Biological Beginnings

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Chapter 2

• Biological Beginnings
• PowerPoints developed by Jenni Fauchier,
  Metropolitan Community College -- Omaha

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The Evolutionary Perspective

• Natural Selection and Adaptive Behavior
• natural selection -- the evolutionary process by
  which those individuals of a species that are
  best adapted are the ones that survive and
  reproduce
• survivors are better adapted to their world than
  are the non-survivors
• (Darwin, 1859) (Johnson Losos, 2008)

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Evolutionary Psychology

• Emphasizes the importance of adaptation,
  reproduction, and survival of the fittest in
  shaping behavior
• Fit -- the ability to bear offspring that survive
  long enough to bear offspring of their own
• the ability to pass your genes to the next
  generation (Promislow, Fedorka, Burger, 2006)

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Developmental Evolutionary Psychology

• Humans take longer to become reproductively
  mature
• Humans require time to develop a large brain and
  learn the complexity of human societies
• Thus, length of childhood period is extended
• Evolved mechanisms are not always adaptive in
  contemporary society

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Evaluating Evolutionary Psychology

• Bandura (1998) rejects what he calls one-sided
  evolutionism
• An alternative is a bidirectional view, in which
  environmental and biological conditions influence
  each other
• Evolution gave us bodily structures and
  biological potentialities
• People have used their biological capacities to
  produce diverse cultures -- aggressive and
  pacific, egalitarian and autocratic

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Genetic Foundations of Development

• Each of us carries a genetic code that we
  inherited from our parents
• A fertilized human egg carries this human code
• Fertilized human egg cannot grow into any other
  species
• Each of us began life as a single cell which
  contained our entire genetic code

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Chromosomes

• Nucleus of each human cell contains chromosomes
• Chromosomes -- thread-like structures made up of
  deoxyribonucleic acid, or DNA
• DNA is a complex molecule that has a double helix
  shape, like a spiral staircase, and contains
  genetic information

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Genes

• Genes - units of hereditary information
• short segments of DNA
• Genes direct cells to reproduce themselves and to
  assemble proteins
• Proteins
• the building blocks of cells
• the regulators that direct the bodys processes
• (Mader, 2008)

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Human Genome Project

• Preliminary map of the human genome -- the
  complete set of developmental instructions for
  creating proteins that initiate the making of a
  human organism
• Each human has 20,000 30,000 genes
• Human genome consists of many genes that
  collaborate both with each other and with
  non-genetic factors inside and outside the body
• Genetic expression is affected by their
  environment

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Mitosis

• All body cells, except the sperm and egg, have 46
  chromosomes arranged in 23 pairs
• Body cells reproduce by a process called mitosis
• During mitosis, the cells nucleusincluding the
  chromosomesduplicates itself and the cell
  divides
• Two new cells are formed, each containing the
  same DNA as the original cell

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Meiosis

• Sex cell division is different type of cell
  division
• Eggs and sperm (or gametes) are formed in meiosis
• A cell of the testes (in men) or ovaries (in
  women) duplicates its chromosomes but then
  divides twice, thus forming four cells
• Each of these has only half of the genetic
  material of the parent cell
• By the end of meiosis, each egg or sperm has 23
  unpaired chromosomes

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Fertilization

• Zygote -- an egg and a sperm fuse to create a
  single cell
• In the zygote, the 23 unpaired chromosomes from
  the egg and sperm combine to form one set of 23
  paired chromosomes
• One chromosome of each pair is from the mothers
  egg and the other from the fathers sperm
• Each parent contributes half of the offsprings
  genetic material

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The 23rd Pair of Chromosomes

• Slight difference in the 23rd pair
• In females, the 23rd pair consists of two
  chromosomes called X chromosomes
• In males, the 23rd pair consists of an X and a Y
  chromosome
• The presence of a Y chromosome is what makes an
  individual male

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Sources of Variability

• Combining genes of two parents increases genetic
  variability in the population
• Chromosomes in the zygote are not exact copies of
  the parents
• Another source of variability comes from DNA
• mutated gene -- a permanently altered segment of
  DNA

