Zoology and Botany Lecture Notes

Mollusca

• Mostly bilateral, triploblastic, and coelomate.
• Protostome development (Mollusca + Annelida).
• Characterized by:
  • Soft body and often a hard shell.
  • Muscular foot.
  • Mantle.
  • Visceral mass.
  • Radula.
• Classes:
  • Polyplacophora.
  • Bivalvia.
  • Gastropoda.
  • Cephalopoda (have a closed vascular system).
• Possess a nervous system and mostly a digestive system (alimentary canal).
• Non-segmented.
• Some have a head region (except clams and mussels).

Annelida

• Bilateral, triploblastic, and coelomate.
• Protostome development (Mollusca + Annelida).
• Known as segmented worms ("little rings").
• Classes:
  • Polychaeta.
  • Oligochaeta.
  • Hirudinea.
• Possess a nervous and digestive system.

Nematoda

• Bilateral, triploblastic, and pseudocoelomate.
• Roundworms with a cuticle.
• Possess a nervous and digestive system (alimentary canal).
• Non-segmented.
• Have a head region.

Arthropoda

• Bilateral, triploblastic, and coelomate.
• Protostome development (Mollusca + Annelida).
• Characterized by:
  • Modified mouthparts.
  • Exoskeleton.
  • Jointed appendages.
• Classes:
  • Arachnida (open circulatory system).
  • Crustacea.
  • Myriapoda.
  • Hexapoda (closed vascular system).
• Possess a digestive system (alimentary canal).
• Main body cavity is a hemocoel.
• Segmented with tagmatization.

Body Systems Key

• V = Vascular system.
• D = Digestive system/tract.
• N = Nervous system.

Porifera

• Asymmetrical.
• Tissue layers: N/A (lacks true tissues).
• Acoelomate (no body cavity).
• Distinguishing features:
  • Gelatinous matrix called mesohyl.
  • Cell types: choanocytes (flagellated collar cells to trap food) and amoebocytes (totipotent, motile, digestion, transport).
  • Filter feeders using water currents.
• Water enters the spongocoel via pores and exits via a large opening called the osculum.
• No classes listed.
• No embryonic development information provided.
• N/A for body systems.
• N/A for body parts/segmentation.

Cnidaria

• Radial symmetry.
• Diploblastic (two tissue layers: endoderm and ectoderm).
• Acoelomate (no body cavity).
• Distinguishing features:
  • Open body plan.
  • Have stinging cells (cnidocytes) that are defensive or predatory.
• Classes:
  • Hydrozoa.
  • Scyphozoa.
  • Cubozoa.
  • Anthozoa (corals and anemones).
• N/A for embryonic development.
• Simple nervous system; no vascular system; gastrovascular cavity for digestion.
• Body form as polyp or medusa; no head region; non-segmented.

Echinodermata

• Larvae are bilateral, adults appear radial.
• Triploblastic and coelomate.
• Deuterostome development (Mouth + most Anus).
• Characterized by "spiny skin".
• Calcareous endoskeleton.
• Pentamerous (5-part) radial symmetry.
• Tube feet.
• Classes:
  • Sea lilies.
  • Starfish.
  • Brittle stars.
  • Sea urchins.
  • Sea cucumbers.
• Water vascular system.
• Simple nerve ring.
• Digestive system or cavity.
• Non-segmented.
• Typically lack a head region.

Chordata

• Bilateral symmetry.
• Triploblastic and coelomate.
• Deuterostome development (Mouth + Anus).
• Classes:
  • Fish.
  • Amphibians.
  • Reptiles.
  • Birds.
  • Mammals.
• Nervous and vascular systems present.
• True digestive system (alimentary canal).
• Many have a head region.
• Segmented at some stage.
• Key characteristics present at some point in development: notochord, dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.

Platyhelminthes

• Bilateral symmetry.
• Triploblastic and acoelomate.
• Protostome development (Mouth only).
• Dorsoventrally flattened.
• Classes:
  • Turbellaria (e.g., Planaria).
  • Trematoda.
  • Cestoda (tapeworms).
• Nervous system present.
• No vascular system.
• Gastrovascular cavity for digestion; Cestoda have no gut.
• Flame bulb excretory system.
• Non-segmented.
• Head region (cephalization).
• Surface gas exchange.
• Most hermaphroditic (function as both sexes).

Rotifera (Syndermata)

• Bilateral symmetry.
• Triploblastic and pseudocoelomate.
• Protostome development (Mouth + Anus).
• "Wheel bearers" - use a water vortex for feeding.
• Nervous system present.
• Digestive system present.
• Non-segmented but can appear so.
• Head region.

Monocot vs. Eudicot

• Leaf attachment:
  • Monocot: Directly attached to the stem via a sheath.
  • Eudicot: Attached to the stem via a petiole.
• Stem structure:
  • Monocot: Vascular bundles are distributed as a complex network throughout the inner part of the stem.
  • Eudicot: Vascular bundles are arranged in one ring surrounding the pith.
• Leaf structure:
  • Monocot:
    • Single or double layered bundle sheaths with chloroplasts.
    • Only one type of mesophyll.
    • Narrow and elongated (isobilateral).
    • Stomata arranged in parallel rows equally on upper and lower epidermis.
  • Eudicot:
    • Single layered bundle sheaths with colorless cells.
    • Palisade mesophyll (top leaf surface) and spongy mesophyll.
    • Rounded with a central midvein (dorsiventral).
    • Stomata arranged randomly.
    • Thicker upper epidermis with fewer stomata.
• Root structure:
  • Monocot: Groups of phloem and xylem cells are arranged alternatively just inside the endodermis and pericycle and outside the pith that occupies the center of many monocot roots.
  • Eudicot: Xylem arranged in a 'star' pattern in the center of the root with the phloem between the arms of the star.
• Stomatal guard cells:
  • Monocot: Dumb-bell shaped.
  • Eudicot: Kidney shaped.