explorers may also have been avoiding large predators such as sea scorpions that preferred to hang out in deeper water Arthropods were well equipped for life on land in prehistoric times Their exoskeletons helped protect them from the sun Their jointed legs propelled them onto land SPRINGTAILS Springtails may have been some of the earliest land dwellers These small wingless arthropods may have originally crawled out of the water to reproduce away from predators and to seek a hiding place in the algae Springtails got their name because of the taillike appendage they use for leaping They're so similar to insects that scientists used to believe they were closely related but recent DNA studies put them in their own order They probably made the transition from ocean to land before insects The evolution of insects occurred in four episodes or stages that happened over millions or even tens of millions of years The first episode of insect evolution was when the early insect ancestors which resembled modern bristletails from the order Archaeognatha evolved The second stage was when some insects evolved wings that can't fold such as those on dragonflies Later other insects evolved wings that could fold such as those 10
Butterflies develop through complete metamorphosis Caterpillars undergo a drastic transformation into their adult forms on cockroaches The fourth stage of evolution was the evolution of complete metamorphosis the transformation of the animal as it develops to an adult form One example of this is the transformation of caterpillars to butterflies Finally social groups developed For example ants or bees live and work together in groups to find food and rear their young Metamorphosis is a process that benefits insects by allowing them to have significantly different life stages to avoid competition for habitats and food sources within a species Not all insects use metamorphosis in the growth and development process and some only use incomplete metamorphosis However all animals with an exoskeleton must shed their skin to
grow which is why different insects have varying levels of metamorphosis Insects from the fourth stage of evolution have complete metamorphosis which includes three life stages larva pupa and adult The different life stages use energy efficiently for a specific goal This allows the insects to transition rapidly through their life cycles A larva such as a caterpillar may look completely different from the adult form The larva spends most of its time eating and growing During the pupal stage the pupa is inactive Its body often encased in a protective covering changes from the larval form to the adult form Adults emerge from the pupal stage ready to find a mate and reproduce On the other hand insects from the first stage of evolution do not participate in any metamorphosis Often the juvenile insects look very similar to the adults and the main distinction is whether or not the sex organs are functional Then there are insects from the second and third stages of evolution Some take part in incomplete metamorphosis with pronymph nymph and adult stages The pronymph stage may largely happen while in the egg A pronymph is generally helpless and does not actively feed but lives off of the nutrients from its yolk Nymphs typically look similar to their adult forms but they cannot reproduce They eat and change as they grow into adults Sometimes the physical function between the nymph and adult stages of an insect are so different that the insect must develop a completely different
A dragonfly nymph bears some resemblance to its adult form form as it grows Scientists believe the pronymph nymph and adult stages later evolved into the more efficient stages of larva pupa and adult in some groups Evolution is defined as genetic changes in organisms across generations All organisms alive today and those that are extinct are connected Genetic changes come about as mutations in the DNA Genetic mutations random changes in the animal's DNA can occur throughout an organism's life The mutations won't affect the future population unless they change the animal's chance of survival Natural selection can then act on these mutations For instance if a mutation leads to a trait that increases reproduction or survival animals will reproduce and pass on that trait to their offspring Over time the trait that allows animals to survive and reproduce will become more common
