Lesson 7 - Evolution of Eukaryotic and Multicellular life (HL Only)

Lesson Objectives

Content Objective: XXX

Language Objective:  XXX

Syllabus Details: 

A2.2.12 - Origin of eukaryotic cells by endosymbiosis "Evidence suggests that all eukaryotes evolved from a common unicellular ancestor that had a nucleus and reproduced sexually. Mitochondria then evolved by endosymbiosis. In some eukaryotes, chloroplasts subsequently also had an endosymbiotic origin. Evidence should include the presence in mitochondria and chloroplasts of 70S ribosomes, naked circular DNA and the ability to replicate."

A2.2.13 (HL) - Cell differentiation as the process for developing specialized tissues in multicellular organisms - "Students should be aware that the basis for differentiation is different patterns of gene expression often triggered by changes in the environment."

A2.2.14 (HL) - Evolution of multicellularity - "Students should be aware that multicellularity has evolved repeatedly. Many fungi and eukaryotic algae and all plants and animals are multicellular. Multicellularity has the advantages of allowing larger body size and cell specialization."


Activites

Activity 1  - Endosymbiotic Hypothesis


Activity 2 - Evolution of Multicellularity - 

Video 1 - The momentous transition to multicellular life may not have been so hard after all

How does this video help explain the importance of genes in the development of multicellularity?

How do the experiments show the possibility of multicellularity?



Video 2 - How Did Multicellularity Evolve?

a. What are some of the advantages of multicellularity? 

b. Cell specialization is a vital part of multicellularity. Use examples from the video to explain why.

Activity 3 : Tracing the Evolutionary Timeline

Activity Directions:

Objective: Create a comprehensive timeline that showcases the evolution from unicellular ancestors to the development of multicellular organisms, emphasizing concepts like endosymbiosis and cell differentiation.


1. Timeline Creation:

a. Align your paper to create a long horizontal timeline.

b. At one end of your timeline, label it as "Origin of Eukaryotic Cells". At the opposite end, label it "Evolution of Multicellularity".


2. Eukaryotic Origins & Endosymbiosis:

a. Begin by placing an image of a unicellular eukaryote at the very start of your timeline.

b. Moving slightly ahead on the timeline, position images of mitochondria and chloroplasts. These represent the evolution of these organelles through the process of endosymbiosis.

c. Next to the images of mitochondria and chloroplasts, use sticky notes to annotate evidence supporting endosymbiosis. These should include terms such as "70S ribosomes," "naked circular DNA," and "ability to replicate".


3. Cell Differentiation:

a. Moving further along your timeline, position images that represent early multicellular organisms.

b. Around these images, use sticky notes to emphasize the onset of cell differentiation and the eventual formation of specialized tissues.

c. Ensure you also have a note or section that touches on the core concept that differentiation arises from "different patterns of gene expression," often influenced by environmental factors.


4. Evolution of Multicellularity:

a. Continuing along your timeline, place images that represent fungi, algae, plants, and animals.

b. Using sticky notes or markers, annotate and highlight the distinct periods when multicellularity is believed to have evolved within these groups.

c. Conclude this section by noting the benefits that multicellularity brought to these organisms, such as the potential for "larger body size" and the luxury of "cell specialization".


End Note: Once you have completed your timeline, review each section to ensure clarity and accuracy. Reflect on the evolutionary progression, understanding the significance of each step in the journey from simple unicellular life to complex multicellular organisms.