Overview
This lecture compares asexual and sexual reproduction, highlighting their processes, examples, genetic outcomes, and evolutionary advantages.
Asexual Reproduction
- Asexual reproduction requires only one organism and produces genetically identical offspring (clones).
- Spider plants reproduce asexually by creating plantlets that are clones of the parent plant.
- Bacteria (prokaryotes) undergo asexual reproduction via binary fission, splitting into two identical cells.
- Some single-celled eukaryotes, like protists, also reproduce asexually.
- Budding is another form of asexual reproduction; hydras can form buds that grow into new, identical organisms.
- Asexual reproduction is usually fast and efficient but results in no genetic variety.
Sexual Reproduction
- Sexual reproduction involves the fusion of gametes (reproductive cells), typically sperm and egg.
- Gametes have half the number of chromosomes of somatic (body) cells (in humans: 23 each; zygote = 46).
- The fertilized egg, called a zygote, divides and develops into a new organism.
- Offspring from sexual reproduction inherit genetic material from two different parents, resulting in genetic diversity.
- Gametes themselves are unique due to independent assortment and crossing over during meiosis.
- Sexual reproduction is more complex and time-consuming because it requires two gametes to unite.
Advantages of Genetic Variation
- Sexual reproduction creates genetic variation, allowing different traits to emerge among offspring.
- Genetic diversity can provide advantages in changing environments, such as improved survival for certain traits.
- Example: Grasshoppers with better camouflage can survive better in changing environments due to genetic variation.
Key Terms & Definitions
- Asexual Reproduction — reproduction involving one organism, producing genetically identical offspring.
- Binary Fission — asexual division in prokaryotes, forming two identical cells.
- Budding — asexual process where a new organism grows from the body of the parent.
- Gamete — reproductive cell (sperm or egg) with half the normal number of chromosomes.
- Zygote — fertilized egg cell formed by the fusion of two gametes.
- Meiosis — cell division process that produces unique gametes with half the chromosome number.
- Genetic Variation — differences in genetic makeup among individuals of a species.
Action Items / Next Steps
- Review meiosis and how it produces genetic variation.
- Consider advantages and disadvantages of both reproductive strategies for different organisms.