Lecture 22: The Amniotes and Evolutionary Biology

This set of flashcards covers key concepts, terms, and definitions from the lecture on amniotes, evolutionary biology, and the adaptations that have enabled these organisms to thrive on land.

Amniotes

A clade of vertebrates characterized by having an amniotic egg, which allows them to reproduce on land without the need for a water environment.

Amniotic egg

A type of egg that contains specialized membranes, including a protective shell and fluid-filled sac, providing a safe environment for the developing embryo.

Dry skin

A trait of amniotes that helps prevent water loss, as opposed to the moist skin typical of amphibians.

Ectotherms

Organisms that rely on an external source of heat to regulate their body temperature; seen in non-avian reptiles.

Endotherms

Organisms that can generate their own heat internally to maintain body temperature; characteristic of birds and mammals.

Synapsids

An early group of amniotes that eventually led to mammals; characterized by having a single temporal fenestra in the skull.

Diapsids

A group of reptiles characterized by having two temporal fenestrae; includes all reptiles and birds.

Thoracic breathing

A more efficient breathing method found in amniotes, involving ribcage expansion to draw air into the lungs.

Natural selection

The process through which species adapt and evolve over time, driven by environmental pressures and survival of the fittest.

Theropods

A clade of dinosaurs that includes modern birds, characterized by their bipedal posture and certain skeletal adaptations for flight.

Palaeognaths

A subclass of birds that includes flightless species (often called ratites) such as ostriches, emus, rheas, cassowaries, kiwis, and tinamous, characterized by more primitive anatomical features.

Neognaths

A diverse group of birds that evolved from flying ancestors and have a wider range of adaptations, including most modern bird species like waterfowl, owls, parrots, and songbirds.

Parental care

The investment of time and resources by parents to ensure the survival of their offspring, seen in many reptiles and birds.

Scales

Keratinized structures covering the skin of reptiles that help reduce water loss and protect against environmental damage.

Migration

Seasonal movement of birds from one region to another, often for breeding or to exploit seasonal resources.

Adaptation

A trait that has evolved through natural selection, enhancing the survival and reproduction of organisms in their environment.

Internal fertilization

A reproductive strategy where fertilization of the egg by sperm occurs inside the body of the female, characteristic of amniotes and enabling reproduction on land.

Glottal breathing

A less efficient form of breathing often seen in amphibians, involving the opening and closing of the glottis to gulp air, contrasting with the more efficient thoracic breathing of amniotes.

Amniote jaw

A more robust and efficient jaw structure found in amniotes, adapted for a wider range of feeding behaviors and capable of generating greater biting forces compared to their amphibian ancestors.

Therapsids

A group of synapsids that includes the ancestors of mammals, characterized by more mammal-like skeletal features and adaptations.

Archosaurs

A major group of diapsids that includes crocodiles, alligators, pterosaurs, dinosaurs (including birds), and their extinct relatives, known as 'ruling reptiles'.

Tuataras

Reptiles endemic to New Zealand, representing the only surviving lineage of Sphenodontia, an order distinct from lizards and snakes.

Squamates

The largest order of reptiles, including lizards and snakes, characterized by their scaly skin and movable quadrate bones in the skull allowing for wide gape.

Testudines

The order of reptiles that includes turtles and tortoises, distinguished by their characteristic bony shell.

Crocodilians

A group of large, semi-aquatic reptiles, including crocodiles, alligators, caimans, and gharials, known for their powerful jaws and ancient lineage within the archosaurs.

Feathers

Unique keratinous epidermal outgrowths that cover the bodies of birds, providing insulation, flight surfaces, and display.

Keel (Bird Skeleton)

A prominent ridge on the sternum (breastbone) of most birds, serving as an attachment point for powerful flight muscles.

Bird lungs

Highly efficient respiratory systems in birds, characterized by a unidirectional airflow through parabronchi and air sacs, allowing for constant oxygen uptake.

Beak Morphology

The study of the structure and shape of a bird's beak (bill), which is highly adapted to its diet and feeding behavior.

Foot Morphology (Birds)

The study of the structure and shape of a bird's feet, which are adapted for various functions such as perching, grasping, swimming, or running.

Passeriformes

The largest order of birds, commonly known as perching birds or songbirds, characterized by their specialized foot structure for grasping branches.

Pelycosaurs

An early group of synapsids from the late Paleozoic era, some of which, like Dimetrodon, were sail-backed, representing an important step in the evolution towards mammals.

Velociraptors

A genus of dromaeosaurid theropod dinosaur, known for its bipedal stance, carnivorous diet, and sharp claws, closely related to modern birds.