EVSC20004 Lecture 22: Polar Regions II
21 Jun 2018
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Polar Regions II: Adaptations and the Seasons
1. Introduction the Arctic and Antarctic
2. Antarctica is cold- why live there?
3. Key physiological, physical and behavioural adaptations to the cold
4. A year in the Antarctic: Biology and the seasons
Fast facts:
Decapods are unable to regulate magnesium levels below around 1o, therefore
Antarctica’s crab-eater seal does not eat crabs as there are no crabs (decapods) in
Antarctica. Instead, they eat krill using specialised teeth- consumes 20kg krill a day.
Polar bears live in the North (Arctic), and penguins live South of the equator (don’t
stay there all year round except for the Emperor penguin)
The sun is present for only 6 months of the year, the rest it is not there.
~70% of the world’s freshwater is frozen in Antarctic ice
Arctic (north) vs. Antarctic (south):
The sun’s influence (albeit weak) is similar at both poles, but is far colder in Antarctica
Average Antarctic winter temp is -50oC, colder than the colder winter night at the
north pole
Main reason is enormous difference in altitude: North pole is 1m above sea level,
south pole 29000m above sea level (highest)
Isolation: Arctic is frozen ocean surrounded by land, Antarctica is a frozen continent
surrounded by ocean
Antarctica has circumpolar current that ‘trap’s cold water/air
oAffects climate and biology
Differences in temperature and isolation have moulded very different animal and plant
communities
Arctic is milder and ‘less demanding’ than the Antarctic, but is still an extreme
environment
Both regions experience enormous seasonal differences: 24-hour summer daylight
to complete darkness in polar winter
Arctic accessible for colonisation (40+ land mammals) all year round, Antarctica has
none: Only Weddell seal stays all winter
Birds:
Emperor penguin is only bird to stay throughout winter in Antarctica
oOnly 20 species penetrate further south than 70 degrees
Arctic has 8 permanent resident land birds and 150 visitors
o100 of these species penetrate further north than 75 degrees
Fauna:
Antarctica has just 2 flowering plants (grass); south of 80 degrees are just lichens
Arctic has 90 flowering plants found as far north as 82 degrees
find more resources at oneclass.com
find more resources at oneclass.com
Antarctica:
The term ‘Antarctica’ refers to the continent itself
oAntarctica is the 5th largest continent (larger than the US and Mexico
combined)
oAntarctic refers to the entire southern polar region, including the ocean that
surrounds this continent
Only 2% of Antarctica is not covered by ice
oSub-polar islands (e.g. Macquarie islands) become very important for
breeding
There is a huge seasonal supply of food due to upwelling of nutrient rich waters and
24-hours of sunlight- therefore lots of photosynthesis
oSmall food-chain- this means those in the food-chain are able to consume
high energy food to generate warmth within
Antarctic food webs relatively simple: ‘efficient’ as fewer trophic links
reduce energy (10% law: On average, only about 10% of the energy
that is consumed at one level is converted to biomass- the rest is lost
to heat
oKrill is the major player in the food-web
Euphasisa species
Can live to 7 years and grow to 6cm
Krill are super abundant
Relatively large compared to other zooplankton, making them directly
accessible to large animals; efficient trophic transfer in food web
Huge animals, like whales, feed close to the bottom of food
web
Physiological adaptations of ectotherms (surviving the cold):
Don’t come into contact with ice (ideal nucleation point for growth of ice is an ice
crystal- touch ice, you freeze)- this is more behavioural
Depress freezing point of body tissues by controlling salt concentrations (sea water
freezes at -1.9o, compared to freshwater)
oRegulating how much ions come in and out of their gills
Glycoprotein anti-freezes in blood
oPrevent spread of ice crystals through the body
‘Slow growing, long lived’- cold slows everything (metabolic, enzymatic etc.)
oWandering albatross can live for over 50 years- ensures that all individuals
have multiple opportunities to breed (energetically costly to raise chicks- 1
chick per year is the average (low fecundity/abundance of offspring))
oMarine worm can live 3-7 times longer than closely related species
Thermal tolerance in polar species
oMetabolic rates, enzyme kinetic properties and protein structural flexibility
are all adapted to life in the cold
Because they’ve adapted, they don’t like it getting hot (seawater in
Antarctic varies -1 to 9-2oC)
find more resources at oneclass.com
find more resources at oneclass.com
Physical adaptations:
Complex heat exchange system
oEmperor penguin captures 80% of the heat it breaths out through its nasal
passage
Mammals and birds have blubber (insulates in water) and fur and feathers (insulate
in air)
Reduced surface area to volume ratios help limit heat loss
oAchieved through increased body size and compact shape (Smaller organs),
especially in endoderms (warm blooded animas)
Behavioural:
Animals can migrate to and from the Antarctic to avoid extreme cold and when ice
forms
Huddle together to keep warm to reduce collective surface area to volume ration
(e.g. penguins)
Don’t leave the sea so they aren’t exposed to extreme cold (water doesn’t get below
-2oC)- some animals enter the sea when the weather is bad
Example: Ice fish:
Completely lack haemoglobin as it is energetically costly to make, and so it is
replaced with glycoproteins
oCan survive without haemoglobin because the levels of dissolved oxygen is
really high (inversely related to temperature- colder= more dissolved oxygen)
Increase in blood volume, therefore greater cardiac output, increased
blood flow
Low blood viscosity (due to the lack of red blood cells)
Thin skin with lots of capillaries: allows for direct oxygen diffusion
across their skin (Also have gills but they also have this mechanism on
top of it)
Benthic (lowest level of a body of water) marine environments:
Many species have circum-Antarctic distribution
oFew fish with powerful jaws and no decapods (crabs, lobsters etc.) which
means that there are few shell-crushing predators in Antarctica
oAntarctic ecosystem resembles the Palaeozoic (350 million years)- top
predators are ribbon worms, starfish and sea spiders
oSea ice scours benthos
Sheltered bays have great diversity of life
Biology and the seasons
Sea ice formation arguably the greatest seasonal change on earth
Along with temperature, plays ta fundamental role in shaping polar life
Sea ice extent determines water and land accessibility
Water and land access required all year for some animals
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
1: antarctica is cold- why live there, key physiological, physical and behavioural adaptations to the cold, a year in the antarctic: biology and the seasons. Decapods are unable to regulate magnesium levels below around 1o, therefore. Antarctica"s crab-eater seal does not eat crabs as there are no crabs (decapods) in. Instead, they eat krill using specialised teeth- consumes 20kg krill a day. Polar bears live in the north (arctic), and penguins live south of the equator (don"t stay there all year round except for the emperor penguin) The sun is present for only 6 months of the year, the rest it is not there. ~70% of the world"s freshwater is frozen in antarctic ice. The sun"s influence (albeit weak) is similar at both poles, but is far colder in antarctica. Average antarctic winter temp is -50oc, colder than the colder winter night at the north pole.
