Life Keeps Evolving

Life Keeps Evolving

  • 3.5 Lectures

Evolution of Eukaryotes

  • Learning Objectives:

    • Measure cell and organelle size using a ruler and a scale bar.

    • Distinguish between images and descriptions of prokaryotes and eukaryotes.

    • Summarize the data that supports the theory of endosymbiosis.

The Three Domains

  • Identify organisms similar to those discussed in previous lectures and readings.

Cell Types

  • Prokaryotic Images:

    • Panel 1: Scanning electron micrographs showing Streptococcus and a spirochete.

    • Panel 2: Contains an Archaea and a methanogen.

  • Eukaryotic Images (Panel 3 Clockwise):

    • Scenedesmus (green alga)

    • Aspergillus fumigatus (fungal fruiting body)

    • Mosquito

    • Rabbit

Tree of Life

  • Archaea and bacteria are both prokaryotes.

  • The third domain is eukarya, consisting of various organisms.

Structure of Eukaryotes

  • Explore cell structure differences between eukaryotes and other domains.

Cell Comparison Methodology

  • Gather information about organisms to determine potential relationships.

Scale Bar Utilization

  • Learn to measure cell length using scale bars:

    1. Identify scale bar and its corresponding value (e.g., 4μ).

    2. Count how many scale bars fit across the cell.

    3. Calculate cell length (e.g., 3 bars x 4μ = 12μ).

Microns

  • Definition: A micron is 1/1000th (0.001) of a millimeter, also known as a micrometer.

  • Conversions:

    • 1 micron = 1000 nanometers.

Organisms Sizes

  • Cell Comparison Sheet:

    • Fill out specifics including the size in microns and organelle presence of various organisms:

      • Euglena (flagellated protist)

      • E. coli (intestinal bacteria)

      • Candida (yeast, fungus)

      • Cyanobacterium (photosynthetic bacterium)

Organelles

  • Panel B & D are prokaryotes; A & C are eukaryotes.

  • Eukaryotes contain nuclei and have larger sizes with organelles.

Differences Between Prokaryotes and Eukaryotes

  • Note key differences in cell structure on Part B assignment.

Homework

  • Complete Part C and submit via D2L.

Additional Exploration

  • Discuss the identification of prokaryote vs. eukaryote cells based on images and reasoning.

Endosymbiosis Theory

  • Objective: Understand how eukaryotic cells evolved via endosymbiotic relationships.

  • Organelles like chloroplasts and mitochondria were once free-living bacteria that became integral to host cells.

    • Differences noted from free-living forms to organelles: inability to survive outside host cell.

Chloroplast and Mitochondrial Functions

  • Similarities in function:

    • Chloroplasts harness sunlight energy (similar to cyanobacteria).

    • Mitochondria extract energy from nutrients (similar to aerobic bacteria).

Evolutionary Implications

  • Comparative analysis of RNA among chloroplasts, mitochondria, and bacteria supports endosymbiosis theory.

Assignment Expectations

  • Complete Organelle Comparison Sheet, reply to questions regarding chloroplast and mitochondria.

    • Understanding similarities and differentiated evolutionary paths informs cellular function.

Multicellular Life Learning Objectives

  • Compare and contrast single-celled and multicelled organisms; identify advantages and disadvantages.

Evolution of Multicellularity

  • Approximately 1 billion years ago, multicellular life forms emerged; experimental hypotheses explore this transition.

Environmental Pressures and Group Living

  • Examine interactions in cultures, observing behaviors when predatory pressures arise.

Observations and Hypotheses from Experiments

  • Track changes in algal populations (Chlorella and Ochromonas) under predatory threats—clumping offers survival advantages.

Academic Reflection on Eukaryote Evolution

  • Discuss ancestral forms as potential early multicellularity indicators.

Definitions Related to Multicellularity

  • Compile definitions of terms like single-celled, multicelled, colony, cooperation, and specialization as part of learning goals.

Part III – Evolution of Multicelled Life

  • Organize notes on the evolutionary advantages of multicellularity.

Nutrient Acquisition in Cells

  • Contrast nutrient movement effectiveness between large and small cells.

Pyramid of Life

  • Categorize life forms based on biomass constituents (multicellular vs. single-celled organisms).

Cell Lifecycle Insights

  • Understand interphase and mitosis in eukaryotic cell cycles.

    • Note that cells spend approximately 90% of their life in interphase, with actively dividing cells being a small percentage.

Mitosis Explained

  • Define mitosis as the cellular process of forming two identical nuclei before cell division.

Sexual Reproduction Process

  • Understand that sexual reproduction involves combining two gametes, each with half the chromosomes, to form a zygote.

Meiosis Overview

  • Distinguish meiosis from mitosis; gametes carry half chromosomes for the organism (e.g., human gametes carry 23 chromosomes).

Genetic Variation Role in Evolution

  • Explore how genetic recombination offers diversity that allows populations to adapt, survive and reproduce, emphasizing natural selection mechanisms.

Final Thoughts on Lecture Content

  • Review how unique traits arise even in siblings, connecting concepts of chromosomes, DNA, and meiosis.

Conclusion and Homework Assignment

  • Submit assignments related to cell division, study for mid-term, and construct concept maps relating to living organisms.