Lecture 20 :Amniotes and nonavian reptiles

Amniotes

A monophyletic group within vertebrates that includes non-avian reptiles, birds, and mammals, characterized by the presence of an amniotic membrane around the embryo, internal fertilization, and laying eggs on land or retaining them within the mother.

Anamniotes

Vertebrates that lack an amniotic membrane, an informal group that includes fishes and amphibians.

Amniotic Egg

The egg characteristic of amniotes, with four extraembryonic membranes - amnion, chorion, allantois, and yolk sac, providing protection and nourishment to the developing embryo.

Amnion

Encloses embryo in fluid and cushions

Chorion

Surround entire egg, gas exchange, contributes to placenta

Allantois

Gas exchange and stores metabolic waste (uric acid) in birds and reptiles, placental development

Yolk sac

Also found in anamaniotes, stores nutrients

Waterproof Skin amphibians

Thin moist skin, permits gas exchanged, vulnerable to dehydration, some secrete mucus

waterproof skin amniotes

Changes in morphology, thicker tougher, more waterproof, few use skin for respiration

Rib Ventilation of the Lungs amniotes

Well developed lungs, use negative ventilation breathing, expand thoracic cavity to pull air into lungs

Riv ventilation of the lungs amphibians

Positive ventilation breathing push air from oral and pharyngeal cavity into lungs

Fish jaw

Designed for suction feeding, have teeth but don’t chew

Tetrapod jaw

Strong jaw for chewing and tongue, teeth for mastication (mammals)

High-pressure Cardiovascular System

An adaptation in amniotes for terrestrial life, with birds and mammals having a four-chambered heart to meet higher metabolic needs and counteract gravity.

Water-conserving Nitrogen Excretion ammonia

Aquatic organisms, toxic at low concentrations, diluted with high amounts of water

water conserving nitrogen excretion urea

Mammals and amphibians, less toxic so less dilution, concentrated in kidneys

water conserving nitrogen excretion uric acid

Birds and nonavian reptiles, least toxic, bladder gets diluted urine and water and salt is adsorbed in the bladder and voided as semi solid mass

Expanded Brain and Sensory Organs

Feature of amniotes with a relatively large brain, particularly well-developed in birds and mammals, allowing for better integration of sensory information and muscle control during locomotion.

Reptilia

A traditional and modern definition of the class Reptilia, including nonavian reptiles and birds, with crocodilians and birds belonging to the clade Archosauria within Reptilia.

Class Reptilia

A class of animals that includes turtles, lizards, snakes, crocodilians, and birds.

Order Testudines

Turtles

Lepidosauria

A superorder of reptiles that includes tuataras, lizards, and snakes.

Archosauria

A group of reptiles that includes crocodilians and birds.

Ectothermic

Animals that rely on external sources of heat to regulate their body temperature.

Tetrapods

Animals with four limbs.

Keratin

A fibrous structural protein found in reptiles, amphibians, and mammals, forming structures like scales, feathers, and horns.

Chitin

A tough nitrogenous polysaccharide found in arthropods, mollusks, and annelids.

Testudines

dorsal carapace with ventral plaston (breastplate) inner layer of bone, bony layer is fused ribs vertebrae and other bones

testunides reproduction

Oviparous, internally fertilize, lay shelled amniotic eggs in the ground and abandon

Lepidosauria squamata

Lizards and snakes, have body covered in scales and kinetic skulls

Kinetic skull

Skull specialization in snakes and lizards for swallowing large prey, allowing for a wider range of motion.

lizards

Paraphyletic group, four limbs and movable eyes, ectothermic, mostly in warm climates

snakes

Monophyletic limbless group, short vertebrae that are wider, no move able eyelids or external ear openings, very kinetic skull

Crocodilia

The order of reptiles that includes alligators and crocodiles, closely related to birds, elongated and robust skull, wide and powerful jaw

crocodilian reproduction

Oviparous, lay 20-50 eggs buried, extensive parental care, female guards eggs and young for two years

Temperature-dependent sex determination (TSD)

A mechanism where an organism's sex is determined by the temperature at which the egg is incubated.

Tuataras

Lizard-like reptiles endemic to New Zealand, representing a lineage distinct from lizards and snakes.

Jacobson's organ

Tongue flicks into air and pull sent past the organ allowing smell with olfactory epithelium