Evolution of Castes in Insects l BERNHARD RENSCH The evolution of organisms in the succession of generations has been primarilly achieved through the appearance of new hereditary variants with minor deviations along with the development of stable structures and functions. Harmful mutants were eradicated either immediately or in the subsequent generations through the process of natural selection while unharmful or advantageous ones usually survived. As this process continued, many new races and species developed which possessed structures and functions of a rational nature and which became increasingly independent from their environment. These evolutionary tendencies were also promoted through either geographical, ecological, physiological or genetical isolation of populations. In some phylogenetic lines, there occurred an increase in the number of cells due to additional cellular divisions in the morphogenesis of structures. This opened up the possibility for the development of the division of labour within cellular groups leading to more complicated and consequently more successful functions of tissues and organs. A further advancement in the adaptation of a species to its environment was made possible through specialization for certain functions of whole individuals or groups of individuals.
The natural world comes alive for young readers with Rookie Read-About "RM" Science With striking, full-color photos and just the right amount of text, this series immediately involves young readers as they discover intriguing facts about the fascinating world around them.
This title offers a guide to the world of arthropods, covering many insect orders, including beetles, flies, stick insects, dragonflies, ants and wasps, as well as microscopic creatures. It provides a fascinating overview of insects and spiders, including their habitats and classification, all shown in over 195 beautiful photographs and illustrations. All aspects of insect life are covered, such as the way insects defend themselves and how they are able to jump, leap and fly. It describes cryptic coloration, and the way insects can use camouflage to blend into their background and escape attack from predators. It offers various methods of feeding are discussed, from biting and chewing to lapping, sucking, piercing and filter feeding, according to their different mouthparts. It outlines their useful role in pollination of crops, production of honey, and removing insect pests. In the arthropoda phylum, insects are one of the most successful species, and spiders are one of the largest groups. This book studies how they organize their lives. The first section provides information of every aspect of insect life: evolution, anatomy, life cycles, flight and social organization. The last section describes the 30 orders within the class Insecta, demonstrating the huge variety of insects, from microscopic creatures to giant stick insects and large beetles. Typical features of insects in each order are highlighted. With expert text, illustrations and clear photographs, this guide will be enjoyed by all who take an interest in natural history.