Amniotes Flashcards
Who is an amniote
- Reptiles (sauropsids)
-turtles
-lizards and snakes
-crocodiles
-birds - Synapsids
-mammals
When did amniotes first appear
Carboniferous era only 20my after first tetrapod
Major radiation in the Permian
3 synapomorphies of amniotes
-amniotic egg
-characteristics of their skin
-ventilation: rub based ventilation or costal ventilation
Non-amniotic egg (amphibians) parts
-embryo with yolk sac originating from embryo (extra-embryonic membrane)
-Vitelline membrane
-thick-jelly layer (remains moist in water)
Gas exchange in the Non-amniotic egg is _______
Limited
-oxygen has to diffuse from water through the jelly like layer to the fluid surrounding the embryo to the embryo itself. Carbon dioxide has to do opposite.
-movement is mostly passive through diffusion but exchange of gases is slow
Amphibia embryos have a _____ metabolic rate
Low
-hatch at earlier developmental stage so they do not asphyxiate from lack of oxygen
Amniotic egg structure and functions
-shell: semipermeable protection that limits water loss and allows gas exchange
-albumin (egg white): shock absorption
-chorion: high vascularization gas exchange
-Allantois: stores metabolic waste, highly vascularized gas exchange
-amnion: inner case that encloses the embryo, protective and stable fluid environment
-yolk sac: energy
Which parts of the amniotic egg are extra-embryonic membranes?
Chorion
Allantois
Amnion
What extra-embryonic membranes are present in reptiles and mammals
Chorion
Allantois
Amnion
Amniotic egg advantages
-resists dedication
-source of calcium
-mechanical protection
-increased capacity for respiration: membranes specialized for gas exchange
-larger, faster growing embryo
-bypass larval stage
Amniote form of reproduction
Internal fertilization: eggs are fertilized in female before shell or placenta form
Amniote skin
External layer of skin and scales consists largely of keratin and lipids (keratinized cells=hard dead layers of epidermal cells)
-waterproof skin
-forms protective layer
-repels heat, water, physical attack and microorganisms
-conserves moisture
Amniote changes in respiration
Lungs are primary organ of ventilation in most amniotes. Lungs of amniotes have more surface area than the amphibian lung. Amniote a rely on different mechanisms to ventilate lung.
-costal ventilation
Costal or rib ventilation
Moving lungs up and down to inflate and deflate
Buccal pumping in amphibians
- Inspiration: nostril open, glottis closed, depress floor of mouth which expands Buccal cavity and draws air into mouth
2.inspiration 2: nostrils close, glottis opens, lifts floor of mouth, which pushes air into lungs.
3.expiration: depress floor of mouth, fill with air - Expiration 2: nostrils open, glottis closes, lifts floor of mouth which pushes air out through nostrils
Intercostal muscles
Located between ribs, move chest wall
-external intercostal muscles raise ribs, expands chest cavity and lungs, drawing in air (inhalation)
-internal intercostal muscles depress ribs and decrease space in chest cavity, forcing out air (exhalation)
Costal ventilation if more effective at______than Buccal pumping
Eliminating CO2 from lungs
Enabling Independence from cutaneous respiration, permits thicker skin that conserves water
3 important synapomorphies of amniotes
- Amniotic egg
2.skin
3.Respiration (intercostal)
Temporal fenestration
Holes in the head posterior to the orbit
-has two apsids or arches called temporal bar (arch) lying below and between holes
Diapsid
Two temporal archs in a skull
All living reptiles
Anapsid
Synapsid
Diapsid
Without arch
-ancestral amniotes, ancestral sauropods
Single arch
-mammals, extinct synapsids
two arches
-lizards, snakes, crocodiles, birds
What kind of fenestra do turtles have?
Living turtles have no opening, but are still considered diapause because extinct turtles had two openings. Secondarily derived trait to not have them.
What is the name of the group that turtles belong to
Testudines
Oldest potential ancestor of turtles and why was it significant to find
Eunotosaurus from the Permian had a diapsid skull atypical of extant turtles and it had no shell.
Carapace
Plastron
How are they both made
Incorporates ribs and spine vertebrate to make up top shell of turtles
Bottom shell of turtle that evolved separately
Made of bone that is covered with epidermal scutes.
Can turtles use costal ventilation?
No-shell prevents turtles from costal ventilation because ribs are fused to the carapace and turtles have no intercostal muscles.
What do turtles do to breathe
Muscles (abdominal oblique and serratus) expand the viscera cavity, which lowers the viscera and results in the lungs expanding and inhaling air.
To exhale, other muscles (transverse abdominis and pectoralis) contract the visceral cavity, which pushes the viscera up-and that deflated the lungs
Extant turtles belong to which lineages
Pleurodires-or side necked turtles that retract neck to the side and live in the southern hemisphere and only in freshwater
Cryptodires-hidden necked turtles that pull neck straight back and live in terrestrial, freshwater or marine habitats worldwide
Where do cryptodires move when seasons change
Terrestrial: bottom of ponds
Marine: greater distances to locate species areas for nesting or fessing
Physical adaptations that related to habitat of turtles
Terrestrial: shell domed, feet adapted for digging or walking
Marine: she’ll is reduced in size and streamlined to reduce water resistant. Epidermis is softer and more flexible, but carapace underneath is still hard. Flippers help propel on water.
Freshwater: shell more streamlined than terrestrial. Often walk on lane and dig so they have legs and feet with claws
All turtles have this physical adaptation
Camouflage
Turtle courtships may involve….
Colours, olfactory signs, visual displays, vocalizations, well endowed males
Are turtles viviparous or oviparous
Oviparous-lay eggs, typically in a nest that is buried in sand
Hatching and navigation of turtles
-turtles vocalize in their eggs to synchronize emergence from the egg )many turtles on the beach reduce the probability that any individual will be eaten)
-newborns walk downslope to the water and follow the light (moon) to navigate to the sea, then swim directly into waves. Use magnetic fields to travel and return to hatching beach to next several years later.
No parental care after hatching!!! Except Amazon river turtle
Mechanisms underlying Temperature Dependent sex determination of turtles
-environmental conditions during embryological development (middle third) determines the sex, not environmental conditions at fertilization
-in most turtles, females hatch at higher temps except snapping turtles where males are produced at intermediate temps and females at extremes
-intersex turtles may be born at intermediate temperatures. Some suggest they become male, but sometimes gonads are still undifferentiated months after brith.
Adaptive benefit of temperature sex determination
Turtles that evolved a sex determination strategy resulting in the birth of female offspring at higher temperatures develop faster in eggs, may hatch earlier, have more time to grow bigger as the season progresses and can produce more eggs which results in higher fitness
How does climate change affect turtles
Result in higher temperatures and therefore may cause female-biased populations to be produced. The low number of males make it difficult for members of populations to find a mate.
Direct threats to turtles
-by catch
-hunted for meat
-hatchling walking away from ocean because of bright street lights
-consuming plastic
Turtle life history type
Slow
Tuataras were common in what era?
Squamates (lizards and snakes) expanded during what ear
Triassic and Jurassic
Cretaceous (after Mesozoic)
What lead to the demise of tuatara populations
They live in new Zea lane where there are no rodents or other egg predators. But invasion of rats, cats and foxes causes their pops to decline.