Descent-with-Modifications-lecture

Descent with Modifications

Essential Learning Competency

  • Show patterns of descent with modification from common ancestors to produce organismal diversity.

Overview

  • Coined by Charles Darwin in On the Origin of the Species.

  • All organisms related through descent from ancestors.

  • Species today evolved from ancestral species by adaptations.

  • Common ancestry links all life into a single tree.

  • Last Universal Common Ancestor (LUCA) is the source of all life.

Major Concepts

Natural Selection

  • Survival of the fittest guides evolution.

  • Competition leads to developments adapted to environmental changes.

  • New species arise from these adaptations over long periods.

Common Descent

  • All species, living or extinct, arise from common ancestors.

  • A “tree of life” depicts these relationships.

Speciation

  • Multiple species can derive from a single ancestral population.

  • The closer the common ancestor, the more related the species.

Fossil Records

  • Track common ancestors dating back 650 million years.

Influences on Darwin

  • Influenced by Lamarck's Theory of Use and Disuse and Linnaeus' binomial nomenclature.

  • Built on discoveries of DNA by Watson and Crick, and Mendelian genetics.

Evidence for Evolution

Types of Evidence

  1. Fossil records

  2. Geographical distribution

  3. Homologous structures

  4. Embryological similarities

Molecular Evidence

  • Phylogenetic trees: Show common origins based on genetic sequences.

  • Common biochemistry: Life forms share fundamental biochemical processes.

  • Common genetic code: Nearly identical genetic code across all life forms supports common descent.

  • Selectively neutral similarities: Genetic variations and mutations provide evidence of common ancestry.

  • Other similarities: Present in cellular structures and metabolism, supporting the LUCA concept.