Animal Evolution II Notes

Animal Phylogeny

  • Module 13 Overview: Covers animal phylogeny, invertebrates, chordates, vertebrates, tetrapods, and mammals.

  • Based on Chapters 32-34 of Campbell Biology.

Learning Objectives

  • Define key characteristics of invertebrates, including body plans, symmetry, and unique cell types.

  • Classify invertebrates into clades based on anatomical traits and molecular data, emphasizing phylogenetic relationships.

  • Understand the evolution of bilateral symmetry on a phylogeny and its significance in animal evolution.

  • Recognize the importance of the notochord in vertebrate evolution, detailing its structure and function.

  • Associate key vertebrate innovations with clade names, such as jaws in gnathostomes and amniotic eggs in amniotes.

  • Describe the evolution of gill arches in vertebrates and their role in the development of jaws and other structures.

  • Explain

Animal Phylogeny

  • Module 13 Overview:

    • Covers animal phylogeny, focusing on the evolutionary relationships and characteristics of animals.

    • Includes detailed studies of:

    • Invertebrates: Animals without a backbone, showcasing diverse body plans and adaptations.

    • Chordates: Animals with a notochord at some point in their development.

    • Vertebrates: Chordates with a backbone.

    • Tetrapods: Four-limbed vertebrates.

    • Mammals: A class of vertebrates characterized by mammary glands, hair, and warm-bloodedness.

    • Based on Chapters 32-34 of Campbell Biology:

    • Provides a comprehensive understanding of animal diversity and evolution.

Learning Objectives

  • Define key characteristics of invertebrates:

    • Body plans:

    • Discuss the various body plans seen in invertebrates, such as radial and bilateral symmetry.

    • Symmetry:

    • Explain radial, bilateral, and asymmetry with examples.

    • Unique cell types:

    • Identify specialized cells like cnidocytes in cnidarians.

  • Classify invertebrates into clades:

    • Based on anatomical traits and molecular data.

    • Emphasize phylogenetic relationships to understand evolutionary connections.

  • Understand the evolution of bilateral symmetry:

    • Its significance in animal evolution, leading to cephalization and directional movement.

  • Recognize the importance of the notochord in vertebrate evolution:

    • Detail its structure and function as a flexible rod providing support.

  • Associate key vertebrate innovations with clade names:

    • Jaws in gnathostomes: Discuss the evolution of jaws from skeletal supports of the pharyngeal slits.

    • Amniotic eggs in amniotes: Describe the structure and advantages of the amniotic egg in terrestrial environments.

  • Describe the evolution of gill arches in vertebrates:

    • Their role in the development of jaws and other structures.

Invertebrates

  1. Porifera (Sponges)

    • Lack true tissues and organs.

    • Have specialized cells called choanocytes for filter feeding.

    • Simplest animals; basal lineage.

  2. Cnidaria (Jellyfish, Corals)

    • Radial symmetry.

    • Have cnidocytes (stinging cells).

    • Two major body plans: polyp and medusa.

  3. Lophotrochozoa

    • Characterized by the presence of a lophophore (feeding structure) or a trochophore larva.

    • Includes:

      • Platyhelminthes (Flatworms): Acoelomates with no specialized respiratory or circulatory systems.

      • Mollusca (Snails, Clams, Squids): Soft-bodied with a mantle that may secrete a shell.

      • Annelida (Segmented Worms): Coelomates with segmented body plan.

  4. Ecdysozoa

    • Undergo ecdysis (molting).

    • Includes:

      • Nematoda (Roundworms): Pseudocoelomates with a tough cuticle.

      • Arthropoda (Insects, Crustaceans, Spiders): Segmented body, exoskeleton, and jointed appendages.

Bilaterian Development

  • Protostome vs. Deuterostome Development

    • Protostomes: The blastopore becomes the mouth.

    • Deuterostomes: The blastopore becomes the anus.

Chordates

  • Four key characteristics present in all chordates at some point during development:

    1. Notochord: Flexible rod providing support.

    2. Dorsal, hollow nerve cord: Develops into the brain and spinal cord.

    3. Pharyngeal slits or clefts: Function in filter feeding, as gills, or develop into other structures.

    4. Muscular, post-anal tail: Provides propulsion in aquatic species.

  • Invertebrate Chordates

    • Cephalochordata (Lancelets): Basal chordates that exhibit all four key characteristics as adults.

    • Urochordata (Tunicates): Larvae have all four key characteristics, but adults may only retain pharyngeal slits.

Vertebrates

  • Vertebrate Innovations

    • Vertebral column: Replaces the notochord as the main body support in adults.

    • Cranium: Protects the brain.

  • Gnathostomes (Jawed Vertebrates)

    • Jaws likely evolved from skeletal supports of the pharyngeal slits.

    • Other innovations include:

    • Enhanced sensory systems.

    • Paired appendages.

  • Tetrapods

    • Adaptations to life on land:

    • Four limbs for locomotion.

    • Lungs for respiration.

    • Adaptations to prevent desiccation.

  • Amniotes

    • Amniotic egg: Contains membranes that protect the embryo and prevent desiccation.

    • Includes reptiles (including birds) and mammals.

Mammals

  • Key characteristics:

    • Mammary glands (produce milk).

    • Hair or fur.

    • Three middle ear bones.

  • Major groups:

    • Monotremes: Egg-laying mammals (e.g., platypus).

    • Marsupials: Mammals with a pouch (e.g., kangaroo).

    • Eutherians: Placental mammals (e.g., humans).