Chapter 27 Reproduction and Embryonic Development

I. Asexual and Sexual Reproduction

1. Asexual reproduction results in the generation of genetically identical offspring, such as budding and fission.

2. Asexual reproduction can also result from the two-step process of fragmentation, the breaking of the parent body into several pieces, followed by regeneration, the regrowth of lost body parts, such as starfish.

3. Sexual reproduction results in the generation of genetically unique offspring.

(1)  Sexual reproduction is the creation of offspring through the process of fertilization, the fusion of two haploid (n) gametes (sperm and egg) to form a diploid (2n) zygote (fertilized egg). n is the number of chromosomes in a gamete and refers to the haploid number of chromosomes; for humans, n = 23 and 2n = 46.

(2)  Sexual reproduction increases genetic variability among offspring.

4. Hermaphroditism is a condition in which an individual has both female and male gonads to produce both sperms and eggs.

5. External fertilization is the fusion of gametes that parents have discharged into the environment, such as many aquatic invertebrates, most fishes and amphibians.

6. Internal fertilization is the reproduction in which sperms are deposited in or near the female reproductive tract, and fertilization occurs within the tract.