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Biology > topic 6 > Flashcards

topic 6 Flashcards

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1
Q

how are photosynthetic organisms the main producers of food and therefore biomass?

A
  • at the base of almost every food chain is a producer
  • these are plants or algae, which photosynthesise
  • this means they convert energy from the sun into glucose during photosynthesis producing biomass
  • it is this which feeds the rest of the food chain
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2
Q

what reaction is photosynthesis and what are it requirements, reactants and products?

A

Photosynthesis is an endothermic reaction as it requires light energy to react carbon dioxide and water to produce glucose and oxygen.

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3
Q

Explain the effect of temperature as a limiting factor on the rate of photosynthesis

A
  • if it gets too cold, the rate of photosynthesis will decrease.
  • plants cannot photosynthesise if it gets too hot.
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4
Q

Explain the effect of light intensity as a limiting factor on the rate of photosynthesis

A
  • Without enough light, a plant cannot photosynthesise very quickly
  • even if there is plenty of water and carbon dioxide and a suitable temperature.
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5
Q

Explain the effect of carbon dioxide concentration as a limiting factor on the rate of photosynthesis

A

As carbon dioxide concentrations increase, so too does the rate of photosynthesis until a certain point where the graph levels off. At lower carbon dioxide concentrations carbon dioxide is the limiting factor because an increase in carbon dioxide causes an increase in photosynthesis.

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6
Q

Explain the interactions of temperature, light intensity and carbon dioxide concentration in limiting the rate of photosynthesis

A
  • the rate of photosynthesis increases until other factors becoming limiting
  • if carbon dioxide concentration is increased, the rate increases further, and then another factor becomes limiting
  • the rate can be increased further if the temperature is increased
  • the rate increases again until another factor becomes limiting
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7
Q

Method of investigating the effect of light intensity on the rate of photosynthesis

A
  • can be investigated in water plants.
  • plants will release bubbles of oxygen – a product of photosynthesis – which can be counted.
  • lamp with an LED bulb is set up at different distances from the plant in a beaker of water
  • sodium hydrogencarbonate is added to supply carbon dioxide to the plant
  • the light intensity is proportional to distance – it will decrease as the distance away from the bulb increases
  • so light intensity for the investigation can be varied by changing the distance from the lamp to the plant
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8
Q

Why is a led bulb best when testing light intensity in plants?

A

an LED bulb is best as this will not raise the temperature of the water

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9
Q

method for investigating light intensity

A
  1. boiling tube w/ 45 cm³ of sodium hydrogencarbonate solution (1%). allow tube to stand to remove any air bubbles that may form.
  2. cut an 8cm piece of pondweed
  3. use forcepts to place the pondweed in boiling tube carefully. make sure not to damage the pondweed
  4. position boiling tube so pondweed is 10cm away from the light source. allow to stand for five minutes. count number of bubbles emerging from cut end of stems in 1 min. repeat the count five times and record results.
  5. calculate the average number of bubbles produced per minute. repeat the experiment at different distances away from the light source.
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10
Q

Explain how the rate of photosynthesis is directly proportional to light intensity and inversely proportional to the distance from a light source

A
  • light provides the energy needed for photosynthesis. Increasing the light intensity increases the rate of photosynthesis
  • as the distance increases, light intensity decreases.
  • this is because as the distance away from a light source increases, photons of light become spread over a wider area.
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11
Q

inverse square law equation

A

the light intensity is inversely proportional to the square of the distance and directly proportional to the rate of photosynthesis. so the light intensity/ rate of photosynthesis=

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12
Q

Explain how the structure of the root hair cells is adapted to absorb water and mineral ions

A
  • have large surface areas to increase the rate of absorption
  • lots of mitochondria which release energy from glucose during respiration in order to provide the energy needed for active transport
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13
Q

Explain how the structures of the xylem are adapted to their function in the plant,

A
  • they lose their end walls so the xylem forms a continuous, hollow tube
  • they become strengthened by a substance called lignin
  • lignin gives strength and support to the plant.
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14
Q

what is the xylem and what is it made up of?

A
  • the xylem is a tissue which transports water and minerals from the roots up the plant stem and into the leaves.
  • xylem consists of dead cells.
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15
Q

does transport in the xylem require energy, explain?

A

no as transport in the xylem is a physical process

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16
Q

xylem diagram showing how it transfers water to the rest of the plant

A
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17
Q

Explain how the sieve tubes of the phloem are adapted to their function in the plant

A
  • are specialised for transport they have no nuclei
  • each sieve tube has a perforated end so its cytoplasm connects each cell to the next
  • sucrose and amino acids are translocated within the living cytoplasm of the sieve tubes
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18
Q

Explain how the companion cells of the phloem are adapted to their function in the plant

A
  • transport of substances in the phloem requires energy
  • one or more companion cells attached to each sieve tube provide this energy
  • a sieve tube is completely dependent on its companion cells
19
Q

what does the phloem do and what is it made up of?

