Chapter 19: Descent with Modification

Fossils and Evolutionary Theories

This section introduces the foundational concepts of evolutionary biology, including the evidence for evolution and the mechanisms proposed by early scientists.

• Fossils: Preserved remains or traces of organisms from the past, found in sedimentary rocks. Fossils provide direct evidence of evolutionary change over time.

• Lamarckian Evolution: The theory proposed by Jean-Baptiste Lamarck that organisms can pass on traits acquired during their lifetime to their offspring. This idea has been largely discredited.

• Darwinian Evolution: Charles Darwin's theory that evolution occurs through natural selection, where heritable traits that enhance survival and reproduction become more common in successive generations.

• Adaptation: A heritable trait that increases an organism's fitness in a particular environment.

• Natural Selection: The process by which individuals with advantageous traits survive and reproduce more successfully, leading to evolutionary change.

• Genetic Variation: Differences in DNA sequences among individuals in a population, providing the raw material for evolution.

• Darwin’s Tree of Life: A metaphor and diagram representing the evolutionary relationships among all living organisms, illustrating common descent.

Chapter 20: Phylogeny

Classification and Evolutionary Relationships

This section covers the methods and terminology used to classify organisms and infer their evolutionary relationships.

• Analogy: Similarity between organisms due to convergent evolution, not common ancestry.

• Basal Taxon: A lineage that diverges early in the history of a group and lies on a branch near the common ancestor.

• Binomial: The two-part scientific naming system for species (genus and species), e.g., Homo sapiens.

• Branch Point: A node on a phylogenetic tree representing the divergence of two evolutionary lineages from a common ancestor.

• Clade: A group of species that includes an ancestral species and all its descendants (monophyletic group).

• Cladogram: A diagram depicting patterns of shared characteristics among species.

• Class, Domain, Genus, Kingdom, Order, Phylum: Hierarchical taxonomic ranks used in biological classification.

• Homoplasy: A trait shared by a set of species but not present in their common ancestor, often due to convergent evolution.

• Horizontal Gene Transfer: The movement of genetic material between organisms other than by descent from parent to offspring.

• Ingroup/Outgroup: In phylogenetic analysis, the ingroup is the group of interest, while the outgroup is a related group used for comparison.

• Maximum Parsimony: A principle that suggests the simplest explanation (fewest evolutionary changes) is preferred when constructing phylogenetic trees.

• Molecular Clock: A method that estimates the time of evolutionary divergence based on the rate of genetic mutations.

• Monophyletic, Paraphyletic, Polyphyletic: Terms describing groups based on their evolutionary relationships:

  • Monophyletic: Includes a common ancestor and all its descendants.

  • Paraphyletic: Includes a common ancestor and some, but not all, descendants.

  • Polyphyletic: Includes taxa with different ancestors.

• Polytomy: A branch point from which more than two descendant groups emerge.

• Rooted: A phylogenetic tree with a branch representing the most recent common ancestor of all taxa in the tree.

• Shared Ancestral Character: A trait that originated in an ancestor of the taxon.

• Shared Derived Character: A trait unique to a particular clade.

• Sister Taxa: Groups of organisms that share an immediate common ancestor.

• Systematics: The scientific study of the diversity and relationships among organisms.

• Taxon/Taxonomy: A taxon is a group of organisms at any level of classification; taxonomy is the science of naming and classifying organisms.

• Convergent/Divergent Evolution: Convergent evolution produces similar traits in unrelated lineages; divergent evolution leads to differences from a common ancestor.

Chapter 21: The Evolution of Populations

Mechanisms of Microevolution

This section explores the processes that cause changes in allele frequencies within populations.

• Adaptive Evolution: Evolution that results in a better match between organisms and their environment.

• Balancing Selection: Natural selection that maintains two or more phenotypic forms in a population.

• Bottleneck Effect: A sharp reduction in population size due to environmental events, leading to loss of genetic variation.

• Directional, Disruptive, Stabilizing Selection:

  • Directional Selection: Favors individuals at one end of the phenotypic range.

  • Disruptive Selection: Favors individuals at both extremes of the phenotypic range.

  • Stabilizing Selection: Favors intermediate variants and acts against extremes.

• Founder Effect: Genetic drift that occurs when a few individuals become isolated from a larger population.

