Heredity

• CHARLES DARWIN

  • Observed that most organisms reproduce at tremendous rates, yet populations remain nearly constant.

  • Reasoned that an intense, constant struggle for food, water, and resources must occur among the numerous young born.

  • Those that survive pass on their genes to the next generation.

  • Believed that those who survive are superior to those who do not.
• Natural selection is the evolutionary process that favors individuals of a species that are more adapted to survive and reproduce.
• FRANCIS GALTON (1822-1911)

  Intelligence is a matter of sensory acuity
• Eugenics


  Selective breeding
• Intelligence inherited


  Sensory acuity mainly a function of natural endowment
• ALPHONSE DE CANDOLLE (1806-1893)


  Climate, religious tolerance, democratic government, and a thriving economy are at least as important as inherited capacity
• MODERN TWIN STUDIES


  • The behavioral similarity of identical twins is compared with the behavioral similarity of fraternal twins
• Identical twins (monozygotic twins)


  develop from a single fertilized egg that splits into two genetically identical replicas, each of which becomes a person
• Fraternal twins (dizygotic twins)


  develop from separate eggs and separate sperm, making them genetically no more similar than ordinary siblings
• Identical twins might perceive themselves as a “set” and play together more than fraternal twins
• Measured skulls


  the favored method of Paul Broca
• W. STERN (1871-1938)


  he said that Mental age should be divided by chronological age and intelligence quotient
• BINET’S APPROACH

  • The scores are a practical device.

  • The scale is an empirical guide for identifying children who need help.

  • Emphasis upon improvement through special training.
• HENRY GODDARD (1866-1957)


  • Translated the Binet-Simon scale into English
• LEWIS TERMAN (1877-1956)


  Revised the Binet scale and made it popular. IQ = MA/CA*100.
• ROBERT M. YERKES (1876-1956)


  invented the army alpha and beta test
• Immigration Restriction Act of 1924


  Quotas against nations of "inferior stock."
• G. R. Stetson


  invented the us black-white mental testing
• Memory not a valid measure of intelligence
• Arthur Jensen: sparked a debate theorizing that intelligence is primarily inherited. Differences between “races” are inherited
• Down syndrome


  Caused by the presence of an extra chromosome
• JOHN LANGDON H. DOWN


  Physician to the Asylum for Idiots at Earlswood.

  • 1860s: Investigations into the 'structure and function of the various organs' in idiots and imbeciles.

  • Classify idiots on the basis of their resemblance to ethnic groups.

  • Facial features and behavioral attributes of certain idiots -> typical Mongols
• Both genes and environment are necessary for a person to exist
• The emerging view is that genes give people a propensity for a particular developmental trajectory that is ultimately realized through environmental circumstances
• PRENATAL DEVELOPMENT


  From a zygote, a single cell, the size of a period in your book, to 2 billion cells and weighing over 3kgs.
• Reproduction begins when an ovum is fertilized by a sperm.

  • This produces a zygote—a single cell formed through fertilization.

  • In the zygote, two sets of unpaired chromosomes combine to form one set of paired chromosomes
• GERMINAL PERIOD


  It is the period that occurs the first 2 weeks after conception
• THE DIFFERENTIATION OF CELLS

  • The Blastocyst - the inner layer of cells that develops during the germinal period and later becomes the embryo

  • The Trophoblast - the outer layer of cells that develops during the germinal period and later provides nutrition and support for the embryo
• EMBRYONIC PERIOD


  The period that occurs from 2 to 8 weeks after conception

  • The rate of cell differentiation intensifies, support systems for the cells form, and organs appear
• Endoderm - inner layer; develops into the digestive and respiratory systems
• Ectoderm - outermost layer; becomes the nervous system, sensory receptors (ears, nose, eyes), and skin parts (hair and nails)
• Mesoderm - middle layer; becomes the circulatory system, bones, muscles, excretory system, and reproductive system
• The Placenta - consists of a disk-shaped group of tissues in which small blood vessels from the mother and the offspring intertwine but do not join
• The Umbilical Cord - contains two arteries and one vein, that connects the baby to the placenta
• The Amnion - a bag or envelope that contains a clear fluid in which the developing embryo floats
• IMPORTANT EMBRYONIC DEVELOPMENTS

  • 21 Days - Eyes begin to appear

  • 24 Days - Heart cells begin to differentiate

  • Fourth Week - First appearance of the urogenital system, arm and leg buds appear, chambers of the heart take shape, blood vessels surface

  • Fifth to Eighth Week - Arms and legs differentiate further, face starts to form, facial structures

  • 8 Weeks - 2.5 cm long
• ORGANOGENESIS


  The process of organ formation that takes place during the first 2 months of prenatal development
• FETAL PERIOD


  The period that begins 2 months after conception and lasts, on average, 7 months
• THREE MONTHS AFTER CONCEPTION


  • The fetus is 7.5 cm long.

  • The fetus becomes active, moving its arms, legs, head, and opening and closing its mouth.
• THE END OF THE FOURTH MONTH


  • The fetus is 15 cm. long.

  • Arm and leg movements can be felt by the mother for the first time.