Biology Paper 2 {SB1, SB6, SB7, SB8, SB9} Flashcards
(324 cards)
1
Q
Chloroplast definition
A
site of photosynthesis
2
Q
organelles in a plant cell
A
cell wall, vacuole, chloroplast, mitochondria, ribosomes, nucleus, cell membrane, cytoplasm
3
Q
Reagent used to test for starch
A
Iodine
4
Q
What are the plant organs
A
Stem, root and leaves
5
Q
what are the tissue layers in a leaf?
A
• Cuticle
• Upper epidermis
• Palisade mesophyll
• Spongy mesophyll
• Lower epidermis
6
Q
What tissue layer does photosynthesis occur in?
A
Palisade mesophyll
7
Q
What is the cuticle?
A
• A waxy waterproof, transparent layer
• Reduces water loss during evaporation
• Acts as a layer of protection
8
Q
What is the upper epidermis?
A
Transparent layer in order to allow light to be absorbed
9
Q
Palisade mesophyll tissue layer
A
Large number of palisade cells are found here to maximise rate of protein synthesis
10
Q
Adaptation of the spongy mesophyll
A
Contains air spaces to maximise surface area and increase gas exchange
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
12
Q
What are the 2 transport vessels in a plant?
A
Xylem and phloem
13
Q
Function of xylem
A
Transports water and dissolved mineral ions
14
Q
Function of phloem
A
Transports sucrose (sugar) and amino acids
15
Q
Endothermic reaction
A
Chemical reaction where heat is absorbed
16
Q
Function of roots
A
Absorb water and nutrients from the soil
17
Q
Photosynthesis definition
A
the process by which plants convert sunlight, water, and carbon dioxide into oxygen and glucose.
18
Q
Autotroph meaning
A
Plants can make complex molecules (glucose) from simple molecules (co2 and water)
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
20
Q
Word equation for photosynthesis
A
Carbon dioxide + Water
—> Glucose + Oxygen
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
22
Q
Function of oxygen in plants
A
Helps with respiration or it diffuses out
23
Q
Diffusion definition
A
Movement of particles from high to low concentration
24
Q
What is a limiting factor?
A
Factor that slows down rate of a process (eg photosynthesis)
25
3 factors that can affect rate of photosynthesis
Temperature, C02 concentration and light intensity
26
Denatured meaning
When the active site of an enzyme loses its shape and is no longer complementary to the substrate
27
Pigment found in chloroplasts
Chlorophyll
28
Factors that affect amount of chloroplasts
Amount of leaves, amount of nutrients, diseases
29
Equipment that can be used to measure light intensity
Light meter
30
What is light measured in?
Lux
31
Why is there a higher concentration of carbon dioxide at night in plants?
there’s a higher rate of respiration as it doesn’t photosynthesise. This produces more carbon dioxide.
32
How does a high temperature affect the rate of photosynthesis?
Enzymes become denatured [state meaning]
33
How do low temperatures affect the rate of photosynthesis?
Less kinetic energy is present therefore less collisions occurs between molecules meaning that less reactions happen
34
What’s the optimum temperature for photosynthesis
25 degrees Celsius
35
How do guard cells control the opening and closing of the stomata?
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.
36
Inverse square law calculation
1/d² - Light intensity is inversely proportional to distance
37
adaptations of root hair cells
• Absorbs water (by osmosis) and mineral ions (active transport)
• Has extensions to increase its surface area and increase absorption
38
What organelle do roots hair cells not have and why?
