Lect 12 Flashcards
Thermoregulation
• The ability of a vertebrate to maintain it’s body temperature within a certain range (important for bio Chem rxns)
• Biochemical reactions in the body are optimized to certain temperatures (there’s an upper limit)
• Usually, reaction rates are higher at higher temperatures
Important for diff processes in body that have diff temp where work best
Thermoregulation types
• Heterothermy: Having a body temperature that fluctuates greater than 2°C (internal. Without large neg impact)
• Homeothermy: Having a body temperature that remains stable (internal 2°C range)
• Ectothermy: The primary source of heat is external to the body (can be hetero or homo but typically also het)
• Endothermy: The primary source of heat is from internal metabolism ( warmblooded, birds, mammals, endothermic tend to be homo but not always)
Pathways of heat transfer
Sun —> primary source oh heat, indirectly or directly
Overheated —> find shade to release heat
Lizard able to release some heat —> radiation also respiration provide little bit of heat loss heat control mainly beh
Sunlit rock tends to be hotter than atmospheric air temp
Behavioural thermoregulation
• Adapting activities based on environmental conditions
• Changing body position to maximize or minimize sun exposure
• Finding substrates that are sun- warmed or breeze-cooled
• Limiting activity to times of day when temperature is optimal
- inactive during middle of day or if it’s cold during night will be active during middle of day
Turned towards body, increased surface area increased heat
Turned directly into Sun, decreased surface area exposures, decreased heat
in a plant/bush/tree Cooling, may be due to more air currents
Find shade
Testudines
Diagnostic characters of turtles
Shell
• Carapace – dorsal shell
• Plastron – ventral shell
• Composed of bony elements with large keratinous scales covering (often don’t align 100% on bones underneath, overlap which provides extra support)
• Carapace derives from the ribs (endochondral (can’t replace as bony tissue)) with some dermal contributions (ones on side from ring, ones on top fuse with vertebra)
• Plastron derives from dermal elements with some endochondral contributions (with dermal layers expand until touch each other)
• Ribs and vertebrae fused to inside of carapace
Exception: Softshell turtles
• Have skin instead of keratinous scales covering shell
• Shell less ossified
- Lack peripherals – bony elements that form the edge of the carapace
- Plastron elements not fused to carapace
Still have plastron
Skin/soft tissue grows over the carapace/plastron
Testudines
Diagnostic characters of turtles
Head
• Retract head and limbs inside shell
Cryptodires: “hidden necks”
- Neck bends into S-shape in vertical plane
- More diverse group today
Pleurodires: “side necks” (pleuro means side)
- Neck bends to one side or the other side
• Sometimes the scaly (will be bigger on these legs) legs are also used to seal the openings in the shell
Testudines
Diagnostic characters of turtles
Muscular sling ventilation
• Ribs are fused to carapace
• Sauropsid lungs are partially rigid
• Flexible ventral surface of lungs attach to guts (muscular sling)
• Muscles around inside of shell draw the gut down or press it up
- This expands or compresses the volume of the lungs, drawing air in or forcing air out (sim to diaphragm of humans)
• Some aquatic turtles have gas exchange in their mouth or cloaca
Turtle diversity and distribution
Pleurodira
• Three clades across the Gondwanan continents (South America, Africa, Australia)
• Freshwater habitats only
Side bending necks
Turtle diversity and distribution
Cryptodira
• Eleven clades across all continents except Antarctica
• Inhabit diverse ecosystems from oceans, to islands; from swamps, to deserts
Carapace shape
• Profile of carapace tends to correlate with habitat
• Terrestrial tortoises have taller, more domed carapaces
• Aquatic turtles tend to have lower, smoother carapaces (reduces drag)
Turtle reproduction
Species recognition
• Some species have brightly-coloured markings
B/c have sharp vision
Could be a combo of light and dark markings
They focus on the dark marking spaces not the bright ones?
Turtle reproduction
Courtship rituals
• More common among terrestrial species
• Males compete by ramming each other
• Head bobs used as signals
Ramming / head butting
Turtle reproduction
Turtle nests and eggs
• All turtles oviparous
• Females dig nests for leathery-
shelled eggs
Environmental sex determination:
• Temperature and humidity (not genetics) determine sex of hatchlings (for most part)
• Type I: low temps = males and high temps = females
• Type II: temperature extremes = females and intermediate temps = males
Turtle pops will skew towards females due to climate change
Turtle reproduction
Parental care in turtles
• Generally, non-existent
• Some tortoises guard nests
briefly after eggs are laid
• One pleuronectid (Arraus) do have parental care
• Females remain near beaches where eggs were laid
• Females and hatchlings vocalize during/after hatching
• Females guide hatchlings along rivers to flooded forests to feed
