Chapter 10 - The Adaptation of Organisms Flashcards
1
Q
How is the polar bear adapted for life in polar regions?
A
White colouration for camouflage.
Thick fur for insulation.
Small ears and a short tail to further reduce heat loss.
The ability to swim considerable distances between ice floes when hunting seals.
Excellent sense of smell to detect their prey.
2
Q
The polar bear is ideally adapted for life in polar regions, an environment which is …
A
Hostile to the vast majority of species on Earth.
3
Q
The polar bear occupies a habitat …
A
Atypical for mammals (most mammals are found in more temperate or warmer areas)
4
Q
What are the three different types of adaptation?
A
Behavioural
Physiological (biochemical)
Morphological (physical)
5
Q
Give an example of a behavioural adaptation of polar bears
A
It’s ability to stalk seals and knowing where and when to smash through a thick layer of ice to locate its prey.
6
Q
Give an example of a morphological (physical) adaptation of polar bears
A
Thick white fur
7
Q
Give an example of a physiological adaptation of polar bears
A
Polar bears often have to go months without food and at this time their metabolic rate can drop to a much lower level - a physiological (biochemical) adaptation that conserves energy.
8
Q
What type of factors influence the distribution of organisms?
A
Ecological factors
9
Q
What are the three types of ecological factors?
A
Climatic
Edaphic (soil)
Biotic
10
Q
Name some climatic factors
A
- Temperature range
- Availability of water
- Light intensity
- Light quality
- Day length
11
Q
Explain why temperature range, a climatic factor, influences the distribution of organisms
A
- As environmental temperatures usually vary (often considerably) many species are adapted to live within a temperature range.
- For different species the relevant range in temperature can be seasonal or even diurnal (difference between the hottest part of the day and the coldest part of the night).
- High temperatures will denature enzymes and in very low temperatures water will turn to ice inside cells, which can physically damage them.
- Most species of life on Earth live within particular latitudes, defined by the temperatures that exist there.
12
Q
Explain why water availability, a climatic factor, influences the distribution of organisms
A
- Water is essential for life and very few organisms are adapted to live in environments that are effective water free such as hot deserts.
- Some species of plant, such as hydrophytes, are adapted for living in water and others, such as xerophytes, are adapted for living in areas where there is little water or water retention by the soil is limited, such as marram grass on sand dunes.
- Mammals have a waterproof skin and a gas exchange surface that lies deep within the body, therefore they are protected from loss of water by evaporation to some extent.
- Consequently, they are able to exploit terrestrial habitats more successfully than many other animal groups.
13
Q
Explain why light intensity, a climatic factor, influences the distribution of organisms
A
- Light is necessary for photosynthesis, so all plants and ultimately most life on Earth is dependent on it.
- In general, the more light the faster the rate of photosynthesis and the faster the rate of growth.
- However, some species are highly adapted for living in low light environments.
- For example, many permanent cave-dwelling animals have evolved an excellent sense of smell and have lost the sense of sight.
- Light intensity has a significant effect on the distribution of most plant species; some require high light levels and others relatively low levels.
- Most water plants either grow close to the shore where light can penetrate through the shallow water or float on the surface layers in deeper water.
14
Q
Explain why light quality, a climatic factor, influences the distribution of organisms
A
- Plants can only use certain wavelengths of light for photosynthesis, so light quality (the wavelength it contains) is as important as intensity.
- This is particularly important in some species of seaweed that live in deeper water.
- Red light is rapidly absorbed in water so blue light tends to penetrate to the deeper depths.
- Species of ‘red’ seaweeds tend to occur in a zone around and below the low tide mark.
- They have a greater proportion of their light-absorbing pigments as red pigments, which absorb at the blue end of the spectrum.
- This adaptation allows the red seaweeds to dominate a zone inhospitable to most other seaweeds.
15
Q
Explain why day length, a climatic factor, influences the distribution of organisms
A
- Longer day length means more light available for photosynthesis and therefore greater growth.
- In many ecosystems there is a close correlation between day length and temperature.
- The length of the day is also crucial for those species whose activity is limited to either day or night.
- For example, nocturnal feeders have only a short feeding window in Britain in mid-summer.
16
Q
What are the two most important climatic factors?
A
Temperature range
Day length
17
Q
Temperature range and day length are considered to be the two most important climatic factors. Why?
