BIO 101 Diversity Of Animals PDF 5th Feb 2024

Diversity of Animals Alafia, A.O. BIO 101 Learning objectives Students should be able to identify the key evolutionary innovations in the animal phylogeny and the traits that have not change Students should be able to list and describe key features the animals body plan St...

Diversity of Animals Alafia, A.O. BIO 101 Learning objectives Students should be able to identify the key evolutionary innovations in the animal phylogeny and the traits that have not change Students should be able to list and describe key features the animals body plan Students should be able to name synapomorphies of animals Students compare and contrast asymmetry, radial symmetry and bilateral symmetry Differentiate between acoelomates, pseudocoelomate and coelomates, how they are evolutionarily related with examples Differentiate between protostomes and deuterostomes GENERAL FEATURES OF ANIMALS Animals are a diverse group of organism ranging from small minute sponges to large whale, mammoth and Lions They share some major characteristics in common They are heterotrophs They are multicellular Their cells do not have cell wall Movement for most is not restricted They encompass diverse habitat Mainly reproduce by sexual means Patterned embryonic development Cells are organized into tissue They store energy as glycogen and not as starch Posses nervous and muscular tissues Characteristics of Animals Body symmetry: Asymmetrical, radial symmetry, bilateral symmetry Nature of coelom: Coelomate, acoelomate Arrangement of cells of embryonic layers: Diploblastic & triploblastic Notochord: Chordate, non-chordate Patterns of organ systems: Digestive system (incomplete & complete framework), circulatory system (open & closed type), reproductive system framework Segmentation: External & internal segments with serial repetition of some organs Levels of organization: Cellular level, tissue level, organ level & organ framework level Division in Animal is based on Tissues Symmetry Body cavity Body plan Development DIVISION BASED ON TISSUE ORANIZATION METAZOANS (MULTICELLULAR ORGANISMS) ARE DIVIDED INTO TWO MAIN BRANCHES PARAZOANS (SPONGES) the simplest animals , they lack defined tissue and organ, They have the ability to disaggregate and aggregate their cells Sponges have cellular-level organization, meaning that that their cells are specialized so that different cells perform different functions, but similar cells are not organized into tissues and bodies are a sort of loose aggregation of different kinds of cells. This is the simplest kind of cellular organization found among parazoans. EUMETAZOANS (Real multicellular animals) (ALL OTHER ANIMALS) have district and well defined tissue Body organization in simple organisms starts becoming more complex with the development of organs and organs systems.  EVOLTUTION IN SYMMETRY Asymmetry ( No Symmetry ) Sponges lack defined symmetry Radial Symmetry- Hydrozoa Body parts arranged around central axis Can be dissected in 2 dimensional planes Bilateral Symmetry e,g Insects, man Body has left and right halves that are mirror images Only sagittal plane bisects the animal into two equal halves Digestive system complete Incomplete Complete Incomplete Evolutionary Trend in Body cavity Acoelom (No Coelom) e.g Platyhelminthes, Flatworms No cavity, Pseudocoelom (False Body Cavity) e.g Round worm (Ascaris) Coelom (True Coelom) e.g Earthworm  Advantages of coelom and psuedocoelom The reproductive and digestive organs can evolve more complex shapes and functions. The gut tube and other organs are cushioned and thus better protected. Can act as hydroskeleton providing support and rigidity for the soft animal. The activities of the suspended gut can take place undisturbed by the  EVOLUTION IN CEPHALIZATION Cephalization is considered an evolutionary trend, whereby nervous tissue, over many generations, becomes concentrated toward one end of an organism. This process eventually produces a head region with sensory organs. this led to the formation of a highly sophisticated brain first observed in arthropods, cephalopods molluscs and vertebrates Evolutionary trend in body plan Protostomes or “First Mouth Animals” During their embryonic development the mouth forms first and the anus second. Deuterostomes: “Second Mouth Animals” During their embryonic development the anus forms first and the mouth second. Deuterostome Protostome Evolution in
