All arthropods have segmented bodies. Muscles in each segment operate that segment and the appendages attached to it. Jointed, specialized appendages permit complex patterns of movement, including, in insects, the ability to fly. With flight, insects took advantage of new feeding and lifestyle opportunities, which contributed to the unparalleled evolutionary success of this group.
learning outcomes
You should be able to:
Describe morphological innovations of arthropods, and their potential effects on arthropod diversity.
Distinguish among different forms of metamorphosis in arthropods.
Explain how the evolutionary innovations among arthropods are related to the distribution of major groups across the Earth’s environments.
What features have contributed to making arthropods among the most abundant animals on Earth, both in number of species and in number of individuals?
The segmented bodies of arthropods, with rigid exoskeletons and jointed appendages, provide support for walking, swimming, and flying, so arthropods are well suited to life in many different environments. Their exoskeletons also provide protection against dehydration and predation.
Describe the difference between incomplete and complete metamorphosis.
Incomplete metamorphosis involves a series of gradual changes among instars. Complete metamorphosis involves a dramatic morphological change between two developmental stages, as between caterpillars and butterflies.
There are more described and named species of insects than of all other species on Earth combined. However, only a very few insect species live in marine environments, and those species are restricted to the intertidal zone or the ocean surface. What factors may have contributed to the insects’ lack of success in the oceans?
One factor contributing to the success of insects is that flight gives insects greater access to plants. Many insect species are specialists on one or a few plant species, and plant diversity is far greater on land and in freshwater environments than in the oceans. Although some insects live in fresh water for part or all of their life cycles, these freshwater environments are closely associated with surrounding terrestrial environments. Crustaceans have been much more successful in the oceans than have insects, and crustaceans may simply outcompete insects in marine environments.