General Zoology Lecture Notes 2022 PDF

LECTURE NOTES: GENERAL ZOOLOGY (2ND SEM MIDTERM 2022) 1. Zoology:- ( zoon – animal; logy – study – the study of animal. AIM: To understand the life of animals. Animal Life – the sum total of all the properties of animals and animal population & their habitat as well as their characteristics. I. Stru...

LECTURE NOTES: GENERAL ZOOLOGY (2ND SEM MIDTERM 2022) 1. Zoology:- ( zoon – animal; logy – study – the study of animal. AIM: To understand the life of animals. Animal Life – the sum total of all the properties of animals and animal population & their habitat as well as their characteristics. I. Structural Zoology – deals with structures: 1. Morphology ( morpho – form ) – the study of structures as to form and shape especially viewed as a whole. 2. Anatomy ( ana – up, tomy – cut ) – the study of the different structures of organisms especially revealed through dissection. 3. Histology ( histos – tissues ) – the study of microstructures and functions of tissues. 4. Cytology ( kytos – hollow ) – the study of structures and functions within the cell. II. Developmental Zoology – deals with development: 1. Embryology - the study of growth and development within the fertilized egg. a. Homologous structures – structures having the same embryonic origin but different functions. Ex: arms of man, wings of aves, fins of fishes. b. Analogous structures – structures having different embryonic origins but the same functions. Ex: lungs of man, gills of sharks and bony fishes all function for respiration but their embryonic origins are different. 2. Ontogeny – study of the development of the individual. 3. Genetics – the study of heredity and variation. III. Functional Zoology: 1. Physiology ( physis – nature ) – the study of living processes or functions within animals. 2. Animal behavior regards to stimuli: stimuli – factors in the environment which cause an organism to respond. ✓ Irritability – the capacity or ability of an organism to respond or react to stimuli. TAXIS (animals) or TROPISM (plants) the automatic directing towards or away from the source of the stimuli. The reaction may be positive or negative.. Types of taxis: ✓ Thigmotaxis : response to contact or pressure or touch. Geotaxis: response to gravity ✓ Thermotaxis: response to temperature Rheotaxis: response to air or water current. ✓ Heliotaxis: response to temperature Hydrotaxix: response to water. ✓ Phototaxis: response to artificial light. Chemotaxis: response to chemicals. ✓ Galvanotaxis: response to electricity. Chromotaxis: response to color. IV. Systematic Zoology or Taxonomy – the study of the systematic classification of animals and Zoology may also be subdivided according to animal subject of study as follows: 1. Protozoology – the study of one-celled animals. 2. Ichthyology (ichthyo – fish) – the study of fishes. 7. Herpetology (herpeton – reptiles) – the study of reptiles. 3. Entomology (entomo - insect) – the study of insects. 8. Ornithology (ornis – bird) – the study of birds. 4. Conchology (konche - shell) – the study of shells. 9. Helminthology – worms with special reference to parasitic forms. 5. Parasitology – parasitic organisms 10. Malacology (mala – soft)– the study of mollusks or soft-bodied animals. 6. Mammalogy – (mamma – breast ) – the study of mammals or animals that feed their young by means of the mammary gland. V. Distributional Zoology – deals with distribution. 1. Zoogeography – the study of the distribution of animals in space (air, water or land ). 2. Ecology – study of the relations of animals to their environment. a. Convergence – a condition whereby different classes of groups of animals assume the same shape or form due to similarities in environment. Ex; pisces – fishes ( fish-like), reptilia – ichthyosaurus ( fish-like ), whale (fish-like). b. Divergence – a condition whereby the same class of animals assume different shapes or forms due to difference in environment. Ex: Mammalia: water – whale, land – man, air, bat. VI. Historical Zoology – deals with history. 1. Paleontology – the study of fossils or remains of animals and plants and their distribution in time. 2. Phylogeny – the study of the development of a group or race. 3. Evolution – the study of the origin and differentiation of animal life. VII. Economic Zoology – the study of the economic values of animals. VIII. Medical Zoology: 1. Parasitology – ( para – beside; sitos – food ) – the study of parasites or organisms that live that live. 2. Pathology – the study of the nature, symptoms and causes of diseases. ◼ Life: the sum total of all bodily activities of organism. ◼ Theories on the origin of life: 1. Divine or Special Creation Theory – life originated from a supernatural power whom we call God. 2. Abiogenesis or Spontaneous Theory – ( Aristotle ) – life originated from non-living things. 