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GCSEs > SB6, SB8, SB9 Biology (paper 2) 📍 > Flashcards

SB6, SB8, SB9 Biology (paper 2) 📍 Flashcards

1
Q

Chloroplast definition

A

site of photosynthesis

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2
Q

organelles in a plant cell

A

cell wall, vacuole, chloroplast, mitochondria, ribosomes, nucleus, cell membrane, cytoplasm

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3
Q

Reagent used to test for starch

A

Iodine

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4
Q

What are the plant organs

A

Stem, root and leaves

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5
Q

what are the tissue layers in a leaf?

A

• Cuticle
• Upper epidermis
• Palisade mesophyll
• Spongy mesophyll
• Lower epidermis

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6
Q

What tissue layer does photosynthesis occur in?

A

Palisade mesophyll

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7
Q

What is the cuticle?

A

• A waxy waterproof, transparent layer
• Reduces water loss during evaporation
• Acts as a layer of protection

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8
Q

What is the upper epidermis?

A

Transparent layer in order to allow light to be absorbed

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9
Q

Palisade mesophyll tissue layer

A

Large number of palisade cells are found here to maximise rate of protein synthesis

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10
Q

Adaptation of the spongy mesophyll

A

Contains air spaces to maximise surface area and increase gas exchange

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11
Q

Function of the guard cells

A

• Controls the opening and closing of the stomata
• Allows gases to diffuse in or out
• Also allows water vapour to leave

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12
Q

What are the 2 transport vessels in a plant?

A

Xylem and phloem

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13
Q

Function of xylem

A

Transports water and dissolved mineral ions

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14
Q

Function of phloem

A

Transports sucrose (sugar) and amino acids

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15
Q

Endothermic reaction

A

Chemical reaction where heat is absorbed

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16
Q

Function of roots

A

Absorb water and nutrients from the soil

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17
Q

Photosynthesis definition

A

the process by which plants convert sunlight, water, and carbon dioxide into oxygen and glucose.

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18
Q

Autotroph meaning

A

Plants can make complex molecules (glucose) from simple molecules (co2 and water)

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19
Q

Producer meaning

A

Organisms (plants) that are able to make their own food and therefore are at the start of all food chains

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20
Q

Word equation for photosynthesis

A

Carbon dioxide + Water
—> Glucose + Oxygen

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21
Q

Function of glucose in plants

A

• Produces starch for storage
• Helps with respiration
• Synthesises lipids to provide seeds with energy
• Form cellulose to make cell walls

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22
Q

Function of oxygen in plants

A

Helps with respiration or it diffuses out

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23
Q

Diffusion definition

A

Movement of particles from high to low concentration

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24
Q

What is a limiting factor?

A

Factor that slows down rate of a process (eg photosynthesis)

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25
Q

3 factors that can affect rate of photosynthesis

A

Temperature, C02 concentration and light intensity

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26
Q

Denatured meaning

A

When the active site of an enzyme loses its shape and is no longer complementary to the substrate

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27
Q

Pigment found in chloroplasts

A

Chlorophyll

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28
Q

Factors that affect amount of chloroplasts

A

Amount of leaves, amount of nutrients, diseases

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29
Q

Equipment that can be used to measure light intensity

A

Light meter

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30
Q

What is light measured in?

A

Lux

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31
Q

Why is there a higher concentration of carbon dioxide at night in plants?

A

there’s a higher rate of respiration as it doesn’t photosynthesise. This produces more carbon dioxide.

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32
Q

How does a high temperature affect the rate of photosynthesis?

A

Enzymes become denatured [state meaning]

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33
Q

How do low temperatures affect the rate of photosynthesis?

A

Less kinetic energy is present therefore less collisions occurs between molecules meaning that less reactions happen

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34
Q

What’s the optimum temperature for photosynthesis

A

25 degrees Celsius

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35
Q

How do guard cells control the opening and closing of the stomata?

A

When the plant has a sufficient amount of water, the guard cells take in the water and swell (turgid) causing the stomata to open to allow gas exchange.

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36
Q

Inverse square law calculation

A

1/d² - Light intensity is inversely proportional to distance

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37
Q

Method to measure volume of gas released in photosynthesis

A

[might come soon]

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38
Q

adaptations of root hair cells

A

• Absorbs water (by osmosis) and mineral ions (active transport)
• Has extensions to increase its surface area and increase absorption

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39
Q

What organelle do roots hair cells not have and why?

