NEET Test 140

Double fertilization occurs in Angiosperm. In this fertilization, one male gamete enters to the ovule and fuse with the egg cell result into the formation of diploid zygote while another male gamete fuse with the polar nuclei (2n) or secondary nucleus present in the center results into the formation of primary endosperm nucleus(3n) and that will be triploid in nature. Endosperm will form from the primary endosperm nucleus. They provide nourishment to the developing embryo. Embryo will be able to survive when endosperm grows faster. Synergids guide the pollen tube and it degenerates after fertilization.

One chromosome of each homologous pair comes from the mother (called a maternal chromosome) and one comes from the father (paternal chromsosome). Homologous chromosomes are similiar but not identical. Each carries the same genes in the same order, but the alleles for each trait may not be the same.

Marine bacteria evolved. Along with this, colonial multicellular filamentous algae evolved in oceans during the Cambrian period. This occurred about seven crore years ago. The Cambrian period, part of the Paleozoic era, produced the most intense burst of evolution ever known. The Cambrian Explosion saw an incredible diversity of life emerge, including many major animal groups alive today.

Covalent crystals are formed by sharing valence electrons between two atoms resulting in the formation of a covalent bond.

The covalent bonds extend in two or three dimensions forming a giant interlocking structure called a network. 

Diamond and graphite are good examples of this type.

Silicon (Si): Covalent solid 

Sulphur (S₈): Molecular solid

Phosphorus (P₄): Molecular solid 

Iodine (I₂): Molecular solid

They are called pathogens, due to which many types of diseases are born. It contains viruses, bacteria, fungi, parasites, etc. It can make sick any organism, plant or other micro organisms. Diseases caused by organisms in humans are also known as pathogenic diseases. Bacteria is a prokaryotic organism and biodegradable while DDT is a nonbiodegradable pollutant and undergo biological magnification.

The innermost layer of cortex forms endodermis, which has compactly arranged barrel shaped cells. The primary thin walled endodermis shows suberin deposition in form of bands or strips that run around the radial and end walls of the cells and forms Casparian strips.

Simple columnar epithelium are found in the stomach, small intestine, large intestine, rectum, fallopian tubes, endometrium, respiratory bronchioles and lining of uterus. In essence, they are found in parts of the respiratory, digestive and reproductive tracts where mechanical abrasion is low, but secretion and absorption are important.

Hence, the image of the needle is 6.7 cm away from the mirror. Also, it is on the other side of the mirror. The image size is given by the magnification formula. 

The height of the image is 2.5 cm. The positive sign indicates that the image is erect, virtual, and diminished. If the needle is moved farther from the mirror, the size of the image will reduce gradually.

Carbohydrates in the chyme are hydrolyzed to disaccharides by pancreatic amylase. The starch is converted into isomaltose, maltose, and dextrins. The intestinal juice converts the disaccharide to monosaccharides. The nucleic acids are broken down to form nucleotides by the nucleases present in the pancreatic juice, these nucleotides are further reduced to form nucleosides by the intestinal juice with the enzyme nucleosidases and nucleotidases.