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Biology > Organisation 4 > Flashcards

Organisation 4 Flashcards

Plant organisation

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1
Q

Examples of plant tissues

A

-epidermal tissues
-palisade mesophyll
-spongy mesophyll
-xylem and phloem
-meristem tissue

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2
Q

The leaf is a…

A

plant organ

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3
Q

Epidermal tissue

A

Covers the whole plant

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4
Q

Palisade mesophyll tissue

A

The part of the leaf where photosynthesis happens.

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5
Q

Spongy mesophyll tissue

A

-In the leaf

-Contains big air spaces to allow gases to diffuse in and out of cells

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6
Q

Xylem and Phloem (brief)

A

Transport things like water, mineral ions, and food around the plant.

(Through the roots, stem, and leaves).

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7
Q

Meristem tissue

A

-Found at the growing tips of roots and shoots

-Is able to differentiate into lots of different types of plant cell, allowing the plant to grow.

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8
Q

What is the order of tissues top to bottom in a leaf?

A

-epidermal
-palisade mesophyll
-spongy mesophyll
-epidermal

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9
Q

How are the epidermal tissues adapted to their function?

A

Covered with a waxy cuticle which helps to reduce water loss by evaporation.

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10
Q

How is the upper epidermis adapted to its function?

A

Transparent so light can pass through it to the palisade layer.

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11
Q

How is the palisade layer adapted to its function?

A

It has lots of chloroplasts.

This means they are near the top of the leaf where they can get the most light.

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12
Q

What do xylem and phloem tubes do?

A

They form a network of vascular bundles which deliver water and other nutrients to the entire leaf, and take away the glucose produced by photosynthesis.

They also help to support the leaf’s structure.

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13
Q

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

A

-Lower epidermis is full of little holes called stomata, which let CO2 diffuse directly into the leaf.

-The opening and closing of stomata is controlled by guard cells in response to environmental conditions.

-Air spaces in the spongy mesophyll tissue increase the rate of diffusion of gases.

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14
Q

What is the role of guard cells?

A

To control the opening and closing of the stomata in response to environmental conditions.

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15
Q

The organ system for transport of substances around the plant is made of…

A

the roots, stem, and leaves.

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16
Q

transpiration stream

A

the movement of water from the roots, through the xylem, and out of the leaves.

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17
Q

why might water escape from the stomata by diffusion?

A

(If) There’s more water in the plant than in the air outside, the water escapes from the leaves through the stomata by diffusion.

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18
Q

Transpiration (step 1)

A
  1. Transpiration is caused by the evaporation and diffusion of water from a plant’s surface.

Most transpiration happens at the leaves.

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19
Q

Transpiration (step 2)

A
  1. This evaporation creates a slight shortage of water in the leaf, and so more water is drawn up from the rest of the plant through the xylem vessels to replace it.
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20
Q

Transpiration (step 3)

A
  1. This in turn means more water is drawn up from the roots, and so there’s a constant transpiration stream of water through the plant.
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21
Q

What factors affect the rate of transpiration?

A

-Light intensity
-Temperature
-Air flow
-Humidity

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22
Q

Which factor decreases the rate of transpiration?

A

Humidity.

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23
Q

How does light intensity affect the rate of transpiration?

A

The brighter the light, the greater the transpiration rate.

24
Q

How does temperature affect the rate of transpiration?

A

The warmer it gets, the faster the rate of transpiration.

25
Q

How does air flow affect the rate of transpiration?

A

The better the air flow around a leaf (stronger wind), the greater the rate of transpiration.

26
Q

Why does good air flow increase the rate of transpiration?

A

Water vapour is swept away, maintaining a low concentration of water in the air outside the leaf.

Diffusion can happen quickly, from an area of high to low concentration.

27
Q

when asked to make improvements to someone’s experiment, think about…

A

…experimental controls.

28
Q

How does humidity affect the rate of transpiration?

A

If the air is humid, there is not much difference between the inside and outside of a leaf in terms of water concentration, so the rate of diffusion is slower.

29
Q

What happens when a plant has lots of water?

A

The water diffuses into the guard cells via osmosis so they go plump and turgid.

