Sexual and Asexual Reproduction

There are two types of reproduction that organisms use to produce offspring; asexual reproduction and sexual reproduction. Asexual reproduction results in genetically identical offspring and only requires one parent, whereas sexual reproduction requires two parents and the offspring produced will always be genetically different from the siblings, parents, and other members of its species. There are many advantages and disadvantages to both types of reproduction. 

The advantages to asexual reproduction are: A large number of offspring is produced promptly from only one parent when conditions are preferable,and the large amount can get together to outcompete other organisms for nutrients and water. With a large number, that species may live longer when the environment and the amount of predators change. Also, no energy is needed to find a mate. Along with the advantages come disadvantages: because the offspring produced are all genetically identical, a negative mutation can make them prone to diseases which wipes out a considerable amount of offspring. In some methods, the offspring are produced quite close together causing them to fight for nutrients and space, also,  if conditions are not preferable (ex. extreme temperatures) significant amounts of offspring will perish.

In sexual reproduction there are two types of fertilization; internal and external. Internal is when sperm cells are deposited inside the females body, where they will meet an egg cell to fertilize. Most animals that live on land such as humans and mountain goats, and some animals living in water such as orcas use internal fertilization. External fertilization is when the sperm and egg cell meet outside of the bodies of the parents. This method is most often used by organisms that live in water such as salmon and sea urchins. Plants like ferns and mosses also use external fertilization.There are disadvantages and advantages to sexual reproduction involving both internal and external fertilization. The advantages to sexual reproduction are: not much energy is needed to find a mate (external fertilization),  and larger amounts of offspring can repopulate after a setback in their environment (external fertilization). A greater amount of security is given to the embryo and offspring receive more parental care(internal fertilization), and offspring are genetically different from their parent, so they have a greater chance of surviving new diseases or other hazards in their environment. The disadvantages of sexual reproduction are: a greater amount of energy is needed to find a mate (internal fertilization),  and a smaller amount of offspring is created, so if the number of predators expands a population will decrease (internal fertilization). Also, through external fertilization gametes, embryos, and offspring are exposed to predators.

Since the offspring created through sexual reproduction is genetically different from any other organism in its species, we get much more diversity compared to the result of asexual reproduction. This is where an advantage comes in for sexually reproduced organisms. Being different from others means you are less likely to inherit genetic diseases and you have a chance of surviving new diseases or other hazards in their environment.If an asexually reproduced organism gets a disease, a very large amount of the offspring will also be affected because they are genetically identical.

External Fertilization (BC Science 9 textbook) 

Internal Fertilization (BC Science 9 textbook)