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GCSEs > SB6, SB7, SB8, SB9 Biology (paper 2) 📍 > Flashcards

SB6, SB7, 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)

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106
Q

Factors affecting the rate of diffusion

A

• Surface area
• Concentration gradient
• Diffusion distance
• Temperature

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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

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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

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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

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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

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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)

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112
Q

Organelle where exchange of substances occur

A

Cell membrane

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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

Examples of mutualism

A

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

• Nitrogen fixing bacteria live inside root nodules of leguminous plants
• they fix nitrogen for plants
• bacteria gain nutrition and protection from plant

• Oxpeckers feed off parasitic insects that live on herbivores
• reduces disease in herbivores

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 due to surface runoff from precipitation
• 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]

263
Q

Why do farmers use plants like beans/peas for crop rotation?

A

• Increases nitrate levels in soil
• Because nitrogen fixing bacteria live on root nodules of peas/beans
• This converts nitrogen into nitrates

264
Q

[Topic 7]
What chemical do endocrine glands release?

A

Hormones

265
Q

How are hormones transported around the body?

A

Dissolved in blood plasma

266
Q

What are the 6 main endocrine glands?

A

• Pituitary gland (master gland in brain producing FSH and LH)
• Thyroid (produces thyroxine)
• Pancreas (produces insulin and glucagon)
• Adrenal gland (produces adrenaline)
• Testes (produces testosterone)
• Ovaries (produces oestrogen and progesterone)

267
Q

Function of glucagon

A

Controls blood glucose concentration

268
Q

Target organ for glucagon

A

Liver/muscles

269
Q

Effect of adrenalin on liver cells during excersise

A

• Glycogen is broken down into glucose
• Glucose is released by the liver
• Ensures a higher blood glucose concentration for increased respiration

270
Q

How does the release of adrenaline result in improved performance of an athlete?

A

• The heart rate and blood pressure increases
• This increases blood flow
• Allows more glucose and oxygen to be delivered to muscle cells at faster rate
• Increases rate of aerobic respiration
• Therefore more energy can be released for movement

271
Q

What does adrenaline do to blood vessels and why?

A

• It dilates (widens) vessels to allow more blood and glucose to be circulated
• Increases rate of aerobic respiration

272
Q

What enzyme breaks down starch?

A

Amylase

273
Q

What does the release of thyroxine stimulate?

A

The metabolism rate

274
Q

What does LH mean?

A

Luteinising hormone

275
Q

What does FSH mean?

A

Follicle stimulating hormone

276
Q

What are the 2 hormones that keep thyroxine concentration stable?

A

• TRH (Thyrotropin releasing hormone)
• TSH (Thyroid stimulating hormone)

277
Q

Describe process of negative feedback if thyroxine concentration is high

A

• High thyroxine levels inhibits the hypothalamus for releasing TRH
• This inhibits the pituitary gland from releasing TSH
• This inhibits the thyroid gland from releasing thyroxine

278
Q

How does an underactive thyroid gland contribute to an increased body mass?

A

• Thyroid gland produces thyroxine
• Thyroxine regulates metabolic rate
• An underactive thyroid causes less thyroxine to be produced
• Metabolic rate therefore decreases
• So there’s a lower break down of carbohydrates and less energy being released
• Increases fat storage and body mass

279
Q

How do hormones control the menstrual cycle?

A

• At the start, the pituitary gland releases FSH which causes the egg to develop in the follicle
• This stimulates the secretion of oestrogen in the ovaries and causes the uterus lining to thicken
• When oestrogen levels are high enough it stimulates the release of LH from pituitary gland causing ovulation
• Progesterone levels from corpus luteum start to increase in order to maintain uterus lining
• If egg is fertilised the oestrogen and progesterone levels remain high to maintain uterus lining

280
Q

What happens if the egg is not fertilised by the end of the menstrual cycle?

A

• The corpus luteum breaks down
• The uterus lining breaks
• Progesterone levels drop
• This causes menstruation (period)

281
Q

What day does ovulation occur?

A

Day 14

GCSEs (21 decks)

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