Origins of Cells (Topic A2.1 – AHL Only)

Essential Idea(s): The origins of the first cells on Earth can be investigated and evaluated with empirical tools.

Unit Length: 2 Lessons (AHL Only)

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Guiding Questions

◊ What plausible hypothesis could account for the origin of life?

◊ What intermediate stages could there have been between non-living matter and the first living cells?

Materials:

Teaching Slides	Quizlet Vocab Set
	Notes Template

IB Statement(s) and Objective(s)

A2.1.1: Conditions on early Earth and the pre-biotic formation of carbon compounds

List the four major classes of carbon compounds used by living organisms
Outline the reasons why carbon is the base element of organic chemistry
Outline the chemical conditions on early Earth
Explain the role of a UV radiation and a lack of ozone in the formation of early organic compounds

A2.1.2: Cells as the smallest units of self-sustaining life

Discuss the differences between something that is living and something that is non-living
Describe the functional characteristics of life
Discuss the reasons why viruses are considered to be non-living

A2.1.3: Challenge of explaining the spontaneous origin of cells

State the three parts of the cell theory
Discuss implications of all cells being formed from preexisting cells
Outline the environmental requirements for the evolution of the first cells
Outline the four processes needed for the spontaneous origin of cells on Earth
NOS Concept*: Claims in science must be testable

A2.1.4: Evidence for the origin of carbon compounds

Evaluate the Miller-Urey experiment

A2.1.5: Spontaneous formation of vesicles by coalescence of fatty acids into spherical bilayers

Outline why fatty acids were likely the primary component of the membrane of early cells

A2.1.6: RNA as a presumed first genetic material

Outline the reasons why RNA is presumed to be the first genetic material

A2.1.7: Evidence for a last universal common ancestor

Outline the evidence for a last universal common ancestor (LUCA)

A2.1.8: Approaches used to estimate dates of the first living cells and the last universal common ancestor

Outline approaches used to estimate dates of the first living cells

A2.1.9: Evidence for the evolution of the last universal common ancestor in the vicinity of hydrothermal vents

Define and describe hydrothermal vents
Summarize the evidence supporting the hypothesis that LUCA originated in/around hydrothermal vents


Activities: ⓟ = podcast / ⍰ = inquiry 5 / ⓦ = Write it / Ӕ = The academy / Ⓡ = Read it
ⓟ/ⓦ: TedEd – How Life Began (💁 [if writing] / 👭 [podcast only] – max 3) How did life really begin on Earth? Watch this TedEd video, and respond to the key ideas. Discuss the relevance of monomers → polymers (polymerization), RNA, and how this could have ultimately led to the origin of the first cell. Use this to make connections to the key ideas found in the statements and objectives from this level. ⍰/ⓟ/ⓦ/ⓡ: Scientists say the ‘R’ in RNA may be abundant in space (💁 [writing] / 👭 [podcast only] max 3) Read about a recent experiment in which scientists asked: could the solar system provide conditions for ribose (the R in RNA) to form naturally? Follow this up by reading the abstract to the actual experiment. Then write 3-5 of your own inquiry questions about the article, linking as many ideas from this unit as possible. Then, if working on your own, write out answers; and if working in pairs, record yourself asking your questions to a partner. Lab! ⓟ/ⓦ: Design an Origins of Life Lab (💁 [if writing] / 👭 [podcast only] – max 3) We’re a small high school with a small high school lab, but you can still use your imagination to design a basic methodology to investigate the idea that LUCA originated from hydrothermal vents. What could you do to support or refute the idea that LUCA came from vents? What kind of evidence would help answer this? Your lab design should include: A brief introduction and background knowledge presentation Clearly defined variables – make sure you address the key independent, dependent, and control variables. A hypothesis of what you would expect, backed with scientific reasoning A summary of the method you could use What you would do with the data, once collected ⍰/ⓟ/ⓦ: Q&A on the Origins of Life (💁/ 👭max 2) Create a list of 3-5 or more inquiry questions related to the origins of life on Earth. Partner up with another student and answer their questions. Remember that good inquiry questions are conceptual / open-ended… Such as: “Why would life need to be contained in a membrane, such as a micelle? NOT: “What are micelles?” If working solo, give answers to your own questions; if working in pairs, record yourselves asking each other your 5 questions. *Try to write questions that cover as many topics from A2.1 as possible!