A

Chloroplast because they are underground and cannot absorb light for photosynthesis

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40
Q

Active transport meaning

A

An energy requiring process where substances are moved across a cell membrane against their concentration gradient

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41
Q

Osmosis meaning

A

Movement of water molecules across a semi permeable membrane from a high concentration to low concentration

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42
Q

Direction of flow in xylem

A

Upwards and unidirectional

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43
Q

Location of xylem in relation to phloem in a vascular bundle

A

Xylem is on the inside whereas the Phloem is on the outside

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44
Q

function of sucrose

A

transports amino acids

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45
Q

How is water transported in a plant

A

Absorbed through osmosis in the root and then up the xylem through transpiration

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46
Q

Define transpiration

A

The pull of water from the root to the leaves to replace the evaporated water

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47
Q

Monomer of sucrose

A

Glucose

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48
Q

Function of sodium hydrogen carbonate

A

Provides plant with Co2 when added to water to support with photosynthesis

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49
Q

Function of protease

A

Breaks down proteins in cell membrane

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50
Q

adaptations of the xylem

A

• No end walls (to form hollow tubes for water to be drawn)
• Contains no cytoplasm (for free passage of water)
• Lignin thickens the outer walls (to strengthen tubes)

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51
Q

Adaptations of the phloem

A

• Cells have few organelles (to aid the flow of sugars and amino acids)
• Cells are joined end to end by sieve plates (forming tubes to allow translocation)
• Small pores in end walls let substances through

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52
Q

Companion cell function

A

Supports the transport of sugars and amino acids from the leaves to phloem by providing energy

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53
Q

Translocation meaning

A

Active transport of sugars from leaves into phloem

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54
Q

Direction of flow in phloem

A

Bidirectional

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55
Q

Xerophytic plant meaning

A

Plant adapted to survive in extreme conditions

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56
Q

Examples of xerophytic plants

A

Cacti and Marram grass

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57
Q

Adaptations of xerophytic plants

A

• stem stores water
• stomata opens at night (because it’s cooler and reduces water loss)
• hairs on stem (to trap water vapour)
• waxy, thick cuticle

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58
Q

Structural adaptations of marram grass in a hot, windy and dry environment

A

Its leaves roll up to reduce exposure to wind (minimising water loss) • Thick cuticle to reduce water loss • Hairs on inner surface of the leaf (trapping air to reduce water loss)

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59
Q

Plant adaptations of marram grass in a hot, windy and dry environment

A

• Long thin leaves to reduce air resistance • strong root structure to prevent being uprooted • flexible to avoid breaking (in windy conditions)

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60
Q

Pathway of water in a plant

A

Root hair cells -> Root cortex cells -> Xylem -> Leaf mesophyll cells

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61
Q

Why does the stomata open during the day?

A

• Higher light intensity allows for gas exchange (photosynthesis) • which allows water vapour to leave during transpiration

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62
Q

Why does the stomata close during the night?

A

To conserve water as the rate of transpiration is reduced (photosynthesis can’t occur)

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63
Q

Turgid meaning

A

Swollen

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64
Q

What happens when water leaves the guard cells?

A

The guard cells become flaccid • Stomata also closes

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65
Q

Cohesion meaning

A

When water molecules stick together

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66
Q

Function of transpiration

A

• Transports mineral ions • Provides water to keep cells turgid for photosynthesis • Keeps leaves cool (water evaporates)

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67
Q

How is the flow of water continuous

A

Due to the cohesion of water it creates a continuous unbroken column

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68
Q

Factors that affect the rate of transpiration

A

• Temperature • Light intensity • Air movement • Humidity

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69
Q

How does temperature affect transpiration?

A

• A higher temperature increases kinetic energy of water molecules • This makes transpiration through evaporation faster

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70
Q

How does light intensity affect transpiration?

A

• A higher light intensity would increase the rate of photosynthesis by opening more stomata for co2 to diffuse in • This allows more water to evaporate

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71
Q

How does air movement affect transpiration?

A

• Moving air removes water vapour in the air and increases the concentration gradient • Allows evaporation to happen faster

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72
Q

How does humidity affect transpiration?

A

• A lot of water vapour in the air reduces the water concentration gradient • This decreases the rate of evaporation

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73
Q

Potometer meaning

A

Apparatus used to measure the rate of transpiration

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74
Q

Why is the shoot (upper part of plant) cut under water?

A

To prevent air entering the xylem

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75
Q

Why are the leaves of the shoot dried?

