6 Permeability

It is important to distinguish clearly between porosity and permeability. Porosity is a measure of how much water can be stored in a rock, whereas permeability is a measure of the properties of a rock which determine how easily water and other fluids can flow through it (see Section 4). Permeability depends on the exte
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8.6 Line spectra: Activity 8 Quasar redshifts

Activity 8: Quasar redshifts

Read Peterson section 1.3.5 (pages 16 and 17) by clicking the link below.

1.4 The invisible Sun

Figure 7 shows an image of the Sun, taken when a huge prominence was visible (bottom left). The image was recorded using instruments that are sensitive to ultraviolet radiation rather than visible light, so the colours that you see are ‘false’. They simply indicate different levels of intensity of ultraviolet radiation. The u
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9 Wildebeest migration

The skill of thinking in a scientific way is as much a part of being a scientist as is knowing facts – perhaps more so. In this series of units, you'll not only come across facts about particular techniques, such as radio transmitters and bat detectors, but also the tactics that scientists use to inves
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8.3 Shortage of minerals

You may be familiar with salt licks that are provided for domesticated cattle. In the wild, grass is also often low in minerals (e.g. it has almost no sodium and very little calcium), so grazers may have to go to extraordinary lengths to supplement their diet with additional minerals obtained from the most unlikely places. LoM gives some examples, but the most impressive activity takes place in the caves of Mount Elgon in Kenya [pp. 113–114]. You'll probably recall this spectacular footage
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7 Plant defences

Activity 5

Watch the ‘Plant Predators’ programme from 05.03–12.07 and make notes in answer to the following questions.

(a) In what ways do plants shown in this sequence protect themselves against their predators?

(b) H
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5.2 Pseudo-ruminants

Animals in the third suborder of the Artiodactlya, the pigs, peccaries and (according to most authorities) the hippopotamuses (suborder Suina), use a slight variant on the ruminant method, and are often referred to as pseudo-ruminants. You might like to add this information to your version of Table 2. These animals do have st
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4.2 Digesting cellulose

Figure 3 in this section contains a lot of information and many terms that are probably new to you. Set aside the detail for the moment, read
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2 The herbivore lifestyle – living on leaves

Leaves are a much less nutritious food than most kinds of animal material, so large herbivores have to eat large quantities of plants and they have special ways to digest their food. As author David Attenborough (DA) says, ‘Leaves are extremely poor food’ [p. 89]. To find out why living on a diet of leaves is particularly difficult, we need to know something about how leaves work.


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5.2 Differences between the sexes

In biology, ‘sex’ refers to a particular form of reproduction, sexual reproduction, that is distinct from asexual reproduction. As you know, sexual reproduction involves the production of eggs by females and sperm by males; eggs (or ova) and sperm are known as gametes. It is a universal feature of mammalian biology that in sexual reproduction there are two types of gametes and that progeny are produced by the fusion of two unlike gametes to form a single cell called the zygote. The zygote
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3.1 Water distribution and usage issues

People in many parts of the world currently face a chronic shortage of water. This is a developing crisis that is expected to get worse. As you read in Section 1, several factors underlie this dire prediction. In addition, climate change is expected to cause major changes in the distribution of freshwater. The uneven distribution of freshwate
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3.8.1 Standard deviation: finding how reproducible a series of measurements are

Even if we know the maximum and minimum and middle values in a group of numbers, we still don't have a clear idea about the distribution of values within that range: are most of the values all bunched up at one end or spread evenly across the results?

For instance, if I count my pulse rate on the hour every hour, nine times over the course of a day, I might get the following values for the number of beats per minute (bpm): 61, 59, 60, 62, 60, 100, 59, 63, 61. The average result is 65 bp
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3.6.3 Exponential decrease: radioactive decay

The most familiar example of exponential decrease is provided by radioactive decay. Radioactivity is a natural phenomenon that is used routinely in many medical applications, from imaging (radioactive tracers in PET scanning) to therapy (radiotherapy to destroy tumours). During radioactive decay, the number of radioactive atoms halves at a constant rate, called the half-life. For instance, the radioactive isotope 11C, pronounced ‘carbon 11’, has a half-life of 1224 seconds (a l
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3.6.1 Radioactivity and bugs!

Many natural processes involve repeated doublings or halving at regular intervals. You may have come across this already in your work, in the context of bacterial growth or radioactivity. In this section, we are going to look in more detail at bacterial growth and radioactivity and we will be using graphs to examine how the numbers of bacteria or numbers of radioactive atoms change over time.


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Questions relating to Figure 11

The following OD450 values were measured from serum samples taken from three babies: 0.12, 0.40, and 1.74.

Self-assessment Question 3

3.9 Moon41: Apollo 15 station 2

The panorama was collected by James B. Irwin at Station 2. David Scott is to the left of the rover. He is examining a boulder. The large hill to the left of the rover is the summit of Mt. Hadley Delta. (QuickTime, 400KB, note: this may take some time to download depending on your connection speed)

8 Multiple plate collisions and the end of the Iapetus Ocean

The document attached below includes the eighth section of Mountain building in Scotland. In this section, you will find the following subsections:

  • 8.1 Introduction

  • 8.2 Palaeocontinental reconstructions

    • 8.2.1 The global view

    • 8.2.2 A model for the closure of the Iapetus Ocean

    • 8.2.3 Summary of Section 8.2

  • 8.3 Tectonics of the Northe
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12.6 Distance cues

There are two main cues available that allow us to judge the distance to a sound source. The first of these is the sound pressure level. Sound pressure level drops by 6 dB each time the distance that a sound travels doubles. In other words, if the sound pressure level of a sound is 60 dB SPL when its source is 1 m from you, then it will be 54 dB SPL if you move back another metre so that you are now 2 m away from its source. Therefore lower sound pressure levels indicate a greater distance. A
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11.5 Summary of sections 8 to 11

In these sections we have described some of the quantitative relationships between the physical dimensions of simple sounds and their subjective psychological dimensions. The physical dimension of intensity, or pressure amplitude, given in decibels (dB), directly affects loudness. Frequency of pressure changes, in hertz (Hz), mainly determines pitch.

The lowest threshold value and hence the maximal sensitivity for humans is in the region of 3000 Hz.

The quantitative relationship b
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7.1 The ascending auditory pathway

Up till now we have dealt with the anatomy of the auditory periphery and how the basic attributes of sound are coded within the auditory periphery. A great deal of additional processing takes place in the neural centres that lie in the auditory brainstem and cerebral cortex. Because localisation and other binaural perceptions depend on the interaction of information arriving at the two ears, we need to study the central auditory centres, since auditory nerves from the two cochleae interact on
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