BIOL 1020U Lecture Notes - Lecture 22: Speciation, Chromosome, Elephas
Species and Speciation Lecture (Part 1)
Textbook Reference: Chapter 22 in Biology How Life Works (2nd ed.)
Sections 22.1 – 22.2; pp.446 to 450
What is a species?
Fundamental evolutionary unit
Why can it be difficult to define species?
Must by definition be fluid and capable of changing, giving rise through evolution to
new species
What is the “species problem”
Many definitions
Species Plot
•What is a species plot for and what
does it show?
To test whether or not species are real, we
examine the natural world, measure some
characteristics of different living things we
see, and then plot these measurements on
a graph – is the species something that is
naturally occurring?
Length of antennae measured to see if
they were different species of the same
naturally occurring animal
Is what is seen in a species plot
supported by molecular data?
Genomes of different organisms also cluster
Species are real biological entities
Distinguishing Species
•How do you distinguish one species from another?
Two criteria for determining if two individuals are members of the same species:
1.They can exchange genetic material
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2.Produce fertile offspring
Different Definitions of Species:
•Morphospecies Concept:
Often use this “rule of thumb” – says that members of the same species usually look
alike
•Advantages:
•Quick and easy
•Limitations:
•This concept is easy to apply but is not perfect
•Members of same species that look very different (peacocks and
cardinals) and members of different species that look alike
•Sexual dimorphism
•Three species of butterflies appear to look the same, but have observable
chromosome differences, making the different species
•Examples:
oPeacock and peahen (same species)
oFemale and make cardinal (same species)
•Biological Species Concept (BSC)
oDefinition:
Species are groups of actually or potentially interbreeding populations that
are reproductively isolated from other such groups
oImportant parts of this concept:
-Reproductive compatibility/reproductive isolation
-Fertile offspring produced
oWhat is meant by actually or potentially interbreeding population?
Example:
Indian elephants and Sri Lankan elephants – even though they are
separated, they still have potential to interbreed – elephas maximus
Geographically isolated but same species
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Document Summary
Textbook reference: chapter 22 in biology how life works (2nd ed. ) Sections 22. 1 22. 2; pp. 446 to 450. Must by definition be fluid and capable of changing, giving rise through evolution to new species. Length of antennae measured to see if they were different species of the same naturally occurring animal. Two criteria for determining if two individuals are members of the same species: Often use this rule of thumb says that members of the same species usually look alike. Species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups: important parts of this concept: Indian elephants and sri lankan elephants even though they are separated, they still have potential to interbreed elephas maximus. Difficult to apply in real world situations. Must test if two species can mate and produce fertile offspring many limitations. Does not apply to asexual organisms (bacteria), extinct species (fossils) Does not account for genetic exchange in ring species.