A

To remove any excess water

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76
Q

Equation to work out the rate of transpiration

A

Rate = Distance moved by air bubble (m) / Time (min)

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77
Q

How can we reduce leaking in a potometer?

A

Assemble equipment underwater

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78
Q

Source meaning

A

Where the products are made

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79
Q

Sink meaning

A

Where the products are stored/ used

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80
Q

Phototropism meaning

A

Response to light in a directional movement

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81
Q

Geotropism meaning

A

Response to gravity in a directional movement

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82
Q

What tropic responses do shoots have?

A

Shoots have a positive phototropism and a negative geotropism

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83
Q

What tropic responses do roots have?

A

Roots have a negative phototropism and a positive geotropism

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84
Q

What are auxins?

A

Growth regulators synthesised in the tips of shoots and roots

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85
Q

How are auxins distributed in phototropism?

A

• Auxins are synthesised in the tips of shoots • Auxins diffuse to the shaded side in response to light • This increases the concentration of auxins in the shaded side • Therefore cells in the shaded side elongate at a faster rate • Causing the shoot to bend towards the light

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86
Q

What are auxins similar to?

A

Hormones

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87
Q

How are auxins distributed in geotropism?

A

Auxins are synthesised in the tips of roots • Auxins diffuse to the lower side • This increases the concentration of auxins in the lower side and inhibits cell elongation • Causing the cells at the top of the root to elongate at a faster rate (in response to gravity)

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88
Q

What are plant hormones used by farmers for?

A

To obtain larger yields

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89
Q

What are three plant hormones?

A

Auxins, ethenes and gibberellins

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90
Q

How are auxins used commercially?

A

They are used as weed killers to maximise yield • Sold as rooting powders to encourage rapid development of roots

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91
Q

What is the commercial use of ethene?

A

It controls the ripening of fruit

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92
Q

How are gibberellins used commercially?

A

They end seed dormancy: promoting seed germination • Produce seedless fruit • Increase fruit size

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93
Q

Seed dormancy definition

A

When seeds are unable to germinate even under ideal growing conditions

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94
Q

Concentration gradient meaning

A

A difference between two concentrations

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95
Q

Dependent variable meaning

A

The variable you measure

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96
Q

Independent variable meaning

A

The variable you change

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97
Q

The rate of photosynthesis is directly proportional to what?

A

Light intensity

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98
Q

[SB8]
What substances are exchanged in and out of organisms?

A

• Oxygen
• Carbon dioxide (waste)
• Water
• Dissolved food molecules (eg glucose)
• Mineral ions
• Urea (waste)

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99
Q

What are the transport processes?

A

• Diffusion
• Osmosis
• Active transport

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100
Q

Why do multi cellular organisms need exchange surfaces?

A

• The distance between the surface and its centre is long (long diffusion distance)
• They have a small surface area in comparison to their volumes (SA:V)
• The transport processes cannot happen sufficiently without them

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101
Q

How is villi adapted for absorption?

A

• It’s the folded membrane of small intestines
• This increases SA and absorption rate of digested food

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102
Q

Transport system in animals

A

• The blood and circulatory system

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103
Q

Exchange surfaces in animals

A

• Lungs and alveoli for gas exchange
• Small intestines and villi for absorption of digested food

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104
Q

Transport systems in plants

A

• Xylem (moves water and mineral ions from roots to shoots)
• Phloem (moves sugars and amino acids to where necessary)

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105
Q

Exchange surfaces in plants

A

• Roots and hairs (mineral ions and water are absorbed)
• Leaves (stomata - gas exchange)

106
Q

Factors affecting the rate of diffusion

A

• Surface area
• Concentration gradient
• Diffusion distance
• Temperature

107
Q

How does surface area affect the rate of diffusion?

A

• The bigger a cell the smaller its surface area to volume ratio
• This slows down the rate of diffusion

108
Q

How does diffusion distance affect the rate of diffusion?

A

• The smaller the distance molecules travel, the faster the transport
• Eg blood capillaries and alveoli have walls one cell thick
• This increases the rate of diffusion

109
Q

How does the concentration gradient affect the rate of diffusion?

A

• The greater the difference in concentration the faster the movement
• Therefore more random collisions will occur against the membrane

110
Q

How does temperature affect the diffusion rate?

A

• The higher the temperature, the faster molecules move as they have more kinetic energy
• This results in more collisions against the cell membrane and a faster rate of movement across it

111
Q

What is Fick’s law?

