extreme biology lecture 4- animals tough climates Flashcards
what are the differences between earth and Venus?
earth=
Mean temperature 15 ºC
Orbital period 365 days
Synodic rotation 1 day
Surface pressure 1 bar
Axial tilt 23.4º
VENUS=
Mean temperature 450 ºC
Orbital period 225 days
Synodic rotation 117 days
Surface pressure 94 bar
Axial tilt 2.6o
Venus has no strong magnetic field (but Earth does) which means it lack protection from solar winds. Venus might well have had water oceans and a fairly conducive temperature in the past, but any water was stripped away many billion years ago and the atmosphere is now mainly sulphuric acid at intense pressure.
what is the giant-impact hypothesis?
It has been proposed that Earth collided with a Mars-sized planet around 4.5 billion years ago, something that would help explain its tilted axis
what does the tilt of the earth cause?
The tilt of the Earth means we get a seasonal distribution of solar radiation and temperature. Temperature is less evenly distributed than radiation as the landmass/water balance have a large impact here.
what 4 biomes are the coldest and warmest/driest places on earth?
-ice and snow
-tundra
-taiga
-deserts
what is obligate annual migration?
All individuals migrate each year, usually to the same general areas
when does migration occur?
-In highly seasonal climatic regions, annual migration can help animals avoid the harshest times each year
what is irruptive migration?
Opportunistic movements that are determined by the local conditions
what is partial migration?
A part of the population migrates, the remaining stays, but pattern is annual and generally fairly regular
what are the historic views of bird migration?
-Samoan and Greek descriptions of migration of birds dates as far back as over 3000 years ago
Aristotle had an interesting view on cranes…
‘Cranes migrate from the steppes of Scythia to the marsh-lands south of Egypt, where the Nile has its source. And it is here that they are said to fight with the pygmies; and the story is true, as there is actually a race of cave dwelling dwarfish men, and their horses are little in proportion too’ (History of Animals, about 400 BC)
-The exiled Swedish archbishop Olaus Magnus moved the crane story to Greenland, he also said that swallows spend their winter in lakes
-Hard evidence came in 1822 when the famous Pfeilstorch (arrow stork) was caught in Germany with a central African spear buried in its throat
what makes polar bears the masters of the cold?
Small surface area to body volume ratio-
Strongly reduces heat loss compared with smaller and less rounded animals
White, translucent fur- Provides camouflage in icy landscape making it easier to stalk and catch prey
Large, dimpled feet- Allows easier grip and spreads weight of the entire animal over a larger area
Acute sense of smell- Can smell prey hiding under the ice and at a far distance
thick fat and fur layers-Direct protection against the cold and also used as fuel during hibernation. Fat metabolism acts as water source
Water repellent fur-Water particles bead off, reducing the risk of water freezing on to the fur coat
Rear young in a den- Protects young from cold winds until most of their fur growth have finished
Closable nostrils- Prevents water from entering intonose when swimming and diving
what are thermophilic scavengers?
-Live in one of the hottest environments on Earth, feeding on victims of extreme heat
-Surface temperature reaches up to 70 ºC, their own thermal maxima is ‘just’ 53.6 ºC
-Minimize heat build-up by short foraging trips, elevated objects, and reflective hairs
Do not use pheromones to find their nest, instead navigate by ‘dead reckoning’ with an internal solar-compass and step-counter
-Spiralling search pattern used if nest is not found, in 1966 the US Air Force employed this method to locate a lost nuclear bomb
how do some animals manage the heat?
Deserts covers one third of all land area on EarthThe searing day-time temperatures put desert- living animals at a serious risk of overheating
Examples of tactics used to keep cool:
-Evaporation cooling
-Reflection
-Reducing contact
-Use of counter-current systems
-Insulation and localising fat stores
-Refuges
Finding enough water is another challenge that need to be solved to survive in a desert habitat
how do some animals deal with limited access to water?
-Darkling beetles (Tenebrionidae) in Namibia have evolved ways to access water in one of the driest deserts found anywhere on Earth
-The surface of their elytra (cover wings) have a texture that turn fog particles into droplets
-Their hindlegs are elongated to help them aligned against the fog drifting from the sea
what is extreme hibernation?
-Arctic ground squirrels live in arid arctic regions and normally hibernate from September to May
In extreme cases their body temperature drops to -2.9 ºC, but their brain stays just above zero
-Not fully understood how they survive freezing, but most likely by cleansing their blood of any potential ice nucleators to keep it supercooled
-The potential of keeping human tissues alive at sub-zero temperatures have made the squirrels the focus of ongoing organ transplant research
-Hibernation enable the squirrels to lower their annual metabolic costs to a manageable level in an environment where food is always scarce
what is the subnivean zone?
Subnivean habitats are where animals shelter within or under a snow pack, using its protection from wind chill outside, and the insulation that snow can provide through the air it holds keeps the temperatures higher than outside and stays around 0 ºC
-Some stay below all winter, others only as overnight shelter or during bad weather
Not accessible to large animals, or those that need large territories to find food