3. Cosmozonic or Interplanetary Theory – life originated from outer planets in the form of a resistant spore propelled by radiation pressure, reached the earth and started the first form of life. 4. Philosophical Theory of eternity – life has no beginning and no end. 5. Marine Theory – life originated from the sea. 6. Naturalistic or Evolutionary or Physico-chemical Theory – life came about as a result of a chain of chemical reactions that gave rise to a mass of living protoplasm which then gradually modified. 2. Chemical Composition of Living Things : Chemical Composition: Only 6 out of 92 naturally occurring elements play an important role in life. ◼ Major elements: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur (C,H, O, N, P, S) ◼ Other essential elements for life: Ca, Na, K, Mg, and Fe ◼ When elements are combined with Carbon, these form an organic molecule producing a living substance or protoplasm. Carbon is the element that life on earth is based upon. ◼ ORGANIC COMPOUNDS: Classes of Organic Molecules: includes carbohydrates, lipids, proteins and nucleic acids  ◼ 1. Carbohydrates: most abundant organic compounds and the greatest source of energy. The simplest carbohydrate is glucose: C6H12O6 1.1. Monosaccharide: Simple sugars (C6H1206)) are building blocks of carbohydrates. Glucose: dextrose or blood sugar Fructose: fruit sugar Galactose: mother’s milk sugar 1.2. Dissaccharides: or double sugars composed of two simple sugars bonded together. Chemical formula: C12H22O11 Examples: Maltose (malt sugar in barley used to make beer), Sucrose (table sugar), Lactose (milk sugar) ➔These sugars must be broken down into simple sugar to be used by organisms and become a good source of energy. 1.3. Polysaccharides : comprise many complex carbohydrates or thousands of glucose or simple sugars. Examples: starch (chief carbohydrate storage in plants), Cellulose (an insoluble structural polysaccharide in plants cell walls), Fructans (storage products in leaves and stems), Glycogen - the chief carbohydrates product storage of animals. 2..Lipids: fats that contain carbon and hydrogen. These organic molecules include 1. fats 2) oils 3) waxes 4) steroids (complex lipids) 5. phospholipids ✓ They function as chief energy storage of food materials, as waterproof coatings, and as chemical messengers ✓ They are considered as water insoluble but soluble in organic solutes. 2.1. Triglycerides: are fats and oils. Types of fats: 1) Saturated fats or animal fat (solid at room temperature, They form straight chain polymers in which fatty acids are packed very closely and include fats such as bacon fat) 2) Unsaturated fat or vegetable oil (liquids at normal room temperature, these are the oils we usually use. 2.2. Waxes: are insoluble in water. Useful as waterproof coatings for organisms, as a structural component of cell walls. 2.3. Phospholipids: are water-soluble while the rest of the molecules are insoluble in water. The cell membrane surrounding every cell are made of a bilayer of phospholipids. 2.4. Steroids: consist of the female and male reproductive hormones. Testosterone: responsible for the development of male secondary sexual characteristics. Estrogen: responsible for the development of female secondary sexual characteristics. 3. Proteins: are the building and replacement materials of our body, especially important when we are growing. It is the most abundant and complex compound in the living cells. : Chemical component CHON. Proteins have many roles in cells, they include: 3.1. Structural proteins: are form cell parts found in skin, nails, and hair. 3.2. Regulatory proteins: control cell processes such as cell reproduction or cell division 3.3. Enzymes: facilitate many chemical reactions; they do this by lowering the amount of energy needed to start the reaction. 3.4. Hormones: chemical messengers like testosterone and estrogen for the secondary sexual development of male and female 3.5. Transport proteins: Carry other substances around cells or from cell to cell like hemoglobin in human blood. 