Biological Sciences
Variation Biology
Variation in biology refers to the differences that exist among individuals within a species. These differences can be attributed to genetic, environmental, or developmental factors. Understanding variation is crucial in fields such as evolution, genetics, and ecology, as it provides insights into the diversity and adaptability of living organisms.
Written by Perlego with AI-assistance
Related key terms
1 of 5
7 Key excerpts on "Variation Biology"
eBook - PDFPhysiological Diversity
Ecological Implications
- John Spicer, Kevin Gaston(Authors)
- 2009(Publication Date)
- Wiley-Blackwell(Publisher)
These embrace a formi- dable range of variation in evolutionary history, genetics, morphology, phy- siology and ecology. On average, each of these millions of species comprises, at least, thousands of individuals, spread across hundreds, or many hundreds, of square kilometres of the landscape or seascape, or through the enveloping media. In most cases, these individuals will have a unique genetic make-up, and, if only in the details, a unique morphology, physiology and ecology. They will, through their life span, encounter a set of environmental circumstances (abiotic and biotic) which is different from that of their conspecifics, perhaps only mildly so, perhaps severely. They may respond in different ways. Their life stories will certainly not be precisely replicated. The study of biology is the study of the diversity of life. Some facets of this diversity have been investigated exhaustively, others more superficially. With regard to physiological diversity, on the one hand the numerous adaptations of animals to their environment have been the focus of the attentions of innu- merable investigators. This has yielded remarkable insights into the variety of ways in which different animals cope with their environment, as well as gen- erating a voluminous literature. On the other hand, the patterns in physiologi- cal diversity more broadly, the mechanisms generating them, and some of their significant implications, have seldom been explicitly enunciated. This book is a step towards resolving this circumstance. More specifically, it attempts to provide an overview of physiological diversity and its ecological implications. 1.1 Physiological diversity Physiological diversity (or physiological variation; the terms will be used inter- changeably) is the variability in physiological characters (or traits) among animals (or plants and other organisms). Physiological traits are regulata and tools of regulation, performance and tolerance.
eBook - ePubBiology Trending
A Contemporary Issues Approach
- Eli Minkoff, Jennifer K. Hood-DeGrenier(Authors)
- 2023(Publication Date)
- CRC Press(Publisher)
The human species is highly variable in every biological trait. Humans vary in their physiology, body proportions, skin color, and body chemicals. Many of these features influence susceptibility to disease and other forces of natural selection. Continued selection over time has produced adaptations of local populations to the environments in which they live. Much of human biological variation is geographic; that is, there are differences between population groups from different geographical areas. For example, Northern European peoples differ in certain ways from those from Eastern Africa, and those from Japan differ in some ways from those from the mountains of Peru. Between these populations, however, lie many other populations that fill in all degrees of variation between the populations we have named, and there is also a lot of variation within each of these groups.Central to the study of human variation is the concept of a biological population, as defined in Chapter 5 , p. 172, and as explained again later in this chapter. Both physical features and genotypes vary from one person to another within populations, but there is also a good deal of variation between human populations from different geographic areas as the result of evolutionary processes. How do populations come to differ from one another? How do alleles spread through populations? How do environmental factors such as infectious diseases influence the spread? Why are certain features more common in Arctic populations and other features more common in tropical populations? Why have we traditionally thought of some of these variations as defining “races”? These are some of the questions that are explored in this chapter.7.1 THERE IS BIOLOGICAL VARIATION BOTH WITHIN AND BETWEEN HUMAN POPULATIONS
