Chapter 26 Amniote Origins & Non-Avian Reptiles and Chapter 27 Birds
Describe the general characteristics of the subgroup Lacertilia: Amphisbaenians (#1)
- "Worm lizards" that are highly specialized for fossorial (burrowing) life - Were in separate suborder; now considered highly modified lizards - Have long, cylindrical bodies, nearly uniform in diameter
Describe the features and significance of the amniotic egg.
- Allowed for the development of larger, faster-growing embryos, - Better support and movement of oxygen - Calcium in the shell can be absorbed by growing embryos for growing skeletal structures. - Amniotic egg helped eliminate the need to reproduce in water along with lack of filled larvae in all amniotes and internal fertilization in all amniotes.
What are the 4 membranes associated with the amniotic egg? What are their functions?
- Amnion: encloses embryo in fluid-filled space, providing cushioning and medium for growth - Allantois: forms sac to store metabolic wastes - Chorion: just under shell, highly vascularized respiratory surface - Yolk sac: Nutrient storage
Why are "reptiles" as traditionally defined, a "paraphyletic" group? How has cladistic taxonomy revised Reptilia to make it monophyletic?
- Because all descendants of their common ancestor are not included in one group. - Originally birds were in their own class, cladistic taxonomers put birds within the class Reptilia to make the group monophyletic.
How does the digestive system and metabolism of a bird reflect their ability to fly?
- Birds are voracious eaters with a high metabolic rate - Small birds need even more food per body mass - Birds have rapid and efficient digestive systems
How is the excretory system of birds adapted for flight?
- Birds excrete nitrogenous wastes as uric acid and is concentrated almost entirely in the cloaca where water is absorbed - Bird kidney is less efficient than a mammal kidney in removing ions of sodium
What is a nest parasite?
- Birds that lay their eggs in other bird's nests, such as cuckoos and cowbirds
Describe the functions of feathers.
- Contour feathers: provide form of the bird and flight feathers are contour feathers that extend beyond the body - Down feathers: Under contour feathers and have barbules that lack hooks and function as insulation - Filoplume feathers: Hairlike, degenerate feathers with weak shaft and tuft of short barbs, no known function - Powder-down feathers: Disintegrate and release talc-like powder to waterproof feathers
Describe the general characteristics of the subgroup Lacertilia
- Diverse group with terrestrial, burrowing, aquatic, arboreal, and some aerial members - Made up of geckos, Iguanids, chameleons, skinks, and other lizards - Most have moveable eyelids - Most have good day vision and some like the nocturnal geckos have good night vision - External ears but hearing is not important to most - Many survive well in hot and dry regions by not having glands in skin and produce semisolid urine - Lizards are ectotherms and require less energy than endotherms - Keep their body temp relatively constant through behavioral thermoregulation
Differentiate between feather color from pigments from color from structure.
- During growth, pigments are added to epidermal cells to produce color - Color can also come from how feathers are arranged and how they reflect or scatter light - Red, Orange, and Yellow come from pigment cells called lipochromes - Black, brown, red-brown, and grey come from melanin - Blue is from light scattering - Green is almost always from yellow pigment and blue feather structure
Explain why and how the squamate skull has been modified.
- Exceptional skull mobility of snakes is major factor in diversification - Most squamate skulls have been modified to a kinetic skull, with moveable joints
Explain the significance of the discovery of Archaeopteryx.
- First fossil that linked birds to dinosaurs.
Describe the typical traits of flightless birds and why flightlessness evolves.
- Flightlessness evolved many times among bird groups usually on islands with few terrestrial predators. - Continental flightless birds are usually large enough to outrun predators because their body weight is no longer a constraint
What is the function of Jacobson's organ in snakes?
- Forked tongue picks up scent particles and conveys them to this organ
Describe the general characteristics of order Testudines.
