Question

Phylum Arthropoda

The Earth’s largest phylum is Arthropoda, including centipedes, millipedes, crustaceans, and insects. The insects have shown to be a particularly successful class within the phylum. What biological characteristics have contributed to the success of insects? In many science fiction scenarios, post-apocalyptic Earth is mainly populated with giant insects. Why don’t we see giant insects today?

Your assignment should be 250-500 words in length.

IN YOUR OWN WORDS!!!!!!! PLEASE DON'T PLAGIARISM!!!!!!

Answer 1

Biological characteristics for success of insects:-

There are many characteristic features which help in the success of insects they are-

Presence of exoskeleton the outer protective covering layer of body, their small body size, flying capacity, high reproductive ability, metamorphosis all these helps them being a successful species.

Exoskeleton - It is a hard structure ,which gives shape and support to the body's soft tissues, gives protection from predators attack or injury, minimizes the loss of body fluids in dry and freshwater environments, and gives mechanical advantage to muscles for strength and ability to move quickly and freely, It can also resist both physical and chemical attack. It is covered by an impermeable layer of wax which prevents desiccation.

Exoskeleton is made up of chitin, a polysaccharide which binds with various protein molecules to form the body wall, which is flexible and elastic and hard in nature. Muscles are attached directly to the body wall which gives it maximum strength, so that it can lift weight larger than its body weight.

Small size - small size in presence of exoskeleton helps the organism, if they were of larger size, exoskeleton might be larger in size and which, would have added load to the body and made it difficult for the organism to carry. Small size also requires minimum resources for survival and reproduction, helps in escaping and hiding from predators. Small size and adoption of body shape and color helps in blending the organism with the environment and helps in escaping the predator.

Insects are the only invertebrates who can fly, this helps them in migrating from one place to another in case of necessity. Their body shape also help them to carry a load 15 times more than their body weight.

Reproductive success is another factor for their success, a female produces large number of eggs and around all of them usually hatch, there short life cycle also helps in their success, as a result they produce large number of offspring. High reproductive potential gives the species a good chance of survival. There are many adaptations to increase their reproductive potential. They are in many females, they can store sperm for a longer period almost a year, inside the spermatheca, a specific part of the reproductive system. Also in some in a single mating a female gets enough sperm to fertilize all its eggs. Unbalanced sex ratios is also another factor, where females are more than males, it helps in maximizing the reproductive potential. As most insects are not monogamous, a few males can supply sperm to a large number of females. There are many species like aphids, scale insects, midges in which males are absent, all members of these species are females, in them the reproduction takes place asexually.

Metamorphosis is also another factor for their success, it is the developmental change between immature stage to adult stage. Metamorphic changes are changes in physical, biochemical, and behavioural level, they help in the survival, dispersal, and reproduction of the organism.

At present significant level of pesticide resistance is also seen in insects which is another mode of adaptation.

All these biological characteristics make it a successful organism.

Huge insects which were found in million years ago, are now extinct because of these factors-

1) Change in atmosphere, million years ago, the air surrounding earth was warmer, moist and has more oxygen, as for insects oxygen levels in air is very important because they don’t possess lungs, there respiration takes place by spiracles. These a series of opening along their body through which air flows they directly connected to the tissues which requires oxygen. Due to reduction of oxygen level respiration got inhibited and led to extinction.

2) Evolvement of dinosaurs- When the ancient dinosaurs evolve, they were flying it put impact on these insects, they became the predators of these insects and created competition which led to the extinction of these giant insects and gradually small sized insects developed.

These are the reasons behind extinction of these giant insects.