Exam Flashcards
Ectotherm
Relies on external environment for heat
Endotherm
Make their own heat
What is the most important physiological variable for ectotherms?
Temperature
Temperature Tolerance Range
Range of temperatures between the boundaries of too hot and too cold
What do zebra-tailed lizards when the substrate is hot?
Curl up their toes and tails
Zone of Intolerance
Animal cannot survive and does not exist in this zone
Law of Tolerance Curve
Zone of intolerance at ends beyond the curve, survival zone at the ends of the curve, then growth, then greatest fitness in the centre (survival, growth, and reproduction)
Water and Salt Balance
Constant gradient/diffusion of salt and water in the body. Makes it more difficult to maintain internal balance
Why is a stable internal environment required for cells?
For metabolic processes
Water Flux
Water moves in an out of cells and bodies in a variety of ways
Why does water exchange differ between reptiles an amphibians?
Because their skin types differ
Routes of Water Transfer
Drinking (reptiles only), from food, across skin (amphibians mostly), metabolism, through highly vascularized tissues in the lining of the cloaca or esophagus
Uptake of Water by Amphibians
Across skin by osmosis and diffusion
Morphological Modifications of Amphibian Skin for Water Uptake
Smooth ventral skin in aquatic species and granular ventral skin of terrestrial species
Granular Ventral Skin
Dark spot on belly of terrestrial amphibians, made up of highly vascularized tissue for water uptake
Smooth Ventral Skin
Smooth, slippery skin of aquatic amphibians to help take up water
Granular Skin
Highly vascularized to enhance water absorption
Purpose of Costal Grooves on Salamanders
Channel water from underside to back
Uptake of Water by Reptiles
Drinking, methods vary by species. May drink from puddles, condensation drops in caves, or use body to channel water to mouth.
How do reptiles drink from condensation?
The water that evaporates in the desert is collected on the ceilings of caves, and the reptile drinks those drops.
How do reptiles use their body posture to drink?
Arch back and stretch out front arms to channel water down to their mouth
Rain Harvesting in Agamid Lizard
Honeycomb-shaped microstructures cover the surface of dorsal scales. There is a complex capillary system involved with the scale hinges. Water flow in these hinges is directed towards the mouth.
How do herps prevent water loss?
Must adjust behaviours and most would not last more than a day without them. Adjust daily/seasonal activity patterns. Seek humid retreats when inactive.
Anuran Burrowing and Water Retention
Burrow into the soil when it is moist and hunker down into a ball so there is less surface area for water loss. The soil is wet, they are protected by the wind, and the ground insulates them.
How does a Plains Spadefoot burrow?
Backwards, using horny/sharp/wedge-shaped feet that have a tubercle “spade” on them
How do Sandhill Frogs and Turtle Frogs burrow?
Frontwards, head-first, with small heads and strong arms
Aestivation
A dormancy period during seasonal drought and heat, like summer hibernation. Inactivity and metabolic depression help to prevent water loss.
Cocoon Formation in Anurans and Sirens
Make a cocoon of shedded skin layers around themselves, forming an impermeable sac with only their nostrils exposed, to reduce water loss during aestivation. When it finally rains after several weeks or months, they eat it.
How do anurans and sirens build their cocoons?
With a protective layer of skin cells. They shed and form a sheet around the body, and keep layering, and eventually form a thick opaque cocoon.
Measuring the Influence of Anuran Cocoons
Put frogs on wet and dry substrates to measure water flux. Cocooned frogs did not exchange significant amounts of water at either high or low substrate water potentials. The cocoon acts as a physical barrier to water exchange, not just to prevent evaporative water loss.
Aestivating Freshwater Crocodiles in Australia
Spend 3-4 months inactive, underground with no access to water
Aestivation in Turtles
Initially use water stored in bladder to osmoregulate. Blood chemistry parameters eventually increase. No metabolic depression other than regular responses to starvation.
Aestivation in Northern Spotted Turtles
Hyp: Avoid overheating and desiccation by aestivating when environmental temperatures increase.
Pred: Turtle body temp should be lower than ambient air and water temps during inactivity. Should choose aquatic sites for inactivity to avoid desiccation.
Conclusion: Avoidance of high summer temps and desiccation were not the reasons for aestivation behaviour, so may not really be aestivation.
Measuring Aestivation in Northern Spotted Turtles
Glued radiotransmitters on shell. Each has a different station. Should be representative of shell temperature. Faster beeps means hotter temperature of transmitter and therefore the shell (louder beep means the turtle is closer).
Northern Spotted Turtle Activity Cycle
Mating late April to mid June, nesting last 2 weeks of June, aestivation July to August in the hottest part of the summer, hibernation September to April in the winter
Waterproofed Frogs
Secretion of lipids/wax from skin glands, and the frog uses its hands to spread the lipids over the body surface to cover themselves in this wax to reduce water loss. Iridiphores are several layers thick and increase in number during dry season.
Iridiphores
Iridescent cells in skin of waterproofed frogs that reflect and send sunlight (and radiation) away to avoid overheating and stay cool
Water-Conserving Postures
Dehydrated or resting amphibians flatten their ventral surface close to the substrate (lay flat on belly) and fold arms and legs tightly underneath their body to minimize the amount of skin exposed to the air to prevent water loss.
