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IB biology > topic 4 > Flashcards

topic 4 Flashcards

1
Q

define a species

A

a group of organisms that can potentially interbreed to produce fertile offspring

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2
Q

define a population

A

a population is a group of organisms of the same species who live in the same area at the same time

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3
Q

what happens if two populations live in different areas? what are the consequences of this?

A
  • the members of the populations are reproductively isolated in separate populations and unlikely to breed with each other
  • they may therefore develop recognisable differences
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4
Q

define and describe the two methods of obtaining organic carbon compounds (eg glucose, amino acids) needed for growth and reproduction.

A
  • autotrophic (self-feeding): make their own carbon compounds from CO2 and other simple substances
  • heterotrophic (feed on others): obtain carbon compounds from other organisms
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5
Q

what is a mixotrophic organism?

A

organisms that are not solely autotrophic or heterotrophic, but can use both methods of nutrition

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6
Q

define a consumer

A

heterotrophs that feed on living organisms by ingestion

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7
Q

define a detritivore

A

heterotrophs that obtain organic nutrients from detritus by internal digestion

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8
Q

define a saprotroph

A

heterotrophs that obtain organic nutrients from dead organisms by external digestion

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9
Q

describe the method by which saprotrophs digest food externally

A

secretion of digestive enzymes onto the extracellular material and absorption of the organic products

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10
Q

how is a community formed?

A

by populations of different species living together in the same area and interacting with each other.

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11
Q

why can a population of one species never live in isolation?

A

all species are dependent on relationships with other species for their long-term survival

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12
Q

how is an ecosystem formed?

A

by the interactions of a community with the abiotic environment

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13
Q

describe the interaction of autotrophs with their abiotic environment

A

they obtain all of the elements that they need as inorganic nutrients from the abiotic environment

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14
Q

describe the interaction of heterotrophs with their abiotic environment

A

obtain the elements that they need as part of the carbon compounds in their food; obtain other elements as inorganic nutrients from the abiotic environment (eg sodium, potassium, calcium)

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15
Q

how is the supply of inorganic nutrients maintained?

A

by nutrient cycling

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16
Q

describe nutrient cycling with a flow diagram

A

reserves of an element in the abiotic environment <–> element forming part of a living organism

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17
Q

describe the process of nutrient cycling

A

organisms absorb the elements that they require as inorganic nutrients from the abiotic environment, use them and then return them to the environment with the atoms unchanged

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18
Q

describe the sustainability of ecosystems.

A

ecosystems have the potential to be sustainable over long periods of tine

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19
Q

give 3 requirements for sustainability in ecosystems

A
  • nutrient availability
  • detoxification of waste products
  • energy availability
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20
Q

when is something sustainable?

A

when is can continue indefinitely

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21
Q

what does the chi-squared test do?

A

it tests for the hypotheses:
- two species are distributed independently
- two species are associated (either positively so they tend to occur together or negatively so they tend to occur apart)

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22
Q

describe how you could conduct a chi-squared test

A
  1. construct a table of frequencies (both observed and expected)
    EXPECTED FREQUENCY = (Row total × Column total) ÷ Grand total
  2. Apply the chi-squared formula to each part of the table
  3. Add each value to give the chi squared result
  4. Determine the degree of freedom (df) (always 1 when there are 2 species)
  5. identify the p-value, which is considered significant if there is less than a 5% probability (p < 0.05) the results are attributable to chance
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23
Q

what do mesocosms do?

A

mesocosms are small experimental areas that can be set up to try and establish sustainability

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24
Q

nutrients —- —- recycled indefinitely, so

A

can be; there should not be a lack of the chemical elements on which life is based

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25
Q

energy —- —- recycled, so

A

cannot be; sustainability depends on continued energy supply to ecosystems (mostly supplied from the sun)

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26
Q

why do most ecosystems rely on sunlight?

A

it is the initial source of energy for both autotrophs (directly) and heterotrophs (indirectly)

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27
Q

give 3 groups of autotroph that carry out photosynthesis and are therefore referred to as producers

A
  • plants
  • eukaryotic algae
  • cyanobacteria
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28
Q

how is light energy converted into chemical energy in carbon compounds?

A

by photosynthesis

29
Q

how does chemical energy in carbon compounds flow through food chains? what then happens to it?

A

by means of feeding; energy released from carbon compounds by respiration is used in living organisms and converted to heat.

30
Q

what is the function of cell respiration?

A

it transfers chemical energy from carbon compounds to ATP, which can be used directly for many activities.

31
Q

what is the drawback of cell respiration?

A

not all of the energy in cell respiration is transferred to ATP. The remainder is converted to heat. Some heat is also produced when ATP is used in cell activities.

