7: Light and Periodicity

light reaction occurs in ?

thylakoids of chloroplasts

dark reactions occur in….

stroma of chloroplasts

-occur independently of light

what is the light compensation point

level of light in which carbon uptake in photosynthesis=rate of carbon loss in cell respiration

what is the light saturation point ?

level of light in which maximum rate of photosynthesis occurs

Where in plants does photosynthesis occur?

chlorophyll of chloroplasts

What kind of plants use Calvin Cycle (C3 pathway)? What habitat are they in?

most temperate plants; all in Arctic

-temperate habitat

Leaf anatomy of C3 plants?

2 mesophyll cells

What kind of plants use Hatch-Slack Cycle (C4 pathway)? What habitat are they in?

-mostly grasses (like sugar cane)

-warm/tropical habitat

leaf anatomy of C4 plants?

Kranzs anatomy- bundle sheath cells w/ vascular bundle

What kind of plants use CAM pathway? What habitat are they in?

-succulents (open stomata at night)

-desert habitat

leaf anatomy of CAM plants?

large vacuoles

Rank the habitats in terms of their light penetration thru forest from least to greatest?

1) tropical rain forest

2) temperate deciduous forest

3) pine forests

Canopy leaves vs. midstory leaves

canopy leaves→smaller and thinner bc they already get a lot of sunlight at the top

midstory leaves→larger bc try to get more sunlight

sun-adapted plants? when do they reproduce?

-in open-disturbed areas

-higher rates of photosynthesis/ respiration & growth

-reproduce early

shade adapted plants? when do they reproduce?

-prefer shade (ground of forest)

-low rates of photosynthesis/respiration & growth

-reproduce late

entrainment

setting of a biological clock based on an environmental time setter (independent of temperature)

what are examples of environmental “time setters” for the biological clock

1) light

2) temperature (sometimes)

3) moisture

4) tide

Where is biological clock located?

mainly brain in multicellular organisms

Circadian rhythm? What is it usually set by?

cycle of activity in organisms that naturally exhibit a periodicity of about 24 hrs

(all organisms have except bacteria)

-set by rising and setting of sun

diurnal vs. nocturnal vs. crepuscular

diurnal→active in day
nocturnal→active at night

crepuscular→most active at dawn & dusk

What is cathemeral behavior?

active during either day or night

Circannual rhythm? Ex?

cycel of activity in organisms that naturally exhibit a periodicity of 12 months

ex// migration, hibernation

short-day plants vs. long-day plants

short day→ flower in late summer or fall (photoperiod is less than critical photoperiod)
long-day plants→flower in late spring or summer (photoperiod exceeds critical photoperiod)

day-neutral plants

flower in response to temperature and moisture not light

reproduction usually occurs during what season? Migration occurs during what season?

reproduction→spring bc optimum food availability

migration→after winter/dormancy

what are tides caused by?

gravitational pull of the mostly MOON & sun

how long is a tidal cycle?

24.8 hrs long, usually with 2 high tides & 2 low tides per day

Spring tides vs. neap tides

spring tides→greatest fluctuation is when earth, sun, and moon are in line
neap tides→least fluctuation is when earth, sun, and moon at right angles

example of extreme biological clocks

13 year and 17 year long cycles for cicadas