Macroevolution: The Long Run Study Notes

Chapter 14: Macroevolution – The Long Run

Introduction

• Faith Hall introduces herself as the SI leader for the course SI BIOL 214.

• Description of personal background: junior biology major with a minor in psychology; previously taken the course, achieving an A.

• Reference to course materials and session times.

Learning Objectives

• Students should be able to:

  • Compare and contrast macroevolution and microevolution processes.

  • Compare and contrast the evolutionary patterns resulting from macroevolution and microevolution.

  • Evaluate the impact of varying origination and extinction rates on species diversity.

  • List evidence necessary to differentiate between dispersal events and vicariance events in fossils.

  • Describe methods used by paleontologists to analyze the fossil record for macroevolutionary patterns.

  • Explain factors leading to adaptive radiations.

  • Distinguish background extinctions from mass extinctions.

  • Assess human influences on biotic and abiotic biodiversity factors.

  • Discuss the potential for human-induced mass extinction.

Biodiversity Statistics

• Approximately 1.8 million described species.

• Stork (2018) estimates:

  • 1.5 million beetle species.

  • 5.5 million insect species.

  • 7 million arthropod species.

• Linnaeus mentioned more than 10,000 plant species in the 18th century, with a current estimate of ~374,000 plant species.

Microevolution vs. Macroevolution

• Microevolution:

  • Evolution within populations.

  • Involves adaptive and neutral changes in allele frequencies.

• Macroevolution:

  • Evolution above the species level.

  • Involves species origination, diversification, and extinction over time.

Patterns of Vertebrate Diversity

• Species diversity follows a gradient from polar to temperate to tropics, noted as the latitudinal species richness gradient.

• Specific reference: North American avian species richness follows a polar-equatorial gradient.

Species Richness Patterns

• Latitudinal species richness gradient explains:

  • Most taxa show increased species numbers from polar to temperate to tropical regions.

• Possible explanations for high species diversity in tropics include:

  • Species-time hypothesis: Communities diversify (gain species) with time; temperate regions are younger post-glaciation.

  • Species-area hypothesis: Larger areas support larger, diverse populations and habitats.

  • Species-energy hypothesis: Energy availability (solar and water) drives higher productivity, leading to diverse herbivores and subsequently diverse predators and parasites.

Biogeography

• Definition: Study of distribution of species across space and time.

• Areas of high and low species richness mentioned.

Dispersal and Vicariance

• Dispersal: Movement of populations with minimal return.

• Vicariance: Formation of barriers that divide a previously continuous population, causing distinct phylogenetic signatures.

Implications of Climate on Diversity

• Overview of extinction dynamics throughout Earth's history; background extinctions vs mass extinctions.

• Human emissions impacting biodiversity and global energy budgets.

• Data on coral species diversity showing disparity between tropical Pacific and Atlantic regions.

Rate of Extinction and Speciation

• Formula depicting diversity change: $D1 + originations - extinctions = D2$.

• Definitions:

  • Fauna: Animal species assembly in a defined area.

  • Flora: Plant species assembly in a defined area.

• Analysis of origination ( = origination rate) and extinction ( = extinction rate) rates in indicating biodiversity changes.

Historical Patterns of Extinction

• Discussion on the five mass extinctions and associated causes.

• Cretaceous-Tertiary (K-T) boundary event linked to extraterrestrial impacts involving iridium levels.

• Overview includes the extinction of vertebrates with historical examples, especially focusing on human-induced extinctions, such as tigers and the Carolina Parakeet.

Behavioral Trends in Extinction Rates

• Charting different taxa extinction rates over time: mammals, birds, reptiles, amphibians, and fish.

• Correlation with anthropogenic effects.

Ecology and Evolution

• Gradient analysis of taxa diversity in context to temperature changes over geological periods.

• Unified understanding of anagenesis vs. punctuated equilibrium, with associated conditions leading to adaptive radiations in various taxa.

Final Insights on Extinctions

• Mass extinction events can profoundly affect ecological interactions, leading to cascading effects throughout ecosystems and affecting species survival rates.

Key Concepts Summarized

1. Biogeography describes species distribution influenced by geography and historical events.

2. Species origination and extinction rates critically inform evolutionary histories.

3. Fossil records can illustrate speciation events and extinction occurrences.

4. Major extinction events generally stem from substantial environmental shifts or catastrophic occurrences.

5. Adaptive radiations often yield numerous new species, notably facilitated by key evolutionary innovations.

Details and Scientific Evidence

Include numerical data, charts, and specific hypotheses associated with the Cambrian explosion and extinction events.
In-depth examination of taxa evolution across timeframes highlighting significance of geological changes on biodiversity.