B4 Flashcards
1
Q
What is an ecosystem? (2 points)
A
- A physical environment with a particular set of conditions, plus all of the organisms that live in it
- Can be artificial or natural
2
Q
What do natural ecosystems have? (1 point)
A
High biodiversity (many different species of plants and animals coexist in the same environment)
3
Q
What are artificial ecosystems for? (1 point)
A
They are designed and maintained for a particular purpose so they have a lower biodiversity
4
Q
How are weedkillers, fertilisers and pesticides related to ecosystems? (1 point)
A
They may be used in artificial ecosystems to prevent other animals and plants from growing alongside a crop, which leads to low biodiversity
5
Q
What are 3 facts about forestry plantations? (3 points)
A
- Very carefully set up, controlled and monitored
- They will have less biodiversity due to the fact they havent been established for as long as natural woodland (takes years to form), and result from the relationships and interactions of the organisms that live there and their surroundings
- Fewer species are introduced at the setting up stage and not all species survive from the start
6
Q
What are 3 facts about fish farms? (3 points)
A
- Have less biodiversity due to the shorter time they have existed compared to lakes
- Plus in the absence of many predators, some fish species will thrive, whilst others not
- Also there are fewer diseases which may result in too many of certain species reducing others
7
Q
What is a habitat? (3 points)
A
- The part of the physical environment where an animal or plant lives
- The organisms living there will have adapted to their habitat, so may be restricted to living there, may only eat the food there
- In a habitat, organisms are distributed at random
8
Q
How may an animal be restricted to living in a certain habitat? (1 point)
A
The organisms living there will have adapted to their habitat, and may only eat the food there
9
Q
What is a community? (1 point)
A
The total number of individuals of all the different populations of plants and animals that live together in a habitat at any one time
10
Q
What is a population? (1 point)
A
The total number of individuals of the same species that live in a certain area
11
Q
How are ecosystems self supporting, and what do they rely on? (2 points)
A
- Self supporting in all factors (e.g. providing mates, shelter)
- Rely on an energy source (the Sun), and producers at the bottom of the food chain
12
Q
What are 4 methods of measuring the size and distribution of a population? (4 points)
A
- Pooters
- Sweepnets
- Pitfall traps
- Quadrats
13
Q
What are pooters? (1 point)
A
Containers used to collect insects easily, without harming them
14
Q
What are sweepnets? (1 point)
A
Used to collect insects in long grass or moderately dense woodland where there are lots of shrubs
15
Q
What are pitfall traps? (1 point)
A
Containers set into the ground that are used to catch small insects, e.g. beetles
16
Q
What are quadrats? (1 point)
A
Square frames that have sides usually 0.5m long, used to count a smaller, representative part of a population
17
Q
How do quadrats work? (3 points)
A
- Throw them randomly on the ground, then count and record the number of each species within the quadrate
- You can then estimate the population of each species in a given area
- Quadrat sizes can vary depending on the area studies
18
Q
When sampling, what must you make sure you do? (2 points)
A
- Take a big enough sample to make the results a good estimate; the larger the sample the more accurate the results
- Sample randomly; the more random the sample the more likely it is to be representative of the population
19
Q
What is Capture-Recapture, and what is it also known as? (2 point)
A
- A method used to estimate a population size
- Also known as the Lincoln Index
20
Q
Why can sampling populations be difficult? (1 point)
A
Species move around all the time
21
Q
Give the 5 stages of Capture-Recapture? (5 points)
A
1) A trap is used to catch a sample of individuals (e.g. mice)
2) Sample is counted, recorded and each individual is marked with a numbered tag/band or a dot of paint
3) Individuals are released unharmed back into the environment, and given time to redistribute amongst the unmarked population
4) Another sample of individuals is captured, where some are marked and some not
5) The unmarked animals are counted, recorded, marked and released
22
Q
What formula can be used to estimate the total population size in the habitat? (1 point)
A
No. in 1st sample (all marked) x no. in 2nd sample (marked/unmarked) ÷ No. in 2nd sample which were previously marked