32
Q

why is heat lost from ecosystems?

A

because living organisms cannot convert heat to other forms of energy. Heat then passes from hotter to cooler bodies, so it will eventually all be lost to the abiotic environment.

33
Q

define biomass

A

the total mass of a group of organisms

34
Q

what is the effect of energy losses on an ecosystem?

A

energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels

35
Q

give 3 reasons why the energy added to biomass by each successive trophic level is less

A
  • most of the energy in food that is digested and absorbed by organisms in a trophic level is released in respiration and lost as heat- the only energy available to organisms in the next trophic level is chemical energy in carbohydrates and other compounds that have not been used in respiration.
  • the organisms in a trophic level are not usually entirely consumed by organisms in the next trophic level- the remaining energy passes to saprotrophs/detritivores instead.
  • not all parts of food ingested by the organisms in a trophic level are digested and absorbed. some material is indigestible and egested as faces.
36
Q

distinguish between energy flow in ecosystems and cycling of inorganic nutrients

A
  • there is a continuous but variable supply of energy in the form of sunlight
  • the supply of nutrients in an ecosystem is finite and limited
37
Q

why does biomass in terrestrial ecosystems diminish with energy along food chains?

A

due to loss of carbon dioxide, water and other waste products (eg urea)

38
Q

carbon fixation

A
  • autotrophs convert carbon dioxide into carbohydrates and other carbon compounds
  • this reduces CO2 concentration in the atmosphere
39
Q

carbon dioxide in solution

A
  • CO2 is soluble, so is present as a dissolved gas and hydrogen carbonate ions in aquatic habitats
  • can also combine with water to form carbonic acid (H2CO3) and then dissociate to form H+ and HCO3-
  • both dissolved CO2 and hydrogen carbonate ions are absorbed by aquatic plants/other autotrophs and used to make carbs and other C compounds
40
Q

absorption of carbon dioxide

A

autotrophs use CO2 in photosynthesis
- this reduces the concentration of CO2 inside autotrophs and sets up a concentration gradient between cells in autotrophs and the surrounding air/water, causing it to diffuse

41
Q

release of carbon dioxide from cell respiration

A

by animal cells, saprotrophs that decompose dead organic matter, and non-photosynthetic cells in producers (eg plant root cells)

42
Q

Anaerobic conditions where methanogens may be found include:

A
  • Wetlands (e.g. swamps and marshes)
  • Marine sediments (e.g. in the mud of lake beds)
  • Digestive tract of ruminant animals (e.g. cows, sheep, goats)
43
Q

3 steps of methanogenesis

A
  1. Bacteria convert organic matter into a mixture of organic acids, alcohol, hydrogen, CO2
  2. Bacteria use organic acids and alcohols to produce acetate, CO2, hydrogen
  3. Archaeans produce methane from CO2, hydrogen and acetate:

CO2 + 4H2 -> CH4 + 2H2O
CH3COOH -> CH4 + CO2

44
Q

Methanogenesis

A

Methanogens (archaean microorganisms) produce methane (CH4) as a metabolic by-product of anaerobic digestion, principally acetic acid and carbon dioxide - this then diffuses into the atmosphere

45
Q

oxidation of methane

A
  • methane is oxidised to carbon dioxide and water in the atmosphere
  • monatomic oxygen and highly reactive hydroxyl radicals are involved in this oxidation
46
Q

peat formation

A

peat forms the organic matter is not fully decomposed because of anaerobic conditions in waterlogged soils, which inhibit saprotroph activity

47
Q

partially decomposed organic matter from past geological eras was converted into

A

oil and gas in porous rocks or coal

48
Q

coal formation

A
  • deposits of peat are buried under other sediments
  • peat is compressed and heated, gradually turning into coal
49
Q

oil and natural gas formation

A
  • formed in the mud at the bottom of seas and lakes as a result of the decay of marine organisms
  • sediments (e.g. clay and mud) are deposited on top of the organic matter, creating anoxic conditions that prevent decomposition
  • partially decomposed matter is compressed and heated, causing chemical changes into crude oil and natural gas
50
Q

combustion

A

carbon dioxide is produced by the combustion of biomass and fossilised organic matter

