Struggle for Existence pt. 5 Flashcards
organisms are…
bags of juices in which chemical rxns occur and libraries of info (DNA)
Abiotic factors can be divided into
conditions
- cannot be depleted (temp, pH)
resources
- water, space, nutrients
Limiting factors
determine whether a species can or cannot persist in an area
biggest two for land organisms are temp and moisture.
transect
sample that cuts across ecological variation
Factors like temp, pH, salinity, organic content of soil, altitude can be treated as….
a gradient
Range of tolerance
the portion of an ecological gradient an organism is restricted to
types of soil
hydric - wet, waterlogged
xeric - dry
mesic - mix of the two
Why are temp and water so important?
Temperature affects reaction rates (proteins denature at too high, reactions will not proceed if its too cold). Water determines internal chemistry. Water will change the concentration of reactants and also affect osmotic balance
How does equilibrium affect organisms?
objects will reach same temp as their surroundings, and in dry environments organisms will lose water and become saltier.
Why is equilibrium asymmetrical?
Environments are intrinsically implacable and organisms are intrinsically vulnerable (rabbit in the arctic becomes super cold but the heat lost by the rabbit does not affect the arctic at all)
thermoregulation
maintaining temp
osmoregulation
maintaining saltiness
thermoconformers
organisms whose bodies closely track ambient temperatures
Which is a better median for heat exchange: water or air?
Water because it requires more energy than any other material commonly found in ecosystems to change its temperature.
radiative heat transfer
does not involve heat transfer by molecules crashing into each other. Concept that you can be heated by a net positive difference in the IR energy being radiated from towards you than from you. Fire on a cold night doesn’t warm your back because it’s not warming the environment!!
linear dimensions
length, width, height
How do otters and penguins stay warm in water?
Water is really effective at conducting heat out of animals. Otters and penguins keep fur/feathers temporarily waterproof by oil secretions and preening. Mammals that are continually immersed need blubber (their outer skin is equilibrated with water but inside is warm)
How do birds stay so warm?
Puff up contour feathers, creates empty space where down feathers spring up blocking convective air flow that brings hot air away from skin.
countercurrent circulation
direct contact between arteries and veins
Most homeotherms can survive extreme cold if… and heat if…
they have sufficient food
they have sufficient water
kangaroo rats
Survive without every drinking liquid water, instead use metabolic water produced by oxidizing dry food they eat. They have highly efficient kidneys that secrete really concentrated urine (minimal water loss). Hygroscopic seeds absorb moisture exhaled.
Catch-22 of leaves
need to be big enough to catch photons and facilitate gas exchange but the larger the leaf the more prone to overheating (leaves are thin thus little if any thermal inertia)
- they use evaporative cooling (water from roots goes to leaves)
C3 plants
- atmospheric CO2 is fixed in a three carbon molecule (enzyme that captures carbon is not efficient and sometimes captures oxygen instead)
- not water efficient
- stomata must be open when sunlight hits to facilitate gas exchange
- wheat and rice
C4 plants
- tropical grasses (maize, sugar cane)
- 4 carbon intermediate
- stomata must be open when sunlight hits to facilitate gas exchange
CAM
Crassulacean Acid Metabolism
- extreme water conservation in succulents and epiphytes
- thick leaves that provide inertia
- keep stomata closed during sunny periods and open at night to get CO2
- store CO2 in vacuoles as organic acid intermediate until the next day
- when photons are available, acid continues on pathway
- evolved independently in many species
Why do leaves have lobes and points and bumps
to turn laminar airflow into turbulent air flow to facilitate gas exchange (break up boundary surface layer thats stagnant air)
differing root systems
- deep root systems use water stored deep in the soil (soil is external store)
- extensive, shallow root systems like the saguaro cactus occur in environments where the soil is dry except right after it rains. The root system immediately soaks up as much water as possible as soon as it falls (internal store year round)
How do other desert plants survive (not cacti)?
They grow, flower, and seed right after a rain. They only grow in periods where there is non-desertlike conditions.
microphylly
tiny leaves
Sclerophylly (advantages in multiple habitats)
small, thick, tough, leaves that persist year round. smelly. (rosemary, pine needles)
BOREAL
- evergreens dont have to regrow leaves and can photosynthesize as soon as its warm enough
- good at shedding snow
CHAPARRAL
- small leaves less likely to overheat also need less water for evaporative cooling
SANDY SOIL
- soil is bad at retaining water, this can have desert like conditions
- dont have to regrow leaves in nutrient deficient conditions
BOGS
- favoured indirectly in acidic watery conditions that pickle dead vegetation (stopping nutrient release) because being evergreen increases nutrient retention
Angiosperm
Flowering plants, seeds enclosed within an ovary (usually fruit)
Gymnosperm
Conifers
- seed bearing, vascular plants
- no flowers or fruits
- have unenclosed (naked) seeds on the surface of scales or leaves
