MRS JONES A-LEVEL BIOLOGY - Home



|Requirements per student*/group of students |Notes |

|0.5  m2 quadrats | |

|Two tapes each at least 25  m long | |

|Random number tables or random number generator | |

|Identification keys | |

|Clipboards with data recording sheets | |

|Pencils | |

|Clear plastic bags to cover the data sheets | |

|Students should be advised to wear suitable clothing for the weather. |Rainwear in wet weather |

| |Hats and sun cream in hot sunny weather |

|Water and snacks/lunch |Depending on how long the trip is |

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Safety

• Work in pairs.

• Be aware of weather conditions and dress accordingly.

• Be aware of dangers in the habitat.

Activity 31: Calculating species diversity

Student Worksheet

Activity 31: Calculating species diversity

Notes on procedure

• A preliminary survey of the area to be studied is advisable wherever possible. This will determine aspects of the study such as:

a) the exact area to be studied

b) the length of metre tapes required

c) how many stations can be reasonably sampled in an area

d) how many groups of students can be accommodated.

It will also help to identify the type of identification keys required and the type of data collection sheets to be prepared.

• The random sampling technique can be first explained and practised in the laboratory. Random tables or alternatives are required.

• Students will require help with identifying the species present in the habitat. Simple pictorial keys usually work best in the field as time is limited.

• The exact number of quadrats to be sampled will depend on the area of study.

• Students should be familiar with Simpson’s species diversity index and how to use the formula:

D = 1 – [( (n / N )2]

Questions

1. Give a reason why it is important to place the quadrats at random.

2. Describe how you could modify this method to determine species diversity along the line of succession on a sand dune. How might the species diversity change along such a line of succession?

3. Why is it more useful to record diversity rather than the number of species present?

4. What are the limitations of collecting data using random sampling?

5. What are the problems of collecting data in the field rather than in a laboratory?

Answers

1. Random sampling removes the influence of bias in sampling.

2. Species diversity of the line of succession on a sand dune can be measured by setting quadrats at regular intervals along a transect and recording the number of species in each quadrat and the number of individuals of each species, as before.

Species diversity should increase along this line of succession, from the harsh environment at the start, where species diversity will be low, to high species diversity further along the succession line, where environmental conditions are less harsh and more stable.

3. Number of species present can be misleading since some of the species may be present in extremely low numbers. Species diversity gives a value of species richness and species abundance. It may also indicate ecological stability.

(Please note that in a monoculture or extreme climax community which is very stable, species diversity tends to be low since one species dominates.)

4. Random sampling may miss trends or differences in an area or a habitat since random sampling is intended to give overall data. For example, one end of a field may be wetter than the other, which affects the distribution of organisms in that area.

5. Collecting data in the field is subject to a number of variables that cannot be controlled. These variables can only be accounted for and not systematically controlled. This inevitably casts some doubt on the data collected. Environmental conditions are the most influential variables; however, interaction, competition and predation may also influence data.

From the examiner

• Species diversity gives a measure of the success of a species in a habitat.

• A high value of Simpson’s index indicates adverse habitat- a place for many different species to live- it is stable. A low value indicates a habitat dominated by a few species. This has low stability and a small change to the environment causes damage or destroys the whole habitat.

1.

Teacher Worksheet

Safety

• Work in pairs.

• Be aware of weather conditions and dress accordingly.

• Be aware of dangers in the habitat.

1.

Diagram

Table 1: For each quadrat

|Species |No. of individuals|n/N |(n/N)2 |1-[((n/N)] |

|A | | | | |

|B | | | | |

|C | | | | |

|D | | | | |

|N = |1-[( (n/N)2 ]= |

Results/conclusion

Procedure

1. Choose the area to be studied and set down the two tapes at right angles to each other. The exact length of each tape to be used is dependent on the area available – your teacher will advise you.

2. Choose coordinates by selecting pairs of numbers from the random number table. The first number of each pair is the x-coordinate which will be read along the horizontal metre tape. The second number is the y-coordinate to be read along the vertical tape.

3. Place the quadrat so the lower left corner is positioned as closely as possible to the chosen coordinate.

4. Identify all the species within the quadrat and record the number of each species present in a suitable table.

5. Repeat sampling using the random number coordinates for approximately 15 quadrats.

6. Record the total number of organisms for each species found.

• This value for each species is = n

• Add the total number of all the species found, this is = N

7. Calculate the species diversity (D) using the formula:

D = 1- [( (n / N)2 ]

8. Table 1 (opposite) could be copied for each quadrat. The number of r N

Calculate the species diversity (D) using the formula:

D = 1- [( (n / N)2 ]

Table 1 (opposite) could be copied for each quadrat. The number of rows can be increased, depending on the number of species present.

.

Equipment/materials

• 0.5  m2 quadrats

• Two tapes each at least 25  m long

• Random number tables or random number generator

• Identification key

• Clipboard with data sheets and a pencil

Objective

• To determine species diversity in a habitat using random sampling

• To calculate the species diversity index

From the examiner

• A high value indicates that many species live there. An environmental change may alter one species but the effect on the whole habitat is small.

• A low value indicates a few species dominate. This has low stability and a small change to the environment causes damage or destroys the whole habitat.

Objective

• To determine species diversity in a habitat using random sampling

• To calculate the species diversity index

Technician Worksheet

Activity 31: Calculating species diversity

Safety

Objective

• To determine species diversity in a habitat using random sampling

• To calculate the species diversity index

Notes

If possible, carry out a preliminary check of the area by both teacher and technician to identify any potential problems and also possible species for study.

Students will require access to suitable keys or identification sheets for the area being studied.

Health and Safety:

• Students must always work in pairs to limit potential dangers.

• Give sensible warning of weather conditions and advise on appropriate clothing and behaviour to suit the conditions.

• Warn of any dangers in the habitat surroundings.

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Practical activities have been checked for health and safety advice by CLEAPSS. All users will need to review the risk assessment information and may need to adapt it to local circumstances.

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© Pearson Education Ltd 2008

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