developed while little is known about nervous system.
• Living polyps are found only on surface layers of coral masses. They feed at night
both by Saptorial and suspension feeding. When not feeding, they withdraw into
cup-like cavities of skeleton.

4. [III] Coral skeleton
Structure of coral skeleton.
• Skeleton of solitary coral is known as corallite.
• It is a calcareous exoskeleton secreted by epidermis.
• In a colonial coral, corallites of individual polyps fuse together to
form a skeletal mass, called corallum.
• Each corallite is like a stony cup with a basal part or basal plate, and
a cup wall or theca, enclosing the aboral portion of polyp.
• Cavity of cup contains a number of vertical radiating ridges called
sclerosepta, proceeding from theca towards the centre of cup.
• Inner ends of sclerosepta are fused to form an irregular central
skeletal mass or columella

5. 2. Formation of coral skeleton.
• In coralpolyps, sexual reproduction takes place by fusion of gametes.
• Zygote develops into a free-swimming ciliated planula larva which settles
down and metamorphoses into a young cond polyp.
• There is no medusa stage. By asexual budding, single polyp becomes the
parent of all other members of the colony.
• The coral polyp begins to secrete a skeletal rudiment or prototheca. It is
secreted by ectoderm, first a basal plate. Following it, radial folds develop
which secrete sclerosepta
Coral colony grows in size continuously by budding of new polyps, particularly
along the margins and on surface layers of coral masses. Variety in form of
compound corals results due to various patterns of budding.

10. Classification: Belongs to Phylum Cnidaria, Class
Anthozoa, Order Alcyonacea.
Common name: Sea fans.
Habitat: Found in warm, shallow tropical and
subtropical oceans, often attached to reefs.
Structure: Colonies form flat, fan-like branching
skeletons (Median axial rod) made of a flexible
protein called gorgonin.
Polyp features: Each branch bears tiny polyps with
eight tentacles (characteristic of Octocorals).
• Dioecious
Ecological role: Provide habitat and protection for
many reef organisms; participate in nutrient
cycling.

12. Coral Reefs
Definition. Vaughan (1917) has defined coral reef as "a ridge or mound of
lime stone, the upper surface of which is near the surface of the sea and
which is formed of calcium carbonate by the actions of organisms, chiefly
corals.
"The coral reefs are, in fact, produced by corals belonging to
Anthozoa, particularly by stony corals, the Madreporaria. but other
important contributors are the hydrocorallines and alcyonarians. Coralline
algae and Foraminiferan Protozoa also take part in the formation of coral
reefs.
• A coral reef, in fact, is a ridge of lime stone whose upper surface is just
below the sea surface and it is exposed at low tides.

13. Reef flat

15. Kinds of coral reefs-
The coral reefs are of three kinds, depending on how they are formed.
1. Fringing reefs.
Coral reefs lying close to the shores of some volcanic island or part of some
continent are termed fringing reefs.
Extend from the shore up to 1/4 miles having no navigable channel between the
shore and reef. This zone of the sea is called edge or front.
However, sometimes reef beds are broken to result into irregular channels called
lagoon. Such reefs are composed largely of coral sand having living and dead
corals building reefs, mud and other animals. Fringing reef is very common in East
Indies.

16. 2. Barrier reef.
• The barrier reefs are like fringing reefs but they are situated in the sea nearly 1 km
to 15 km away from the shore. Therefore, navigable channel called lagoon separates
these reefs from the shore.
• The lagoon may be 20 to 40 fathoms deep, hence, it becomes navigable.
• The Great Barrier Reef on the north-east coast of Australia is 1,200 miles long, about
20-70 miles wide and situated nearly 90 miles away from the shore.
• 1 mile = 1.609 km
• 1 fathom = 1.829 m

17. 3.Atoll reef.
• The atoll reef, also referred to as
coral island or lagoon island, is a
circular or horse-shoe-shaped reef
enclosing a lagoon of water which
may be small or large up to 50 miles
across.
• Atoll reef may be broken to form
channels; some suitable for
navigation and other may not be
suitable for it.
• An interesting atoll reef example is
Aldabra in the Indian Ocean, about
260 miles northeast of the Malagasy
Republic and 400 miles from the
coast of Africa.

18. Formation of coral reefs.
1. Darwin's subsidence theory.
• This theory states that coral reefs were first formed as fringing reefs on sloping
shores, they became barrier reefs when the shores sank with water channel between
them and the land. If the land is an island which sinks completely, then an atoll is
formed. Thus, sinking or subsidence has caused the thickness of the reefs
2. Daly's glacial-control theory.
• This theory states that during the last glacial period the formation of ice caps lowered
the ocean level by 60 to 70 metres below the present surface. Waves cut the shores
to make flat platforms suitable for growth of corals.
• As the ice caps melted and temperature rose, corals began to grow on these platforms
and rose upwards with rising ocean level, and all types of reefs were formed on the
pre-existing platforms.
• There is evidence that coral reefs are growing today on submerged land and the
foundations of reefs are now at a much greater depth than they were when corals
first began to grow.

19. The coral reefs grow best at a depth of about 30 metres or less and normally in
warm water up to about 20°C. Light and amount of sediment also limit the reef
forming corals. They also fail to grow in dark shaded areas and they completely
die in total darkness. Below 50 metres no reef building corals are found though
some solitary corals exist up to 8000 metres.
Components of coral reefs. In addition to stony corals, other components in the
formation of coral reefs are Millepora, Tubipora, Heliopora, Alcyonaria,
Gorgonians, Foraminifera, Coralline algae and branching algae, etc. The coral
reefs are also inhabited by a number of sponges, anaemones, sea-urchins,
starfishes, crabs, snails, bivalves, etc.

20. Types of Coral
1.Hard Corals (Scleractinia):
1. Characteristics: Secrete a rigid calcium carbonate
skeleton.
2. Examples: Staghorn coral, brain coral.
3. Role: Major builders of coral reef.
4. Soft Corals (Alcyonacea):
5.
6. Characteristics: Lack a rigid skeleton; have a flexible
structure.
7. Examples: Sea fans, sea whips.
Role: Provide habitat complexity but do not contribute
significantly to reef structure.