T10.1 - The Nature of Ecosystems

Question 1

Define population

Answer 1

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

Question 2

Define community

Answer 2

A group of populations living together and interacting with each other within a given area.

Question 3

Define habitat

Answer 3

The environment in which a species normally lives, or the location of a living organism.

Question 4

Define habitat biodiversity

Answer 4

A measure of the number of different habitats found within an area.

Question 5

State what is meant by the term ecosystem

Answer 5

All the living organisms and all the nonliving components in a specific habitat, and the interactions between them.

Question 6

State what is meant by the term niche

Answer 6

The functional position and role of an organism within its environment.

Question 7

State what is meant by the term fundamental niche

Answer 7

The entire set of conditions under which an organism can survive and reproduce (i.e. where it can live).

Question 8

State what is meant by the term realised niche

Answer 8

The set of conditions used by a given organism after interactions with other species are taken into account (i.e. where it does live).

Question 9

What term is given to all or the areas of the surface of the earth where living organisms survive.

Answer 9

Biosphere

Question 10

What is a biome?

Answer 10

A major ecosystem, distinguished by its climate and plant species which live there.

Question 11

What are biotic factors?

Answer 11

The living factors in a habitat when an organism lives

Question 12

What are abiotic factors?

Answer 12

The non living factors in a habitat where the organism lives

Question 13

What is competitive exclusion

Answer 13

When one species uses resources more efficiently and drives the other species to local extinction.

Question 14

What is resource partitioning?

Answer 14

When two or more species alter their use of the niche to avoid direct competition, allowing for co-existence.

Question 15

What do food chains show?

Answer 15

Linear feeding relationship between species in a community

Question 16

What do arrows represent in a food chain

Answer 16

Transfer of energy and matter as one organism is eaten another, pointing in direction of energy flow

Question 17

What is meant by trophic level?

Answer 17

The feeding position that an organism holds in a food chain, web, pyramid of numbers or biomass

Question 18

List the trophic levels from first to fourth

Answer 18

1. Producers
2. Primary consumers
3. Secondary consumers
4. Tertiary consumers

Question 19

What are autotrophs?

Answer 19

Organisms that produce their own food by converting carbon dioxide (from atmosphere or dissolved in water) into organic compounds

Question 20

What is the difference between photoautotrophs and chemoautotrophs?

Answer 20

Photoautotrophes use light energy
Chemoautotrophes use energy released from the oxidation of inorganic compounds

Question 21

Give example of photoautotroph

Answer 21

Plants or algea

Question 22

Give an example of a type of chemoautotroph

Answer 22

Nitrosomonas / Nitrobacter / Methanogens / Iron bacteria

Question 23

How do chemoautotrophs make organic compounds?

Answer 23

Chemosynthesis - oxidise inorganic energy sources to synthesize organic compounds from carbon dioxide.

Question 24

Name three examples of heterotrophs

Answer 24

Consumers, detritivores, saprotrophs

Question 25

Define hetertroph

Answer 25

An organism that eats other plants or animals for energy and nutrients.

Question 26

What is a pyramid of numbers?

Answer 26

Graphical representation of the number of organisms at each trophic level of a food chain.

Question 27

Give an advantage and disadvantages of pyramids of number

Answer 27

It is easiest to mease (counting), but can be distorted by large organisms.

Question 28

What is a pyramid of biomass?

Answer 28

Graphical representation of the combined biomass of all the organisms at each trophic level of a food chain.

Question 29

Why is dry biomass more accurate that wet biomass?

Answer 29

Water content in organisms is variable

Question 30

Explain the shape of a pyramid of biomass

Answer 30

Always upright in shape, as biomass diminishes along food chains as carbon dioxide and water (urea) is released

Question 31

Explain why pyramids of biomass for marine ecosystems are not upright

Answer 31

Phytoplankton replace their biomass at such a rapid rate they can support a larger biomass of zooplankton

Question 32

State an advantage of a pyramid of biomass

Answer 32

More accurate representation than pyramid of numbers as not inverted by large organisms.

