Week 8A

• Protist

  Organism similar to but not identical to current daquino flagella
• Earliest animals

  • Sponges
• Cells of sponges

  • Very similar to the quantifying deletes
  • Coenocytic
• Animal


  • Eukaryotic
  • Multicellular
  • No cell walls
  • Heterotrophic
  • Motile at some point during their life cycle
• Unicellular eukaryotes that are animal-like are lumped in with the protists
• Modes of animal reproduction

  • Asexual
  • Sexual
• Animals

  • Have an extensive extracellular matrix around the cells that provides structural support
  • Have unique cell junctions that help hold cells in place and facilitate communication, including gap junctions, anchoring and tight junctions
• Heterotrophs


  Cannot produce their own photosynthate, so they have to eat other organisms or the products that those other organisms make
• Animal feeding

  • Feeding on plant material
  • Feeding on animal material
• Animal feeding

  1. Suspension feeding (filtering particles from surrounding water)

  2. Bulk feeding (eating large pieces of food)

  3. Fluid feeding (sucking sap or animal body fluids)
• Animals cannot produce their own high carbon food like photosynthate because they are heterotrophs
• Animals

  • Have muscles and nerve cells organized into specific tissues, including muscle tissue and nervous tissue
  • Muscle tissue is unique to animals
• Movement is a big characteristic of animals
• Plants or fungi or any of the protists are capable of moving and have some sort of locomotion in order to find food items or to escape from predators or to find mates
• The movement of most animals is usually coordinated using a combination of sensory structures and the nervous system
• Some species that appear to be sessile, such as barnacles, can move their appendages or are capable of moving at some stage in their development, such as in the larval stage when they can swim
• Some species reproduce asexually, such as through parthenogenesis where a female can produce offspring without fertilization
• Most species reproduce sexually, with a dimorphism between the male contribution (small sperm) and the female contribution (large eggs)
• In terrestrial animals, there is usually internal fertilization, while in aquatic animals, external fertilization is common due to the aquatic environment
• Metamorphosis


  The animal changes over time as it matures
• Metamorphosis examples

  • Frog (egg to tadpole to adult frog)
  • Insects (egg to larva to pupa to adult)
• Some species have immature stages that look completely different from the adult forms
• Common characteristics of animals

  • Multicellular
  • Heterotrophic (have to get food by eating other organisms or their products)
  • Lack cell walls
  • Have nervous tissue to respond to environmental stimuli
  • Have a muscular system for movement
  • Reproduce sexually with small sperm and larger eggs
  • Have unique extracellular matrix and cell junctions
  • Possess Hox genes that determine body patterning
  • Have similar small ribosomal subunit RNA molecules
• If a single-celled eukaryotic organism, it would be called a protist
• Metamorphosis


  The animal changes over time as it matures
• Metamorphosis examples

  • Frog (egg to tadpole to adult frog)
  • Insects (egg to larva to pupa to adult)
• Some species have immature stages that look completely different from the adult forms
• Common characteristics of animals

  • Multicellular
  • Heterotrophic (must get food by eating other organisms or their products)
  • Lack cell walls
  • Have nervous tissue to respond to environmental stimuli
  • Have muscular system for movement
  • Reproduce sexually with small sperm and larger eggs
  • Have unique extracellular matrix and cell junctions
  • Possess Hox genes that determine body patterning
  • Have similar small ribosomal subunit RNA genes
• Animal cells lack cell walls, unlike plants, fungi, bacteria, archaea and most protists
• Most animals reproduce sexually with small sperm and larger eggs
• Animals have a unique extracellular matrix and cell junctions
• Most animals possess Hox genes that function in determining the patterning along the body axis
• Animals have very similar genes for the small ribosomal subunit RNA molecules
• Protists


  Unicellular eukaryotes that are animal-like, but not true animals
• Multicellular animals emerged

  End of the Proterozoic Eon
• First animals

  • They were invertebrates
  • They were marine
• Animal diversity really increased

  Cambrian, about 530 million years ago
• There were a lot of different body forms in the Cambrian
• The fossil beds from the Cambrian are just spectacular, like the Burgess Shale fossil beds
• Cambrian explosion


  Up until the Cambrian, there really hadn't been all that many new novelty forms, but suddenly it looks like all of these animal forms just seem to appear