Tetrapods: Out on a limb

What are the defining characteristics of mammals? Mammals are a diverse class of vertebrate animals that share several key traits. These include the presence of mammary glands in females, which produce milk to feed their young; a body covering of hair or fur at some stage of life for insulation; a specialised jaw structure with three middle ear bones for enhanced hearing; being warm-blooded (endothermic), allowing them to maintain a stable internal body temperature; and typically giving birth to live young, with a few exceptions like the egg-laying monotremes . They also possess specialised teeth adapted for various diets and a four-chambered heart for efficient blood circulation. What are the main groups or divisions within the class Mammalia? The class Mammalia is broadly divided into three main groups based on their reproductive strategies. These are: Monotremes: These are unique egg-laying mammals, such as the platypus and echidna . Marsupials : This group includes pouched mammals...

What are the defining characteristics of reptiles? Reptiles are a class of vertebrates (animals with backbones) that are typically cold-blooded ( ectothermic ), meaning they rely on external heat sources to regulate their body temperature. They are covered in dry, scaly skin made of keratin, which provides protection and helps prevent water loss. Most reptiles reproduce by laying amniotic eggs with protective membranes, allowing for development on land. All reptiles breathe using lungs, and while some, like snakes, are limbless, the class is generally characterised by having four limbs or being descended from four-limbed ancestors.  What are the main groups or orders of living reptiles? There are four main living orders of reptiles.  Squamata is the largest order, encompassing lizards and snakes, known for their diverse forms and behaviours. Testudines includes turtles and tortoises, distinguished by their protective bony shells. Crocodylia consists of crocodiles, alligator...

What are the defining characteristics of amphibians? Amphibians are cold-blooded vertebrates that typically start their lives in water and transition to living on land. Key characteristics include undergoing metamorphosis from an aquatic larval stage (like tadpoles ) to a terrestrial or semi-aquatic adult form, possessing moist, permeable skin crucial for respiration and absorbing water and oxygen, and being ectothermic (cold-blooded), relying on external sources to regulate their body temperature. What are the main groups of amphibians? The amphibian class is divided into three primary groups: Frogs and Toads (Anura), which are the largest and most recognisable group, characterised by powerful jumping legs and a tailless adult form; Salamanders and Newts (Caudata/Urodela), which are elongated and resemble lizards but lack scales and possess tails in adulthood; and Caecilians (Gymnophiona), the least known group, which are legless and worm-like, primarily found in tropical regions....

What are the defining characteristics of birds? Birds are vertebrates , meaning they have a backbone. They are uniquely identified by having feathers , wings, and beaks without teeth. While most birds use their wings for flight, some have adapted to life on land or water and do not fly. They all reproduce by laying eggs. Feathers serve multiple purposes, including insulation, flight, and display. How many bird species exist globally and what is the range of their habitats? There are over 10,000 known species of birds worldwide. These species exhibit an incredible diversity in size, shape, colour, and behaviour. They are found across every continent and inhabit a wide variety of environments, including icy polar regions, arid deserts , dense forests, grasslands, hedgerows, heathlands, rivers, wetlands, coastal areas, and even urban spaces and gardens. Their ability to fly allows them to inhabit such diverse locations.  What significant roles do birds play in ecosystems? Birds play ...