A
As they tend to have an overriding and geographically widespread influence on plant and animal distribution.
18
Q
Why are edaphic (soil) factors important at the local level?
A
As small changes in soil chemistry or water content can influence species distribution and number over very short distances.
19
Q
Typically, edaphic factors have a much greater effect on …
A
Plant species than animal species, but the two are often interlinked because animal distribution is frequently influenced by the distribution of the plant species they need for food or shelter.
20
Q
Name some edaphic (soil) factors
A
- pH values
- Availability of nutrients
- Water content
- Aeration of soils
21
Q
Explain why pH, an edaphic factor, influences the distribution of organisms
A
- Soil pH affects the availability of certain ions and this availability often influences the range of plant species that can grow.
- The optimum pH for most plants is around neutral, with a smaller number of species adapted for acidic or alkaline conditions.
- Plants adapted for habitats with limestone or chalk-rich soils normally have an alkaline pH optimum.
22
Q
Explain why the availability of nutrients, an edaphic factor, influences the distribution of organisms
A
- Macronutrients such as nitrate (for amino acids) and calcium (for cell wall formation) are required by plants in relatively large amounts.
- Micronutrients are ions that are required in very small amounts, but nonetheless can be critical in plant distribution.
- The availability of the nutrients depends on a number of factors, including the parent rock from which the soil has been formed and the ecosystem.
23
Q
Explain why water content, an edaphic factor, influences the distribution of organisms
A
- The water content of the soil has a major influence over plant distribution.
- Most British plant species are adapted for moist but well drained soils, with smaller numbers of highly adapted species favouring either water logged or very dry soils (xerophytes).
- Waterlogged soils often have very low oxygen levels, which restricts aerobic respiration in the root cells.
- Waterlogged soils often have reduced nitrate levels due to denitrification (most common in waterlogged conditions) converting the nitrate to atmospheric nitrogen.
- The zonation of plant species on a river bank is often due to gradients of water availability.
24
Q
Explain why aeration of soils, an edaphic factor, influences the distribution of organisms
A
- Most soils contain air in the spaces between the soil crumbs.
- Much of the oxygen diffuses into the cells in the plant roots and is used in respiration.
- Most soil microbes involved in the decomposition of organic matter also require oxygen.
- Peat bogs are formed from plant matter (usually rich in mosses) that has not decayed for a number of reasons, including the fact that they are waterlogged and acidic, conditions that restrict the activity of microbes.
25
Name some biotic factors
1. Competitors
2. Predators and prey
3. Accumulation of waste
26
In addition to climatic and edaphic factors, the distribution of plant and animal species is influenced by ...
The activities of other living organisms, whether as competitors or being a predator or prey of the organism concerned.
27
In addition to climatic and edaphic factors, the distribution of plant and animal species is influenced by the activities of other living organisms, whether as competitors or being a predator or prey of the organism concerned. These factors can be grouped as ...
Biotic factors
28
Explain why competition, a biotic factor, influences the distribution of organisms
* Organisms compete with one another for any resource that is in limited supply.
* The general principle of competition is that some win and others lose out.
* Young chicks compete for their mother's attention and the food that this will bring, with the weaker ones often losing out at the expense of the stronger ones.
* Only some of the young oak seedlings at the base of the parent tree survive, as they compete for light, space, water and ions.
* While other factors such as grazing and trampling can have an effect, it is the competition among the seedlings (and with the parent tree) that ultimately determines that the vast majority of seedlings will not survive to maturity.
* This type of competition, where organisms of the same species are competitions, is intraspecific competition.
* Interspecific competition is where organisms of different species are competing for a resource, for example, a range of species of scavengers feeding off a dead carcass or different plant species competing for light on the woodland floor.
29
Explain why predators and prey, a biotic factor, influences the distribution of organisms
* Numbers of predator and prey are influenced by the numbers of each other.
* When prey numbers are high, predator numbers are often high and the converse applies, with a fall in prey numbers often resulting in a fall in the number of predators.
* This is particularly true when a predator has only one main species of prey.
* Typically, a graph showing the number of prey animals in a population and the number of predators follows the pattern in the graph below. (Textbook page 182)
30
What does the term ecological niche mean?
The term ecological niche describes an organism's role within the ecosystem. This includes its role in the food chain, it's climatic and (if relevant) edaphic requirements, and its competition with other organisms.
