According to taxonomists, Arthropoda is the largest existing phylum of creatures present on Earth. Commonly known as insects or bugs, they cover at least 80% of the Earth population. There are about 1 million species present under this phylum and many are yet to be discovered. Arthropods had come into existence on Earth 100 million years before the vertebrates did. The colonization of land was easier for them as they had already evolved legs which they had used for walking at the bottom of the sea.
A phylum is a category which comes under the Kingdom classification of all the creatures present in this planet. The creatures are classified and divided into groups based on their physical traits or characteristics. Species is the lowest level of the division classification while Kingdom being the highest. There are mainly five types of Kingdom; dividing the plants, animals, multicellular and unicellular into different categories. The list of Kingdom classification goes on like this:-
KINGDOM
PHYLUM
CLASS
ORDER
FAMILY
GENUS
SPECIES
Arthropoda is the phylum of bugs. All of them share certain similarities in their traits. They all have exoskeleton, i.e., a hard cover present outside the body which acts as an armour protecting the organs present inside. The exoskeleton is made up of a hard substance known as chitin (KIE- tin), made of a derivative of the sugar glucose, which is secreted by the cells of the underlying epidemis. Since the exoskeleton cannot grow, an insect has to shed its cover periodically in order to grow. The process is known as Moulting. They undergo metamorphosis which is a process where their bodies change radically as they pass from their larval to adult stages. Butterflies are the best-known for entering cocoons as caterpillars and coming out quite different.
Arthropod means jointed-foot. In order for an Arthropod to move in such a rigid body, it has numerous joints in its exoskeleton. Like door hinges, they allow bending in only one direction. They had come into existence on Earth 100 million years before the vertebrates did. The colonization of land was easier for them as they had already evolved legs which they had used for walking at the bottom of the sea.
The phylum Arthropod is sub-categorized into four Families:-
a. Insects like ants, dragonflies, bees, cockroach etc.
b. Arachnids like spiders and scorpions.
c. Myriapods, a term which is used for creatures having many pairs of feet such as millipedes, centipedes etc.
d. Crustaceans such as lobsters, shrimps, crabs etc.
Crustaceans and Arachnids have blue blood instead of red blood. This is because their blood uses a blue copper compound to carry oxygen, instead of the red iron compound used by animals.
Arthropods are underappreciated in the contributions of the ecosystem. Without them, the survival of humans is not possible, especially bees. This is the reason why people are donating huge amounts of funds to organizations for their conservation. Mites are used to prey on unwanted arthropods in farms and homes. Some are used for weed control. Scorpions and millipedes feed on destructive fungi and bacteria. Cockroaches, spiders, mites, ticks and other insects are considered carnivores and thus prey on other smaller species for ecological balance. Thus, they are the best pest control humans can have.
Arthropods are of ecological importance because of their sheer numbers and extreme diversity. Bees, wasps, ants, butterflies, moths, houseflies, beetles etc are agents of pollination. Pollens and grains get attached to their chest and legs and are transferred to other fields and crops.
Mites, ticks, centipedes, and millipedes are decomposers, meaning they break down dead plants and animals and turn them into soil nutrients. This is an important role because it supplies the plants with the minerals and nutrients necessary for life. It also keeps dead material from accumulating in the environment. Plants then pass along those minerals and nutrients to the animals that eat the plants.
Arthropods are also invaluable to humans. They are used in many different human-made products like silk produced by caterpillars; pollens in honeycombs; spiders’ web using for adhesive and antiseptics etc.
Many species of Crustaceans, especially crabs, lobsters, shrimp, prawns, and crayfish, are consumed by humans, and are now farmed on a large commercial scale. Nearly 10,000,000 tons of arthropods as food were produced in 2005. Over 70% by weight of all crustaceans caught for consumption are shrimp and prawns. Over 80% is produced in Asia, with China producing nearly half the world’s total.
Arthropods play an integral part in our environment. The flux in their population indicates an environment change. They play an integral part in the health and livelihood of all the other species and their extinction would be a doom to us all!
Written by:-
Damini Bagchi