A

Diffusion rate ∝ (surface area x concentration gradient) / diffusion distance

• The rate of diffusion is directly proportional to the surface area and concentration gradient
• But inversely proportional to the thickness of the membrane (diffusion distance)

112
Q

Organelle where exchange of substances occur

A

Cell membrane

113
Q

What type of reaction is respiration?

A

An exothermic reaction

114
Q

Products formed when lipids are digested

A

Fatty acids and glycerol

115
Q

Why do organisms need energy?

A

• Chemical reactions to build large molecules from smaller ones
• Muscle contraction to allow movement
• Keeping warm (to maintain a constant temperature for optimum enzyme activity)

116
Q

Definition of aerobic respiration

A

The chemical reaction in cells that uses oxygen to completely break down nutrient molecules to release energy

117
Q

Aerobic respiration word equation

A

Glucose + Oxygen —> Carbon dioxide + Water

118
Q

Where does aerobic respiration occur in a cell?

A

Mitochondria

119
Q

Products in respiration

A

• Carbon dioxide
• Water
• Useful energy

120
Q

Anaerobic respiration definition

A

Chemical reaction in cells that partially breaks down nutrient molecules to release energy without using oxygen

121
Q

Differences between aerobic and anaerobic respiration

A

• Aerobic respiration requires oxygen whilst anaerobic doesn’t
• Glucose is only completely broken down aerobically
• Aerobic respiration releases larger amounts of energy

122
Q

Chemical equation for aerobic respiration

A

C6H12O6 + 6O2 —> 6CO2 + 6H2O
(+ energy/ATP)

123
Q

What is ATP?

A

• Short term energy store in all cells
• Universal energy carrier

124
Q

Where does anaerobic respiration take place?

A

Muscle cells during vigorous exercise

125
Q

Why do our bodies use anaerobic respiration?

A

• When we exercise at high intensities our muscles have a higher demand for energy
• Therefore oxygen is likely to run out and when it does glucose is broken down without it, producing lactic acid instead
• Glucose has not been fully broken down so there’s still energy stored in the bonds of lactic acid molecules
• Which results in less energy being released

126
Q

Word equation for anaerobic respiration in animals

A

Glucose —> Lactic acid

127
Q

Effect of lactic acid buildup

A

It lowers the pH of the muscle tissue as it makes the blood more acidic

128
Q

Oxygen debt

A

The amount of oxygen required to break down the lactic acid that has built up

129
Q

Which organisms other than animals respire anaerobically?

A

• Plants
• Yeast (fungi)

130
Q

What is fermentation?

A

Anaerobic respiration in yeast cells

131
Q

What is the economic importance of fermentation?

A

• It’s used in the manufacturing of bread
(CO2 helps the dough to rise)

• It’s used in brewing
(ethanol produced makes beer)

132
Q

Word equation for anaerobic respiration in plants and fungi

A

Glucose —> Alcohol + Carbon dioxide

133
Q

How is iodine used to test for starch?

A

It changes its colour to blue/black

134
Q

Purpose of soda lime in the rate of respiration practical

A

It absorbs any co2 to prevent it affecting the measuring of oxygen

135
Q

Purpose of cotton wool in the rate of respiration practical

A

It protects us and the organisms used from the soda lime because it’s harmful

136
Q

Purpose of inserting a bung with the capillary tube

A

• Allows us to accurately measure how much oxygen is used up
• No air is lost/gained from surrounding area

137
Q

Purpose of setting up a control tube

A

The tube will have no organisms in it to ensure results are only due to respiration

138
Q

Why do we time for 5 minutes after marking the position of the coloured liquid?

A

• Time is the control variable and prevents results from being affected

139
Q

Why do we measure the distance the liquid has travelled in the rate of respiration practical?

A

• It is the dependent variable
• It allows us to see how much oxygen has been consumed

140
Q

Why do we repeat the rate of respiration practical at different temperatures?

A

• Independent variable
• Range of temperatures would help identify the effect it has on respiration

141
Q

What are the 4 blood components?

A

• Red blood cells
• White blood cells
• Plasma
• Platelets

142
Q

What are the 3 types of blood vessels?

A

• Arteries
• Veins
• Capillaries

143
Q

What is a eukaryotic cell?

