Lecture 6/7 Adaptations Flashcards
What must plants and animals overcome in boreal conditions (3)
*cold
*Drought
*low nutrients
What happens to plant tissue when water freezes (3)
Frozen water expands 9% in volume, which
injures cells in 2 ways:
1) by rupturing the cell membranes
2) by messing up the permeability of those
membranes
How do Boreal plants escape frost damage (2)
Extra-cellular freezing - antifreeze accumulates inside cell walls
supercooling - lowering the temperature of water below its potential freezing point, without it becoming a solid
How do cold temps affect animals (3)
*Food scarcity – plants die off or buried (endotherms need more food to burn for heat
production)
* Metabolism disrupted.
* Freezing. Ice crystals cause damage. Cells dehydrate
Acclimation vs adaptation (3 each)
Acclimation
– Non-heritable modification of characters
– Caused by exposure to environment
– Changes readily reversible
Adaptation
– Accumulation of genetic changes
– Increases survival or reproduction in a particular environment
– Not readily reversible
Evolutionary vs physiological adaptation (3 each)
Evolutionary Adaptation
– Accumulation of genetic changes
– Increases survival or reproduction in a particular
environment
– Not readily reversible (but can be over many Generations)
Physiological Adaptation
– Organism adjusts to a new environment
– Does not involve evolution – phenotypic plasticity
– Changes not reversible
Ectotherms 2 major strats
Freeze avoidance
Freeze tolerance
Freeze avoidance (6)
*Water-impermeable exoskeleton or epidermis Keeps soft tissues away from environmental ice
* May involve cocoon or wax coating
*Body removes ice nucleators (particles that could form ice)
*Supercooling chemicals present
*still lose water, can become dehydrated
*high supercooling point (cant tolerate very much)
Freeze Tolerance
*Very low super cooling point, extremely high cryoprotectants
*often seen in animals that can’t avoid coming into contact with ice (freeze avoidance doesn’t work).
*glycerol binds to water = water is not lost, avoid dehydration
Endotherm 3 major strats
Migration
reduce heat loss (stay warm)
Dormancy
Dormancy (2)
Torpor = entry of animal into hypothermia with behavioral inactivity.
Hibernation = sustained state of torpor, entry to and exit from which is governed by internal signals together with exclusively seasonal external cues.
Hibernation (4)
*During hibernation, cell processes slow down = <5% of normal ATP turnover
*Pre-hibernation need to eat lots and lots (hyperphagia). Gain up to 40% of body mass
* Need polyunsaturated fats
* Find hibernaculum (where they “sleep” for the winter)
Arousal (5)
- Period when metabolic rate will rise
- Can occur if temps in burrow go too low
- Can occur spontaneously
- Some species have food caches and will feed during this time
- Use Brown Adipose Tissue (BAT) for arousal
Brown Adipose tissue (BAT) (4)
*Brown fat is highly vascular, well innervated, contains many mitochondria.
*Near blood vessels and vital organs.
*Often lost after infancy. Remains in hibernators through their entire life.
*Is burned to produce heat, not energy.
Small vs large hibernators (3)
Body size determines fuel storage & heating cost
Small hibernators: bats, ground squirrels
* Body temp dropped to near freezing.
* Long periods of dormancy, short periods of arousal
Large hibernators: bears
* Body temp dropped only slightly
* Shorter periods of dormancy, longer periods of arousal
Staying warm: moving lower (3)
On land : Go deep below frost line, where ground is above freezing
In water: move to deeper water
under snow: make tunnels and burrows
Staying warm: alternative life stage (3)
*Many invertebrates Overwinter in egg stage
* Often in thick casing to protect egg
* Mosquito eggs can sometimes lie dormant for several years
All the therms (4 and general status)
Endotherm: generates heat to maintain body temp.
Ectotherm: Rely on external sources of heat
Homeotherm: animal that maintains approximately constant body temp
Poikilotherms: animals that have variable body temperatures
Generally:
ectotherm = Poikilotherm e.g., most insects, fish, herps
Endotherm = Homeotherm e.g., most birds & mammals
Staying warm: how reduce heat loss (6)
- Get Big (bergman’s rule)
- Be more round (Allen’s rule)
- Insulate
- Lower conductive heat loss
- Restrict evaporative heat loss
Staying warm: Get big (bergman’s rule)
Bergmans rule: Animals of larger size are found in colder environments Within species (populations), and between species
size to volume ratio: Bigger you are = more volume to store heat and less surface area to lose it
Staying warm: Get round ( Allen’s rule)
Allen’s rule: A reduction of the Arctic fox’s ears, muzzle, legs, and tail allows it to conserve heat.
size to volume ratio: rounder you are = less surface area to lose heat
examples (dont need to list just to understand)
* Short appendages
* Blunt snout
* Short rounded ears
* Dense winter fur
* Furry feet
Staying warm: insulate (3)
*Insulation is increased by Structure of hair and increased density/thickness to better trap air
*insulation is decreased by Water (cannot trap air when compacted) and wind (destroys layering)
*Blubber isnt as good as fur but it works in the water!
Gloger’s rule (definition and 4 explanations)
*birds and mammals should be darker in humid and warm environments compared to colder and drier areas. there are 4 main explanations for this
Camouflage: Warmer/humid environments = richer soil and more vegetation = darker backgrounds
Photoprotection: Thought that darker pigmentation has protective functions against harmful UV rays (think human skin tones)
Pleiotropy: where a single gene affects multiple systems, or controls more than one phenotype (ie it’s a fluke not intended)
Protection against parasites: no info given
Staying warm: lower conductive heat loss (3)
Limit snow contact: birds have rough feet on the microscopic level so their entire foot is never on the ground at once. Caribou have fur feet to achieve the same thing
Limit energy lost through traversal: making trails, different foot loads etc.
Allow peripheral tissue to cool
Staying warm: reduce evaporative heat loss (3)
*evaporative heat loss: heat lost from water evaporating out of the body
*In humans on cold day, 20% energy is lost by breathing
*many arctic animals have specially adapted nasal conchae (nose holes) to reduce heat loss from breathing
Caribou Conchae (inhale 2 exhale 3)
Animal inhales
– Air passes over warm mucosa, saturated with water
– Mucosa are cooled & warm wet air goes to lungs
Animal exhales
– Air passing over cool mucosa is warm, wet from lungs
– Water condenses & mucosa are warmed
– Animal exhales cool “dry” air
