chapter 11 p1

Question 1

biodiversity

Answer 1

the variety of living organisms present in an area.
Biodiversity includes plants, animals, fungi, and other living things.

Question 2

The importance of biodiversity:

Answer 2

Biodiversity is essential in maintaining a balanced ecosystem for all organisms.
All species are interconnected - they depend on one another.
For example, trees provide homes for animals.
Animals eat plants, which in turn need fertile soil to grow.
Fungi and other microorganisms help decompose dead plants and animals, returning nutrients to the soil.
In regions of reduced biodiversity, these connections may not all be present, which eventually harms all species in the ecosystem.
We rely on balanced ecosystems as they provide us with the food, oxygen and other materials we need to survive.
Unfortunately, many human activities, such as farming and clearing land for housing, can lead to a reduction in biodiversity.

Question 3

Measuring biodiversity

Answer 3

Tropical, moist regions (that are warm all year round) have the most biodiversity.
The UK’s temperate climate (warm summers and cold winters) has less biodiversity.
Very cold areas such as the Arctic, or very dry areas such as deserts, have the least biodiversity.
Generally, the closer a region is to the Equator (the line of latitude of the Earth, halfway between the North Pole and South Pole), the greater the biodiversity.
For example, over 40000 plant species live in the Amazon rainforest, whereas less than 3000 live in Northern Canada.

Question 4

How does Measuring biodiversity plays an important role in conservation:

Answer 4

It informs scientists of the species that are present, thus providing a baseline for the level of biodiversity in an area.
From this information, the effect of any changes to an environment can be measured.
These may include the effect of human activity, disease or climate change, for example.
Before a major project is undertaken, such as building a new road or the creation of a new nature reserve, an Environmental Impact Assessment (EIA) is undertaken.
This assessment attempts to predict the positive and negative effects of a project on the biodiversity in that area.

Question 5

Biodiversity can be studied at different levels:

Answer 5

habitat biodiversity
Species biodiversity
genetic biodiversity.

Question 6

Habitat biodiversity:

Answer 6

Habitat biodiversity refers to the number of different habitats found within an area. Each habitat can support a number of different species.
Therefore in general, the greater the habitat biodiversity, the greater the species biodiversity will be within that area.
The UK is home to large number of habitat types, including meadow, woodland, streams, and sand dunes. It has a large habitat biodiversity.
By contrast Antarctica, covered almost entirely by an ice sheet, has a very low habitat biodiversity and very few species live in this region.
On a smaller scale, countryside that is habitat rich, perhaps with a river, woodland, hedgerows and wild grassland, will be more species rich than farmed countryside with large ploughed fields making up a single uniform habitat.

Question 7

Species biodiversity:

Answer 7

Species biodiversity has two different components:
species richness
species evenness

Therefore an area can differ in its species biodiversity even if it has the same number of species.
For example, a cornfield and a grass meadow may both contain 20 species.
However, in the cornfield, corn will make up 95% of the community with the remaining 5% made up of other organisms including weed plants, insects, mice, and birds.
In the grass meadow the species will be more balanced in their populations.

Question 8

species richness

Answer 8

the number of different species living in a particular area,

Question 9

species evenness

Answer 9

a comparison of the numbers of individuals of each species living in a community. (The community is all the populations of living organisms in a particular habitat.)

Question 10

Genetic biodiversity:

Answer 10

Genetic biodiversity refers to the variety of genes that make up a species. Humans have about 25000 genes, but some species of flowering plants have as many as 400000 genes.
Many of these genes are the same for all individuals within a species. However, for many genes, different versions (alleles) exist.
This leads to genetic biodiversity within a species
Genetic biodiversity within a species can lead to quite different characteristics being exhibited.
For example, some genes are the same for all breeds of dog - these genes define the organism as a dog.
Some of the genes have many alleles - they code for the wide variation in characteristics seen between different breeds of dog. for example coat colour and length.
Greater genetic biodiversity within a species allows for better adaptation to a changing environment, and is more likely to result in individuals who are resistant to disease.

