Animal and Eukaryotic Diversity Study Notes

Overview of Eukaryotic Groups

• Major Eukaryotic Groups:
  • Brown algae
  • Diatoms
  • Water molds
  • Apicomplexans
  • Dinoflagellates
  • Ciliates
  • Chlorarachniophytes
  • Foraminiferans
  • Land plants
  • Green algae
  • Red algae
  • Glaucophyte algae
  • Kinetoplastids
  • Euglenids
  • Diplomonads
  • Parabasalids
  • Animals
  • Choanoflagellates
  • Fungi
  • Plasmodial slime molds
  • Cellular slime molds
  • Lobose amoebae
• Classification of Eukaryotes:
  • All eukaryotes are protists except for fungi, animals, and land plants.
  • Major Supergroups:
  • Unikonta
    • Amoebozoa
    • Opisthokonta
  • Bikonita
    • Excavata
    • Plantae
    • Rhizaria
    • Alveolata
    • Stramenopila
• Multicellularity:
  • Evolved independently at least seven times.

Animal Diversity

• Overview of Animal Taxonomy:
  • Monophyletic Group: All animals share a common ancestor.
  • Classification of major animal phyla based on developmental patterns, symmetry, and body plans.
  • Basic Structure:
  • Multicellularity
  • Various levels of tissue organization

Major Groups of Animals

• Non-Bilaterians:

  • Placozoa: 1 species
  • Ctenophora: 190 species
  • Acoela: 350 species
  • Porifera (Sponges): 8500 species
  • Cnidaria: 11,500 species

• Bilaterians: Divided into two major groups:

  • Protostomes:
  • Lophotrochozoa: e.g., Mollusca, Annelida (Segmented worms)
  • Ecdysozoa: e.g., Arthropoda, Nematoda
  • Deuterostomes:
  • Echinodermata (like sea stars)
  • Chordata (including vertebrates)

Origin of Multicellularity

• All animals are believed to have arisen from a single multicellular ancestor.
• Sponges as the Most Ancient Lineage:
  • Fossil evidence supports that sponges are among the earliest animals.

Morphological Evidence for Sponges

• Both sponges and choanoflagellates share several characteristics:
  • Both are benthic and sessile organisms.
  • Feeding occurs via choanocytes in sponges and similar cells in choanoflagellates.

Identifying Animal Characteristics

• Characteristics Typical to Animals:
  • Multicellularity
  • Extracellular matrix
  • Introduction of tissues and organs from embryonic germ layers.
  • Distinct reproductive strategies (e.g., eggs and sperm).

Cnidarians

• Group Overview:

  • Radially symmetric, diploblastic body structure.
  • Cells called cnidocytes, which have stinging structures called nematocysts.
  • Includes classes like Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa.

• Hydrozoa:

  • Marine group; includes species with both polyp and medusa stages.

• Scyphozoa:

  • Marine jellies; exhibit reduced polyp stage.

• Cubozoa:

  • Box-shaped medusae; many are poisonous.

• Anthozoa:

  • Assumes no medusa stage; includes corals and sea anemones.
  • Reef-building corals often have symbiotic algae.

Key Evidence for Animal Classification

• Sponges previously considered colonies of protists due to their ability to reaggregate after dissociation.
• Essential evidence for classification includes the presence of flagellated feeding cells and their unique feeding mechanisms.

Summary of Key Concepts

• Synapomorphies for Animals:
  • Multicellularity, extracellular matrix, nerve cells
  • Comparison of feeding structures in sponges and choanoflagellates provides insight into the evolutionary history of animals.