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Lecture 19

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Biology 1001A

Lecture 19 Species and Speciation  Macroevolution: involving large number of lineages, between different lineages  Microevolution: changes between one lineage  Speciation gave rise to the diversity of life  Last class:  Parent-offspring conflict before birth  o starts at conception, at formation of zygote o Fetus selected to "demand" more resources from mother than mother selected to give o  fetal tissue in placenta secretes allocrine hormones to manipulate maternal blood pressure and blood sugar; maternal sensitivity to these signals drops  a tug of war between the mother and the fetus, it is dangerous, if mother wins, and fetus will not get enough sugar, then fetus will under develop  conflict of interest endangers both parties (gestational diabetes, pre-eclampsia) o coefficient of relatedness to self is 1 o coefficient of relatedness to mom, dad and siblings are 0.5  Unrelated individuals may have similar, but not overlapping, interests  o tragedy of the commons: social dilemma (conflict) over use of shared resource o  10 farmers each own their own cows, but all share "the commons"  as more cows are added, cost of overgrazing shared by all the farmers  Benefits of owning another cow are not shared  in the individual farmer's own benefit  rational decisions by individuals -> overexploitation of shared resource  Summary: Cooperation and Conflict  o Altruism, like sex, is puzzling o Many 'altruistic' traits can be explained by shared genetic interests; others by reciprocity; but rational decisions by individuals may deplete shared resources o Even when genetic interests overlap (family groups) they can be different enough to induce conflict  Species and Speciation:  Morphological species concept  o look at their phenotype o look more similar pending on phenotype o when there are sexual dimorphism, we cannot really tell the species between them just based on morphological species concept o  e.g. when there's strong sexual selection between male and female, thus males look very different from the females  Biological species concept  o Species: interbreeding (or potentially interbreeding) group of individuals, reproductively isolated from other such groups o grey areas o  sometimes two different species may mate between each other e.g. liger (lion with tiger) o need to look at the hybrids' reproductiveness, can it reproduce offspring, if the hybrid cannot reproduce, then the parent are two different species  Limitations to Biological species concept  o cannot be tested easily in the field o geographical isolations o dealing with animals that are extinct o reproductive isolation is meaning less to organism that use asexual reproduction  One species or two?  o there are two birds, on
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