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ANIMAL CLASSIFICATION Animals evolved from colonial flagellated protists as a result of division of labour among colonial cells. Coordination of specialized cells with other group of cells begun and more complex organism are evolved. They are called animals. Animals are; • Multicellular eukaryotes • heterotrophs • Sense food source • Ingestion (eating food – distinctive feature of animals) • No cell wall • Digest food within the body • Most of them have embryonic layers (these layers form tissues, organs, systems) • Cells are connected to eachother by extracellular proteins (connective tissue) • Most animals have diploid life cycle • Most animals have muscle tissue for movement, nerve for impulses. Animals are divided into two groups according to their body symmetry 1) Radial symmetry has one main axis around which its body parts are arranged. (Simple sponges, sea anemones, Cnideria have radial symmetry). These animals move slowly or not at all. 2) Bilateral symmetry is a common characteristic of animals that move rapidly through their environments(active animals). They can be divided into mirror images. There is cephalization in bilateral symmetry. Sensory organs are located on the head. Animals can be divided into three main groups according to their body cavity. • Acoelomates: lack of enclosed body cavity Pseudocoelomates: have body cavity a liquid filled space in which many of the internal organs are suspended. There is only outer muscle layer and there is no inner layer of muscle surrounding organs. Coelomate: have a body cavity. It is enclosed by both inner and outer muscle layers Fluid filled body cavity gives the animal better control over its movement. ( Movement of heart, stomach ) Brief Classification of Animals 1) Phylum porifera • Simplest animals • They have pores in their structure, so all cells have contact with environment • There are no systems in their structure • They are suspension feeders (filter feeders). They collect food particles when water passes through the pores. • Sessile organisms 2) Phylum Cnideria(coelenterates) • They have two layers of cells, so all cells have contact with environment. They can be in two forms polyp or medusa. • They have a body cavity with single opening. Tentacles catch the prey and they digest. • They have radial symmetry. They have simple nerve net and muscle cells. • Tentacles have stinging cells that penetrate and paralyze the prey. • e.g: jelly fish (motile), hydra (sessile) 3) Phylum Platyhelminthes • They are bilateral leaf like (flat) animals. There are more than three layers of cells. They have incomplete digestive tract with single opening. • There is no space between digestive tract and outer layer (no coelom). They have simple nervous and excretory system. • Non-parasitic flatworms live in marine, fresh water damp soil in terrestrial ecosystem (planarian) • Parasitic: tapeworm and flukes AFTER THIS PHYLUM ALL ANIMALS HAVE SYTEMS FOR DIFFERENT FUNCTIONS 4) Phylum Nematoda (round worm) • They have exoskeleton which is made of cuticle. They have complete digestive tract with two openings (mouth and anus) • Some of them are important detritivores – decomposers • Some of them are parasites for humasn and plants e.g. trichinella spiralis is a parasite which is taken by uncooked pork meat 5) Phylum Mollusca • They have muscular foot, developed nervous system and other systems and soft body. They do not have skeleton. They have true coelom. • There are three main groups of mollusca. • Gastropoda: live in water and on land, they are herbivores-e.g snail • Bivalves: Aquatic animals. They have shell. They are filter feeders – e.g: mussel, scallop • Cephalopoda: Aquatic animals which have large brain. Carnivores – e.g: octopus AFTER THIS PHYLUM SEGMETATION STARTS!!! • Segmentation: subdivision of the body into parts. This feature played a central role in the evolution of many complex animals. • Segmented worms have segmented body but not segmented organs. • Arthropods have more specialized segments. Head thorax and abdomen • Mammals have segments: head, chest cavity, abdomen • *** Advantage of having segmented body is: it allows flexibility and mobility. This is adaptation for movement. Movement to catch prey or digest efficiently. 6) Phylum annelida • They consist of body segments. • They live in sea, fresh water and damp soil. • e.g. Earth worm, Polychaetes, Leechs • Most of them are scavengers • Body is externally protected by thin, elastic protein cuticle 7) Phylum Athropoda • They have systems and jointed legs, chitin exoskeleton. • Some of them are carnivores, some of them are herbivores . • They have open circulatory system • They have distinct group of segments form head, thorax, abdomen. Some classes; • • • • a. crabs b. Spiders (arachnids) c. Crustaceans d. Millipedes and centipedes • e. Insects •milipede 8) Phylum Echinodermata • All live in marine. They do not have body segments. • Most are radial symmetrical in adult, bilateral in larvae. • They have spiny skin, endoskeleton an water vascular system. • They are carnivores. • e.g: sea urchin, seastar 9) Phylum Chordota Main characteristics of chordate: • Dorsal nerve cord • Notochord : a flexible, supportive rod between digestive tract nerve cord • Pharyngeal slits (gill structure in the pharynx) • Muscular anal tail a. Invertebrate chordota • Invertebrate chordate do not have segmented backbone. • There are two main groups: Tunicate and lancelets. Both groups are suspension feeders b. Vertebrate chordata • Nerve cord is protected by bone • Sharks made of cartilage no proper bones on the nerve cord (transition between vertebrate and invertebrate) Classes: • • • • • fish amphibian reptiles birds mammals Fish • Respiration by gills, • Locomotion by fins • External fertilization young organisms are growing outside of mother’s body Amphibians • Partially terrestrial, partially aquatic (Adapt water for reproduction) • Moist skin (respiration by skin) • External fertilization • Adapt land for respiration, excretion and movement • Respiration is by gills for tadpoles and by lungs, and skin for adult frogs What are the differences between amphibians and fish?? • Gills become lungs • Fins become forelimbs Reptiles • Dry skin with scales • Respiration by lungs -- inside the body (why?) • İnternal fertilization PREPARED BY CANAN ÇERMEN SOURCE: BIOLOGY: CONCEPTS AND CONNECTIONS BY CAMPBELL, REECE, MITCHELL, TAYLOR Compare reptiles and amphibians?? • Amphibians make external fertilization,reptiles internal • Reptiles have tough, scaly skin but amphibians have thin, moist skin • Reptiles have stronger skeleton than amphibians, more efficient lungs and better developed nervous system Birds • • • • • • • • Skin is covered by feathers Legs have scales Strong and light skeleton with air spaces High body temperature for internal regulation(endothermic) High metabolic rate Internal fertilization No teeth and jaws They have horny beaks Mammals • They have hair (furs) which insulates and protects the body • They have mammary glands to provide milk for the young • Differentiated teeth and three middle ear bones • İnternal fertilization • Endothermic organisms • Parental care for the young • Muscular diaphragm helps respiration There are 3 main groups... • Egg laying mammals (female organisms lay eggs. When the eggs hatch, female takes the baby and gives milk) • Pouched mammals • Placental mammals Egg laying mammals • Female lays eggs • When the young hatch, they lick milk secreted by their mother’s mammary glands Pouched mammals • Embryo begins development in the mother’s uterus • Young are born undeveloped • Mother put the young into pouch & young animals attaches its mouth to a mammary gland nipple and gets milk. • e.g: kangroo Placental mammals • Placenta forms both embryonic membrane & maternal uterus wall • In placenta blood vessels of mother come closer material exchange by diffusion • Development is completed in placenta