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biology > Topic 6 > Flashcards

Topic 6 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Give examples of photosynthetic organisms

A

green plants and algae

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2
Q

How are these photosynthetic organisms the main producers of food?

A
  1. They use energy from the sun to make glucose
  2. some of the glucose is used to make larger, complex molecules that plants/algae need to grow. (these makes up biomass)
  3. energy stored in biomass works its way through food chains as animals eat them and each other
    So photosynthetic organisms are the main producers of food fr nearly all life on earth
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3
Q

Is photosynthesis an endothermic or exothermic reaction?

A

An endothermic reaction (energy is taken in)

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4
Q

What is the symbol and word equation for photosynthesis?

A

Carbon dioxide + water (arrow with light and chlorophyll) glucose + oxygen

6CO2 + 6H20 (arrow with light above and chlorophyll below) C6H1206 + 602

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5
Q

What three things are limiting factors on the rate of photosynthesis?

A
  1. Temperature
  2. light intensity
  3. Conc of CO2
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6
Q

Describe how you could investigate the effect of light intensity on the rate of photosynthesis?

A
  1. set up apparatus. gas syringe should be empty at start and sodium hydrogencarbonate could be added to provide plant with CO2
  2. place source of light at specific distance from PW
  3. allow PW to photosynthesis for set amount of time
  4. O2 released will collect in the syringe (volume)
  5. repeated with light source at different distances
  6. rate of oxygen produced - volume / time
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7
Q

What should we control during the core practical?

A
  • temperature (by putting flask into a water bath)

- and CO2 conc (adding set amount of sodium hydrogencarbonate to set amount of water)

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8
Q

what is rate of reaction

A

the rate at which reactant is used up or the rate at which the product is formed

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9
Q

how does CO2 concentration affect the rate of photosynthesis

A
  • CO2 is one of the raw materials needed for photosynthesis
  • increasing CO2 concentration increases rate of photosynthesis to a point
  • on a graph, the line flattens out, showing that CO2 is no longer a limiting factor
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10
Q

how does light intensity affect the rate of photosynthesis?

A
  • without enough sunlight, a plant cant react quickly no matter how much CO2 there is
  • this is because light transfers the energy needed for photosynthesis
  • increasing light intensity boosts the rate of photosynthesis
  • eventually the line would flatten out on a graph, indicating temp or CO2 level is the limiting factor
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11
Q

how does temperature affect the rate of photosynthesis

A
  • if it gets too hot or cold, the rate of photosynthesis will be low
  • but it increases as you reach the middle
  • this is because the enzymes in a plant that carry out photosynthesis have an optimum temperature in which that can react the quickest
  • temperatures too high denatures them so they dont react as quickly
  • and temps too low cause the enzymes to work more slowly
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12
Q

What is the inverse square law?

A

the law saying that the light intensity is inversely proportional to the square of the distance form the light source

light intensity = 1/distance squared

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13
Q

why is the rate of photosynthesis inversely proportional to the distance of the light source?

A

Because the the more the distance of the light source increases, the more the rate of photosynthesis decreases

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14
Q

How do root hair cells allow plants to absorb water and minerals?

A

They give the plant a large surface area for absorbing water (through osmosis) and minerals (through active transport as the conc of minerals is higher in the root hair cells than in the soil)

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15
Q

What is a phloem tube made up of?

A

columns of elongated living cells with small pores in the end walls to allow stuff to flow through

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16
Q

what is the function of the phloem tube

A

to transport food substances (mainly sucrose) made in the leaves to the rest of the plant for immediate use or for storage

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17
Q

What is translocation?

A

A process in phloem tubes that transports sucrose made in the leaves to the rest of the plant for immediate use or for storage. The process requires energy from respiration and the transport goes in both directions

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18
Q

What are xylem tubes made out of?

A
  • They are made out of dead cells joined end to end with no end walls between them and a hole down in the middle.
  • They’re strengthened with a material called lignin
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19
Q

What is the main function of xylem tubes?

A

They carry water and mineral ions from the roots to the stem and leaves

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20
Q

What is the transpiration stream?