51
Q

limestone

A
  • animals such as reef-building corals and mollusca have hard parts that are composed of calcium carbonate
  • when the animals die:
    ACID CONDITIONS: calcium carbonate dissolves away
    NEUTRAL/ALKALINE CONDITIONS: it is stable and deposits of it form on the sea bed. the result is these hard parts becoming fossilised in limestone rock
52
Q

draw a carbon cycle diagram

A
53
Q

describe the trends in atmospheric carbon dioxide

A
  • CO2 levels fluctuate annually (lower in the summer months when long days and more light increase photosynthetic rates)
  • Global CO2 trends will conform to northern hemisphere patterns as it contains more of the planet’s land mass (i.e. more trees)
  • CO2 levels are steadily increasing year on year since the industrial revolution (due to increased burning of fossil fuels)
54
Q

estimation of carbon fluxes due to processes in the carbon cycle

A

Carbon fluxes describe the rate of exchange of carbon between the various carbon sinks / reservoirs

It is not possible to directly measure the size of the carbon sinks or the fluxes between them – instead estimates are made

55
Q

what are the two most significant greenhouse gases and how are they released and removed from the atmosphere?

A

carbon dioxide:
- cell respiration in living organisms, combustion of biomass and fossil fuels.
- removed by photosynthesis and dissolving in oceans

water vapour:
- evaporation from the oceans and transpiration in plants
- removed by rainfall and snow

56
Q

why does temperature drop so much more quickly at night in areas with clear skies than in areas with cloud cover?

A

water continues to retain heat after it condenses to form droplets of liquid water in the clouds - the water absorbs heat energy, radiates it back to the earth’s surface, and reflects the heat energy back

57
Q

give 2 other greenhouse gases that have less of an impact

A

methane:
- emitted from marshes/waterlogged habitats and landfill sites where organic wastes have been dumped
- released during extraction of fossil fuels and from melting ice in polar regions

nitrous oxide:
- released naturally by bacteria in some habitats and also by agriculture and vehicle exhausts

58
Q

what two things does the impact of a gas depend on?

A

its ability to absorb long-wave radiation
its concentration in the atmosphere (determined by the rate at which it is released into the atmosphere and how long on average it remains there)

59
Q

give the steps of climate change

A
  1. surface of the earth absorbs short-wave energy from the sun
  2. the warmed earth emits longer-wave (mostly infrared) radiation
  3. this is reabsorbed by greenhouse gases which retains the heat in the atmosphere, causing global warming
60
Q

what does data collected from the Vostok ice core demonstrate?

A

There is a strong positive correlation between carbon dioxide concentrations and temperature (↑ CO2 levels ∝ ↑ temperature)

61
Q

how can past global temperatures and carbon dioxide concentrations be deduced?

A

with Ice cores taken from the Vostok station in Antarctica:
- temperatures can be deduced from ratios of hydrogen isotopes in the water molecules
- bubbles of air trapped in the ice can be extracted and analysed to find the carbon dioxide concentration

62
Q

what are global temperatures and climate patterns influenced by?

A

concentrations of greenhouse gases; these will affect how much heat is retained

63
Q

give examples of how global temperatures influence other aspects of climate

A

Enhanced greenhouse effect:
- higher temp = more evaporation of water from oceans and more frequent/protracted periods of rain
- more frequent extreme weather conditions (e.g. heat waves, cyclones, more powerful tropical storms, etc.)
- some areas to become more drought affected, while other areas become more prone to periods of heavy rainfall
- changes to circulating ocean currents – which may cause longer warming and cooling events

64
Q

state the relationship between industrialisation and climate change

A

there is a correlation between rising atmospheric concentrations of carbon dioxide since the start of the industrial revolution two hundred years ago and average global temperatures

here, combustion of coal, oil, and natural gas increased rapidly

65
Q

give factors (aside from greenhouse gas emissions) that may influence global average temperatures

A
  • Milankovitch cycles in the earth’s orbit
  • variation in sunspot activity
  • volcanic activity
  • cycles in ocean currents
66
Q

what are recent increases in atmospheric CO2 largely due to?

A

increases in the combustion of fossilised organic matter
- deforestation
- increased farming and agriculture

67
Q

state the relationship between CO2 Emissions and Ocean Acidification

A

Rising levels of atmospheric carbon dioxide are causing a decrease in the pH of ocean water (ocean acidification)

CO2 solubility is temperature dependent (more soluble when cooler), so less CO2 will be absorbed as temperatures rise

  • some CO2 will remain dissolved in a gaseous state but most will combine with water to form carbonic acid, which dissociates into hydrogen ions and hydrogen carbonate
  • H+ ions will lower the ocean pH (acidification) and will also combine with free carbonate ions to form more hydrogen carbonate
68
Q

describe the effects of ocean acidification on marine biodiversity

A
  • with less free carbonate ions in the water, marine organisms are less able to produce calcium carbonate (via calcification)
  • shells and coral exoskeletons are also likely to begin to dissolve when ocean conditions are more acidic
  • this threatens the viability of coral reefs and certain molluscs

IB biology (60 decks)

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