PSY1BAM Week 2 Evolution and Genetics Mini-lecture notes 1 slide page

Part 1: Evolution by Natural Selection

Overview

This part covers key principles of evolution, organism classification, and the relevance of studying brain behaviors in non-human animals:

• Principles of evolution: Core tenets that explain the mechanisms driving the diversity of life on earth.

• Classification of organisms: The systematic categorization that aids in understanding the relationships and evolutionary history among species.

• The significance of non-human animals in understanding brain function and behavior: Insights gained from studying other species enhance our comprehension of human psychology and neuroscience.

Natural Selection Drives Evolution

Key Concepts:

• Rapid population increase is possible unless limited by factors such as predation, disease, or limited resources.

• Variation among individuals in a species exists, with traits that can be inherited; these variations can be structural, behavioral, or functional.

• Not all individuals survive to reproduce; survival challenges in the environment mean that only a subset of the population will pass on their genes.

• Variations influence survival and reproduction, leading to adaptation, where beneficial traits become more common in the population over generations.

Adaptations and Sexual Selection

Charles Darwin observed that certain variations improve survival and reproductive success through adaptations.

• Adaptations: Traits that enhance an organism's abilities to survive and thrive in particular environments.

• Sexual Selection: A form of natural selection where anatomical and behavioral traits evolve based on their appeal to potential mates, such as bright colors or elaborate courtship behaviors.

Convergent Evolution

Definition:

Convergent evolution occurs when unrelated species develop similar adaptations due to facing comparable environmental pressures, leading to analogous traits.

Example Terms:

• Homoplasy: Similar features that arise in species independently due to convergent evolution, not from common ancestry.

• Differences between homology (common ancestry) and analogy (similar function) help elucidate evolutionary relationships among species.

Mendel's Insights on Genetic Variation

Darwin lacked knowledge of genetic variations and mechanisms of inheritance, a gap filled by Gregor Mendel’s work in the 19th century, which laid the foundation for modern genetics.

• Mutations: Changes in DNA sequences that can lead to new traits and greater genetic diversity.

• Pangenes: An early concept by Hugo de Vries that proposed the idea of gemmules, influencing later genetic research.

Classification of Species

Carolus Linnaeus's System:

The modern classification system developed by Carl Linnaeus introduced a two-name species classification (Genus and Species) that organizes biological diversity logically.

• Example of Domestic Dog:

  • Species: Canis familiaris

  • Genus: Canis

  • Family: Canidae

  • Higher Taxa: Kingdom (Animalia), Phylum (Chordata), Class (Mammalia), Order (Carnivora), Genus (Canis), Species (C. familiaris).

Hierarchical taxonomy includes:

• Kingdom: Broadest category, grouping all life.

• Phylum: Grouping organisms based on major body plans.

• Class: Grouping organisms with similar traits within a phylum.

• Order, Family, Genus, and Species progressively narrow focus to specific organisms.

Importance of Studying Non-Human Animals

Reasons to Study:

• Unique traits and abilities, such as enhanced sensory skills in certain species, provide insights into evolutionary adaptations.

• Ethical considerations: Non-human species serve as models for diseases, allowing for ethical research avenues without harming humans.

• Comparative studies enhance understanding of processes involved in human evolution and cognitive functions.

Part 2: Evolution of the Brain

Brain Evolution Overview

Vertebrate brains share a common basic structure, revealing evolutionary relationships.

Historical Trends:

• The increase in overall brain size correlates with behavioral complexity; more complex behaviors often require more sophisticated neural architecture.

• Fossil studies and examinations of modern species provide crucial insights into evolutionary changes in brain structures over time.

Vertebrate Nervous System Features

Key Characteristics Include:

• Development from a dorsal neural tube, which is essential for forming the central nervous system.

• Bilateral symmetry, which has implications for motor control and sensory processing.

• Segmentation: The division of the body and nervous system into segments, which reflects evolutionary adaptations.

• Hierarchical control where different brain regions manage different functions, leading to efficient information processing.

• Localization of function: Specific brain regions being responsible for particular cognitive or bodily functions.

Brain Size and Body Size Relationship

Encephalization Quotient:

A measure used to compare brain weight and body weight across species, providing insights into cognitive abilities relative to body size.

• General Trend: Increase in brain size relative to body size over evolutionary history indicates a trend towards greater cognitive complexity.

Costs of a Large Brain

Challenges Faced Include:

• Long gestation periods and the prolonged dependency of offspring due to the complex brains require significantly more time to develop.

• High metabolic demands: Larger brains consume more energy, requiring additional resources (e.g., increased oxygen and glucose usage).

• Developmental duration influences brain size, a concept termed neoteny, where juvenile traits are retained in adults, impacting overall brain development.

Part 3: Genetics for Psychology

Genetics and Psychology

Genetic factors underpin mental health and behavioral traits, emphasizing the importance of understanding heredity in psychology.

• Concordance in Twin Studies: Research findings, such as schizophrenia showing about 50% concordance in identical twins, highlight genetic influences on behavior.

• The environment plays a critical role in shaping gene expression and mental health outcomes, illustrating the complex interaction between nature and nurture.

Gene Expression and Inheritance

Gene Expression:

The process of converting genetic information into cellular traits, which significantly influences an organism's physical characteristics and capabilities (e.g., protein synthesis).

• Genotype vs. Phenotype:

  • Genotype: The complete set of genes inherited from both parents.

  • Phenotype: The observable characteristics or traits of an organism, influenced by both the environment and genotype.

Genetic Variation and Interactions

Genetic variation arises via sexual reproduction and mutations, contributing to the diversity of traits within populations.

• Single Nucleotide Polymorphisms (SNPs): Variants in the genetic code that are studied for their roles in affecting behaviors and susceptibilities to mental health disorders.

• Gene-environment interactions are essential in understanding the etiology of psychological issues and conditions, illustrating the complexity of genetic and environmental influences.

Summary of Key Concepts

• Evolutionary Principles: Concepts of natural selection, genetic mechanisms, and comparative studies in animals significantly enrich our understanding of brain evolution and behavior.

• Genetic Foundations: Acknowledging the interplay between genetics and environment is crucial for comprehending mental health and psychological traits