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A Biology IGCSE course > Human influences > Flashcards

Human influences Flashcards

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1
Q

What are the main limiting factors of photosynthesis?

A
  • Light intensity
  • Carbon dioxide
  • temperature
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2
Q

What is an alternative to greenhouses and why is it more used

A

Polytunnels as they are cheaper and can be used on a massive scale

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3
Q

What are the different factors that can be controlled in a greenhouse?

A
  • Temperature
  • Light
  • Carbon dioxide
  • Water
  • Pests
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4
Q

How is temperature controlled in a greenhouse?

A
  • Paraffin heater which releases heat through combustion
  • Clear glass which allows greenhouse effect to happen within the greenhouse.
  • whitewash which can be used if it is too hot during the summer to block some of the sunlight
  • Removable netting
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5
Q

How can light be controlled in a greenhouse?

A
  • Clear glass
  • removable netting
  • electric lighting
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6
Q

How can carbon dioxide be controlled in a greenhouse?

A

There is a paraffin heater to increase the levels of carbon dioxide, which produces carbon dioxide by combusting.

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7
Q

How can water be controlled in a greenhouse?

A

This can be controlled through the automatic watering system which waters plants. There is also gravel under the plants to allow drainage out of the pots

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8
Q

How can pests be controlled in a greenhouse?

A
  • Pesticides
  • Biological control
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9
Q

Why do some plants need to be carnivorous?

A

Because if the soil under them does not contain many minerals, they consume other animals to get their minerals and nitrates

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10
Q

What are the essential minerals needed by plants?

A
  • Nitrate
  • Magnesium
  • Potassium
  • Phosphorus
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11
Q

How are most minerals acquired by plants?

A

By active transport form an area of low concentration to high in the root hair cells

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12
Q

How do plants use nitrates?

Include symptomps

A
  • NO3 is used to make amino-acids for proteins.
    Without it, plants have:
  • yellow leaves
  • reduced chlorophyll levels
  • weak root systems
  • low fruiting
  • low protein and starch content.
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13
Q

What is the use of Phosphorus in the plant?

A

This is used to form DNA and RNA, building, regulating protein synthesis, used in growth of new tissue, needed for root systems, this helps convert the sun’s energy.
Symptoms without:
Purple leaves, poor root development, stunted growth

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14
Q

What is the use of Magnesium in the plant?

symptomps as well

A

Making chlorophyll
Symptoms without:
Yellow areas in leaves, reduced fruit yields, death of plant tissue, no chlorophyll produced

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15
Q

What happens if plant roots are waterlogged?

A

the plant will respire anaerobically as there is less oxygen in the soil. This will release less energy. Therefore, there will be less active transport of mineral ions into the plant, which will reduce growth.

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16
Q

What are crop pests?

A

Pests that decrease crop yield by eating or damaging the plants/fruit

17
Q

What are pesticides, and what are the different types?

A

Pesticides are chemicals used to kill crop pests. These include:
* Herbicides - chemicals that kill weeds or unwanted plants
* Insecticides - These kill insects
* Fungicides - These kill fungi
* Molluscicides - These kill molluscs e.g. snails and slugs

18
Q

What are the problems with pesticides?

A
  • Development of resistance
  • Death to non-target(maybe useful) species
  • Some persist in the soil and can be accumulated along food chains and harm usfeul animals (bioaccumulation)
19
Q

What are the two main ways of controlling pest species?

A
  • Pesticides
  • Biological control
20
Q

How does biological control work?

A

Biological control uses a natural predator to reduce pest population.

21
Q

What are potential problems with biological control?

A

Animals do not belong there and turns out badly. This can happen if:
Species is invasive
Species targets non-pest species
increased competition leads to non-pest species dying
Species may migrate

22
Q

Advantages of biological control compared to pesticides

A
  • animals cannot develop resistance/immunity to being eaten
  • does not need to be reapplied continuoslly
  • does not lead to bioaccumulation
23
Q

What is eutrophication

(model answer, rainwater)

A
  1. Mineral ions e.g. nitrates from fertiliser are leached into rivers by rainwater
  2. Leads to an algal bloom
  3. This blocks light to plants under the surface which die
  4. dead plants are decomposed by bacteria
  5. bacteria multiply
  6. bacteria respire and use up oxygen
  7. fish die as not enough oxygen for aerboic respiration
24
Q

What is eutrophication

(model answer, sewage)

A
  1. Organic waste provides food for bacteria as they decompose it
  2. This allows them to grow and reproduce
  3. Bacteria use up the oxygen in the water when they respire aerobically
  4. There is less oxygen for fish which leads to anaerboic respiration
  5. Fish die
25
Q

What is BOD

A

Biological oxygen demand is the amount of oxygen being used by bacteria in water, which can be measured by an oxygen meter.
Low - clean water, with large selection of fish
High - polluted water, with only species like sludge and blood worms

26
Q

Why are fish stocks in oceans decreasing?

A
  • Overfishing
  • Higher human population leading to higher demand
  • Too high efficiency - trawling wipes ocean floor and wasts a lot of unnecessary fish, with sonar to locate fish, sophisticated net designs and boats capable of long-distance
27
Q

What is fish farming?

A

When fish are grown and are kept in nets or cages so that the conditions can be controlled. Furthermore, as the fish cannot move that much it means that they are using less kinetic energy to grow faster

28
Q

What is a disadvantage to keeping the fish huddled together?

A

water quality would be bad
waste produced would lead to eutrophication
If there is a disease, it will spread to all the fish

29
Q

Why is removing leftover food better?

A

By feeding little and often, it means that less food is wasted so that less is digested by other fish or bacteria.

30
Q

What is the advantage of keeping the size of the fish the same?

A
  • They can easily be caught and collected at the same time at once, making the selection process easy.
  • reduces intraspecific competition, as otherwise the large fish could take all the food and potentially eat the smaller fish
31
Q

How can the impacts of disease be reduced?

A
  • Biological control
  • anti-biotics
31
Q

What is pollution?

A

the release of environmentally damaging substances.

32
Q

What are some names of:

Air polluants

A
  • carbon monoxide
  • carbon dioxide
  • sulphur dioxide
  • nitrogen oxide
  • water vapour
  • methane
  • CFCs
33
Q

Where do polluants come from?

A

CFCs - fridges
Methane - cows
rest - fossil fuels combusting

34
Q

What is the formation of:

Acid rain

A
  1. Sulphur impurities in fossil fuels
  2. Sulphur dioxide released when these are burnt
  3. Dissolves in water vapour of clouds to form sulphuric acid
  4. Lowers pH of rain

H2CO3, carbonic acid, lowers the pH of rainwater but is not acid rain

35
Q

What are the effects of:

Acid rain

A
  • Death of aquatic life due to low pH which denatures enymes
  • Trees die as they lose leaves meaning they cannot photosynthesise. Root systems are also damaged which decreases tree growth
36
Q

What are impacts of the enhanced greenhouse effect?

A
  • Icecaps melt
  • Antarctica melting can lead to species going extinct, which can affect a whole food web
  • Habitat loss
  • migration of species
  • global sea level rising as icecaps melting which can plung islands below sea level
  • extreme weather
  • human health scares as biomes will shift as temperature rises. e.g. malaria will be more common in europe
  • Extreme droughts

A Biology IGCSE course (16 decks)

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