Birds

Chapter 19: Phylum Chordates (Chordata)

Sub-phylum Vertebrates (Craniata)

  • Clade Gnathostomata

  • Clade Osteichthyes

  • Clade Tetrapods

  • Class of Reptiles (Reptilia)

  • Clade of Birds (Aves)

Life Classification

  • Domain: Life

  • Kingdom: Animalia

  • Phylum: Chordata

    • Subphylum: Vertebrata

    • Class: Reptiles

    • Orders:

      • Squamates

      • Testudines

      • Crocodilians

    • Clades: Birds

  • Family, Genus, Species classification hierarchy

Chordata Characteristics

Core Concepts

  • Chordata: Animals with notochord at some stage of life

  • Vertebrata: Chordates with vertebrae and a cranium

  • Gnathostomata: Vertebrates with jaws

  • Osteichthyes: Bony fishes + tetrapods

  • Tetrapoda: Four-limbed vertebrates

  • Amniota: Tetrapods with embryos having extraembryonic membranes

Major Clades Under Chordata

Key Groups

  • Protochordata

  • Agnatha

  • Reptilia

  • Cephalochordata (lancelets)

  • Cyclostomata (hagfishes, lampreys)

  • Actinopterygii (ray-finned fishes)

  • Crocodilia

  • Amphibia (e.g., frogs and salamanders)

  • Chondrichthyes (sharks and rays)

  • Urochordata (tunicates)

Amniota Classification

Subgroups

  • Synapsida (Mammals)

  • Diapsida (Reptiles)

    • Lepidosauria (including lizards and snakes)

    • Testudines (turtles)

    • Other notable adaptations of reptiles:

      • Loss of diapsid openings in skull

      • Hemipenes in males

      • Modified skeletons

Clade Aves (Birds)

  • Over 9,000 species, more than all other tetrapods combined

  • Loss of temporal fenestration, loss of teeth leading to the presence of beak, and parental care

  • Key features of birds:

    • Endothermy (warm-blooded)

    • Flight adaptations

Bird Groups

  1. Paleognathae: Flightless birds (e.g., Kiwi, Ostrich, Emu)

    • Include giant moa and elephant bird

  2. Neognathae: Flying birds (e.g., Kakapo)

Adaptations for Flight

  • Feathers:

    • Types: Flight feathers and down feathers

    • Exaptation: Modified reptilian scales developed from epidermal thickening

  • Skeletal Modifications:

    • Lightweight and hollow bones

    • Keeled sternum for muscle attachment

  • Muscular System:

    • Large flight muscles attached to the keel of the sternum

    • Adaptations include a rope-and-pulley arrangement for flying

Other Systems in Birds

4) Digestive System

  • Rapid digestion of energy-rich diet

    • Crop for storage

    • Gizzard for grinding food

5) Circulatory System

  • 4-chambered heart

    • Fast heartbeats and high blood pressure

6) Respiratory System

  • Modified lungs with air sacs allowing for unidirectional airflow

  • Highly efficient, can sustain high metabolism

7) Nervous and Sensory System

  • Strong coordination and balance from developed cerebellum

  • Good hearing with large optic lobes for enhanced vision

8) Reproductive System

  • Reproductive organs typically on the left side in females

  • Various mating systems and courtship rituals

Ecological Niche of Birds

  • Clade Aves has radiated to exploit numerous terrestrial niches, adapting to various habitats including polar regions.