What structures should you identify when observing moss under a compound microscope?

When observing moss slides, identify the antheridium where sperm are formed—these appear as darker, oblong regions. Also locate the archegonia, which contain circular eggs at the bottom of a long dark tube called the vent. After fertilization, the embryo is protected within structures surrounding the egg.

How do you properly focus a prepared slide on a compound microscope?

First, position the 10X lens above the slide and turn on the light to illuminate from below. Use the large coarse adjustment knob to bring the slide into rough focus while looking through the eyepiece. Then use the smaller fine adjustment knob to refine focus until the material becomes clear and sharp.

What adaptations allow conifer pollen grains to reach female ovules?

Conifer pollen grains have two wings on either side that allow them to be dispersed by wind to female ovules. Within each pollen grain are dark spots representing nuclei. These structural features enable effective pollination across distances in terrestrial environments.

What are guard cells and what role do they play in stomata function?

Guard cells are specialized cells that surround the stomatal pore on leaf surfaces. These cells contain nuclei visible as dark spots on either side of the circular stomatal opening. Guard cells control the opening and closing of stomata, regulating gas exchange and water loss in plants.

How do you examine plant specimens collected outdoors using a dissecting microscope?

Place the specimen on the dissecting microscope stage and turn on the light. Adjust the fine focus knobs to bring the sample into view. For leaves, examine stomata at maximum magnification and look for the clear cuticle covering the surface. Observe leaf venation for resource transport pathways.

What key features should you observe when examining flowers under magnification?

Look for pollen appearing as yellow dust on the anthers. Identify the stigma, a long structure protruding from the flower with a round sticky tip where pollen lands. Check for evidence of fruit or seed development at the flower's base, indicating successful reproduction and seed formation.

Why is it important to identify different plant adaptations across multiple habitats?

Different plant adaptations reflect how species survive in specific terrestrial environments. By observing plant adaptations across different species in various habitats, you can compare traits like leaf size, plant height, and flowers. This reveals how evolution shapes plant diversity and survival strategies across environmental conditions.

Plant Diversity

Concepts Instructor Prep Student Protocol

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Before plants colonized land from the sea, the continents were barren. Now millions of species of microbes, plants, and animals live on land, and it was the evolution of land plants that made all of this possible. To understand this staggering transformation, we need to understand what exactly plants are and how they evolved to meet the challenges of life on land.

There are certain characteristics that all plants share, from the tallest trees to the smallest moss. First, all plants are multicellular eukaryotes. Second, plants produce the photosynthetic pigment chlorophyll in organelles called chloroplasts, enabling them to produce their own food using energy from the sun. Third, all plants have cells that are surrounded by walls made of cellulose. Lastly, all plants have a life cycle characterized by the alternation of generations, defined as the transition between haploid and diploid multicellular stages over the life cycle. Here, generations refers to two different multicellular phases in the life cycle. One phase is the haploid gametophyte. The gametophyte produces gametes by mitosis, which fuse during fertilization to form a diploid cell, which then undergoes mitosis to develop into a sporophyte. The sporophyte, in turn, produces haploid spores by miosis, completing the cycle by giving rise to new gametophytes.

Although all plants share these characteristics, there are stark differences among the diverse plant lineages in how some of these characteristics are expressed. Let's examine this diversity. Land plants fall into three major groups, the nonvascular plants, the seedless vascular plants, and the seed plants. Each of these groups contains many thousands of species.

The mosses belong to the division Bryophyta. These relatively simple plants have three main characteristics, a lack of vascular tissue, the gametophyte is the dominant free-living stage of their life cycle, and the sporophyte is small, unbranched, and dependent on the gametophyte for nutrition.

The next major group of land plants to evolve was the seedless vascular plants, represented here by the division Monilophyta. This group includes the ferns and horsetails. These plants have true vascular tissue but do not produce seeds like the other vascular plants. The sporophyte is dominant and branched with a waxy cuticle and leaf pores called stomata that regulate gas exchange. The gametophyte is much smaller but is free-living in most members of this group. Fern spores and sperm both require liquid water for dispersal. The extensive root systems and vascular tissues are key innovations in seedless vascular plants that provide structural support and allow for efficient collection of water from the soil.

The seed plants were the next major group to evolve. There are two major lineages in this group, the gymnosperms and the angiosperms. Although they differ in many details, all gymnosperm and angiosperm seeds consist of an embryo and a store of food that is surrounded by a protective shell called the seed coat. The store of food provides the seedling with resources until it is able to feed itself. The gymnosperms include familiar trees like pines, spruces, and ginkgos. The sporophyte is the dominant life cycle stage in the gymnosperms. The gametophytes are very small and grow on male or female cones. Wind carries the male gametophyte, called pollen grains, to the female gametophytes. After fertilization, a female structure called the ovule, develops into a seed. The angiosperms, or flowering plants, were the next group of seed plants to evolve. This group is the most widespread and species-rich group of plants, including many familiar plants and trees like lilies, oaks, and apples. Like the gymnosperms, angiosperm sporophytes are large and free-living and the gametophytes are very small and separated into male and female forms. But in contrast to the gymnosperms, diverse animals can pollinate flowers in addition to the wind, collecting pollen as they visit flowers and distributing it as they leave to visit others. After pollination and fertilization, the ovary develops into a fruit that contains the seeds.

We have now completed our simplified tour of plant diversity that highlighted some key plant traits from vascular tissue to the evolution of fruits. Together, these adaptations enabled plants to dominate most terrestrial biomes. In this lab, you will investigate plant diversity by examining specimens from the different major lineages of plants and observing their structures in both the laboratory and field settings.

Print Procedure Steps

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Viewing Prepared Slides
- 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.
Observing Adaptations and Collecting Samples
- 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.
Results
- 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.