This makes the stomata open so gases can be exchanged for photosynthesis.

30
Q

Guard cell adaptations (random)

A

-kidney shape which opens and closes the stomata

-thin outer walls and thickened inner walls make the opening and closing work

-They are sensitive to light so close at night

-This saves water whilst maximising photosynthesis.

31
Q

Why are more stomata found on the underside of a leaf than the top?

A

The lower surface is shaded and cooler.

So less water is lost through the stomata here than if they were on the top. (less evaporation).

32
Q

What is the role of stomata and guard cells?

A

-To control gas exchange within a leaf

-To control water loss within a leaf

33
Q

Translocation

A

The movement of food molecules (dissolved sugars) through phloem tissue.

34
Q

Where is meristem tissue found?

A

The growing tips of roots and shoots.

35
Q

What are root hair cells specialised for?

A

The efficient uptake of water (by osmosis), and mineral ions (by active transport) from the soil.

36
Q

How are root hair cells adapted for their function?

A

They have a hair-like structure

This gives the plant a large surface area for the efficient uptake of water (by osmosis), and mineral ions (by active transport) from the soil.

37
Q

What is phloem tissue specialised for?

A

Transporting dissolved sugars made in the leaves to the rest of the plant for either immediate use or storage.

38
Q

How is phloem adapted for its function?

A

-Made of columns of elongated cells so long

-These join end to end to form phloem tubes

-Have few sub-cellular structures so that cell sap can easily flow in both directions

39
Q

What is xylem tissue specialised for?

A

Transporting water and mineral ions from the roots to the stem and the leaves.

40
Q

How is xylem tissue adapted for its function?

A

-Made of columns of dead cells so long

-These join end to end to form xylem tubes

-Hollow to allow water and mineral ions to flow through them easily

-Strengthened with a material called lignin

41
Q

What are root hair cells?

A

Cells on the surface of plant roots.

42
Q

How do root hair cells take up water?

A

By osmosis

43
Q

How do root hair cells take up mineral ions?

A

By active transport

44
Q

Why is the rate of transpiration low(er) in the dark?

A

Photosynthesis can’t happen in the dark, so the stomata don’t need to be open to let CO2 in.

So, stomata begin to close as it gets darker.

When the stomata are closed, very little water can escape.

45
Q

Why is there a faster rate of transpiration in high(er) temperatures?

A

When it’s warm, the water particles have more energy to evaporate and diffuse out of the stomata.

46
Q

Why is there a slower rate of transpiration if there is little air flow?

A

If air flow is poor, water vapour surrounds the leaf and doesn’t move away.

This means that there is a high concentration of water particles both outside and inside the leaf.

Which means there is a gentle concentration gradient, and so less fast diffusion.

47
Q

How does cell sap move from one phloem cell to the next?

A

Through pores in the end walls.

48
Q

What is xylem tissue composed of?

A

Hollow tubes made of dead cells strengthened by lignin, adapted for the transport of water in the transpiration stream.

49
Q

What happens if a plant is short of water?

A

The guard cells lose water via osmosis and become flaccid.

This makes the stomata close and stops too much water vapour from escaping.

50
Q

Transpiration is a side effect of what?

A

The way that leaves are adapted for photosynthesis.

They have to have stomata so that gases can be exchanged easily.

Because there’s more water inside the plant than in the air outside, water escapes out of the leaves via diffusion.

It then must be replaced.

51
Q

What is the transpiration stream?

A

The movement of water from the roots, through the xylem, and out of the leaves.

52
Q

How can we estimate the rate of transpiration?

A

Measuring the uptake of water by a plant using a potometer.

53
Q

Why is it that we can estimate the rate of transpiration by measuring the uptake of water by a plant?

A

Because we can assume that the water uptake by a plant is directly related o water loss by the leaves (transpiration).

54
Q

How do we use a potometer to estimate the rate of transpiration?

A

-Set up apparatus (diagram)

-Record the starting position of the air bubble

-Start a stopwatch

-Record the distance moved by the bubble per unit time e.g. per hour

55
Q

What conditions must we keep constant when using a potometer to estimate the rate of transpiration

A

-Temperature

-Air humidity

Biology (18 decks)

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