• Frequency-Dependent Selection: The fitness of a phenotype depends on its frequency relative to other phenotypes.

• Gene Flow: The transfer of alleles between populations.

• Gene Pool: The total collection of genes in a population at any one time.

• Genetic Drift: Random changes in allele frequencies, especially in small populations.

• Hardy-Weinberg Equilibrium: The condition under which a population's allele and genotype frequencies remain constant in the absence of evolutionary forces. The equation is: where and are the frequencies of two alleles.

• Heterozygote Advantage: When heterozygous individuals have greater fitness than either homozygote.

• Microevolution: Evolutionary change within populations; change in allele frequencies over time.

• Neutral Variation: Genetic variation that does not provide a selective advantage or disadvantage.

• Population: A group of individuals of the same species living in the same area and interbreeding.

• Relative Fitness: The contribution an individual makes to the gene pool of the next generation relative to others.

• Sexual Dimorphism: Differences in secondary sexual characteristics between males and females.

• Sexual Selection: Natural selection for mating success.

Chapter 22: The Origin of Species

Speciation and Species Concepts

This section discusses how new species arise and the various concepts used to define a species.

• Allopatric Speciation: The formation of new species due to geographic isolation.

• Allopolyploid/Autopolyploid: Types of polyploidy; allopolyploid involves hybridization between species, autopolyploid involves chromosome duplication within a species.

• Biological Species Concept: Defines species as groups of interbreeding populations that are reproductively isolated from other groups.

• Ecological Species Concept: Defines species based on their ecological niche.

• Fusion: When two hybridizing species merge into one.

• Hybrid/Hybrid Zone: Hybrids are offspring of crosses between different species; a hybrid zone is a region where different species meet and mate.

• Macroevolution/Microevolution: Macroevolution refers to broad patterns of evolutionary change above the species level; microevolution is change within populations.

• Morphological Species Concept: Defines species by structural features.

• Phylogenetic Species Concept: Defines species as the smallest group of individuals sharing a common ancestor.

• Polyploidy: The presence of extra sets of chromosomes due to accidents during cell division.

• Postzygotic/Prezygotic Barriers: Barriers that prevent hybrid zygotes from developing into fertile adults (postzygotic) or prevent mating/fertilization (prezygotic).

• Punctuated Equilibria: The theory that species evolve rapidly during short periods, followed by long periods of stasis.

• Reinforcement: Strengthening of reproductive barriers in hybrid zones.

• Reproductive Isolation: The existence of biological factors that impede members of two species from interbreeding.

• Speciation: The process by which one species splits into two or more species.

• Species: The basic unit of biological classification.

• Stability: In hybrid zones, the continued production of hybrids.

Chapter 23: Broad Patterns of Evolution

Macroevolutionary Events and Developmental Genes

This section covers large-scale evolutionary changes and the genetic mechanisms underlying them.

• Adaptive Radiation: The rapid evolution of diversely adapted species from a common ancestor.

• Geologic Record: The history of Earth as recorded in rocks and fossils.

• Half-life: The time required for half the atoms of a radioactive isotope to decay.

• Heterochrony: Evolutionary change in the timing or rate of developmental events.

• Homeotic Gene: Genes that control the placement and organization of body parts.

• Macroevolution: Evolutionary change above the species level.

• Mass Extinction: A widespread and rapid decrease in the biodiversity on Earth.

• Paedomorphosis: The retention of juvenile features in the adult organism.

• Radiometric Dating: A method for determining the age of rocks and fossils based on the decay of radioactive isotopes. Example equation for radiometric dating: where is the number of remaining radioactive atoms, is the original number, is the decay constant, and is time.

• Permian Extinction: The largest mass extinction event, occurring about 252 million years ago.

• Cambrian Explosion: A period about 541 million years ago when most major animal phyla appeared in the fossil record.

Chapter 24: Early Life and the Diversification of Prokaryotes

Origin of Life and Prokaryotic Diversity

This section explores hypotheses about the origin of life and the diversity of prokaryotic life forms.

• Abiotic Synthesis: The formation of organic molecules from inorganic substances without life.

• Protocells: Simple, cell-like structures that may have been precursors to living cells.

• Self-replicating RNA: RNA molecules capable of replicating themselves, possibly the first genetic material.

• Fossil Record: The ordered array of fossils within layers of sedimentary rock.

