Human DevelopmentDevelopment Parenting styles CognitionDNA Theories of development ConceptionGenes Developmental theorists AssimilationGenotype Teratogenic effects Threshold effectPhenotype Imprinting AccommodationGamete Stranger anxiety Germinal stageZygote Theory theory Embryonic stageAttachment Theory of mind Fetal stageInteraction effect Apgar scale Critical periodsAddiction Dizygotic/Monozygotic twins

• The sperm and ovum receive only one member of each chromosome pair when cells divide to produce gametes, and thus have only 23 single chromosomes each

• Gamete-a reproductive cell, a sperm or ovum that can produce a new individual if it combines with a gamete from the other sex to make a zygote

• Zygote- the single cell formed from the fusing of two gametes, a sperm & an ovum

• How does conception occur?

• Conception occurs when the male gamete (or sperm) penetrates the membrane of the female gamete (the ovum); the gametes fuse and their genetic material combines to form one zygote

• Where does the zygote develop?

• The amniotic sac is the fluid-filled pouch in which the embryo will live until birth

• The amniotic sac acts as both a cushion against the environment and as a temperature regulator

As the head of the spermatozoan enters the ovum, the ovum prevents penetration by another spermatozoan.

Conception: The Incredible Journey

• The ovum can live for 24 hours• Sperm can live for 72 hours; less than 1% can live

up to one week• Pregnancy may occur a few days before or after

ovulation• The ovum may release chemicals to signal its

location• If a sperm reaches the ovum, it wriggles violently

• The 23rd pair of chromosomes determines the sex• The chemical on the Y chromosome signals the development of the male organs• The chromosomal make up is XY in the male and XX in the female• In a stressful pregnancy, XY embryos are more likely than XXs to be expelled in a

spontaneous abortion, or miscarriage• Within hours, the zygote initiates human development through the process of duplication

and division• Implantation begins about 10 days after conception, the organism buries into the

placenta for nourishment• Then differentiation begins, this is when cells begin to specialize, taking different forms

and reproducing at various rates• At the eight-cell stage, the organism has stem cells it could develop into a body part• The cells on the outer side of the of the mass become the placenta-the organ that will

support the life• Certain genes begin to switch on an off during this developmental stage• In some pregnancies, a single zygote splits into two separate identical cells that develop

into genetically identical or monozygotic (MZ) twins• MZ twins have the potential for developing the same physical appearance and

psychological characteristics, but they are also vulnerable to specific diseases• Dizygotic (DZ) or fraternal twins begin life as separate zygotes, and share no more genes

than any other sibling (about 50 percent)

Gestation• The 1st 2 weeks of prenatal development are

called the germinal period• The embryonic period begins in the 3rd week as

the formless mass becomes a distinct being, which is now referred to as an embryo

• A thin line down the middle of the outer layer of cells is the primitive streak, and the structure becomes the neural tube, then the brain and spinal column (the central nervous system)

• The third week to the eighth week begins the embryonic phase…the developing mass can now be considered an embryo

• 5th – 6th week: primitive gonads form• 7th – 8th week: gonads become testes with Y chromosome

and the SRY gene• In the 4th week, the cardiovascular system is functioning;

the eyes, ears, nose, and mouth start to form• At 5 weeks, the arm and leg buds appear and the

primitive heart is now visible• By the end of the 2nd month, the developing organism has

all the basic organs and body parts of a human being, and a unisex structure called the indifferent gonad

• The fetal period-from the 9th week after conception, the sex organs begin to take shape

• By the 12th week, the genitals are fully formed• A sonogram is readable

• By the 12th week, the genitals are fully formed• A sonogram is readable

• At the end of the 3rd month, the fetus has all its body parts• • *22 weeks-signals the age of viability- the ability of the fetus

to live outside of the body• • During this time, the brain develops new neurons in a

process called neurogenesis and new connections between them in a process called synaptogenesis

• • Weight gain during the final 3 months is 41/2 pounds• The neurological, respiratory, and cardiovascular systems

mature dramatically; brain growth is so extensive that the brain’s cortex must fold into layers in order to fit into the skull

Stages of conception

Variables that may affect the fetus…

• Teratology is the study of birth defects; teratogens include such substance as viruses, drugs, chemicals, stressors, and environmental hazards that can impair developmental and lead to birth defects and even death

• The critical periods are times when the body is most susceptible to teratogenic damage

• For behavioral teratogens that affect the brain and nervous system, the entire prenatal period is critical

• For some teratogens, the threshold effect is imperative; this means that the substance is not harmful until the chemical reaches a certain level

