Biological Evolution and Theories

Biological Evolution

• Biological evolution is the process of organisms changing over generations through variations in traits and natural selection.
• Non-evolutionary changes are not genetic, resulting from short-term environmental changes.

Theory of Common Descent

• All living organisms share a common ancestor.
• Phylogenetic trees illustrate evolutionary relationships between species.
• Branches represent evolutionary changes.
• Branch points indicate common ancestors.

Darwin's Theory of Evolution

• Influences:
  • Collection of diverse animals and plants
  • Principles of Geology
  • Divergence between island organisms and mainland species
• The Linnaean system categorizes organisms based on shared traits and evolutionary relationships, revealing common ancestry.

Linnaean System

• Domain: Eukarya
• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Primates
• Family: Hominidae
• Genus: Homo
• Species: Homo sapiens

Anatomical Homology

• Similarities in skeletal structures.

Convergent Evolution

• Structural similarities in unrelated species due to similar lifestyles.

Vestigial Traits

• Non-functional or greatly reduced traits.

Developmental Homologies

• Similarities in developmental processes from fertilized egg to adulthood.

Molecular Homologies

• Similarities in DNA sequences.
• Embryonic development

Biogeography

• Distribution of species on Earth.

Fossil Record

• Radiometric dating:
  • Estimating the age of rocks using ratios of radioactive elements.
  • Direct evidence of change in organisms over time.

Why is Evolution a Good Explanation?

• Good explanation of a wide variety of observations. Well-supported by a wide variety of evidence.
• Anatomy, geology, molecular biology and genetics provide evidence.
• Consilience - agreement among observations from various sources.

Chapter 12: Natural Selection

• Use the Natural Selection Worksheet

Chapter 13: Biological Species

• A group of individuals that can interbreed and produce fertile offspring but cannot reproduce with members of other species.

Reproductive Isolation

• Prevents gene flow between species
• Pre-zygotic barriers:
  • Spatial isolation
  • Behavioral isolation
  • Mechanical isolation
  • Temporal isolation
• Post-zygotic barriers:
  • Gamete incompatibility
  • Hybrid inviability
  • Hybrid sterility

Speciation

• Three steps of speciation:
  • Isolation of gene pools
  • Evolutionary changes in gene pools
  • Evolution of reproductive isolation.

Races

• Race as defined using the geological species concept - organisms able to interbreed- descended from a common ancestor, representing independent evolutionary lineage.

Humans' African Origin

• Humans have less genetic diversity than any other great ape which suggests a relatively young species.
• African populations have the greatest genetic diversity, indicating the oldest human population.

Genetic Evidence of Race

• Allele frequencies: The percentage of gene copies of a specific allele in a particular population.
• Human races are not isolated.
• More variations exist within groups than between groups.

Traits Due to Natural Selection

• Traits that have become common due to natural selection in specific populations such as skin, sickle cell, and nose shape.

Genetic Drift

• Changes in allele frequency due to chance.
  • Examples: Founder effect and bottleneck effect.

Sexual Selection

• When a trait influences the likelihood of mating.

Chapter 14

• Estimated number of species: 1.3 million (estimate).
• Only about 20% of species are known.
• Three major domains: Bacteria, Archaea, Eukarya.
• Broad overview of life's history: Prokaryotes evolved into more complex eukaryotes.

Prokaryotes

• Found anywhere and able to resist extreme conditions.
• Endospores allow some to survive.

Endosymbiotic Theory

• Mitochondria and chloroplasts descended from bacteria inside primitive eukaryotes.

Four Kingdoms of Eukarya

• Protista (mostly single-celled).

Resembling life forms: Animals, fungi, and plants.

• Most members are unknown. Some are photosynthetic (algae). Others consume cellulose/ organic molecules.

Animalia

• Vertebrates and invertebrates. Eukaryotic and multicellular, heterotrophic.

Fungi

• Immobile and Multicellular. Heterotrophic and decomposers. Examples include spores, yeast, and molds.

Plantae

• Multicellular and eukaryotic. Autotrophic. Include first plants, flowering/nonflowering plants.

Adaptive Radiation

• Rapid diversification of species into a large group of descendants, often due to evolutionary breakthroughs or the extinction of competing species.

Viruses

• Not considered living organisms because they cannot maintain homeostasis and require assistance for reproduction and growth.

Evolutionary Classifications

• Phylogeny: Evolutionary relationships
• Cladistic analysis: Technique to examine variation in related species
• Fossil examination and DNA provide verification.