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Biology Paper 1 > TOPIC 10: ECOSYSTEMS > Flashcards

TOPIC 10: ECOSYSTEMS Flashcards

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1
Q

Define Ecosystem

A

A self-contained environment containing all the abiotic and biotic factors. Ecosystems range in sizes

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2
Q

Define Trophic level

A

The trophic level of an organism is the position it occupies in a food web. (feeding level)

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3
Q

Describe the advantages and disadvantages of the pyramid of number

A

They are easy to measure

counting the actual numbers for a whole ecosystem can be time consuming . The main drawback is that the bars simply compare the counts of organisms but the organisms are of very different sizes oak trees and insects also choosing scales to plot one axis will be difficult as the organisms are so largely different in sizes

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4
Q

Describe the advantages and disadvantages of the pyramid of biomass

A

Different components of biomass have very different energy contents per kilogram.It is also very time consuming to weigh each organism concerned. As we need the dry biomass the animal has to be dehydrated and dried out so it will be dead this may be deemed unethical

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5
Q

Describe the advantages and disadvantages of the pyramid of energy

A

The amount of energy at each trophic level is measured and a pyramid is drawn. The units for energy are expressed as kJ m^-2 yr^-1.

The pyramid of energy is accurate but it is hard to measure and uses a single set of measurements ,a single set of measurements gives us the situation at one snapshot in time but we know that ecosystems are subject to lots of fluctuations.

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6
Q

Describe ways to measure abundance of species

A
  1. Quadrats can be used they make sure that the sampling areas are the same size
  2. Estimates of percentage cover
  3. light traps to attract flying insects
  4. Capture/recapture techniques for animals that move around
  5. Beating of branches to collect what falls out
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7
Q

What is the subjective scale for animals

A

ACFORN

  1. Abundant
  2. Common
  3. Frequent
  4. Occasional
  5. Rare
  6. None
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8
Q

What is the subjective scale for plants

A

DAFORN

  1. Dominant
  2. Abundant
  3. Frequent
  4. Occasional
  5. Rare
  6. None
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9
Q

Describe ways to measure distribution

A

collecting data about distribution needs to be done in a systemic way

  1. Line transect
  2. Belt transect
  3. Interrupted belt transect
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10
Q

What is a line transect

A

Record organisms touching a line between two points

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11
Q

What is a belt transect

A

Record organisms in quadrats along a line between two points

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12
Q

What is an interrupted belt transects

A

Sample at regular intervals rather than recording a whole belt

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13
Q

When are transects used

A

Most often used to discover correlations between species distribution and environmental factors along a gradient

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14
Q

What is systematic sampling

A

Systematic sampling is sampling matching a pattern or sampling at periodic intervals from a large area

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15
Q

What is random sampling

A

Random sampling is sampling at random this eliminates bias; a number coordinate generator or dice can be used to make it random.

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16
Q

What are frame quadrats used for and how are they used

A
  1. used to collect frequency data
  2. Each plant is identified and then the number of squares the plant is identified in is counted
  3. Data collection is objective ( everyone looking at the sample should get the same answer)
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17
Q

What are point quadrats used for

A
  1. used to estimate percentage occurrence of individuals
  2. Useful when plant live in a mixed community and it is hard to identify distinct individuals
  3. More likely to miss rare or small plants as you are sampling a very small proportion of the population
  4. Less prone to random error
  5. Objective
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18
Q

What are the three things to consider when using quadrats

A
  1. The size of the quadrat - This will depend on the size of the organisms being investigated
  2. The number of samples being taken in the area- The more samples you take in the habitat the more reliable the results will be
  3. The position of each quadrat- its best to make it as unbiased and as quick as possible
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19
Q

List some abiotic factors

A 
Wind
Temperature 
Soil PH 
Humidity 
Soil moisture 
Light intensity
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20
Q

List some biotic factors

A 
Competition 
Predation 
Diversity 
Parasites 
Disease
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21
Q

Equation for estimated mean density

A

Total number of individuals counted / Number of quadrats x Area of quadrat

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22
Q

Define null Hypothesis

A

The null hypothesis, states that there is no effect or difference (e.g. no difference between groups, or no correlation between variables).

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23
Q

What is the P value

A

The probability that our results would be obtained if the null hypothesis were true

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24
Q

When do we reject the null hypothesis

A

If P < 0.05 this means there is a less than 5% probability that the observed effect is due to chance and we reject the null hypothesis and conclude there is a significant effect

25
Q

When do we accept the null hypothesis

A

If P > 0.05 OR P is equal to 0.05 this means that there is more than 5% probability that the observed effect is due to chance we accept the null hypothesis and conclude there is no significant effect

26
Q

How do we determine whether the p value is greater or less than 0.05

A
  1. Calculate a test statistic
  2. Compare it wit the critical value in the table
  3. Use this to determine whether the P-value is greater or less than 0.05
27
Q