4. Nucleic Acids: large organic molecules whose chief function is to carry the genetic information in the form of a code. Types: 4.1. Deoxyribonucleic acid (DNA): double helix; stores genetic information; provides the genetic code; transmit hereditary information from cell to cell and from generation to generation; contain nitrogen bases: Adenine, Thymine(unique in DNA), Guanine, Cytosine, 4.2. Ribonucleic acid (RNA): single helix; contain nitrogen bases: Adenine, Uracil (unique in RNA), Guanine, Cytosine, 4.3. Adenosine triphosphate (ATP): known as the energy molecule; it provides immediate energy for the activities of every living cell. ◼ INORGANIC COMPOUNDS: Inorganic Compounds and Molecules: includes water, minerals, acids, bases and salts 1. Water: (H2O): universal solvent, the lubricant of our functionality; has a high heat of vaporization ✓ Water comprises 60 – 90% of the protoplasm (colloidal and liquid substance of which cells are formed, the physical basis of all living organisms) ✓ Our body is made up of 70% water by weight; Our brain is about 70-80% water; Absence of water, digestive enzyme will be dry ✓ Water molecules exhibit a high degree of cohesion (tendency of water molecules to cling to each other) and adhesion (tendency of unlike molecules to cling to each other) ✓ Water exhibits a high surface tension (the tendency of molecules at the surface of a liquid to cohere to each other and not to the air above. 2. Vitamins: Mineral elements are in the form of salts and combined with protein. Vitamins : are organic compounds needed in minute amounts and usually are of plant origin. ✓ They are required for normal growth and development. These are not manufactured by animals. Vitamins can be grouped into two: 1) Fat soluble vitamins: A, D, E, K – are stored in your body for a while, a few days, some up to six months 2) Water soluble vitamins: B (Carmitine- heart vitamins), C (Ascorbic acid), B1 (thiamin), B2 (riboflavin) B6 (pyridoxine), B12 (cobalamine), Niacin, Biotin – travel through your bloodstream and when not needed excreted when you urinate. Vitamin A: Functions: maintains the integrity of epithelial tissue; Contains the visual purple of the retina; vitamin for the eyesight Sources: liver, egg yolk, milk, cream, green and yellow vegetables. Vitamin D: Functions: promotes growth of bones and teeth; Sources: margarine, butter milk, cheese, liver Vitamin E: Functions: relates the cellular respiration; Prevents hemolysis in RBC; for the formation of RBC Sources: oil from wheat and corn, soybeans, mayonnaise, salad dressing  Vitamin K: Functions: maintains the prothrombin level in the blood plasma; for blood clotting Sources: liver, dark green leaves, wheat, beans, vegetable oil, tomatoes and egg yolk 3. Minerals: Minerals are needed by the body in minute amounts to perform important function. ✓ They comprise about 4 - 6% of the total body weight of man; may be grouped into two: Macro & Microminerals Macrominerals and Functions Microminerals and Functions Calcium (C) Essential for the formation of bone and teeth Manganese (Mn) Activates enzymes Phosphorus (P) PH regulation & sugar metabolism Copper (Cu) Associated with iron function Potassium (K) For the activity of skeletal & cardiac muscles Iodine (I) Synthesis of thyroxine Sulfur (S) Maintains protein structure Cobalt (Co) Constituent of Vit. B12 for normal function of cell Sodium (Na) Maintains fluid and acid-base balance Fluorine (F) Food in bones & teeth, thyroid glands & skin Chlorine (Cl) Maintains fluid & electrolyte balance Chromium (Cr) For glucose metabolism Magnesium (Mg) For normal nerve impulses & muscular relaxation, Selenium (Se) Reduces or prevents Vit. E deficiency used for production of enzymes Iron (Fe) Major constituent of hemoglobin Nickel (Ni) Associated with Fe function Zinc (Zn) Cellular functions & regulation of enzymes Tin (Sn) Maintains prote4in structure, oxidation reduction Silicon (Si) Enhances bone calcification 4) Basic Food Groups : the five basic food groups are: dairy products, fruits, vegetables, grains, meat group 5) Acidity and Alkalinity: a. Neutral Solution: the number of H+ in a solution equals the number of 0H-, the solution is said to be Neutral (pH 7) b. Acidic Solution: if the number of H+ in a solution is greater than the number of 0H-, the solution is an Acid (pH -7). Tend to have a sour taste and in concentrated forms are highly corrosive c. Basic Solution: the solution contains more 0H- than H+ , it is defined as Base (pH 7+).Tend to feel slippery (soapy) and have a bitter taste. The pH Scale: Scientist developed the pH Scale which ranges from 0 – 14. A solution with a pH of 0 is very acidic A solution with a pH of 7 is neutral ; A solution with a pH of 14 is very basic; pH solution can be measured with litmus paper 3) THE CELLULAR STRUCTURES, PROCESSES, AND FUNCTIONS THE CELL THEORY IS STATED AS FOLLOWS: 1. All living things are composed of one or more units called cells. 