Chloroplast because they are underground and cannot absorb light for photosynthesis
39
Active transport meaning
An energy requiring process where substances are moved across a cell membrane against their concentration gradient
40
Osmosis meaning
Movement of water molecules across a semi permeable membrane from a high concentration to low concentration
41
Direction of flow in xylem
Upwards and unidirectional
42
Location of xylem in relation to phloem in a vascular bundle
Xylem is on the inside whereas the Phloem is on the outside
43
function of sucrose
transports amino acids
44
How is water transported in a plant
Absorbed through osmosis in the root and then up the xylem through transpiration
45
Define transpiration
The pull of water from the root to the leaves to replace the evaporated water
46
Monomer of sucrose
Glucose
47
Function of sodium hydrogen carbonate
Provides plant with Co2 when added to water to support with photosynthesis
48
Function of protease
Breaks down proteins in cell membrane
49
adaptations of the xylem
• 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)
50
Adaptations of the phloem
• 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
51
Companion cell function
Supports the transport of sugars and amino acids from the leaves to phloem by providing energy
52
Translocation meaning
Active transport of sugars from leaves into phloem
53
Direction of flow in phloem
Bidirectional
54
Xerophytic plant meaning
Plant adapted to survive in extreme conditions
55
Examples of xerophytic plants
Cacti and Marram grass
56
Adaptations of xerophytic plants
• 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
57
Structural adaptations of marram grass in a hot, windy and dry environment
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)
58
Plant adaptations of marram grass in a hot, windy and dry environment
• Long thin leaves to reduce air resistance
• Strong root structure to prevent being uprooted
• Flexible to avoid breaking (in windy conditions)
59
Pathway of water in a plant
Root hair cells -> Root cortex cells -> Xylem -> Leaf mesophyll cells
60
Why does the stomata open during the day?
• Higher light intensity allows for gas exchange (photosynthesis) • which allows water vapour to leave during transpiration
61
Why does the stomata close during the night?
To conserve water as the rate of transpiration is reduced (photosynthesis can’t occur)
62
Turgid meaning
Swollen
63
What happens when water leaves the guard cells?
The guard cells become flaccid • Stomata also closes
64
Cohesion meaning
When water molecules stick together
65
Function of transpiration
• Transports mineral ions • Provides water to keep cells turgid for photosynthesis • Keeps leaves cool (water evaporates)
66
How is the flow of water continuous
Due to the cohesion of water it creates a continuous unbroken column
67
Factors that affect the rate of transpiration
• Temperature • Light intensity • Air movement • Humidity
68
How does temperature affect transpiration?
• A higher temperature increases kinetic energy of water molecules • This makes transpiration through evaporation faster
69
How does light intensity affect transpiration?
• 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
70
How does air movement affect transpiration?
• Moving air removes water vapour in the air and increases the concentration gradient • Allows evaporation to happen faster
71
How does humidity affect transpiration?
• A lot of water vapour in the air reduces the water concentration gradient • This decreases the rate of evaporation
72
Potometer meaning
Apparatus used to measure the rate of transpiration
73
Why is the shoot (upper part of plant) cut under water?
To prevent air entering the xylem
74
Why are the leaves of the shoot dried?
To remove any excess water
75
Equation to work out the rate of transpiration
Rate = Distance moved by air bubble (m) / Time (min)
76
How can we reduce leaking in a potometer?
Assemble equipment underwater
77
Source meaning
Where the products are made
78
Sink meaning
Where the products are stored/ used
79
Phototropism meaning
Response to light in a directional movement
80
Geotropism meaning
Response to gravity in a directional movement
81
What tropic responses do shoots have?
Shoots have a positive phototropism and a negative geotropism
82
What tropic responses do roots have?
Roots have a negative phototropism and a positive geotropism
83
What are auxins?
Growth regulators synthesised in the tips of shoots and roots
84
How is phototropism controlled in plant shoots?
• It is controlled by auxins
• Auxins diffuse to the shaded side of shoot
• Therefore cells in the shaded side elongate
• Causing the shoot to bend towards the light
85
What are auxins similar to?
Hormones
86
How are auxins distributed in geotropism?
• (Auxins are synthesised in the tips of roots)
• Auxins diffuse to the lower side of root
• This inhibits cell elongation
• Causing the cells at the top of the root to elongate at a faster rate (in response to gravity)
87
What are plant hormones used by farmers for?
To obtain larger yields
88
What are three plant hormones?
Auxins, ethenes and gibberellins
89
How are auxins used commercially?
• Selective weed killers to maximise yield
• Sold as rooting powders for rapid development of roots
90
What is the commercial use of ethene?
It controls the ripening of fruit
91
How are gibberellins used commercially?
