Which of the following is a characteristic of all angiosperms?
A) carpels that contain microsporangia B) free-living gametophyles C) ovules that are not contained within ovaries D) double internal fertilization
The Correct Answer and Explanation is:
The correct answer is D) double internal fertilization.
Explanation:
Angiosperms, or flowering plants, are a highly diverse and dominant group of plants that are characterized by several unique features, one of which is double internal fertilization. This process is a hallmark of angiosperms and is critical for the formation of seeds.
Here’s a breakdown of the key concepts related to the characteristics of angiosperms:
- Double Internal Fertilization (D):
Double fertilization is unique to angiosperms and involves two separate fertilization events within the ovule. The first event occurs when one sperm cell fuses with the egg cell to form a diploid zygote, which will develop into the embryo. The second event involves the fusion of a second sperm cell with two other nuclei in the central cell of the ovule, forming a triploid cell that will develop into the endosperm. The endosperm provides nourishment to the developing embryo. This dual process ensures the proper formation of both the embryo and the nutrient-rich endosperm, which is crucial for seed development and germination. - Carpels that Contain Microsporangia (A):
Carpels are the female reproductive structures of angiosperms, but they do not contain microsporangia. Microsporangia are found in the male structures, specifically the anthers of stamens. Carpels contain ovules, not microsporangia, which are important for the production of female gametes. - Free-Living Gametophytes (B):
In contrast to some other plant groups, angiosperms do not have free-living gametophytes. Their gametophytes are highly reduced and are contained within the reproductive structures. The male gametophyte is the pollen grain, and the female gametophyte is the embryo sac, both of which are contained within the flower. - Ovules Not Contained Within Ovaries (C):
In angiosperms, ovules are contained within the ovaries, which are part of the carpel. This is in contrast to gymnosperms, where the ovules are exposed on cone scales. In angiosperms, the ovary surrounds and protects the ovules, facilitating fertilization and seed development.
Thus, double internal fertilization is the defining feature of angiosperms, setting them apart from other plant groups.