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Genotype and Phenotype

• Genotype -- all of a persons genetic material
• Phenotype -- observable characteristics
• Phenotypes include
• physical characteristics (such as height, weight,
  and hair color)
• psychological characteristics (such as
  personality and intelligence)

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Dominant-Recessive Genes Principle

• Dominant -- one gene of a pair always exerts its
  effects
• Recessive gene -- exerts its influence only if
  the two genes of a pair are both recessive
• may be overridden by a dominant gene
• may be carried from generation to generation but
  not expressed in phenotype

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Sex-Linked Genes

• X-linked inheritance -- mutated gene is carried
  on the X chromosome
• males have no backup copy to counter the
  harmful gene
• females have a second X chromosome, which is
  likely to be unchanged
• Females who have one changed copy of the X gene
  are known as carriers
• (Turner, 2006)

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Polygenic Inheritance

• Genetic transmission is usually quite complex
• few characteristics reflect the influence of only
  a single gene or pair of genes
• Polygenically determined characteristics --
  determined by the interaction of many different
  genes

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Chromosome Abnormalities 

• Down syndrome -- caused by the presence of an
  extra copy of chromosome 21
• once in every 700 live births
• women aged 16 - 34 are less likely to give birth
  to a child with Down syndrome
• Sex-Linked Chromosome Abnormalities

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Sex-Linked Chromosome Abnormalities

• Klinefelter syndrome -- extra X chromosome
• Fragile X syndrome -- results from an abnormality
  in the X chromosome
• X chromosome becomes constricted and often breaks
  
• Turner syndrome -- females have either an X
  chromosome missing or part of one X chromosome is
  deleted
• XYY syndrome male has extra Y

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Gene-Linked Abnormalities

• Phenylketonuria (PKU) -- individual cannot
  properly metabolize phenylalanine, an amino acid
• left untreated, phenylalanine builds up in the
  child, producing mental retardation and
  hyperactivity
• Sickle-cell anemia -- genetic disorder that
  impairs the bodys red blood cells
• most often in African Americans
• red blood cell becomes a hook-shaped sickle
  that cannot carry oxygen properly

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Other diseases that result from genetic
abnormalities

• Cystic fibrosis
• Diabetes
• Hemophilia
• Huntington disease
• Spina bifida
• Tay-Sachs disease

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Behavior Genetics

• Behavior genetics seeks to discover the influence
  of heredity and environment on individual
  differences in human traits and development
• Behavior geneticists often study either twins or
  adoption situations
• (Plomin, DeFries, Fulker, 2007 Vogler, 2006)

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The Epigenetic View

• Development is the result of an ongoing,
  bi-directional interchange between heredity and
  the environment
• Heredity and environment operate togetheror
  collaborateto produce a persons intelligence,
  temperament, height, weight, ability to pitch a
  baseball, ability to read, etc. (Gottlieb,
  Wahlsten, Lickliter, 2006)

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The Course of Prenatal Development

• Fertilization to birth
• Prenatal development lasts approximately 266 days
  
• Three periods
• Germinal
• Embryonic
• Fetal

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The Germinal Period

• First two weeks after conception
• Creation of the fertilized egg (the zygote)
• Cell division
• Attachment of the zygote to the uterine wall

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The Germinal Period

• Blastocyst -- consists of an inner mass of cells
  that will eventually develop into the embryo
• Trophoblast -- outer layer of cells that later
  provides nutrition and support for the embryo
• Implantation -- the attachment of the zygote to
  the uterine wall
• takes place about 10 to 14 days after conception

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The Embryonic Period

• Occurs from two to eight weeks after conception
• Rate of cell differentiation intensifies
• Begins as the blastocyst attaches to the uterine
  wall
• Every body part eventually develops from these
  three layers
• endoderm
• ectoderm
• mesoderm

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The Embryonic Period

• The mass of cells is an embryo
• Organogenesis -- the process of organ formation
  during the first two months of prenatal
  development
• organs are especially vulnerable to environmental
  influences
• Life-support systems for the embryo develop
  rapidly

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Life-support Systems for the Embryo

• Amnion -- bag containing a clear fluid in which
  the developing embryo floats
• Umbilical cord contains two arteries and one vein
  and connects the baby to the placenta
• 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