31
Give an example of a macronutrient
Nitrate (for amino acids)
| Calcium (for cell wall formation)
32
What are macronutrients?
Macronutrients are ions required by plants in relatively large amounts
33
What are micronutrients?
Micronutrients are ions required by plants in relatively small amounts.
34
The availability of nutrients depends on ...
A number of factors, including the type of parent rock from which the soil has been formed and the ecosystem.
35
What is intraspecific competition?
Organisms of the same species compete for a resource.
36
What is interspecific competition?
Organisms of different species compete for a resource.
37
Give two examples of interspecific competition
A range of species of scavengers feeding off a dead carcass.
Different plant species competing for light on the woodland floor.
38
Draw a graph showing the numbers of predator and prey animals in a population over time
Textbook page 182
39
Case study: wild garlic
| What is wild garlic?
Common plant occurring in deciduous woodlands (for example, oak, ash and beech) with moist soils throughout most of lowland British Isles.
The species overwinters as a bulb within the soil and new leaves emerge through the soil in February/March to make use of the increasing light levels on woodland floors before the tree canopy closes.
By the time the tree canopy closes (May), the wild garlic plants will be in flower. The flowers and other above ground parts of wild garlic are largely decomposed by July.
40
Case study: wild garlic
Wild garlic is a common plant occurring in deciduous woodlands (for example, oak, ash and beech) with moist soils throughout most of lowland British Isles.
The species is particularly common in ...
The wetter western parts of the British Isles, for example, Northern Ireland, the islands and the western coastal regions of Scotland, Cornwall and Devon.
41
Case study: wild garlic
Wild garlic is a common plant occurring in deciduous woodlands (for example, oak, ash and beech) with moist soils throughout most of lowland British Isles.
The species is particularly common in the wetter western parts of the British Isles, for example, Northern Ireland, the islands and the western coastal regions of Scotland, Cornwall and Devon. Why?
These areas give it the appropriate temperature ranges and water availability.
42
Case study: wild garlic
| Wild garlic grows particularly well on ...
Nutrient-rich woodland soils with a pH value around neutral
43
Case study: wild garlic
| Wild garlic grows particularly well on nutrient-rich woodland soils with a pH value around neutral. It favours ...
Nitrate-rich soils (the main macronutrient required) which are necessary to provide the minerals required for the rapid rate of growth in late February/ early March, ensuring that the plant is mature enough to benefit from the high light intensities and increasing day length at this time.
44
Case study: wild garlic
| High rainfall levels ensure that ...
The plants have moist soil
45
Case study: wild garlic
| Although high rainfall levels ensure that the plants have moist soil, they cannot grow in ...
Waterlogged soil
46
Case study: wild garlic
Although high rainfall levels ensure that the plants have moist soil, they cannot grow in waterlogged soil. The bulbs cannot survive if ...
The ground is waterlogged, and therefore not aerated, for too long a period of time.
47
Case study: wild garlic
| Wild garlic grows in ...
Dense colonies with very few other plants present (during the particular stage of year.
48
Case study: wild garlic
Both the photographs on page 183 of the textbook emphasise that wild garlic grows in dense colonies with very few other plants present in the habitat at this stage of the year. Why is this?
As the wild garlic is able to out compete other potential competitors.
49
Case study: wild garlic
Both the photographs on page 183 of the textbook emphasise that wild garlic grows in dense colonies with very few other plants present in the habitat at this stage of the year. This is because the wild garlic is able to out-compete other potential competitors. How does it do this?
It grows in very high densities where conditions are favourable, through a combination of a high output of seeds per plant and extensive asexual reproduction through the production of daughter bulbs.
50
Case study: wild garlic
| Wild garlic is virtually unique in that ...
It can grow in very low light intensities
51
Case study: wild garlic
| Wild garlic is virtually unique in that it can grow in very low light intensities, such as ...
The light levels found at the edges and partially under rhododendron trees.
52
Case study: wild garlic
Wild garlic is virtually unique in that it can grow in very low light intensities, such as the light levels found at the edges and partially under rhododendron trees. The plants can do this because they are ...
Highly adapted
53
Case study: wild garlic
| How is wild garlic adapted for growing in low light intensities?
They have the ability to develop very thin leaves in low light intensities.
They wild garlic can develop a thinner cuticle (to compensate for the low evaporation rates in the dense shade).