2. Cells are the basic units of life and all the chemical reactions of life occur in cells. 3. All cells arise from preexisting cells through cell division. THE CELLS OF THE HUMAN BODY 1. The largest cell in the female body is the egg cell, visible to the naked eye as a speck of translucent dust. 2. The sperm cells are small but, unlike red blood cells, a huge part of their size is made up of DNA. THE TWO DIFFERENT TYPES OF CELLS: 1. Prokaryotic cells – do not have the membrane-enclosed nucleus. Ex. (bacteria) = unicellular. (0.1 – 10 um) 2. Eukaryotic cells - have definite nucleus and cell organelles. Ex. (plants, animals, fungi) = multicellular (10-100 um) THE COMMON CELL ORGANELLES 1. Cell Membrane – all surface of cells lies the plasma membrane. - barrier between the interior and exterior environment of the cell, regulates the coming in and out or flow of substances of the cell. - it is a semipermeable that selectively controls the entrance and exit of materials - The lipids and proteins of the membrane are always in motion, like the surface of a soap bubble. ➔Cell Wall – outermost structure of plant cells which consists of cellulose and other substances. Its function is to give rigidity and strength to the plant cells. 2. The Nucleus– controls the central part of the cell; contains all the genetic (hereditary) information in the form of DNA. - within the nucleus is the nucleoplasm (the protoplasm inside the nucleus of the cell. - Chromosomes are threadlike bodies which are only visible during cell division – bear the genes, the basic units of heredity. - DNA and protein make up a chromosome; DNA contains the genetic blueprint of the cell - Nucleolus – small dark-staining region which has no membrane, is responsible for ribosome production RNA and synthesis of protein Other Parts & Other Special Cell Processes 1. Flagella (long cytoplasmic projections for propulsion) & Cilia (shorter and more numerous and move in waves) = movable hairlike structures - functions either in the moving of the cell or moving liquids or small particles across the surface of the cell. 2. Pinocytosis means, “cell drinking”; certain amount of liquid are taken by the cell. 3. Phagocytosis means, “cell eating”; solid particles are ingested by the cell. 4. Plasmolysis – is the shrinking of the cell’s cytoplasm by osmosis due to loss of protoplasm (dried fish) 5. Hydration – is the entrance or adding of water to the living cell resulting to the bulging of the cell. 3. The Cytoplasm – the liquid portion of the cell - the substance between the cell membrane and the nucleus - food nutrients are generally received, processed and used in the cytoplasm, it is also in this part of the cell where waste are removed - it is composed of two main components: Cytosol and Organelles 3.a. Cytosol (literally, “cell solution”) – is jellylike mixture that consists mostly of water (70%), along with proteins, carbohydrates and other organic compounds. 3.b. Organelles – are membrane bound structures that work like miniature organs, carrying out specific functions in the cell.  The Common Cell Organelles: on the table summarizes the cell organelles and functions common animal cells: Organelles Functions Animal cell Cell walls Support and protect the cytoplasm consists of cellulose X none Cell membrane Controls the flow of materials in and out of the cell ✓ check Endoplasmic Network or interconnected flattened hollow tubules and channels. Synthesize carbohydrates, lipid, ✓ check reticulum protein. Two types: Smooth ER – manufactures lipids, detoxify certain poisons, transports CHO, lipids, other non-proteins Rough ER – is where proteins CHON are synthesized destined to be secreted out of the cell Ribosomes Responsible for protein synthesize; consist of molecular complexes of ribosomal RNA and proteins ✓ check Mitochondria The “ power house” of the cell (release energy from food molecules); location where chemical energy in ✓ check the form of ATP is produced. Lysosomes Acts as a digestive system of the cell; Digest foreign particles that enter the cells ✓ check Golgi apparatus Collection of flat sacs that transport proteins from Rough ER to the outside of the cell; Selects several ✓ check chemical products for membrane repair and transport of materials Vacuoles The storage of materials ( food and waste ) in the protoplasm; give cell shape(sap vacuole); store waste ✓ check product to be released later (contractile vacuole) ; Digest structure that stores food (food vacuole) Centriole Aids the distribution of chromosomes during cell division in animal cells. ✓ check The Cellular Reproduction/ Cell Division: ▪ Mitosis Promoting Factor (MPF) – is a protein triggering agent for cell division. Cell Division is continuous and is needed to replace those cells that have aged or died. Each dividing cell is called a mother or parent cell, and its descendants are called daughter cells.. 