Lecture 4 – Organisms Vs. Env Variability

Question 1

Individual Responses: Developmental (years)

Answer 1

Irreversible

Individual alters its development to produce a phenotype most suitable to a persistent slow change in environmental conditions

ex: long vs short winged striders
temp low= most likely short wing since less likely to dry up

Question 2

Individual Responses: acclamatory

Answer 2

day-weeks and reversible

fur gets thick, hibernation

Question 3

freeze avoidance strategy (acclamatory response)

Answer 3

in insects as temperatures start to decrease in fall
 convert glycogen reserves → alcohol

because alcohol= higher freezing point. so need more alcohol in body

Question 4

Individual Responses: regulatory

Answer 4

min-hrs
reversible
ex: shivering, leaf curling (to lose less water when temp is high)

Question 5

Photosynthesis (what is it and where it takes place)

Answer 5

process where energy from the sun is used to transform CO2 into
carbohydrates (simple sugars) and O2

mesophyll cells

Question 6

respiration (what is it and where it takes place)

Answer 6

carbohydrates are broken
down to generate energy (ATP), releasing CO2

in the mitochondria of cells (plant & animal)

Question 7

photosyn and resp difference

Answer 7

Plants both use and produce CO2 and the difference in the rates of these two processes
is:
Net Photosynthesis = Photosynthesis – Respiration
(= carbon uptake – carbon loss)

Question 8

Chlorophyll

Answer 8

(light absorbing pigment) traps light energy → synthesizes ATP →
this energy drives CO2 → O2 + sugars
 this chemical reaction is dependent on enzyme called rubisco

Question 9

process of co2 and water in leaf

Answer 9

CO2 diffuses into the leaf through openings in the surface of the leaf, called stomata

As CO2 diffuses into the leaf, water diffuses out of the leaf (= transpiration aka plants lose water vapor through stomata)

Because of diffusion note: CO2 enters: atmosphere&raquo_space; leaf
Water leaves: atmosphere &laquo_space;leaf

water lost must be replaced with water taken by roots from the soil

Question 10

Plants must acquire essential resources:

Answer 10

light, CO2, water, nutrients

Question 11

leaf tissue, stem tissue, and root tissue roles and which role is most important in hot environment

Answer 11

Leaf tissue - photosynthesis (uptake of CO2)

Stem tissue - structural support (gain access to light)

Root tissue - water and nutrient uptake from the soil

root tissue most important since no problem with sun and photosynthesis

Question 12

Plants vs. Water Loss: Moderate time scales (wet vs dry)

Answer 12

Wet conditions (ideal) → ↑ leaf tissue & ↓ root and shoot

No increase in other tissues (i.e. shoot, root) because this
increases the rate of respiration (CO2 loss)

Dry conditions → ↑ root tissue & ↓ leaf and shoot

this is an example of Individual → Acclimatory or Developmental Response

Question 13

Long time scales (evolution): dry environments

Answer 13

dessert plants actually adapt

modified form of photosyn= inc water use efficiency

ex c4 and CAM plants

additional step in the conversion of CO2 into sugars → higher
maximum rate of photosynthesis

higher rate of photosynthesis requires stomata to be open less
time → less water is lost

Question 14

leaf morphology adaptations to dry conditions:

Answer 14

smaller and thicker leaves (water storage)
 smaller stomata
 cover leaves in wax, resin, little hairs (e.g. cactus

Question 15

Shade-tolerant vs shade-intolerant

Answer 15

lower production of rubisco in leaf tissue (do not expend energy
producing high amounts of rubisco)

consequence: even if now put in the sun, it will still grow similarly (due to low rubisco, decreases photosynthetic rate)

shade intolerant: high growth rates in sunlight, low in shade

Question 16

Shade-tolerant compensated by:

Answer 16

higher production of chlorophyll (light absorbing pigment)

higher leaf surface area

higher growth of leaves than roots
(increase the photosynthetic surface area to offset the decrease in
photosynthetic rate- due to lower amount of rubisco)