The cuticle can also be thickened into microscopic 'pyramid' structures. These structure have optical properties that allow them to concentrate and refract light onto the palisade layer below, including the light that reaches the leaf at a very low angle - light that in most leaves would be subject to reflection and be lost to the leaf.
54
Case study: wild garlic
| The presence of pyramid structures on the cuticles of wild garlic leaves is what type of adaptation?
Morphological
55
Case study: wild garlic
The ability of the pyramid structures on the cuticles of wild garlic leaves to concentrate and refract light is what type of adaptation?
Physiological
56
Case study: wild garlic
The flexibility that allows each wild garlic plant to be able to develop a cuticle appropriate to its needs may be regarded as what type of adaptation?
Behavioural
57
Practical work
| You are expected to be familiar with ...
A range of qualities and quantitative techniques used to investigate the distribution and relative abundance of plants and animals in a habitat.
58
Practical work - sampling
| It is normally not possible, or at least not efficient, to ...
Count all the individuals of one or a range of species in a habitat.
59
Practical work - sampling
It is normally not possible, or at least not efficient, to count all the individuals of one or a range of species in a habitat. Instead, the habitat is usually ...
Sampled
60
Practical work - sampling
It is normally not possible, or at least not efficient, to count all the individuals of one or a range of species in a habitat. Instead, the habitat is usually sampled to ...
Gain an accurate estimate of plant or animal species numbers, or their distribution.
61
Practical work - sampling
It is normally not possible, or at least not efficient, to count all the individuals of one or a range of species in a habitat. Instead, the habitat is usually sampled to gain an accurate estimate of plant or animal species numbers, or their distribution.
There are several ways to estimate the amount, or abundance, of organisms present. When sampling, the abundance of organisms can be estimated in terms of:
1. Density
2. Percentage cover
3. Frequency
62
Practical work - sampling
| When sampling, the abundance of organisms can be estimated in terms of density. What is density?
* The number of individuals present per quadrat.
* Frame (square) quadrats are often used in sampling to determine density.
* Density is a useful indicator for many animals but is not suitable for many plant species, as it is often difficult to know where one plant starts or ends, for example, grass plants.
63
Practical work - sampling
| When sampling, the abundance of organisms can be estimated in terms of percentage cover. What is percentage cover?
* Mainly used for plants.
* This gives an estimation of the percentage area of the quadrat covered by a plant species.
* As it is impossible to be very precise when estimating percentage cover, the estimated percentage cover is usually rounded to the nearest 10%.
* An exception is that a value of 1% is given to indicate the presence of a species in a quadrat where it has less than 5% cover (and so would be rounded down to 0% unless the 1% value is used).
[Go to textbook page 184 for a diagram]
64
Practical work - sampling
| When sampling, the abundance of organisms can be estimated in terms of frequency. What is frequency?
* At each sampling point (for example, quadrat) each species is recorded as being present or absent.
* Thus % frequency indicates the percentage of all quadrats or sampling points that a species occurs in.
* A pin frame (point quadrat) is a sampling device that has a number of large pins that can be lowered onto the ground; pin frames are often used when recording frequency.
* For each pin, a species is recorded as being present only if he pin makes contact with that species.
* When using a pin frame a frequency of 5% indicates that 5% of the pins used in the sampling process touched the species concerned.
Note: a number of different plant species can be recorded present at a particular pin (point) if the pin touches a number of different plants.
[Textbook page 184 diagram on pin frame]
65
What equipment is used in sampling to determine density and percentage cover?
Frame (square) quadrats
66
What equipment is used in sampling to determine frequency?
Pin frame (point quadrat)
67
How can a number of different plant species be recorded present at a particular pin (point)?
If the pin touches a number of different plants.
68
Practical work - Mechanisms of sampling
| What are the two types of sampling?
Random
| Systematic
69
Practical work - Mechanisms of sampling
| It is important to use (blank) during sampling.
An appropriate number of quadrats (sample size)
70
Practical work - Mechanisms of sampling
| It is important to use an appropriate number of quadrats (sample size) during sampling. Too few will ...
Not give a representative (reliable) value
71
Practical work - Mechanisms of sampling
It is important to use an appropriate number of quadrats (sample size) during sampling. Too few will not give not give a representative (reliable) value and too many will ...
Defeat the purpose of sampling.
