👉Annelids are metamerically segmented animals with a true coelom. 👉The arthropods are the most abundant group of animals characterised by the presence
of jointed appendages. The body is covered with external skeleton made of chitin
👉The molluscs have a soft body surrounded by an external
calcareous shell. .
👉The echinoderms possess a spiny skin. Their most distinctive feature is the presence
of water vascular system.
👉The hemichordates are a small group of worm-like marine
animals. They have a cylindrical body with proboscis, collar and trunk.
👉Exoskeletons of arthropods, for example, have a complex
polysaccharide called chitin. These complex polysaccharides are mostly
homopolymers.
👉Decomposition is largely an oxygen-requiring process. The rate of
decomposition is controlled by chemical composition of detritus and
climatic factors. In a particular climatic condition, decomposition rate
is slower if detritus is rich in lignin and chitin, and quicker, if detritus is
rich in nitrogen and water-soluble substances like sugars.
👉With the exception of yeasts which are unicellular, fungi are
filamentous. Their bodies consist of long, slender thread-like structures
called hyphae. The network of hyphae is known as mycelium. Some hyphae
are continuous tubes filled with multinucleated cytoplasm – these are
called coenocytic hyphae. Others have septae or cross walls in their
hyphae. The cell walls of fungi are composed of chitin and polysaccharides.
👉Phylum – Arthropoda
This is the largest phylum of Animalia which
includes insects. Over two-thirds of all named
species on earth are arthropods .
They have organ-system level of organisation.
They are bilaterally symmetrical, triploblastic,
segmented and coelomate animals. The body
of arthropods is covered by chitinous
exoskeleton. The body consists of head, thorax
and abdomen. They have jointed appendages
(arthros-joint, poda-appendages). Respiratory
organs are gills, book gills, book lungs or
tracheal system. Circulatory system is of open
type. Sensory organs like antennae, eyes
(compound and simple), statocysts or
balancing organs are present. Excretion takes
place through malpighian tubules. They are
mostly dioecious. Fertilisation is usually
internal. They are mostly oviparous.
Development may be direct or indirect.
Examples: Economically important insects –
Apis (Honey bee), Bombyx (Silkworm), Laccifer
(Lac insect)
Vectors – Anopheles, Culex and Aedes
(Mosquitoes)
Gregarious pest – Locusta (Locust)
Living fossil – Limulus (King crab).
This is the largest phylum of Animalia which
includes insects. Over two-thirds of all named
species on earth are arthropods .
They have organ-system level of organisation.
They are bilaterally symmetrical, triploblastic,
segmented and coelomate animals. The body
of arthropods is covered by chitinous
exoskeleton. The body consists of head, thorax
and abdomen. They have jointed appendages
(arthros-joint, poda-appendages). Respiratory
organs are gills, book gills, book lungs or
tracheal system. Circulatory system is of open
type. Sensory organs like antennae, eyes
(compound and simple), statocysts or
balancing organs are present. Excretion takes
place through malpighian tubules. They are
mostly dioecious. Fertilisation is usually
internal. They are mostly oviparous.
Development may be direct or indirect.
Examples: Economically important insects –
Apis (Honey bee), Bombyx (Silkworm), Laccifer
(Lac insect)
Vectors – Anopheles, Culex and Aedes
(Mosquitoes)
Gregarious pest – Locusta (Locust)
Living fossil – Limulus (King crab).