BIOL1003 Lecture Notes - Lecture 3: Explanatory Power, Polyploid, Reproductive Isolation
BIOL1003: Module 1 - Evolution
Lecture 3 - Species
Lecture 2 Overview:
• Microevolution is currently occurring and is observable
• Macroevolution is currently occurring and is observable
• Speciation by polyploidy has been observed an d evidence indicates it is common in plants
• Speciation by polyploidy can be induced artificially
What is a species
• Everyone has a different answer, which changes how many species we can say we have
• Approx. 2 million different species exist (as a fair guess)
• Fungi are closer to animals than plants are
• Confusion on what a species actually is
• There is a discontinuity of form
o All things within that group have something in common, but the next group has a
significant gap
o Example: apes and humans are very closely related (98%), but there is a discontinuity
between them, making them starkly different, although also relatively similar
• Differences in chromosomal numbers usually means significant differences
o Underlying differences
o Taxonomists were able to identify morphological differences
• Typological species concept (TSC)
o Aristotle to Linnaeus
o Original species concept
o "species" Latin specere, to look at
o Species are:
• Particular kinds within genera
• Eternal and unchanging
• Not by accidental properties (variation)
• SPECIES ARE THINGS THAT LOOK DIFFERENT FROM ONE ANOTHER
• Easily understood and expounded
o Limited:
• behaviour, genes, etc.
• No explanatory power
▪ How species originate
▪ How or ehy they are related to any other species
▪ How they became distinct
▪ How it remains distinct
• Subjective
▪ How different is actually different?
▪ People change their mind and publish an article grouping previously
different species, then ungrouping them again
▪ Mean species is something different
• Biological species concept (BSC)
o Mayr
o If they can interbreed, they are the same species
o This is generally accepted by biologists in principle
o Explanatory power
• Why species are similar - through sexual reproduction
• Why members differ between species - reproductive isolation
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