Populations & Evolution Fundamentals

Populations & Evolution Fundamentals

• Populations evolve, with changes in allele frequencies over time
• Primates, including humans, have a shared evolutionary history
• Evolutionary relationships can be visualized using phylogenetic trees
• Different primate groups are shown on a phylogenetic tree with lemurs, lorises, tarsiers at the base. Higher order primates like monkeys and apes follow
• Multiple primate lineages, like New World monkeys, Old World monkeys and apes appear at progressive stages
• Early primates are shown at the bottom of the branching tree.

Aims of Studying Populations & Evolution

• Define key terms related to populations and evolution
• Discuss the applications of population and evolutionary principles
• Present examples of evolutionary changes
• Identify problems and controversies related to evolution
• Explain and demonstrate why this topic is important for the study of Biomedical Sciences

What is Evolution?

• Evolution is the process of inheritable change in a population over time
• Microevolution describes evolutionary changes within a population.
• Macroevolution describes changes at the level of species and their evolutionary history, including the fossil record

Forms of Evolution

• Microevolution: changes within populations (adaptive or neutral)
• Macroevolution: changes at the species level and fossil record

Evolution Needs

• Mutable Heritable Base (DNA): Genetic variation is passed from generation to generation due to differences in DNA
• Time: Evolutionary changes occur over long periods of time

Other Evolutionary Concepts

• Neutral Evolution: DNA changes that occur without phenotypic advantage. They do not alter fitness
• Genetic Drift: Random changes in allele frequencies due to chance events.
• Heritable Variation: DNA changes passed to the next generation

Mutable? Variation?

• DNA passes from one generation to the next through sexual reproduction (meiosis and fertilization)
• Changes at the DNA level (mutations) can be neutral, positive, or negative.
• Mutations involve changes in amino acid sequences

What Drives Evolution?

• Selective Pressure: Environmental changes, such as temperature changes, diseases (HIV, Ebola), food availability, or other environmental factors. These influences drive the selection of traits

Types of Evolution

• Adaptive Evolution: Changes driven by random DNA changes increase fitness. Individuals better adapted to environments survive and reproduce more often. This will cause allele frequencies to change.
• Natural Selection: The survival and reproduction of individuals based on their traits
• Sex Selection: The choice of mates based on phenotypic traits

Fitness

• Fitness is a measure of reproductive success of individuals, within a population.
• Evaluating fitness can involve tracing relationships between parents, offspring or grand-children.

Fitness for Humans

• A balance of energy intake (food) to output (activities). This impacts human fitness.
• Fitness can be affected by access to food, contraception, etc.

Population Relationships

• A cyclic, ongoing process: Mutations, crossover, selections and evaluations impact population trends

Why is Population and Evolution Important to BMS?

• Human-associated species: BMS impacts the environment, and in turn it is affected. This is important because changes at the micro and macro level influence populations.
• Changing evolutionary history: Human actions are altering the genetic makeup of both humans and other species.

What Is a Species?

• Organisms that can share grandchildren are considered part of a species.
• Anatomically, phenotypically and genetically similarities are important

Phylogenetic Tree

• A branching diagram showing evolutionary relationships between organisms.
• A diagram depicts the evolutionary relationships between various species
• The terms genus and species are used to depict the relationship between species.
• Homo sapiens is a particular species of human

Additional Concepts

• Population genetics: studies the frequency of different alleles in populations, including those that result from mutations, selection, in-breeding, assortative mating, gene flow and random genetic drift
• Hardy-Weinberg equilibrium: describes the theoretical conditions under which allele frequencies do not change in populations over time, This is used to assess relative frequencies
• Calculating allelic frequencies using Hardy-Weinberg equations: Shows how to predict genotype and allele frequencies when conditions are not in equilibrium
• Worked examples help determine allele frequencies using mathematical calculations demonstrating these principles
• Other topics include human disease development and evolution and the use of technology for population analysis (genomics) such as population genetic tools

Change and Variation

• Variation within populations is considered
• Plasticity, or non-heritable changes, can impact populations. These are examples of change that do not involve evolution, but are adaptations to environments

Examples of Change in Populations

• Physical traits, like height, are influenced by both genes and environmental factors.
• Medical advances, such as antibiotic use, have driven evolutionary changes in bacteria.
• Population genetics examines patterns (population change) and how human actions impact genetic makeup and evolutionary processes.

Evolution and Disease

• Co-evolution is the relationship between malaria and sickle cell anemia provides an example of the interaction between population genetics patterns, disease and evolution. Selective pressure has shaped human evolution
• Examples and case studies illustrate how different selection pressures have led to the rise in specific genetic diseases.

Removing Genes from the Population

• Genetic screening and counselling
• Prenatal genetic screening and pre-implantation genetic diagnosis.

Additional Concepts

• Gene therapy and germ-line gene therapy
• The alteration of DNA impacts populations and medical treatment and prevention

History of Human Populations

• Genetic features of humans are traced
• Evolution of human populations is examined via history
• Diseases and their prevalence, are illustrated by charts and maps, including those illustrating the prevalence of malaria, sickle-cell anemia, cystic fibrosis, and antibiotic-resistant bacterial strains.