- Fossils first appear in Upper Triassic, 220 mya - Shell made of dorsal carapace and ventral plastron - Rigid shell that doesn't allow chest to expand to breathe - Uses abdominal and pectoral muscles as "diaphragm" - Some aquatic turtles can pump water in and out of vascularized body cavities to acquire oxygen - Small brain, less than 1% of body weight, but cerebrum is larger than that of amphibians - Sound perception is poor - Good sense of smell and vision - Are oviparous, with internal fertilization, females bury their eggs and then desert them - Low temps produce males - High temps produce females - Leatherbacks are the largest turtles - Land turtles may weigh several hundred kilograms - Low metabolic activity may explain their long life, believed to exceed 150 years. - Shell is an effective coat of armor - Box turtles have hinged plastron, allowing them to completely withdraw into their shell and close up tightly - Snapping turtles have reduced shells, can't withdraw but have powerful jaws for defense.
Describe the general characteristics of the subgroup Lacertilia: Monsters, Dragons
- Gila monsters store fat in tails to provide energy and metabolic water during drought - Gila monster, bearded lizard, Komodo dragons, and other lizards have venom
How is eye position in birds influenced by trophic level (herbivores or carnivores)?
- Herbivores must avoid predators so their eyes are placed to each side to view all directions - Carnivores (Birds of prey) have eyes directed forward which provides better depth perception
Explain how temperature affects reproduction in crocodilians.
- High nest temps produce males - Low nest temps produce females
Describe the structure of feathers.
- Hollow quill emerges from skin follicle and continues as a shaft or rachis, bearing numerous barbs - Up to several hundred barbs are arranged to form a flat, webbed surface, the vane - Each barb resembles a mini feather
Explain how temperature affects reproduction in turtles/tortoises.
- In some turtle families nest temperature determines sex of hatchlings - Low temps produce males - High temps produce females
The decline of Tuatara populations is caused by what 2 factors?
- Intentional human actions - Introduction of nonnative species that preyed upon tuatara or destroyed their habitat
What is meant by a "kinetic skull" and what benefits does it confer? How are snakes able to eat large prey?
- Kinetic skull means its very flexible and the lower jaw bones are loosely joined which allows them to unhinge their jaw to be able to fit larger prey inside their mouths. - They can also breathe while swallowing
Differentiate between the two suborders of squamates.
- Lacertilia (formerly Sauria)- lizards and amphisbaenians - Serpentes- snakes
Distinguish between the 4 common types of snake locomotion.
- Lateral undulation: S-shaped movement that pushes against rough ground and water; is the most typical movement pattern - Concertina movement: Braces s-shaped loops on tree or in narrow passage and extends most of body forwards - Rectilinear movement: straight movement using minute lifting of consecutive rib, used by large snakes when stalking prey - Sidewinding: Sideways looping by desert vipers that "walk" them across loose sand
List some of the threats facing marine turtles.
- Lights preventing young from reaching water - Nest predation, lack of nest sites - Hunting/ poaching - Entanglement in trash - Bycatch from ocean fisheries - Pollution and oil spills
How do bird bones differ from other bones?
- Modern birds have light, delicate bones laced with air cavities, Pneumatized bones - Very strong - Total weight of bird's feathers may outweigh skeleton
Differentiate between monogamous and polygamous (including polygyny and polyandry) mating systems
- Monogamy, over 90% of birds mate with one partner each breeding season, some like geese or swan have one partner for life, both male and female care for young - Polygamous, birds that mate with two or more partners each breeding season >> Polygyny, most common form of polygamy, one male mates with. many females >> Polyandry, relatively rare in birds, a female mates with several males, male incubates the eggs
How is the respiratory system of birds adapted for flight?
- Most efficient vertebrae respiratory system - Interconnected air sacs (separate from the lungs) serve as reservoirs for fresh air
Describe the general characteristics of the subgroup Lacertilia: Amphisbaenians (#2)
- Most lack any trace of limbs - Move backwards almost as well as forwards, using rings of skin similar to earthworms - Found mostly in tropics, one species in Florida
Describe the general characteristics of the order Squamata
- Most recent and diverse of diapsids - 95% of living non-avian reptiles - Kinetic skull with moveable joints - Exceptional skull mobility of snakes is major factor in diversification - Two subgroups: Lacertilia (lizards and amphisbaenians) and Serpentes (snakes) - Reproduce with Viviparity, evolved at least 100 times by increasing the length of time eggs kept in oviduct, often associated with cold climates, protects young from predation
Describe the three general methods snakes use to acquire prey.
