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IGCSE Biology > Topic 7 > Flashcards

Topic 7 Flashcards

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1
Q

What is the sun?

A

The principal source of
energy input to biological systems

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2
Q

How does energy flow through living organisms?

A
  • Light energy from sun and chemical energy in organisms
  • Energy is eventually transferred to the environment e.g. as heat
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3
Q

What is a food chain?

A

Showing the transfer of energy from one organism to the next, beginning with a producer

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4
Q

What is a food web?

A

Network of interconnected food chains

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5
Q

What is a producer?

A

An organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis

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6
Q

What is a consumer?

A

An organism that gets its energy by feeding on other organisms

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7
Q

What 4 types of consumers are there?

A

Primary, secondary, tertiary and quaternary

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8
Q

What is a herbivore?

A

An animal that gets energy by eating plants

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9
Q

What is a carnivore?

A

An animal that gets its energy by eating other animals

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10
Q

What is a decomposer?

A

An organism that gets its energy from dead/waste organic material

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11
Q

What do pyramids of number show?

A

How many organisms we are talking about at each level of a food chain. Width of the box indicates the number of organisms at that trophic level (not always pyramid shaped)

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12
Q

What does a pyramid of biomass show?

A

How much mass the creatures at each level would have without including all the water that is in the organisms (always pyramid shaped)

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13
Q

Why are pyramids of biomass better?

A

Provide a much better idea of the quantity of the plant/animal at each level of a food chain - therefore better at representing interdependence within the food chain

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14
Q

Name all the trophic levels:

A

Producers, primary consumers, secondary consumers, tertiary consumers and quarternary consumers

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15
Q

Why is the transfer of energy from one trophic level to another is not often efficient?

A

Only the energy that is made into new cells remains with the organism to be passed on. Some of this energy does not get consumed - as energy is still stored in (roots/bones) so it does not get past on

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16
Q

How does the organism lose majority of its energy?

A
  • Making waste products (e.g. urine) that get removed from the organism
  • Movement
  • Heat
  • Undigested waste(faeces)
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17
Q

Why are food chains rarely more than 5 trophic levels?

A

Inefficient loss of energy at each trophic level.
- Huge number of prey eaten per day(not enough in the proximity)
- Not expend much energy itself hunting

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18
Q

Why is it more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants:

A

Given the energy transfer in food chains, if humans eat crops there is much more energy available to them than if they eat the cows that eat the wheat. This is because energy is lost from the cows.

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19
Q

What is in the carbon cycle? (6)

A

Photosynthesis, respiration, feeding, decomposition, formation of fossil fuels and combustion

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20
Q

Why can’t plants nor animals absorb N2 from air?

A

Gas is very stable - cannot be easily broken down

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21
Q

What is in the nitrogen cycle? (8 steps)

A

Decomposition of plant/animal protein to ammonium ions, nitrification, nitrogen fixation by lightning and bacteria, absorption of nitrate ions by plants, production of amino acids/proteins, feeding/digestion of proteins, deamination and denitrification

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22
Q

2 ways nitrogen gas in the air can be converted into a usable form?

A
  • Nitrogen fixing bacteria convert N2 gas into ammonium compounds, which can be converted to usable nitrites (can be free-living in soil or live within the root nodules of some plants)
  • Lightning can split the bond between the two N atoms, turning them into nitrous oxides like N2O and NO2 that dissolve in rainwater and leach into the soil
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23
Q

How do plants absorb nitrogen from soil?

A

In the form of nitrates - used to build proteins

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24
Q

How do animals send nitrogen back into the soil in the form of ammonium compounds?

A

Waste (urine and faeces)

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25
Q

How are dead plant/animals broken down into ammonium compounds?

A

Decay and all the proteins inside them are broken down into ammonium compounds by decomposers

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26
Q

What do nitrifying bacteria do?

A

Convert ammonium compounds to nitrites and then to nitrates

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27
Q

What do denitrifying bacteria do?

A

Take nitrates out of the soil and convert them back into N2 gas

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28
Q

Why is denitrification bad?

A

Reduces soil fertility and is bad for plant growth

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29
Q

How to reduce denitrifying bacteria?

A

They are anaerobic so aerating the soil (reduce waterlogging, turning over soil during ploughing) can reduce rate of denitrification

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30
Q

What is a population?

