Exam 2 Review Notes

Exam 2 Review Notes

Major Events in Each Era

• Precambrian Era: Formation of Earth, development of early life (prokaryotes), first multicellular organisms.

Key Concepts to Understand

• Macroevolution: Large-scale evolutionary changes; significant divergence in species.
• Gradualism: Evolutionary change occurs slowly over long periods; issues include its inability to account for sudden changes.
• Punctuated Equilibrium: Evolution characterized by long periods of stability followed by rapid changes; issues include lack of fossil evidence for transitions.
• Adaptive Radiation: Rapid diversification of species to fill different ecological niches; often occurs after mass extinctions.
• Allopatric Speciation: Species formation due to geographic separation.
• Sympatric Speciation: Species formation in the same geographic area through reproductive isolation.
• Inbreeding: Mating among closely related individuals; issues include increased vulnerability to diseases.

Adaptive Radiation

• Definition: Evolution of numerous species from a common ancestor in new ecological niches.
• Often occurs after events such as mass extinctions, allowing for rapid adaptation and diversification.

Origins of Organic Chemicals

• Abiogenesis Theories: 1. Primordial soup hypothesis (energy sources, e.g., lightning). 2. Iron-sulfur world hypothesis (hydrothermal vents). 3. Extraterrestrial origins (panspermia).

Thought Process for First Genetic Material

• Likely candidates: RNA due to its ability to store genetic information and act as a catalyst (ribozymes).
• Issues include instability and how RNA could self-replicate.

Stages of Developing First Life

1. Formation of simple organic molecules.
2. Formation of complex molecules (proteins, nucleic acids).
3. Aggregation of molecules into protocells.
4. Development of self-replicating systems.

Oxygen in Our Atmosphere

• Responsible Factors: Photosynthetic organisms (cyanobacteria) produced oxygen as a by-product of photosynthesis.

Endosymbiont Theory

• Explanation of the origin of eukaryotic cells from prokaryotic organisms through symbiosis (e.g., mitochondria and chloroplasts).

Hominids Discussed

• Key species included: Neanderthals, Homo sapiens, Homo habilis, etc.

Out of Africa Hypothesis and mtDNA

• Hypothesis that modern humans originated in Africa and migrated outwards.
• mtDNA is used to trace maternal lineage and understand human evolutionary history.

Biomes Discussed

• Notable examples: tropical rainforests, deserts, tundras, grasslands, etc.; factors influencing each biome include climate, soil type, and vegetation.

Thermocline and Turnover

• Thermocline: Layer in water where temperature changes sharply; critical for aquatic ecosystems.
• Turnover: Seasonal mixing of water layers; influenced by temperature and wind; prevents stagnation.

Distribution of Biomass

• Most biomass exists primarily in producers (plants, phytoplankton) within ecosystems; forms the foundation of food webs.

Key Population Concepts

• Population Density: Number of individuals per unit area.
• Immigration/Emigration: Movement in and out of populations, impacting density.
• Boom and Bust Cycles: Rapid population increases followed by sharp declines.
• Life Expectancy: Average lifespan of individuals within a population.
• Ecological Footprint: Impact of individual/group on the environment.
• Altricial vs. Precocial: Altricial species are born immature, needing care (e.g., most birds), while precocial species are more developed at birth (e.g., deer).

Distribution Patterns

• Clumped: Individuals grouped in patches (e.g., social species).
• Uniform: Evenly spaced, often due to territoriality.
• Random: Unpredictable spacing, often due to environmental factors.

Population Growth Types

• Exponential Growth: Growth without constraints; assumes unlimited resources, ideal conditions.
• Logistic Growth: Growth that levels off as carrying capacity is reached; includes limiting factors.
• Boom-and-Bust Growth: Cycles of rapid growth and sharp declines due to resource limitations.

Population Density Regulation

• Factors include resource availability, predation, disease, and competition; can shift populations to stable states.

Survivorship Curves

• Type I: High survival in early/middle life, high mortality in older age.
• Type II: Constant mortality rate throughout life.
• Type III: High mortality in early life, low mortality for survivors.

Interspecific Interactions

• Relationships between different species, including predation, competition, parasitism, and mutualism.

Keystone Species

• A species that has a disproportionate effect on its environment relative to its abundance (e.g., sea otters, wolves).

Ecological Succession

• Process of change in species structure over time in a community following disturbance.

Intermediate Disturbance Hypothesis

• Moderately disturbed ecosystems tend to have higher biodiversity; prevents dominance by a few species.

Predator/Prey Adaptations

• Evolving traits that enhance survival for predators (e.g., speed) and for prey (e.g., camouflage).

Factors Correlating with Biodiversity

• Habitat Diversity and Climate Stability in an environment;

Trophic Levels Calculation (10% Rule)

• Only 10% of energy at one trophic level is available to the next. Example: if producers have 1000 kcal, primary consumers receive 100 kcal.

Competitive Exclusion Principle

• Two species competing for the same resource cannot coexist indefinitely; leads to niche differentiation or extinction of one species.