Learning outcomes By the end of this unit you should be able to: identify the common features shown by tree-dwelling mammals from different groups; show an awareness of the difficulties of classifying primates, especially in relation to the position of the prosimians; give an account of opportunities and challenges encountered by tree-dwelling mammals and of evolved adaptations linked with arboreal life; provide examples of the closeness (and sometimes
Acknowledgements The content acknowledged below is Proprietary (see terms and conditions) and is used under licence. Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit: The content acknowledged below is Proprietary and is used under licence.
Author(s):
7 The threat of extinction DA ends his book by writing eloquently of the dangers of extinction faced by mammals, from habitat loss as we exploit our environment to produce more and more food, for our growing population. However bleak the picture, there is still time and opportunity to save mammal species from extinction. Although bison in the USA and Canada were reduced to barely 1000 individuals in 1900, their numbers have now risen to well over 150 000 thanks to the efforts of First Nation indigenous peoples, and ran
5 Who were the ancestors of Homo sapiens? Large brain size is a defining feature of Homo sapiens, which means that evolution of increased brain size in Homo is crucial evidence. Indeed, an increase in both the size and the complexity of the brain is a defining feature of primate evolution as a whole. It's possible to estimate brain sizes from fossil skulls or parts of skulls, e.g. by filling what there is of the skull with sand and then measuring the volume of the sand. Use of computer technology fills in ‘gaps’ in
4 Who were the ancestors of Homo? Fossil evidence supports Darwin's view that humans and apes evolved from an ape-like ancestor and, furthermore, suggests that the ape line diverged from the Homo line at least five million years ago (Figure 1). From our current knowledge of the fossils available to us, the evolutionary tree in
Acknowledgements Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit: The content acknowl
8 What makes a successful omnivore? From what has been said already, there's good evidence that the key physical characteristic of the great majority of omnivores is a non-specialist dentition. What about other aspects of their biology? Question: Many omni 2.3 Food chains and food webs This section includes two graphs. Figure 2 has the standard numerical values on its axes, in this case years from 1830 to 1930 on the hor 2.2 Energy flow in ecosystems You are about to meet some very large numbers, expressed in scientific notation, and some new units. The new units are those that are used to measure the amount of solar energy received by a part of the Earth's surface. Since plants are dependent on light for photosynthesis, the amount of plant material that ca 8.1 Introduction You know by now that plants can synthesise all the complex molecules that make up their tissues and seeds from very simple molecules – water, carbon dioxide and minerals from the soil. Mammals, on the other hand, need to take in many complex molecules ready-made, and some foods do not contain the right amounts or the right mix of nutrients. They have evolved various strategies to overcome the shortfalls, some of which are described in this section. 7 Plant defences 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 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 3 Herbivore teeth Tables are a useful way of recording key information. The headings for Tables 1 and 2 have been prepared for you, and you can copy and complete the tables in your notebook. If you need to find any of this information again later, then it is very useful to have it summarised in a table. I Introduction The plant predators, or herbivores, are a varied group, but they share certain characteristics. Many of them are large; among the smallest is the chevrotain (or mouse-deer) at about two kilograms weight, and the elephant is the largest, with a typical bull male weighing around six tonnes. In this unit we'll be looking in more detail at some of the problems and consequences of adopting a plant-eating way of life. Leaves are a much less nutritious food than most kinds of animal material, so lar 6 Reflection If you are working through all the units in this series, you'll be aware that this unit has taken a somewhat different tack from earlier ones. I've used rodents to explore some fundamental biological principles that have a relevance far beyond this particular order. It is especially appropriate to talk about issues such as biological success in connection with rodents, given their very wide geographical distribution and the very large number of rodent species and individuals. You'll recall (f Learning outcomes By the end of this unit you should be able to: describe the lifestyle of a variety of insect eaters, from four orders; give examples of adaptations linked to feeding in insect eaters; explain the limited extent to which insectivores can be regarded as ‘primitive’; characterise typical adult mammalian dentition and understand dental formulae; recognise teleology and write down accounts of evolution that do not assume 6.2.4 The speed and direction of the Earth's motion The first significant claim to have detected the motion of the Earth relative to the ‘frame of isotropic 3 K radiation’ came in 1977 from a group at Berkeley, California. They concluded that the Earth is moving at a speed of (390 ± 60) km s−1, in a direction towards the constellation Leo, relative to a frame in which the 3 K radiation is isotropic. Their conclusion resulted from observations of a variation of intensity with angle of the form predicted by Equation 14, which w 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 2 Radiation from the galaxies Stars occur in great collections called galaxies. The distribution and motion of galaxies provide us with the first important experimental information on which we shall build our understanding of the type of universe we inhabit. So, what do we know about galaxies? All the stars that can be distinguished by the naked eye – a few thousand in number – belong to one galaxy: our own Milky Way Galaxy. Sometimes it is just written Galaxy, with a capital G, to distinguish it from all 6 Appendix: a note on displacement current density This appendix is optional reading. It is included for the sake of comparison with other texts. The Ampère–Maxwell law, is sometimes expressed in the form
Question 11
Activity 5
