PSYC 50Developmental Psychology

Section 2 Chapter 3: Biological Beginnings

THE EVOLUTIONARY PERSPECTIVENatural Selection: is the evolutionary process that favors individuals of a species that are best adapted to survive and reproduce.

Adaptive behavior: behavior that promotes an organism’ survival in the natural habitat.

Evolutionary Psychology: emphasizes the importance of adaptation, reproduction, and “survival of the fittest” in shaping behavior.“Fit” in this sense refers to the ability to bear offspring that survive long enough to bear offspring of their own.

David Buss (1995, 2000, 2004), believes that just as evolution shapes our physical features, such as body shape and height, it also pervasively influences how we make decisions, how aggressive we are, our fears, and our mating patterns.

GENETIC FOUNDATIONSEvery species has a mechanism for transmitting characteristics from one generation to the next. This mechanism is explained by the principles of genetics. Each of us carries a “genetic code” that we inherited from our parents, and it is a distinctly human code. Because it carries this human code, a fertilized human egg cannot grow into an egret, eagle, or elephant.

Chromosomes: threadlike structures that contain the remarkable substance DNA; there are 23 pairs of chromosomes.

DNA: a complex molecule that contains genetic information. It has a double helix shape, like a spiral staircase.

Genes: units of hereditary information composed of DNA. Genes direct cells to reproduce themselves and to assemble proteins.

How do genes manage to get passed from generation to generation and end up in all of the trillion cells in the body?

1. MITOSIS – cellular reproduction in which the cell’s nucleus duplicates itself with two new cells being formed, each containing

the same DNA as the parent cell, arranged in the same 23 pairs of chromosomes.

2. MEIOSIS – a specialized form of cell division that produces cells with only one copy of each chromosome. Meiosis forms eggs and sperm (or gametes).

3. FERTILIZATION – a stage in the reproduction process whereby an egg and a sperm fuse to create a single cell, called a zygote.

Zygote – a single cell formed through fertilization

Genotype – person’s genetic heritage; the actual genetic material.

Phenotype – the way an individual’s genotype is expressed in observed and measurable characteristics.

GENETIC PRINCIPLES: Dominant-Recessive Genes Principle – if one gene of a pair is

dominant and one is recessive, the dominant gene exerts its effect, overriding the potential influence of the other, recessive gene.

Sex-Linked Genes – X-linked inheritance is the term used to describe the inheritance of an altered (mutated) gene that is carried on the X chromosome.

Genetic Imprinting – occurs when genes have differing effects depending on whether they are inherited from the mother or the father.

Polygenic Inheritance – occurs when many genes interact to influence a characteristic.

CHROMOSOME AND GENE-LINKED ABNORMALITIES:

Chromosome Abnormalitieso Down Syndrome – a chromosomally transmitted form

of mental retardation, caused by the presence of an extra copy of chromosome 21.

o Sex-Linked Chromosome Abnormalities Klinefelter syndrome – a chromosome

disorder in which males have an extra X chromosome, making them XXY instead of XY.

Fragile X syndrome – a chromosome disorder involving an abnormality in the X chromosome, which becomes constricted and often breaks.

Turner syndrome – a chromosome disorder in females in which either an X chromosome is missing, making the person XO instead of XX, or the second X chromosome is partially deleted.

XYY syndrome – a chromosome disorder in which males have an extra Y chromosome.

Gene-Linked Abnormalitieso Phenylketonuria (PKU) - genetic disorder in which an

individual cannot properly metabolize phenylalanine, an amino acid. PKU is now easily detected but, if left untreated, results in mental retardation and hyperactivity.

o

Sickle-cell anemia – a genetic disorder that affects the red blood cells and occurs most often in people of African descent; blood disorder that limits the body’s oxygen supply; it can cause joint swelling, as well as heart and kidney failure.

NAME DESCRIPTION TREATMENT INCIDENCE

Cystic fibrosis

Glandular dysfunction that interferes with mucus production; breathing and digestion are hampered, resulting in a shortened life span.

Physical and oxygen therapy, synthetic enzymes, and antibiotics; most individuals live to middle age.

1 in 2,000 births

Diabetes Body does not produce enough insulin, which causes abnormal metabolism of sugar.

Early onset can be fatal unless treated with insulin.

1 in 2,500 births

Hemophilia

Delayed blood clotting causes internal and external bleeding.

Blood transfusions/injections can reduce or prevent damage due to internal bleeding.

1 in 10,000 males

Huntington disease

Central nervous system deteriorates producing problems in muscle coordination and mental deterioration.

Doesn’t usually appear until age 35 or older; death likely 10 to 20 years after symptoms appear.

1 in 20,000 births

Spina bifida

Neural tube disorder that causes brain and spine abnormalities.

Corrective surgery at birth, orthopedic devices, and physical/medical therapy.

2 in 1,000 births

Tay-Sachs disease

Deceleration of mental and physical development caused by an accumulation of lipids in the nervous system.

Medication and special diet are used, but death is likely by 5 years of age.