A
  • Transpiration is the loss of water from a plant

- The transpiration stream is the movement of water from the roots, through the xylem and out of the leaves

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21
Q

Describe transpiration (process)

A

1, This is caused by evaporation and diffusion of water from plants surface( mostly happens at leaves)
2. This creates a shortage of water in leaf, and so more water is drawn up from rest of plant through xylem vessels to replace it
3 This means more water is drawn up from the roots, and so theres a constant transpiration stream of water through plant
4. The transpiration stream also carries along mineral ions that are dissolved in the water along with it

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22
Q

What are stomata?

A

Tiny pores found on the lower surface of leaves

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23
Q

How do stomata relate to gases and transpiration?

A

They allow CO2 and oxygen to diffuse directly in and out of a leaf. They also allow water vapour to escape during transpiration as the conc of water vapour is higher inside the cell so water escapes through the stomata

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24
Q

What are guard cells?

A
  • These are cells that surround the stomata and change shape to control the size of the pore.
  • When the guard cells are turgid (swollen with water), the stomata are open and when the guard cells are flaccid (low on water), the stomata are closed
25
Q

What three factors affect transpiration rate?

A
  1. Light intensity
  2. Temperature
  3. Air flow
26
Q

How does light intensity affect transpiration rate?

A

The brighter the light, the greater the transpiration rate as stomata are closed when its darker (they dont need to be open in the dark as photosynthesis only happens in the light so they can let CO2 in)

27
Q

How does temperature affect transpiration rate?

A
  • The warmer it is, the faster transpiration happens.

- When its warm, the water particles have more energy to evaporate and diffuse out of the stomata

28
Q

How does air flow affect transpiration rate?

A
  • if there is good air flow, rate of transpiration increases
  • because the water is swept away
  • which maintains a low concentration of water particles in the air outside the leaf
  • so diffusion from the leaves happens quickly, from an area of high concentration to an area of low concentration
29
Q

How can you estimate transpiration rate?

A
  • Using a potometer. measure the water uptake of a plant and use the equation. speed = distance / time.
  • You can use a potometer to estimate how light intensity, temperature or air flow affect transpiration rate by only changing the variable and controlling the rest
30
Q

what is water uptake by the plant directly related to?

A
  • water loss from the leaves

- as the xylem tube is a continuously flowing source of water

31
Q

How are leaves adapted for photosynthesis?

A

They are broad, so that there is a large surface area exposed to light. This is needed for photosynthesis

32
Q

How is the palisade layer adapted to photosynthesis?

A

Has lots of chloroplasts so they are near the top of the leaf, where they can get the most light

33
Q

How is the upper epidermis adapted for photosynthesis?

A

it is transparent so that light can pass through it to the palisade layer

34
Q

How are the xylem and phloem adapted for photosynthesis?

A

They form a network of vascular bundles, which provide the leaf with water for photosynthesis and takes away the glucose produced.
-They also help support the structure

35
Q

How are the epidermal tissues adapted for reducing water loss by evaporation?

A

They are covered with a waxy cuticle, which helps reduce water loss by evaporation

36
Q

How are the tissues of leaves adapted for efficient gas exchange?

A
  • the lower epidermis has lots of stomata, which lets CO2 diffuse into the leaf.
  • the spongy mesophyll tissue contains lots of air spaces which increases the rate of diffusion of gases into and out of the leaf cells
37
Q

How do small leaves or spines help plants like cacti to adapt in extreme conditions?

A

They reduces surface area for water loss by evaporation. spines stop animals eating plants to get water

38
Q

How do curled leaves or hairs help plants like cacti to adapt in extreme conditions?

A
  • They reduce air flow close to the leaf, trapping water vapour near the surface and reducing diffusion from the leaf to the air.
  • Spines also reduce air flow near the surface of the plant and so do a similar job
39
Q

How do thick waxy cuticles help plants like cacti adapt to extreme conditions?

A

They reduce water loss by evaporation

40
Q

How do thick, fleshy stems help plants like cacti adapt to extreme conditions?