Question 17

conformers vs regulator

Answer 17

conformers: allow internal conditions to follow external changes

Regulators: maintain constant internal conditions

Question 18

Homeostasis

Answer 18

ability to maintain constant internal conditions in a varying environment

Always involves a negative feedback system

1. mechanism that senses the internal condition
2. means of comparing the actual with the desired
   internal condition
3. apparatus that alters the internal condition in
   preferred direction

Question 19

endotherm vs ectotherm

Answer 19

1. maintain body temp through internal processes (metabolism)
2. rely on external sources (sun, warm surfaces)

snakes eat less than mammal of same size since mammals use energy to constantly warm themselves

Question 20

Poikilothermy vs Homeothermy

Answer 20

1. cannot maintain constant body temperature (body temp varies)
    Most amphibians, fish and insects
    Only active in a narrow range of temperatures

maintain constant body temperature
 most birds and mammals ~ 36 – 410C (temp. at which biochemical processes within cells
are efficient)
 Highly active under varying temperatures

Question 21

false of Poikilothermy and Homeothermy

Answer 21

not all t ectotherms are poikilotherms (i.e. body temps vary)
and not all t endotherms are homeotherms (i.e. constant temp)

ex: naked mole rat is endotherm but it is poikilo

ex: deep sea fish are ectotherm but since temp is constant it is homeotherm

Question 22

Limitations of Ectotherms

Answer 22

Ectotherms must behaviourally generate heat
 Ectotherms generate heat when active

Question 23

Limitations of Endotherms

Answer 23

Endotherm’s ability to maintain constant body temperature is limited under low
temperatures
 Short-term – by physiological capacity to generate heat
 Long-term – by ability to gather food (or energy) to satisfy requirements for
metabolic heat production
 animals usually starve to death before they die of direct causes of cold
temperatures

Question 24

3 ways endotherms conserve energy

Answer 24

1. Lower the regulated temperature of a portion of their body
2. Lower the regulated temperature at certain times of the day

Torpor = temporary reduction in metabolic activity and lowered body temperature (it’s used to save energy)
 Hibernation = extended reduction… (e.g. over the winter)
Eg. Hummingbirds
Inactive at low temps:

3. become larger!
   Large Organisms
    Low SA/V
    Require more heat but it is retained easier

Question 25

Counter-current heat exchange (in birds)

Answer 25

legs and feet much cooler, reduces the temp difference between their feet and environment warm blood goes down, cold blood goes up (cold blood to body= less heat loss0, heat flows from warm to cold. this keeps warm blood in body, and cold blood going to feet

Question 26

The surface area to volume ratio of an organism is an example of an:

Answer 26

Allometric Relationship a relative increase in a physical or physiological property of an organism in relation to its body size

Question 27

: What happens when temperatures drop slowly in plants vs temperatures drop rapidly in plants?

Answer 27

ice forms in cell walls, causing dehydration, which is reversible when temperatures rise. Ice crystals form inside cells without dehydration, which can puncture membranes and cause cells to leak during thawing.

Question 28

What is supercooling in plants? and its downside

Answer 28

A genetically controlled trait where plants produce antifreeze compounds (like sugars) to lower the temperature at which freezing occurs. requires a lot of energy and nutrients.

Question 29

Which plant types use supercooling?

Answer 29

Needle-leaf evergreen species.

Question 30

How do deciduous species avoid the cost of supercooling?

Answer 30

By shedding their leaves before winter.

Question 31

What is pubescence in plant leaves?

Answer 31

Small, light-coloured hairs that reflect solar radiation and create an insulative boundary layer. Reduces heat from solar radiation and insulates the leaf.

Question 32

What unique temperature strategy does skunk cabbage use?

Answer 32

It metabolically generates heat in spring to thaw snow and attract pollinators. aka endotherm

Question 33

Moisture adaptations can be: short moderate and long time scales. give examples

Answer 33

Moisture adaptations can be: short (e.g. stomatal regulation), moderate (e.g. leaf orientation), and long (e.g. deep root systems) time scales.