Instant Speciation

Polyploidy is due to nondisjunction / failure of chromosomes to separate during meiosis resulting in an extra set of chromosomes in the offspring. 

This leads to instant speciation / no gene flow / new species.. 

The offspring cannot reproduce with is parent species/ can only reproduce vegetatively / asexually and so gene flow does not occur.

Hermaphrodite animals usually are polyploidy, such as flatworms, and earthworms. Polyploid humans usually abort spontaneously.

Polyploidy  

When an organism contains 3 or more times the haploid (1N) number of chromosomes.

E.g. Normal for 2N (homologous pairs), polyploidy = 3N or more)

Non-disjunction 

This is the process that leads to these mutations and how species can go from producing infertile hybrids to fertile new species.

Autopolyploidy

Form of polyploidy, results from mating between SAME SPECIES

In this condition/situation an organism receives multiple sets of chromosomes from the same genome type or the same species. 

Most often this results in an even number of chromosomes. 

Due to the similarity of the chromosomes, they undergo multivariant pairing during the process of meiosis. 

Allopolyploidy

Type of polyploidy, results from mating between TWO different SPECIES.

In this phenomenon/condition/situation a hybrid variety is formed as a result of receiving three or more sets of chromosomes from genetically nonidentical varieties/species or parents. 

Therefore, they do not have similar genomes and they belong to different types of species. 

This can result in the offspring (species C) having either an even or an odd number of chromosomes. 

Remember Polyploidy is more common in plants because plants can self-pollinate and reproduce asexually.

Polyploid plants usually have larger cells resulting in larger or resistant plants, with better characteristics than normal (diploid) plants. These are mainly useful in agriculture (bigger seeds) and horticulture (larger flowers). 

Polyploidy with uneven numbers of chromosomes are sterile, so any resulting fruit will have no seeds which is a commercial benefit (banana, seedless watermelons, seedless grapes). 

Polyploidy may have a greater advantage as they contain a range of adaptations resulting from the combination of characteristics they have got from the different species. 

Example of what you will usually have to cover in a polyploidy exam question

·      describes polyploidy as a doubling / multiple of chromosome sets

·      describes effect of polyploidy on phenotype, e.g. hybrid vigor

·      explain why species must be closely related

·      explains why hybrids are infertile

·      explains the role of meiotic error/ double chrom #/ non-disjunction/ amphiploidy in polyploidy

·      explains the role of  self fertilizations in polyploidy

·      links the changes in genotype to the changes in phenotype in modern wheat development

·      explains instant speciation or sympatric in terms of reproductive isolation

Very useful No Brian too small link for this topic: 

http://www.nobraintoosmall.co.nz/students/biology/NCEA_Level3/pdfs/bio_91605_polyploidy_notes.pdf#zoom=100