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A-LEVEL BIOLOGY > ECOLOGICAL TECHNIQUES > Flashcards

ECOLOGICAL TECHNIQUES Flashcards

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1
Q

What do the symbols mean in the MRR equation? (4)

A

N = total number in population
n = total number of animals recaptured
K = total number of animals marked
k = total number of recaptured animals that were marked

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2
Q

how do you calculate the number of organisms in the whole population using MRR? (1)

A

N = nK/k

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3
Q

what does MRR stand for? (1)

A

mark, release, recapture

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4
Q

what are the types of transects? (2)

A

continuous belt transects
interrupted transect

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5
Q

what is a point frame? (2)

A

consists of a frame with 10 pointed metal pins, frame is placed at chosen sampling point and only plants touching the ten points of the metal pins is recorded. used in dense vegetation

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6
Q

what is a transect? (2)

A

a graduated line across the area you wish to study - most useful when investigating the effect of a gradient of factors across a habitat.

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7
Q

how can you count the abundance of an organism? (3)

A
  • count each individual of a species
  • percentage cover
    -relative abundance (ACFOR scale)
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8
Q

what is objective data? (1)

A

data that can be measured (e.g species diversity)

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9
Q

what is subjective data? (1)

A

data that is based on personal opinion (e.g estimations)

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10
Q

what is a gridded quadrat? (2)

A

a frame quadrat modified by adding strings to form extra squares within the frame. ensures organisms are not counted twice and making estimates with percentage cover.

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11
Q

what is a quadrat? (1)

A

a frame that outlines an area of known size for sampling purposes.

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12
Q

what are biotic factors? (2)

A

living factors such as, distribution/number of a species, biodiversity, species richness, population size, etc

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13
Q

what are abiotic factors? (2)

A

non-living factors such as water availability, soil pH, temperature, oxygen availability, wind speed, etc

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14
Q

what equipment is used for sampling? (3)

A

-frame quadrat
-gridded quadrat
-point quadrat

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15
Q

why do we take measurements of these factors? (2)

A

-to compare and contrast ecosystems of two areas
-to evaluate an ecosystem over time or before and after an event (earthquake or tsunami)

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16
Q

what does ACFOR stand for? (5)

A

Abundant
Common
Frequent
Occasional
Rare
X - absent

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17
Q

what effects the number of quadrats you need to use? (1)

A

whether it has homogenous distribution or heterogenous distribution.

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18
Q

how many quadrats should you use for a area of homogenous distribution? (1)

A

for habitats that show homogenous distribution of plants 2% of the area should be sampled.

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19
Q

how many quadrats should you use for a area of heterogenous distribution? (1)

A

for habitats that show heterogenous distribution of plants 10-20% should be sampled.

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20
Q

what is random sampling? (1)

A

locations ae selected at random within an area.

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21
Q

what is systematic sampling? (1)

A

locations are predetermined based on the variables being investigated.

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22
Q

what is stratified sampling? (1)

A

this is where a proportioned number of observations is taken from each part of the population.

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23
Q

what is a line transect used for? (1)

A

is useful for examining the effect of change in habitat on biodiversity, any species touching the line at fixed intervals is recorded.

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24
Q

what is a belt transect used for? (1)

A

quadrats are taken at regular intervals along the line to identify the number/density of species.

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25
Q

what are the advantages of random sampling? (2)

A

-Can be used with large sample populations
-avoids bias

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26
Q

what are the disadvantages of random sampling? (2)

A

-can lead to poor representation of the overall parent population or area if large areas are not hit by the random number generated
-there may be practical constraints in terms of time available and access to certain parts of the study area

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27
Q

what are the advantages of systematic sampling? (3)

A

-more straight forward than random sampling
-a grid does not necessarily have to be used, just has to be at uniform intervals
-a good coverage of the study area can be more easily achieved than at random

28
Q

what are the disadvantages of systematic sampling? (2)

A

-more biased as not all members or points have an equal chance of being selected
-it may therefore lead to over or under representation of a particular pattern

29
Q

what are some common methods of sampling? (4)

A

-quadrats
-kick sampling
-plankton nets
-pitfall traps

30
Q

what is Lincoln’s index? (1)

A

population = total number of animals in 1st sample x (total number of animals in 2nd sample / number of marked animals in 2nd sample)

31
Q

what are the three types of statistical tests? (3)

A

-spearmens rank
-chi squared test
-T test

32
Q

what is spearmens test used for? (1)

A

to test for correlations between two continuous variables.

33
Q

what is the chi squared test used for? (1)

A

to test for associations between two or more data sets.

34
Q

what is the T test used for? (1)

A

for differences between two sets of data by measuring the difference between the means.

35
Q

what data does spearmens rank test? (1)

A

continuous, interval or ordinal data - when plotted on a scatter graph the relationship should be linear.

