Animal

• However, some have also advocated total re-organization of the kingdoms of living things
• Molecular analysis (using ribosomal RNA) indicates that the kingdoms are not monophyletic
• Eukaryotes have been classified into six major supergroups

  • Amoebozoa (protists, amoebae and slime moulds)
  • Archaeplastida (plants)
  • Chromalveolata (red alga etc.)
  • Excavata(flagellated orgainisms)
  • Opisthokonta (fungi and animals)
  • Rhizaria (shelled amoebas)
• Classification of organisms


  Can be based on advancement in body structure organisation, habitat, lifestyle, biochemical and molecular characteristics
• In some widely used taxonomic systems, living things are classified under five kingdoms

  • Monera (prokaryotae), (or Achaebacteria & Eubacteria(US)
  • Protista
  • Fungi
  • Plantae
  • Animalia
• Monera


  Prokaryotes, comprising the bacteria and cyanobacteria, characterized by the absence of a distinct, membrane-bound nucleus or membrane-bound organelles, and by DNA that is not organized into chromosomes
• Eukarya (eukaryotes)


  Organisms composed of one or more cells containing visible evidence of nuclei and organelles

  
• The kingdoms of the Eukarya that are important for this course are the Protista and Animalia
• Protists


  Have numerous compartments ie membrane enclosed organelles which help to keep items separate or together
• Invertebrates


  • No vertebrae, eg worms, insects, snails, amoeba; Very diverse and widely distributed, 97% of animal species
• Vertebrates


  • Have vertebral column, eg: birds, reptiles, fishes, Complexity, advanced development, specialization
• Protista (or Protoctista)


  Defined by exclusion: its members are neither animals, plants, fungi, nor prokaryotes. They comprise the eukaryotic microorganisms and their immediate descendants
• In some widely used taxonomic systems, Protista is a kingdom comprising

  • Unicellular, coenocytic (having a multinucleate cell), colonial (all the cells are similar with similar, generalized functions) and multicellular ("body" of the organism consists of a variety of types of cells, each type with its own specialized function) organisms such as protozoans, slime molds, brown algae and green algae
• All protists are aerobic and have mitochondria to carry out cellular respiration
• Protoctista


  A group of unicellular protists
• Some protists are closely related to members of the kingdom Animalia, some motile others stationary, some photosynthetic others heterotrophic
• Most protists are unicellular while some are not only multicellular but also huge (but without specialized tissues)
• Protists can be


  • Animal-like
  • Plant-like
  • Fungi-like
• Animal-like and fungi-like Protists are heterotrophs, while Plant-like Protist are autotrophs
• For this course we shall restrict ourselves to protists that are animal-like
• Protozoa are usually the protists that are animal-like
• The plant-like protists are algae
• Animal-like Protists: The Protozoans("first animals")


  • Single-celled (unicellular) organisms, The single–celled organization does not imply that they are simple organisms, Some colonies can be so complex that some level of specialization is observed among the members
• Cell of the Animallike protist

  Comprised of organelles surrounded by cytoplasm, Outer and inner parts of the cytoplasm are called ectoplasm (rel. Clear and firm) and endoplasm (more fluid and granular) respectively, Cytoplasm is surrounded by plasma membrane, Lack a cell wall
• Animal-like protists


  • Microscopic, range in size from 0.01-0.5mm in diameter, Most are naked, but some have a simple endoskeleton or exoskeleton, All forms of body symmetries are present, No organs or tissues are present but possess highly specialized cell organelles
• Maintenance of Homeostasis: Size

  Small cells allow enough surface area to support exchange of materials necessary for survival
• Maintenance of Homeostasis: Vesicles

  Many relatively large unicellular protists minimize the problem of enough membrane surface area by having membrane-enclosed vesicles of various types to increase their effective surface area
• Maintenance of Homeostasis: Solute concentration

  Most marine protists have solute concentration similar to that of their environments (isotonic), Many freshwater protists, being hypertonic (have a higher concentration of solutes than their freshwater environment and constantly take in water by osmosis) to their environment, have to address the problem of excretion of excess water
• Maintenance of Homeostasis: Contractile vacuoles

  Many freshwater protists have contractile vacuoles into which excess water collects and is then push out of the body
• Maintenance of Homeostasis: Food vacuoles


  Many protists have food vacuoles into which food is engulfed by endocytosis and digested
• Endocytosis


  A process of cellular ingestion by which the plasma membrane folds inward to bring substances into the cell to form a vacuole, Types include phagocytosis (particulate substances), pinocytosis (liquid substances), and receptor-mediated endocytosis (cell surface receptors)
• Small vesicles containing digested food pinch away from the food vacuole, move around in the cytoplasm to distribute digested food and provide large surface area for absorption of nutrients
• Protozoans


  • Ecologically diverse and widely dispersed, Can be fantastically numerous, No germ layers are present (no embryogenesis), Have at least one motile stage in their life cycle, Movement is either by amoeboid motion, ciliary action, flagellar locomotion, or their combinations

  
• Amoeboid Motion


  The cells form pseudopods (pseudopodia; false feet) that are extensions of its constantly changing body mass, The pseudopodium is extended and the body flows into it
• Cilia and Flagella


  No real morphological distinction between the two structures although cilia are usually shorter and more abundant and flagella fewer and longer, Each flagellum or cilium is composed of 9 pairs of longitudinal microtubules arranged in a circle around a central pair, The collection of tubules is referred to as the axoneme and it is covered with a membrane continuous with the rest of the organism's cell membrane, Axoneme anchors where it inserts into the main body of the cell with a basal body
• Movement by Ciliary Action


  Cilia are tiny, hairlike organelles that beat in a coordinated fashion to move the cell forward or backward
• Movement by Flagella


  Flagellum moves like a whip, Some flagella push the cell forward, others pull the cell forward
• Symbiosis


  Persistent biological interactions in which one organism lives in or on another of different species; for mutual benefit of the partners (mutualism), where one organism derives benefit with little effect on the other (commensalism), and where one organism derives benefit at the expense of the other (parasitism)
• Some scientists contested that symbiosis should refer to only persistent mutualistic relationships
• Types of nutrition present in animallike protists

  • Autotrophic
  • Heterotrophic