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The Fetal Period

• Fetal period begins two months after conception
  and lasts for seven months
• Three months after conception -- fetus is about 3
  inches long weighs about 3 ounces
• At birth, the average American baby weighs 7 ½
  pounds and is about 20 inches long

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Three Trimesters

• The germinal and embryonic periods occur in the
  first trimester
• The fetal period begins toward the end of the
  first trimester and continues through the second
  and third trimesters
• Viability (the chances of surviving outside the
  womb) occurs at the beginning of the third
  trimester

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Prenatal Tests

• Ultrasound sonography
• non-invasive
• high-frequency sound waves
• Chorionic villi sampling
• tiny tissue sample from the placenta is removed
  and analyzed
• Amniocentesis
• sample of amniotic fluid is withdrawn and tested
  for chromosome or metabolic disorders
• Maternal blood screening
• identifies pregnancies that have an elevated risk
  for birth defects
• (Bromage, 2006).

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The Birth Process

• The Birth Process
• first stage -- contractions cause the womans
  cervix to stretch and open
• second stage begins when the babys head starts
  to move through the cervix
• third stage is afterbirth
• placenta, umbilical cord, and other membranes are
  detached and expelled

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Methods of Childbirth

• Medications
• Three basic kinds of drugs
• Analgesia
• Anesthesia
• Oxytocics
• Natural and Prepared Childbirth
• Natural childbirth reduce pain with breathing
  techniques and relaxation
• Prepared childbirth a.k.a. Lamaze

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• Other Non-Medicated Techniques to Reduce Pain
• Waterbirth -- giving birth in a tub of warm water
  
• likely to be less stressful for the baby and the
  mother
• Massage -- reduce pain and anxiety
• Acupuncture -- insertion of strategically located
  needles

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Breech or Cesarean Delivery

• Breech position buttocks rather than head
  emerge first
• Can prevent the baby from breathing normally
• Cesarean delivery -- the baby is removed from the
  mothers uterus through an incision made in her
  abdomen
• May be lifesaving but carries the risks of major
  surgery

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Apgar Scale

• Used to assess the health of newborns at one and
  five minutes after birth
• A score, or reading, of 0, 1, or 2 on each of
  these five health signs
• heart rate, respiratory effort, muscle tone, body
  color, and reflex irritability
• Anoxia -- an insufficient supply of oxygen

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Threats to Newborns

• Low birth weight -- less than 5 ½ pounds at birth
• Very low birth weight - under 3 pounds
• Extremely low birth weight - under 2 pounds.
• Preterm -- born three weeks or more before full
  term
• Small-for-date -- birth weight is below normal
  when the length of the pregnancy is considered

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Incidence and Consequences of Low Birth Weight 

• Incidence of low birth weight varies considerably
  from country to country
• Related to poverty, maternal health status,
  maternal nutrition
• More health and developmental problems than
  normal-weight infants
• At school age, more likely to have a learning
  disability, attention deficit hyperactivity
  disorder, or breathing problems such as asthma
• (Moss, 2006) (Wocadlo Rieger, 2006)

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Interventions for Low Birth Weight/Preterm Infants

• Kangaroo care -- a way of holding an infant so
  that there is skin-to-skin contact for two to
  three hours per day over an extended time in
  early infancy
• Massage therapy -- firm stroking with the palms
  of the hands three times per day for 15-minute
  periods
• Bonding -- formation of a connection, especially
  a physical bond, between parents and the newborn
  in the period shortly after birth
• (Feldman others, 2003) (Field others, 1986)

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The Postpartum Period

• Postpartum period -- lasts for about six weeks
  after childbirth or delivery or until the
  mothers body has completed its adjustment and
  has returned to a nearly pre-pregnant state
• Physical and psychological adjustments
• Involution -- process by which the uterus returns
  to its pre-pregnant size

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Postpartum Adjustments

• Baby blues -- two to three days after birth, many
  women begin to feel depressed, anxious, and upset
• Postpartum depression -- a major depressive
  episode about four weeks after delivery
• Fathers also undergo considerable adjustment in
  the postpartum period, even when they work away
  from home all day