23
Q
What must you do when you use the Capture-Recapture method? (3 points)
A
- Assume that no organisms have died, immigrated or emigrated between sampling
- Make sure that identical sampling methods are used from one visit to the next
- Make sure that marking the organisms doesn’t affect their survival (e.g. be careful when using paint on invertebrates because if too much is used it can enter their respiratory passages and kill them)
24
Q
How can a population size estimate be more accurate? (1 point)
A
A larger sample size is more accurate
25
What is a transect line? (1 point)
- Used to map the distribution of organisms
| - Used for studies of how species change across a boundary between habitats (e.g. a rocky shoreline)
26
What are the stages of using a transect line? (2 points)
1) A line like a tape measure is laid out
| 2) Quadrats are distributed in regular intervals on the line, and the species in the quadrats are counted
27
Why is the data from a transect line presented in a kite diagram? (1 point)
Counting the animals and plants in quadrats along the line of a transect gives a lot of numbers, making it difficult to see trends and compare different parts of the habitat
28
What is one thing that kite diagrams show? (1 point)
Zonation
29
What is zonation? (1 point)
The gradual change in the distribution of species across a habitat
30
What factors can result in the zonation of organisms in a habitat? (1 point)
Gradual changes in abiotic (non-living) factors, e.g. tides, water temperature, salinity of a rock pool etc
31
Where is zonation clearly seen? (1 point)
In rock shores, where there are distinct zones f organisms to due to the changing tides and the different conditions created
32
What is photosynthesis? (1 point)
Where green plants make their own food (glucose and starch), using sunlight
33
What does photosynthesis produce? (1 point)
Glucose for biomass and energy, oxygen is produced as a by-product
34
What is the equation for photosynthesis? (1 point)
carbon dioxide + water (+ light energy) → glucose + oxygen
35
How has our understanding of photosynthesis changed? (3 points)
- Greek scientists thought that plants gained mass only by taking in minerals from the soil
- Van Helmont carries out many experiments and concluded plant growth cannot be due only to the nutrients in the soil
- Joseph Priestley put a plant in a jar of air, and a plant in a jar with a mouse inside; changed the combinations of plants and mouse and concluded that oxygen is produced by plants
36
What can glucose produced in photosynthesis be used for? (2 points)
- Used immediately to produce energy through respiration
| - Can be converted into other substances that the plant needs
37
What can glucose and starch be converted into? (4 points)
- Energy (during respiration)
- Proteins for growth and repair
- Starch, fats and oils that can be stored in seeds
- Cellulose, which is needed for plant cell walls
38
What must glucose be to be transported and stored? (2 points)
- Glucose is soluble, and can be transported around the plant as soluble sugar
- In order to be stored, glucose must be converted into starch, which is insoluble
39
How is starch a very useful storage molecule? (2 points)
- It is insoluble so doesn't affect the water concentration inside the cells where its stored
- Also does not move away in solution from storage areas
40
What would happen if the cells stored soluble glucose? (1 point)
The inside of the cells would become very concentrated and water would constantly move in through osmosis, which would make the cell swell
41
Talk about the chemistry of photosynthesis? (5 points)
- Using radioactive Oxygen-18, scientists discovered that the oxygen produced as a by-product in photosynthesis comes from the water and not the carbon dioxide
- Only when oxygen-18 is introduced via the water do you get a radioactive waste product of oxygen
- This shows that photosynthesis is a two-stage process
- First stage: light energy is used to split water, releasing oxygen gas and hydrogen ions
- Second stage: the carbon dioxide gas combines with the hydrogen ions to make glucose
42
Why do plants grow faster in the summer? (1 point)
They need light and warmth to grow
43
How can photosynthesis be increased? (3 points)
- Increasing the temperature (using heaters in a greenhouse)
- Increasing light intensity (using lamps in a greenhouse)
- Increasing CO2 concentration (using chemicals or as a by-product of using gas heaters in a greenhouse)
44
Talk about increasing the temperature with regard to photosynthesis (3 points)
- As the temperature rises, so does the rate of photosynthesis
