C8 Part 2

• Coelomate animals


  Triploblastic - having THREE (3) types of tissues called ectoderm, endoderm and mesoderm
• Two main groups of coelomate animals

  • Protostomes - lophophores, molluscs, annelids and anthropods
  • Deuterosomes - echinoderms and chordates
• Protostomes


  • Early embryonic cell divisions are "angled" which is called spiral cleavage
  • In the ball-shaped early embryo, the first indentation (blastopore) becomes the mouth
  • The coelom forms from tissue at the sides of the gut near the blastopore

  
• Deuterostomes


  • The zygote divides symmetrically, this is called radial cleavage
  • The blastopore becomes the anus, the mouth develops from a second opening
  • The coelom forms from outpouchings of the gut wall
• Coelomate invertebrates


  • Lophophores (3 phyla)
  • Phylum Mollusca
  • Phylum Annelida
  • Phylum Arthropoda
  • Phylum Echinodermata

  
• Lophophore


  A characteristic feeding organ possessed by three major groups of animals
• Lophophorate phyla


  • Phylum Ectoprocta
  • Phylum Phoronida
  • Phylum Brachiopoda
• Lophophorates


  • The mouth is always located inside the lophophore ring of tentacles, while the anus lies outside the ring
  • The lophophore tentacles are covered with cilia in a specific arrangement that are responsible for generating a current of water that flows toward the mouth
  • They are sessile animals with a U-shaped digestive tract and no distinct head
• Ectoprocts


  • Colonial animals resembling plants
  • Encased in hard exoskeleton with pores for lophophore extension
  • Mostly marine - reef builders
• Phoronids


  • Tube dwelling marine worms
  • The lophophore will not be coiled whenever threatened
  • Phoronids are elongated and worm-shaped, but the gut loops and ends close to the mouth, instead of passing straight through the body
• Brachiopods


  • Also known as lamp shells, they are sessile, two-shelled, marine animals with an external morphology resembling clams
  • Brachiopods are suspension feeders with a distinctive feeding organ called a lophophore
  • The two halves of the shell are dorsal and ventral rather than lateral as in clams
• Phylum Mollusca


  • Includes snails and slugs, oysters and clams, and octopuses and squids
  • Most molluscs are marine, though some inhabit fresh water and some are terrestrial
  • Molluscs are soft-bodied animals, but most are protected by a hard shell
• Molluscs


  • Have a head (even though not all), a broad and fleshy foot for locomotion, a dorsal shell or a reduced version of one, a mantle, ctenidia (gills) as the respiratory organ, and a radula (a rasping tonguelike structure) for feeding (except in suspension/filter feeders like bivalves)
• Major classes of molluscs

  • Polyplacophora (chitons)
  • Gastropoda (snails and slugs)
  • Bivalvia (clams, oysters, and other bivalves)
  • Cephalopoda (squids, octopuses, cuttlefish, and chambered nautiluses)
• Gastropods


  • Literally means "belly foot", referring to the way a mollusk foot spreads out when it crawls
  • They have coiled shells that function as a backpack, for balancing
• Polyplacophora


  • Slow moving or sedentary grazers, which have eight plates shell covering their dorsal body
  • Their head is reduced, and they lack eyes or tentacles
• Bivalves


  Animals having a "two-valved shell" that includes clams, scallops, oysters and mussels
• Cephalopods


  The swift-moving (squids) and smart (octopus) members of the phylum
• Phylum Mollusca is unique due to their soft body, allowing the members to undergo different modifications with their body plan
• Evolutionary experiments with the molluscan body

  1. Twisting and detwisting of soft bodies (Only in gastropods)

  2. Hiding out, one way or another (Chitons, bivalves, cephalopods)

  3. The cephalopod need for speed (Thick, muscular mantle, jet propulsion, ability to change color and discharge ink)

  
• Annelids


  • Protostome, with bilateral body symmetry, a tubular gut, and they possess segmentation
  • Their habitat includes terrestrial, freshwater and marine
  • Their segments are usually referred to as 'rings'
  • Many of their internal organs such as the metanephridia (osmoregulatory organ) are segmented, while structures like the digestive tract and certain nerves extend throughout the body
• Advantages of segmentation


