Students might also discuss the causes and sources of mutations as well as other sources of variation such as recombination. They will also need to discuss and analyse the ethical aspects of genetics and how these impact on humans. Ethical issues and dilemmas associated with genetics can elicit student need to know and provide excellent routes into student engagement.
Our website uses a free tool to translate into other languages. This tool is a guide and may not be accurate. For more, see: Information in your language. You may be trying to access this site from a secured browser on the server. Please enable scripts and reload this page. Skip to content. Page Content. Examples of these conceptions include: that any observable variation between organisms of the same species is solely due to environmental factors that not all living things contain genetic information that a gene is not a real thing that genes that carry the genetic material are only found in the blood or only found in the brain or only found in the reproductive system that a person will only carry genes for characteristics they display such as tongue rolling and not for characteristics that they do not display such as red hair that acquired changes e.
Critical teaching ideas Genetic material provides the information that allows living things to function. Genetic information can be passed on from generation to generation.
The passing on of this genetic information will be different in asexual and sexual reproduction and cloning. Variations within this information are more likely in sexual reproduction. Changes in genetic information for example, from mutation can give rise to variation in characteristics and can be passed on through the generations.
Promote reflection on and clarification of existing ideas Another activity might be for the students to design high tech genetic identity cards; for this students may need to research the possible ethical and human rights considerations of collecting this personal information. Promote reflection on and clarification of existing ideas Students might also discuss the causes and sources of mutations as well as other sources of variation such as recombination.
Find out more. Biological diversity — biodiversity — is reflected in the vast number of species of organisms, in the variation of individual characteristics within a single species and in the variation of cell types within a single multicellular organism. Differences between species reflect genetic differences. Differences between individuals within a species could be the result of genetic factors, of environmental factors, or a combination of both.
The base sequence of each gene carries the coded genetic information that determines the sequence of amino acids during protein synthesis. The genetic code used is the same in all organisms, providing indirect evidence for evolution. Genetic diversity within a species can be caused by gene mutation, chromosome mutation or random factors associated with meiosis and fertilisation.
This genetic diversity is acted upon by natural selection, resulting in species becoming better adapted to their environment. Variation within a species can be measured using differences in the base sequence of DNA or in the amino acid sequence of proteins. Biodiversity within a community can be measured using species richness and an index of diversity.
In prokaryotic cells, DNA molecules are short, circular and not associated with proteins. In the nucleus of eukaryotic cells, DNA molecules are very long, linear and associated with proteins, called histones. Together a DNA molecule and its associated proteins form a chromosome. The mitochondria and chloroplasts of eukaryotic cells also contain DNA which, like the DNA of prokaryotes, is short, circular and not associated with protein.
A gene occupies a fixed position, called a locus, on a particular DNA molecule. A sequence of three DNA bases, called a triplet, codes for a specific amino acid. The genetic code is universal, non-overlapping and degenerate. In eukaryotes, much of the nuclear DNA does not code for polypeptides.
There are, for example, non-coding multiple repeats of base sequences between genes. Even within a gene only some sequences, called exons, code for amino acid sequences. Within the gene, these exons are separated by one or more non-coding sequences, called introns. The concept of the genome as the complete set of genes in a cell and of the proteome as the full range of proteins that a cell is able to produce.
Translation as the production of polypeptides from the sequence of codons carried by mRNA. Students will not be required to recall in written papers specific codons and the amino acids for which they code. Gene mutations involve a change in the base sequence of chromosomes. They can arise spontaneously during DNA replication and include base deletion and base substitution. Due to the degenerate nature of the genetic code, not all base substitutions cause a change in the sequence of encoded amino acids.
Mutagenic agents can increase the rate of gene mutation. For models with all species, despite a good average correspondence between observed and fitted range change values, there were large residuals for some species Fig 4.
For models including all species, the species that had the largest positive differences between observed and fitted values i. For models excluding C. Results were very similar across measures of range change and levels of recording effort S8 Table.
The dashed unity line indicates equality of observed and fitted values. Species with the largest residuals have been labelled. Considerable distributional changes have occurred among British grasshoppers and related species in recent decades. Our analysis provides interesting indications as to which combination of traits is responsible for the particularly large range expansions of two species, C. No effects were found and model fits dropped sharply when as a matter of caution these two species were omitted, and conclusions about the importance of specific traits therefore had limited relevance to the remaining species.
Limited predictive and explanatory power is a common feature of traits analyses in the literature—while a number of studies find significant associations, the variation explained is generally low, and the traits that are identified for a taxonomic group may vary between studies [ 8 , 9 , 70 — 72 ]. It is likely that characteristics of species beyond those examined explain additional variation, e.
For example, there is limited data on physiological tolerances and quantitative importance of food-web interactions for grasshoppers and relatives [ 21 , 73 ].
Additional constraints of our study were the small number of species 23 , which meant that for traits with few species in individual categories there was limited statistical power, and the necessity to employ conservative range change measures which, while robust, are unable to detect small distributional changes, or indeed more subtle changes in abundance. In the discussion of the findings of the traits analysis we restrict application mainly to C.