72
Practical work - Mechanisms of sampling
| When should random sampling be used?
If the area to be sampled is uniform or if there is absence of any clear pattern in species distribution.
73
Practical work - Mechanisms of sampling
| What are the aims of random sampling?
Random sampling avoids bias and ensures that the sample is representative.
Aims of random sampling:
1. Eliminate bias.
2. Reduce the effects of chance.
3. Minimise errors in obtaining measurements/samples.
4. Ensures that the sample is representative.
74
Practical work - Mechanisms of sampling
If the area to be sampled is uniform or if there is absence of any clear pattern in species distribution, then random sampling should normally be used.
Random sampling avoids bias and ensures that the sample is representative. How is this achieved?
By dividing the area to be sampled into a grid using tapes at right angles to each other and then generating random numbers to define the co-ordinates of the positions to place the quadrats. Typically the bottom left hand corner of the quadrat is placed at the point of the random co-ordinate.
Another variation in random sampling is to place a (master) tape along the edge of the area to be sampled and place other tapes at right angles to the master tape
[See diagrams in textbook page 185]
75
Practical work - Mechanisms of sampling
| In certain conditions sampling should not be ...
Totally random
76
Practical work - Mechanisms of sampling
| In certain conditions sampling should not be totally random but should be ...
Systematic
77
Practical work - Mechanisms of sampling
In certain conditions sampling should not be totally random but should be systematic. When should systematic sampling be used?
When there appears to be zonation/clear transition from one habitat type to another in the distribution of species.
78
Practical work - Mechanisms of sampling
In certain conditions sampling should not be totally random but should be systematic. Systematic sampling should be used when there appears to be zonation/clear transition from one habitat type to another in the distribution of species. Give three examples of when this may occur.
Up a river bank
From a woodland edge to the centre of the wood
Up a seashore
79
Practical work - Mechanisms of sampling
In certain conditions sampling should not be totally random but should be systematic. Systematic sampling should be used when there appears to be zonation/clear transition from one habitat type to another in the distribution of species, for example, up a river bank, from a woodland edge to the centre of the wood or up a seashore. In this situation the sampling is described as being ...
Along a line or transect
80
Practical work - Mechanisms of sampling
| What is a transect?
A line created with tape along which systematic sampling is performed.
81
Practical work - Mechanisms of sampling
| What are the three types of transect used in systematic sampling?
Line transect
Belt transect
Interrupted belt transect
82
Practical work - Mechanisms of sampling
| What is a line transect?
* Sampling either continually or at intervals (such as every 5 m) along a transect line, for example a tape.
* Only individuals actually touching the transect line are recorded.
83
Practical work - Mechanisms of sampling
| What is a belt transect?
* Sampling along a transect line using quadrats, typically placed end to end to each other (contiguously) so that the transect line is continually sampled from one end to the other.
* When using a belt transect it is important that the quadrat is always placed in the same side of the tape, with the investigator remaining on the other side. This prevents the trampling of plants that are part of the investigation.
84
Practical work - Mechanisms of sampling
| What is an interrupted belt transect?
* Sampling along a transect line using quadrats but the sampling is at intervals along the overall 'transect' due to the large distances involved.
* In effect, interrupted belt transects are a number of belt transects nested at intervals along an overall transect.
85
Practical work - Mechanisms of sampling
| When will an interrupted belt transect be appropriate?
Over large distances
E.g. When sampling a sand dune system from the seashore to a woodland edge immediately beyond the dune system, a distance that could be a kilometre or more.
86
Practical work - Mechanisms of sampling
| The method used to measure abundance in transects can depend on ...
The type of transect used.
87
Practical work - Mechanisms of sampling
The method used to measure abundance in transects can depend on the type of transect used. For example, frequency is commonly used for ...
Line transects
88
Practical work - Mechanisms of sampling
The method used to measure abundance in transects can depend on the type of transect used. For example, frequency is commonly used for line transects - it is obviously impossible to use (blank) for line transects.
Percentage cover
89
Practical work - Mechanisms of sampling
| What method for measuring the abundance of organisms can be used for line transects?
Frequency
90
What are the two types of abiotic factor?
Climatic
| Edaphic
91
Practical work - Biotic and abiotic factors
| In investigations of abundance or distribution it is usually appropriate to collect data on ...
