topic 10.1 - nature of ecosystems Flashcards
1
Q
what is an ecosystem
A
- an environment including all the living and non living factors which they interact with
- can be many sizes
2
Q
population
A
a group of organisms of the same species that breed together in the same habitat
3
Q
community
A
- group of population of different species interacting in the same habitat
4
Q
niche
A
- role of an organism in a community
- includes everything with which the organism interacts
5
Q
habitat
A
- place where an organism lives
6
Q
biotic factors
A
- living elements of a habitat that affect ability of organisms to live there
- e.g. availability of prey, bacteria
7
Q
abiotic factors
A
- non-living elements of a habitat
- e.g. sunlight, temp, soil, pH, rainfull, O2 in water
8
Q
biosphere
A
- all the areas of the surface of the earth where living organisms survive
9
Q
biome
A
- the major ecosystems of the world
10
Q
what is meant by trophic levels
A
- describe the feeding relationships and position of an organism in a food chain or web
11
Q
how can trophic levels be represented
A
- pyramids of numbers
- biomass (dry)
- energy
12
Q
different trophic levels within a food web
producers
A
- producers are the first stgae in any food chain
- plant & algae use sunlight to photosynthesise - nutrients from soil and CO2 from air
13
Q
different trophic levels within a food web
primary consumers
A
- organisms which consume producers
- harbivores digest plant materials to obtain energy and nutrients
14
Q
different trophic levels within a food web
secondary consumers
A
- organisms which feed on herbivores
- carnivores prey on herbivores to obtain nutrients & energy
15
Q
different trophic levels within a food web
tertiary consumers
A
- organisms which eat other carnivores
- top carnivores prey on other carnivores to obtain nutrients and energy
16
Q
different trophic levels within a food web
decomposers
A
- digest dead organic material
- final trophic level in any feeding relationship
- microorganisms (i.e. bacteria & fungi) that break down remains of animals & plants
- return nutrients to soil
17
Q
advnatages and disadvantages of pyramids of numbers
as representation of ecosystem structure & how biomass & energy transferred
A
ADV
- easiest to meausure
DISADV
- least accurate
18
Q
advantages & disadvantages of biomass
as representation of ecosystem structure & how biomass & energy transferred
A
ADV
- more accurate
DISADV
- don’t take into account rate of production of biomass
- using dry mass is bad bc dehydration kills organisms
- using wet mass is less accurate
19
Q
advantages and disadvantages of energy levels
as representation of ecosystem structure & how biomass & energy transferred
A
ADV
- most accurate
DISADV
- hardest to measure
- rarely used in practice
20
Q
abundance
A
- the relative representation of a species in a particular ecosystem
- total number of individuals of a species present in an ecosystem relative to other organims in the same habitat
21
Q
distribution
A
- where species of organisms are found in the environment & how it is arranged
- how spread out the organisms are from eachother
22
Q
ecological techniques
A
- quadrat
- transect
- ACFOR scales
- percentage cover
- individual counts
23
Q
quadrats
A
- square gridded frames placed randomly
- count the number of individual organisms inside (individual counts)
- find area covered by organisms using divided grid (percentage cover)
- take multiple reading & find mean
24
Q
issue with quadrats
A
- issues about decisions on whether to include organisms partly covered by quadrat
- need to make these decisions before starting
25
uniform distribution
- when resources are thinly but evenly spread
26
clumped distribution
- distribution in groups (e.g. herd of animals)
- groups of animals/plants which have specific resource requirements
- clump in areas where they are found
27
random distribution
- result of plentiful resources and no antagonism
- e.g. dandelions in a field
28
ACFOR scale
- use **ACFOR** scale to measure abundance of organisms in a quadrat or area
**A** = abundant
**C** = common
**F** = frequent
**O** = occasional
**R** = rare
29
what is the issue with the ACFOR scale
- it is subjective
- 2 people will not come up with the same rating
- no set definition of term
- i.e. what is 'common'?
30
line transect
- runs across the area to be investigated
- records organisms touching a line between two points
31
belt transect
- 2 tapes laid out
- area between them surveyed using quadrats along a line
32
interrupted belt transect
- sample at regular intervals rather than recording a whole belt
33
other measures of abundance
- light traps to attract flies/insects
- capture/recpature techniques for animals that move around
- beating of branches to collect what falls out
34
what are transects mostly used for
- to discover correlations between species distribution and environmental factors
- i.e. light intensity or soil pH
- these factors are also measured along the transect
35
aspects of making comparisons between sampling techniques
- transects & random sampling
- belt & interrupted transects
- different quadrat sizes
- types of quadrats
- counting individuals & percentage cover
36
# statistical testing to analyse data
what is observer value
- on table of critical values
- need to look up the osberver value for each test to see which probability value this corresponds with
- then you can see if the null hypothesis should be accepted or not
37
# statistical testing to analyse data
null hypothesis
- hypothesis that any differences between data sets are simply due to chance
38
Statistical tests can indicate if differences in results (from sampling methods) are significant
- significant = less than **0.05**
- corresponds to the **p < 0.05**
39
# statistical tests
Spearman's rank correlation coefficient - why is it used?
- to measure the correlation between two variables
## Footnote
the extent to which changing one variable affects the other variable
40
# statistical tests
Spearman's rank correlation coefficient - how to use it
1. state the null hypothesis
2. give rank to each item in each set of measurements
3. find the differences between ranks for each pair of measurements
4. add all the differences together and use formula to calculate the correlation coefficient; r(s)
41
# statistical tests
Spearman's rank correlation coefficient - interpreting results
- closer to 1 - more positive correlation
- closer to -1 - more negative correlation
- around 0 - no correlation
42
# statistical tests
Spearman's rank correlation coefficient - what is the null hypothesis
- that there is no correlation between the two variables
43
# statistical tests
Spearman's rank correlation coefficient - deciding whether to accept the null hypothesis or not
- state null hypothesis
- compare to critical value (0.05)
- <0.05 = significant
- >0.05 = not significant
44
# statistical tests
Student's t-test - why is it used
- to see if there is a difference between means values from two sets of measurements
45
# statistical tests
student's t-test - how to do it
1. state the null hypothesis
2. calculate observer value (t) using formula
3. use table to see if *t* is above or below p = 0.05 for (n1 + n2) - 2 degrees of freedom
46
# statistical tests
student's t-test - intepreting the results
- *t* value compared to a critical value for a particular p value chosen by researcher
- find degrees of freedom (total nuber of data - 2)
- find probability, **p**, that relates to oberver value & degree of freedom
- if p < 0.005, difference is significant