- This means temperature is the limiting factor in the rate of photosynthesis
- As the temperature approaches 45°c, the enzymes controlling photosynthesis start to be denatured and the rate of photosynthesis declines to 0
45
Talk about increasing the CO2 concentration with regard to photosynthesis (4 points)
- As the carbon dioxide concentration rises, so does the rate of photosynthesis
- So carbon dioxide is limiting the rate of photosynthesis, up to a certain point
- After this point, a rise in carbon dioxide levels has no effect
- So carbon dioxide is no longer the limiting factor; light or temperature must be
46
Talk about increasing the temperature with regard to photosynthesis (3 points)
- As the light intensity increases, so does the rate of photosynthesis
- This means light intensity is limiting the rate of photosynthesis up to a certain point
- After this point, a rise in light intensity has no effect
- Light intensity is no longer the limiting factor, carbon dioxide or temperature must be
47
How do plants break down glucose to release energy? (1 point)
They respire
48
What do plants do during the day? (1 point)
During the day, light is available from the Sun so plants photosynthesise; taking in carbon dioxide to make glucose and releasing oxygen as a by-product
49
What do plants do during the day and night? (4 points)
During the day and night, they respire, absorbing oxygen and giving out carbon dioxide
- Respiration is the reverse of photosynthesis
- Plants photosynthesise much faster than they respire when light is available
- This is why they give out oxygen during the day
50
Where does photosynthesis mainly occur in a plant? (1 point)
The leaves, which are specially adapted for efficiency
51
Give 5 ways that plants are specially adapted for photosynthesis efficiency? (5 points)
- Contains a pigment chlorophyll (which absorbs light) in millions of chloroplasts, plus other pigments: to absorb light from different parts of the spectrum
- Broad and flat: provides huge surface area to absorb sunlight
- Has a network of vascular bundles: for support and to transport water to the cells, and remove the products of photosynthesis (i.e. glucose)
- Thin structure: so gases (CO2 and O) only have a short distance to travel to and from the cells
- Has stomata (tiny pores): on the underside of the leaf to allow the exchange of gases, which are opened and closed by guard cells
52
What happens in a plant during photosynthesis? (3 points)
- Carbon dioxide diffuses in through the stomata (leaf pores)
- Oxygen diffuses out through the stomata
- Water is absorbed through the roots
53
What are a leaf's 4 distinctive layers? (4 points)
- The upper epidermis
- The palisade layer
- The spongy mesophyll
- The lower epidermis
54
How are the distinctive layers adapted for efficiency? (3 points)
- The upper epidermis is transparent to allow sunlight through to the layer below
- The cells in the palisade layer are near the top of the leaf and are packed with chloroplasts so they can absorb the maximum amount of light
- The spongy mesophyll contains lots of air spaces connected to the stomata to allow the optimum exchange of gases
55
Which factor of the leaf provides efficient gaseous exchange? (1 point)
The internal structure provides a very large surface area to volume ratio for efficient gaseous exchange
56
How do plants absorb lots of light? (2 points)
- Plants contain many chloroplasts
| - Chloroplasts are long for efficient light absorption
57
What plants cells do not contain chloroplasts? (1 point)
Chloroplasts are not found in all plant cells, e.g. in root cells as they obviously dont receive any light
58
What do a plants' chloroplasts and other pigments do? (1 point)
Absorb different wavelengths of light
59
What is chlorophyll a mixture of? (1 point)
A mixture of pigments including: chlorophyll a + b, xanthophylls and carotene
60
What do chlorophyll a + b absorb? (1 point)
They absorb different ranges of colours, but both tend to absorb colours in the red and violet ends of the spectrum
61
When lights of different colours are shone on a plant and the rate of photosynthesis is measured, where are the maximum rates obtained? (1 point)
In the red and violet ends of the spectrum
62
Why do plants tend to be green? (1 point)
Greener colours are reflected when shone on chlorophyll a + b
63
How do substances move in and out of cell membranes? (1 points)
By diffusion
64
What is diffusion? (1 point)
The movement of a substance from a region of high concentration to a region of low concentration
65
What is random movement? (1 point)