A

A group of organisms of one species, living in the same area, at the same time

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31
Q

What is a community?

A

All of the populations
of different species in an ecosystem

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32
Q

What is an ecosystem?

A

A unit containing the
community of organisms and their environment,
interacting together

33
Q

What are the factors affecting rate or population growth?

A
  • Food supply
  • Competition
  • Predation
  • Disease
34
Q

What is the exponential (log), stationary and death phases in the sigmoid curve of population growing in an environment show?

A

Population growing in an environment with limited resources

35
Q

What is the name of a population growth curve?

A

Sigmoid growth curve

36
Q

What is the lag phase?

A

Organisms are adapting to the environment before they are able to reproduce; in addition, at this stage there are very few organisms and so reproduction is the limiting factor

37
Q

What is the exponential (log) phase?

A

Food supply is abundant, birth rate is rapid and death rate is low; growth is exponential and only limited by the number of new individuals that can be produced

38
Q

What is the stationary phase?

A

Population levels out due to a factor in the environment, such as a nutrient, becoming limited as it is not being replenished; birth rate and death rate are equal and will remain so until either the nutrient is replenished or becomes severely limited

39
Q

What is the death phase?

A

Population decreases as death rate is now greater than birth rate; this is usually because food supply is short or metabolic wastes produced by the population have built up to toxic levels

40
Q

Why are organisms in a natural environment unlikely to show the population growth sigmoid curve?

A

Affected by many other factors:
- changing temp/light
- predation
- disease
- immigration (moving into)
- emigration (moving out)

41
Q

How have humans increased food production? 5 ways

A
  • agricultural machinery to use larger areas of land, improve efficiency
  • chemical fertilizers to improve yield
  • insecticides to improve quality and yield
  • herbicides to reduce competition with weeds
  • selective breeding to improve production by crop plants and live stock
42
Q

What is monoculture farming?

A

On a given area of agricultural land only one type of crop is grown (eg trees for palm oil grown in Indonesian rainforest)

43
Q

Disadvantages of monocultures?

A
  • decreased biodiversity (pathogens/disease)
  • increase in pest populations
  • insecticides (harmless insects killed, pollution, reduce effectiveness)
  • destroy soil nutrients
  • lead to soil erosion due to lack of established roots through soil
44
Q

Advantages of monocultures?

A
  • more efficient
  • crops can be optimized for highest quality/yield
45
Q

What is intensive livestock farming?

A

Large numbers of livestock are often kept in an area that would not normally be able to support more than a very small number

46
Q

What is biodiversity?

A

The number of different species that live in an area

47
Q

What are the reasons for habitat destruction:

A
  • increased area for housing, crop plant production and livestock production
  • extraction of natural resources
  • freshwater and marine pollution
48
Q

Undesirable effects of deforestation

A
  • reduce biodiversity
  • extinction
  • loss of soil
  • flooding
  • increase of carbon dioxide
49
Q

What is eutrophication?

A

Runoff of fertilizer (increased availability of nitrate/other ions) from farmland enters the water and causes increased growth of algae and water plants. Algal bloom (growth of producers) blocks sunlight so water plants cant photosynthesize and die out and the algae follows along with it when competition for nutrients become too intense. As water plants and algae die in greater numbers, decomposing bacteria increase in number and use up the dissolved oxygen whilst respiring aerobically (increased aerobic respiration by decomposers). As a result there is a reduction in dissolved oxygen in water, so aquatic organisms such as fish and insects may be unable to breathe and would die

50
Q

Plastic in marine habitats:

A
  • Animals often try to eat plastic or become caught in it, leading to injuries and death
  • As the plastic breaks down it can release toxins that affect marine organisms
  • Once it has broken down into very small particles, it is commonly ingested by animals and enters the food chain
51
Q

Plastic on land:

A
  • Generally disposed of by burying in landfills
  • As it breaks down, it releases toxins into the surrounding soil and as such the land is no good for growing crops or grazing animals and can only be used for building on several decades after burials
52
Q

Methane and Carbon dioxide do what?

