Vertebrate Animals: Mammals, Birds, and Reptiles

Mammals

• Females have breasts that produce milk to feed their young.
• The body is covered with hair.
• Body temperature is constant.
• Young are born alive.
• Examples: Prototherians (e.g., the platypus), marsupials (e.g., kangaroos), and eutherians (e.g., insectivores, bats, primates, cetaceans, carnivores, Perissodactyla, and Artiodactyla).
• Temperature: Mammals maintain a constant body temperature, typically between 38 and 40 degrees Celsius, regardless of whether they live in hot or cold climates.
• Reproduction: Mammals reproduce viviparously with internal fertilization. They lay eggs without nutrient reserves, which are implanted and developed in the womb. The placenta provides nourishment and oxygen to the developing fetus and facilitates the excretion of waste substances, ensuring communication between mother and fetus.

Birds

• Characteristics: Feathers, beak, and wings.
• They are oviparous (lay eggs) and homeothermic (maintain a constant body temperature).
• Examples: Archaeornithes (ancient birds with characteristics of both reptiles and birds) and Neornithes (modern birds, including Odontognathae, Paleognathae, Neognathae, and Ciconiiformes).
• Temperature: Birds are warm-blooded.
• Reproduction: Birds are oviparous. The female incubates the eggs after internal fertilization. Birds have separate sexes. Females typically have only one ovary and a left oviduct.
• Feather Types:
  • Remiges (Flight Feathers): These are large and stiff feathers. The rachis (central shaft) has two parallel rows of barbs, each with two rows of barbules.
  • Tectrices (Covert Feathers): Similar to remiges but smaller and concave. They overlap each other like shingles on a roof.
  • Plumules (Down Feathers): These feathers have a very short rachis and calamus. The barbs, emerging from the tip, are flexible and have barbules.
  • Filoplumes: These are thick and hair-like. They have a long rachis with barbs and some barbules at the end.
• Feather Features: Feathers provide the aerodynamic body shape, form an insulating layer, increase the wing area, and give color to the bird. They are implanted in the epidermis, and their base is connected to a small muscle.
• Adaptations for Flight: Pneumatic bones (hollow bones filled with air), air sacs, remiges that increase the bearing surface of the wings, aerodynamic body shape, a stiff spine, tail feathers acting as a rudder, and specialized wing movements.

Reptiles

• Characteristics: Lung-breathing, scales, hatch from eggs, and body temperature varies with the environment (poikilothermic).
• Examples: Squamata (lizards and snakes), Chelonia (turtles), Crocodilia (crocodiles and alligators), and Rhynchocephalia.
• Temperature: Reptiles are cold-blooded animals. Their body temperature matches the temperature of their environment. They often hibernate during winter.
• Reproduction: Reptiles have sexual reproduction.
• Venomous vs. Non-venomous Snakes:
  • Venomous: Broad head covered with triangular scales, elliptical and vertical pupils, elongated scales with a longitudinal ridge, and a narrow tail that ends abruptly.
  • Non-venomous: Elongated head covered by plates with circular pupils, smooth and rounded scales, and a gradually tapering tail.