When do we reject the null hypothesis

A

Critical value < the calculated value, means the P< 0.05 we reject the null hypothesis

28
Q

When do we accept the null hypothesis

A

Critical value > the calculated value, means the P > 0.05 we accept the null hypothesis

29
Q

What is the Standard Deviation

A

The standard deviation measures the dispersion of the raw data around the mean. The standard deviation is more representative than the range as it is calculated from replicate data. The larger the standard deviation the larger the spread of the data about the mean the less reliable the sample

30
Q

Equation for Standard deviation

A

s=square root of sum of (value-mean)^2 /number of values-1

31
Q

What is the unpaired t-test

A

The unpaired t-test tests for differences between two sets of independent data.
The unpaired t-test tests the null hypothesis that there is no difference between the means of two sets

32
Q

Equation for Unpaired t-test

A

t= mean of set data 1 -mean of set data 2/square root of standard deviation 1^2/number of repeats of set data 1 + standard deviation 2^2/number of repeats of set data 2

33
Q

When do you use the mean and standard deviation test

A

For summarisation of quantative (numeric) data

34
Q

When do you use the unpaired t-test (independent samples)/ Paired t-test ( matched samples)

A

To compare two sets of quantative numeric data ( bar chart)

35
Q

When do you use the Spearman correlation coefficient test

A

To correlate two sets of quantative numeric data (scatter graph)

36
Q

What do you use to summarise qualitative categoric data

A

Tally frequencies

37
Q

What do you use to compare two sets of qualitative categoric data

A

Chi-squared data

38
Q

What is gross primary productivity

A

The amount of light energy fixed by photosynthesis in a given area and fixed time
The units are: KJ/m^2/year

39
Q

What is net primary productivity

A

The total amount of light energy fixed by photosynthesis in a given area and fixed time after losses and uses by producer KJ/m^2/year

40
Q

Equation linking GPP and NPP

A 
NPP= GPP-R 
R= energy lost in plant respiration
41
Q

Describe the ways in which energy can be used or lost in food webs?

A
  1. Through movement of the animal (respiration)
  2. Through excreted matter
  3. Through storage in cells and tissues
42
Q

What are Detritivores?

A

Animals that feed off dead and decaying organic materials. They are important recyclers in all ecosystems

43
Q

What are Sapratrophs?

A

Mainly fungi or bacteria; feeding by secreting extracellular enzymes to break down dead organic matter and reabsorb products

44
Q

What are Scavengers?

A

Opportunist feeders on the remains of dead animals and faeces

45
Q

What is a Carbon Sink?

A

A natural or artificial reservoir that accumalates and stores some carbon-containing chemical compound for an indefinate period

46
Q

What is the removal of carbon dioxide from the atmosphere known as ?

A

Carbon Sequestation

47
Q

Why are nitrates so important for plants ?

A

Plants take nitrates from the soil to produce amino acids and therefore proteins, and to produce the nucleotides used to build DNA and RNA

48
Q

What do Nitrifying bacteria do ?

A

They convert the ammonium compounds that were produced during decomposition into nitrates

49
Q

What does Nitrogen-fixing bacteria do ?

A

They convert inert nitrogen gas from the atmosphere into ammonia

50
Q

What does Denitrifying bacteria do ?

A

They release nitrogen gas from nitrates, making the nitrogen unavailable to plants

51
Q

What effect does ploughing have on anaerobes like denitryfying bacteria?

A

Ploughing:

  1. Aerates the soil
  2. More nitrates formed (nitrification)
  3. Less denitrification to lessen the nitrogen back into the atmosphere
52
Q

What is the point in crop rotation ?

A

Crop rotation can be used to replenish nitrogen concentrations in the soil
legumes with nitrogen fixing nodules increase nitrification and increase nitrogen in the soil

53
Q

What is the null hypothesis for a paired t-test

A

Null Hypothesis: The mean of the paired differences is zero (or there is no difference between the two conditions)

54
Q

What is a paired t-test

A

The paired t-test tests the null hypothesis that the mean of the paired differences is zero, in other words that there is no difference between the two groups. Note that this is a different test from the unpaired t-test, so it has a slightly different null hypothesis.

The paired t-test is for experiments where the data is “matched”, eg in a before and after experiment were the same location is investigated but at different times

55
Q

Equation for paired t-test

A

t= absolute mean of the differences x square root of the number of pairs / the standard deviation of the differences

56
Q

What does the Spearmans rank correlation coefficient tell us

A

The spearman rank correlation coefficient gives us the strength of a correlation on a scale of -1 to +1.

-1 is the perfect negative correlation
+1 is the perfect positive correlation

57
Q

What is the null hypothesis for Spearmans rank correlation

A

The null hypothesis is that there is no correlation between the two sets of data

58
Q

Equation for Spearmans rank correlation

A

1- 6 x Difference in ranks ^2/ number of pairs cubed-number of pairs

Biology Paper 1 (17 decks)

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