Plant Diversity

To start the exercise, first split up into groups and find a station with a compound microscope, dissecting microscope and one prepared slide.

HYPOTHESES: The alternative hypothesis for this experiment might be that plants have specific adaptations that allow them to survive and reproduce in their own individual terrestrial environments. The null hypothesis for this experiment is that all plants have the same adaptations to live in terrestrial habitats.

Find the prepared slide at your station and place it on the stage of the compound microscope. Then, secure it between the stage clips.

Next, find the light switch on the side or back of the microscope and turn it on to illuminate the slide from below.

Adjust the lenses until the 10X lens is positioned above the slide.

Now, look through the eye piece of the microscope and turn the large course adjustment knob on the side of the microscope to bring the slide into focus.

After course adjustment, the smaller fine adjustment knob can be used to further refine the focus. Do this until the material on the slide becomes clear.

For each slide there are several key structures that you will need to sketch in Table 1. Click Here to download Table 1

For moss antheridium, identify the areas where sperm are formed. These areas should be darker than surrounding regions and oblong in shape. Sperm are released from these structures and swim to the archegonia.

For moss archegonia, identify the eggs. These are circular in shape and are located at the bottom of a long dark tube called the vent. Once fertilized, the new embryo will be retained within the structures surrounding the egg for protection.

Then, for the onion stomata, identify the stomata. These are the circular structures with two dark spots on either side. These dark spots are the nuclei of the guard cells that surround the pore and control its opening and closing.

For conifer pollen grains, notice the two wings on either side of each pollen grain. These allow the pollen to be blown by the wind to the female ovule. Also, notice the dark spots within the pollen grain. These are the nuclei.

NOTE: For this experiment, you'll be testing the same hypotheses, but you will leave the lab behind and venture outside to explore plant adaptations in the local environment. For safety, make sure to wear proper clothing and sun protection if needed.

Once your instructor has taken you to the designated outdoor location, try to identify plants in each of the three major groups: non-vascular, seedless vascular, and seeded vascular.

Using Table 2, fill out information for at least 10 plants listing the major group, specific adaptations and a brief sketch for each. Click Here to download Table 2

Where possible, try to identify different adaptations than the ones we've discussed so far. These include traits such as leaf size and shape, plant height, or flowers. To find plants of all three major groups, you may need to look in more than one location or habitat.

Before returning to the lab, each group member should collect a leaf, flower or other structure from a plant of their choosing for further analysis.

Back in the lab, place the one group member’s specimen on the stage of the dissecting microscope.

Next, find the light switch and turn it on to illuminate the sample.

Similar to the compound microscope, you will next need to adjust the fine focus knobs to bring the sample into view.

For leaves, view the stomata under maximum magnification. These will look like very small dots on the surface of the leaf.

Next, tear the leaf in half and see if you can find the clear cuticle that covers the surface of the leaf.

Examine the venation of the leaf, which allows for transport of resources.

When observing flowers, look for pollen, which will appear as yellow dust on the anthers of the flower.

Next, identify the stigma, a long structure protruding from the flower and ending with a round sticky tip. This is where pollen would land allowing sperm to travel down to the ovule at the base of the flower to form a seed.

Notice whether or not there is evidence of a fruit or seed in the base of the flower.

Make a sketch of each of the samples within your group.

When the exercise is complete, turn off the light on both microscopes. Remove the prepared slide from the stage of the compound microscope and return it to the instructor.

Finally, remove the samples you collected from the dissected microscope and discard them into the trash and clean the microscope stages, if necessary.

Compare the adaptations you observed for the plants you examined outdoors with the adaptations other student groups noticed.

Take note of any similar adaptations across the different plant species.