At least some of the factors that affect plant (or animal) distribution.
92
Practical work
In investigations of abundance or distribution it is usually appropriate to collect data on at least some of the factors that affect plant (or animal) distribution. What are the two broad types of factor that affect plant and animal distribution?
Biotic
| Abiotic
93
Practical work - Biotic and abiotic factors
In investigations of abundance or distribution it is usually appropriate to collect data on at least some of the factors that affect plant (or animal) distribution. These factors can be abiotic or biotic.
What are abiotic factors?
Non-living or physical factors
94
Practical work - Biotic and abiotic factors
In investigations of abundance or distribution it is usually appropriate to collect data on at least some of the factors that affect plant (or animal) distribution. These factors can be abiotic or biotic.
Give some examples of abiotic factors
```
Soil moisture
Soil organic content
Soil temperature
Soil pH
Light intensity
```
95
Practical work - Biotic and abiotic factors
In investigations of abundance or distribution it is usually appropriate to collect data on at least some of the factors that affect plant (or animal) distribution. These factors can be abiotic or biotic.
Factors that relate to the soil are called ...
Edaphic factors
96
Practical work - Biotic and abiotic factors
In investigations of abundance or distribution it is usually appropriate to collect data on at least some of the factors that affect plant (or animal) distribution. These factors can be abiotic or biotic.
What are biotic factors?
Factors linked to living organisms
97
Practical work - Biotic and abiotic factors
In investigations of abundance or distribution it is usually appropriate to collect data on at least some of the factors that affect plant (or animal) distribution. These factors can be abiotic or biotic.
Give some examples of biotic factors
Competition from other organisms
Grazing
Predation
98
Practical work - Biotic and abiotic factors
In investigations of abundance or distribution it is usually appropriate to collect data on at least some of the factors that affect plant (or animal) distribution. These factors can be abiotic or biotic.
In practice, there can be an ...
Overlap between abiotic and biotic factors
99
Practical work - Biotic and abiotic factors
In investigations of abundance or distribution it is usually appropriate to collect data on at least some of the factors that affect plant (or animal) distribution. These factors can be abiotic or biotic.
In practice, there can be an overlap between abiotic and biotic factors. Give an example of when this may occur.
The light intensity at ground level in a wood is mainly affected by other living organisms, ie the tree canopy overhead.
100
Practical work - Biotic and abiotic factors
In investigations of abundance or distribution it is usually appropriate to collect data on at least some of the factors that affect plant (or animal) distribution. These factors can be abiotic or biotic.
In many ecological investigations involving plant abundance and distribution you are also asked to measure a small number of ...
Abiotic factors
101
Practical work - Biotic and abiotic factors
In investigations of abundance or distribution it is usually appropriate to collect data on at least some of the factors that affect plant (or animal) distribution. These factors can be abiotic or biotic.
In many ecological investigations involving plant abundance and distribution you are also asked to measure a small number of abiotic factors. What type of abiotic factors would you measure?
Edaphic factors
102
Practical work - Biotic and abiotic factors
In investigations of abundance or distribution it is usually appropriate to collect data on at least some of the factors that affect plant (or animal) distribution. These factors can be abiotic or biotic.
In many ecological investigations involving plant abundance and distribution you are also asked to measure a small number of abiotic factors, for example, a range of Edaphic factors. Why is this?
As for most plant species abiotic factors are more important than the biotic factors in determining abundance and distribution.
103
Practical work - Measuring abiotic factors
| What are some of the abiotic factors that can be measured in the field?
1. Soil moisture (water) content
2. Soil organic content
3. Soil pH
4. Soil temperature
5. Light intensity
104
Practical work - Measuring abiotic factors
| How can soil moisture (water) content be measured?
1. Collect a sample of soil using a soil auger
- A soil auger is an instrument that can 'bore' down into the soil, similar to a household drill
- When it is removed from the ground, a sample of soil can be removed from the 'curls'.
- This type of apparatus has the advantage of removing soil across a range of depths and not just at the surface.
2. Weigh a small sample of the soil and then place this sample in an oven and dry to a constant weight at 105°C.
3. The percentage soil moisture (water) content can be calculated using the formula:
(initial soil mass - soil mass after drying)
————————————————— X 100%
initial soil mass
105
Practical work - Measuring abiotic factors
- Measuring soil moisture (water) content
If there is a time delay between sampling the soil and testing for moisture content, it is important that the soil samples are ...
