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Plants first appeared on earth 400 million years ago. Insects arrived 100 million years later. Ever since, a fierce war has raged between the two.
At first it does not seem likely that the plants would stand any chance in the battle. Plants, unlike insects, cannot move. Plants are vastly outnumbered by insects; an average oak tree will have tens of thousands of insects feeding on it. The great naturalist Charles Darwin once carried out an interesting experiment to show how insects destroy plants. He dug and cleared a piece of ground about one meter square and then began counting all the tiny weeds as they sprang out of the earth. Out of the 357 plants that grew, 295 were destroyed by insects.
However, despite this fierce onslaught, plants are well able to survive. Scientists now know that plants have been using deadly chemicals and poison gas to deter their enemies! One type of potato releases a chemical that will kill any greenfly attacking it. Tomatoes can release a gas that kills attacking worms. Trees produce a poison called tannin when their leaves are chewed by hungry insects. Perhaps the most amazing defence of all is that used by the bracken plant. It will produce cyanide, the most deadly of all poisons, when the chewing insects attack. But bracken does allow ants to drink its nectar; the ants, in return, fight off other insects that attack the plant.
A small group of plants has launched a full-scale offensive against their enemies in this great war. These are the carnivorous plants. They have turned to trapping, killing and devouring insects.
Answers
Answer:The most recent understanding of the evolution of insects is based on studies of the following branches of science: molecular biology, insect morphology, paleontology, insect taxonomy, evolution, embryology, bioinformatics and scientific computing. It is estimated that the class of insects originated on Earth about 480 million years ago, in the Ordovician, at about the same time terrestrial plants appeared.[1] Insects may have evolved from a group of crustaceans.[2] The first insects were land bound, but about 400 million years ago in the Devonian period one lineage of insects evolved flight, the first animals to do so.[1] The oldest insect fossil has been proposed to be Rhyniognatha hirsti, estimated to be 400 million years old, but the insect identity of the fossil has been contested.[3] Global climate conditions changed several times during the history of Earth, and along with it the diversity of insects. The Pterygotes (winged insects) underwent a major radiation in the Carboniferous (356 to 299 million years ago) while the Endopterygota (insects that go through different life stages with metamorphosis) underwent another major radiation in the Permian (299 to 252 million years ago).
Most extant orders of insects developed during the Permian period. Many of the early groups became extinct during the mass extinction at the Permo-Triassic boundary, the largest extinction event in the history of the Earth, around 252 million years ago.[4] 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).[5][6]
Many modern insect genera developed during the Cenozoic that began about 66 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.
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