• The interaction effect of teratogens occurs when one teratogen intensifies the impact of the other

• Zygotes that are formed from abnormal or fragile gametes may not duplicate, divide, or differentiate

• • * the variable that most often correlates with chromosomal

abnormalities is the mother’s age• • The most common of the extra-chromosome syndrome is Down

Syndrome (trisomy 21)• • Persons with Down Syndrome exhibit distinguishing features of the

slanted eyes, rounded face, and a thick tongue• • the extra chromosome at site 21 also makes them more

susceptible to heart defects, slow intellectual development, and by middle age Alzheimer’s disease it’s inherited

• *people with this syndrome age faster than other adults

Baby is born!What are reflexes?• Reflexes are involuntary responses to stimuli• What are some examples of reflexes?• Rooting, Babinski, stepping• The infant is born around the 38 week of pregnancy (9 ½ months)• Newborns are born with survival reflexes that prepare them for their new

world• Tonic neck reflex• When the baby is laid on its back, baby turns its head and extends arms to

same side, helps develop eye/hand coordination• Moro reflex• When baby is dropped or hears a loud noise, baby extends arms and legs

and quickly brings them in as if trying to grasp something• Withdrawal reflex• When a soft pinprick is applied to baby, the sole of baby’s foot, baby flexes

the leg, helps protect the infant from harmful stimuli

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Motor Development

First, infants begin to roll over. Next, they sit unsupported, crawl, and finally walk. Experience has little effect on this sequence.

Baby Preferences

• The infant is born with an acute auditory sense? Why do you think this is?

• Newborns have a preference for human faces, which human face do you think newborns prefer most?

• Newborns have a preference for the smell of their mother’s milk

• Newborns have a preference for sweet tastes

Habituation• One way we learn about the cognitive development of

babies is by measuring their behavior in response …sucking responses

• Another approach to understanding cognitive development is by observing the behavior of infants is through the use of habituation technique

• Habituation refers to the decreased responsiveness toward a stimulus after it has been presented numerous times in succession

• Organisms, including infants, tend to be more interested in things the first few times they experience them and become less interested in them with more frequent exposure

Developmental psychologists have used habituation to help them understand what babies remember and understand

Although they may not

consciously remember, babies are capable of learning.

3-month-old infants can learn to move a mobile by kicking. (Rovee - Collier, 1989, 1997.)

Remember the habituation procedure

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Maturation and Infant Memory

Infant Brain Development• The newborn’s brain contains more neurons than it will ever need, 70 %

are located in the cortex• In the womb, the brain forms nerve cells at one quarter mil/m• Each neuron consists of a single axon and many dendrites• The dendrites show an estimated fivefold increase in density within the

cortex from birth until age 2 • Transient exuberance is a an increase in neural connections over the first

two years have been called (use it or lose it)• • If too many stress hormones are produced early on, cortisol is released

and the developing brain becomes incapable of normal stress responses• From age 3-6, the most rapid growth is in the frontal lobes• The developing brain enables physical coordination

How the brain develops

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Cognitive DevelopmentCognition refers to all the mental activities associated with thinking, knowing, remembering, and communicating.

Developmental psychologist Jean Piaget believed that children reason differently than adults and that a child’s mind develops in a series of stages. Jean Piaget (1896–

1980)

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SchemasPiaget felt that the driving force behind our intellectual progression is an unceasing struggle to make sense of our experiences and that to do this maturing brains build schemas.

Schemas are concepts or frameworks thatorganize and interpret information.

To use our schemas Piaget proposed that we assimilate new experiences, or interpret them according to our schemas and then adjust or accommodate our schemas accordingly.

• Theory-theory is the idea that children attempt to construct theories to explain everything they see and hear

• • As preschoolers develop informal theories that attempt to

answer basic question about mental process-thoughts, emotions, beliefs, motives, and intentions-they acquire a theory of mind

• • By age 4, young children come to realize that mental

phenomena may not reflect reality and that people can deliberately deceived or fooled

• • Theory of mind is strengthened by a combination of factors,

including maturation of the brain’s prefrontal cortex• Schemas- our understanding of the world

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Egocentrism

Piaget concluded that preschool children are egocentric. They cannot perceive things from another’s point of view.

When asked to show her picture to mommy, 2-year-old Gabriella holds the picture facing her own eyes, believing that her mother can see it through her eyes.

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Preoperational StagePiaget suggested that from 2 years old to about 6-7 years old, children are in the preoperational stage—too young to perform mental operations. For example, in this stage do not understand the concept of conservation, the principle that quantity remains the same despite changes in shape.

This preoperational child does not yet understand the principle of conservation of substance. Video…