REPRODUCTION
The survival of a species, a group that produces fertile offspring from interbreeding, completely depends on its reproductive success. It is the production of offspring through asexual or sexual processes. Asexual reproduction is the process of making clones of an organism through only one parent. Sexual reproduction creates genetically variable offspring through two parents, one male and one female. Many plants and "unicellular" organisms use asexual reproduction for creating offspring, while many mammals and amphibians such as fish, use sexual reproduction. [1] However, it has been seen that sexual reproduction is preferable because asexual reproduction "compromises their ability to adapt to the environment because they do not benefit from the genetic variation introduced by sexual reproduction." [1] Asexual reproduction also takes place in many forms including binary fission, cell division in prokaryotes; budding, offspring growing off of a parent; fragmentation (regeneration), a piece of an organic forming a new organism; and vegetative propagation.
MITOSIS VS. MEIOSIS Meiosis and mitosis are two cell dividing processes. Meiosis is more applicable to reproduction, while mitosis is more applicable to cell reproduction, growth, and repairing the body (requires fertilization). Meiosis creates sex cells, also known as gametes, and mitosis creates skin cells. At the end of these processes, mitosis leaves a full set of chromosomes, known as diploid cells (there are two), and meiosis leaves a half set of chromosomes, also known as haploid cells (there are four). Like asexual and sexual reproduction, mitosis involves a cell that creates two identical cells while meiosis is "involving two fissions of the nucleus and giving rise to four gametes, or sex cells, each possessing half the number of chromosomes of the original cell." [2] Mitosis happens in every organism, while meiosis only occurs in humans, animals, plants and fungi. Crossing over can only occur in meiosis, not in mitosis. These processes occur in a similar manner. Mitosis goes through interphase, prophase, metaphase, anaphase, then telophase and meiosis goes through two rounds of that, with interphase, prophase I, metaphase I, anaphase I, telophase I, then prophase II, metaphase II, anaphase II, and telophase II. These processes involve a non-dividing phase (interphase, occurring 90% of the time). The next steps take up 10% of the time which involves chromosomes appearing, spindle fibers forming (created by centrioles), and nuclei disappearing (prophase), chromosomes lining up in the center (metaphase), sister chromatids moving apart (anaphase), and finally two cells forming from the division of one cell (telophase). These two processes are extremely essential to survival, growth, and reproduction processes. |
Green Darner Reproduction
In dragonflies, reproduction has a large process. Dragonflies use sexual reproduction to produce offspring. The male normally grabs the female's head with his cerci, an addition at the end of the abdomen. Mating will normally take place on vegetation. Males "have a separation of the genital opening and the copulatory organ." [3] This means that they have a specific sexual organ along with genitals. Similar to humans, the male transfers sperm before connection with a female to their seminal vesicle under one of their many abdominal segments. This sperm comes from the genital opening also located in a different segment of the abdominal. Sperm is transferred to the female once the organisms are linked, and the female puts the tip of her abdomen on the seminal vesicle (of the male) in order to obtain sperm. While the dragonflies are mating, the male will cleanse the female of any leftover sperm from past mating. Green darners are seen as polygynandrous, which is where males and females have many mating partners that they have mated with many times. Females are often marked from the male aggression of grabbing the females' heads. After the mating process, green darners lay their eggs still in male and female pairs. Egg clutches can come in many different amounts depending on the size of the dragonfly. Oxygen deficiency normally causes the eggs to hatch. When they are born, the green darners are born as nymphs that live in lakes and ponds for the first stage of their lives before going through metamorphosis and going into adulthood. [3]