2a. The Phusical Enviornment

Question 1

Light

Answer 1

Too little light = gain from photosynthesis does not cover energy requirements = for example the forest floor

Too much = excess light can not be absorbed as energy and photo damage can occur.

Question 2

Adaptation to light levels

Answer 2

May be permanent (morphology of plants) or dynamic (chloroplast moving in leaf cell)

Question 3

Life history adaptations

Answer 3

Shade tolerant plants almost always perennial, as an annual life cycle requires high energy

Question 4

Germination

Answer 4

Lightbkevels drive germination success. Some require light, some darkness => plants at the bottom of the forest will develop and reproduce before tree grow leaves and block the light and temperature correlated

Question 5

Poikilotherms

Answer 5

Pants => generally assume the temperature of their environment

Question 6

Hemeotherms

Answer 6

Maintain steady body temperature

Extreme body temperatures can cause metabolic difficulties and physical damage.

E.g. Forest damage = burnt tips

Question 7

Cardinal points of temperature tolerance

Answer 7

1. Cold death
2. Cold rigidity
3. Range pf active life
4. Health rigidity
5. Heat death

Question 8

Frost avoidance

Answer 8

Annual life cycles, over wintering as seeds - Deciduous trees lose frost sensitive leaves during winter

Question 9

Frost tolerance

Answer 9

Supercooling (reduce freezing threshold below 0 degrees), loss of water to extra cellular areas to avoid cell damage.

Thermal insulation to avoid short term freeze events

Question 10

Heat avoidance

Answer 10

Division of leaves, hairy leaves reflect radiation, position of leaves (similar to light adaptation), transpiration cooling n

Question 11

Heat tollerance

Answer 11

Hardening (chemical processes in cell membrane to increase resistance to heat stress

Question 12

Psychrophiles

Answer 12

Adapted to cold.

Question 13

Themophiles

Answer 13

Require high temperature

Question 14

Extremephiles

Answer 14

Slow ice algae

Question 15

Mesophiles

Answer 15

Most plants prefer medium temperatures

Question 16

Pyrophytes

Answer 16

Fire dependent for seed opening

Question 17

Temperature

Answer 17

Not all life cycles require the same temperature. Some plants can regulate temperature => sunflowers follow the sun. Distribution of plants depend on temperature. Each plant needs to have perfect conditions to reproduce

Question 18

Water and animals

Answer 18

Mammals can withstand water loss of about 10% of their body water

Water can be lost through skin, respiration, excrement and other secretions.

The level of water lost amongst animals is dependent on climate conditions

Majority of terrestrial animals are dependent on water sources such as rivers, while some animals take up water through their food

Question 19

Water and plants - transpiration is controlled by:

Answer 19

Waxy cuticle
Stomata opening
Lenticles ( waxy small leaf in drier climates)

Question 20

Water stress

Answer 20

Water loss relatively high compared to absorption through roots. Reduces rates of photosynthesis

I.e. = closing of stomata = lack of gas exchange
Higher vulnerability at seedling stage

Limited water availability is often accompanied with high temperatures and high light levels.

Cells cannot desiccate or rehydrate or take up water from the air.

Plants could only expand into terrestrial habitats with the division of labour between organs

Leaf surface is impermeable to h2o and co2

Algae, mosses and lichens cannot have the division of labour and so cannot desiccate but do the other two

Question 21

Adaptations to water stress: desiccation avoidance

Answer 21

Survive as dormant seeds, shedding leaves, dormant plants below ground, storage of water in the stem (cacti), reduce transpiration, open stomata at night, salt exclusion,excretion mechanisms

Question 22

Salt

Answer 22

Atmospheric gradient changes with salinity. Most marine organisms cannot live in fresh water and vice versa.

Salmon for example has adapted to survive in both fresh and salt water

Question 23

Soils - nutrients

Answer 23

Bounded to soil particles and exchanged with the plant through cation exchange. pH value regulates nutrient availability (best in neutral pH)

Question 24

Water

Answer 24

Look at slide

Capillary water is mainly what plants can use

Question 25

Field capacity

Answer 25

How much water the soil can hold. Usually less than 3 days after rainfall

Question 26

Permanent wilting point

Answer 26

Water content of soil beyond which most plants are no longer able to take up water

Question 27

Plant available water

Answer 27

Field capacity - wilting point