Where particles move about in lots of different directions during diffusion
66
In diffusion, what is the term for the general direction of movement of particles from an area of high concentration to low? (1 point)
Net (overall) movement
67
How is the rate of diffusion increased? (3 points)
- When there's a greater surface area of the cell membrane
- When there's a greater difference between concentrations (a steeper concentration gradient)
- When the particles have a shorter distance to travel
68
What happens with regard to diffusion during the day? (3 points)
- Carbon dioxide is used up in photosynthesis, so the concentration inside the leaves is lower than the concentration outside the leaves
- Carbon dioxide diffuses into plants through the stomata (tiny pores) on the bottom of their leaves
- Oxygen, a by-product of photosynthesis, diffuses from the plant into the atmosphere
69
What happens with regard to diffusion during the night? (3 points)
- At night, photosynthesis stops
- Oxygen diffuses into leaf cells
- Carbon dioxide diffuses out of leaf cells
70
How are the stomata on the underside of the leaves specially adapted? (2 points)
- To open: to help increase the rate of diffusion of carbon dioxide and oxygen
- To close: to prevent excessive water loss in drought conditions
71
What is osmosis? (2 points)
- The diffusion of water from high concentration (dilute solution) to low concentration of water (concentrated solution) through a partially-permeable membrane (a membrane that allows the passage of water molecules but not solute molecules)
- Special type of diffusion involving water molecules
72
What are plant cells surrounded by? (1 point)
A membrane which allows water to move in and out of the cells
73
What can move freely through the cellulose cell wall? (1 point)
Water and solute molecules
74
What is the function of the cell wall? (1 point)
To provide support - it doesn't affect the movement of substances in or out of the cell
75
In osmosis, how do the water particles move? (1 point)
Randomly, colliding with each other, and passing through the membrane in both directions
76
What is the net movement of particles in osmosis, and what does it do? (2 points)
- From the area of high water concentration to the area of low water concentration
- This gradually dilutes the solution
77
How can you predict the direction of water movement in osmosis? (2 points)
- If you know what the concentration of the water is
| - BUT, soluble molecules cannot pass through the membrane, only the water molecules can!
78
What other cells does osmosis occurs in to allow the diffusion of water? (1 point)
Animal cells
79
How could an animal cell burst? (1 point)
Animal cells dont have a cell wall, so too much water entering a cell could cause it to burst
80
Give an example of a cell that changes shape when the solutions they are in differ? (4 points)
Red blood cells
- When red blood cells are in solutions with the same concentration as their cytoplasm, they retain their shape
- When in a weaker solution, they absorb water, swell up, and may burst
- When in a more concentrated solution, they lose water and shrivel up
81
How are animal cells different to plant cells? (1 point)
They dont have an inelastic cell wall
82
Describe what happens when blood cells are in a pure water solution? (3 points)
- They will gain water by osmosis
- Without a cell wall to prevent water entering the cell, they absorb more and more water until eventually they burst
- This is called lysis
83
Describe what happens when blood cells are in a pure concentrated solution? (2 points)
- Blood cells in a concentrated solution (very little water) will lose water by osmosis
- Without a cell wall to prevent water loss, they can shrivel up and become crenated
84
What does flaccid mean? (1 point)
A plant cell that is limp
85
What does turgid mean? (1 point)
A plant cell fully inflated with water
86
What does plasmolysed mean? (1 point)
When cells lose a lot of water, the inside of the cell contracts, causing the cell membrane to pull away from the inside of the cell wall
87
What is crenation? (1 point)
The shrinking of an animal cell by osmosis
88
What is lysis? (1 point)
The bursting an animal cell by osmosis
89
What 2 things does the cell wall do? (2 points)
- Prevents cells from bursting due to excess water
| - Contributes to rigidity
90
What 2 things are essential for the support of young non-woody plants? (2 points)
- Plant cells have inelastic cell walls which, together with
| - Water inside the cells are essential for support
91
What is turgor pressure? (1 point)
The pressure of the water pushing against the cell wall
92
