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Haploids vs Diploids
Haploids have one of each chromosome, diploids have 2 of each chromosome
Asexual reproduction
offspring are clones of parents, no change in chromosome number
Why might organisms not do sexual reproduction?
its inefficient, costly, and risky for survival
Facultative sexual
Sometimes asexual, sometimes sexual
“The Tangled Bank Hypothesis” by G.Bell
Sexual reproduction is advantageous in complex environments with limited resources (differentiation increases survival rate)
“The Red Queen Hypothesis” L. Van Valen
Sex provides varied offspring allowing for rapid evolution
Conflict between the sexes
small male investment, large female investment, males compete, females choose, different traits between sexes
Sexual Selection
Differential success among individuals in acquiring mates (male competition and female choice)
Sexual dimorphism
Darwin- males and females differ through physical traits and aggressiveness
Intrasexual selection
Favors the evolution of mechanisms that enhance ability to compete with other members of one’s own sex
Female choice hypothesis - Why do females prefer a particular male trait?
Direct benefits, good genes, sexy sons/ runaway selection
Biological species concept (BSC)
all member have the potential to interbreed under natural conditions and produce viable, fertile offspring
Problems with BSC
subspecies, hybrids, doesn’t apply for asexual organisms, ring species
Prezygotic barriers
Separates species by preventing the formation of a zygote or fertilized egg(habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation)
Post-zygotic barriers
Separates species by preventing development of viable or fertile offspring (reduced hybrid viability, hybrid infertility, hybrid breakdown)
Allopatric Speciation
a mechanism of speciation, a physical barrier that divides the population
Sympatric Speciation
a mechanism of speciation, no physical barrier, but changes in behavioral traits
Autopolyploidy
duplication of chromosome number reproductively isolates offspring from parent population
Allopolyploidy
Hybridization and errors in meiosis lead to polyploid offspring with chromosomes from 2 different species (odd number)
Phylogeny/cladogram
a tree depicting different species and their ancestors, often showing shared traits
Phylogeny sister groups
two groups more closely related to each other than anything else on the tree
Phylogeny monophyletic group
includes a common ancestor and all of its descendants
Phylogeny paraphyletic group
includes a common ancestor and some but not all of its descendants
Phylogeny polyphyletic group
does not include the common ancestor
know how to build a phylogeny
:)
Phylogeny Synapomorphies
shared derived characteristics that are new and arose from a common ancestor