A

A cell that contains genetic information within a nucleus

144
Q

Adaptations of the alveoli

A

• They are small sacs that increase the SA:V ratio

• They have thin single layers of cells to minimise diffusion distance

• They have ventilation to maintain high levels of O2 entering lungs and low levels of CO2

• They have a good blood supply to ensure a constant supply of blood high in CO2 and low in O2

• They have a layer of moisture on the surface to dissolve gases which supports diffusion

145
Q

What does ventilation and a good blood supply do for alveoli?

A

It maintains the concentration gradient

146
Q

What is blood?

A

The liquid that transports important substances around the body
(eg oxygen and glucose)

147
Q

Functions of the blood

A

• Helps defend the body against pathogens
• Helps control body temperature
• Helps to maintain the pH of cells

148
Q

Function of plasma

A

• Carries red and white blood cells and platelets
• Carries dissolved substances eg glucose and oxygen

149
Q

What colour is plasma?

A

Yellow

150
Q

Why is the blood red?

A

Due to the haemoglobin in red blood cells

151
Q

What is haemoglobin?

A

The pigment in red blood cells that binds to oxygen and transports it

152
Q

Function of red blood cells

A

They carry oxygen from the air in our lungs to our respiring cells

153
Q

Function of white blood cells

A

• Form part of the immune system (fights against infection)
• Lymphocytes produce antibodies
• Phagocytes engulf and digest pathogens

154
Q

What are platelets?

A

Small fragments of cells without a nucleus and are involved in the clotting of blood

155
Q

Function of platelets

A

• Helps with the clotting of blood
• Clotting forms a network of fibres that trap more platelets and red blood cells to form a scab
• This protects the new skin as it grows underneath
• This also prevents microorganisms from entering

156
Q

Adaptations of red blood cells

A

• Are biconcave disks which increases their SA:V ratio and also diffusion
• Are packed with haemoglobin which binds to O2
• Have no nucleus which allows more space for haemoglobin
• Haemoglobin contains an atom of iron which gives the pigment its red colour (is brightest when lots of oxygen is bound to it)

157
Q

Anaemia meaning

A

Not having enough red blood cells in the body

158
Q

Sickle cell anemia

A

• Consists of deformed red blood cells (loss of biconcave shape)

• Blood cells have a smaller volume and so cannot hold as much haemoglobin (and therefore cannot carry as much oxygen)

• Smaller surface area means that diffusion of oxygen is slower

• Shape can cause blood vessels to block which decreases blood flow

159
Q

Impacts of having sickle cell anaemia

A

• Sufferers get breathless quickly and are often tired
• Less able to do exercise as muscles get tired quickly

160
Q

Function of the arteries

A

• They carry oxygenated blood away from the heart and to the body
• Blood is under a high pressure

161
Q

Adaptations of the arteries

A

• Have a thick layer of muscle and elastic fibres and also thick walls
• This helps it withstand the high pressure and be able to stretch

• Also have a narrow lumen to maintain high pressure

162
Q

Function of the veins

A

• They carry deoxygenated blood away from organs towards the heart
• Blood is carried under low pressure

163
Q

Adaptations of the veins

A

• They have a larger lumen and thin walls because blood is under low pressure
• Veins have valves to prevent blood flowing backwards due to gravity

164
Q

How are the veins assisted with blood flow?

A

Muscles in the legs and arms help to push blood along the veins when moving

165
Q

Function of the capillaries

A

They connect arteries and veins

166
Q

Adaptations of the capillaries

A

• They are very narrow with thin walls one cell thick to minimise diffusion distance
• This increases the diffusion rate

• Also they have very narrow lumens that only allow 1 red blood cell to pass at a time
• This slows blood flow to increase the time oxygen diffuses into cells
• And maximises the diffusion of oxygen

167
Q

How many chambers does the heart have and where are they found?

A

• 4
• Two upper chambers - left and right atrium
• Two lower chambers - left and right ventricles

168
Q

What type of blood does the left side of heart carry?

A

Oxygenated blood

169
Q

What type of blood does the right side of heart carry?

A

Deoxygenated blood

170
Q

Function of the heart

A

Pumps blood around our body

171
Q

Adaptations of the heart

A

• Made of 2 pumps
• The walls of our heart is mostly made of muscle
• A muscle wall (septum) separates the two sides of the heart
• Left ventricle is thicker which allows blood leaving it to be under high pressure as it pumps blood around the body

172
Q

What is the coronary artery?

A

The blood vessel that supplies the heart with oxygen

173
Q

What is the vena cava?

