Difference between Heterocrony and Paedomorphisism ● paedomorphasis is one type of heterochrony ○ = juvenille of the ancestor looks like the adult of descendant ○ Ex: salamanders that stay in the water as adults=they can keep the gills of juvenile form and stay in the water ○ Ex: human evolution; dog breeds in lab ○ ex: Dog Lab­truncated development so various breeds of dogs looked like juveniles of wolf ○ ex: pedomorphic foxes that came from the breeding of them for tameness ● paramorphasis ○ = adult of ancestor looks like juvenille of descendant ○ Ex: Irish elk = a simple extension of the growth of the antlers ■ an extension of the development of the juvenile Mosaic Evolution: ● = “different rates for different traits” ● Some parts of the body develop at different rates or at different times than others­­different morphological features change at different times in Jablonski’s words ● EX: birds; these early birds­had feathers and wish bone also had teeth in skull and well­developed claws in forelimbs like ancestral dinosaurs ● Tetrapods ­ had flattened tail to swim in water but at the same time had limbs for land ● Humans: upright posture came before the enlargement of the brain ● Mammals; whales­whale­like ears and aspects of skull but vertebral column; still had hindlimbs ● organisms tend to be modular­­­so head can evolve separately from limbs, body, aspects of behavior Amniotic Egg: ● Huge leap in terms of animals the reproduce that way. ● Breakthrough that allowed the creatures to reproduce without being bound to the water ● Multiple layers of tissue that allowed gas to pass through the membrane without the egg drying out ○ This meant eggs could be laid on the ground without the risk of the newly fertilized egg dehydrating ● With dependency on water they couldn’t really fully transition to living on land ● Once they could live on land and reproduce there they were able to go more onto land and truly diversify there to fill niches Natural selection will be on the final (from the first part of the course): ● The major themes from the first part of the course will be the most important, not specific details ● Heritable,

● opportunistic nature of evolution ­ the contingency of having right mutation at the right time, based upon an environment allowing for the development of new niches Selfish Gene Theory ● idea that there are certain genetic sequences that allow them to multiply within the genome ○ Not to benefit of bodies that carry them, s.t. they are reproduced whenever the cell divides ● molecular parasite (transposons like we talked about earlier in the quarter)=some of the sheer volume of the genome is the parasite ● why this doesn't take over the entire genome: ○ Natural Selection acts at the level of the body and it would be disadvantageous to have too too much of the transposons! ○ Domesticated selfish dna=has been caught by body’s defensive mechanisms and stabilized ○ When they sometimes break loose and insert randomly into dna they are like mutation and can cause diseases or change how the dna functions ○ People are trying to use this mechanism to try and get rid of genetic diseases in humans Cambrian Explosion and its Mechanisms: ● when virtually every major body plan originates, and is visible in the fossil record ● Why did it happen? ○ there was not enough oxygen prior to this era for body parts to develop, which means with more oxygen a threshold was passed ○ Loose niches vs.loose genes hypothesis ■ loose niches: ● promoted by ecological opportunity ● organisms were exposed to so many ecological niches that diversification was promoted ● all the open opportunities promoted great diversification ● as niches filled up when organisms developed, there was not a lot of open areas to fill up and conquer ■ loose genes: ● the genes that told what to develop when were more simple back then, so there was more of an opportunity and less of a side effect to develop fancy designs ● when genes became more interactive between themselves, a web was created, and it bogged the wild advancement of developments and mutations. they became more slow ○ ex ­ kidneys have tooth genes and teeth have tooth genes.

○ → so once there was an increasing level of buffering such that there was less of an effect for mutations to go ary, great new evolutionary advancements occurred much less… Bush­like vs. Ladder­like Evolution ● people think of evolution as linear progressions from one form to next; but actually series of diversifications­­bush rather than ladder ● (thought to be a ladder­­same for horses; but really once developed determined that evolution is actually bush like) Humans: ape→ primitive mammal→ therapsid→ icthyopsaur(sp??)→ fish ● → main point is that although we think of intermediate steps being a path, there is in actuality a series of diversification at each level → which means there is a bush at each end to the tree. not just a simple development as time went on ­ but at each stage there were branches of development Mass extinctions ● really shake things up ● most extinctions occur on a very small level ○ very short events, probably 95% of extinction happens during background times (analogous to background radiation) ● the mass extinctions change the rules. alot of the factors that matter during normal times, play no role during mass extinctions at all. ○ like body size, and amount of population do not matter ○ instead, the effective geographic range of lineage matters! ■ → the more widespread you are, the lower your extinction rate is ● because this means there is a higher chance that somewhere the genetic lineage is might happen to be where the extinction affects an area less ■ “Dead Clade Walking” ● = a species that surrives a mass extinction does not come out of the ruins and flourish, taling over new niches and ecological opportunities from their opening, but instead lingers on for millennia w/o becoming a diversified and commonplace species ­ a mere old vestige of a pre­extinction species ○ ex = the nautilius ○ shows us that this new post­extinction environment is not paradise ­ it is not easy to flourish and takeover new niches ● = winning the extinction but losing the recovery