Evolutionary Biology Overview

Diversity of Life

• Earth is home to approximately 8.7 million species.
• Explaining this vast diversity has challenged scientific understanding throughout history.
• Debates about evolutionary theories, including disagreements with natural selection, persist.

Mechanisms of Biological Evolution

• Five primary mechanisms drive biological evolution:
  • Natural selection
  • Sexual selection
  • Genetic drift
  • Gene flow
  • Mutation

Observations Before Darwin & Wallace

• Life forms change over time.
• Biological characteristics serve specific functions.

Darwin & Wallace's Explanatory Challenge

• Understanding the why of evolutionary changes.
• Explaining the origin of new species.
• Determining the purpose of physical traits.

The Origin of Species (1859)

• Three key pillars underpin natural selection:
  • Competition:
    • Unlimited resources lead to exponential population growth, resulting in a struggle for existence.
  • Variation:
    • Individuals vary in their competitive abilities.
    • Individuals with advantageous variations are more likely to survive and reproduce.
  • Heritability:
    • Variations are inheritable, passed down through generations.
    • Differential reproductive success drives evolutionary changes in populations.

Natural Selection Scrutinised

• Population growth: Populations do exhibit exponential growth.
• Sufficient time: Enough time has passed for evolution to occur.
• Heritability of variation: Variation is indeed heritable.
• Sexual dimorphism: Some traits, seemingly disadvantageous for survival, arise from sexual selection, primarily affecting reproduction.

Genes

• Genes dictate both physical appearance and internal bodily functions.
• They contain instructions for protein synthesis.
• Proteins form the body's structure and are integral to life processes.
• Genes reside on DNA strands.
• Gregor Mendel (1865) described that organisms inherit two alleles (versions) of a gene per trait, one from each parent.
• DNA replicates and is passed to offspring.
• Genotype: The genetic makeup of an organism.
• Phenotype: The observable physical characteristics of an organism.
• Genetic Variation Sources:
  • Sexual reproduction
  • Mutations
  • Genetic drift
  • Gene flow

The Selfish Gene

• At the heart of biological evolution is the gene, not the individual or trait.
• Genes are self-serving.
• Biological fitness relates to the number of copies of genes passed into future generations.

Sexual Selection

• Intersexual selection (mate choice): One sex (usually female) chooses a mate based on traits.
• Intrasexual selection (competition): Individuals compete within a sex for mates, often involving physical combat or vying for resources.

Human Evolution

• A detailed evolutionary history of the human species is not provided in the text.

Explore the mechanisms of biological evolution and the diversity of life on Earth. This quiz delves into key concepts from Darwin and Wallace's theories and the challenges in explaining evolutionary changes. Test your understanding of natural selection, genetic drift, and the origins of species.