Ch 14-25 Flashcards
What are the advantages to an Amniotic egg?
Protects developing embryo
– Development on land does not require it
– Requires internal fertilization and related reproductive structures
• sperm cannot pass through shell following egg deposition
• Includes three new extraembryonic
membranes: amnion, chorion, and allantois
What are the Extraembyronic Membranes of the amniotic egg and what are they for?
-Amnion surrounds embryo, protects it from
mechanical shock
• Chorion facilitates gas exchange and protects other membranes
• Allantois stores nitrogenous wastes of embryo
What does the shell do for the amniotic egg?
– Provides protection for embryo
– Serves as medium of gas exchange
– More or less rigid due to deposition of calcium
Why did the amniotic egg develop?
• Resistance to desiccation
– Use of marginal environments unavailable for non-amniotes
• Improved respiratory capacity and increased
structural support
– Exchange gases more efficiently
– Better protected developing embryo
– Facilitated evolution of large body size…?
• Egg size and adult size correlated
What are Synapsids and Sauropsids?
• Earliest amniotes had few derived terrestrial characters
• Each lineage evolved independent solutions to challenges of life on land
– Conflict of locomotion and respiration
– Thermal insulation and endothermy
What were some problems that an early amniote had?
Rib Ventilation
• Costal muscles (derived hypaxial muscles) move ribs, expanding thoracic cavity
• Creates pressure differential strong enough to draw air in down the trachea
Locomotion and Respiration
• Problem: hypaxial muscles that help with breathing were also needed for locomotion (lateral undulation) in earliest amniotes
• Created physiological conflict: impossible to run and breathe at same time
What happened when Primitive Amniotes ran?
- When running, axial muscles compress one lung as other expands
- Little expiration of old air and intake of new air
- Sprinting constrained to short distances
How did Synapsids run?
• When running, bend vertebral column
- Compression of lungs generates positive pressure:
forces air out
- Straightening expands lungs generates negative
pressure: causes air to fall in
- Gait and breathing are synchronized
What is bipedalism?
• More derived forms (birds) exhibit bipedalism
– Axial muscles do not contribute to locomotion
– Resolves conflict of locomotion and respiration
What is Endothermy and why did it evolve?
• Maintenance of elevated body temps due to metabolic activity rather than external heat
• Requires high metabolic rate and insulation
– Lack of either prevents endothermy from evolving
• Thermogenic opportunity model
– Higher body temps permitted nocturnality
• Warmer-is-better model
– Physiological and biochemical processes run faster or more stronger at warmer internal temperatures
How does Heat Retention in Synapsids work?
Mammals evolved hair
– Increases whole body insulation
– Originally primarily sensory structures (vibrissae)
How does Heat Retention in Sauropsids work?
• Feathers initially served as display features
– Secondarily modified for insulation
What is Temporal Fenestration?
• Amniotes categorized by # of skull fenestrae
– Each fenestra has bony arch (apse) beneath it
– Apse lost in derived groups
• Provide room for jaw muscles to bulge
What are the characters of Temporal Fenestrae
in Anapsid?
: no fenestrae, thus no temporal arch
– Primitive condition for amniotes
– Also seen in modern turtles
• Probably derived from diapsid condition
What are the characters of Temporal Fenestrae
in Synapsid?
one fenestra
– Modern mammals
– Extinct “mammal-like reptiles”
What are the characteristics of Temporal Fenestrae
in Diapsid?
two fenestrae
– Lepidosaurs (lizards, snakes, tuatara)
– Archosaurs (crocodilians, birds, “dinosaurs”)
What is the name of Turtles and how many species?
Testundines, • ~350 species
of turtle
What are the Characters of Turtle shells?
• Shell gives
distinctive body architecture
• Dorsal carapace and ventral plastron
• Outer covering of epidermal scutes
How are the Ribs of turtles different than other species?
• Bones of carapace underneath scutes – Ribs and vertebrae expand and fuse; – Only turtles have ribs external to girdles
What are the benefits to turtles hiding their head? What are the disadvantages?
• Hinged plastron allows head, appendages to be withdrawn tightly into shell
– Benefit: effective armor from many predators
– Cost: weight and structure limit mobility and niche diversity
What are the different type of hide-neck turtles?
• Cryptodires (hidden-neck turtles)
– Withdraw head into shell by bending neck into
vertical S-shape
– 75% of living species, and found on all
continents
• Pleurodires (side-neck turtles)
– Withdraw head into shell by bending neck
horizontally
– Now found only in Southern Hemisphere
What is the reproductive biology of turtles?
• All turtles are oviparous
– Eggs deposited in nests, covered by sand or soil
– Small species lay 4-5 eggs; large marine turtles can lay 100+ in single event
• Many species exhibit temperature-dependent sex determination (TSD)
– Offspring sex a function of background temps experienced during embryonic development
– Change in offspring sex typically occurs across a narrow range (3-4°C)
What are the different types of TSD?
- Type Ia: males at low temps, females high
- Type Ib: females at low temps, males high
- Type II: females at high and low temps males intermediate
- What is advantage to linking offspring sex to environmental temperature…?
- Females may be able to assess sex frequencies in population, then select nest site more likely to generate offspring of rarer sex
Why is turtle conservation important?
• Delayed reproduction limits capacity of population to recover from decline quickly
• Largest turtles endemic to small islands
– Vulnerable to habitat disturbance and invasive species
• Harvesting of turtles for food and traditional medicines, especially in China and SE Asia
– Most species in region are highly threatened
• Illegal collection for pet trade
– Largest markets in N. America, Europe and Japan
– Rarest species command highest prices, putting further pressure on most endangered species
• Skew in offspring ratios due to effects of global warming on TSD
– May generate too few males or females to keep populations viable
What is the Diapsid skull in lepidosaurs?