36
Q

what data does the chi squared test use? (1)

A

categorial, only used with raw data, not percentages.

37
Q

what data does the T test use? (1)

A

continuous interval data, when plotted as a histogram both samples should show a normal distribution.

38
Q

what is a normal distribution curve? (1)

A

the mean, mode and median are the same.

39
Q

what if a curve does not fit the normal distribution curve? (1)

A

if it does not fir this it is called an abnormal distribution curve.

40
Q

what does a normal distribution curve look like? (2)

A

-a bell shaped curve
-50% values either side of mean

41
Q

what is meant by a null hypothesis? (1)

A

there is statistically significant difference.

42
Q

what does a niche consist of? (2)

A

a biotic and biotic interactions.

43
Q

what occurs if two species occupy the same niche? (1)

A

if two species occupy the same niche they will compete with each other.

44
Q

what is the carrying capacity? (1)

A

the maximum stable population size of a species that an ecosystem can support.

45
Q

how does interspecific competition effect population size? (3)

A

interspecific competition can mean that the resources available to both populations are reduced so the population sizes will be lower for both species.
-but if one of the species is better adapted to its surroundings than the other, the less well adapted species it likely to be out-competed - it wont be able to live along side the better adapted species.

46
Q

when does the population of a species increase? (3)

A

the population of a species increases when resources are plentiful, as the population increases they will be more organisms completing for the amount of space and food.
-eventually resources become limiting, there isn’t enough for all organisms so population declines.
-a smaller population = less competition which is better for growth and reproduction so the population starts to grow again

47
Q

what is the issue with the simplistic model of predator-prey relationships? (1)

A

predator-prey relationships are more complicated than this due to the impact of other factors such as food availability for prey.

48
Q

why do we repeat investigations? (1)

A

this will reduce the likelihood that your results are due to chance.

49
Q

what assumptions must be made doing the MRR method? (3)

A

-the marked sample has had enough time and opportunity to mix back in with the population
-the marking hasn’t affected the individuals chance of survival and the marking itself is still visible
-there are no changes in population size due to birth, deaths and migration during study

50
Q

how do you measure pH? (2)

A

-use a digital probe to take readings of sand or soil in the field
-add some barium sulphate to a sample with distilled water and pH indicator, shake and check colour on pH chart

51
Q

why does pH tend to decrease as you move inland? (1)

A

pH decreases as you move inland this is because near the shore the sand/soil contains lots of shell fragments that are made of calcium carbonate, an alkaline compound - further inland the rotting vegetation adds organic matter to the oil, which is more acidic.

52
Q

what does a low chi-squared value indicate? (1)

A

A low value suggests that the observed data fits well with the expected ratio.

53
Q

what does a high chi-squared value indicate? (1)

A

A high value may indicate a significant deviation due to reasons like genetic linkage, mutations, or environmental factors.

54
Q

what factors influence the value of chi-squared results? (3)

A

-sample size
-randomness
-genetic linkage

55
Q

how does sample size effect the value of chi-squared? (2)

A

-large sample sizes ; Provide more reliable and statistically significant results
-small sample sizes ; Can result in misleading Χ² values due to higher variability in smaller data sets.

56
Q

how does randomness effect the value of chi-squared? (1)

A

The test assumes that factors such as mating and segregation of alleles occur randomly. Non-random mating or segregation can lead to skewed results.

57
Q

what is meant by the p-value? (1)

A

The p-value represents the probability of obtaining test results at least as extreme as the observed results, under the assumption that the null hypothesis is true.

58
Q

what does a value less than a p value of 0.05 indicate? (1)

A

Indicates that there is less than a 5% chance that the observed deviation from the expected ratio is due to random chance, leading to the rejection of the null hypothesis.

59
Q

what does a value greater than a p value of 0.05 indicate? (1)

A

Suggests that the observed deviation could reasonably occur by chance, and thus, the null hypothesis cannot be rejected.

60
Q

If the data presented within an experiment is not normally distributed what is the preferred test to use? (1)

A

if the data is not normally distributed use Spearman ranks coefficient.

61
Q

what are the steps to calculate spearman’s rank? (5)

A

step 1; rank each set of data (rank 1 being the smallest data figure)
step 2; find the difference in rank for the two species
step 3; square the difference in rank
step 4; substitute the appropriate numbers into the equation
step 5; refer to a table that relates values of rs to probability

62
Q

when is it applicable to use the t-test? (1)

A

the sets of data must follow a rough normal distribution, to be continuous and the standard deviations should be approximately equal.

63
Q

what is meant by standard deviation? (1)

A

a measure of how spread out the mean values are.

64
Q

what is meant by x1 and x2? (1)

A

the mean for sample 1 and sample 2.

65
Q

how do you calculate the degree of freedom? (1)

A

v = (n1 - 1) + (n2 -1)

66
Q
A

A-LEVEL BIOLOGY (46 decks)

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