What does a lack of water cause plants to do? (1 point)
Droop (wilt)
93
What happens as the amount of water inside cells reduces? (1 point)
The cells become less rigid due to reduced turgor pressure
94
Explain what happens to cells as the amount of water inside fluctuates (6 points)
- As water moves into plant cells by osmosis, the pressure inside the cell increases
- The inelastic cell walls can withstand the pressure and the cell becomes very turgid
- When all the cells are fully turgid, the plant is firm and upright
- But if water is in short supply, cells will start to lose water by osmosis
- They lose turgor pressure and become flaccid, and the plant begins to wilt
- When cells lose a lot of water, the inside of the cell contracts, called plasmolysis
95
What do the xylem and phloem form? (1 point)
A continuous system of tubes from roots to leaves, called vascular bundles
96
What is the role of the xylem? (1 point)
Transports water and soluble mineral salts from the roots to the leaves (transpiration)
97
What is the role of the phloem? (1 point)
Allows the movement of food substances (sugars) around the plant (translocation), up and down stems to growing tissues and storage tissues
98
Give 3 features of the xylem vessels? (3 point)
- Made from dead plant cells
- Have a hollow lumen
- The cellulose cell walls are thickened with a waterproof substance
99
What is the structure of phloem cells? (1 point)
They are long columns of living cells
100
Why do root hairs have an enormous surface area? (1 point)
For absorbing water and so increase the plant's ability to take up water
101
What is transpiration, and what does it do for the plant? (3 points)
The diffusion and evaporation of water from inside a leaf
- It causes water to be moved up xylem vessels
- Provides plants with water for cooling, photosynthesis and support, and brings minerals to the plant
102
What is the transpiration stream powered by? (1 point)
The evaporation of water from the leaf
103
State the 4 stages that occur in the transpiration stream (4 points)
1) Water evaporates from the internal leaf cells through the stomata
2) Water passes by osmosis from the xylem vessels to leaf cells, which pull the thread of water in that vessel upwards by a very small amount
3) Water enters the xylem from root tissues, to replace water that has moved upwards
4) Water enters root hair cells by osmosis to replace water that has entered the xylem
104
What can the rate of transpiration be affected by? (4 points)
- High light intensity (which causes the stomata to open - this increases the rate of water evaporation)
- Increased air movement/wind (which blows the ager molecules away fro, the stomata - this increases transpiration)
- High temperatures (which increase the movement of the water molecules - this speeds up transpiration)
- High humidity (which decreases the concentration gradient - this slows down transpiration)
105
How can a leafy shoot's rate of transpiration be measured? (1 point)
Using a mass potometer
106
State the 4 stages of using a mass potometer to measure a leafy shoot's rate of transpiration? (4 points)
1) The plant's roots are submerged in a sealed bag of water and placed in a beaker
2) The beaker is placed on a digital balance
3) Readings are then taken to see how much water is lost by the plant during transpiration
4) The conditions (e.g. light, temperature) can be changed to see how this affects water loss
107
What do healthy plants need to do with regard to water? (1 point)
They need to balance the amount of water they take it and lose
108
What are 3 stages water uses to enter a plant, move around, and to exit? (3 points)
1) Water is absorbed by the plants by the roots hair cells, which have a large surface area to take in water
2) The water then diffuses through the plant up to the leaves
3) When it reaches the leaves it can be lost by transpiration (evaporation)
109
What are 2 adaptations that reduce the rate at which water is lost from leaves? (4 points)
- A waxy cuticle on the surface on the leaf
- Having the majority of the stomata on the lower surface of the leaf
- The number, position, size and distribution of stomata vary between plants, depending on the environment (which affects the amount of water they need)
- The turgidity of guard cells hanged in relation to the light intensity and availability of water, in order to alter the size of the stomatal openings
110
What 2 things are an unavoidable consequence of photosynthesis? (2 points)
- Transpiration
| - Water loss
111
What do the stomata do as well as being needed for the exchange of gases? (1 point)