Question 33

What are the disadvantages of a pyramid of biomass?

Answer 33

Calculating dry biomass requires destruction of the material. To avoid destroying whole habitats, small samples are taken and results scaled up - so only estimate. Does not take into account rate of biomass production.

Question 34

What is a pyramid of energy?

Answer 34

Graphical representation of the total energy content of all organisms at each trophic level of a food chain.

Question 35

What are the advantages of a pyramid of energy?

Answer 35

It will never appear inverted as some of the energy stored in one source is always lost upon transfer It takes into account the rate the producers are reproducing over a period of time.

Question 36

What is a disadvantage of a pyramid of energy?

Answer 36

Extremely difficult to measure accurately

Question 37

Explain where decomposers go on a pyramid

Answer 37

Decomposers occupy every trophic level after the first, so appear to the side, separate to the rest

Question 38

How is the abundance (population size) of a species in a habitat measured?

Answer 38

Random sampling using quadrats

Question 39

When assessing abundance of an organism, why must the sample sites be selected at random?

Answer 39

To prevent bias and get a representative sample

Question 40

How can you select random sample positions?

Answer 40

Use random number tables/generators to plot coordinates within the habitat. Select coordinates from a map and use GPS.

Question 41

How can abundance be quantified?

Answer 41

Quantitative - Percentage cover, frequencies Qualitative - ACFOR scale

Question 42

What does ACFOR stand for?

Answer 42

Abundant Common Frequent Occasional Rare

Question 43

Describe how a point quadrat is used to estimate percentage cover

Answer 43

Metal pins are dropped through each hole in turn and ‘hits’ are recorded. Percentage cover = (No. of hits / total no. of hits) x 100

Question 44

What will the number of samples taken depend on?

Answer 44

The size of the habitat The time of year The diversity of the habitat being studied

Question 45

Suggest ways to get a more accurate estimate of population size (abundance)

Answer 45

The larger the sample size the more accurate the estimate So use larger quadrats/use more quadrat positions

Question 46

Outline how to estimate population size in a given area.

Answer 46

Place frame quadrat at minimum of 10 random positions. Count number of organisms in each quadrat and calculate mean. Calculate population size (no.): mean x (total area of habitat / area of quadrat)

Question 47

Outline how to estimate the density of organisms in a given area.

Answer 47

Place frame quadrat at minimum of 10 random positions. Count number of organisms in each quadrat and calculate total. Calculate density (no. per metre squared): total / (no. of quadrats x area of each quadrat)

Question 48

Outline how to estimate the relative abundance of a plant species in a given area.

Answer 48

Place frame quadrat at minimum of 10 random positions. Count number of each plant in each quadrat and calculate total. Calculate relative abundance (%): (No. of plant X in all quadrats / Total no. of all plants) x 100

Question 49

Outline how to estimate the of a plant species in a given area.

Answer 49

Place frame quadrat with 10x10 grid at minimum of 10 random positions. Count how many whole squares are covered by each species of plant. 1 square = 1%.

Question 50

How is the distribution of organisms measured in a habitat?

Answer 50

Systematic sampling using a line/belt transect

Question 51

What is a transect?

Answer 51

Line across a habitat used to measure the change in distribution and abundance of organisms in an area.

Question 52

What is zonation

Answer 52

The changing distribution pattern of a species in response to a change in an abiotic factor or competition.

Question 53

What can transect data be used for?

Answer 53

data can used to identify optimum conditions as a well as zones of stress and zones

Question 54

What is a line transect used for?

Answer 54

For large/rare animals e.g snakes

Question 55

What are belt transcects?

Answer 55

Qudrats are placed along a transect line and numbers of organisms in each qudrat are counted. Continous belt transects place quadrat continuously along the transect line with no gaps. Interrupted belt transects place quadrats at regular intervals along the transect line.

