Review for General Biology II – Lecture Exam I

This set of flashcards covers key terms and concepts from the lecture notes on the origin of species, phylogeny, the history of life on Earth, prokaryotes, and eukaryotic diversity.

How do new species form?

New species form through reproductive isolation combined with evolutionary mechanisms such as natural selection, mutation, genetic drift, and sexual selection.

Prezygotic vs. Postzygotic Barriers

1. Prezygotic barriers: Prevent mating or fertilization (e.g., habitat, temporal, behavioral, mechanical, and gametic isolation).
2. Postzygotic barriers: Reduce the success of the hybrid offspring (e.g., reduced viability, reduced fertility, and hybrid breakdown).

What are the four major species concepts?

• Biological: Defined by reproductive compatibility (cannot apply to fossils/asexual organisms).
• Morphological: Defined by physical traits.
• Ecological: Defined by ecological niche.
• Phylogenetic: Defined as the smallest monophyletic group on a phylogenetic tree.

Allopatric vs. Sympatric Speciation

• Allopatric speciation: Occurs when populations are geographically separated.
• Sympatric speciation: Occurs without geographic separation, often driven by polyploidy (in plants), habitat differentiation, or sexual selection.

Outcomes of Hybrid Zones

1. Reinforcement: Hybrids have low fitness; reproductive barriers strengthen.
2. Fusion: Hybrids are fit; barriers weaken and species merge.
3. Stability: Hybrids persist, but parent species remain distinct.

Gradualism vs. Punctuated Equilibrium

• Gradualism: Suggests slow, continuous evolutionary change over long periods.
• Punctuated Equilibrium: Suggests long periods of stasis interrupted by sudden, rapid bursts of speciation.

Fundamental vs. Realized Niche

• Fundamental Niche: The full potential range of environmental conditions and resources a species could theoretically occupy.
• Realized Niche: The actual range a species occupies due to limiting factors like competition or predation.

Competitive Exclusion Principle

The principle stating that two species with identical niches cannot coexist indefinitely; one will eventually outcompete the other for resources.

Stages of the Origin of Life

1. Abiotic synthesis of organic monomers.
2. Formation of organic polymers.
3. Packaging into protocells.
4. Origin of self-replicating RNA systems (the 'RNA World').

Key Events in the History of Life

• \approx 3.5 billion years ago: First prokaryotic cells.
• Oxygenation: Caused by the origin of photosynthesis.
• Cambrian Explosion: A sudden increase in animal diversity.
• Mass Extinctions: Events that eliminate large portions of global biodiversity, often followed by adaptive radiation.

Homology vs. Analogy

• Homologous traits: Phenotypic and genetic similarities due to shared ancestry.
• Analogous traits: Similarities due to convergent evolution in response to similar environmental pressures, not shared ancestry.

Monophyletic vs. Paraphyletic vs. Polyphyletic

• Monophyletic: A common ancestor and all of its descendants (a clade).
• Paraphyletic: A common ancestor and some, but not all, descendants.
• Polyphyletic: Distantly related species but does not include their most recent common ancestor.

Gram-Positive vs. Gram-Negative Bacteria

• Gram-positive: Thick peptidoglycan cell walls; usually stain purple.
• Gram-negative: Thin peptidoglycan layer and an outer membrane; often more resistant to antibiotics; usually stain pink/red.

Prokaryotic Genetic Recombination

1. Transformation: Uptake of foreign DNA from the environment.
2. Transduction: Movement of genes between bacteria via bacteriophages (viruses).
3. Conjugation: Direct transfer of DNA between two cells via a pilus.

Endosymbiosis Theory

The theory that mitochondria and plastids (chloroplasts) originated as free-living prokaryotes that were engulfed by a host cell and eventually evolved into organelles.

Photic vs. Aphotic Zones

• Photic Zone: The upper layer of water where there is sufficient light for photosynthesis.
• Aphotic Zone: The deeper layer where little to no light penetrates, limiting primary productivity.