A

A vein that brings deoxygenated blood back to the heart

174
Q

Describe the flow of deoxygenated blood through the heart (1)

A

• Blood flows through the vena cava then ➡️ right atrium
• Blood flows to ➡️ the right ventricle
• The tricuspid valve closes to prevent back flow
• The right ventricle contracts to force the deoxygenated blood into ➡️ the pulmonary artery
• Blood travels to ➡️ the lungs to pick up oxygen

175
Q

Describe the flow of oxygenated blood through the heart (2)

A

• The newly oxygenated blood is returned to the heart by the pulmonary vein and flows into ➡️ the left atrium
• Blood flows into ➡️ the left ventricle and the bicuspid valve closes to prevent back flow
• The left ventricle pumps oxygenated blood around the body through ➡️ the aorta

176
Q

Cardiac output definition

A

The volume of blood that is pumped by the heart per unit time

177
Q

What impact does being fitter have on cardiac output?

A

Fitter people have higher cardiac outputs due to having thicker and stronger ventricular muscles in the heart

178
Q

Heart rate meaning

A

The number of times a heart beats per minute

179
Q

Stroke volume meaning

A

The volume of blood pumped out of the the left ventricle during one cardiac cycle

180
Q

Calculation for cardiac output (cm³min-¹)

A

Heart rate (bpm) x Stroke volume (cm³)

181
Q

What is the aorta?

A

Artery that transports oxygenated blood from the heart to the rest of the body

182
Q

Tropism meaning

A

A plant’s response to stimulus

183
Q

[[SB9]]
What is a population?

A

The number of individuals of a species in an area

184
Q

What is a community?

A

The number of individuals of all species in an area

185
Q

What is an ecosystem?

A

All the living organisms and the non-living components in an area

186
Q

Biotic factor definition and examples

A

A living factor that affects an ecosystem

Eg:
• Food availability (plants)
• Predators (animals)
• Pathogens
• Competition

187
Q

Abiotic factors definition and examples

A

A non-living factor that affects an ecosystem

Eg;
• soil pH and mineral content
• light intensity
• co2 levels for plants
• moisture levels

188
Q

Interdependence meaning

A

When species rely on each other for survival

189
Q

Resources plants and animals could compete for

A

• Food
• Space
• Water
• Mates
• Pollination

190
Q

How could you improve an investigation?

A

Repeating it to:
• Calculate a mean
• Collect more data
• Identify anomalies

191
Q

Examples of interactions that create interdependence in a community

A

• Parasitism
• Mutualism

192
Q

What is mutualism?

A

A relationship between two species where both benefit

193
Q

What is parasitism?

A

A relationship between two species where the parasite benefits but the host is harmed

194
Q

Example of parasitism

A

Fleas feed on the host’s blood but don’t provide anything to the host in return

195
Q

Example of mutualism

A

Bees gain nectar from flowers and they spread pollen as they visit different ones helping with reproduction

196
Q

Biodiversity meaning

A

The range and variety of different species in an area

197
Q

Importance of biodiversity

A

High biodiversity ensures the stability of ecosystems and reduces the dependence on one species for:
• Food
• Shelter
• Maintenance of the physical environment

198
Q

Methods of assessing abundance and distribution of organisms

A

• Quadrats
• Belt transects

199
Q

Abundance meaning

A

The number of individuals of a species

200
Q

Distribution meaning

A

How a species is spread through out an ecosystem

201
Q

What is a quadrat?

A

A square frame used to collect samples and measure biodiversity

202
Q

What is a belt transect?

A

A straight line that runs parallel with a suspected change in factor along which samples are taken

203
Q

Formula for estimating the abundance of a species in an ecosystem

A

Total number of organisms in all quadrats x (total area sampled / area of quadrat)

204
Q

How can we make samples more representative of an ecosystem?

A

• Increase the number of samples
• Use a random sampling method

205
Q

Random sampling meaning

A

Collecting samples in an unbiased way

206
Q

What are quadrats used to estimate?

A

The abundance of a species in an ecosystem (using random sampling)

207
Q

How do we use a quadrat?

A

• The sampling area is converted to a grid format
• A random number generator is used to pick the sample points
• The quadrat is laid on the chosen sample point
• We can then estimate the abundance using the number of organisms (plants) in the quadrat

208
Q

What are belt transects used to estimate?

A

The distribution of a species in an ecosystem (using systematic sampling)

209
Q

How do we use a belt transect?

