Environmental Biology

Allan M. Jones

• Publisher: Routledge
• Year: 2006
• eBook ISBN: 9781134777662
• Topic: Ciencias biológicas
• Subtopic: Geografía

Environmental Biology offers an accessible introduction to the core elements of biology and the biosphere. With balanced coverage of acquatic and terrestrial examples throughout, the text builds logically to present a clear understanding of the fundamental processes of life before examining its more complex components, namely individuals, populations, communities and ecosystems.
A knowledge of environmental biology and its practical applications is essential for a deeper understanding of the environment. Environmental Biology offers an invaluable introduction to the living environment for all areas of study, from environmental history, agriculture and forestry, to impact assessment, climate change, ecology and conservation.

The basic organisation of living forms

Key concepts

• Living things combine many vital characteristics to distinguish them from non-living materials.
• Cells are the fundamental units of life which interact with their environment.
• The cell contains various structures which organise its activities.
• Energy transformations form the engine of the cell.
• The materials of life: eleven main elements, water and the macromolecules.
• The diversity of life and its levels of organisation.
• The species concept and the kingdoms of life.

There are a number of features and concepts which apply to the study of all living things. The construction and activities of cells underlie any understanding of the material and energetic requirements of life at all levels of study. The development and evolution of the interrelationships between the cell and its environment have resulted in increases in complexity and diversity. This chapter briefly reviews the key organisational features of living forms as related to environmental systems and outlines the ways in which biologists define and describe the variety of living forms.

1.1 The fundamentals of life

Some of the basic properties of living material need to be considered if we are to understand the ways in which organisms interact with their environment. Organisms are essentially chemical machines based around the chemistry of carbon compounds and of water, possibly the most important molecule to life.

1.1.1 The characteristics of life

Life is not a simple concept and it is impossible to define precisely what life is: all that can be done is to describe the observable phenomena that distinguish living matter from inanimate matter. Living organisms are characterised chemically by their ability to interact with their environment. Both biotic (living) and abiotic (non-living) components exchange and synthesise materials and energy in carefully controlled manipulations through the integrated chemical processes called metabolism.

Most properties exhibited by living forms are found also in some form in non-living material, i.e. they are characteristic of living material but not restricted to it. These include:

• Cellular organisation: all organisms comprise one or more cells but non-living structures such as coacervates, a mass of minute (colloidal) particles held together by electrostatic attraction, also appear cell-like in organisation.
• Nutrition:the acquisition of materials and energy necessary for growth. In living material this is either

• autotrophic,using light energy (photosynthesis) or chemical energy (chemosynthesis), or
• heterotrophic,obtaining materials and energy by the breaking down of other biological material using digestive enzymes and then assimilating the usable by-products.

Non-living forms, e.g. stalactites, acquire material only passively.

• Growth: non-living objects such as crystals usually grow by the addition of materials to their exterior while living material grows from within using materials acquired through nutrition.
• Respiration: a series of energy-producing chemical reactions releasing energy from energy-rich compounds either by ‘burning’ with oxygen (aerobic respiration) or by reactions not involving oxygen (anaerobic respiration and fermentation).
• Responsiveness (irritability): the ability to respond to changes in both internal and external environments, usually to improve the chances of survival. This may involve growth (plants), movement (mobile species), or physiological changes. Inanimate material can respond only passively and to external forces.
• Movement: non-living material moves only as a result of external forces while living material moves as a result of internal processes at cellular level or at organism level (locomotion in animals and growth in plants).
• Excretion: the elimination from living organisms of waste by-products from metabolism.
• Reproduction: all living forms can multiply, thus ensuring the continuation of the species. Non-living material can sometimes replicate, e.g. the production of crystals and the spreading of a fire. However, it never involves the use of hereditable material (DNA or RNA; see Section 1.1.3.4), which contains a complex coding for the construction, development and functioning of the progeny.

These observable characteristics are typical of all living organisms but the real significance of living material lies in its ability to extract, convert and use energy and materials to maintain and even increase its energy content. The process of metabolism, a characteristic of life, is itself divided into two processes:

• Catabolism, the breaking down of complex materials into simpler ones using enzymes and releasing energy, and
• Anabolism, the utilisation of energy and materials to build and maintain complex structures from simple components.

Non-living material can only undergo catabolic activity according to the Second Law of Thermodynamics (Box 1.1).

Box 1.1

The flame of life – an interesting analogy

Non-scientific literature often uses the phrase ‘The flame of life’. However, this analogy is not as strange as it may seem at first sight since the properties of a burning flame parallel many of the characteristics of living things. Thus, arguably, a flame:

• respires: it requires oxygen for its chemical conversion of organic material into carbon dioxide, water and energy (heat). This is fundamentally the same catabolic process carried out in all aerobic cellular respiration. However, cells carry it out under controlled conditions using ...

Table of contents

• Front Cover
• Half Title
• Title Page
• Copyright
• Dedication
• Contents
• Series editors‘ preface
• List of figures
• List of tables
• List of boxes
• Acknowledgements
• An introduction to environmental biology
• Chapter 1. The basic organisation of living forms
• Chapter 2 The biosphere
• Chapter 3 Basic ecological concepts and processes
• Chapter 4 Conditions and resources: major determinants of ecology
• Chapter 5 Individuals
• Chapter 6 Populations
• Chapter 7 Communities and ecosystems
• Glossary
• Index