- Most swallow whole - Use venom - Constrict
What are the advantages that flocking behavior provides?
- Mutual protection from enemies - Greater ease in finding mates - Less opportunity for individual straying during migration - Mass huddling shares body warmth
Differentiate between neurotoxins and hemorrhagic venoms.
- Neurotoxins act on the nervous system, typically causing blindness or inhibiting respiration - Hemorrhagic venoms break down blood vessels causing blood to leak into tissue spaces
Describe the general characteristics of the subgroup Serpentes: Snakes
- No limbs; most have lost pectoral and pelvic girdles (except in pythons, boas, etc) - Many vertebrae, shorter, wider than other tetrapods-allows undulation - Eyes have reduced mobility, protected by permanent corneal membrane (no lids), and most (except arboreal snakes) have poor vision - Able to eat prey several times their own diameter by: Skull is highly kinetic, lower jaw bones loosely joined, can breathe while swallowing - Lack external ears - Chemical senses are main senses used to hunt prey - Reproduction: most are oviparous and lay shelled eggs, some are ovoviviparous (American pit vipers), and few are viviparous (with a primitive placenta) - Jacobson's organ is a pair of pits in roof of mouth, lined with olfactory epithelium, forked tongue picks up scent particles and conveys them to this organ - Move with either Lateral undulation, Concertina movement, Rectilinear movement, or sidewinding - Most snakes swallow prey alive, typically eat smaller prey to not get injured - Snakes that kill prey by constriction can eat larger prey items - Vipers, elapids, sea snakes, mole vipers, and colubrids are snakes from 5 different families that all kill prey with venom - Saliva of harmless snakes contains limited toxins - Most snake venoms are complex combinations of venom types: Neurotoxins and Hermorrhagics - Venom toxicity is measured by median lethal dose in laboratory animals, called LD50
Describe the general characteristics of the order Sphenodonta
- Only 2 living species in New Zealand - Often live in burrows with petrels (birds) - Slow growing, long-lived, low reproductive rates - Skull nearly identical to diapsid skulls of 200 mya - Well-developed parietal eye beneath skin that can register changes in light intensity
Describe the general characteristics of the order Crocodilia: Crocodiles and Alligators
- Only surviving non-avian reptiles of archosaurian lineage - 3 families of modern crocodiles: Alligators and caimans, Crocodiles, and Gharial - Long, well-reinforced skull and jaw musculature for a powerful bite - Have theocodont dentition, the teeth are set in sockets - Have a complete secondary palate, a feature only shared with mammals - 4 chambered heart - Alligators and Crocodiles are Oviparous, usually laying 20-50 eggs in a mass of vegetation
Describe the general characteristics of modern birds.
- Over 10,500 species - Live in all biomes - Have feathers which are unique and essential features - All birds have horny, keratinized beaks - All birds are oviparous - Birds and traditional reptiles share many similarities - Skulls are fused into one piece
Distinguish between paleognaths and neognaths.
- Paleognathae are birds with a flat sternum such as ostriches, rheas, kiwis, tinamous, and emus - Neognathae are birds with keeled sternum, which all other birds have (most of which are able to fly)
Distinguish between altricial and precocial young, and describe the advantages of each.
- Precocial birds- feed, run or swim as soon as they are hatched, these are chickens and most water birds, and they have a greater ability to find food, escape from predators - Altricial birds- naked and helpless at birth; must be fed in nest for week or more, reduced parental investment in eggs (less yolk), young grow faster
Explain why lizards thrive in hot dry areas.
- Reduce water loss by having no glands in skin - Conserve water by producing semisolid urine
How are non-avian reptiles different from amphibians?