• They end seed dormancy/promote seed germination
• Produce seedless fruit
• Increase fruit size
92
Seed dormancy definition
When seeds are unable to germinate even under ideal growing conditions
93
Concentration gradient meaning
A difference between two concentrations
94
Dependent variable meaning
The variable you measure
95
Independent variable meaning
The variable you change
96
The rate of photosynthesis is directly proportional to what?
Light intensity
97
[SB8]
What substances are exchanged in and out of organisms?
• Oxygen
• Carbon dioxide (waste)
• Water
• Dissolved food molecules (eg glucose)
• Mineral ions
• Urea (waste)
98
What are the transport processes?
• Diffusion
• Osmosis
• Active transport
99
Why do multi cellular organisms need exchange surfaces?
• 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
100
How is villi adapted for absorption?
• It’s the folded membrane of small intestines
• This increases SA and absorption rate of digested food
101
Transport system in animals
• The blood and circulatory system
102
Exchange surfaces in animals
• Lungs and alveoli for gas exchange
• Small intestines and villi for absorption of digested food
103
Transport systems in plants
• Xylem (moves water and mineral ions from roots to shoots)
• Phloem (moves sugars and amino acids to where necessary)
104
Exchange surfaces in plants
• Roots and hairs (mineral ions and water are absorbed)
• Leaves (stomata - gas exchange)
105
Factors affecting the rate of diffusion
• Surface area
• Concentration gradient
• Diffusion distance
• Temperature
106
How does surface area affect the rate of diffusion?
• The bigger a cell the smaller its surface area to volume ratio
• This slows down the rate of diffusion
107
How does diffusion distance affect the rate of diffusion?
• 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
108
How does the concentration gradient affect the rate of diffusion?
• The greater the difference in concentration the faster the movement
• Therefore more random collisions will occur against the membrane
109
How does temperature affect the diffusion rate?
• 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
110
What is Fick’s law?
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)
111
Organelle where exchange of substances occur
Cell membrane
112
What type of reaction is respiration?
An exothermic reaction
113
Products formed when lipids are digested
Fatty acids and glycerol
114
Why do organisms need energy?
• 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)
115
Definition of aerobic respiration
The chemical reaction in cells that uses oxygen to completely break down nutrient molecules to release energy
116
Aerobic respiration word equation
Glucose + Oxygen —> Carbon dioxide + Water
117
Where does aerobic respiration occur in a cell?
Mitochondria
118
Products in respiration
• Carbon dioxide
• Water
• Useful energy
119
Anaerobic respiration definition
Chemical reaction in cells that partially breaks down nutrient molecules to release energy without using oxygen
120
Differences between aerobic and anaerobic respiration
• Aerobic respiration requires oxygen whilst anaerobic doesn’t
• Glucose is only completely broken down aerobically
• Aerobic respiration releases larger amounts of energy
121
Chemical equation for aerobic respiration
C6H12O6 + 6O2 —> 6CO2 + 6H2O
(+ energy/ATP)
122
What is ATP?
• Short term energy store in all cells
• Universal energy carrier
123
Where does anaerobic respiration take place?
Muscle cells during vigorous exercise
124
Why do our bodies use anaerobic respiration?
• 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
125
Word equation for anaerobic respiration in animals
Glucose —> Lactic acid
126
Effect of lactic acid buildup
It lowers the pH of the muscle tissue as it makes the blood more acidic
127
Oxygen debt
The amount of oxygen required to break down the lactic acid that has built up
128
Which organisms other than animals respire anaerobically?
• Plants
• Yeast (fungi)
129
What is fermentation?
Anaerobic respiration in yeast cells
130
What is the economic importance of fermentation?
• It’s used in the manufacturing of bread
(CO2 helps the dough to rise)
• It’s used in brewing
(ethanol produced makes beer)
131
Word equation for anaerobic respiration in plants and fungi
Glucose —> Alcohol + Carbon dioxide
132
How is iodine used to test for starch?
It changes its colour to blue/black
133
Purpose of soda lime in the rate of respiration practical
It absorbs any co2 to prevent it affecting the measuring of oxygen
134
Purpose of cotton wool in the rate of respiration practical
It protects us and the organisms used from the soda lime because it’s harmful
135
Purpose of inserting a bung with the capillary tube
• Allows us to accurately measure how much oxygen is used up
• No air is lost/gained from surrounding area
136
Purpose of setting up a control tube
The tube will have no organisms in it to ensure results are only due to respiration
137
Why do we time for 5 minutes after marking the position of the coloured liquid?