Question 11

What is sampling:

Answer 11

• taking measurements of a limited number of individual organisms present in a particular area.
• Sampling can be used to estimate the number of organisms in an area without having to count them all.
• The number of individuals of a species present in an area is known as the abundance of the organism.
• Sampling can also be used to measure a particular characteristic of an organism.
• For example, you cannot reliably determine the height of wheat by measuring one wheat plant in a farmer’s field.
• However, if you measure the height of a number of plants and then calculate an average.
• your result is likely to be close to the average height of the entire crop.
• After measuring a sample, you can use the results of the sample to make generalisations or estimates about the number of organisms, distribution of species or measured characteristic throughout the entire habitat.

Question 12

Sampling can be done in two ways

Answer 12

random and non-random:

Question 13

Random sampling

Answer 13

Random sampling means selecting individuals by chance. In a random sample, each individual in the population has an equal likelihood of selection, rather like picking names out of a hat.
To decide which organisms to study, random number tables or computers can be used.
You have no involvement in deciding which organisms to investigate.
For example, to take a random sample at a grass verge you could follow these steps:

Question 14

For example, to take a random sample at a grass verge you could follow these steps:

Answer 14

Mark out a grid on the grass using two tape measures laid at right angles.
Use random numbers to determine the x coordinate and the y coordinate on your grid.
Take a sample at each of the coordinate pairs generated.

Question 15

Non-random sampling

Answer 15

Non-random sampling is an alternative sampling method where the sample is not chosen at random.
It can be divided into three main techniques:
Opportunistic
Stratified
Systematic

Question 16

Opportunistic

Answer 16

this is the weakest form of sampling as it may not be representative of the population.
Opportunistic sampling uses organisms that are conveniently available.

Question 17

Stratified

Answer 17

some populations can be divided into a number of strata (sub-groups) based on a particular characteristic.
For instance, the population might be separated into males and females.
A random sample is then taken from each of these strata proportional to its size.

Question 18

Systematic

Answer 18

in systematic sampling different areas within an overall habitat are identified, which are then sampled separately.
For example, systematic sampling may be used to study how plant species change as you move inland from the sea.
Systematic sampling is often carried out using a line or a belt transect.
A line transect involves marking a line along the ground between two poles and taking samples at specified points, this can include describing all of the organisms which touch the line or distances of samples from the line.
A belt transect provides more information; two parallel lines are marked, and samples are taken of the area between the two lines.

Question 19

Reliability:

Answer 19

• A sample is never entirely representative of the organisms present in a habitat. This may be due to the following:
  Sampling bias
  Chance

Question 20

Sampling bias

Answer 20

the selection process may be biased.
This may be by accident, or may occur deliberately.
For example, you may choose to sample a particular area that has more flowers because it looks interesting.
The effects of sampling bias can be reduced using random sampling, where human involvement in choosing the samples is removed.

Question 21

Chance

Answer 21

the organisms selected may, by chance, not be representative of the whole population.
For example, a sample of five worms collected in a trap may be the five longest in the habitat.
Chance can never be completely removed from the process, but its effect can be minimised by using a large sample size.
The greater the number of individuals studied, the lower the probability that chance will influence the result.
Therefore the larger the sample size, the more reliable the result.

Question 22

Sampling animals:

Answer 22

The following techniques can be used to collect living animals for study later.
Remember, all living organisms must be handled carefully and for as short a time period as possible.
As soon as any sample animals have been identified, counted and measured if required, they must be released back into the habitat at the point they were collected.
A pooter
Sweep sets
Pitfall traps
Tree beating
Kick sampling

Question 23

A pooter

Answer 23

is used to catch small insects
By sucking on a mouthpiece, insects are drawn into the holding chamber via the inlet tube.
A filter before the mouthpiece prevents them from being sucked into the mouth.

Question 24

Sweep sets

Answer 24

used to catch insects in areas of long grass

Question 25

Pitfall traps

Answer 25

are used to catch small, crawling invertebrates such as beetles, spiders and slugs. A hole is dug in the ground, which insects fall into. It must be deep enough that they cannot crawl out and covered with a roof-structure propped above so that the trap does not fill with rainwater. The traps are normally left overnight, so that nocturnal species are also sampled.