All genetic traits in humans and other species vary considerably from one individual to another. Some of this variation consists of different alleles at each gene locus; other variation results from the interaction of genotypes with the environment. The simplest type of variation governs traits such as those discussed in Section 3.3 , in which an enzyme may either be functional or nonfunctional. The inheritance of these traits follows the patterns described in Chapter 2 , which you may want to review at this time. In particular, be sure that you understand the meaning of dominant and recessive alleles and of homozygous and heterozygous genotypes. Many other traits, as we saw in Chapter 3
eBook - PDFBiology Today
An Issues Approach
- Eli Minkoff, Pamela Baker(Authors)
- 2003(Publication Date)
- Garland Science(Publisher)
204 T he human species is highly variable in every biological trait. Humans vary in their physiology, body proportions, skin color, and body chemicals. Many of these features influence susceptibility to disease and other forces of natural selection. Continued selection over time has produced adaptations of local populations to the environments in which they live. Much of human biological variation is geographic; that is, there are differences between population groups from different geographical areas. For example, northern European peoples differ in certain ways from those from eastern Africa, and those from Japan differ in some ways from those from the mountains of Peru. Between these populations, however, lie many other populations that fill in all degrees of variation between the populations we have named, and there is also a lot of variation within each of these groups. Central to the study of human variation is the concept of a biological population, as defined in Chapter 5 (p. 151), and as explained again later. Both physical features and genotypes vary from one person to another within populations, but there is also a good deal of variation between human populations from different geographic areas as the result of evolutionary processes. How do populations come to differ from one another? How do alleles spread through populations? How do environmental factors such as infectious diseases influence the spread? Why are certain features more common in Arctic populations and other features more common in tropical populations? Why do we think of some of these variations as ‘races’? These are some of the questions that are explored in this chapter. There Is Biological Variation Both Within and Between Human Populations All genetic traits in humans and other species vary considerably from one individual to another. Some of this variation consists of different alleles at each gene locus; other variation results from the interaction of genotypes with the environment.
eBook - PDFEcological Mechanics
Principles of Life's Physical Interactions
- Mark Denny(Author)
- 2015(Publication Date)
- Princeton University Press(Publisher)
Part IV ECOLOGICAL MECHANICS Chapter 19 Ecological Variation and Its Consequences ... variation itself is nature’s only irreducible essence. Variation is the hard reality, not a set of imperfect measures for a central tendency. Stephen Jay Gould (1985) N ature is variable: the physical environment fluctuates in both predictable and unpredictable ways, plants and animals fatigue and sustain damage, and interac- tions among organisms shift through time and space. On occasion, these variations are sufficiently extreme to pose a substantial threat: an unseasonal freeze can kill all the song birds on an island, for instance; corals can be broken by storm waves; and urchin stampedes can decimate a kelp forest. (We will deal with the biology of these sorts of extremes in Chapter 22.) Most of the time, however, life’s variations fall within organisms’ normal working range, and to understand the resulting biological dynamics we must take these more typical fluctuations into account. We do so in the course of three chapters. In this, the first, we explore scale transition theory, a statistical method that allows one to predict how physiological, environmen- tal, and ecological variability affect the average response of a system (Chesson et al. 2005; Melbourne et al. 2005; Melbourne and Chesson 2006). It also allows one to scale up from experiments conducted locally and for a short time to predict how a phenomenon will play out at larger scales and over longer periods. Scale transition theory is especially applicable in the context of ecomechanics because it makes use of the mechanistic response functions we have explored in the last eighteen chapters. Having quantified the consequences of variability, we proceed in Chapter 20 to investigate spectral analysis, a tool that allows one to specify how variability is distributed among spatial and temporal scales.
