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Mammals

Phylum Chordates

  • Sub-phylum Vertebrates (Craniata)

    • Clade Gnathostomata: Vertebrates with jaws

    • Clade Osteichthyes: Bony fishes and tetrapods

    • Clade Tetrapods: Four-limbed vertebrates

    • Class Mammals (Mammalia)

Chapter Overview

  • Overview of various vertebrate classes and traits

  • Classification details of Chordates

Page 2: Chordate Classification

  • Chordata: Animals having a notochord at some stage

    • Vertebrata: Chordates with vertebrae and cranium

    • Gnathostomata: Vertebrates possessing jaws

    • Osteichthyes: Includes bony fishes and tetrapods

    • Tetrapoda: Four-limbed vertebrates

      • Amniota: Tetrapods with extraembryonic membranes during development

  • Sub-groups within Chordata:

    • Protochordata: Early chordates without a backbone

    • Agnatha: Jawless vertebrates (hagfishes, lampreys)

    • Reptilia: Class including reptiles

    • Cephalochordata: Lancelets

    • Cyclostomata: Jawless fishes

    • Actinopterygii: Ray-finned fishes

    • Crocodilia: Crocodiles and allies (like lizards, snakes)

    • Chondrichthyes: Sharks and rays

    • Urochordata: Tunicates

    • Mammalia: Includes all mammals

Page 3: Modern Amniotes

  • Amniota: Characterized by extraembryonic membranes (amnion, chorion, and allantois)

    • Synapsida: Includes mammals; single temporal opening in skull

    • Diapsida: Includes reptiles and birds; two temporal openings

    • Lepidosauria: Group that includes lizards and snakes

    • Testudines: Turtles with a carapace and plastron

    • Archosauria: Includes crocodilians and birds

  • Morphological characteristics:

    • Males possess hemipenes

    • Beta-keratin found in skin

    • Diaphragm present aiding respiration

    • Lungs ventilated via negative pressure

Page 4: Classification of Mammals

  • Kingdom Animalia

    • Phylum Chordata

      • Subphylum Vertebrata

        • Class Mammalia

          • Subclass Prototheria (Monotremes)

          • Subclass Theria

            • Clades: Order Marsupials and Family Placentals

Page 5: Classes of Mammalia

  • Prototheria: Egg-laying mammals (Monotremes)

  • Theria: Includes marsupials and placentals

    • Evolution from diverse cynodont ancestors (Triassic to mid-Jurassic)

  • Key traits:

    • Hair and mammary glands

    • Unique jaw articulation (dentary-squamosal)

    • Three ear ossicles for hearing

Page 6: Mammal Characteristics

  • Class Mammalia: Comprises approximately 5,400 species

  • Distinctive features:

    • Skull with one temporal opening (synapsid)

    • Significant size variation across species

    • Endothermic (warm-blooded)

    • Chromosomal sex determination (presence of a penis)

    • Parental care behaviors observed

Page 7: Hair in Mammals

  • Synapomorphy of Mammalia: Presence of hair (alpha-keratin)

  • Functions of hair include:

    • Insulation

    • Camouflage and signaling

    • Tactile functions (as in whiskers)

    • Defense mechanisms (e.g., quills in porcupines)

Page 8: Skin Glands

  • Numerous dermal glands: Key for different functions

    • Sweat glands: Secreting watery fluid for thermoregulation

    • Sebaceous glands: Keep skin and hair pliable, secreting sebum

    • Scent glands: Used for communication

Page 10: Mammary Glands

  • Mammary glands: Essential for offspring feeding

    • Produce milk delivered via paired nipples

    • Unique feature in monotremes: Milk secreted onto the belly rather than through nipples

Pages 11-19: Adaptations for Metabolic Activity

  • Class Mammalia Adaptations to support high metabolic activity:

    1. Skeletal/Muscular Modifications: Specialized jaw musculature

    2. Digestive System: Heterodont teeth for different food types

    3. Respiratory System: Diaphragm for efficient breathing

    4. Circulatory System: Four-chambered heart for better oxygenation

    5. Excretory System: Efficient kidneys processing nitrogen waste as urea

Pages 20-23: Prototheria Characteristics

  • Monotremes: Only egg-laying mammals

    • Key species: Platypus and echidnas

    • Yolk sac utilized for feeding embryos, semipermeable shells for gas exchange

Pages 25-30: Theria Characteristics

  • Theria: All other mammals excluding monotremes

    • Key traits: Viviparous with presence of nipples and placenta

    • Short gestation period coupled with long lactation in marsupials

    • Species examples: Grey kangaroo, ring-tailed lemur

Pages 35-38: Placentals

  • Placentals: Major group with complex placentae

    • Diverse environments and dietary adaptations

    • Examples of placentals include pangolins, dolphins, and fruit bats

  • Adaptations for viviparity and fetal development in the uterus