BISC 102 Chapter Notes - Chapter 13, 20, 26, 27, 34: Moose, Helianthus Annuus, Helianthus Petiolaris
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19 Jan 2018
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Recommended Lab Readings - Part 6
Sec 13.6 - Identifying Human Traits as Autosomal or Sex-Linked:
- If trait is equally often in males and females = likely autosomal
- If males more likely to have the trait, allele is likely recessive and on X chromosome (x-linked)
- The appearance of an X-linked recessive trait skips a generation in a pedigree.
- Good indicator of X-linked dominant trait: Affected male has all affected daughters, no affected sons. Every
daughter gets X chromosome from affected father, sons get X from unaffected mother.
Lab - The Major Patterns of Evolution:
26.1 - How are Species Defined and Identified?
- Genetic distinctions bc mutation, selection, drift act on each species independently of what is happening in
other populations.
-Biological species concept: two diff populations do not interbreed, fail to produce viable and fertile offspring,
they are diff species
- No gene flow in reproductively isolated populations.
-Morphospecies: distinguishing features most likely to arise if populations are independent/isolated from
gene flow.
- Applicable: no data on extent of gene flow, to sexual, asexual, fossil species
-Ecological: species = organisms exploiting a single set of resources, having same range of environmental
tolerances, facing same predators and parasites
- Concept emphasizes role of natural selection
- Useful for identifying bacteria, archaea, asexual eukaryotes
-Phylogenetic: reconstructing evolutionary history of populations. Species = smallest monophyletic groups
on tree of life.
- synapomorphy = homologous trait (inherited from common ancestor), unique to certain populations/lineages
- Logical bc diff species have diff synapomorphies only if they are isolated from gene flow and evolved
independently
26.4 - What Happens When Isolated Populations Come Into Contact?
- Reinforcement: if 2 populations diverged extensively, distinct genetically, then their hyrid offspring should
have lower fitness than parents. Populations well adapted to diff habitats. Hybrid offspring not well adapted
to either.
- Selected traits reinforce differences that evolved while populations were isolated.
- Natural selection can act to reduce mating b/w species only if ranges overlap. Sympatric species exhibit
prezygotic isolation that allopatric species do not.
- Hybrid Zones: geographic area where interbreeding occurs and hybrid offspring are common.
- New Species through Hybridization: H. annuus
and H. petiolaris
were isolated and diverged as separate
species. Later interbreed ---> hybrid offspring = new species that had unique combo of allels from each
parental species. Different characteristics (H. anomalus
).
27.3 - Adaptive Radiation
- Adaptive radiation: when a single lineage produces many descendant species that live in a wide diversity of
habitats and use a wide array of resources.
- Trigger adaptive radiation: new resources and new ways to exploit them.
- Ecological opportunity: availability of new or novel types of resources
- Morphological innovation: the evolution of a key morphological trait - one that allowed descendants to live in
new areas, exploit new sources of food, or move in new ways = triggered many important diversification
events in the history of life.
- New morphological features may support rapid speciation and ecological divergence.