  A segmented body has great evolutionary potential, because individual parts can undergo modification and become highly adapted for specialized tasks especially locomotion
• Oligochaeta and Polychaeta


  • Possess setae or bristles that project directly from the highly segmented body and are chitin-reinforced, helping in crawling and burrowing

  
• Special adaptations of annelids

  • Leeches (class Hirudinea) have suckers at both ends
  • Polychaetes have fleshy, paddle-like parapods above the bristles
• Rings


  The structures that make up their identity
• Annelids


  • Many of their internal organs such as the metanephridia (osmoregulatory organ) are segmented
  • Structures like the digestive tract and certain nerves extend throughout the body
• Segmentation


  • A segmented body has great evolutionary potential, because individual parts can undergo modification and become highly adapted for specialized tasks especially locomotion
• Oligochaeta and Polychaeta


  • Possess setae or bristles that will project directly from the highly segmented body and it is chitin-reinforced
  • In the soil, it helps in crawling and burrowing

  
• Leeches (class Hirudinea)


  • Have suckers at both ends
• Polychaetes


  • Have fleshy, paddle-like parapods above the bristles
• Earthworms (Oligochaetes)


  • Bear few short setae (oligochaetes) for each segments compared to polychaetes
  • The gut extends through all chambers, from mouth to anus
  • The body is enclosed in a flexible and permeable cuticle that is good for gas exchange
  • Respire through their skins
  • Cuticle is not good for water conservation causing them to be restricted in aquatic and moist habitats
  • Their habit of ingesting dirt particles while scavenging for organic matter makes them valuable tillers of the soil
  • Internal partitions define individual coelomic chambers filled with fluid to provide a hydrostatic skeleton
  • Paired nerve cords extend from the brain to run the length of the body with a ganglion in each segment
  • Circulatory system is closed (blood confined to multiple heart and vessels)
  • Contain an osmoregulatory system of metanephridia, which occur in nearly every segment to regulate the volume and composition of body fluids
  • Hermaphrodites, exchange spermatozoa (sperm)
• Metanephridia


  • Each unit has a funnel (nephrostome) that collects excess fluid and delivers to the bladder which leads to a pore (nephridiophore) that helps excrete the excess water
• Polychaeta


  • Marine worms that are free living, some burrow in the mud near the shore or live inside a tube
  • Their fleshy paddle-liked parapods function in gas exchange and locomotion
  • They have a well developed head with tentacles and palps (feelers)
• Hirudinea


  • Mostly blood-sucking parasites
  • Do not possess any setae or parapodia
  • Instead, anterior and posterior suckers are unique to them
• Arthropoda


  • Largest phylum of animal – More than 80% of living animals are arthropods
  • Most successful organism on earth - Most offspring, Greatest number of species, Most habitats, Fending off threats and competition efficiently, Having the capacity to exploit great amounts / kinds of foods
  • Protostome, with bilateral body symmetry, a tubular gut, and they possess segmentation
• Adaptations that contribute to the success of Arthropoda

  • Segmentation
  • Exoskeleton
  • Jointed appendages
  • Respiratory structures
  • Specialized sensory structures
  • Division of labor
• Segmentation


  • Important because it provides specialization of body regions
  • Specialization causes certain segments to concentrate on certain functions like sensory, feeding, locomotion and reproduction
  • Produce head, thorax, abdomen
• Exoskeleton


  • Provide protection against predators
  • Protection against dessication
  • Disadvantage is the exoskeleton is non living, causing molting to be necessary and this made them vulnerable to predators
• Jointed appendages


  • Appendages (legs) that have joints to facilitate movements
  • A uniformly hardened cuticle at joints restrict movement
  • The appendages are thinner at joints, to ease bending and movement
• Respiratory structures


  • Many aquatic arthropods depend on gills for gas exchange
  • Special tubes called tracheas supply oxygen directly to body tissues from pores on the body surface for terrestrial arthropods
  • Allows high metabolic rates and sustained activity, such as flying