3 Types of cell division: 1. Unicellular cells – undergo direct cell division or amitosis – a simple process involving membrane growth by duplicating (replicating) its genetic material. 2. Multicellular cells undergo indirect cell division that occurs only in the somatic cells (body cells) called mitosis. The process involved in the cell division of somatic cells is called Mitotic Cell Division. 3. Meiosis – development and maturation of gametes(male: sperm cell, female: egg cell) or reproductive cells = Meiosis I & II The process involved in the cell division of reproductive cells is called Meiotic Division I and Meiotic Division II The Mitosis Cell Cycle: 1. 1st interphase or G1 phase– chromosomes single stranded & uncoiled = cell growth. 2. S phase – DNA replication, genetic materials replicated 3. G2 phase – preparation for mitosis, sister chromatids are formed followed by mitotic division. 4. Mitosis is divided into four stages: 1)Prophase – 2 centrioles become visible and move to opposite poles of the nucleus. - Each chromosomes consist of two strands or chromatids joined together by small body called centromere - 2 centrioles move apart and fiber-like structures appear, This arrangement is called central spindle or division figure. 2) Metaphase – the chromosomes migrates and aligns at the equator of the spindle, the sister chromatids divides/separates into 2 3) Anaphase: centromeres uncoupled and begun moving toward opposite pole of the spindle. 4) Telophase – new nuclear membranes forming chromosomes become longer & thinner and less dense 5) Interphase – nuclear membranes complete, chromosomes no longer visible = cytokinesis complete Cleavage furrow – separates the 2 daughter cells, same chromosomes as the mother or parent cell ◼ The cell cycle is divided into 2 phases: the interphase ( 30 min- 1hour and Mitotic phase ( occupies small portion only of the cell cycle ) ◼ Mitosis comes from the Greek word “mitosis” meaning “thread” ◼ Crossing over is the exchange of genes between pairs of homologous chromosomes occur during prophase 1 ◼ Crossing over changes the combination of genes on a particular chromosomes = results to variations of genes ◼ Each dividing cell is called a mother or parent cell, and its descendants are called daughter cells. 4. THE ANIMAL TISSUES, STRUCTURE, AND FUNCTION The Four Types of Tissues: Epithelial, Connective, Muscle, Nerve Tissues 1. Epithelial Tissues - generally occurs as sheets of tightly packed epithelial cells, it covers the outside of the body (epidermis) and lines organs and cavities inside the body (Endothelium) Function: barrier protecting the body from mechanical injury, invading microorganisms, ultraviolet light, and loss of fluid (dehydration) Absorb nutrients (lining of the intestine), lubricate surface (mucous membrane of the throat), secrete chemicals for digestion and regulation (glands) 2. Connective Tissues - generally cells are scattered throughout an extracellular matrix, matrix may be liquid, solid, or jelly-like. Function: main function is to bind and support other tissues: cartilage, bone, and blood. ✓ Loose Connective Tissues: collagenous fibers do not tear easily; elastic fibers resist stretching, rubbery; adipose tissue which store fat; blood, matrix is a liquid (plasma). ✓ Fibrous Connective Tissues: dense, tightly woven and arranged in parallel bundles: tendons, ligaments, cartilage, bone, 3. Muscle Tissues - three basic types: Skeletal – voluntary muscle and striated – under conscious nervous control Smooth – involuntary muscle and lacks striations – under autonomic nervous control or visceral muscles (intestine, uterus, stomach, urinary bladder, iris of eye, and in the base of the hairs) Cardiac – involuntary muscle and striated like skeletal muscle – under the control of autonomic nervous system (unconscious control) 4. Nerve Tissues - are composed primarily of nerve cells known as neurons. Function: responsible for the conduction of nerve impulses. Nerve cells must last for life because they cannot be replaced.  ◼ Neurons- specialized cells the basic structural unit of the nervous system that transmit messages throughout the body. ◼ Principles Parts of Neurons: Cell body- is found in the protoplasm which is the living part of the neuron. Dendrites – are clusters of nerve fibers which carry messages towards the cell body. Axon – is a long, slim, tube-like extension which carries messages away from the cell body. 5. INVERTEBRATE INTEGUMENT:: Integument ( skin ) – outer covering of the body. Functions of the Integument: 1. Covering and protection from mechanical injury and entrance of foreign materials or bodies; protective coloration. 