• Time is the control variable and prevents results from being affected
138
Why do we measure the distance the liquid has travelled in the rate of respiration practical?
• It is the dependent variable
• It allows us to see how much oxygen has been consumed
139
Why do we repeat the rate of respiration practical at different temperatures?
• Independent variable
• Range of temperatures would help identify the effect it has on respiration
140
What are the 4 blood components?
• Red blood cells
• White blood cells
• Plasma
• Platelets
141
What are the 3 types of blood vessels?
• Arteries
• Veins
• Capillaries
142
What is a eukaryotic cell?
A cell that contains genetic information within a nucleus
143
Adaptations of the alveoli
• 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
144
What does ventilation and a good blood supply do for alveoli?
It maintains the concentration gradient
145
What is blood?
The liquid that transports important substances around the body
(eg oxygen and glucose)
146
Functions of the blood
• Helps defend the body against pathogens
• Helps control body temperature
• Helps to maintain the pH of cells
147
Function of plasma
• Carries red and white blood cells and platelets
• Carries dissolved substances eg glucose and oxygen
148
What colour is plasma?
Yellow
149
Why is the blood red?
Due to the haemoglobin in red blood cells
150
What is haemoglobin?
The pigment in red blood cells that binds to oxygen and transports it
151
Function of red blood cells
They carry oxygen from the air in our lungs to our respiring cells
152
Function of white blood cells
• Form part of the immune system (fights against infection)
• Lymphocytes produce antibodies
• Phagocytes engulf and digest pathogens
153
What are platelets?
Small fragments of cells without a nucleus and are involved in the clotting of blood
154
Function of platelets
• 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 prevents microorganisms from entering
155
Adaptations of red blood cells
• Have a biconcave disc shape, to increase surface area, so more oxygen can be carried
• Have no nucleus which allows more space for haemoglobin
• Are packed with haemoglobin which binds to O2
(• Haemoglobin contains an atom of iron which gives the pigment its red colour (is brightest when lots of oxygen is bound to it))
156
Anaemia meaning
Not having enough red blood cells in the body
157
Sickle cell anemia
• 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
158
Impacts of having sickle cell anaemia
• Sufferers get breathless quickly and are often tired
• Less able to do exercise as muscles get tired quickly
159
Function of the arteries
• They carry oxygenated blood away from the heart and to the body
• Blood is under a high pressure
160
Adaptations of the arteries
• 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
161
Function of the veins
• They carry deoxygenated blood away from organs towards the heart
• Blood is carried under low pressure
162
Adaptations of the veins
• 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
163
How are the veins assisted with blood flow?
Muscles in the legs and arms help to push blood along the veins when moving
164
Function of the capillaries
They connect arteries and veins
165
Adaptations of the capillaries
• They have 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
166
How many chambers does the heart have and where are they found?
• 4
• Two upper chambers - left and right atrium
• Two lower chambers - left and right ventricles
167
What type of blood does the left side of heart carry?
Oxygenated blood
168
What type of blood does the right side of heart carry?
Deoxygenated blood
169
Function of the heart
Pumps blood around our body
170
Adaptations of the heart
• 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
171
What is the coronary artery?
The blood vessel that supplies the heart with oxygen
172
What is the vena cava?
A vein that brings deoxygenated blood back to the heart
173
Describe the flow of deoxygenated blood through the heart (1)
• 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
174
Describe the flow of oxygenated blood through the heart (2)
• 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**
175
Cardiac output definition
The volume of blood that is pumped by the heart per unit time
176
What impact does being fitter have on cardiac output?
• Fitter people have higher stroke volumes due to having thicker and stronger ventricular muscles in the heart
• So more blood is pumped per beat
177
Heart rate meaning
The number of times a heart beats per minute
178
Stroke volume meaning
The volume of blood pumped out of the the left ventricle during one cardiac cycle
179
Calculation for cardiac output (cm³min-¹)
Heart rate (bpm) x Stroke volume (cm³)
180
What is the aorta?