A

They store water

41
Q

How do fewer stomata/stomata that only open at night help plants like cacti adapt to extreme conditions?

A

They reduce water loss by evaporation

42
Q

How do stomata sunken in pits help plants like cacti adapt to extreme conditions?

A
  • This makes the stomata lower than the surface of the leaf, which reduces air flow close to the stomata.
  • This reduces water loss in the same way as curled leaves or hairs
43
Q

What are auxins?

A
  • These are plant hormones that control the growth at the tips of shoots and roots
  • They are produced in the tips
  • They diffuse backwards to stimulate the cell elongation process in the cells just behind the tips
44
Q

What do auxins promote and inhibit?

A

They promote the growth in the shoot, but actually inhibit growth in the root.

45
Q

How are shoots positively phototrophic?

A
  1. When a shoot tip is exposed to light, it accumulates more auxins on the side thats in the shade than the side thats in the light
  2. This makes the cell grow faster on the shaded side and bend towards the light. they can absorb more light for photosynthesis
46
Q

What would shoots growing completely in the dark look like?

A
  • They would be tall and spindly as the auxins helps them to elongate quickly on all sides.
  • A taller shoot has a better chance of finding light
47
Q

How are shoots negatively gravitrophic? (grow away from gravoty)

A
  1. When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side
  2. This causes the lower side to grow faster, bending the shoot upwards
48
Q

How are roots positively gravitrophic? (grows towards gravity)

A
  1. A root growing sideways will have more auxins on its lower side
  2. In a root, the extra auxin inhibits growth. This means the cells on top elongate faster, and the root bends downwards
49
Q

How are roots negatively phototrophic?

A

1) If a root starts being exposed to some light, more auxin accumulates on the more shaded side
2) The auxin inhibits cell elongation on the shaded side, so the roots bends downwards, back into the ground

50
Q

Roots are

A
  • positively gravitrophic

- negatively phototrophic

51
Q

Shoots are

A
  • negatively gravitrophic

- positively phototrophic

52
Q

What happens to roots that are underground?

A

They arent exposed to light, so they grow downwards due to positive gravitropism

53
Q

How can plant hormones be used as selective weedkillers?

A
  • most weeds in fields are broad-leaved, in contrast to grasses and cereals which have narrow leaves
  • selective weedkillers have been developed from auxins which only affect broad-leaved plants
  • they do this by disrupting the plants growth patterns, which soon kills them
54
Q

How can root powder be used to grow cuttings?

A
  • By adding rooting powder, which contains auxins, cuttings are able to produce roots rapidly and start growing as new plants.
  • This allows growers to produce lots of clones of a really good plant quickly
55
Q

How can plant hormones be used to control flower and fruit formation?

A
  • Gibberelins are hormones that stimulate seed germination, stem growth and flowering. They can be used to make plants flower earlier than they would usually do so, or under conditions in which they wouldnt usually flower
  • They could also be used to reduce flower formation, which can improve fruit quality. e.g. apricot treet often produce too many flowers, this causes many fruits to form and as the tree cant support them all, they grow quite small
56
Q

How can plant hormones be used to produce seedless fruit?

A
  • Fruit only grows on flowering plants that have been pollinated by insects.
  • If the flower isnt pollinated, the fruit and seed may not grow.
  • If plant hormones like gibberelins are applied to unpollinated flowers, the fruit can grow but the seed wont.
57
Q

How can plant hormones be used to control the ripening of fruits

A
  1. the ripening of fruits can be controlled with when they’re still on the plant, or when they’re being transported to shops. This allows the fruit to be picked when its unripe
  2. A ripening hormone called ethene is then added and the fruit will ripen on its way to the supermarket and be perfect just as it reaches the shelf
58
Q

How can plant hormones be used to control seed germination?

A
  • Lots of seeds wont germinate until they’ve been through certain conditions (e.g a period of cold, or of dryness)
  • Seeds can be treated with gibberelins so that plants can germinate at times of year that they wouldn’t normally. It also helps to ensure all the seeds in a batch germinate at the same time

biology (7 decks)

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