- Rib ventilation of the lungs by either expanding the thoracic cavity or pulling the liver aside -Thicker and more waterproof skin, more keratinized - Better developed lungs that have more surface area and draw air, some have cloaca, pharynx, or cutaneous respiration - Tough, dry scaly skin to protect against desiccation and physical injury, thicker epidermis, the dermis contains chromatophores, epidermal scales made of beta keratin - Amniotic egg - Jaws of nonavian reptiles efficient at applying crushing or gripping force on prey and muscular and mobile tongue - Efficient and versatile circulatory system, higher blood pressure than amphibians, reptiles have 3-chambered heart, crocodiles have a 4-chambered heart - Efficient strategies for water conservation, non-avian reptiles secrete nitrogenous waste as uric acid - More complex nervous system, the brain of non-avian reptiles is small compared to other amniotes, have good vision, Jacobson's organ in snakes and many lizards
Describe the similarities of among birds and non-avian reptiles.
- Skulls meet first neck verterbra with single bony knob - Single middle ear bone - Lower jaw composed of 5 or 6 bones - Excrete nitrogenous wastes as uric acid - Similar yolked eggs
Why can snake bites with less toxic venom still be dangerous?
- Snakes with less potent venom may: 1) inject more venom like the King cobra 2) Bite numerous times like the Black mamba 3) Some bites are deeper than others, or might hit a vein
What does Anapsid, Diapsid, and Synapsid mean?
- Synapsid is a skull with one pair of temporal openings low on the cheeks and happens in mammals and their extinct relatives - Anapsid is a skull with no temporal opening behind the eye orbits. Modern turtles have anapsid skulls but probably had diapsid ancestors - Diapsid is a skull with two pairs of temporal openings, this type gave rise to all other traditional "reptiles" and to birds.
Explain the function of the pits in pit vipers.
- The "pits" have nerve endings that are sensitive to heat emitted by warm-bodied birds and mammals
Why are tuataras (sphenodon) of special interest to biologists? Why are they rare?
- They are special because the sphenodon has one of the slowest rates of morphological evolution in vertebrates - They are rare because there are only 2 living species which are located in New Zealand
Why do many bird species migrate and how do they navigate during migration?
- To exploit seasonal changes in abundance of insects and avoid bird predators - Navigate chiefly by sight, can navigate using Earth's magnetic field, and can use celestial cues
Most snakes and lizards are oviparous, but some are ovoviviparous or have placental viviparity. In what climate is viviparity most common?
- Viviparity is most common in cold climates
How is the bird skeleton modified to allow for flight?
- Wings provide both lift and propulsion - Sternum has large keel to anchor flight muscles - Fused clavicles form furcula (wishbone) - Bones in forelimbs are highly modified for flight - Vertebral column is very rigid and fused, except cervical vertebrae - Caudal vertebrae (tail) fused into pygostyle
Explain why viviparity may be relatively common among the squamates.
-Perhaps to help regulate temperature of developing young and protect eggs from predation
Explain the structure and function of the shell in turtles/tortoises, and how it affects breathing.
-Shell is made of dorsal carapace and ventral plastron - Outer horny layer of keratin and inner layer of bone (fused ribs, vertebrae, and dermally-ossified elements) - Rigid shell, cant expand chest to breathe - Use abdominal and pectoral muscles as "diaphragm" to: 1) Increase or decrease abdominal cavity volume 2) Visible bellows-like movements at "limb pockets" 3) Movement of limbs while walking helps ventilate lungs
Explain the two general hypotheses for the evolution of flight in birds.
1) "Ground-up" (cursorial) hypothesis- running birds with primitive wings to snare insects 2) "Trees-down" (arboreal) hypothesis- Birds climbed trees, leaped out, parachuted and glided down, finally powered flight
How is the nervous system of birds adapted for flight?
Brain has well developed: - Cerebral hemispheres- size increases w/ intelligence - Cerebellum- coordinating center - Optic lobes- comparable to visual vortex of mammals
What are the 4 types of bird wings?
Elliptical- birds that must maneuver in forested habitats High-speed wings- birds that feed on the wing or make long migrations, these wings sweep back and taper to slender tip which reduces "tip vortex" turbulence Active (Dynamic) soaring wings- Albatrosses and other oceanic soaring birds have long narrow wings adapted for dynamic soaring, these birds exploit the highly reliable sea winds and air currents of different velocities Passive soaring (high-lift) wings- Eagles and other birds of prey that carry heavy loads need wings with high lift at low speeds, many are land soarers with broad wings