Artery that transports oxygenated blood from the heart to the rest of the body
181
Tropism meaning
A plant’s response to stimulus
182
[[SB9]]
What is a population?
The number of individuals of a species in an area
183
What is a community?
The number of individuals of all species in an area
184
What is an ecosystem?
All the living organisms and the non-living components in an area
185
Biotic factor definition and examples
A living factor that affects an ecosystem
Eg:
• Predation
• Competition
• Disease
186
Abiotic factors definition and examples
A non-living factor that affects an ecosystem
Eg;
• soil pH and mineral content
• light intensity
• co2 levels for plants
• moisture levels
187
Interdependence meaning
When species rely on each other for survival
188
Resources plants and animals could compete for
• Food
• Space
• Water
• Mates
• Pollination
189
How could you improve an investigation?
• Use smaller intervals
Repeating experiment to:
• Calculate a mean
• Collect more data
• Identify anomalies
190
Examples of interactions that create interdependence in a community
• Parasitism
• Mutualism
191
What is mutualism?
A relationship between two species where both benefit
192
What is parasitism?
A relationship between two species where the parasite benefits but the host is harmed
193
Example of parasitism
Fleas live on the host and feed on the host’s blood
194
Examples of mutualism
• 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
195
Biodiversity meaning
The range and variety of different species in an area
196
Importance of biodiversity
High biodiversity ensures the stability of ecosystems and reduces the dependence on one species for:
• Food
• Shelter
• Maintenance of the physical environment
197
Methods of assessing abundance and distribution of organisms
• Quadrats
• Belt transects
198
Abundance meaning
The number of individuals of a species
199
Distribution meaning
How a species is spread through out an ecosystem
200
What is a quadrat?
A square frame used to collect samples and measure biodiversity
201
What is a belt transect?
A straight line that runs parallel with a suspected change in factor along which samples are taken
202
Formula for estimating the abundance of a species in an ecosystem
Total number of organisms in all quadrats x (total area sampled / area of quadrat)
203
How can we make samples more representative of an ecosystem?
• Increase the number of samples
• Use a random sampling method
204
Random sampling meaning
Collecting samples in an unbiased way
205
What are quadrats used to estimate?
The abundance of a species in an ecosystem (using random sampling)
206
How do we use a quadrat?
• 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
• Count number of plant species
207
What are belt transects used to estimate?
The distribution of a species in an ecosystem (using systematic sampling)
208
How do we use a belt transect?
• Place quadrats at regular intervals along the tape measure
• Use tape measure to measure along the transect
• Measure the [abiotic factor] at each point
• Measure the [species] along the transect
209
When plotting a graph, which variables goes on the x and y axis?
x-axis: Independent variable
y-axis: Dependent variable
210
What are the dependent, independent and control variables in the quadrats and transects practical?
Dependent variable: The abundance
Independent variable: Abiotic factor
Control variable: Quadrat (placed at top left corner)
211
Trophic levels meaning
The feeding relationships between organisms
212
Food chain meaning
Shows the transfer of energy from one organism to the next
213
What is energy stored as at each trophic level in a food chain/web?
Biomass
214
Maximum number of trophic levels in a food chain/web
Between 4 and 5
215
Why is the efficiency of energy transfer between trophic levels low?
Energy is lost as it gets transferred
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
216
What is a pyramid of biomass?
Shows how much mass the creatures at each level have without the water in them (dry mass)
217
Roughly what percentage of energy of each trophic level is passed on to the next?
10%
218
Characteristics and importance of nitrogen
• Needed to make proteins and DNA in plants and animals
• Is an unreactive gas
• Makes up about 78% of atmosphere
219
Describe the process of the nitrogen cycle (6)
• 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
• Nitrifying bacteria converts ammonium ions into nitrites which are then converted into nitrates
• Denitrifying bacteria converts these nitrates into nitrogen gas during respiration into the atmosphere
220
How does lightning contribute to the nitrogen cycle?
