Hello, everyone. In our last lesson, we talked about the anatomical structures of flowers. Now we're going to talk about the different types of flowers that you can find on different types of angiosperms.

Okay, we previously discussed things like sepals, petals, anthers, filaments, and things like that. The structures that you find within a flower. But these structures can vary depending on which type of flower you have. There are complete flowers, incomplete flowers, perfect flowers, monoecious flowers, and dioecious flowers. What we learned about previously were complete flowers. They contain sepals, petals, stamen, and pistils. So, remember that stamen includes the anther and the filament, which are the male structures that create pollen and sperm. And then, pistils include the stigma, style, and ovaries, which are the female components of the flower, creating the egg and eventually the seed or fruit. Now, if a flower is missing any of those four structures, it is considered an incomplete flower. Otherwise, it is a complete flower. Some examples of complete flowers are hibiscus flowers, roses, pea plants, and tulips. There are many more examples, but those are just a couple.

Okay, now let’s talk about the perfect flower. You may think that the perfect flower and the complete flower are probably the same thing. It’s actually not true. They have confusing names. You would think a complete flower would be a perfect flower, but in fact, it's not. A perfect flower is going to be a flower that is bisexual, meaning it has both male and female structures in the same flower, which means it has a stamen and pistils. Now, you may think, oh, well then it’s probably a complete flower. No, because it doesn't have to have sepals and it doesn't have to have petals and it can still be qualified as a perfect flower as long as it's got a stamen and a pistil. So, perfect flowers can be complete flowers, but complete flowers are not always perfect flowers.

Monoecious and dioecious are going to be two other types of flowers. So, monoecious and dioecious, you’ve heard these terms used before, generally when talking about animals and the sexes of animals. Monoecious plants, or monoecious angiosperms are going to have unisexual flowers, meaning that the entire flower is either male or female. But, these male and female flowers are found on the same plant. So what that’s going to look like is if we have a monoecious species of angiosperm, we’re going to have male flowers, and we’re going to have female flowers on the same plant. This is monoecious. And, generally, when we talk about monoecious organisms, we're talking about hermaphroditic organisms, organisms that possess both qualities of both sexes, and these angiosperms do fit that category.

Now, dioecious flowers, or dioecious angiosperms also have unisexual flowers, meaning that they have either male-only flowers or female-only flowers. However, these are found on completely different plants. So, if this species is dioecious, we're going to have one male plant and one female plant. That is a dioecious species of angiosperm. And that’s because dioecious generally refers to two different sexes. Human beings are dioecious. There are individuals that are solely male, and there are individuals that are solely female. The same thing is happening with these plants.

Examples of plants include squash and corn, which have both male and female flowers on the same plant. Some examples of dioecious plants, or dioecious angiosperms, would be willow trees, holly, sassafras, and also poison ivy. These are just some examples of the two different categories.

Now, since we talked about flowers, let's talk about the different forms of pollination that can occur with these flowers. First, we'll discuss cross-pollination. Cross-pollination is where pollen is transferred from one plant in the species to a completely different plant in the species. This is preferred in the reproduction of angiosperm plants because it allows for genetic diversity. It is sexual reproduction. This is how two separate individuals mix their genetics to create a zygote and eventually a seed or a fruit, which will create the new plant.

This is in contrast to self-pollination. If an angiosperm self-pollinates, it is able to take pollen from its own stamen and fertilize its own egg in the ovary. This is not particularly preferred because it does not introduce new genetic diversity; it is essentially cloning. While self-pollination is not preferred, some plants also can perform it if necessary, but cross-pollination is favored for its contribution to genetic diversity.

Now, let's talk about double fertilization. Angiosperms perform a unique process called double fertilization. Usually, you think about fertilization involving sperm fertilizing the egg to create a zygote; that's single fertilization, and that's how a lot of reproduction occurs. Angiosperms, however, do double fertilization. This is where one sperm fertilizes the egg to create a zygote, and another sperm is used to fertilize what's called the polar nuclei, which will become the endosperm. The endosperm serves as the nutritional substance inside the seed that allows the baby plant to grow. You can think of it like the yolk of an egg, providing sustenance to the developing embryo. This unique characteristic of double fertilization is very important for angiosperms.

Okay, everyone. Let's move on to our next topic.