bio chapter 28

• Invertebrates


  • Lack a backbone
  • Account for more than 97% of known animal species
  • Morphologically diverse and occupy almost every habitat on Earth
  • More than 35 phyla identified
• Phylum Porifera


  Sponges

  • Aquatic, mostly marine,
  • sessile as adults,
  • NO nervous, digestive, respiratory, circulatory, or reproductive system,
  • filter feeders,
  • NO true tissue or cephalization
• Porifera


  • Body supported by hard spicules and protein fibers (spongin)
  • Reproduce asexually by fragmentation or budding, or sexually as hermaphrodites with flagellated larvae
  • no gonads! gametes form in mesohyl
  • have choanocytes
• Basal Eumetazoans: Cnidaria


  • Jellyfish, hydra, sea anemones, corals
  • Radial symmetry,
  • diploblastic,
  • aquatic,
  • two adult body forms: sessile polyp or drifting/free-swimming medusa
  • no cephalization (brain)

  
• Cnidaria

  • Sac-like body with gastrovascular cavity,
  • mesoglea - noncellular layer functions as a hydrostatic skeleton
  • flexible, supported by fluid pressure
  • simple nervous system with non-centralized nerve net
• Basal Eumetazoans: Ctenophora


  • Comb jellies: Radially symmetric, diploblastic,
  • transparent medusa-like body
  • moves with cilia, fused into 8 comb-like plates
• Superphylum Lophotrochozoans include...

  • ectoprocts,
  • brachiopods,
  • platyhelminthes,
  • syndermata,
  • annelids
  • molluscs
• Lophotrochozoans


  Some develop a lophophore for feeding, others pass through a trochophore larval stage, and a few have neither feature
• Lophotrochozoans: Ectoprocts and Brachiopods

  • Have a lophophore, a crown of ciliated tentacles around their mouth used for feeding
• Lophotrochozoans: Platyhelminthes (Flatworms)

  • Live in marine, freshwater, and damp terrestrial habitats,
  • many are parasites like flukes and tapeworms,
  • flat shape increases surface area for gas exchange and waste elimination
• Lophotrochozoans: Platyhelminthes

  • Acoelomates
  • have cephalization
  • gastrovascular cavity with one opening, highly branched to digest and distribute nutrients
  • lack respiratory and circulatory systems
  • O2/CO2 exchange is at cell levl
• Lophotrochozoans: Platyhelminthes

  • Examples: Planarians Tapeworms
  • THEY DO HAVE:
  • Digestive system
  • nervous system- centralized collection of nerves
  • excretory system- protonephridia w/ flame cells remove excess water and some waste
  • reproduction system (usually hermaphrodites)
• Lophotrochozoans: Syndermata (Rotifers)

  • Free-living, aquatic,
  • microscopic, cylindrical body,
  • crown of cilia draws in water,
  • jaws grind up food,
  • have a pseudocoelom
  • alimentary canal- digestive tube with two openings (mouth and anus)
  • Parthenogenesis occurs- asexual reproduction; females produce females from unfertilized eggs
• Lophotrochozoans: Molluscs

  • Most are marine, some inhabit freshwater and some snails and slugs are terrestrial
  • Soft-bodied protected by a calcium carbonate shell
  • True coeloms surrounded by mesoderm and complex organ systems
  • Cephalization: yes, except bivalves

  
• Major clades of Mollusca


  • Polyplacophora (chitons)
  • Gastropoda (snails and slugs)
  • Bivalvia (clams, oysters)
  • Cephalopoda (squids, octopuses)
• Molluscs Visceral mass


  Internal organs, well developed organ systems
• Molluscs Mantle


  Secretes minerals that makes shell (if present) for protection, covers visceral mass, & makes pearls!
• The basic body plan of a mollusc has three main parts: muscular foot, visceral mass, and mantle
• Organ systems of molluscs


  • Digestive system: complete with a strap like radula to feed
  • Excretory system: more complex than flatworms
  • Respiratory system
  • Circulatory system
  • Reproductive system
  • Nervous system: some primitive and some have central brain (Cephalopods)
• Respiratory and circulatory system in Molluscs