A
  • moves food substances that the plant has produced by photosynthesis to where they are needed such as:
  • growing parts of the plant for immediate use
  • storage organs such as bulbs and tubers
  • developing seeds
20
Q

Explain how water and mineral ions are transported through the plant by transpiration, including the structure and function of the stomata

A
  • transpiration is the evaporation of water at the surfaces of the spongy mesophyll cells in leaves, followed by loss of water vapour through the stomata
  • transpiration produces a tension on the water in the xylem vessels by the leaves
  • water molecules are cohesive so water is pulled up through the plant
21
Q

Describe how sucrose is transported around the plant by translocation

A

The sucrose is transported around the plant in phloem vessels. It needs to be able to reach all cells in the plant so that the sucrose can be converted back into glucose for respiration. The movement of sucrose and other substances like amino acids around a plant is called translocation

22
Q

Explain how the structure of a leaf is adapted for photosynthesis and gas exchange

A
  • large surface area: maximum light absorption
  • chlorophyll containing chloroplast
  • thin structure: short distance for carbon dioxide to diffuse into leaf cells
  • stomata: allow carbon dioxide to diffuse into the leaf and oxygen to diffuse out.
23
Q

Explain the effect of environmental factors on the rate of water uptake by a plant, to include light intensity, air movement and temperature

A
24
Q

how do you calculate the rate of transpiration?

A

measuring the distance travelled by an air bubble in a capillary tube over a given time.

25
Q

Explain how plants are adapted to survive in extreme environments including the effect of leaf size and shape, the cuticle and stomata

A
  • stems: store water.
  • widespread/very deep root systems: collect water from a large area/ very deep underground.
  • spines (modified leaves): minimise the surface area reducing water loss and protect the cacti from animals
  • very thick, waxy cuticle: reduce water loss by evaporation.
  • reduced number of stomata: reduce water loss by transpiration.
26
Q

Explain how plant hormones control and coordinate plant growth and development, including the role of auxins in phototropisms and gravitropisms

A
27
Q

positive tropisms

A

the plant grows towards the stimulus

28
Q

negative tropisms

A

the plant grows away from the stimulus

29
Q

phototropism

A

is the growth of plant shoots towards the light

30
Q

positive phototropism

A

the stem grows towards the light

31
Q

negative phototropism

A

the root grows away from the light.

32
Q

where is positive phototropism found?

A

the stem

33
Q

where is negative phototropism found?

A

in the root

34
Q

how do auxins affect phototropism in the stem?

A
  • the shaded side of a stem contains more auxin
  • the auxins cause the cells to elongate on the shaded side so it grows more (it doesn’t bend to the light)
  • this unequal growth causes the growth of the stem towards the light
35
Q

how do auxins affect phototropism in the root?

A
  • the shaded side contains more auxin
  • grows less
  • causes the root to bend away from the light.
36
Q

negative gravitropism

A

when the stem grows against the force of gravity

37
Q

positive gravitropism

A

when a root grows in the direction of the force of gravity

38
Q

how do auxins affect gravitropism in the root?

A
  • in a root placed horizontally, the bottom side contains more auxin and grows less
  • causing the root to grow in the direction of the force of gravity
39
Q

how do auxins affect gravitropism in the stem?

A
  • when a stem is placed horizontally, the bottom side contains more auxin and grows more
  • causing the stem to grow upwards against the force of gravity.
40
Q

diagram of the four stages of positive gravitropism

A
41
Q

how can auxins be used in weedkillers?

A
  • selective weed killers kill some plants, but not others
  • the selective weed killer contains a growth hormone that causes the weeds to grow too quickly and die
  • because the weeds have broader leaves, the weed killer is absorbed in larger quantities by the weeds than it is by the grass
  • selective weed killers can reduce biodiversity within treated areas due to specific plants being killed.
42
Q

how are gibberellins used in germination, fruit and flower formation and the production of seedless fruit?

A
  • seed dormancy must be broken for seeds to germinate, and this can be done by using gibberellins
  • promote flowering: can mean more financially profitable flowers to sell due to the increased speed of flower growth
  • more attractive flowers and larger specimens are also produced
  • flowering also has an impact on the rate of fruit growth
  • gibberellins are used in the production of seedless fruit such as seedless grapes, which are normally sprayed with gibberellin to increase the size of each grape.
43
Q

how is ethene used to ripen fruit?

A
  • ethene is a hydrocarbon gas and it speeds up ripening in bananas and other fruit
  • ethene is used routinely within the food industry to provide controlled ripening during storage and transport or when fruit is displayed in shops, in sealed packages

Biology (15 decks)

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