Stored in plastic bags (or other watertight containers)
106
Practical work - Measuring abiotic factors
- Measuring soil moisture (water) content
If there is a time delay between sampling the soil and testing for moisture content, it is important that the soil samples are store in plastic bags (or other watertight containers). Why is this?
As some of the moisture might evaporate before the measurement of the initial mass.
107
Practical work - Measuring abiotic factors
- Measuring soil moisture (water) content
Why is 105°C a suitable oven temperature to dry soil?
As the temperature is high enough to evaporate all the water but not high enough to burn off the humus (organic matter).
108
Practical work - Measuring abiotic factors
| How can soil organic content be measured?
• Firstly, carry out the procedure for measuring soil moisture (water) content.
1. Place the oven-dried soil in a porcelain container (crucible) and reweigh.
2. Use a Bunsen burner to burn off the organic content (humus).
3. It is important to mix the soil in the crucible at intervals to ensure that all the organic content is burnt.
4. Allow to cool, burn and reweigh to a constant mass.
5. The percentage organic content can be calculated using the formula:
(dry soil mass - soil mass after burning)
————————————————— X 100%
initial soil mass
Note 1: using the above formula gives the percentage organic content of the soil in a set of data that also includes soil moisture. If soil moisture measurements are not required, it is possible to use the formula:
(dry soil mass - soil mass after burning)
————————————————— X 100%
dry soil mass
This gives the percentage organic content after the moisture has been removed. Values obtained this way are often more meaningful as the percentage soil moisture can vary considerably over short periods of time and this will affect the soil organic content percentages.
109
Practical work - Measuring abiotic factors
- Measuring soil organic content
How can precision, accuracy, validity and reliability be improved in these types of investigations?
Precision can be increased by using a balance that can measure mass to two decimal places.
Accuracy is increased by transporting and storing soil samples in plastic bags; if accuracy is compromised, this affects the validity of the investigation.
Reliability can be improved by taking a number of soil samples and measuring the edaphic factors as required. Increasing reliability is very important as factors such as soil moisture can vary considerably over short distances and over time.
110
Practical work - Measuring abiotic factors
| How can soil pH be measured?
Soil pH can be measured using a soil testing kit (using indicator dyes) or using a pH electrode attached to a digital meter.
111
Practical work - Measuring abiotic factors
| How can soil temperature be measured?
* Soil temperature can be measured using thermometers.
* Normally in ecological investigations, special soil thermometers are used where the thermometer is encased and protected within a metal cover.
* To get accurate soil temperature readings, it is important that the thermometers are left long enough in the soil for them to equilibrate and the bulb should also be inserted to the same depth at different sampling points.
112
Practical work - Measuring abiotic factors
| What apparatus can be used to measure light intensity?
Light meter
113
Practical work - Measuring abiotic factors
- Measuring light intensity
Many light meters measure light intensity within ...
The waveband 400-700 nm
114
Practical work - Measuring abiotic factors
- Measuring light intensity
Many light meters measure light intensity within the waveband 400-700 nm, the wavelength range that can be used for ...
Photosynthesis
115
Practical work - Measuring abiotic factors
- Measuring light intensity
What wavelength range of light can be used for photosynthesis?
Light within the waveband 400-700 nm.
116
Practical work - Measuring abiotic factors
- Measuring light intensity
Light can be measured using a light meter. Many light meters measure light intensity within the waveband 400-700 nm, the wavelength range that can be used for photosynthesis, with the readings being expressed in ...
Wm-2
117
Practical work - Measuring abiotic factors
- Measuring light intensity
How can light intensity be measured?
1. Light intensity can be measured using a light meter.
2. Often relative light intensity (for example, the light reaching ground level in a particular habitat as a percentage of light reaching 'open' ground) is more meaningful.
3. Formula:
Light intensity at ground level for a sample point
————————————————————— X 100%
Light intensity in the open (no shade)
118
Practical work - Measuring abiotic factors
- Measuring light intensity
Give an example of when relative (percentage) light intensity is appropriate
When measuring the percentage (relative) light intensity at different sampling points in a transect running from grassland into a wood.
Turn to textbook page 188 for a diagram
119
Practical work - Measuring abiotic factors
- Measuring light intensity
At each particular sample point it is important that ...
