Asexual vs Sexual Reproduction Notes

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Characteristics to Compare|  
Items to be Compared (# 3 Description)|  
 
Similarities and/or Differences|
| Asexual Reproduction | Sexual Reproduction | |
 
Process Description | Mitotic division, requiring only one parent.  Offspring are identical replicas of parent.  Cell divides after DNA is replicated. No gametes are formed, can also occur by fragmentation (a piece of the organism breaking off)| Meiotic division.  2 parents are required.  Each parent contributes ½ of the genetic material for the offspring.  Each gamete is haploid.  Gametes fertilize to make a diploid offspring.| Both are methods of reproduction, in asexual one parent is needed and offspring are identical in sexual 2 parents are needed and offspring are genetically unique|  

Disadvantages |  
All offspring are genetic replicas, there is no genetic variation except from mutation, does not allow organisms to adapt to changing environment|   2 parents are required, process is longer the population cannot grow as quickly|   No similarities, differences as listed in descriptions|

 
Advantages |  
Only one parent is needed, usually can increase number of organisms quickly, this can allow the population an advantage under desirable environmental conditions|   Offspring are all different, organisms are able to adapt and evolve to a changing environment, sexual reproduction is advantageous in a less desirable environment|   No similarities, differences as listed in descriptions|

 
Genetic Variation |  
Little or none, mutations are the only source of variation, otherwise offspring are identical |   Highly diverse, offspring are a genetic recombination of 2 parents, there is also opportunity for many mutations in meiosis|   Mutation is a source of variation in both, asexual offspring are otherwise identical to parent, sexual offspring are genetic recombinations of parents.|  

Similarities of Mitosis and Meiosis
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Mitosis and meiosis have some common features:
* cell chromosomal DNA is doubled from 2n to 4n to form tetraploid DNA just prior to division. * chromosome stages of prophase, metaphase, anaphase and telophase occur. * cytokinesis yields two new cells after one division in each process. * chemical signals initiate mitosis and meiosis in each cell's nucleus. Differences Between Mitosis and Meiosis

The processes of mitosis and meiosis, despite similarities, differ: Read on 
* Meiosis in Plants and Animals – Basic Facts
* Chromosomes & Sister Chromatids
* Mitosis & Meiosis Comparison
* mitosis occurs in many different tissues of animals; in plants, the meristems and the cambium are mitotic tissues. * meiosis occurs only in specialized tissues - the ovaries and testes in animals, and the anthers and ovaries in flowering plants. * mitosis has only 1 sequence of chromosome division and cytokinesis. * meiosis has 2 complete rounds of chromosome divisions, and two cytokinesis events. * mitosis yields 2 cells with diploid (2n) chromosomes numbers. * meiosis yields specialized, reproductive cells (gametes) with haploid (n) chromosome numbers. The sole purpose of these haploid gametes is to fuse with another appropriate gamete (e.g sperm with an egg or ovule) to produce a new, viable diploid (2n) cell (zygote). * mitosis, in either plants or animals, maintains genetic uniformity of the two new cells. * meoisis produces recombinant DNA and genetic diversity as a result of two important processes: 1. crossing-over between paternal and maternal homologous, sister chromatids, and 2. independent assortment of paternal and maternal chromosomes that produces multiple combinations of paternal and maternal chromosomes within the gametes.

Meiosis vs Mitosis
| Meiosis| Mitosis| Hide AllShow All|
Occurrence of Crossing Over:| Yes| No| hide|
Occurs in:| Humans, animals,...
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