‘entomon' and `logos'; ‘entomon’



Download 8.6 Mb.
Page13/36
Date conversion15.05.2018
Size8.6 Mb.
1   ...   9   10   11   12   13   14   15   16   ...   36

(06) Class Insecta or Hexopoda – insects
Evolution of insects:
Based on genome sequencing data, it is estimated that the class of insects originated on Earth about 480 million years ago (48 †KvwU eQi Av‡M), in the Ordovician (The is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 485.4 and 443.8 million years ago), at about the same time terrestrial plants appeared.
Insects evolved from a group of crustaceans. They were the first animals to develop flight, about 400 million years ago in the Devonian period (The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 419.2 Mya (million years ago).
The oldest definitive insect fossil, Rhyniognatha hirsti, is estimated to be 407 to 396 million years old. Global climate conditions changed several times during the history of Earth, and along with it the diversity of insects.
The Pterygotes (winged insects) was found in the Carboniferous (356 to 299 million years ago) while the Endopterygota (insects that go through different life stages with metamorphosis) was also found in the Permian (299 to 252 million years ago).
Most extant (GLb Awã we`¨gvb) orders of insects developed during the Permian period (The Permian is a geologic period and system which extends from 298.9 to 252.17 million years ago). Many of the early groups became extinct during the mass extinction at the Permo-Triassic boundary (extinction is a major watershed in the history of life on Earth), the largest extinction event in the history of the Earth, around 252 million years ago.
The survivors of this event evolved in the Triassic (252 to 201 million years ago) to what are essentially the modern insect orders that persist to this day. Most modern insect families appeared in the Jurassic (201 to 145 million years ago).
In an important example of co-evolution, a number of highly successful insect groups especially the Hymenoptera (wasps, bees and ants) and Lepidoptera (butterflies) as well as many types of Diptera (flies) and Coleoptera (beetles) evolved in conjunction with flowering plants during the Cretaceous (145 to 66 million years ago).
Many modern insect genera developed during the Cenozoic that began about 65 million years ago; insects from this period onwards frequently became preserved in amber, often in perfect condition. Such specimens are easily compared with modern species, and most of them are members of extant genera.
Phylogeny of Arthropoda/Insects:
The evolutionary history of a group of organisms, especially as depicted in a family tree is called Phylogeny./ The evolution of a genetically related group of organisms as distinguished from the development of the individual organism is called Phylogeny./ The development or evolution of a particular group of organisms. The phylogeny related to insects is called phylogeny of insects.


1   ...   9   10   11   12   13   14   15   16   ...   36


The database is protected by copyright ©dentisty.org 2016
send message

    Main page