Invertebrate Zoology: A Study Guide - T. A. Dauda 2014

Preface

The proposed course "Invertebrate Zoology" is intended for biology students at agricultural universities who are training to become veterinarians, zoo-engineers, and ecologists.

The book examines the main phyla of invertebrate animals, whose representatives are widely distributed across the globe. The material is presented according to a classical scheme. First, the most general and Characteristic Features of the phylum are provided, followed by the morphophysiological CHARACTERISTICS OF THE Class under study, and finally, Representatives of the most practically and scientifically important orders whose species are found in our country are discussed. After describing the typical features of an order, the characteristic biological positions of the species are presented in connection with their ecological living conditions, along with their Significance in nature and human attitudes toward them (protection, eradication, limited harvesting, etc.).

The study guide covers issues of phylogeny, evolution, and the ecology of individual systematic groups of invertebrate animals. Much attention is paid to parasitic species, and the Practical significance of animals is discussed in considerable detail.

Introduction

The animal and plant worlds are integral and closely interconnected PARTS OF THE surrounding organic nature. There is much in common between PLANT AND ANIMAL organisms: their bodies consist of Cells; both exhibit irritability, METABOLISM, growth, reproduction, heredity, Variability, and internal regulation. This testifies to the common origin of all Earth's inhabitants from a single ROOT—primitive living organisms whose development led to The formation of various groups on Earth: the kingdoms of plants, animals, Fungi, and Bacteria.

The main differences between animals and plants are as follows: most animals are motile, whereas plants are typically attached to a surface; animal cells are covered by a thin membrane, while plant cells additionally form a Cellulose Cell wall; most animal Organs are located inside their body, which maintains a constant shape, whereas plant organs are located externally and body shape is quite variable; animal growth usually ceases after a certain period of development (although cells of various Tissues are constantly renewed), whereas plant growth continues throughout their entire life. Another difference between plants and animals is manifested in The Nature of their metabolism. Animals consume complex organic substances by feeding on plants or other animals—this mode of Nutrition is called heterotrophic. Plants are capable of absorbing carbon dioxide from the air, and Water and inorganic substances from the soil. From these, under The Influence of solar energy in the presence of the green pigment chlorophyll, complex Organic compounds are formed through Photosynthesis, with oxygen released as a byproduct. This mode of nutrition is called autotrophic.

Humanity's first acquaintance with animals, as well as with plants, dates back to the earliest stages of The Development of primitive society. Hunting and consuming animals, as well as domesticating and breeding them, provided humans with their first knowledge about the anatomy, lifestyle, and diseases of animals.

Later, in Ancient Greece, the generalization of information about animals led to The Emergence of zoology as an independent science (from the Greek *zoon* — animal, *logos* — study). The great ancient Greek scientist and philosopher Aristotle (384–322 BC), who was familiar with about 500 species of animals, is considered the founder of zoology. He divided all the animals known to him into 2 large groups: blooded animals with a spinal Column and bloodless animals.

After Aristotle, attempts to classify animals resumed only in the 17th–18th centuries. Among the many researchers working at that time, the Swedish scientist Carl Linnaeus (1707–1778) made the greatest contribution to biological science. His main work was the book *Systema Naturae*, which served as a culminating stage in the development of descriptive sciences—botany and zoology. In this work, C. Linnaeus proposed a system and Classification of plants and animals that, with some additions, form The basis of modern plant and animal Taxonomy. C. Linnaeus subdivided all the animals known to him (about 4,200 species) into 6 classes: mammals, birds, amphibians, fish, insects, and worms. He further subdivided these animal classes into orders, orders into genera, and genera into species. At the same time, C. Linnaeus believed that a species is a collection of similar individuals that interbreed freely, produce fertile offspring, and have no transitions to other (neighboring) species. Linnaeus's proposal of a binary (double) naming of species using Latin words proved highly successful. The first—the generic name—was common to all closely related species united in a genus, while the second—the specific epithet proper—identified the species (for example, the large roundworm — Ascaris lumbricoides).

Along with scientific ideas that have endured through the centuries, Linnaeus's views also contained idealistic thoughts. In particular, he believed that the entire world was created by a Creator (God). Despite these idealistic views, his method (binary species naming, strict subordination of taxonomic categories) proved rational and is still in use today.

A major contribution to the further development of zoology was made by the French scientists Jean-Baptiste Lamarck (1744–1829) and Georges Cuvier (1769–1832), who improved C. Linnaeus's System of the animal kingdom. The former championed the idea of the evolutionary historical development of living nature, although he misinterpreted the causes of evolution, linking them to an Organism's innate ability to adapt to the environment. The latter established THE CONCEPT OF phyla in zoology and was the first to unite fish, amphibians, reptiles, birds, and mammals into a single phylum—vertebrates. His works laid the foundation for the formation of a new science—vertebrate paleontology. Also important are the works of the German scientist Theodor Schwann (1810–1882), who in 1839 formulated the basic tenets of Cell Theory, proving that All living organisms consist of cells.