  • Have specialized gas exchange surface – Gills or simple lungs (large surface, thin and moist, highly vascularized, protected)
  • Most have open circulatory system with 2-chambered heart

  
• Reproduction in Molluscs


  • Most have separate sexes
  • Most aquatic species with trochophore larvae - larva disperses marine snail to new locations
• • Molluscs are the animal group with the largest number of documented extinctions
  • The most threatened groups of molluscs are: freshwater bivalves, including pearl mussels, and terrestrial gastropods, including Pacific island land snails
  • These molluscs are threatened by habitat loss, pollution, competition or predation by non-native species, and overharvesting by humans
• Lophotrochozoans: Annelida - segmented worms

  • About 16,500 species
  • Some marine species have trochophore larvae
  • Much less diverse than Mollusks, but important to the ecosystem
  • ex. earthworm
• Lophotrochozoans: Annelida body

  • Segmentation (metamerism)- External & internal features are repeated
  • Soft body- True coelom acts as hydrostatic skeleton
• Well-developed organ systems of Annelids

  • Digestive
  • Closed circulatory (with a heart and blood contained in vessels)
  • Excretory system consists of a pair of metanephridia
  • Nervous system with a ring of fused ganglia
• Gas exchange in Annelids


  Occurs across the moist body surface
• Types of Annelids


  • Earthworms - with few bristles & no parapodia, terrestrial or freshwater deposit-feeders, aerate soils
  • Leeches - no bristles, no parapodia, most live in fresh water, some are terrestrial, produce anti-coagulant (hirudin)
• Phylum Platyhelminthes are dorsoventrally flattened acoelomates with a gastrovascular cavity or no digestive tract
• Phylum Syndermata are pseudocoelomates, with rotifers having an alimentary canal and jaws, and acanthocephalans being parasites of vertebrates
• Lophophorates are coelomates with lophophores (feeding structures bearing ciliated tentacles)
• Mollusca are coelomates with three main body parts (muscular foot, visceral mass, mantle), reduced coelom, and most have a hard shell made of calcium carbonate

  
• Annelida are coelomates with a segmented body wall and internal organs (except digestive tract, which is unsegmented)
• Superphylum Ecdysozoans= the most species-rich animal group

  • including crayfish, lobsters, crabs, barnacles, spiders, ticks, and insects,
  • covered by a tough cuticle that is molted through ecdysis
• The two largest phyla of Ecdysozoans are Nematoda (roundworms) and Arthropoda
• Ecdysozoans: Nematoda (roundworms)


  • No segmentation
  • have a pseudocoelom,
  • body covered by tough cuticle (flexible)
  • some are plant and animal parasites
• Ecdysozoans: Tardigrada ("water bears")

  • Segmented with chitinous cuticle that sheds,
  • 4 pair stubby, unjointed legs,
  • very small (<0.5mm),
  • live in water films on mosses and soils
  • can survive extreme conditions in dehydrated dormant state
• Major groups of Arthropoda

  • Chelicerata
  • Myriapoda
  • Crustacean
  • Hexapoda
• Ecdysozoans: Arthropod exoskeleton

  • cuticle Made of polysaccharide chitin & proteins,
  • thick & hard for support, protection & attachment of muscles, thin at joints,
  • waterproofed with waxes in land species,
  • enabled first arthropods to colonize land,
  • but limits growth & final body size, must be shed to grow (molting= ecdysis)
• Arthropod organ systems


  • Circulatory system: open circulatory system. Have hemolymph fluid thats pumped in vessels and bathes tissues
  • Respiratory system: such as tracheal system
  • Digestive system
  • Nervous system
  • Excretory system: such as malpighian tubules
  • Reproduction system
• Arthropod gas exchange


  • Aquatic species: hemolymph pumped through feathery gills
  • Terrestrial arthropods: book lungs and tracheal system that takes air directly to cells for gas exchange.
  • Spiders hemolymph flows thru book lungs in contact w/ air
  • Circulatory system NOT involved in insects!