eBook - PDF- Robert Cliquet(Author)
- 2014(Publication Date)
- Masarykova univerzita(Publisher)
CHAPTER 2 INDIVIDUAL VARIATION AND INDIVIDUALISM INTRODUCTION It is logical to start this book with a discussion about the simplest source of human biological variation – the differences which exist between individuals within populations. However, biological variation at the individual level is not only influenced by genetic and environmental factors of a general nature, but also by specific biological sources of variation such as sexual variation, age variation, social variation, and inter-population variation – specific sources which will be addressed in subsequent chapters. Furthermore, dealing first with the individual sources of biological variation allows us to briefly dwell upon the role of basic determinants – both genetic and environmental – of biological variation in general, which are also necessary to understand the causation of specific sources of biological variation, such as sex, age, and race in later chapters. From the study of within-population variability it is conceptually easy to move to hierarchically more complex forms of variability, such as sexual variability, age variability, between-population variability and inter-generational variability. The central question in this chapter is why people within a population, and apart from sex, age, and race, differ from each other and how this variation is linked to individualism in modern society. Why don’t people of the same sex, age, or race resemble each other completely? EVOLUTIONARY BACKGROUND Some basic genetic concepts In order to explain the evolutionary background of individual variation, it is necessary to remind the reader in a very simple and brief way of a few basic genetic concepts. Most readers will undoubtedly be familiar with these concepts, but it might be useful to specify their importance for the genetically unique identity of the individual and its relation to the population to which it belongs and its role in intergenerational transmissions, i.e.
eBook - PDF- K V Krishnamurthy(Author)
- 2003(Publication Date)
- CRC Press(Publisher)
In organisms that exhibit a sexual mode of reproduction, the resultant genetic variations can spread through the population by recombination. In inbreeding members of a population, the pool of genetic variation already present is acted upon by selection. Differential survival results in changes in the frequency of genes within this pool, in tum resulting in population evolution. Therefore, the main significance of genetic variation in a population is that it enables natural evolutionary changes to take place since the rate of these changes is proportional to the amount of genetic diversity available. Genetic Diversity is a resource for the species' own survival and future evolution; it also promotes selective breeding (see Groombridge 1992). In addition, genetic variation also confers fitness advantages upon the members of a population. Another reason why it should be considered a resource is that many genes are potential sources for improving the productivity of other members of a population or of a species. For example, genes from wild plants have become very important today for improving domesticated taxa (for more details, see Chapters 4 and 10). The global pool of genetic diversity represents all the information pertinent to all biological structures, functions and processes on this planet. In other words, every process and every pattern is encoded in a genetic 'library' of unimaginable global extent. But only a negligible fraction (often less than 1 %) of the genetic material of higher organisms is expressed in the form and functions of organisms (see Groombridge 1992). This means that much of the DNA in each cell is not coded (Thomas 1992). The role of such 'silent' DNA in the expression of variations still remains unclear. Again, of the estimated 10 9 different 11 genes in the world biota (of which about lOS are distributed in higher organisms) not one has been found to duplicate the contribution of another to the overall genetic diversity.
eBook - PDF- Robert Jurmain, Lynn Kilgore, Wenda Trevathan, Russell Ciochon(Authors)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
A DNA molecule superimposed over a NASA map of the Old World. iStockphoto.com/Jgroup; NASA; Top Images: © Cengage Learning; Guido Cozzi/Terra/Atlantide Phototravel/Corbis; Robert Jurmain ◂ ▸ Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 CHAPTER 14 | MODERN HUMAN BIOLOGY: PATTERNS OF VARIATION 412 Unfortunately there are probably hundreds (if not thousands) of popular mis-conceptions regarding human diversity, and to make matters worse, many people seem unwilling to accept what science has to say on the subject. Many misconcep-tions, especially those regarding how race is defined and categorized, are rooted in cultural history over the last few centuries. In Chapters 3 and 4, we saw how physical characteristics are influenced by the DNA in our cells. We discussed how people inherit genes from their parents and how variations in those genes (alleles) can produce different expressions of traits. We also focused on how the basic principles of inheritance are related to evolution-ary change. In this chapter, we’ll continue to deal with topics that directly relate to genetics— namely, biological diversity in humans and how biocultural evolution influences the ways in which humans adapt to environmental challenges. After discussing histori-cal attempts to explain human phenotypic variation and racial classification, we’ll examine contemporary methods of interpreting diversity. In recent years, several new techniques have emerged that permit direct examination of the DNA mole-cule, revealing differences among people even at the level of single nucleotides. But as discoveries of different levels of diversity emerge, geneticists have also shown that our species is remarkably uniform genetically, particularly when compared with other species.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