• Stromatolites: Layered structures formed by the activities of prokaryotes, some of the oldest evidence of life.

• Peptidoglycan: A polymer forming the cell wall of most bacteria.

• Gram-positive/Gram-negative Bacteria: Classification based on cell wall structure and staining properties.

• Endospores: Resistant cells formed by some bacteria for survival in harsh conditions.

• Capsule: A sticky layer surrounding the cell wall of some bacteria.

• Fimbriae/Pili (Pilus): Hair-like appendages that help bacteria adhere to surfaces or exchange DNA.

• Nucleoid: The region in a prokaryotic cell where DNA is located.

• Heterocysts: Specialized cells in some cyanobacteria that carry out nitrogen fixation.

• Biofilms: Surface-coating colonies of prokaryotes.

• Metabolic Types:

  • Photoautotroph: Uses light as energy and CO2 as carbon source.

  • Chemoautotroph: Uses inorganic chemicals as energy and CO2 as carbon source.

  • Photoheterotroph: Uses light as energy and organic compounds as carbon source.

  • Chemoheterotroph: Uses organic compounds for both energy and carbon.

• Anaerobic Respiration: Respiration that does not require oxygen.

• Nitrogen Fixation: Conversion of atmospheric nitrogen (N2) to ammonia (NH3).

• Horizontal Gene Transfer: Movement of genes between organisms by means other than descent.

• Genetic Recombination: Exchange of genetic material between organisms.

• Transformation, Transduction, Conjugation: Mechanisms of genetic recombination in prokaryotes.

  • Transformation: Uptake of foreign DNA from the environment.

  • Transduction: Transfer of DNA by bacteriophages (viruses).

  • Conjugation: Direct transfer of DNA between two cells via a pilus.

• Plasmids: Small, circular DNA molecules in bacteria.

• F Plasmid: A plasmid that enables bacteria to form a pilus for conjugation.

• Antibiotic Resistance: The ability of bacteria to survive and multiply in the presence of antibiotics.

• Archaea: A domain of prokaryotes distinct from bacteria, often living in extreme environments.

• Halophiles, Thermophiles, Methanogens: Types of archaea adapted to high salt, high temperature, or methane-producing environments, respectively.

• Bacteria: One of the two domains of prokaryotic life.

• Cyanobacteria: Photosynthetic bacteria important for oxygen production.

• E. coli: A common model organism and member of the gut microbiota.

Chapter 25: The Origin and Diversification of Eukaryotes

Endosymbiosis and Eukaryotic Evolution

This section explains the origin of eukaryotic cells and the endosymbiont theory.

• Endosymbiont Theory: The hypothesis that mitochondria and plastids (e.g., chloroplasts) originated as prokaryotic cells engulfed by a host cell, leading to a symbiotic relationship.

• Endosymbiosis: A relationship in which one organism lives inside the cell or cells of another organism.

Chapter 27: The Rise of Animal Diversity

Animal Evolution and Body Plans

This section discusses the evidence for animal evolution and the diversity of animal body plans.

• Fossil Evidence: Fossils provide insight into the early evolution of animals.

• Molecular Evidence: DNA and protein sequence comparisons reveal evolutionary relationships among animals.

• Cnidarians: A phylum of animals including jellyfish, corals, and sea anemones, characterized by radial symmetry.

• Cambrian Explosion: A period of rapid animal diversification about 541 million years ago.

• Bilaterians: Animals with bilateral symmetry and three germ layers.

• Body Plans: The basic structural and developmental characteristics of animals.

• Radial Symmetry: Symmetry around a central axis, as in a starfish or jellyfish.

• Bilateral Symmetry: Symmetry with a single plane dividing the body into left and right halves.

• Endoderm, Mesoderm, Ectoderm: The three primary germ layers in animal embryos:

  • Endoderm: Innermost layer, forms the gut lining.

  • Mesoderm: Middle layer, forms muscles and organs.

  • Ectoderm: Outermost layer, forms skin and nervous system.

• Invertebrate: Animals without a backbone.

• Vertebrate: Animals with a backbone.

Additional info: These notes are based on a list of key terms from BIO 101 modules covering evolution, phylogeny, population genetics, speciation, macroevolution, the origin of life, prokaryotic diversity, eukaryotic origins, and animal diversity. Where only terms were provided, academic definitions and context have been added for clarity and completeness.