• It can split the bond between the 2 nitrogen atoms
• This turns them into nitrous oxides
• Forms a part of the nitrogen fixing process
221
Crop rotation meaning
• When different types of crops are grown in the same area in a cycle to improve soil health
• Usually includes nitrogen fixing crops
222
How is the haber process involved with the nitrogen cycle?
• 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
223
What are the 4 processes in the nitrogen cycle?
• Nitrogen fixation
• Ammonification
• Nitrification
• Denitrification
224
Characteristics and importance of carbon
• 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
225
Describe the carbon cycle (6)
• 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
226
Describe the water cycle
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
227
Why is water filtered?
To make it safe for human consumption, or potable, because it can contain substances harmful to health
228
Biomass definition
Mass of living organisms
229
Why do pyramids of biomass have a pyramid shape?
The mass of organisms decrease as you go up a food chain
230
In what form does energy enter a food chain/web?
As light (used by producers)
231
Formula for efficiency of biomass transfer
Biomass in higher trophic level
__________________________________ x 100
Biomass in lower trophic level
232
What factors affect the rate of decomposition?
• Temperature
• Water
• Availability of oxygen
233
Decomposition meaning
The breaking down and digestion of biological material (waste and dead organisms) by decomposers
234
Why is decomposition important?
It ensures that materials like carbon and mineral ions are recycled and returned to the environment
235
How does temperature affect rate of decomposition?
• 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
236
How does water affect rate of decay?
• As water availability decreases so does the rate of decomposition
• Decomposers require water to survive
237
How does oxygen levels affect rate of decomposition?
Higher oxygen levels mean that decomposers respire more aerobically which gives them more energy to grow and decompose faster
238
What is compost?
A mixture of decayed organic material
239
What can compost be used as?
A natural fertiliser
240
How can we slow down the rate of decomposition?
• Low temperatures eg a fridge slow down the rate of enzyme activity and the reproduction of microorganisms
• Sealed food eg vacuum packed food have no oxygen which is needed for respiration so microorganisms die
• Using dried foods mean they lack the water needed by microorganisms for survival therefore they won’t be able to grow on it
241
What 2 types of organisms carry out decomposition?
• Detritivores
• Decomposers
242
What are detritivores?
Organisms that break down organic matter into small pieces
243
What are decomposers?
Microorganisms that feed on dead organisms
244
Examples of detritivores
• Maggots
• Worms
• Beetles
245
Examples of decomposers
• Bacteria
• Fungi
246
Formula for rate of decomposition
change in mass
________________
time taken
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Why is sea water not suitable for drinking?
It contains excess mineral ions (salts) which can lead to dehydration
248
Desalination meaning
Removing the excess mineral ions from the water to make it drinkable
249
What are 2 ways of achieving desalination?
• Distillation
• Reverse osmosis
250
What happens during distillation in desalination?
• Saline water is boiled
• The water vapour is funnelled through a tube
• The water vapour is condensed
• Pure water is collected
251
What happens during reverse osmosis in desalination?
• Saline water is forced at high pressure through a partially permeable membrane
• This filters out the mineral ions leaving pure water behind
252
What are indicator species?
Organisms whose presence indicates the presence or absence of certain types of pollution
253
What are the indicator species for water pollution?
• Bloodworms and sludgeworms (high levels of water pollution)
• Freshwater shrimps and stoneflies (clean water)
254
What are the indicator species for air pollution?
• 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)
255
What are lichens?
• Organisms that grow in exposed places such as rocks or tree bark
• Indicators of different levels of air pollution
256
What does water pollution consist of?
• 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
257
What does air pollution consist of?
• Sulfur and nitrous dioxide being released into the atmosphere
• Fossil fuel is burnt
258
What is the advantage of using indicator species?
They’re cost effective
259
What are the disadvantages of using indicator species?
• Can’t give accurate quantitative figures for pollution levels
• Can be hard to see
• Specialists are required
260
What happens during eutrophication?
• Leaching causes a build up of nitrates in water
• (So an algae bloom tends to occur) (nitrate indicator)
• Light becomes blocked by algae so plants in the water die as they can’t photosynthesise
• Microorganisms decomposing the plants respire, removing O2 from water
• Other respiring organisms eg fish die so biodiversity is reduced
261
How can the level of water and air pollution be assessed using living organisms?