They also allow water molecules to pass out of a leaf
112
During photosynthesis, what do the guard cells become? (1 point)
Turgid, and the stomata fully open
113
What happens if there is a lack of water in guard cells? (1 point)
The guard cells become flaccid and the stomata close to prevent unnecessary water loss and photosynthesis
114
What are essential nutrients needed for by plants, and how are they taken in? (2 points)
- Needed to keep plants healthy and growing properly
| - Plants absorb dissolved minerals in the soil through their roots
115
What are the minerals in soil like? (1 point)
Naturally present, but usually in quite low concentrations
116
Why do farmers use fertilisers, and give an example? (2 points)
The minerals naturally present are usually in low concentrations, so farmers use fertilisers containing essential minerals to make sure that plants get all the minerals they need to grow
- E.G. NPK
117
What 4 minerals are needed in plants, and give their purposes? (4 points)
- Nitrates (N): to make amino acids that form proteins for cell growth
- Potassium compounds (K): to help the enzymes in respiration and photosynthesis
- Phosphates (P): to make DNA and cell membranes for respiration and cell growth
- Magnesium: to make the chlorophyll for photosynthesis
118
What happens if one or more of the essential minerals is missing (deficient) from the soil? (1 point)
The growth of the plant will be affected
119
How can you see whether removing one mineral affects a plant? (3 points)
- Experiments can be carried out
- This is done by growing plants in a soil-less culture
- The minerals can then be carefully controlled and changed
120
What is active transport, and what does it require? (2 points)
- Substances sometimes need to be absorbed from a low to a high concentration area, i.e. against a concentration gradient, called Active Transport
- Requires energy from respiration
121
How do plants absorb mineral ions? (1 points)
Through their root hairs by active transport
122
What is decay, and what are the key factors in the process? (2 points)
- Decay is a process involving the breakdown of complex substances into simpler ones by micro-organisms
- The key factors in the process are microbes, temperature, oxygen and moisture
123
What is the rate of decay affected by? (3 points)
- Changing temperature: micro-organisms responsible for decay work slowly at low temperatures, but at high temperatures (above 40°c) their enzymes are denatured and decay stops - so they work best at around 40°c
- Amount of oxygen: increasing the amount of oxygen increases the micro-organisms' rate of respiration, which means they produce more energy, enabling them to grow and reproduce more quickly - the more oxygen there is, the faster they grow, and their rate of activity increases
- Amount of water: microorganisms grow quickest in moist conditions, too much or too little water will slow down their growth, and therefore the rate of decay
124
What are earthworms, woodlice and maggots known as? (1 point)
Detritivores
125
What do detritivores feed on? (2 points)
- Dead organisms
| - Decaying material (detritus) produced by living organisms
126
How do detritivores speed up the process of decay? (2 points)
- They speed up the process of decay by breaking down detritus into small particles which have a large surface area
- This makes it easier for decomposers (bacteria and fungi) to feed on
127
What are microorganisms used to break down? (2 points)
- Human waste in sewage treatment works
| - Plant waste in compost heaps
128
Why can materials that decay be recycled? (1 point)
Because decaying materials release minerals back into the soil, which plants use to grow
129
What are fungi? (1 point)
Saprophytes
130
What do saprophytes do? (1 point)
They feed on dead organic material by secreting enzymes onto the material and then absorbing the digested products, saprophytes are essential for decay
131
How can food be preserved? (1 point)
By removing the oxygen, warmth or moisture (water) that the microorganisms need in order to grow or survive
132
Give 5 ways that food can be preserved and reduce the rate of decay? (5 points)
- Sealed inside sterile cans (canning), this prevents the entry of decomposers
- Kept at low temperatures in a fridge or freezer, this slows down reproduction of the microorganisms growth
- Pickled in vinegar, acid kills the decomposers
- Preserved in sugar (or salt), this removes water from the decomposers by osmosis, so killing them
- Dried, this reduces the water
133
What do intensive farming methods aim to do? (2 points)
- Aim to produce as much food as possible from the available land, plants and animals
