Developmental Psychology

Achieve Test Prep: Developmental Psychology

that monozygotic twins are more similar than dizygotic twins. The easiest method of studying differences in twins is by studying twins who were separated at birth. Additionally, studying adopted children and comparing their traits to those of their adoptive parents can indicate whether a particular trait is genetically or environmentally- based: nature versus nurture. Natural selection has an influence on which genes are expressed at a given time. Natural selection states that organisms which are best adapted to their environment will be most likely to survive, thus passing on their genes to the next generation. Charles Darwin originally postulated the theory of natural selection. Darwin’s study of the Galapagos finches is an excellent example used to better understand natural selection. Within the Galapagos Islands, Darwin noticed there were different finches particular to individual islands. Each type of finch was slightly different; some had long beaks, while others had shorter beaks. After examination, Darwin discovered the beak size and shape corresponded directly to the food available on the different islands. Each type of finch, though stemming from a common ancestor, has developed into a new species which allowed them to survive and reproduce. Genetic and Chromosomal Abnormalities: Many abnormalities have negative repercussions for organisms, and humans are no different. Having too many or too few chromosomes can lead to a variety of syndromes (a cluster of symptoms which occur together). There are numerous genetic diseases and here are a few of the more well-known ones: • Down syndrome: Also known as Trisomy 21 . A child with Down syndrome has three copies of chromosome 21, instead of the normal two copies. Most individuals live well into adulthood with this common abnormality. Individuals with Down syndrome have distinct facial features, such as a round face, thick tongue, and slanted eyes. Most individuals have slow development in many areas and a degree of mental retardation. The degree of mental retardation varies widely, as some individuals live on their own, while other require lifelong care. There are a plethora of accompanying diseases and medical issues with Down syndrome. • Phenylketonuria: PKU is an abnormal digestion of the amino acid phenylalanine.

Phenylalanine is a necessary amino acid and is found in many foods. PKU is recessive, meaning parents could be carriers and unaware of the gene. Dietary restriction of phenylalanine can reduce symptoms.

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