XI Unit 9 Invertebrates - Evolutionary Adaptations (PDF)

# Kingdom Animalia ## Phylum Anthropoda * **Jointed Legs:** Largest phylum. Includes about a million species, found in most habitats. * **Distinguishing Characteristics of Phylum Anthropoda** * **General Organization of the Body:** * Bilaterally symmetrical, triploblastic, metamerical...

# Kingdom Animalia ## Phylum Anthropoda * **Jointed Legs:** Largest phylum. Includes about a million species, found in most habitats. * **Distinguishing Characteristics of Phylum Anthropoda** * **General Organization of the Body:** * Bilaterally symmetrical, triploblastic, metamerically segmented animals * Bodies divided into head, thorax and abdomen * Coelomic space is called hemocoel because it is occupied by blood sinuses in an open circulatory system. * **Mode of Respiration:** * Gills in aquatic forms * Trachea in insects * Book lungs in scorpions * **Mode of Nutrition:** * Well developed alimentary canal assisted by jaws, suckers, etc. * **Mode of Excretion:** * Excretory organs are mostly malpighian tubules * **Nervous System:** * Nervous system is a paired format of ganglia around the mouth, a ring or collar around the gullet and a ventral chain of ganglia. * **Muscular System:** * Highly developed, numerous separate muscles are present. * **Circulatory System:** * Open circulatory system. * **Mode of Locomotion:** * Provided with jointed feet and may be provided with wings. * **Exoskeleton:** * Chitinous exoskeleton forms a protective covering around the whole body and appendages. It is non-living and is shed and replaced by a new one as the body grows by a process called ecdysis or moulting. * **Reproduction:** * Sexes are separate, fertilization is internal. Most arthropods undergo metamorphosis where a set of changes transforms larva into adult stage. ## Economic Importance of Anthropoda **Useful Effects** * **Insects help in pollination.** * **Arthropods are used as food for many animals and carnivorous plants.** * **Honey bee farming called apiculture and silk bee farming called sericulture.** **Harmful Effects** * **Many arthropods cause diseases in plants and animals by transmitting microrganisms.** * *For example:* Transmission of Trypanosomes, Plasmodium and germs of cholera, etc. ## Phylum Annelida * Also called segmented worms. Includes about 15,000 species. Most complex body structures of all the worms. * **Distinguishing Characteristics of Phylum Annelida** * **General Organisation of the Body:** * Triploblastic, bilaterally symmetrical organisms with an organ system level of organization. * Distinguished by their ring-like external segments called "metarmeres" which coincide with internal partitions called "septa". * Excretory and reproductive organs are repeated in each segment. * Coelomates with coelomic compartments in the body. * **Mode of Locomotion:** * Some annelids have chitinous structures called setae with or without parapodia for locomotion. * **Mode of Excretion:** * Excretory organs are a pair of more tubular nephridia per segment. * **Mode of Respiration:** * Respiration takes place by diffusion through the moist skin. * **Circulatory System:** * Closed circulatory system with definite blood vessels and many pulsatile hearts. Blood is usually red with haemoglobin dissolved in it. * **Mode of Nutrition:** * They may be predators, filter feeders or parasites. Some live on dead organic matter. * **Mode of Reproduction:** * They may be hermaphrodite or heterophodrite. In some species, trocophone larva is formed. * **Nervous System:** * Well developed nervous system with pair of cerebral ganglia (brain). Some have sense organs. ## Phylum Mollusca * It's the second largest phylum of kingdom Animalia with about 50,000 species of living and 35,000 of fossil mollusca. They are terrestrial or aquatic. ### Distinguishing Characteristics of Phylum Mollusca * **General Body Organization:** * Soft-bodied, triploblastic, coelomate, bilaterally symmetrical animals with organ system grade of body organization. * Mostly unsegmented. Coelom has reduced because of large fluid-filled cavities of the open circulatory system. * Hydrostatic skeleton. * Body is divided into head, mantle, foot and visceral mass. * **Mode of Nutrition:** * Alimentary canal is a straight or coiled tube, with a mouth and anus at the opposite ends. Most of them are provided with a rasping feeding structure, the radula in their buccal cavity. * **Circulatory System:** * Closed circulatory system. * **Excretory System:** * Well developed excretory system with paired kidneys for excretion. * **Mode of Gaseous Exchange:** * Respiration takes place by gills in aquatic form and by rudimentary lungs in terrestrial forms. * **Mode of Locomotion:** * Mostly provided with "foot" and some have arms for locomotion. * **Shell:** * Shell constitutes an exoskeleton which may be univalve or bivalve and internal in some. * **Mode of Reproduction:** * Sexes are separate and fertilization takes place in water. Trocophore larva is formed. ### Common Characteristics in all Molluscs * **Head-Foot:** * A head-foot portion primarily concerned with sensation, feeding and locomotion. * **Visceral Mass:** * A dorsal visceral mass that includes the major organs. * **Mantle:** * A mantle, it's a fold of delicate tissue surrounding the entire body. ## Economic Importance of Mollusca * **Paleontological Studies:** * They are important in paleontological studies and contain well preserved fossil forms. * **Sea Food:** * Variety of molluscs provide an important source of food. * *For example:* Shell fish, crustaceans. * **Pearl Formation:** * "Pearl oysters" are molluscs used in pearl formation by deposition of concentric layers of protein, nacre. * **Decorative:** * The shells are decorative and some molluscs shells and pearls are used for making jewelry items.