Answer:
Transmission electron microscope (MET): allows sample observation in ultra-thin sections. A TEM directs the electron beam towards the object to be increased. A part of the electrons bounce or are absorbed by the object and others pass through it forming an enlarged image of the specimen. To use a TEM, the sample must be cut into thin layers, not larger than a couple thousand thousands of angstroms. A photographic plate or a fluorescent screen is placed behind the object to record the enlarged image. Transmission electron microscopes can increase an object up to a million times.
A scanning electron microscope creates an enlarged image of the surface of an object. It is not necessary to cut the object into layers to observe it with an SEM, but it can be placed in the microscope with very few preparations. The SEM scans the image surface point by point, unlike the TEM, which examines a large part of the sample each time. Its operation is based on traversing the sample with a very concentrated beam of electrons, similar to the scanning of an electron beam on a television screen. The electrons in the beam can disperse from the sample or cause secondary electrons to appear. Lost and secondary electrons are collected and counted by an electronic device located on the sides of the specimen. Each point read from the sample corresponds to a pixel on a television monitor. The higher the number of electrons counted by the device, the greater the brightness of the pixel on the screen. As the electron beam sweeps the sample, the entire image of it is presented on the monitor. Scanning electron microscopes can enlarge objects 200,000 times or more. This type of microscope is very useful because, unlike TEM or optical microscopes, it produces realistic three-dimensional images of the object's surface.
Sexual reproduction offers genetic variation, as the offspring are a combination of 2 sets of genes opposed to one. This ultimately leads to evolution and the adaption to changing environments :)
Difference between Alpha, Beta and Gamma Radioactive Decay. Difference between Alpha, Beta and Gamma radioactive decay can be summarized as follows: Alpha decay forms new element with two fewer protons and two fewer neutrons; Beta decay forms new element with one more proton and one fewer neutron.
Answer: Option A
Explanation:
An endosperm is defined as the tissue which are produced inside the seeds during fertilization. As the endosperm surrounds the embryo, it acts as the food storage for the embryo and provide nutrition.
During embryo development , endosperms supports enlargement of cotyledons which helps in storage function and stores fats and starch and provide nourishment to the embryo.
for example cereal crops or grains are primarily endosperm which stores fat and starch and are edible fruits.
Hence, the correct option is A, endosperm can be a cotyledon which functions as a source of food for embryo.
The independent variable is the variable that is being changed in an experiment. It is also called the manipulated variable. In this case, it would be the amount of sunlight. The dependent variable would be the variable that is being studied. In this case it would be the length of sleep of the mice. The constants would be the variable that are supposed to have an effect on the dependent variable however it is held constant so as to clearly see the effect of the independent variable.