Question 26

Tree beating

Answer 26

is used to take samples of the invertebrates living in a tree or bush. A large white cloth is stretched out under the tree. The tree is shaken or beaten to dislodge the invertebrates. The animals will fall onto the sheet where they can be collected and studied.

Question 27

Kick sampling

Answer 27

used to study the organisms living in a river. The river bank and bed is 'kicked' for a period of time to disturb the substrate. A net is held just downstream for a set period of time in order to capture any organisms released into the flowing water.

Question 28

Sampling plants:

Answer 28

Plants are normally sampled using a quadrat, which can also be used to pinpoint an area in which the sample of plants should be collected. Quadrats can also be used to sample slow-moving animals such as limpets, barnacles, mussels, and sea anemone two main types of quadrat: Point quadrat Frame quadrat

Question 29

Point quadrat

Answer 29

this consists of a frame containing a horizontal bar. At set intervals along the bar, long pins can be pushed through the bar to reach the ground. Each species of plant the pin touches is recorded

Question 30

Frame quadrat

Answer 30

this consists of a square frame divided into a grid of equal sections. The type and number of species within each section of the quadrat is recorded (Figure 4). Further details are given below. To collect the most valid representative sample of an area, quadrats should be used following a random sampling technique (as discussed in Topic 11.2, Types of sampling). To study how the presence and distribution of organisms across an area of land varies, the quadrats can be placed systematically along a line or belt transect.

Question 31

Measuring species richness:

Answer 31

Biodiversity species richness is a measure of the number of different species living in a specific area. You should use a combination of the techniques described above to try to identify all the species present in a habitat. A list should be compiled of each species identified. The total number of species can then be calculated. To enable scientists to accurately identify organisms, identification keys are often used. These may contain images to identify the organism, or a series of questions, which classify an organism into a particular species based on the presence of a number of identifiable characteristics.

Question 32

Measuring species evenness:

Answer 32

Biodiversity, species evenness refers to how close in numbers the populations of each species in an environment are. For example, 50 organisms are found living under a decaying log. Of these, 20 are woodlice, 15 are spiders, and 15 are centipedes - the community is quite evenly distributed between species. However, if the 50 insects comprised just 45 woodlice and 5 spiders, the community would be described as uneven.

Question 33

Using frame quadrats: p1

Answer 33

A frame quadrat is used to sample the population of plants living in a habitat. There are three main ways of doing this: Density Frequency Percentage cover

Question 34

Density

Answer 34

if individual large plants can be seen clearly, count the number of them in a 1m by 1m square quadrat. This will give you the density per square metre. This is an absolute measure, not an estimate as the following two methods.

Question 35

Frequency

Answer 35

this is used where individual members of a species are hard to count, like grass or moss. Using the small grids within a quadrat, count the number of squares a particular species is present in. For example, if clover is present in 65 out of 100 squares, the frequency of its occurrence is 65%. (Each square represents 1%.) Another commonly used quadrat contains 25 squares - in this case. each square represents 4% of the study area. Therefore if, during a sampling of grassland, eight quadrat squares contained buttercups, the frequency of occurrence would be 32%.

Question 36

Percentage cover

Answer 36

this is used for speed as lots of data can be collected quickly. It is useful when a particular species is abundant or difficult to count. It is an estimate by eye of the area within a quadrat that a particular plant species covers.

Question 37

Using frame quadrats: p2

Answer 37

For each approach, samples should be taken at a number of different points. The larger the number of samples taken, the more reliable your results. You should then calculate the mean of the individual quadrat results to get an average value for a particular organism per m2 (To calculate the mean value, sum the individual quadrat results, then divide by the number of samples taken). To work out the total population of an organism in an area that has been sampled, multiply the mean value per m2 by the total area. A Figure 5 An electronic tag is being fitted to this green sea turtle (Chelonia mydas). This is as part of a study to estimate population size