Living Things Are Characterized byTerm Paper

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[. . .] 37) Biotechnology has provided scientists with new means to understand the complexity of protein functions. Molecular cloning, an important tool in biotechnology, has vastly improved the prospects of understanding individual proteins and their functions. Microarray technology is another tool, which allows the study of a group of genes in combination. Similarly, Antisense and RNA interference (gene blocking) and gene knockouts (induced mutations) are important biotech methods that aid our understanding of the complex genetic machinery.

38) Biotechnology is a diverse field and hence the application areas are ever extending. The most prominent application is in the field of medicine. Synthesis of human insulin for example is considered a remarkable breakthrough and a blessing in disguise for diabetic patients. Similarly Genetically modified food products are saving countless lives in famine struck African countries. Safety of food materials is also vastly increased with the availability of DNA probe kits that can detect allergic microorganisms. From the environmental viewpoint also bio-decomposition of waste products promise better pollution control.

39) Scientists study evolution by analyzing the fossil remains and the structural similarity along with slight variations in morphological features. Homologous functional structures indicate same ancestry. Further, currently available genetic analysis also reveals similarities among organisms.

40) Darwin's theory of evolution suggests a common ancestry of evolution for all the species that exist in the world. Darwin included the theory of natural selection ("preservation of favorable individual differences ") to account for the evolutionary changes implying that by nature only the fittest can survive.

41) Genes are responsible for particular character traits. Evolution of character traits occurs at a particular species or population level as a result of the interaction between the genes and the environment.

42) Evolution can be bought about by mutations, reduced population size, unequal distribution of allele frequencies and natural selection.

43) Natural selection brings about changes in populations over a period of time. Unequal distribution of phenotypes as a result of natural selection hinders variety. For example sexual selection favors traits that increase mating chances at the cost of other phenotypic traits.

44) Extinction of species leads to loss of bio diversity. A variety of factors contribute to species extinction. The prominent of these is habitat destruction as a result of direct or indirect human activities. (Deforestation, pollution, etc.) Introduction of new species is also found to affect the native species. Further hunting, poaching are also leading causes for species extinction or dwindling populations.

45) From the biological viewpoint, a species denotes a group of interbreeding individuals that share a common ancestor. Members of a Species reproduce in isolation from other groups so their genotypes are intact.

46) Isolation and genetic divergence are two necessary conditions for the formation of a new species. Allopatric (where there is physical separation of the population), Sympatric (ecological isolation) and adaptive radiation (where species evolve in response to environmental conditions) are the different speciation methods.

47) There are two main ways of maintaining reproductive isolation between species. They are premating isolation and postmating isolation. Premating isolation includes many factors like geographical, ecological, temporal (differing mating periods) and mechanical isolation. (Incompatible sexual organs). Gamete incompatibility and Hybrid infertility are postmating isolation mechanisms.

48) The origin of life is pretty much an unsolved mystery. Sidestepping spontaneous evolution theory, which the scientific community has mostly rejected, we are left with the theory of organic evolution. (Chemical evolution). Under prebiotic conditions, it is believed that organic molecules would have formed spontaneously, and in the process the RNA would have become the first self-replicating molecule.

49) Though there is no conclusive answer, it is generally believed that the earliest organisms were anaerobic prokaryotes. It is also believed that gradually these early organisms developed the mechanism of utilizing sunlight (photosynthesis) thereby increasing the availability of oxygen.

50) Unicellular organisms were the only forms of life in the early periods of life on the planet. Biologists believe that multicellularity arose as a result of mutations in cell divisions, which prevented the separation of cells after division. (Failure of cytokinensis) Then natural selection might have favored multicellularity for its advantages.

51) Life on land evolved as some plants and amphibians adapted to life on dry lands. Thus, from primitive plants, which depended on water for reproduction (swimming sperms), plants developed pollen grains and attracted insects for pollination. Similarly, amphibians evolved from fish, reptiles evolved from amphibians and from reptiles birds and mammals evolved gradually.

