Sexual Reproduction

Sexual reproduction can be summarized in this section of the flow chart. As you can see, it is more of an extensive diagram compared to that of asexual reproduction:

BC 17

Seedless Plants: 

Seedless plants produce better in an conducive environment. That is an environment that is typically wet, allowing the sperm to swim up the ovule and the ovary of the plant. In seedless plants, there are two types of sexual reproduction that occurs. In Non-vascular plants such as mosses, the reproductive cycle is slightly different compared to that of an vascular plant such as a fern. Let’s examine each of these carefully.

Moss Life Cycle:

The diploid zygote begins the sporophyte stage and develops into an embryo that grows into a stalk and capsule. Meiosis occurs in the capsule and spores are produced. When spores fall to the ground, they can grow into thread like structure’s. These can grow into mature gametophyte’s. Sex cells are produced in reproductive structure’s of male and female moss gametophyte’s.  During a heavy dew or rain, the sperm swims to the egg, and fertilization occurs.

moss life

Fern Life Cycle:

Meiosis takes place inside each spore case to produce thousands of spores. Spores are ejected and fall to the ground. Each can grow into the prothallus, which is the gametophyte plant.  The prothallus contains the male and female reproductive structure’s where sex cells from. Water is needed for the sperm to swim to the egg. Fertilization occurs and a zygote is produced. The zygote is the beginning of the sporophyte stage, and grows into the familiar fern plant.

fern life

Seed Plants: 

Seed plant sexual reproduction is he other part of the flow chart. In seed plants, there needs to be an outside source to help plants reproduce. This usually occurs in terms of pollination. Pollination assist with fertilization, and hence a new seedling is formed. Similar to seedless plants, there are two ways that this can occur. Either through gymnosperms, such as cone tree’s,  or angiosperms, such as in lily’s. We will examine each carefully suing the following diagrams.

Gymnosperm Reproduction: 

In the cones, cells divide by meiosis to produce gametophyte plant structure’s. Eggs and food storage tissue are produced in  the ovule. Two sperm form inside each pollen grain.  Each pollen grain has tiny wings that help carry it to the female cone. Once it reaches the female cone, a pollen tube forms and fertilizes the egg. This process may take up to 15 months. The zygote produced during fertilization grows into an embryo. The embryo is a new, immature, sporophyte plant. One wing pine seed develops from each ovule  the seeds are eventually released from the female cone and grows into a sporophyte plant. gymnosperm life

Angiosperm Reproduction:  

Before understanding angiosperm reproduction, it is important to first understand the anatomy of a typical angiosperm flower, the lily. The important points of the diagram are as follows:

Male Reproductive Parts – anther & filament

Female Reproductive Part – style, ovary, ovule, & stigma

BC 24

Pollination happens when the pollen grains from the anther lands on the sticky stigma of the pistil. The pollen tubes grow from the pollen grain down from the style and into the ovary of the ovule. The sperm than travels down the pollen tube and fertilizes the egg. This zygote than develops into the plant embryo. Parts of the ovule become the seeds coat and stored food. the ovary and other flower parts will develop into a fruit and surround the seed.

angiosperm lifeIt is important to note that pollination can occur in many ways. The three most common are through:

poll 1

poll 2

poll 3

Advantages vs. Disadvantages

 Similar to asexual reproduction, sexual reproduction poses pros and cons as well. The benefits of reproducing sexually include the fact that you have a high genetic variability among species of plant. This poses great excellence of biodiversity within our ecosystem. Because of the high biodiversity, plants are not competing for the same food source because they are all different. To add, seeds can also remain dormant for a long period of time before they start to bud. This proves high sustainability among species of plants. The drawback to sexual reproduction pertain to the fact that these plants require more plant structure, and because of that, also require more energy to sustain life and reproduce.

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