Given this and the very close correlation of values across both range change measures and all levels of recording effort Table 3 , we are confident that they are robust, if conservative, estimates of range change. In Britain, those grasshoppers and crickets which have restricted ranges are generally confined to the south or south-east, i. Consequently, where range expansions occurred, they proceeded in predominantly northerly and westerly directions.
For example, this can be clearly seen in the two species with the greatest range increases in this study, C. Such north- or northwest-ward range expansions are also consistent with a climatic explanation see discussion of average latitudes below. The figure shows years of first records of the species in each hectad. Populations of grasshoppers and crickets may undergo large fluctuations in density from year to year, for example in response to variations in abiotic factors such as temperature and precipitation, with densities varying by factors of up to 5 or 10 or even more between successive years [ 73 ].
These fluctuations in density may in turn lead to fluctuations in distributions, particularly at small scales [ 74 ]. If fine-scale records of individual years were to be compared, therefore, erroneous conclusions might be reached about changing distributions.
Here, we summarised records at a coarse spatial scale 10x10km squares , and examined distribution changes across whole decades s vs. We are confident, therefore, that any substantial range changes observed reflect genuine change.
Comparison of trajectories of change between decades with those inferred from annual series of records over the entire study period — confirm that large observed range changes are genuine, cumulative, and sustained and are not artefacts of one-off fluctuations or outbreaks S2 and S3 Figs.
Our all-species traits analysis found three species traits to have significant effects on range changes between the s and s Table 4. The observed significant positive effect of the number of habitats that a species utilises on its ability to extend its distribution has been documented in several species groups and is consistent with the notion that under conditions of environmental change species with a broad ecological niche are more likely to be able to find suitable resources in the landscape than specialists [ 6 , 23 , 29 ].
The species with the largest range size increases in our study, the bush-crickets C. Potential links between the number of habitats species can exploit and climate warming are discussed below. The second finding of our all-species traits analysis—a significant effect of oviposition site, with species which lay their eggs in vegetation increasing their ranges more than species that oviposit in the ground or at the ground-vegetation interface—may be related to land use changes and their effects on microclimates.
The recently published second atlas of mosses and liverworts in Britain documents particular declines for species of low-nutrient lowland habitats [ 75 ]. Notwithstanding localised decreases in vegetation height through factors such as increasing rabbit populations [ 76 ] and targeted habitat management, therefore, it is possible that suitable microclimates for insects that oviposit in the ground have generally decreased, despite climatic warming. At the same time, species that oviposit in vegetation including the two with the largest range size increases in the present study, M.
Conversely, the mottled grasshopper Myrmeleotettix maculatus has shown one of the largest declines in our study; it oviposits in the soil and is a specialist of short vegetation and bare ground exposed to the sun and is likely to be very vulnerable to succession and nutrient enrichment [ 21 , 50 ].
The importance of short vegetation or open ground for oviposition have been highlighted for other taxa such as bumblebees [ 77 ], butterflies [ 35 ], moths [ 7 ] and indeed recently for grasshoppers and relatives with an explicit link to a negative effect of nutrient enrichment [ 26 ].
This is consistent with a positive effect of climatic warming over the study period — Being on their northern range edge, species with low average British latitudes such as M.
Under a warming climate they are therefore expected to expand their ranges into previously unsuitable areas; such changes have been observed for multiple species groups [ 2 , 5 , 78 ]. Consistent with this explanation, M. There is anecdotal evidence that C. Another interesting mechanism by which climatic warming could aid range expansions is through increases in voltinism [ 37 ].
The development of M. Increased temperatures could therefore halve generation times for parts of the populations of these species and so aid increases in numbers and range expansions. The number of generations per year is not identified as a significant trait in our analysis. A further reason that we found no effect here may be that climatic warming may of course also aid reproduction in species such as C. In addition to the three traits discussed above, wing-length dimorphism is known to be a further very significant trait catalysing the rapid range expansion of M.
Wing-length is not identified as a significant predictor of range change in our analysis. Likely reasons for this include that other wing-dimorphic species have not expanded rapidly, and that our study did not take account of maximum proportions of macropters in populations, because the small total number of species did not allow a finer categorisation.
Overall, it seems likely that a combination of favourable traits is required for species to have been able to expand their ranges under the climatic and land-use changes of recent decades. Wing-dimorphic species such as C.
It is instructive to compare these species to others which share some but not all of these traits: For example, Conocephalus dorsalis is very similar to M. This may be because, while wing-dimorphic, it is not known to produce large numbers of macropters [ 21 ]. A lack of information on maximum proportions of macropters in our analysis may also explain why the range change for this species is overestimated by models, while it is underestimated for C.
Another species, Chorthippus parallelus , has somewhat less in common with C. Our analysis showed large changes in distributions for some grasshoppers and crickets at the scale of a whole geographical region Britain between and , a period of extensive climatic and land use change. Range changes were positively influenced by three species traits: habitat generalism, oviposition above ground in vegetation, and a southerly distribution. However, these findings applied mainly to the two species with the greatest increases in range only, C.
