Lecture 14

Announcements

  • Midterm Survey

    • 5 points extra credit
    • Due by 11:59 PM, Friday, March 14
    • Submission via the Quizzes tab in Canvas

  • Extra Credit Seminar

    • Speaker: Dr. Crystal Reynaga, UCR
    • Title: From Tendons to Terrain
    • Date & Time: March 13, 4 PM - 5 PM, via Zoom
    • Seminar will be recorded; general notes required for forthcoming assignment.
Seminar Series Details
  • Speaker Information:
    • Crystal Reynaga, PhD
    • Assistant Professor, Department of Evolution, Ecology, & Organismal Biology, UCR
  • Research Focus:
    • Integrative systems biology exploring animal locomotion across multiple scales: neuro-muscular control, musculotendinous mechanics, and performance.
  • Upcoming Dates: March 13, 2025, 4:00 PM
    • Zoom Meeting ID: 817 8028 2041
    • For more information, contact Dr. Houng-Wei Tsai at houng-wei.tsai@csulb.edu.
CSULB Animal Museum Events
  • Guided Animal Drawing Workshops
    • Location: Hall of Science, Room 074
    • Dates:
    • 02/28 - Big Skulls
    • 03/14 - Birds & Wings
    • 04/11 - Fur
    • Time: 1 PM - 3 PM
    • All skill levels & majors welcome. BYO materials.
    • Limited space; RSVP at kelly.hood@csulb.edu.
Upcoming Research Experience
  • CSULB/Catalina Island Conservancy Summer Research Experience
  • Dates: July 13 - 26, 2025
Office Hours & Exam Preparation
  • Students encouraged to attend office hours or schedule appointments to discuss Exam 2.
  • Familiarize with vocabulary lists and study questions at the end of each PPT.
Today's Goals
  1. Species Diversity: The balance between speciation and extinction.
  2. Origin and Loss of Complex Traits.
Species Diversity: Extinction vs. Speciation
  • Clade species numbers are influenced by a balance between:
    • Speciation Rate: Rate at which new species originate.
    • Extinction Rate: Rate at which species go extinct.
  • Example: Although speciation rates in two clades may be similar, extinction rates in clade A are significantly higher.
Species Diversity: Mass Extinction
  • Extinction is normal but can spike into mass extinctions.
  • Major Events:
    • Five major mass extinction events in the past 500 million years.
    • Important examples include:
    1. End-Permian: 251 million years ago; extinction of 96% of marine species.
    2. End-Cretaceous: 65 million years ago; >50% extinction, including dinosaurs.
End-Permian Mass Extinction (251 mya)
  • Caused by tectonic activities leading to:
    • Formation of Pangaea & massive volcanic eruptions.
    • Results: Increased CO2, climate warming, ocean acidification leading to anoxic waters and further species loss.
End-Cretaceous Mass Extinction (65 mya)
  • Caused by asteroid impact resulting in:
    • Climate cooling due to debris blocking sunlight, leading to an "impact winter" and failure of photosynthesis in plants.
Adaptive Radiation
  • Concept of speciation occurring at low rates interrupted by rapid adaptive radiations.
    • Defined as the rapid increase in species diversity driven by adaptation to different environments.
  • After Mass Extinctions: Provides ecological niches for diversification, as in the case of Hawaiian silverswords that adapted to various habitats after colonizing the islands.
Key Innovations Leading to Radiations
  • Radiations occur when lineages evolve significant traits enabling habitat invasion (e.g., plants with seeds and waxy cuticles migrated to land).
The Origin of Complex Traits
  • Evolution does not inherently favor complexity; simpler phenotypes can thrive.
  • Examples of simplifications:
    • Some insects lose wings; some reptiles lose limbs.
    • Buddenbrockia: A simplified parasitic worm former jellyfish losing characteristics through evolution.
Evolution of Complex Adaptations
  • Complex traits can evolve via natural selection on heritable phenotypic variations.
  • Incremental Steps: Complex traits often develop through identifiable intermediate states, such as in the evolution of mollusc eyes from simple light detection to complex focus capabilities.
Essential Vocabulary
  • Mass Extinction: A sharp increase in extinction rates.
  • Evolutionary Radiation: Rapid increase in species numbers, can be contextually general.
  • Adaptive Radiation: Rapid diversification usually following new environmental opportunities.
  • Key Innovation: Trait that significantly enhances survival and reproduction potentially leading to diversification.
Study Questions
  1. When did the end-Permian and end-Cretaceous mass extinctions occur? What were their effects and potential causes?
  2. How do current extinction rates compare to historical rates?
  3. What is the difference between "evolutionary radiation" and "adaptive radiation"?
  4. What conditions typically lead to evolutionary radiations?