[might come soon]
262
Why do farmers use plants like beans/peas for crop rotation?
• Increases nitrate levels in soil
• Because nitrogen fixing bacteria live on root nodules of peas/beans
• This converts nitrogen into ammonia and then into nitrates
263
[Topic 7]
What chemical do endocrine glands release?
Hormones
264
How are hormones transported around the body?
Dissolved in blood plasma
265
What are the 6 main endocrine glands?
• 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)
266
Function of glucagon
Controls blood glucose concentration
267
Target organ for glucagon
Liver/muscles
268
Effect of adrenalin on liver cells during excersise
• Glycogen is broken down into glucose
• Glucose is released by the liver
• Ensures a higher blood glucose concentration for increased respiration
269
How does the release of adrenaline result in improved performance of an athlete?
• 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
270
What does adrenaline do to blood vessels and why?
• It dilates (widens) vessels to allow more blood and glucose to be circulated
• Increases rate of aerobic respiration
271
What enzyme breaks down starch?
Amylase
272
What does the release of thyroxine regulate?
The metabolism rate
273
What does LH mean?
Luteinising hormone
274
What does FSH mean?
Follicle stimulating hormone
275
What are the 2 hormones that keep thyroxine concentration stable?
• TRH (Thyrotropin releasing hormone)
• TSH (Thyroid stimulating hormone)
276
Describe process of negative feedback if thyroxine concentration is high
• High thyroxine levels inhibits the hypothalamus from releasing TRH
• This inhibits the pituitary gland from releasing TSH
• This inhibits the thyroid gland from releasing thyroxine
• (Opposite for low thyroxine concentration)
277
How does an underactive thyroid gland contribute to an increased body mass?
• 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
278
How do hormones control the menstrual cycle?
• 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
279
What happens if the egg is not fertilised by the end of the menstrual cycle?
• The corpus luteum breaks down
• The uterus lining breaks
• Progesterone levels drop
• This causes menstruation (period)
280
What day does ovulation occur?
Day 14
281
Control meaning
Point of comparison in an experiment
282
What 2 hormones act as contraceptives and why?
• Oestrogen - inhibits FSH release from pituitary gland, preventing egg development in follicle
• Progesterone - inhibits FSH and LH, preventing egg from being released, so no egg gets fertilised
(it also stimulates production of thick cervical mucus, preventing sperm entry)
283
How do barrier methods eg condoms prevent pregnancy
• It’s stops the sperm and egg meeting
• So there’ll be no fertilisation
284
Disadvantages of using chemical contraceptive eg combined pill
• Doesn’t prevent STDs
• Still a chance of pregnancy
285
Importance of controlling internal temperature of body
• Optimum of 37°C
• Is required for enzyme activity
286
What is an um?
A micrometer
287
What is a micrometer?
10 ^-6 meters
288
What is a nanometer?
10 ^-9 metres
289
What’s a picometer?
10 ^-12 metres
290
Test for fats
• Add ethanol to food sample
• Shake and pour solution into water
• If emulsion turns milky, test is positive
291
Test for reducing sugars eg glucose
• Add Benedict's reagent to food sample and leave in water bath
• Colour changes from blue to green/yellow/ brick red
292
Test for starch
• Add iodine to food sample and mix
• Colour should change from browny orange to blue black
293
(Biuret) test for protein
• Add biuret reagent to sample
• Colour changes from blue to purple
294
What does amylase do?
Breaks down starch into simple sugars eg glucose
295
What does protease do?
Breaks down proteins into amino acids
296
What does lipase do?
Breaks down lipids (fats) into fatty acids and glycerol
297
What do we to the specimen in microscope practical?
We add a drop of water to specimen to ensure cells don't dry out
298
How can we ensure the image is seen clearly in microscope prac?
• Use thin layer of cells
• So light passes through
• Use a stain
• To see parts of the cell
299
How can achieve 400x magnification?
• Start with lowest objective lens
• Increase magnification to 40x objective lens
• With 10x eyepiece lens
300
How should a light microscope be used to view a specimen?
• Place slide on stage and look through eyepiece lens
• Turn focusing wheel to obtain clear image
301
How is calorimetry carried out?