Segmentation Segmentation in biology refers to the division of some animal and plant body plans into a series of repetitive segments. i. this similar repeated units permit larger organisms ii. in annelids (segmented worms), segments are similar form fluid filled compartments that can be stretched or compressed separately-- worm locomotion iii. segmentation permits specialization of different segments Allows redundant organ systems in adults such as in annelids Allows for more efficiency and flexible movement because each segment can move independently Evolution of nervous system Neurons in metazoans were electrical signalling cells Action potential occurred in Eukaryotes Simple nerve net in acoelomate More complex nerve net with simple nerve cords in Ctenophores (comb jellies) when some animals started to live a mobile lifestyle and eating larger food particles externally ,they developed ciliated epithelia, contractile muscles  Evolution in SKELETAL MODIFICATION Sponges have internal skeleton which is composed of collagen and siliceous structures From legged gaits to specialized mode of locomotion e.g bipedalism (two legged gait) Changes in the shoulders, backbone, pelvic girdle, legs and change in dentition Modification of hands leading to increased manipulative skills Less reliance on sense of smell, more reliance on enhanced daytime vision From specialized to omnivorous eating habits Brain expansion and reorganization.- This trend began with among mammals generally but accelerated during homonid evolution Characteristics of Selected animal groups PYHLUM PORIFERA - SPONGES No definite symmetry At the cellular level of organization with specialized cells that perform different functions They are sessile No nervous system Mainly aquatic filter feeders Reproduce sexually or asexually; they are generally hermaphoditic  The body of a sponge is a collection of a few different types of cells loosely arranged in a gelatinous matrix called a 'mesohyl', mesoglea or mesenchyme. Cells includes Choanocytes Pinacocytes Amoebocytes Lophocytes Importance of Sponges They are important in nutrient cycle of coral reefs They remove excess nitrogen from coral reefs They are also used in automobile industries. The skeleton is used for bathing, polishing in automobile industries and also for decorative purposes.  PHYLUM CNIDARIA Cnidarians encompasses more than 9,000 species, including corals, hydras, jellyfish, Portuguese man-of -war, and sea anemones. Mainly marine, and a few species inhabit fresh water. all cnidarians exhibit radial symmetry—that is, similar body parts radiate from a central mouth Diploblastic  Digestion: begins in the gastrovascular cavity (GVC) and is completed in food vacuoles, undigested waste exits out the mouth (intracellular), no anus present Excretion: GVC also functions in the exchange of nitrogenous waste through diffusion Respiration: the exchange of gases (O2 & CO2 ) also functions through diffusion of the GVC Reproduction: GVC functions to release the gametes (egg and sperm cells) Skeletal & locomotion: support and movement are aided by a hydrostatic skeleton (the GVC fills with water)  They usually have specialized stinging cells -cnidocyte - whole cell nematocyst – stinging capsule within cnidocyte Cnidarians lack internal organs and they do not have digestive, circulatory, or respiratory systems. Secretions from endoderm cells digest food within the central body cavity and endoderm cells also distribute nutrients and dissolved oxygen to all parts of the body IMPORTANCE OF CNIDARIANS scientists have discovered many chemical compounds in Cnidarians that can be used to treat cancer and other illnesses They provide an important habitat for a huge number of commercially fished species, including crustaceans and other invertebrates, fish, algae, seaweed and more. These coral reefs also have a huge economic impact due to tourism as well, as people flock to the reefs for snorkeling, diving and other activities. There is also a large worldwide trade in coral for aquariums and jewelry, but much of this has resulted in the destruction of many of these resources. PHYLUM PLATYHELMINTHES Nervous system consists of a pair of anterior ganglia with longitudinal nerve cords connected by transverse nerves. Excretory system of two lateral canals with branches bearing flame cells (protonephridia). Lacking in some. Respiratory, circulatory and skeletal systems lacking. Monoecious or hermaphrodites. Well developed gonads, ducts and accessory organs. There is internal fertilization. Development is direct in free swimming forms. Complicated life cycle involving several hosts in many internal parasites PHYLUM PLATYHELMINTHES : FLATWORMS Triploblastic-Three germ layers Bilateral symmetry with definite anterior and posterior ends Have only one internal space, the digestive cavity They lack coelom or pseudoceolom. They are termed acoelomate animals. Acoelomates have reached the organ level of organization. Body flattened dorsoventrally. Oral and genital apertures on ventral surface PHYLUM ARTHROPODA TRIPLOBLASTIC BILATERAL SYMMETRY SEGMENTED ANIMALS MOST DIVERSE BOTH AQUATIC AND TERRESTRIAL