Biology Test-2

Snow-blindness in Antarctic region is due to inflammation of cornea due to high dose of UV-B radiation.

Snow blindness is an acute conjunctivitis and superficial epithelial keratitis caused by exposure to ultraviolet light or what Ernest Shackleton described as “the violet rays.” It occurs because ultraviolet exposure is increased by the light reflecting from the snow. Ultraviolet exposure will also be higher at altitude (e.g., on the Antarctic plateau) and with clear skies. Exposure to ultraviolet light will be greater on bright sunny days, and Edward Atkinson, the senior surgeon on Scott's Terra Nova expedition (1910–1913) says that “fifteen minutes of such a day will cause snow-blindness.” The symptoms were described (to a lay readership) by Macklin as “a condition of acute and sudden congestion of the eyes, affecting chiefly the conjunctivae. The little blood-vessels become dilated, producing a prickly sensation of grit in the eyes, which become painful in strong light. The condition may become worse, leading to a marked congestion with heavy discharge and total blindness.” These symptoms are clearly describing snow blindness, but some of the symptoms described are not typical of what is now described as photokeratoconjunctivitis, and there are other possible causes of some of the eye problems.

Decondensation of chromosomes occurs during telophase.

At the beginning of the final stage of karyokinesis, i.e., telophase, the chromosomes that have reached their respective poles decondense and lose their individuality. The individual chromosomes can no longer be seen and each set of chromatin material tends to collect at each of the two poles. This is the stage which shows the following key events:

Chromosomes cluster at opposite spindle poles and their identity is lost as discrete elements. Nuclear envelope develops around the chromosome clusters at each pole forming two daughter nuclei. Nucleolus, golgi complex and ER reform.

The correct option isa-(iii), b-(iv), c-(ii), d-(i).

Plants obtain iron in the form of ferric ions Fe³⁺. It is reversibly oxidized from Fe²⁺ to Fe³⁺ during electron transfer. It activates catalase enzyme, and is essential for the formation of chlorophyll.

Plants obtain zinc as Zn²⁺ ions. It activates various enzymes, especially carboxylases. It is also needed in the synthesis of auxin (IAA).

Boron is absorbed as BO₃^3- or B₄ O₇^2-. Boron is required for uptake and utilization of Ca²⁺, membrane functioning, pollen germination, cell elongation, cell differentiation and carbohydrate translocation.

The best defined function of manganese is in the splitting of water to liberate oxygen during photosynthesis.

Energy flow in an ecosystem is unidirectional.

The energy flow is the term related to flow of an energy from one organism to another. Ecosystem is the system where living and nonliving components interact with each other.

First of all, sunlight energy is used by the producer for synthesizing their food by the process of photosynthesis. Carbon dioxide and water are also involved in this process and glucose is the product. Glucose provides energy to the organism because breakdown of glucose by means of respiration leads to release of energy in the form of ATP. Producer acts as the lowest level in the ecological pyramid of energy.

According to Lindeman’s law of energy, 10% of energy is transferred from one level of ecological pyramid to another level. Because most of the energy is released in the form of heat and it is also utilized in performing the metabolic activities of organisms. That’s why there will be transferring of less energy from one trophic level to another trophic level. And the organisms which are found at the top most trophic level will get less energy as compared to previous trophic levels.

Thus, we can say that the less energy is transferred to the next trophic level. That’s why the flow of energy in an ecosystem is described as the direction of energy from the sun to the producer and then to the next level of the pyramid of energy.

That’s why flow of energy in the ecosystem is unidirectional in nature.

Malignant tertian/subtertian fever is caused by plasmodium falciparum.

Malignant tertian (plasmodium falciparum), in which the cold stage is less pronounced and the fever stage is more prolonged and intensified (if the fever is recurring it occurs every 2^nd day). However, the fever is usually continuous or only briefly remittent.

Plasmodium falciparum can cause severe malaria because it multiples rapidly in the blood, and can thus cause severe blood loss (anemia). In addition, the infected parasites can clog small blood vessels. When this occurs in the brain, cerebral malaria results, a complication that can be fatal.

Five species of plasmodium (single-celled parasites) can infect humans and cause illness.

Plasmodium falciparum (or plasmodium falciparum) causes Malignant tertian plasmodium malariae (or P. malariae), Humans occasionally become infected with Plasmodium species, with a fever every 3^nd day plasmodium vivax (or P. vivax) with a fever every 2^nd day, can remain dormant in the liver plasmodium ovale (or P. ovale) with a fever every 2nd day, can remain dormant in the liver plasmodium knowlesi (or P. knowlesi) fever pattern is daily.

Evolution of Giraffe is an example of natural selection.

Natural selection was given by Charles Darwin, according to it those populations which are a better fit (reproductively fit) in an environment will be selected by nature and will survive more.It can be understood with the example of industrial melanism -

In a collection of moths made in the 1850s, i.e., before industrialisation set in, it was observed that there were more white-winged moths on trees than dark-winged or melanised moths.

Binding to DNA and forming a gene hormone complex steroid hormone influence the cellular activities.

