Turn the revolving turret (2) so that the lowest power objective lens (eg. 4x) is clicked into position.
Place the microscope slide on the stage (6) and fasten it with the stage clips.
Look at the objective lens (3) and the stage from the side and turn the focus knob (4) so the stage moves upward. Move it up as far as it will go without letting the objective touch the coverslip.
Look through the eyepiece (1) and move the focus knob until the image comes into focus.
Adjust the condenser (7) and light intensity for the greatest amount of light.
Move the microscope slide around until the sample is in the centre of the field of view (what you see).
Use the focus knob (4) to place the sample into focus and readjust the condenser (7) and light intensity for the clearest image (with low power objectives you might need to reduce the light intensity or shut the condenser).
When you have a clear image of your sample with the lowest power objective, you can change to the next objective lenses. You might need to readjust the sample into focus and/or readjust the condenser and light intensity. If you cannot focus on your specimen, repeat steps 3 through 5 with the higher power objective lens in place. Do not let the objective lens touch the slide!
When finished, lower the stage, click the low power lens into position and remove the slide.
Your microscope slide should be prepared with a coverslip over the sample to protect the objective lenses if they touch the slide.
Do not touch the glass part of the lenses with your fingers. Use only special lens paper to clean the lenses.
Always keep your microscope covered when not in use.
Always carry a microscope with both hands. Grasp the arm with one hand and place the other hand under the base for support.
<span>The anterior end of an earthworm contains an organ that detects smells. Evidence of this is the way the earthworms responded to the ammonia. The earthworms backed away from the ammonia when it was waved near their anterior end, but they did not respond at all when the ammonia was waved near their posterior end.</span>
In immunology two types of immune response are described depending on whether there is prior contact with the antigen.
• At this first contact, only lymphocytes with receptors specific to the antigen in question are stimulated and lead to the production of antibodies capable of neutralizing it. The lymphocytes capable of recognizing a specific antigen are very few and the production of antibodies - of low intensity and limited duration - is detectable only after a period of latency of several days. This is called the primary response. The specificity of the resulting seropositivity, however, makes it possible to detect contamination (seroconversion).
• Upon re-contact with an antigen that has already triggered a primary response, specific antibody production is found to increase rapidly after a short latency period. The secretion of IgG then reaches levels much higher than those observed during the primary response, while that of IgM is of the same order. This early and intense response, called secondary response, most often results in the destruction of infectious agents before any clinical sign.
• Many centuries before the discovery of microbes, it was noted that people who developed a contagious disease without death were then specifically immunized against the disease, without being protected against others.
• The ability to react appropriately to an already received stimulus supposes the existence of a memory. The immune memory is based on the existence of memory B and T lymphocytes, resulting from the clonal expansion due to the first contact with the antigen. Their lifespan is significantly higher than that of other lymphocytes and their high reactivity gives its rapid and intense character to the secondary response.
Answer:
D) Asexual reproduction produces offspring that are genetically identical to the parent.
Explanation:
I am honestly not quite sure of this answer, but I was trying to read up on the topic and this is the answer I'm most confident in. It would make sense that the offspring are genetically identical to the parent because they would have no where else to get their genes/mix to form new ones. I really hope this helps!
Answer:
The behavior of chromosomes during meiosis and fertilization is responsible for most of the variation that arises in each generation. Three mechanisms contribute to genetic variation arising from sexual reproduction: independent assortment of chromosomes, crossing over, and random fertilization.