• Two temporal fenestrae
• Seen in all lepidosaurs (lizards, snakes, tuatara) and most archosaurs
• Tuatara show the ancestral “classic” form
– Other groups show variations
What are Lepidosaurs?
• Largest group of non-avian reptiles (>10000 sp.)
– Lizards (6500)
– Snakes (3600)
– Tuatara (1)
• Important mid- and high-trophic level vertebrates wherever they occur
What is the General Biology of Lepidosaurs?
• Largely terrestrial but have exploited virtually all forms of habitat available
• Reduction or loss of limbs is common (>60 times!)
• Limblessness associated with life in fossorial and grassland habitats
- Decreases resistance to moving through soil
- Easier to maneuver around vegetation
• Skin covered with epidermal scales
– Prevents desiccation
– Shed periodically
What are Rhyncocephalia (Tuatara)?
• One living species endemic to New Zealand
• Superficially resemble lizards but morphologically primitive
• Restricted to islands off New Zealand coast
• Eliminated on mainland following human settlement
– High predation from introduced animals
• Low reproductive rate inhibits population recovery
What is the Reproductive Biology of Tuatara?
• Oviparous with internal fertilization
– No intromittent organ (unique for lepidosaurs)
– Male and female bring cloacae together (birds)
• Type Ib TSD
– Eggs incubated above 21ºC are mostly males; cooler temps produce females
What is Tuatara ecology?
• Unusual activity pattern for ectotherm
– Feed at night, when temperatures of (already moderate) temperate region even colder
– Body temps may be as low as 6ºC
– Warm up during day but not active then…why?
• Live in seabird burrows
– Primarily feed on seabirds, their eggs, and insects associated with seabird nest activities
– Hunting most effective at night, despite suboptimal thermal conditions
What is so interesting about lizard size?
- Dramatic size variation
- Dwarf chameleons (< 3 cm)
- Monitor lizards (~3 m)
What is Lizard Feeding Ecology?
• Small lizards mostly insectivores or carnivores
• Large lizards usually herbivores
– Plants have lower nutritive value
– Larger body needed to extract sufficient nutrients
How does lizard reproduction work?
• Sperm transfer by paired hemipenes
– Each connected to separate testis
– When mating multiply over short time periods, males will alternate inserted hemipene
– Helps prevent sperm depletion
• Oviparity is most common mode
– Females usually deposit soft, leathery eggs
– Not calcified like bird eggs
• Viviparity less common; limits reproductive output and constrains female locomotion
• More common in species at colder climates
– Females can better control embryonic temps by retaining eggs for longer period in cold habitats
What are Hunting Strategies in Lizards?
• Widely foraging – Active – Elongate body – Not territorial – Eat many sedentary, small prey • Sit-and-Wait – Little movement – Stocky body – Territorial – Eat few large mobile prey
What are characteristics of Geckos?
• Widely distributed in tropics and subtropics
• Many specialized for arboreality
– Toe pads provide exceptional climbing ability
– Setae adhere by subatomic van der Waals forces
• Largely nocturnal
– Exceptional in use of vocalization (rare in lizards)
– Used in courtship and aggressive social contexts
• Some colorful species are secondarily diurnal
What is so cool about Whiptails?
• Some species exhibit parthenogenesis – usually formed by hybrid crosses of two sexual species – Offspring are female clones – Arise from unfertilized ova • Common in arid western U.S. – Possibly adaptive when environments are stable – Limited genetic diversity constrains adaptation to climate change
What are characteristics of Monitors?
• Large, active predators of Old World tropics
– Includes largest living lizard (Komodo monitor)
– Capable of tracking relatively large vertebrate prey
• Closely related to snakes
• Deeply forked tongue permits acute olfactory capability
– Venom glands important in subduing prey
What are Serpentes (Snakes)?
• Morphologically, ecologically diverse clade of limbless lizards (3600 sp.)
What is snake feeding ecology?
• All snakes consume vertebrate or invertebrate
animal prey
– No snakes are herbivores
– Swallow prey whole
What are snake Feeding Specializations?
• Highly kinetic skulls that can move in 3 dimensions • 8 movable joints on each side of the skull Seize and Swallow • Most common form of prey capture – Probably primitive for snakes • Limits types of prey that can be safely consumed – Prey with claws and teeth can inflict injury Constriction • Loops thrown around body of prey • Tighten with each exhalation of prey • Suffocate prey or induce cardiac arrest Envenomation • Delivery of salivary gland products – kills prey and initiates digestion • Prey often released, then recovered by following scent trail – reduces chance of injury to snake
What are different Snake Dentition?
- Aglyphous: no fangs
- Ex: pythons, boas
- Ophistoglyphous: rear-fanged
- Ex: boomslang
- Proteroglyphous: fixed-fanged
- Ex: mamba, cobra
- Solenoglyphous: hinge-fanged
- Ex: vipers, rattlesnakes
What are Crocodilians?
- Important predators of tropical and subtropical aquatic habitats
- Only 27 described extant species
What are characteristics of Early Crocodilians?
• Evolved in Triassic
• Originally terrestrial predators
– long limbs, small body sizes
– Possibly bipedal
• Derived species (and living taxa) mostly aquatic
– small limbs, large body sizes
– Some extinct species exhibited gigantism
What are Crocidilian Foraging Strategies?
- Most frequently hunt in ambush in water
- Some catch prey on land by ambush or short bursts of running
- Aggregate to collect fish
- Use sticks as lures to capture wading birds
What are Characters of Crocodilians?
• Dorsal nostrils allow breathing by floating at surface of water
• Laterally-flattened tail helps propel
efficiently through water
- Legs held close to body to reduce drag
