3.2 Adaptation If you are working through the units in this series in sequence, you have already been introduced to the idea that many features of an animal's behaviour and structure are adaptations to their way of life. Unit S182_2 looked at the oily fur and the flipper-like feet of the water shrew, comparing the water shrew to the common shrew, a close relative that does not have these features and that does not chase prey under water. We also thought very carefully about the way that adaptations are desc
2.2 Cracking nuts and other ways of eating This section returns to the arrangement of teeth in the jaws of various mammals and uses the same representation for the dental formula as used in S182_2 Studying mammals: the insect hunters. You are not expected to remember the dental formulae of the various mammals. We can tell
1 The rodent As you work through this unit you will come across boxes, like this one, which give you advice about the study skills that you will be developing as you progress through the unit. To avoid breaking up the flow of the text, they will usually appear at the start or end of the sections. As well as the un Learning outcomes By the end of this unit you should be able to: explain the implications of a seed/nut-eating habit; suggest why rodents are a successful order of mammals; describe adaptation, based on knowledge of the theory of biological evolution by natural selection; explain how altruistic characteristics can be understood in terms of kin selection and inclusive fitness; give examples of the fitness costs and benefits associated wit 6.2 Opting out This last section of the unit contains, I think, some of the most challenging science that you have met so far. Take it slowly, translating all the abbreviations in your head as you come to them (read BAT as ‘brown adipose tissue’, for example) and looking carefully at the graph in Author(s): 5.3 Body size and surface area You will be using some more maths in this section. Remember that areas are measured in units such as m2, which is read as metres squared or, more usually, square metres. Volumes are measured in units such as m3, which you should read as metres cubed or, more usually, cubic metres. Most mea 5.1 Introduction If you have already worked through S182_1 Studying mammals: a winning design, you'll be aware (from Section 5) that animals break down their food for conversion into usable forms of energy; thus, breakdown of food is sometimes called (as in the commentary to the TV programme) the ‘internal fire’. Fire is a useful analogy because within the body, food is oxidised. This process is comparable to burning, but it is much, much slower and takes place in living tissue. Chemical energy rel 4 Thinking about adaptation Section 3 identified a range of adaptations in insect eaters, most linked with their mode of feeding. Particular structures are identified as having particular functions. But there are problems with the concept of adaptation if it's taken too far. Not all features of an organism have to be functional in ways that perfectly sui 3.4 Anteaters View ‘The Insect Hunters’ on the DVD from 22.40–26.54, which shows the giant anteater, and make notes on what you see. On the basis of your notes, what features of the giant anteater could be regarded as adaptations for 1 Meeting the insect eaters As you work through this unit you will come across boxes, like this one, which give you advice about the study skills that you will be developing as you progress through the unit. To avoid breaking up the flow of the text, they will usually appear at the start or end of the sections. As well as the unit t Introduction Sixty-five million years ago, animal and plant life were very different from nowadays, but there were rat-sized placental mammals living successfully on the ground. They were insect eaters, i.e. insectivores, feeding on the vast numbers of insects and other invertebrates living in soil, leaf litter and low-lying vegetation. Insectivore means ‘insect eater’, and in this unit we will explore the world of insect-eating mammals, classified together on the basis of a reasonably close evolution 7.4 Nuclear abundances as evidence for the big bang What we have seen is that a theoretical model based on the assumption that there was a big bang, and incorporating an assumption about the present-day value of the baryonic density, ρb,now, leads to definite predictions as to what the nuclear abundances must have been when the elements froze-out. This, therefore, provides us with a third way of checking out the big bang hypothesis: Do the present-day cosmic nuclear abundances agree with these predictions for any plausible v 7.3 The formation of light nuclei It is the very high temperatures that make the early stages of the big bang relatively simple to calculate. When it comes to the formation of the first nuclei, we are looking at a temperature that has dropped to about 109 K, this being achieved approximately 3 minutes after the instant of the big bang. For nuclei to form, the temperature must still be high enough that charged nuclei can approach each other closely – despite the electrostatic repulsion between their positive charg 7.2 The temperature of matter and radiation The different reactions by which neutrons and protons came together soon after the instant of the big bang to produce heavier nuclei will have proceeded at different rates according to the energies of the particles involved. The first step in calculating nuclear abundances is therefore to make some assumption about these energies. The particles at any instant have a wide range of energies; this obviously complicates matters. Fortunately, however, it is possible to make one very importan 6.3 Anisotropies in the Universe itself Having subtracted the dipolar anisotropy due to the motion of the Earth relative to the 3 K radiation, we are left with radiation that is exceedingly isotropic. So, we have to ask whether there are any residual variations that would point to a departure from isotropy of the radiation itself? This is a crucial question. Although it was gratifying to have the radiation so isotropic that there could be little doubt of its cosmic origins, nevertheless a completely isotropic distribu 6.2.2 The Earth's motion relative to the 3 K radiation Radiation has energy and momentum, so we can use the molecules of a fluid such as air as an analogy for the photons of radiation. A detector pointing forwards along the direction of our motion (if any) will encounter a greater number of photons than a detector pointing backwards; in other words, it will record a higher intensity of 3 K radiation. (If the detector is tuned to a narrow band of frequencies one would also have to take account of the change in observed spectrum, but the principle 3.2 The impact of climate change on global freshwater resources The availability of freshwater will be significantly altered in a future world affected by climate change (Houghton, 2004). In some regions, water availability will decrease; in others it will increase. Precise predictions about the extent and exact location of such changes cannot be made because they are based on climate models, the accuracy of which is uncertain. However, there is wide agreement that probable changes will include: More rain in north 2.3 Common maths problems and errors in the workplace In a busy, hospital environment mistakes with medicines and other treatments can happen at any time. Some of these are caused by communication/administrative problems, whilst others are due to mathematical errors (the news stories shown in Figure 7 are sadly typical). 2.1.1 Accuracy The way to ensure that equipment is accurate is to use a series of known standards against which to calibrate the equipment. Calibrating should be done at least each day and sometimes more frequently (such as before using the equipment to measure unknown samples). Many types of measuring equipment go through an automatic calibration when they are switched on, but others require the user to provide a series of known calibration standards. 1.9 Addition of decimal numbers If we add 109.8 ml of one liquid to 6.5 ml of another liquid, what would be the total volume of liquid in ml? To compare 109.8 with 6.5, you need to remember that
Place the two numbers in a grid on top of each other and make sure that columns representing the same magnitude line up wit
Activity 4