Question 56

What is kite diagram

Answer 56

Graph that shows the number of animals (or percentage cover for plants) against distance along a transect.

Question 57

Suggest some abiotic factors that could affect the abundance and distribution of organisms in a habitat

Answer 57

Light intensity, pH, salinity, temperature, Wind speed, humidity, water availability

Question 58

Suggest some biotic factors that could affect the abundance and distribution of organisms in a habitat

Answer 58

Competition, predation, herbivory, human activities etc.

Question 59

What piece of apparatus is used to sample plants and slow moving (sesile) animals?

Answer 59

Quadrats

Question 60

What method is used to sample fast moving (motile) animals?

Answer 60

Mark Release Recapture

Question 61

Outline the mark-release-recapture method

Answer 61

Capture sample of animals. Record the number captured - S Mark each individual, ensuring it doesn't cause harm, and release them. Capture a second sample after a set period of time e.g. 48 hours, using the same capture technique. Record number captured in second time = S . Record the number of recaptured (marked) animals - R. Calculate population size using the Lincoln Index: N = (S x S ) / R

Question 62

What method would you use to compare abundance of organisms in two different areas?

Answer 62

Random sampling using quadrats in both areas.

Question 63

What would you use Student's t-test for?

Answer 63

To determine if there is a significant difference between two means for one characteristic between two sub-groups (e.g. comparing mean fruit weight for two crops grown in different fields)

Question 64

When can you use student t-test for?

Answer 64

When the sample size is less than 30 and the data is normally distrubuted

Question 65

What is the null hypothesis when using the t-test?

Answer 65

There is no significant difference between sample A and sample B, any difference is due to chance or sampling error.

Question 66

How do you calculate the degrees of freedom when using the t-test?

Answer 66

total number of data values minus 2

Question 67

What siginificance level is used in statistical tests?

Answer 67

p=0.05

Question 68

What is the name of the value that you compare the t value with?

Answer 68

Critical value

Question 69

If the value is less than the critical value, what do you conclude?

Answer 69

There is greater than 5% propbaility that the difference between the two means is due to chance or sampling error. Therefore ACCEPT the null hypothesis; there is no significant difference between the mean of sampel A and sample B.

Question 70

If the t value is greater than the critical value, what do you conclude?

Answer 70

There is less than 5% propbaility that the difference between the two means is due to chance or sampling error. Therefore REJECT the null hypothesis; there is a significant difference between the means of sample A and sample B.

Question 71

What would you use Spearman's rank correlation coefficient (r ) for?

Answer 71

To determine if there is a correlation between two variables.

Question 72

What is the null hypothesis for Spearman's rank correlation coefficient?

Answer 72

There is no statistically significant correlation between (variable 1) and (variable 2), any correlation is due to chance.

Question 73

How do you calculate the degrees of freedom for Spearman's rank?

Answer 73

n (number of pairs of data)

Question 74

If r = -1, what does this indicate?

Answer 74

There is a perfect negative correlation between the two variables (as x increases, y increases)

Question 75

If r = +1, what does this indicate?

Answer 75

There is a perfect positive correlation between the two variables (as x increases, y decreases).

Question 76

If r = 0, what does this indicate?

Answer 76

There is no correlation between the two variables.

Question 77

When you are thinking about correlation, just remember this rule

Answer 77

The closer the correlation is to 0, the weaker it is, while the closer it is to +/-1, the stronger it is.

Question 78

If the is less than the critical value, what do you conclude?

Answer 78

There is greater than 5% probability that the correlation is due to chance. Therefore ACCEPT the null hypothesis; there is no statistically significant correlation between variable 1 and variable 2.

Question 79

If the is greater than the critical value, what do you conclude?

Answer 79

There is less than 5% probability that the correlation is due to chance. Therefore REJECT the null hypothesis; there is a statistically significant correlation between variable 1 and variable 2.