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Biogeography and Ecology > Physical controls on the distribution of organisms > Flashcards

Physical controls on the distribution of organisms Flashcards

1
Q

Light

A

variation in light intensity is a key control in distribution of plant species within an ecosystem

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2
Q

Heliophytes

A
  • sun plants
  • plants which grow best in full sunlight
  • shade intolerant
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3
Q

Sciophytes

A
  • shade plants
  • plants which grow best in shade
  • shade tolerant
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4
Q

C4 photosynthesis

A
  • more efficient use of CO2
  • no photorespiration
  • chloroplasts concentrated within bundle sheath cells
  • but expensive!
  • tropical grasses
  • good water-use efficiency
  • efficient at high temp and low CO2
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5
Q

Transpiration

A

evaporation from the leaf

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6
Q

Evapotranspiration

A

evaporation from leaf plus soil

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7
Q

C3 plants

A

inefficient at high temp and low CO2

  • increased photorespiration
  • poor water-use efficiency
  • physiological drought
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8
Q

CAM photosynthesis

A

Crassulacean Acid Metabolism

  • carbon fixation pathway that evolved in some plants as an adaptation to arid conditions.
  • closes leaves at night to reduce evapotranspiration and open at night to collect CO2
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9
Q

Photoinhibition

A

shrinking of chloroplasts, loss of chlorophyll, loss of CO2 due to ‘photo-oxidation’

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10
Q

Photo-respiration

A
  • as a result from photo-oxidation
  • CO2 released but not utilisable by plant
  • only occurs in C3 plants
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11
Q

Rate of photorespiration

A

positively correlated with light intensity and temperature

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12
Q

Sun leaves

A
  • thicker, more cell layers
  • thicker cuticle
  • leaves more dissected
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13
Q

Shade leaves

A
  • thinner, fewer cell layers
  • thinner cuticle
  • leaves less dissected§
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14
Q

Perennials

A

live for more than 1 year

shade tolerant plants

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15
Q

annuals

A

not enough light in shady conditions to support them

must germinate, grow, flower and set seed in 1 year

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16
Q

phenology

A

The timing of changes in growth of plant e.g.
- flowering in spring
- Shedding leaves in Autumn
Triggered by changes in duration of daylight

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17
Q

Photoperiodism

A

relationship between phenology and light

18
Q

Key points about plants and light

A
  • too little light is bad, but too much light is also bad

- plants have evolved a range strategies to grow under low and high light intensities

19
Q

Temperature

A

geographic distribution of plants strongly linked to temperature
- metabolic and physical damage by extreme heat and cold

20
Q

Chilling stress

A
  • damage to cold temp above 0 degrees
21
Q

Chilling sensitive

A

Damage by temp <10 degrees

22
Q

Chilling resistant

A

survive < 10 degrees but damaged by ice formation

23
Q

Frost resistant

A

survive to -15 degrees

24
Q

Frost tolerant

A

Survive to -40 degrees

25
Q

Cold tolerant

A

survive below -40 degrees

26
Q

Damage caused by chilling stress

A
  • above 0 degrees, but may be 15-20 for some tropical plant species
  • infertile pollen or seeds
  • low growth rate
  • leaf discolouration
  • stem/leaf dieback
  • lesions on fruit
  • young plants affected more than older/larger plants
27
Q

Frost hardening

A
  • frost resistance only possible if cooling gradual

- period of physiological preparation required

28
Q

Poikilotherms

A
  • cold blooded animals
  • Ectotherms
  • fish, reptiles, amphibians, insects
29
Q

Homeotherms

A
  • warm blooded animals
  • Endotherms
  • birds, mammals
  • metabolic generation fo heat
30
Q

Ectotherms

A
  • body temp = ambient temp of environment
31
Q

Endotherms

A
  • above ambient temp of environment
32
Q

Temperature Range

A
  • when active, body temp must be in a narrow range

- most cannot survive close to freezing or near 40 degrees

33
Q

Eurythermic

A

species that can tolerate a broad temperature range

34
Q

Stenothermic

A

species with a restricted temperature range

35
Q

Why does metabolic rate decline rapidly above 40°C?

A
  • Enzyme activity slows
  • Proteins break down
  • Cell membranes destroyed
  • Rates of oxygen intake no longer match respiratory needs
36
Q

Allens rule

A

the shorter an animals erctremitites are relative to body mass, the lower the rate of heat loss

37
Q

Moisture and plants

A

Xerophystes
mesophytes
hydrophytes

38
Q

Desert annuals

A
  • 8 day life cycle

- very high rates of photosynthesis

39
Q

Tropical Deciduous trees

A
  • drop leaves in dry season
  • store water in trunk
  • photosynthetic bark
40
Q

Conclusion

A
  • form related to function
  • different strategies (avoidance versus adaptation)
  • interaction of physical factors

Biogeography and Ecology (13 decks)

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