- These methods use chemicals like pesticides to kill pests that damage crops or livestock so more food is produced
134
What are 4 types of chemicals used in intensive farming? (4 points)
- Pesticides: used to kill pests (i.e. any organism that can damage crops or farm animals)
- Insecticides: (types of pesticides) used to kill insect pests
- Fungicides: (types of pesticides) used to kill fungi
- Herbicides: used to kill weeds which compete with crops for water and nutrients
135
Why does care need to be taken with pesticides? (3 points)
- They can harm other organisms (non-pests)
- They can build up (accumulate) in food chains, harming animals at the top
- Some pesticides are persistent, they stay in the food chain for years
136
How can intensive farming increase productivity? (1 point)
- By keeping animals in carefully controlled environments where their temperature is controlled and movement is very limited
- This improves the energy transfer by reducing the amount of energy lost at each stage of the food chain
137
What are 4 examples of controlled intensive farming? (4 points)
- Battery farming
- Glasshouses
- Hydroponics
- Fish farming
138
What ethical dilemma does intensive farming raise? (1 point)
Some people find it morally unacceptable because the animals have a very poor quality of life (e.g. battery farming of hens is in very small, confined spaces, and they can suffer health problems as a result)
139
By reducing energy transfer to pests, what does intensive farming do? (1 point)
It reduces the efficiency of energy transfer in food chains
140
What do organic farming methods aim to do? (1 point)
They aim to produce food without the use of chemicals, so minimising the impact on the environment (no pesticides, no artificial fertilisers)
141
What are 5 examples of organic farming? (5 points)
- Using natural fertilisers like animal manure or compost
- Growing nitrogen-fixing crops (e.g. peas or clover)
- Rotating crops to maintain soil fertility
- Avoiding chemical pesticides by weeding
- Varying seed planting times to discourage pests
142
What are the advantages of organic farming? (4 points)
- Food crops and the environment aren't contaminated with artificial fertilisers or pesticides
- Soil erosion is limited, and fertility is maintained through the use of organic fertilisers
- Biodiversity is promoted because hedgerows and other habitats are conserved
- Livestock have space to roam
143
What are the disadvantages of organic farming? (4 points)
- It's less efficient because some crops are lost to pests and diseases
- Organic fertilisers take time to rot and they don't supply a specific balance of minerals
- It is expensive
- More space is needed
144
What is hydroponics? (2 points)
- A method of growing plants without using soil
| - The plants are grown with their roots in a solution containing the minerals needed for growth
145
Where is the hydroponics method useful? (2 points)
- For greenhouses
| - In areas that have very thin or barren soil
146
Give an example of a plant that can be grown using hydroponics? (1 point)
Tomatoes can be grown hydroponically in greenhouses
147
What are the advantages of hydroponics? (2 points)
- The mineral levels added to the solution can be carefully controlled and adjusted to the type of plant
- There is a reduced risk of the plant becoming diseased
148
What are the disadvantages of hydroponics? (2 points)
- The plants have to be supported as they have no anchorage for their roots
- Expensive fertilisers are needed to supply the plant with minerals
149
What is biological control? (1 point)
Some farmers prefer to introduce a predator, instead of using a pesticide, to reduce the number of pests
150
What must be considered when biological controls are used? (1 point)
It is important to remember that when biological controls or pesticides are used to get rid of pests, the effect on the rest of the organisms in the food chain or web must be considered
151
What are the advantages of using biological control? (4 points)
- The predator selected only usually attacks the pest (i.e. it's species-specific)
- Once introduced, the predator can have an impact over many years, so repeating treatment isn't required
- The pest can't become resistant to the predator (unlike pesticides)
- No need for chemical pesticides
152
What are the disadvantages of using biological control? (4 points)
- The pest is reduced but isn't completely removed
- The predator may not eat the pest or it may even eat useful species
- The predator may reproduce out of control
- The predator may leave the area