A
  • Both gases insulate the Earth and act as a ‘blanket’ around the atmosphere
  • Higher levels of both have led to global warming and climate change
  • Human activity has increased levels of both gases in the atmosphere
53
Q

What does global warming do

A

Melts the permafrost in sub-polar regions, which results in even more trapped methane being released into the atmosphere

54
Q

What is a sustainable resource?

A

One which is
produced as rapidly as it is removed from the
environment so that it does not run out

55
Q

What resources can be conserved and managed sustainably?

A
  • Forests
  • Fish stocks
56
Q

How can forests be conserved?

A
  • Education
  • Protected areas
  • quotas
  • replanting
57
Q

How fish stocks can be conserved?

A
  • education
  • closed seasons
  • protected areas
  • controlled net types
  • mesh size
  • quotas and monitoring
58
Q

Reasons for conservation

A
  • maintaining/increasing biodiversity
  • reducing extinction
  • protecting vulnerable ecosystems
  • maintaining ecosystem functions, limited to nutrient cycling and resource provision (food, drugs, fuel and genes)
59
Q

What do humans do for organisms become endangered/extinct?

A
  • climate change, habitat destruction, hunting, overharvesting, pollution and introduced species
60
Q

How can endangered species can be conserved?

A
  • monitoring and protecting species and habitats
  • education
  • captive breeding programmes
  • seed banks
61
Q

Describe the use of artificial insemination (AI) in captive breeding

A

Allows large numbers of offspring to be produced without the need for conventional sexual intercourse between males and females

62
Q

Describe the use of vitro fertilization (IVF) in captive breeding

A

Allows gametes with known alleles to be used in ensuring the next generation remains biodiverse

63
Q

What is the risk to a species if its population size decreases

A

Reduces genetic variation - more susceptible to environmental change, less resilient (greater risk of extinction

64
Q

Why are bacteria useful in biotech and gene modification?

A

Due to their rapid
reproduction rate and their ability to make
complex molecule

65
Q

Why are bacteria useful in biotechnology and genetic modification?

A
  • few ethical concerns over manipulation and growth
  • presence of plasmids
66
Q

What is the role of anaerobic respiration in yeast during the production of ethanol for biofuels?

A

Anaerobic respiration in yeast produces ethanol and CO2

67
Q

What is the role of anaerobic respiration of yeast in bread making?

A

Respires producing carbon dioxide causing the bread to rise

68
Q

What is yeast?

A

Single celled fungus that uses sugar as its food source

69
Q

What does pectinase do?

A

Enzyme that causes more juice to be released. Breaks down a chemical called pectin that is found inside plant cell walls. Once pectin is broken down, cell walls break more easily, allowing more juice to be squeezed out of the fruit (also helps to produce a clearer juice, as pectin can make juice seem cloudy)

70
Q

What do the enzymes in biological washing powders do?

A
  • quickly breaks down large, insoluble molecules (such as fats and proteins into smaller, soluble ones that dissolve in washing water)
  • Less effective at lower temperatures
71
Q

Conditions needed to be controlled in a fermenter:

A
  • temperature
  • pH
  • oxygen
  • nutrient supply
  • waste products
72
Q

What can fermenters be used for?

A

Large scale production of useful products by bacteria/fungi
- insulin
- penicillin
- mycoprotein

73
Q

How can milk be made lactose free?

A
  • adding enzyme lactase and allow enzyme to break down lactose
74
Q

What is genetic modification?

A

Changing the genetic material of an organism by removing/changing/inserting individual genes

75
Q

Outline the process of genetic modification using bacterial production of a human protein as an example limited to:

A
  • isolation of the DNA making up the human gene using restriction enzymes, forming sticky ends
  • cutting of a bacterial plasmid DNA with the same restriction enzymes, forming complementary sticky ends
  • insertino of human DNA into bacterial plasmind DNA using DNA ligase to form a recombinant plasmid
  • insertion of recombinant plasminds into bacteria
  • multiplication of bacteria containing recombinant plasmids
  • expression in bacteria of the human gene to make the human protein
76
Q

Insertion of human genes into bacteria produce?

A

Human proteins

77
Q

Insertion of genes into crop plants to produce?

A

Herbicides

78
Q

Insertion of genes into crop plants to produce?

A

Resistance to insect pests

79
Q

The insertion of genes into crop plants to improve nutritional qualitites

A

IGCSE Biology (10 decks)

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