Introduction:
Scientists believe that the gymnosperms developed from an extinct phylum whose members reproduced through spores (E. Taylor, T. Taylor, & Krings, 2009). The first true gymnosperms, however, produced seeds instead of spores. As a result, the evolution of the seeds became a fundamental adaptation of the gymnosperms to the dry conditions on land. The second factor that made the group successful on land was the development of pollen grains, which transported and protected the male gametes. Hence, unlike the seedless vascular plants, the gymnosperms became less dependent on the aquatic conditions for the success of fertilization. Instead, they gained the ability to disperse the male gametes through the wind. The leaf morphology of gymnosperms such as the conifers allowed the gymnosperms to thrive when the earth became much drier in the Permian. Unlike the gymnosperms, angiosperms possess flowers, and their embryos have an ovary that forms a fruit. The gymnosperm embryos on the scales of female cones have relatively less protection.
Angiosperms’ oldest group, the Magnoliids, gave rise to the dicotyledon and monocotyledon plants (Campbell & Reece, 2007). The two groups evolved efficient vascular tissues, embryos enclosed in seed coats and desiccation-resistant leaves in order to adjust to the dry conditions. In addition, the groups became successful on land because their male gametes were mainly insect pollinated. Insect pollination, therefore, made fertilization effective and increased the specialization of the flowers. Some angiosperm groups such as the grasses, however, improved their adaptation for wind pollination and dominated most of the planet’s dry regions.
Hypothesis:
The present experiment tested the theory that Gymnosperms and angiosperms have evolved structures similar in function in order to adapt to the land conditions.
Materials:
Pine’s ovulate (female) and staminate (male) cones
Pine leaf
Monocotyledon and dicotyledon plant seeds
Lily flower
Fruit
Razor blade
Method:
The leaves, as well as the male and female cones of the pine, were viewed and illustrated. Monocotyledon and dicotyledon seeds were also examined for the presence of the seed coat. Next, a razor blade was used to cut the lily flower vertically. The half flower was then drawn. A fruit was also cut in order to reveal the enclosed seeds.
Results:
The observed results were illustrated as shown in the Figure 2, 1, 3, and 4
Figure 1. Pine’s ovulate and staminate cones. (a) The dwarf and long shoots with ovulate and staminate cones. (b) Different pine branches and leaves. (c) Cluster of the staminate cones. (d) An ovulate cone in the three different stages of development.
Figure 2. Staminate cone. The figure shows the vertical section of a staminate cone.
Figure 3. Patterns on the lily flower. The diagram shows the pattern of the pistil, stamen, sepals, and petals on the lily flower.
Figure 4. Vertical section of a lily flower. The figure shows the floral formula of the lily flower.
Figure 1 describes the needle-shaped leaves that adjust the pine to the dry conditions by reducing the water loss caused by evapotranspiration. It also explains that the seeds of ovulate cones lack seed coats. Ovulate cone is also larger than the staminate cone as shown in Figure 2. The Figure 3 specifies the number of the pistil, stamen, sepals, and petals in the lily flower. It also shows that the plant’s leaves have parallel veins; therefore, the plant is a monocotyledon. Figure 4 describes the superior and syncarpous ovary observed in the lily. In addition, it shows that the lily’s fruit is a capsule. The investigator concluded that the angiosperms and gymnosperms have features that adapt them to the dry conditions.
Conclusions:
The experimental observation showed that the gymnosperms and angiosperms developed various characteristics that adapt them to the dry conditions. For example, the staminate cone is adapted for wind pollination while the angiosperm flower has features that promote insect pollination. In addition, the angiosperm seed coat reduces the water loss from seeds while the fruit enclosing them encourages seed dispersal by animals. In the pines, the needle-shaped leaves lower the evapotranspiration rate and, hence, reduce water loss. Therefore, the experiment was successful because it supported the hypothesis.
References
Campbell, N. A. & Reece, J. B. (2007). Biology. San Francisco, CA: Benjamin Cummings.
Taylor, E. L., Taylor, T. N., & Krings, M. (2009). Paleobotany: The Biology and evolution of fossil plants. Waltham, MA: Academic Press.