A number of light readings are taken
120
Practical work - Measuring abiotic factors
- Measuring light intensity
It is important that a number of light readings are taken at a particular sample point as ...
Light intensity usually fluctuates significantly due to cloud cover changing.
121
Practical work - Measuring abiotic factors
- Measuring light intensity
It is important that a number of light readings are taken at a particular sample point, as light intensity usually fluctuates significantly due to cloud cover changing. It is also important to ...
Take all the light readings in a transect over a relatively short period of time
122
Practical work - Measuring abiotic factors
- Measuring light intensity
It is important that a number of light readings are taken at a particular sample point, as light intensity usually fluctuates significantly due to cloud cover changing. It is also important to take all the light readings in a transect over a relatively short period of time, as ...
Light intensity changes over time due to the position of the Sun in the sky changing throughout the day.
123
Practical work - Measuring abiotic factors
- Measuring light intensity
Ideally, light readings should be taken in ...
Full Sun rather than in cloudy conditions.
124
Practical work - Measuring biotic factors
- Sampling animals
Unlike plants, most species of animals are ...
Mobile and often difficult to see
125
Practical work - Measuring biotic factors
- Sampling animals
Unlike plants, most species of animals are mobile and often difficult to see due to ...
Them blending in with the background or their small size.
126
Practical work - Measuring biotic factors
- Sampling animals
Unlike plants, most species of animals are mobile and often difficult to see due to them blending in with the background or their small size. Therefore, simply counting the animals visible in a quadrat at any one time is ...
Seldom the appropriate method to use when estimating animal abundance.
127
Practical work - Measuring biotic factors
- Sampling animals
What equipment can be used to capture small animals in a particular habitat?
Pitfall traps
Sweep nets
Pooters
128
What is a pitfall trap?
1. Can be used to capture small animals that walk over the habitat surface, for example, woodland floor.
2. The pitfall traps are sunk into the soil in such a way that small animals, such as beetles and woodlice, will fall into them and cannot escape.
129
What are some of the precautions that need to be observed when using pitfall traps?
1. Ensure the trap is sunk sufficiently into the soil so that the edge does not protrude above ground level (otherwise small arthropods might walk around rather than into the trap).
2. Traps need to be checked on a regular basis (to prevent predation of trapped animals as far as possible).
130
Draw a diagram of a pitfall trap
* 'Lid' (eg flat stone) to keep rain out and reduce predation.
* Small stones.
* Container, eg plastic yoghurt pot inserted into ground.
Textbook page 189
131
What is a sweep net?
1. Can be used to sample arthropods in tall grass.
2. The sweep net is swept from side to side through the grass and as this happens small arthropods (usually mainly insects) are captured in the net.
3. When comparing different parts of a grassland, or different grasslands, it is important to be consistent in technique. For example, there should be a specific number of sweeps, such as 10, and the same size of net with same mesh size should be used.
132
What is a pooter?
1. Can be used to capture small insects for bringing back to the laboratory for identification and/or counting, for example, the small insects caught in a sweep net.
133
Draw a diagram of a pooter
* Rubber (replaceable) tip.
* Investigator sucks to create negative pressure at X.
* Gauze/membrane prevents investigator sucking up animal into mouth.
Textbook page 189
134
Practical work - Presenting the data
| Ecological data is usually recorded in ...
Tables
135
Practical work - Presenting the data
| Ecological data is usually recorded in tables and presented in ...
Graphs
136
Practical work - Presenting the data
| Ecological data is usually recorded in tables and presented in graphs. The actual type of graph used depends on ...
The data that is collected
137
Practical work - Presenting the data
Ecological data is usually recorded in tables and presented in graphs. The actual type of graph used depends on the data that is collected. For example, the percentage cover of a plant species along a belt transect could be represented by a ...
Line graph, a histogram or a kite diagram
138
Practical work - Presenting the data
Ecological data is usually recorded in tables and presented in graphs. The actual type of graph used depends on the data that is collected. For example, the percentage cover of a plant species along an interrupted belt transect could be represented by a ...
Bar chart
139
Knowledge check 40
| Explain what is meant by an adaptive feature
A feature (behavioural, physiological, etc.) that helps an organism survive in its habitat, breed and pass on its genes.
140
Knowledge check 41
| What are edaphic factors?
Edaphic factors are environmental factors that relate to the soil.
