Science Practice Challenge Questions

4.3 Eukaryotic Cells


Describe structural and functional similarities between mitochondria and chloroplasts that provide evidence of common ancestry.


Explain how the structural and functional differences between mitochondria and chloroplasts provide evidence of adaptations among common ancestral organisms.


Examine the differences and similarities in the structural features of animal and plant cells. Justify the claim that both animals and plants have common ancestors based on your observations.


What conserved core processes are common to both animals and plants? Construct an explanation of the differences based on the selective advantages provided in different environments.

4.6 Connections Between Cells and Cellular Activities


Louis Sullivan described architectural design as “form follows function.” For example, a window is designed to add light to a space without heat transport. A door is designed to allow access to a space. Windows and doors have different functions and so take different forms. Biological systems are not designed, but selected from random trials by interaction with the environment. Apply Sullivan’s principle to explain the relationship of function and form for each pair of cellular structures below.

  1. Plasma membrane and endoplasmic reticulum
  2. Mitochondrion and chloroplast
  3. Rough endoplasmic reticulum and smooth endoplasmic reticulum
  4. Flagella and cilia
  5. Muscle cells and secretory cells

Complex multicellular organisms share nutrients and resources, and their cells communicate with each other. A society may encourage cooperation among individuals while discouraging selfish behavior to increase the overall success of the social system, sometimes at the expense of the individual. Scientific questions are testable and often attempt to reveal a mechanism responsible for a phenomenon. Pose three questions that can be used to examine the ways in which a social system regulates itself. Be prepared to share these in small group discussions with your classmates about the similarities between these regulatory strategies and the analogous roles of plasmodesmata and gap junctions in cell communication.


Plasmodesmata in vascular plants and gap junctions in animals are examples of specialized features of cells. Mechanisms by which transport occurs between cells evolved independently within several eukaryotic clades. Explain, in terms of cellular cooperation, the selective advantages provided by such structures.


Mammalian red blood cells have no nuclei, must originate in other tissue systems, are relatively long-lived, are small with shapes that actively respond to their environment, and are metabolic anaerobes. Other vertebrates have red blood cells that are usually nucleated and are often relatively large, aerobic, self-replicating, and short-lived.

To connect these facts to biology, questions need to be asked. The questions that you pose will depend on the path your class is taking through the curriculum. Begin by summarizing what you know:

  • What are the functions of a eukaryotic cell nucleus?
  • What is the approximate average size of a human red blood cell?
  • What is the range of blood vessel diameters in adult humans?
  • What is the range of red blood cell size in vertebrates?
  • What is the average lifetime of a human red blood cell?
  • How can you show how cell production is stimulated using examples from particular systems?
  • How is cell death controlled?
  • What biochemical cycles are associated with anaerobic and aerobic respiration, and what are the important differences between these?
  • What process is involved in the transport of oxygen and carbon dioxide into and out of red blood cells?
  • What behaviors and dynamic homeostatic processes might be associated with the properties of red blood cells in mammalian and nonmammalian organisms?
  • What do you know about the evolutionary divergences among vertebrates?

Your summary has revealed some similarities and differences among vertebrate erythrocyte and circulatory system structures. Scientific questions are testable. They can be addressed by making observations and measurements and analyzing the resulting data.

  1. Pose three scientific questions that arise from your summaries of what you know about erythrocytes and capillary size.
  2. For each question you pose, predict what you believe would be the answer and provide reasoning for your prediction.
  3. Describe an approach you think can be used to obtain data to test your prediction.
  4. In the production of mammalian red blood cells, erythrocytes that have not yet matured and are still synthesizing heme proteins are surrounded by a macrophage. Predict the role of the macrophage in the maturation of a red blood cell.

Mitochondria have DNA that encode proteins related to the structures and functions of the organelles. The replication appears to occur continuously, however, many questions about control of replication rate and segregation during mitosis are yet unanswered. Many diseases are caused by mitochondrial dysfunction. Mitophagy, as the name suggests, leads to the destruction of mitochondria. Predict whether or not cellular control mechanisms involving the regulation of mitochondrial DNA by the nucleus exist. Make use of what you know about selection and homeostasis as they apply to both the organism and to the organelle.