BIOA01H3 Lecture Notes - Lecture 12: Sympatric Speciation, Asexual Reproduction, Nondisjunction
BIOA01
LEC 12: Speciation and Variation
SEPT 29, 2015
1. Genetic Isolation (no gene flow)
→ 1.1: Allopatric Speciation (most common)
• Physical barrier divides a pop.
• A. Vicariance
- example: formation of Isthmus of Panama = vicariance event for
MARINE animals
- closely related animals found on Pacific and Caribbean side
- pairs of species on either side of land bridge
• B. Dispersal
- dispersal among islands can lead to REPEATED divergence
- Ex: Kingfishers on mainland New Guinea (varies on nearby
islands→ closely related but diff. subspecies
- Species cluster: closely related species or subspecies descended
from a RECENT ancestor
- Ex: Caribbean Anolis Lizards
→ Sympatric speciation
• Subgroups form within a pop. In the same geographic region
• Specialization in subgroups reduce gene flow
A. Host races
- different variants favour distinct hosts
- Ex: Hawthorn fruit (more nutritional for maggots but more likely
to be parasitized) and apples (less nutritional but less likely to be
parasitized) → equally good for them
B. polyploidy
more than 2 pairs of homologous chromosomes
- ancestral state for eukaryotic organimss is two copies of chromo
(diploid)
- gametes have one set of chromo. (haploid)
- two routes→ autoplyploidy & allopolyploidy
autopolyploidy → adults give rise to gametes; in some there is a mutation that
causes non-disjunction ; create triploid offspring that cannot produce gametes →
meiosis does not continue
- ***if gamete self-fertilizes, the produces two 4 offspring allows
meiosis to continue
- if organisms can self-fertilize and asexually reproduce, fertile
offspring is the result
allopolyploidy
- species 1 and species 2 are able to produce gametes
- the gametes hybrdidize a zygote
- then produce offspring that may be viable but might be sterile
find more resources at oneclass.com
find more resources at oneclass.com
3363410481 and 37710 others unlocked
18
BIOA01H3 Full Course Notes
Verified Note
18 documents
Document Summary
Sept 29, 2015: genetic isolation (no gene flow) 1. 1: allopatric speciation (most common: physical barrier divides a pop, a. vicariance. Example: formation of isthmus of panama = vicariance event for. Marine animals closely related animals found on pacific and caribbean side. Pairs of species on either side of land bridge: b. dispersal. Dispersal among islands can lead to repeated divergence. Ex: kingfishers on mainland new guinea (varies on nearby islands closely related but diff. subspecies. Species cluster: closely related species or subspecies descended from a recent ancestor. Sympatric speciation: subgroups form within a pop. In the same geographic region: specialization in subgroups reduce gene flow, host races. Ex: hawthorn fruit (more nutritional for maggots but more likely to be parasitized) and apples (less nutritional but less likely to be parasitized) equally good for them: polyploidy more than 2 pairs of homologous chromosomes. Ancestral state for eukaryotic organimss is two copies of chromo (diploid)