Question

Climatic and Ecological Change: Past and Future The earth and its life are always changing. However, many of the most important changes occur over such long periods of time or at such large spatial scales that they are difficult to study. Two approaches that provide insights into long-term and large-scale processes are studies of pollen preserved in lake sediments and evolutionary studies. Margaret Davis (1983, 1989) carefully searched through a sample of lake sediments for pollen. The sediments had come from a lake in the Appalachian Mountains, and the pollen they contained would help her document changes in the community of plants living near the lake during the past several thousand years. Davis is a paleoecologist trained to think at very large spatial scales and over very long periods of time. She has spent much of her professional career studying changes in the distributions of plants during the Quaternary period, particularly during the most recent 20,000 years. S ome of the pollen produced by plants that live near a lake falls on the lake surface, sinks, and becomes trapped in lake sediments. As lake sediments build up over the centuries, this pollen is preserved and forms a historical record of the kinds of plants that lived nearby. As the lakeside vegetation changes, the mix of pollen preserved in the lake’s sediments also changes. In the example shown in f igure 1.8, pollen from spruce trees, Picea spp., first appears in lake sediments about 12,000 years ago then pollen from beech, Fagus grandifolia, occurs in the sediments beginning about 8,000 years ago. Chestnut pollen does not appear in the sediments until about 2,000 years ago. The pollen from all three tree species continues in the sediment record until about 1920, when chestnut blight killed most of the chestnut trees in the vicinity of the lake. Thus, the pollen preserved in the sediments of lakes can be used to reconstruct the history of vegetation in the area. Margaret B. Davis, Ruth G. Shaw, and Julie R. Etterson review extensive evidence that during climate change, plants evolve, as well as disperse (Davis and Shaw 2001; Davis, Shaw, and Etterson 2005). As climate changes, plant populations simultaneously change their geographic distributions and undergo the evolutionary process of    adaptation    , which increases their ability to live in the new climatic regime. Meanwhile, evidence of evolutionary responses to climate change is being discovered among many animal groups. Willranging from small mammals and birds to insects ( fig. 1.9 ), in response to increasing growing season length as a consequence of the now-well-documented phenomenon of globaliam Bradshaw and Chrranging from small mammals and birds to insects ( fig. 1.9 ), in response to increasing growing season length as a consequence of the now-well-documented phenomenon of global istina Holzapfel (2006) summarized several studies documenting evolutionary change in northern animals, ranging from small mammals and birds to insects ( fig. 1.9 ), in response to increasing growing season length as a consequence of the now-well-documented phenomenon of global warming (see chapter 23, p. 519). Research such as that by Davis and her colleagues will be essential to predicting and understanding ecological responses to global climate change. I n the remainder of this book we will fill in the details of the sketch of ecology presented in this chapter. This brief survey has only hinted at the conceptual basis for the research described. Throughout this book we emphasize the conceptual foundations of ecology. Each chapter focuses on a few e cological concepts. We also explore some of the applications associated with the concepts introduced. Of course, the most important conceptual tool used by ecologists is the scientific method, which is introduced on page 9. W e continue our exploration of ecology in section I with natural history and evolution. Natural history is the foundation on which ecologists build modern ecology for which evolution provides a conceptual framework. A major premise of this book is that knowledge of natural history and evolution improves our understanding of ecological relationships.

During the course of the studies reviewed in this chapter, each scientist or team of scientists measured certain variables. What major variable studied by Margaret Davis and her research team distinguishes their work from that of the other research reviewed in the chapter?

Answer 1

The evolutionary works are done by the many researchers and reviewed further by others but in this case, these researchers have done a study in an opposite format that means they have not gone to search for the evolved species directly rather it might be the possibility that the evolved species must have been suppressed during the process. Hence, they have collected the sediments of the lake and found out the pollen grains embedded in it and based on the genetic makeup of the pollen grain it was a backtrace study to find out the surrounding region's plants. Thus to get an idea that what kind of climate change is leading to such evolution by the pollen grain study. All other researcher mostly tries to take the genome of the plant or animal and microorganism found in that niche and then carry out the comparative study with the older databases for that species to check for the similarity and the changes found in them. Thus this study does not need to find the changes directly, they are getting double sure by performing this kind of work as the pollen study. It is logical and like a two selective marker that the study will carry out the genomic study as well but on the primitive stages the pollen study is the primary aim. It can be a possibility that some of the pollens must be found in the surrounding but they have also consider to find out the sediment in the lake which must have entrapped the pollen in it.

Therefore this study is varies from other on all these aspects.