52) Biological nomenclature is a well-defined system wherein each species is identified with a two-part name based on its categorization. The categorization is a hierarchical grouping based on the anatomical and molecular similarities and the evolutionary relatedness.

53) Bacteria and Archaea fall under the prokaryotic kingdom though they have different mechanisms. However, recent studies reveal that some Archaea (for ex, Metanococcus jannaschii has protein synthesis that resembles eucaryotes) exhibit functional mechanisms that are similar to Eukaryotes.

54) The Protista kingdom includes fungus like (molds), animal like (protozoa) and plant like (ex algae) forms.

55) Fungi are specialized in that they can reproduce both sexually as well as asexually. They absorb nutrients from plants and other living organisms.

56) Scientists believe that plants originated from green algae. Green algae contain chlorophyll pigments similar to plants. The ancestors of plants can be traced back to the fresh water environment.

57) Animals are multicellular, Ingestive heterotrophs. (Obtain food from their environment) Except sponges all animals have distinct tissues and exhibit radial or bilateral symmetry.

58) Plants have three types of tissues namely 'Dermal tissue', 'Ground tissue' and 'Vascular tissue'. Dermal tissue is the outer layer or the skin layer, ground tissue rests between dermal and vascular tissue. It stores energy and is also involved in photosynthesis. (in leaves). Vascular tissue is the conductive tissue, which includes the xylem and phloem that transport nutrients. Parenchyma, Collenchyma and Sclerenchyma, cells of xylem (tracheids and vessel elements) and phloem represent the different types of cells in plants.

59) Roots anchor the plant firmly to the ground and carry water and other minerals from the soil to the plant body. There are two types of root systems namely tap root system (single root that grows deep) or fibrous root system (has several main roots each with multiple sub-roots). Some roots such as carrots, beetroots store food in their roots.

60) Stems support the plant body and conduct water (xylem) and nutrients (phloem) to the leaves and other parts of the plant. There are two types of stem namely green stem (thin and bending) and woody stem. (Thick and hard)

61) Leaves perform the important task of synthesizing food materials by photosynthesis. Leaves have a central stalk, the lamina or blade and veins.

Leaves may be of different shapes like needle leaves or broad leaves. Broad leaves are further differentiated into simple or compound leaves. (each stalk having several leaflets)

62) Plants acquire nutrients from the soil through their root hairs. Symbiotic relationship with microorganisms assists plants in absorbing minerals from the soil. (eg, legumes- bacteria) Farmers use fertilizers to enrich the soil that is depleted of its nutrient content. Plants absorb water through the roots.

63) Flowers are the attractive reproductive structures of plants. A flower in general is made up of the colorful petals that are held together by the whorl of sepals attached to the receptacle. At the center of the flower is the pistil, the female reproductive part that holds the stalk like structure called the style. At the tip of the style lies the stigma. (the entry for pollen grains). The male reproductive part, namely the stamen (filament and the anther) develops along the base of the pistil. These anthers contain the pollen grains.

64) Seeds develop from the ovules. The fertilized ovum undergoes mitosis resulting in an embryo. The endosperm cell divides and differentiates into the endosperm tissue that nourishes the embryo. The integuments that surround the ovule thicken up to form the seed coat. The pericarp or the ovary wall becomes the fleshy and edible part of the fruit.

65) Seeds germinate when the conditions are favorable. These conditions generally include availability of water, light, warmth and oxygen. While the primary root develops from the root coat the hypocotyl pushes itself towards the surface. In dicots the 'plumule' is protected from damage by the two cotyledons. Once the cotyledons reach the surface they straighten and open up exposing the primary leaves and begin photosynthesis. In the case of monocots, the primary leaf is protected by the coleoptile (a cylindrical structure) till it reaches the surface.

66) Animals maintain homeostasis by means of an effective feedback mechanism. As soon as a sensor detects a change in a control variable it passes the information to the central control, which processes the information and activates an effector. The effector either corrects the variable to a preset point (in case of negative feedback) or allows the deviation to proceed (in case of positive feedback) to its conclusion.… [END OF PREVIEW]

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