Learning Outcomes:
i. Students will outline the historical development of biological classification.
ii. They will understand the characteristics of the Two Kingdom and Three Kingdom systems of classification.
iii. Students will be able to compare these systems based on distinct criteria.
Summary of Lesson:
The way we sort life forms into groups has changed a lot as scientists have discovered more about the variety of life. We started with just two groups but realized we needed more to really show all the differences. This lesson will guide you through this history and help you understand how these systems compare.
i. The Two Kingdom System:
The journey begins with Linnaeus's Two Kingdom system, where all living things were sorted as either plants (Plantae) or animals (Animalia), mainly based on their ability to move and their obvious physical traits.
ii. The Three Kingdom System:
As technology like microscopes got better, scientists saw tiny organisms that didn't fit as plants or animals. Ernst Haeckel proposed adding a new kingdom for these odd ones out: Protista.
iii. Advancing to the Five Kingdom System:
With even more discoveries, scientists expanded to five kingdoms to make room for all the different types of life, especially once they realized some organisms were really different, like the bacteria in the Monera kingdom.
Comparison of Two Kingdom and Three Kingdom Systems:
i. Simplicity vs. Complexity: The Two Kingdom system was simpler, but too broad. The Three Kingdom system acknowledged more complexity in life forms.
ii. Recognition of Microorganisms: Microorganisms got overlooked in the Two Kingdom system due to their size and differences in cell structure. The Three Kingdom system recognized their uniqueness.
iii. Cellular Organization: The Two Kingdom system didn't consider cellular organization, while the Three Kingdom system started to sort life forms based on whether they had a nucleus or not.
List of Important Questions for Self-Study:
i. What was the basis of the Two Kingdom system of classification?
ii. Why did scientists feel the need to move from the Two Kingdom to the Three Kingdom system?
iii. What are some limitations of the Two Kingdom system?
iv. How did the introduction of the Three Kingdom system improve classification?
v. What kind of organisms would be classified under Protista in the Three Kingdom system?
vi. Why is it important for classification systems to be updated over time?
vii. How did the discovery of the cell nucleus affect biological classification?
viii. Can you name an organism that would be challenging to classify under the Two Kingdom system?
ix. What criteria are used today to classify organisms that were not considered in the Two Kingdom system?
x. How does the way we classify organisms affect our understanding of their evolution and relationships?
Important Terminologies Used in Lesson:
i. Two Kingdom System: The classification of living organisms into Plantae and Animalia based on physical characteristics such as mobility.
ii. Three Kingdom System: The addition of the kingdom Protista to accommodate organisms that didn't fit into Plantae or Animalia.
iii. Five Kingdom System: The expanded classification system that includes Monera, Protista, Fungi, Plantae, and Animalia, recognizing differences in cell structure and function.
iv. Cell Nucleus: A membrane-bound structure within a cell that contains the cell's genetic material.
v. Protista: The kingdom that includes mostly unicellular organisms that have a nucleus.