A

• Lay out a measuring tape in a straight line across sample area
• Place quadrats at regular intervals along the tape
• Measure the abiotic factors at each point to identify how it affects abundance
• Record abundance of each species within each quadrat

210
Q

When plotting a graph, which variables goes on the x and y axis?

A

x-axis: Independent variable
y-axis: Dependent variable

211
Q

What are the dependent, independent and control variables in the quadrats and transects practical?

A

Dependent variable: The abundance

Independent variable: Abiotic factor

Control variable: Quadrat (placed at top left corner)

212
Q

Trophic levels meaning

A

The feeding relationships between organisms

213
Q

Food chain meaning

A

Shows the transfer of energy from one organism to the next

214
Q

What is energy stored as at each trophic level in a food chain/web?

A

Biomass

215
Q

Maximum number of trophic levels in a food chain/web

A

Between 4 and 5

216
Q

Why is the efficiency of energy transfer between trophic levels low?

A

• Energy is lost as it gets transferred

This is because:
• Organisms rarely eat every part of the organism they’re eating (eg bones which are inedible)

• Some ingested material is egested (excreted) as faeces

• Energy is absorbed for:
• Movement
• Heat generation
• Metabolic processes

217
Q

What is a pyramid of biomass?

A

Shows how much mass the creatures at each level have without the water in them (dry mass)

218
Q

Roughly what percentage of energy of each trophic level is passed on to the next?

A

10%

219
Q

Characteristics and importance of nitrogen

A

• Needed to make proteins and DNA in plants and animals
• Is an unreactive gas
• Makes up about 78% of atmosphere

220
Q

Describe the process of the nitrogen cycle (6)

A

• Both plants and animals need nitrogen in order to survive and grow, but neither can absorb the nitrogen in the air as it’s unreactive
• Animals get their nitrogen from digesting plants (or other animals), and plants must get their nitrogen from the soil (as nitrates or ammonium ions)

• Nitrogen fixing bacteria in the soil/root nodules of leguminous plants convert N2 gas into ammonium compounds

• Decomposers (fungi & bacteria) convert nitrogen compounds in waste and dead organisms into ammonia
• This forms ammonium ions in the soil

• Nitrifying bacteria converts ammonium ions into nitrites which are then converted into nitrates

• Denitrifying bacteria converts these nitrates into nitrogen gas during respiration and it gets released into the atmosphere

221
Q

How does lightning contribute to the nitrogen cycle?

A

• It can split the bond between the 2 nitrogen atoms
• This turns them into nitrous oxides
• Forms a part of the nitrogen fixing process

222
Q

Crop rotation meaning

A

• When different types of crops are grown in the same area in a cycle to improve soil health
• Usually includes nitrogen fixing crops

223
Q

How is the haber process involved with the nitrogen cycle?

A

• It’s used to make fertilisers
• These provide the soil with nitrates which are absorbed by plants to support making protein and DNA
• This maximises plant growth

224
Q

What are the 4 processes in the nitrogen cycle?

A

• Nitrogen fixation
• Ammonification
• Nitrification
• Denitrification

225
Q

Characteristics and importance of carbon

A

• It’s always transferred as a molecule in the carbon cycle
• CO2 is required for photosynthesis
• Photosynthesis is the only process that takes carbon out of the atmosphere

226
Q

Describe the carbon cycle (6)

A

• Carbon is absorbed from the atmosphere by plants during photosynthesis in the form of CO2

• The carbon is transferred to animals as they feed on it

• Carbon is released into the atmosphere in the form of CO2 as plants, animals and microorganisms respire

• When animals/(plants) excrete waste or die, decomposers feed on it transferring carbon in the process

• The carbon in dead plants and animals can also be converted into fossil fuels over millions of years under much pressure

• When fossil fuels are combusted, the carbon combines with O2 therefore CO2 is released into the atmosphere

227
Q

Describe the water cycle

A

• Water enters the atmosphere as water vapour in two ways
• Energy from the sun heats the Earth’s surface and water evaporates from oceans, rivers, lakes
• Or when plant transpire releasing water vapour into the air

• The warm air rises taking water vapour with it
• The moist air cools down as it rises and water vapour condenses back into liquid water forming clouds

• Water returns to the earth in the form of precipitation

228
Q

Why is water filtered?

A

To make it safe for human consumption, or potable, because it can contain substances harmful to health

229
Q

Biomass definition

A

Mass of living organisms

230
Q

Why do pyramids of biomass have a pyramid shape?

A

The mass of organisms decrease as you go up a food chain

231
Q

In what form does energy enter a food chain/web?