One in 30 American Jews is a carrier

CYSTIC FIBROSIS

PRENATAL DIAGNOSTIC TESTS:o Amniocentesis – a prenatal medical procedure in which a sample

of amniotic fluid is withdrawn by syringe and tested for any chromosome or metabolic disorders; performed between the 12 th

and 16th weeks of pregnancy.

o Ultrasound sonography – a prenatal medical procedure in which high-frequency sound waves are directed into the pregnant woman’s abdomen; can detect disorders such as microencephaly, a form of mental retardation involving an abnormally small brain, as well as giving clues to the baby’s sex.

o Chorionic villus sampling – a prenatal medical procedure in which a small sample of the placenta (the vascular organ that links the fetus to the mother’s uterus) is removed at some point between the 8th and 11th weeks of pregnancy; allows a decision about abortion to be made near the end of the first 12 weeks of pregnancy, a point when an abortion is safer and less traumatic than after amniocentesis, which is done between 12 and 16 weeks of pregnancy.

o Maternal blood screening / Triple screen – identifies pregnancies that are at higher risk for birth defects such as spina bifida and Down syndrome; it currently measures three substances in the mother’s blood: alpha-fetoprotein, estriol, and human chorionic gonadotropin.

INFERTILITY – defined as the inability to conceive a child after 12 months of regular intercourse without contraception.

In vitro fertilization (IVF) – eggs and sperm are combined in a laboratory dish. If any eggs are successfully fertilized, one or more of the resulting embryos is transferred into the woman’s uterus or womb.

Gamete intrafallopian transfer (GIFT) – a doctor inserts eggs and sperm directly into a woman’s fallopian tube.

Zygote intrafallopian transfer (ZIFT) – this a two-step procedure. First, eggs are fertilized in the laboratory. Then, any resulting zygotes are transferred to a fallopian tube.

MENPROBLEM POSSIBLE CAUSES TREATMENT

Low sperm count Hormone imbalance, varicose vein in scrotum, possibly environmental pollutants, lead, arsenic

Drugs (cocaine, marijuana, some steroids and antibiotics)

Y chromosome gene deletions

Hormone therapy, surgery, avoiding excessive heat

Immobile sperm Abnormal sperm shapeInfectionMalfunctioning prostate

NoneAntibioticsHormones

Antibodies against sperm

Problem in immune system

Drugs

WOMENPROBLEM POSSIBLE CAUSES TREATMENT

Ovulation problems Pituitary or ovarian tumorUnderactive thyroid

SurgeryDrugs

Antisperm secretions Unknown Acid or alkaline douche, estrogen therapy

Blocked fallopian tubes Infection caused by IUD or abortion or by sexually transmitted infection

Eggs surgically removed from ovary and placed in uterus

Endometriosis (tissue buildup in uterus)

Delayed parenthood until the thirties

Hormones, surgical removal of uterine tissue buildup

BEHAVIOR GENETICS – the field that seeks to discover the influence of heredity and environment on individual differences in human traits and development.

TWIN STUDY – a study in which the behavioral similarity of identical twins is compared with the behavioral similarity of fraternal twins.

Identical Twins (called monozygotic twins) – develop from a single fertilized egg that splits into two genetically identical replicas, each of which becomes a person.

Fraternal Twins (called dizygotic twins) – develop from separate eggs and separate sperm.

ADOPTION STUDY – a study in which investigators seek to discover whether the behavior and psychological characteristics of adopted children are more like their adoptive parents, who have provided a home environment, or more like their biological parents, who have contributed their heredity. Another form of the adoption study is to compare adopted and biological siblings.

HEREDITY-ENVIRONMENT CORRELATIONS – which means that individuals’ genes influence the types of environments to which they are exposed.

Behavior geneticist Sandra Scarr (1993) described three ways that heredity and environment are correlated:

Heredity-Environment Correlation

Description Examples

Passive genotype-environment correlations

Children inherit genetic tendencies from their parents and parents also provide an environment that matches their own genetic tendencies.

Musically inclined parents usually have musically inclined children and they are likely to provide an environment rich in music for their children.

Evocative genotype-environment correlations

The child’s genetic tendencies elicit stimulation from the environment that supports a particular trait. Thus genes evoke environmental support.

A happy outgoing child elicits smiles and friendly responses from others.

Active (niche-picking) genotype-environment correlations

Children actively seek out “niches” in their environment that reflect their own interests and talents and are thus in accord with their genotype.

Libraries, sport fields, and a store with musical instruments are examples of environmental niches children might seek out if they have intellectual interests in books, talent in sports, or musical talents, respectively.

SHARED ENVIRONMENTAL EXPERIENCES – siblings’ common environmental experiences, such as their parents’ personalities and intellectual orientation, the family’s socioeconomic status, and the neighborhood in which they live.

NONSHARED ENVIRONMENTAL EXPERIENCES – the child’s own unique experiences, both within the family and outside the family, that are not shared by another sibling. Thus, experiences occurring within the family can be part of the “nonshared environment.”

EPIGENETIC VIEW – emphasizes that development is the result of an ongoing, bidirectional interchange between heredity and environment.

REFLECTION:1. Which is more persuasive to you: the views of evolutionary

psychologists or their critics? Why? 2. What are some possible ethical issues regarding genetics and

development that might arise in the future?3. Someone tells you that they have analyzed their genetic

background and environmental experiences and reached the conclusion that environment definitely have had little influence on their intelligence. What would you say to this person about their ability to make this self-diagnosis?

Reference: Santrock, J.W. (2006). Life-Span Perspective.10th Edition. McGraw-Hill. New York.

Prepared by:Mrs. Maria Angela L. Diopol

Instructor