Ch 25: Origin & Diversification of Eukaryotes

Question 1

Explain how the structural components of eukaryotic cells are more diverse and specialized than prokaryotic cells and connect it to the function of these cells

Answer 1

• Nucleus /DNA
• Other membrane-enclosed organelles:
  
  • Mitochondria
  • Golgi apparatus
    
    • specific locations for specific functions, novel metabolic capabilities
• Cytoskeleton
  
  • structural support & asymmetrical forms
    
    • Change shape to feed, move or grow

Question 2

Compare and contrast the defining characteristics of the three domains of life

Answer 2

Bacteria have no nucleus in their cells.Archaea have a distinct cell wall than bacteria and do not have a nucleus.Eukaryotes: cells have a nucleus.

Question 3

Explain the endosymbiotic theory for the origins and unique characteristics of eukaryotes

Answer 3

• DNA sequence data suggest that eukaryotes are “combination” organisms, with some of their genes and cellular characteristics being derived from archaea, and others from bacteria.
• Endosymbiosis theory: Holds that mitochondria and plastids (a general term for chloroplasts and related organelles) were formerly small bacteria that began living within larger cells. According to this hypothesis, the defining moment in the origin of eukaryotes occurred when an archaeal cell (or a cell that was closely related to the archaea) engulfed a bacterium that would later become an organelle found in all eukaryotes—the mitochondrion.

Question 4

What selective pressures favored the evolution of multicellularity?

Answer 4

• Protection: multicellularity helps organisms avoid being eaten
• Stability in the fluid environment: multicellular organisms may be better able to maintain their position on a surface or in the water column
• Feeding opportunities: multicellularity may enhance feeding opportunities

Question 5

What is Simple Multicellularity?

Answer 5

• Simple multicellularity:
  
  • Organisms are composed of multiple similar cells
  • Cell adhesion, but little cell differentiation
  • Little communication or transfer of resources between cells
  • Prominent in algae

Question 6

What is Complex Multicellularity?

Answer 6

• Complex Multicellularity
  
  • Highly developed molecular mechanisms for adhesion between cells
  • Specialized structures that allow cells to communicate
  • Complex patterns of cellular and tissue differentiation, guided by networks of regulatory genes

Question 7

How is simple multicellularity different from complex multicellularity?

Answer 7

Simple multicellularity involves the adhesion of cells with little cell differentiation. Complex multicellularity involves cell adhesion, cell signaling, and differentiation and specialization among cells.

Question 8

What 3 features characterize complex multicellular organisms? Why are these features essential for complex multicellularity?

Answer 8

• Adhesion Between Cells: Animals use cadherins, integrins and additional transmembrane proteins for adhesion
• Communication Between Cells: Communication is essential for guiding gene expression during development/cellular differentiation and for the functional integration of cells within tissues and tissues within organs.
• Genetic Program for Coordinated Growth and Cell Differentiation: All cells in the human body are derived from a single fertilized egg, and most contain the same DNA; Complex multicellular organisms differentiate into multiple cell types in space

Question 9

According to the phylogenetic tree of eukaryotes do all multicellular eukaryotes share a common multicellular ancestor?

Answer 9

All true animals—members of the kingdom Animalia—are eukaryotic multicellular organisms that share a single common evolutionary ancestor

Question 10

NOTES

Answer 10

• Protists are simple eukaryotic organisms that are neither plants nor animals or fungi. They are the largest eukaryotic group.
• The green algae (Charophytes) are believed to share a common ancestor with plants becausetheir chloroplasts are similar in structure and pigment composition to those of plants.
• The termmixotrophindicates that an organism can be both heterotrophic and autotrophic.