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Introduction to Psychology: Biological Basis of Behavior

This lecture explores the biological basis of human behavior, discussing how our biology and genetics influence behavior, the mechanism of heredity, genetic variation, and how genes affect brain development. It also examines the unique features of the human brain.

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Introduction to Psychology: Biological Basis of Behavior

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  1. Introduction to Psychology Suzy Scherf Lecture 4: How Do We Act? Biological Basis of Behavior

  2. Why Learn About Biology? • Permits us to see human behavior as having a lot in common with that of other animals. • Considering our biology enables us to see how evolutionary processes have shaped our behavior. • When the biology/brain is disrupted, so is behavior!

  3. The Mechanism of Heredity • If a trait is not heritable - • Genes code for ________ human traits as well as a ________ set of individual traits • Genes are -

  4. Genes are particles The Mechanism of Heredity • Genes not diluted when combined - • Normal adults diploid -

  5. The Structure of Genetic Material • Genes have different versions called ________ • For each gene -

  6. 1. Homozygous - 2. Heterozygous - different versions of alleles The Structure of Genetic Material Kinds of alleles:

  7. 1. Dominant - 2. Recessive - The Structure of Genetic Material Kinds of Heterozygous alleles:

  8. The Structure of Genetic Material Kinds of Heterozygous alleles: 3. Co-Dominant -

  9. The Structure of Genetic Material • Genes organized as ___________ in nucleus of all cells • 23 pairs of chromosomes in each cell • Each chromosome has a definite structure -

  10. Human Chromosomes

  11. Human Chromosomes

  12. De Brazza Monkey Chromosomes

  13. Sexual Reproduction and Genetic Transmission • Offspring get __% genes from mom and __% from dad • Why not reproduce asexually and pass on 100% of genes?

  14. The Need for Genetic Variation Evolution needs to have genetic variation in order to select the genes that contribute to solving the problems presented by the local environment.

  15. Major Sources of Genetic Variation 1. Each mature sex cell has 1 per 8 billion possible assortments of chromosomes. 2. During meiosis crossing over -

  16. Major Sources of Genetic Variation 3. Random Assortment - 4. Mutations -

  17. Genes to Traits • Genes always working in combination with the environment - • Genes don’t directly make bones, muscle, or brains • Genes code and oversee the assembly of specific _______ and _________

  18. Genes and Traits • Very rarely does a single gene determine a trait, most especially a behavioral trait. • Most behavioral traits are polygenetic -

  19. Genotype vs. Phenotype • Genotype - • Phenotype -

  20. Determinants of Phenotypic Expression 1. Reaction Range - 2. Canalization -

  21. Determinants of Phenotypic Expression 3. Resilient Traits - 4. Fragile Traits -

  22. Beware! Genetic Fallacy:

  23. How do Genes Affect Behavior and Development? Genes code for: 1. 2. 3. 4.

  24. How do Genes Affect Behavior and Development? 1. Genes influence the development of facultative traits - Genes influence way the central nervous system works

  25. How do Genes Affect Behavior and Development? Genes influence way the central nervous system works

  26. Two Focused Questions on Brains 1. What are our brains for? 2. How do our brains work?

  27. What’s Special about Our Brain? Does Size Matter?

  28. What’s Special about Our Brain? Does Shape Matter?

  29. Lucy’s Skull Neanderthal Skull • Australopithecus afarensis • Ethiopia 3.5 million yrs. old • 3’8” tall • 1/3 brain size of modern humans • Archaic Homo Sapiens • 300,000 years ago • Brain size 1175 cc • Modern human brain size 1400 cc

  30. Evolutionary Scale Lucy Neanderthal Human

  31. What’s Special about our Brains?

  32. What’s Special about our Brains?

  33. What’s Special about our Brains? Passingham (2002)

  34. What’s Special about our Brains? Semendeferi et al. (2002)

  35. What’s Special about our Brains? • Brain:body ratio • Amount of frontal cortex - • Size and organization of more specific cortical areas within frontal cortex -

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