A

As light (used by producers)

232
Q

Formula for efficiency of biomass transfer

A

Biomass in higher trophic level
__________________________________ x 100

Biomass in lower trophic level

233
Q

What factors affect the rate of decomposition?

A

• Temperature
• Water
• Availability of oxygen

234
Q

Decomposition meaning

A

The breaking down and digestion of biological material (waste and dead organisms) by decomposers

235
Q

Why is decomposition important?

A

It ensures that materials like carbon and mineral ions are recycled and returned to the environment

236
Q

How does temperature affect rate of decomposition?

A

• At warmer temperatures, the enzymes involved have more kinetic energy to work at a faster rate which would increase the rate of reactions and decay
• However if it’s too high the enzymes would denature [meaning] and the rate of decay decreases

237
Q

How does water affect rate of decay?

A

• As water availability decreases so does the rate of decomposition
• Decomposers require water to survive
• However if the soil becomes waterlogged, the rate of decay decreases as O2 availability falls

238
Q

How does oxygen levels affect rate of decomposition?

A

Higher oxygen levels mean that decomposers respire more aerobically which gives them more energy to grow and decompose faster

239
Q

What is compost?

A

A mixture of decayed organic material

240
Q

What can compost be used as?

A

A natural fertiliser

241
Q

How can we slow down the rate of decomposition?

A

• Low temperatures eg a fridge slows down the rate of enzyme activity and the reproduction of microorganisms

• Sealed food eg tinned food creates sterile conditions preventing microorganisms contaminating

• Using dried foods lack the water needed by microorganisms for survival therefore they won’t be able to grow on it

242
Q

What 2 types of organisms carry out decomposition?

A

• Detritivores
• Decomposers

243
Q

What are detritivores?

A

Organisms that break down organic matter into small pieces

244
Q

What are decomposers?

A

Microorganisms that feed on dead organisms

245
Q

Examples of detritivores

A

• Maggots
• Worms
• Beetles

246
Q

Examples of decomposers

A

• Bacteria
• Fungi

247
Q

Formula for rate of decomposition

A

change in mass
________________

time taken

248
Q

Why is sea water not suitable for drinking?

A

It contains excess mineral ions (salts) which can lead to dehydration

249
Q

Desalination meaning

A

Removing the excess mineral ions from the water to make it drinkable

250
Q

What are 2 ways of achieving desalination?

A

• Distillation
• Reverse osmosis

251
Q

What happens during distillation in desalination?

A

• Saline water is boiled
• The water vapour is funnelled through a tube
• The water vapour is condensed
• Pure water is collected

252
Q

What happens during reverse osmosis in desalination?

A

• Saline water is forced at high pressure through a partially permeable membrane
• This filters out the mineral ions leaving pure water behind

253
Q

What are indicator species?

A

Organisms whose presence indicates the presence or absence of certain types of pollution

254
Q

What are the indicator species for water pollution?

A

• Bloodworms and sludgeworms (high levels of water pollution)
• Freshwater shrimps and stoneflies (clean water)

255
Q

What are the indicator species for air pollution?

A

• Blackspot fungus on roses (clean air)
• Bushy lichen (clean air)
• Leafy lichen (mild pollution)
• Crusty lichen (more polluted environments)
• Absence of lichens (very heavy pollution)

256
Q

What are lichens?

A

• Organisms that grow in exposed places such as rocks or tree bark
• Indicators of different levels of air pollution

257
Q

What does water pollution consist of?

A

• Raw sewage or fertilisers (both having nitrates) are released into a body of water
• Microorganisms in the water increase in number
• Respiration increases and oxygen in the water is used up

258
Q

What does air pollution consist of?

A

• Sulfur and nitrous dioxide being released into the atmosphere
• Fossil fuel is burnt

259
Q

What is the advantage of using indicator species?

A

They’re cost effective

260
Q

What are the disadvantages of using indicator species?

A

• Can’t give accurate quantitative figures for pollution levels
• Can be hard to see
• Specialists are required

261
Q

What happens during eutrophication?

A

• Nitrates from nearby fertilisers enter a body of water during precipitation due to surface runoff
• Water pollution occurs and an algae bloom tends to occur (nitrate indicator)
• Light becomes blocked by algae
• Plants underwater die as they can’t photosynthesise
• Fish die as they lose prey and O2 levels decreased

262
Q

How can the level of water and air pollution be assessed using living organisms?

A

[might come soon]

GCSEs (21 decks)

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