• Weigh food sample
• Fix food sample onto mounted needle
• Pour volume of water into test tube and record it
• **Measure temperature of water at the start
• Set food on fire and hold it closely under tube
• Calculate increase in temperature to measure energy content**
302
Adaptations of sperm cell
• A long flexible tail allows it to swim
• Large number of mitochondria releases energy
• Acrosome in the head to digest egg cell membrane
303
Adaptations of egg cell
• Cell's membrane changes after fertilisation to prevent more sperm entering
• Cytoplasm contains nutrients which will feed developing embryo
304
Adaptations of ciliated epithelial cells
• Cilia beat from side to side to waft mucus
• (The mucus then traps bacteria and dust preventing damage to lungs)
305
Effect of denatured enzyme
• Active site of enzyme has changed
• So substrate will not bind with active site
• No enzyme substrate complex is formed
306
What colour does hydrocarbon indicator turn during the lack of co2?
Turns from red to purple
307
Why must potato strips be dried in osmosis prac?
To get accurate reading of mass
308
Name each factor and how they affect enzyme activity
**Temperature:**
• Optimum temp for humans is 37°C
• Over 37°C changes shape of active site
• So enzyme becomes denatured
• Rate of reaction decreases
**pH:**
• If pH is too high or too low, enzymes get denatured and shape of active site changes
• So rate of reaction decreases
**Substrate concentration:**
• Higher concentrations mean faster reactions
• Due to more collisions
• Until all the enzymes are used
309
Prokaryotes characteristics
• No nucleus
• No membrane bound organelles
• Tend to have chromosomal and plasmid DNA
310
Light intensity practical: Instead of counting number of bubbles produced, what’s a better alternative?
• Use a gas syringe
• Measure the volume of gas produced
311
Devise a plan to investigate effect of light intensity on photosynthesis rate
• Put light source at a distance away from pondweed/algae balls
• Use a light meter to measure light intensity
• Use a heat shield to absorb any heat from light source
• Add sodium hydrogen carbonate to the water
• Count the number of bubbles in a set time
• Repeat with light at different distances
312
What is a control for the rate of respiration practical?
Repeating using glass beads instead of living organisms
313
What’s the advantage of using an electron microscope?
• Higher magnification can be used
• So the *specimen* is more visible
• And the sub-cellular structures are visible
314
How do non-indigenous species reduce biodiversity eg water plants?
• Because conditions are suitable for growth,
• They outcompete the natural plants
• Therefore they reproduce
315
How is starch broken into glucose?
Amylase breaks the bonds as starch fits into active site
316
Advantage of mashing food before adding enzyme
• It increases surface area
• So enzyme will break it down more
317
How do plant hormones work as weed killers?
Auxins only act on the weeds, causing them to overgrow and die, reducing competition for resources
318
How can fish farming reduce biodiversity?
• Waste from the nets can enter water and cause eutrophication
• Parasites can escape from the farm and infect animals, killing then
319
Benefits of reforestation and animal conservation
**Reforestation:**
• Reforestation is the planting of trees
• The rate of photosynthesis increases
• CO2 is removed from atmosphere
• Reducing greenhouse gases
**Animal conservation:**
• Involves preventing extinction
• Through maintaining habitats, improving biodiversity
• While generating income through ecotourism
320
How does an increase in animal consumption eg meat, reduce future food security?
• There’ll be less food for people to eat
• As meat farming no longer produces as much food
• Meaning more land gets used for meat farming
• And less food gets grown for humans
321
How do pathogens affect food security?
They decrease food security by reducing variety of food as crops can no longer grow
322
How can environmental change caused by human activity reduce food security?
Soil pollution can reduce crop growth
323
Advantages and disadvantages of biofuel production
**Pros:**
• It’s carbon neutral so no greenhouse gases are released
• Provides jobs so more can be spent in economy
• Reduces transport of other fuels so pollution is reduced
**Cons:**
• Machinery used may release pollution
• Deforestation reduces biodiversity levels
• High water demand for irrigation saves less water for drinking
324
How do enzymes work?
They are specific, having a shape complementary to their substrate, so that the substrate fits into the active site, and a reaction can take place
