Second Quarter Examination in Science 7 (STE)

During a Science activity at Lubao NHS, the Grade 7 students collected water samples from a nearby fishpond. Their teacher, Mr. Dela Cruz, explained that the water might contain very tiny living things that cannot be seen with the naked eye. He asked the students to observe the samples carefully and identify any microorganisms present. To do this, the students needed to use a specific laboratory instrument that can make very small objects appear larger. Which laboratory apparatus should the students use to observe microorganisms that are too small to be seen by the naked eye?

• Beaker

• Graduated cylinder

• Microscope

• Platform balance

The Grade 8 students are conducting an experiment to observe microorganisms in pond water collected from a nearby barangay. While setting up the compound microscope, Jimin notices that the image in the microscope is too dark. Her teacher reminds her that proper lighting is important when observing specimens. Jimin adjusts the mirror to reflect lighter but realizes she also needs to tilt the microscope for better illumination on the slide. Which part of the microscope should Jimin adjust to tilt it and properly illuminate the specimen?

• A. Body tube

• B. Inclination joint

• C. Mirror

• D. Stage

After placing a specimen under the microscope, the image appears blurry. Which adjustment should you make first to bring it into clear focus?

• Base

• Body tube

• Fine adjustment knob

• Revolving nosepiece

Arrange the steps below in the correct order for focusing a specimen under a microscope.

• I, II, III, IV

• I, III, IV, II

• I, IV, II, III

• I, III, II, IV

A plant cell being observed is seen at the uppermost part of the field of view. If you want to center the specimen, which direction should you move the slide?

• Move the slide to the top

• Move the slide to the left

• Move the slide to the right

• Move the slide to the bottom

When carrying a microscope, which parts should you hold securely? To avoid damage when moving a microscope, which parts should you hold securely?

• A. Arm and base

• B. Arm and stage

• C. Eyepiece and base

• D. Draw tube and base

When viewing a plant cell under high magnification, which structure would you likely observe and why?

• Chloroplasts – They are large organelles that contain pigments, making them easier to see at high magnification.

• Mitochondria – They are too small to be seen clearly even with high magnification in most classroom microscopes.

• Nucleus – It is a large, central structure that can be observed with high magnification and is essential to cell function.

• Ribosomes – These structures are too small to be visible with standard classroom microscopes, even at high magnification.

Which of the following is the best method to view the internal structures of a cell, such as the nucleus and mitochondria, using a microscope?

• Observe only under natural light.

• Use low magnification and bright light.

• Use medium magnification without adjusting focus.

• Use high magnification with proper focusing and staining.

When using a microscope to observe the mitochondria of a cell, which of the following steps should be done first?

• Increase the magnification

• Focus using the coarse adjustment knob

• Apply a stain to highlight the mitochondria

• Place the slide under the highest magnification objective

While observing a sample under high magnification, you spot a structure with a double membrane and DNA. Which organelle does this likely represent, and what is its main function?

• Chloroplast – Responsible for photosynthesis in plant cells.

• Cytoplasm – Provides a medium that supports and surrounds the organelles.

• Mitochondrion – Responsible for energy production in the cell.

• Nucleus – Controls cell activities and stores genetic information.