Write about energy flow in an ecosystem.
Energy is an essential requirement for all living organisms. Solar energy is the only source of energy for the Earth. Solar energy is transformed to chemical energy by photosynthesis in plants (primary producers). Though lot of sunlight falls on plants, only 1% of this is utilized for photosynthesis. Some amount of energy is used by the plant for growth and the remaining is transferred to consumers by the process of eating. Thus energy enters the ecosystem through photosynthesis and passes through different feeding levels (tropic levels) The flow of energy through an ecosystem follows two laws of thermodynamics: 1. First law of thermodynamics states that “energy can neither be created nor destroyed, but can be converted from one form to another.” Ex: Energy for an ecosystem comes from the sun. It is absorbed by plants where it is converted and stored as chemical energy or solar energy is converted into chemical energy. 2. Second law of thermodynamics states that “whenever energy is transformed, there is a loss of energy through the release of heat.” Ex: Whenever energy is transferred between tropic levels, loss of energy takes place through respiration, running, hunting, etc.
What is DNA Polymorphism? Why is it important to study it?
A DNA polymorphism is any difference in the nucleotide sequence between individuals. These differences can be single base pair changes, deletions, insertions, or even changes in the number of copies of a given DNA sequence. SNPs (single nucleotide polymorphisms) are the most common type of DNA polymorphism in humans. An example of an SNP would be if a cytosine (C) nucleotide is present at a particular locus in one person’s DNA but a thymine (T) nucleotide occurs at the same locus in another person’s DNA. So, how can DNA polymorphisms be used for genetic mapping? Genetic mapping involves measuring the amount of recombination that occurs between two markers during meiosis. If there is a low amount of recombination between markers, then they are linked (i.e., located very close to each other on the same chromosome). Originally, the markers used by geneticists for genetic mapping experiments included alleles of genes that produced different physical phenotypes (traits). For example, one might perform crosses in flies with different eye colors and wing shapes to see if the genes associated with these phenotypes are linked. If the genes are linked and the chromosomal location of one of the two genes is known, then the second gene can be successfully “mapped” to a chromosomal location near the first. DNA polymorphisms can be used in much the same way as these physical phenotypes. Different forms of DNA polymorphisms can be tracked using a variety of techniques. Some of these techniques include Southern blots, PCR (polymerase chain reaction), and hybridization techniques using DNA microarray chips. These techniques allow us to determine if a specific DNA polymorphism is linked to a specific phenotype. We can then conclude that the gene responsible for a given phenotype maps to a chromosomal location very close to the DNA polymorphism.
deciduous plants shed their leaves during hot summer or in autumn. this process of shedding of leaves ids called abscission. apart from physiological changes what anatomical mechanism is involved in the abscission of leaves?
abscission is the process of separation of leaves, flowers, and fruits from plants after the formation of an abscission zone at the base of their petioles, peduncles and pedicels. it is a physiologically determined program of cell separation. when an autumn leaf falls, the breaking point is an abscission layer near the base of the petiole. A well-defined abscission zone is characterized by isodiametric cortical parenchyma cells, the absence of perivascular fibers, and shortened vascular elements. The abscission-zone cells proximal and distal to the separation layer contain high levels of starch. Separation, preceded by swelling of cell walls and the dissolution of the middle lamella between adjacent separation-layer cells, begins in the abaxial cortical parenchyma in the region of the vascular tissue. There is a rapid increase in total protein content in the separation-layer cells following ethephon treatment and a corresponding decrease in levels of pectic substances in the transverse walls of separation-layer cells. Neither cell divisions, tylose formation, nor lignification occurred in abscission-zone cells up to the time of leaf drop. The weight of the leaf then with the help of the wind, causes a separation within the abscission layer.