The comprehensive study of animals led to the emergence of many new systems of the animal kingdom, but all of them were artificial, since no one before Charles Darwin (1809–1882) imbued the concept of a natural system of the animal kingdom with evolutionary content. In his book *On THE ORIGIN OF Species by Means of Natural Selection*, he proved the historical development of all living organisms from a single root. Ch. Darwin explained the existence and subordination of all systematic categories using The Theory of natural selection and THE PRINCIPLE OF divergence of character, laying the THEORETICAL FOUNDATIONS OF The Natural System by proving that it was formed in The process of the Evolution of the organic world.

Of great importance for proving and improving the natural system of animals, as well as for the development of zoological science as a whole, were the works of prominent Russian scientists K. Roulier (1814–1858), K. M. von Baer (1792–1876), A. N. Severtsov (1827–1885), A. S. Kovalevsky (1840–1901), I. M. Mechnikov (1845–1916), and others.

The deep and comprehensive Study of the animal kingdom in the 19th and early 20th centuries, the accumulation of vast factual material, and The Diversity of research tasks and Methods led to the emergence of A number of independent zoological branches of knowledge, each examining animals from its own perspective. Thus, today zoology represents a whole complex of interconnected sciences studying a single object—animals.

Animal Morphology studies The Structure of organisms. It includes anatomy, which examines the macroscopic structure (i.e., visible to the naked eye) of organs and Organ Systems in animals; Histology, which studies the microscopic structure of tissues and organs; Cytology, which investigates the Structural Features of animal cells; and Embryology, whose subject of research is the regularities of embryonic development in animals. Animal physiology examines the life processes occurring within the organism (Digestion, Respiration, excretion, The activity of The Nervous system and Sense Organs, etc.). Ethology investigates animal behavior under natural conditions. Animal ecology clarifies the relationships between organisms and their environment. Zoogeography studies the regularities of animal distribution across the globe. Animal genetics is the science of the regularities of heredity and variability in organisms. Animal phylogeny investigates the historical Development of the animal kingdom and individual groups of organisms. Paleozoology studies the fossil remains of extinct animals, their structure, origin, and evolutionary relationships with modern forms. Animal taxonomy, based on other zoological sciences, deals with the Classification of organisms and constructs a natural system of the animal kingdom.

The modern natural system of the animal kingdom includes about 2 million species. The animal kingdom is conventionally divided into a series of mutually subordinated systematic categories—taxa.

The principle of binary nomenclature, developed by C. Linnaeus, is used to designate species. Each species is assigned a Latin name consisting of two words. The first word—a noun—is the name of the genus that groups together a cluster of closely related species; the second word—usually an adjective—is the species name. For example, the scientific name of the small white butterfly is Pieris brassicae, while closely related species belonging to the same genus Pieris are called: the green-veined white — Pieris rapae, the small-veined white — Pieris napi, etc. Binomial names are convenient because they immediately indicate the generic affiliation of the species.

If a species name is established According to the rules of the "International Code of Zoological Nomenclature," it is considered mandatory for everyone. The only valid name for a species is the one established earlier than all others; a name proposed later is not recognized.

Closely related genera are grouped into families, families into orders, and orders into classes. The highest taxon in modern taxonomy is the phylum, which unites several related classes. Zoologists frequently use "intermediate" taxa: subphyla, subclasses, suborders, etc., which unite groups of lower rank within a given taxon.

The currently accepted system of the animal kingdom is based on more than 20 phyla. The proposed study guide examines the morphological and Biological features of the following 11 phyla of greatest practical importance:

1. Sarcomastigophorans (Sarcomastigophora).

2. Sporozoans (Sporozoa).

3. Ciliates (Ciliophora).

4. Sponges (Spongia or Porifera).

5. Coelenterates (Coelenterata or Cnidaria).

6. Flatworms (Plathelminthes).

7. Pseudocoelomates, or Roundworms (Nemathelminthes).

8. Segmented worms, or Annelids (Annelida).

9. Mollusks (Mollusca).

10. Arthropods (Arthropoda).

11. Echinoderms (Echinodermata).

The animal kingdom is naturally divided into two subkingdoms: Unicellular organisms (Protozoa) and Multicellular Organisms (Metazoa).

It should be noted that invertebrates within the animal kingdom are abundant both in terms of the number of species and the number of individuals.

QUESTIONS FOR SELF-assessment and review:

1. What are the Similarities and differences between plants and animals?

2. What are the main Stages of development highlighted in The history of zoology?

3. Why is zoology currently considered an interdisciplinary science?

4. What are the Basic principles of zoological systematics?