2. Secretion. 3. Excretion 4. Sensation. 5. Respiration – frogs use the skin, which is highly impregnated with blood vessels, as an accessory organ of respiration. 6. Absorption – in the frog, the stratum corneum is thin thus easily allow entrance of water. 7. Regulation of body temperature. Homiothermous animals – warm-blooded animals or those with a regular body temperature. Ex. Aves and Mamalia Poikilotermous animals – cold-blooded animals whose body temperature closely follows that of their environment. INVERTEBRATE INTEGUMENT: Protozoa – with delicate cell membrane. Ex. Amoeba - with firm and elastic pellicle. Ex. Paramecium. All multicellular animals are provided with a tissue – the epidermis: 1. Coelenterata: the epidermis is made up of a single layer of cells found in animals with a soft body 2. Annelida: epidermis contains a delicate non-cellular cuticle secreted by the epidermis, like in the earthworm. 3. Platyhelminthes: epidermis contains a resistant cuticle in flukes, tapeworm and especially Nemathelminthes: roundworms like ascaris 4. Arthropoda: epidermis secretes a protective external skeleton, called epidermis chitin (insects) and shrimps; or Mollusca: shells in snails and bivalves. Vertebrates:The skin of the frog consists of two layers: 1. Epidermis – consists of two layers: 1.a. Stratum corneum – non-living, stratified layer of squamous epithelial tissue. In land vertebrates, the outer layer is hardened or cornified and is constantly removed (ecdysis or molting) 1.b. Stratum germinativum – the living and growing layer of stratified columnar epithelial tissue. The cells continuously divide and replace the constantly shed off stratum corneum of the skin. 2. Dermis – consists of two layers: 2.a. Stratum laxum or spongiosum – connective tissue fibers which are loosely arranged, where cutaneous glands are situated, thus giving a spongy appearance. 2. b. Stratum compactum – connective tissue fibers which are compactly arranged. ➔ Glands present – are mostly mucous and poison glands. 6. SKELETAL SYSTEM: skeleton – any hard portion of the body which may either be located externally (exoskeleton) or internally (endoskeleton) Types of skeleton as to location: 1. Exoskeleton – ex. Carapace and plastron of turtles, feathers and hair. 2. Endoskeleton – ex. Cartilage and bone Functions of the Skeletal System: 1. Framework of the body; Gives physical support; Protection; Muscle attachment; Leverage for locomotion; Prevents the loss of body fluid; Manufacture of red blood cells in the bone marrow of long bones. Invertebrate skeleton 1. Protozoa – may be calcareous, siliceous or glassy or of organic substance. 2. Porifera – made up of microscopic internal rods called spicules which maybe siliceous or calcareous or made up of spogin fibers (bath sponge) 3. Coelenterata, brachiopoda, echinodermata and mollusca – skeleton made up mainly of lime which grows , becoming thicker with age. 4. Arthropoda ( crustacean and insects ) covered completely by jointed exoskeleton of organic materials containing a nitrogenous polysaccharide called chitin. Types of bone according to formation:  1. cartilage bone – starts first as a cartilage and later hardens into bone.  2. membrane bone – develops immediately into a hard bone. Types of endoskeleton to position in the body:  1. axial – endoskeleton which is located at the center or axis of the body. Ex: skull, vertebral column, sternum, hyoid and jaws.  2. appendicular – endoskeleton which is located laterally or at the sides of the body. Ex. Pectoral ( shoulder) and pelvic, bones of the forelimbs and hindlimbs. 7. MUSCULAR SYSTEM: Myology – the study of muscles: Invertebrate Musculature: Protozoa – with specialized parts called organelles, the function of which is compared to an organ of metazoans. 1. Pseudopodia ( false feet ) – the animal makes use of protoplasmic streaming in contracting or extending its body. Ex. Amoeba 2. Myonemes – specialized contractile fibrils. Ex. Stalked vorticella 3. Cilia – hair-like structures that propel the animal in water. Ex. Paramecium 4. Flagella – whip-like structure that propels the animal in water. Ex. euglena 5. Coelenterata – with epithelio-muscular cells which are provided with contractile fibers at their base. 6. Platyhelminthes ( flatworms ) – muscle fibers are in three planes. 