All living things must reproduce in order to grow their populations. In order to accomplish that goal, evolution has provided 2 competing methods: sexual and asexual reproduction. Each method produces offspring, but has its own benefits and drawbacks. Let’s take a closer look at sexual vs. asexual reproduction.
Most of the species that we’re usually in contact with reproduce sexually. This includes everything from humans to fish to flowering plants! Sexual reproduction requires two parents who produce special cells called gametes which combine to form a genetically unique offspring.
In sexual reproduction, an offspring will only receive half of each of its parent’s DNA. This mixing and matching of genetics produces lots of variations in a population. As DNA is mixed and matched over several generations, new traits pop up that may not have been present before.
This variety is considered the primary advantage of sexual reproduction. Because all the individuals in a sexually reproducing population are slightly different from one another, there is a higher chance that some portion of the population will have a genetic resistance to challenges that may arise as environmental conditions inevitably shift. This process of slightly changing over time makes sexual reproduction the primary driving force of evolution.
The drawbacks of sexual reproduction mostly center around the amount of energy it requires. Gametes, produced by the process of meiosis, take time and energy to make. On top of that, it also requires energy to find and select a suitable partner for mating. One has only to think of the plight of the salmon to be convinced that sexual reproduction is often quite the task!
Asexual reproduction, involving much less energy, is a form of cloning. A parent will produce offspring which shares an identical set of DNA. This can happen in a variety of ways:
Types of Asexual Reproduction
|Budding||Some species, like the hydra, are capable of growing an appendage that eventually breaks off and becomes an offspring. This process is called budding.|
|Binary Fission||Most cells reproduce asexually. In eukaryotes that process is called mitosis, in prokaryotes it’s known as binary fission.|
|Runners||Several plants, including strawberries, are able to reproduce asexually by growing a root that shoots away from the parent plant. Eventually this root will sprout a genetically identical clone.|
Regardless of the way it’s accomplished, asexual reproduction always produces genetically identical offspring. This can be a bad thing when it comes to changes in the environment. When one individual is susceptible to a danger, so is the entire population. For better or for worse, asexual reproduction produces an army of clones. This lack of genetic variety makes an asexually reproducing population vulnerable to changing conditions.
Asexual reproduction, however, is strong where sexual reproduction is weak. It requires very little energy and can happen very quickly. These benefits make asexual reproduction an excellent reproductive strategy for any species interested in building a very large population quickly. Bacteria are one such example. Their colonies can grow to millions of individuals in just a few hours.
Sexual vs. Asexual Reproduction Resources
2 pages of pre-reading covering sexual vs. asexual reproduction prepares students for a summarizing review. This resource also includes a graphing extension which can be used for differentiation or extension.
15 multiple choice questions requiring students to differentiate between instances of sexual vs. asexual reproduction.
Who doesn’t love a good sub plan? Let students explore reproductive strategies on their own using this interactive webquest. An extension activity requires students to argue which strategy they would choose in an organism of their own design.
Additional Sexual vs. Asexual Reproduction Resources
- PDF File containing many descriptions of various organisms and their reproductive strategies from the University of Utah
- Lab involving population growth of both sexually and asexually reproducing species
- Textbook style pages describing in detail the two methods of reproduction. Includes a watermark, but could still be useful for reference
- Web Interactive containing descriptions of reproductive strategies of several species
- Youtube Video with a short, student friendly description of both strategies
- Presentation 2
- Worksheet 2
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