Steroid hormones are the group of hormones that relate with the class of chemical compounds called steroids. There are three secretory glands which secrete the steroids namely-the adrenal cortex, testes, and ovaries-and during pregnancy by the placenta. All steroid hormones are taken from cholesterol. Many physiological processes are regulated by the steroid hormones, including the development and function of the reproductive system. The binding of a steroid hormone forms a hormone-receptor complex that affects gene expression in the target cell’s nucleus. The binding of a non-steroid hormone activates a secondary messenger that puts its effect on various processes inside the target cell. The steroid hormone then passes through the plasma membrane of a target cell and sticks to intracellular receptors which are present in the nucleus or the cytoplasm. The cell signaling pathways induced by the steroid hormones help to regulate the specific genes on the cell’s DNA. On the basis of their receptors, steroid hormones have been classified into five groups-Glucocorticoids, mineralocorticoids, androgens, estrogens, and progesterone.

Colostrum the yellowish fluid, secreted by mother during the initial days of lactation is very essential to impart immunity to the new born infants because it contains Immunoglobulin A.

During pregnancy, mammary glands of the female undergo differentiation and at the end of pregnancy, milk secretion starts from them. This process is called lactation. The yellowish milk produced during the initial days of lactation is called colostrum. It is rich in carbohydrates, proteins and antibodies and has very fat. Breastfeeding is very important for an infant because it provides them with nutrition and immunity. There are many types of antibodies produced in our body. Some of them are IgM, IgA, IgE, IgG. Normally these antibodies are found in the blood and hence, show humoral immune response. Colostrum contains a large amount of IgA (Immunoglobulin A) antibody, which provides immunity to the child and hence protects the child from many infections.

Two friends are eating together on a dining table. One of them suddenly starts coughing while swallowing some food. This coughing would have been due to improper movement of epiglottis.

The epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It prevents the entry of food into the larynx, and directs it to the oesophagus. Due to improper movement of epiglottis, one may suddenly start coughing while swallowing some food.

The correct answer isMetamorphosis.

Metamorphosis:

• It is a biological process through which ananimal physically develops after birth or hatching.
• It involves a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation.
• The metamorphosis is aGreek word that means transformation ortransforming.

Fertilization:

• It is also known asinsemination, pollination,syngamy, and impregnation.
• It is the fusion of gametes to initiate the development of a new individual or offspring.

Budding:

• It is a type ofasexual reproduction.
• In this, a new organism develops from an outgrowth due to cell division at one particular site.
• Bud is the small bulb-like projectioncoming out from the yeast cell.
• Reproduction is asexual, therefore the newly formed organism is a clone and excepting mutations is genetically identical to the parent organism.

Cloning:

• It is the process of producing individuals withidentical or virtually identical DNA, either artificially or naturally.
• ​It iscoined by Herbert J. Webber.
• Its application in Biotechnologyis very prevalant.

Ependyma is the thin epithelium lining in the ventricles of the brain and the central canal of the spinal cord. These are ciliated simple columnar epithelium cells. These are involved in the production of cerebrospinal fluid (CSF).

Glyoxylate cycle reactions related to plant photosynthesis, peroxisomes are involved.

The glyoxylate cycle centers on the conversion of acetyl-CoA to succinate for the synthesis of carbohydrates. At later stages of plant carbohydrates and biosynthetic precursors are provided by photosynthesis and thus, the glyoxylate cycle is no longer essential. Basic function in plants the glyoxylate cycle occurs in special peroxisomes which are called glyoxysomes. This cycle allows seeds to use lipids as a source of energy to form the shoot during germination. The seed cannot produce biomass using photosynthesis because of lack of an organ to perform this function.

Epithelial cells of the intestine involved in food absorption have on their surface microvilli.

Microvilli are the tiny hair like structures which are present on the surface of epithelial cells.

These are present in the small intestine.The function of the microvilli is to increase the surface area for the absorption of water and nutrients directly into the bloodstream from the digested or partially digested food.

The genetic defect adenosine deaminase (ADA) deficiency may be cured permanently by introduction of genes isolated from the bone marrow cells which produce adenosine deaminase (ADA), into the cells of the patient at early embryonic stages.

Adenosine deaminase(ADA)is an inherited disorder. It is a metabolic disorder. The mutation in adenosine deaminase (ADA)genes causes this disorder. It mainly affects the immune system and causes severe combined immunodeficiency (SCID). It was recognized as the first immunodeficiency disorder. The immune lacks the protection against bacteria, viruses, and fungi. This type of disorder is present in infancy, childhood, adolescence, or adulthood. The growth of the affected children is slower than the healthy children. The development is delayed in affected children.

The Adenosine deaminase enzyme is attached to the adenosine deaminase (ADA)gene. If there is a decreased level of adenosine deaminase (ADA)in blood then the person has adenosine deaminase (ADA)deficiency. Bone marrow transplant, adenosine deaminase (ADA)enzyme in PEG vehicle can be used for the treatment of this disorder. The treatment adenosine deaminase (ADA)is a very complex process. Enzyme replacement therapy involves the injection of adenosine deaminase (ADA)to the patient. Introduction of genes isolated from bone marrow cells, it produces adenosine deaminase (ADA), into the cells of the patient at early embryonic stage. It can only cure permanently with the help of gene therapy.

Significanceof classification is:

• It makes the study of such a wide variety of organisms easy.
• It projects before us a good picture of all life forms at a glance.
• It helps us understand the inter-relationship among different groups of organisms.
• It serves as a base for the development of other biological sciences such as biogeography etc.
• Various fields of applied biology such as agriculture, public health, and environmental biology depend on the classification of pests, disease vectors, pathogens and components of an ecosystem.