Homeostasis
Maintenance of a relatively constant internal environment relative to variable external conditions. Requires some means of regulating body temperature, water balance, pH, and amount of salts in fluids and tissues.
Osmoregulation
Control of water and salt balance
Hypo-Osmotic Relative to Environment
On land and in salt water, the animal has more water/less salt than its surroundings, so water moves out of their body, potentially causing severe dehydration so they need to regulate it
Hyper-Osmotic Relative to Environment
In fresh water, the animal has less water/more salt than its surroundings, so water moves inward, potentially causing cells to burst so they need to regulate it
Reptiles in Saline Environments
Salt glands (nasal glands/lacrimal glands) aid in the removal of salt. Marine iguanas sneeze salt. Sea turtles/snakes shed salt through tears. Some reptiles move away for a bit when a saltwater tide comes in.
Anhomeostasis of Desert Tortoise
Concentrations of solutes in body increase with increasing dehydration. Huge bladder acts as a reservoir to draw from until they are iso-osmotic to their environment to maintain homeostasis. Once they can no longer keep up, they let the solute concentration in their body go wild, drink like crazy, and flush it all out. When it rains, they drink a whole bunch again to store up their bladder for next time.
Anhomeostasis of Ctenophorus ornatus
Eat ants that have high sodium content, but the only way to secrete sodium is with urine, requiring a substantial loss of water. During dry spells, these lizards allow sodium to accumulate (2x) in their extracellular fluids, then they drink a bunch and flush it out when water becomes available.
Respiration
Process by which animals acquire oxygen. CO2 and H2O are produced as byproducts and must be eliminated.
Respiratory Surfaces
Heavily vascularized surfaces of one or a few cell layers between capillaries and exchange medium (air or water)
Respiratory Surfaces of Amphibians
Skin, gills in larvae, lungs in adults, buccopharyngeal cavity, cloaca. Most use more than one, switching or using 2 at once. Skin, cloaca, and buccopharyngeal cavity can be used in both air and water.
Respiratory Surfaces in Reptiles
Lungs, cloaca. Cutaneous respiration is rare and limited.
Which herps have gills?
Amphibian larvae and some aquatic salamanders (neotenic)
Gills as Respiratory Surfaces
Used for breathing in water. Highly branched to increase surface area, but lack of skeletal support means that they can only be supported in aquatic medium. Water allows them to spread out for more surface area exposure.
Gill Size/Structure
Long and feathery in pond types, medium in stream types, short and less filamentous in mountain brook types. Stagnant waters have less O2 and less water moving over the gills, so they need more surface area exposure. Long gills will also get ripped off in fast moving waters.
Buccal Cavity and Pharynx as Respiratory Surfaces
Membranes of mouth and throat are permeable to O2 and CO2. Important for species submerged in water for long periods, like turtle hibernation.
Skin as a Respiratory Surface
Skin folds increase surface area for gas exchange
Theories for Growth of “Hairs”
Help males sustain high activity associated with breeding. Greater surface area for gas exchange to allow males to stay with their eggs in underwater nests. Hairs release oxygen to aerate eggs during embryogenesis. Hairs serve as mechanical protection from claws in aggressive male-male interactions.
Lungs in Amphibians
Positive-pressure buccal pump. Floor of mouth is dropped and raised. When dropped, nostrils are open and air is taken into buccopharyngeal cavity and stored. Floor of mouth is elevated, and nostrils close and glottis is opened, expelling deoxygenated air from the lungs and forging oxygenated air into them.
Lungs in Reptiles
Negative-pressure thoracic aspiration. Elongate forms gave loss or reduction of a lung.
Lungs in Lizards
Use ribs and intercostal muscles to ventilate lungs. Sedentary lizards have few divisions in lungs, active lizards have complex lungs with many chambers to maximize surface area.
Lungs in Crocodiles
Liver acts as a plunger and presses against lungs
Lungs in Turtles
Lungs and viscera in a single cavity in a hard shell. Skin and muscle at the anterior and posterior openings of shell provide the flexibility needed to change the volume of lungs to draw air in and out (can’t expand ribs). Breathing is partially facilitated by moving legs in and out of shell.
Lungs in Amphisbaenians
Right lung is absent
Lungs in Snakes
Left lung is reduced. 2 regions in right lung-vascular lung in anterior part of body vascularized for gas exchange, and saccular lung posterior to vascular lung to regulate air flow.
Lungs in Tadpoles
Play a role in buoyancy regulation, like a swim bladder
Gas Exchange by Eggs in Water
Gelatinous material around eggs is a barrier to oxygen diffusion, but channels between eggs allow convective flow of O2-rich water so they are in loose clusters.
Gas Exchange by Eggs/Tadpoles in Foam Nests
Volume of foam decreases as water evaporates, decreasing O2 concentration, which may trigger tadpoles to drop from nest to water.
Gas Exchange by Eggs on Land
Pores extend through crystalline layer of rigid eggs. Gaps between fibres in flexible eggs.
SMR
Standard metabolic rate
Standard Metabolic Rate
Minimum energy consumption an animal needs to remain alive