7. Annelida (earthworms) – with two layers of muscles. 8. Mollusca – with a ventral muscular foot that is modified for crawling, burrowing, swimming, attaching and grasping.  9. Echinodermata and Arthropoda – muscles are alternately attached to the inner surface of the endoskeleton to move the jointed legs and segments of the body. 10. - Nemathelminthes – roundworms like ascaris 8. DIGESTIVE SYSTEM: Digestion – a physical as well as a chemical process of changing food from insoluble to soluble form. Food must be changed into a simple liquid form to facilitate its transport by the blood. FUNCTIONS – primarily for digestion The process of digestion includes several processes like: 1. Ingestion – taking in of food through the mouth. 2. Digestion – changing of food from solid to liquid state. 3. Absorption – passage of simple food from the digestive tract to the blood and lymph. 4. Circulation – transport of the absorbed food to the tissues of the body. 5. Assimilation – incorporation of absorbed simple food as part of the protoplasm. 6. Egestion – passing out of the undigested food or residue through the anus. Invertebrate Digestive System 1. Protozoa – provided with organelle, the food vacuole, which serves as an organ for digestion. Digestion is intercellular ( takes place within the cells ) 2. Porifera – with schizocoel and choanocytes - digestion is intracellular. 3. Coelenterata – with gastrovascular cavity, which serves as an incomplete digestive tube ( a type of digestive tube with only one opening which serves for both entrance and exit; with a mouth but no anus ). Digestion is both intracellular and extracellular ( type of digestion that takes place outside the cell, usually within the digestive cavity ). a. Intracellular – smaller food particles are absorbed into the vacuoles of the cell of the gastrodermis. b. Extracellular – the glandular cells of the gastrodermis secrete enzymes into the gastrovascular cavity where the digestion of the large particles takes place. Platyhelminthes – has an incomplete, branched digestive tube; an exception is the tapeworm which has no digestive tract. ▪ Tapeworm have no digestive tract and absorb food directly through their body walls ▪ The head of the tapeworm is called scolex – structure that contain suckers and hooks ▪ The scolex is used to attached their bodies into the intestinal wall of their host ▪ Diphylobothrium lutum (fish tapeworm) Hymenolopis Nana (dwarf tapeworm) ▪ Taenia Saginata (beef tapeworm) Taenia solium (pork tapeworm) ▪ Echinococcus granulosus (hydatid cyst disease) Echinococcus Multicularis (alveolar cyst disease) Nemathelminthes – has complete digestive tube ( type of digestive tube with a mouth for entrance and anus for exit. ▪ Nemathelminthes – roundworms like ascaris ▪ Annelida – a typical example of an invertebrate with a complete digestive tube. - digestion is extracellular. Parts of the digestive tube of the earthworm: 1. Mouth – the anterior opening which is provided with prostomium or lips used for grasping the food. 2. Buccal cavity- 3. Pharynx muscular structure which facilitates sucking in of food. 4. Crop – an expanded portion of the esophagus which serve for temporary storage of food. 5. Gizzard – very muscular structure which through its grinding motion with bits of sand present in it that act as an abrasive material ( aids in cutting the food into smaller bits ). 6. Intestine – place where digestion of food takes place; digestion is hastened by the secretion of enzymes secreted by the intestinal glands. Enzymes present: a. amylopsin – acts on carbohydrates b. pepsin – acts on protein c. lipase – acts on fats d. cellulase – acts of cellulose 7. Anus – the terminal opening of the digestive tube, an exit of digestive waste products Mollusca – with a complete digestive tube in some the mouth is provided with horny teeth that rasp off food particles. - digestion takes place in the stomach - absorption takes place in the intestine and residue exit through the anus. Echinodermata – with complete digestive tube ( incomplete in some )- the stomach is usually everted on the food, mucus is secreted, then the stomach with its contents is withdrawn into the body.- large bits are cast out through the mouth.- the intestines is mainly for excretion Arthropoda – with a complete digestive tube - mouth parts are modified appendages and are specialized for various purposes depending upon the feeding habits of the animal ( chewing, piercing, lapping, sucking) Enzymes present: a. amylopsin – acts on carbohydrates b. pepsin – acts on protein c. lipase – acts on fats d. cellulase – acts of cellulose