The Evidence-
On
Page 285, Shenk talks about the enormous impact the sounds a mother hears has
on their baby and the baby’s development later in life. It is no doubt that the mother has
numerous other impacts on the baby’s development outside of just sounds. Consider species with external
development. Are individuals that
develop externally at a disadvantage because they do not have their mother to
experience different sensations through? Or is it actually an advantage because
they can experience things during development first hand, instead of through
their mother? Consider animals,
such as kangaroos, that are born early, but continue development inside their
mother’s pouch. Does that make a
difference? Relate your answer to
Chapter 47 in Campbell.
Brad Tiller
By the way the question is worded, internal development is an advantage over external development; developing organism can be exposed to the environment via their mother, and GxE interactions allow an organism to adapt to its environment before birth. An externally developing organism would still be exposed and be able to adapt to its environment, but its increased exposure to dangers in the environment would negatively impact its chance at survival. For example, developing humans are exposed to their mother's immunity to pathogens. An externally developing species has no such immunity, and therefore has a decreased chance at survival.
ReplyDeleteInternal development is more prevalent in a Type I species, while external development is more prevalent in a Type III species. With a Type I species, usually both parent organisms play an influential role in the survival of their young offspring, which reflects the connection between the mother and child established in part from the shared environmental factors during internal development. Type I species produce few offspring per mating season, and have a higher infant survival rate. On the other hand, in a Type III species, the parent organisms often have little or no effect on the child organisms, reflecting a lesser focus on shared environmental factors. Furthermore, there is a higher amount of offspring per mating season and a lower infant survival rate.
Specifically regarding a kangaroo, in the pouch, an infant kangaroo is more exposed to its mothers environmental factors. This is advantageous, as kangaroos live in harsh desert biomes which require a greater deal of acclimation to the environment
[Edit:
DeleteSource used: http://www.koalaexpress.com.au/kangaroo%20facts.htm
Brandon Axe
brandona0701@aol.com]
This comment has been removed by the author.
ReplyDeleteI agree with Brandon with regards to the way the prompt is worded; internal development seems to be a much more advantageous method than external development in its context. Also, like Brandon stated, the GxE theory would allow a baby born from internal development to adapt to their environment prior to birth, contrary to external development, which would require a developing child to adapt on its own.
ReplyDeleteShenk discusses the formation of the ear and its functionality on page 286, and emphasizes the significance of hearing as a sense. “The ear first appears in the 3rd week of gestation and it becomes functional by the 16th week” (286). This is significant because during the morphogenesis in animals, the development of hearing is rapid and is “probably the most developed of all senses before birth” (286). While this hearing is extremely important as Shenk discussed thoroughly, there are many other traits that can be attributed towards experiencing something from the mother, both positive and negative.
In terms of an example for the factors on a baby’s development internally in humans, illicit drug use and alcohol drinking can affect children still in the womb negatively in many ways. Even though the actual identification of effects of drugs and alcohol were extremely difficult to pinpoint, “nationwide, between 550,000 and 750,000 children are born each year after prenatal exposure to drugs or alcohol”, and the effects were seen consistently (http://www.childwelfare.gov/pubs/usermanuals/substanceuse/chapterthree.cfm). Most commonly, the children are born with growth deficiencies (prenatal and post-birth), issues with the central nervous system, inhibited development of the optic nerve, joints, limbs, ears, and heart. With the presented information, it seems to be that internal development could actually be a disadvantage for children in the wombs of mothers that drink or use drugs during pregnancy. In this case, external development would have been an advantage, however humans cannot develop externally.
Internal development could actually be a significant advantage when it comes to placental aid versus marsupials that are born immaturely and then crawl into the mother’s pouch to then receive elements essential to survival. The ability of placental development is efficient because the fetus does not have to adjust position. The placenta “protects the fetus from the immune system of the mother, which would otherwise react against the fetus because half of its genes are from the father” and would then be producing foreign proteins (http://www.livestrong.com/article/128647-process-reproduction-humans/). A key advantage of the internal development for the entire duration of pregnancy is that the fetus is protected within the mother for it’s entire development.
Edit: Shivani Thakker (shivanithakker1357@gmail.com)
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