The nature of corals and reefs
Tropical reefs are built mainly from corals, primitive animals closely related
to the sea anemones. Most of the coral types that contribute to reef construction
are colonial; that is, numerous individuals - polyps - come together to create what
is essentially a single compound organism. The polyps produce calcareous skeletons;
when thousands of millions of them are present in a single colony they form large,
stony (infact, limestone)structures which build up as reefs.
There are about 450 species of reef-building coral in the seas around Southeast Asia.
Corals grow slowly, adding about 1-10 cm growth in a year.
Creatures camoflage and survival
Creatures whose colours, patterns and shapes are unsuited to their environment
pay the ultimate penalty for being less efficient hunters or easily distinguished prey.
Because they have a smaller change of surviving until sexual maturity, they are unlikely
to be able to mate and pass on their genes. But creatures which are correctly "designed"
thrive and multiply. Over millions of years this process of natural selection has produced
animals with highly efficient mechanisms that enables them to be effective survivors.
Many marine animals can vary their colour. This is effected through signals from the central
nervous system causing muscles to expand sacs of black, yellow and yellow-orange pigment
that lie beneath the skin which reflect the greenish light. By using a combination of pigments,
the fish can change to match most colors.