Several previous studies on the rapid range expansion of these two species emphasised wing-length dimorphism as the key to their success, with the ability of populations to develop large proportions of long-winged macropterous individuals resulting in a high phenotypic plasticity of dispersal.
Our findings suggest that dispersal is not the whole picture and that it is likely to be the combination of traits that these species possess that have enabled them to thrive under recent environmental changes.
Differences in their traits, however, were not significant predictors of the range size changes of the remaining individual species. We conclude that trait-based analyses may contribute to the assessment of species responses to environmental change and may provide insights into underlying mechanisms, but results need to be interpreted with caution and may have limited predictive power, particularly where trait and population trend data is not extremely detailed and species numbers are low.
Advances in species distribution and abundance monitoring, and assembly of more detailed and comprehensive trait data for example alongside the collection of distribution data [ 93 ] or through follow-up investigations on the findings of studies such as the present one, will be important for future improvements in assessing the consequences of environmental change. In each case, Conocephalus discolor and Metrioptera roeselii were identified as outliers. We are very grateful to the many volunteer recording scheme contributors who have gathered the distribution data used in this study.
Many thanks to Jane Hill and Julia Ferrari for useful feedback on earlier drafts of this paper, and to two anonymous reviewers for thorough and helpful comments.
Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Abstract There are large variations in the responses of species to the environmental changes of recent decades, heightening interest in whether their traits may explain inter-specific differences in range expansions and contractions. Introduction The responses of individual species to environmental change are highly variable, despite average polewards and upwards range shifts of species responding to climate change, and contractions of species ranges in regions experiencing habitat loss, degradation and fragmentation [ 1 — 5 ].
We considered here a series of traits that might be expected to influence the responses of species to a variety of land use and climatic changes: Resource use traits Under conditions of environmental change, generalists that are capable of exploiting a wide range of resources are more likely to be able to survive changes to the availability of a specific resource in a landscape, and they are more likely than specialists to be able to exploit new landscapes if climatic or other conditions become suitable [ 28 , 29 ].
Materials and Methods Range changes The extent of changes in distributions of British grasshoppers and crickets was quantified using the data of the Orthoptera Recording Scheme [ 22 , 42 , 43 ]. Download: PPT. Fig 1. Table 1. Species traits A database of British grasshopper and related species traits covering habitat and resource use, life history, dispersal ability, and distribution was compiled to address the hypotheses of factors affecting range change outlined in the introduction Tables 1 and 2.
Table 2. Definitions of species traits and sources of information. Results Range changes Our analysis of grasshopper and related insect range changes in Britain between the s and s showed moderate or large range size increases for a few species, with range size decreases for a smaller number, and less or no consistent change for the remaining majority of species. Fig 2. Range changes of grasshoppers and related species in Britain between —9 and —9. Fig 3.
Grasshopper and related species range sizes in —9 and —9 and calculation of range change measures. Species traits, results for all species The analysis of relationships between distribution changes and species traits for all species showed three traits to be significantly associated with changes in range for both range change measures Table 4. Table 4. Impacts of species traits on distribution changes of British grasshoppers and crickets all species between the s and s.
Species traits, results excluding Conocephalus discolor and Metrioptera roeselii When the analysis of the relationships between distribution changes and species traits by GLMs was repeated for all species excluding the two species with particularly large range changes, Conocephalus discolor and Metrioptera roeselii , no traits were found to be significantly associated with changes in range for either measure of range change Table 5.
Table 5. Impacts of species traits on distribution changes of British grasshoppers and crickets excluding Conocephalus discolor and Metrioptera roeselii between the s and s. Discussion Considerable distributional changes have occurred among British grasshoppers and related species in recent decades. Fig 5. Range expansions of Conocephalus discolor and Metrioptera roeselii in Britain between and Species traits Our all-species traits analysis found three species traits to have significant effects on range changes between the s and s Table 4.
Supporting Information. S1 Fig. S2 Fig. Scatter- and boxplots of annual relative numbers of hectad records for species with the greatest positive range changes. S3 Fig. Scatter- and boxplots of annual relative numbers of hectad records for species with the greatest negative range changes. S1 Table. Grasshopper and related species range changes between —9 and —9.
S2 Table. S3 Table. Results of Shapiro-Wilk tests for normality of residuals. S4 Table. S5 Table. Impacts of species traits on distribution changes of British grasshoppers and crickets all species , phylogenetic models. S6 Table. Amount of overall variation explained by models adjusted deviance D 2.
S7 Table. Impacts of species traits on distribution changes of British grasshoppers and crickets excluding Conocephalus discolor and Metrioptera roeselii , phylogenetic models.
S8 Table. Fitted range change values. Acknowledgments We are very grateful to the many volunteer recording scheme contributors who have gathered the distribution data used in this study. References 1. Temporal variation in responses of species to four decades of climate warming. Global Change Biology. View Article Google Scholar 2. Terrestrial and Inland Water Systems. Comparative losses of British butterflies, birds, and plants and the global extinction crisis.
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