Photosynthesis History Lesson Part 1

Summary

The history of photosynthesis is a gradual story of discovery, highlighting that scientific knowledge is built over time. The video starts by explaining why it's important to understand the process that led to our current knowledge of photosynthesis. Shannon Isenhower outlines a note-taking strategy for students, involving three sections to capture details about scientists, experiments, and learnings. The lesson covers key figures like Yan Von Helmont, who conducted early quantitative experiments on willow trees, and Joseph Priestley, who discovered oxygen's role in air quality with his mouse and candle experiments. These historical milestones illustrate how our understanding of photosynthesis and respiration evolved, showing the interplay between animals and plants.

Highlights

• Yan Von Helmont was a quirky scientist from the 1500s who discovered carbon dioxide 🌿
• Yan's experiment involved growing a willow tree to understand plant mass, a leap in quantitative science 📏
• After five years, he observed the tree mass increased significantly while soil mass slightly decreased 🌱
• Joseph Priestley's discovery of 'dephlogisticated air' or oxygen changed how we understood atmospheric interactions 🌬️
• Priestley's mouse and candle experiments highlighted how plants could repair 'injured' air by respiring 🌿

Key Takeaways

• Science is a gradual process of discovery over time 📚
• Yan Von Helmont's important contribution was discovering carbon dioxide through an innovative willow tree experiment 🌳
• Joseph Priestley revealed the crucial role of oxygen in sustaining life with his candle and mouse experiments 🔬
• Early experiments laid the foundations for understanding photosynthesis and respiration 📖
• The importance of detailed note-taking and experimentation in scientific discovery is emphasized ✍️

Overview

Welcome to a fun journey through the history of photosynthesis! Our lesson kicks off with Shannon Isenhower explaining why understanding the historical context of science – particularly photosynthesis – is crucial. She guides students on creating organized notes, setting the stage for a structured dive into the scientific breakthroughs that eventually pieced together our understanding of this essential biological process.

First on the time machine is Yan Von Helmont, who lived in the 1500s. He wasn't just a quirky guy with strange ideas; he was a pioneer in experimenting with plants. Helmont's famous willow tree experiment was a trailblazer in quantitative science, where he meticulously measured the mass of a tree and its soil over five years. His conclusion about water being the source of a tree's mass, while not entirely accurate, marked the beginning of understanding plant growth.

Next up, it's Joseph Priestley, the man who flirted between pastoring and science to uncover one of the greatest discoveries – oxygen, or as he called it, 'dephlogisticated air.' Through brilliantly simple experiments with candles and mice, he demonstrated that plants could revive 'injured' air. This was an enormous leap towards realizing the symbiotic relationship between plant photosynthesis and animal respiration. It was the perfect puzzle piece added to the story of photosynthesis.

Chapters

• 00:00 - 00:30: Introduction to Photosynthesis History This chapter introduces the history of photosynthesis, emphasizing that scientific discoveries are gradual and not instantaneous. It explains that the understanding of photosynthesis evolved over many centuries, involving numerous contributors. The lesson aims to demonstrate that scientific knowledge is cumulative and collaborative.
• 00:30 - 01:00: Taking Notes on Photosynthesis The chapter 'Taking Notes on Photosynthesis' provides guidance on how to effectively organize notes while learning about the process of photosynthesis. It suggests dividing a notebook page into three sections: a smaller section on the left for the scientist's name, a larger middle section for details about the experiment and possibly a drawing, and a third section on the right for additional information. This structured approach aids in understanding the various components and experiments related to photosynthesis.
• 01:00 - 03:00: Van Helmont's Discovery The chapter discusses a scientist's discovery in the field of photosynthesis related to a notable gas.
• 03:00 - 06:30: Priestley's Experiment with Air The chapter titled 'Priestley's Experiment with Air' introduces Yan Von Helmont, a scientist from the 1500s known for his peculiar ideas and significant discovery of carbon dioxide. Although Helmont didn't grasp the full importance of his discovery at the time, his work focused on studying trees, plants, and the sources of their mass, demonstrated through his experiment of growing a willow tree in a controlled environment.

Photosynthesis History Lesson Part 1 Transcription

• 00:00 - 00:30 welcome to your history of photosynthesis lesson now why are we looking at the history of photosynthesis this is Biology class well because I want you guys to know that science doesn't happen all at once science is a gradual process so it wasn't like some guy woke up someday and said hey photosynthesis this is how it happens it was actually many many people over many hundreds of years actually that
• 00:30 - 01:00 gradually discovered all the little pieces that fit together into photosynthesis as we're going to learn about it in this unit so let me tell you a little bit about your notes right now you have your piece of paper in your notebook I want you to split that to three sections on the left you're going to have a smaller section you're going to write the scientist's name in the middle you need a bigger section where you're going to talk about the experiment and maybe draw a picture of the experiment they did if that's appropriate and then on the right you're going to have a third column and in that
• 01:00 - 01:30 column you're going to write what did we learn about photosynthesis from that experiment so for every slide here you're going to have a scientist and experiment and what we learned about it so our first scientist now this guy actually discovered something really important that I'm sure you've all heard of which is called gas Sylvester or maybe you know it as carbon dioxide
• 01:30 - 02:00 now his name was Yan Von Helmont and as you can see he lived in the 1500s um he was kind of a quirky guy he had a lot of strange ideas about how the world worked but he also made a really important Discovery um he did discover carbon dioxide he didn't know how important it was his Discovery actually had to do with trees and plants and where their Mass came from so he grew a willow tree and a popped and this
• 02:00 - 02:30 experiment we're going to talk about was one of the few like very first quantitative experiments which means it was one of the very first experiments where someone actually carefully measured um the quantities the things that went into it and use numbers to analyze the experiment as opposed to just general observations so it used numbers um nowadays of course we always use numbers in experiments but he was one of the first to do so so so he put
• 02:30 - 03:00 his Willow Tree in a pot and it was a lovely willow tree and he very carefully measured how much the tree weighed and he measured how much the dirt that he put in the pot Wade and the very first day he had a 5 lb tree and 200 lb of dirt then he carefully watered his tree every day and that's all he did was water it and he didn't add anything else to the pot or the chy tree and he let it go
• 03:00 - 03:30 grow so as you might imagine over time it grew quite big and after 5 years yes he was a very patient man had a very long experiment after 5 years his willow tree and his pot had grown quite large so he took out the tree and he took out the dirt and he weighed it all very carefully and he found out that he had a tiny bit less dirt than he started with so he lost like a tenth of a pound of dirt but he had a whole lot more more
• 03:30 - 04:00 tree he had 169 lbs of tree now the only thing he had done to this tree the entire time was water it so quite logically he concluded that the tree was made of water that that was what had turned into all of the leaves and the wood was the water because it was the only thing he added to the pot now we know now that it wasn't the whole picture but still it was a start
• 04:00 - 04:30 remember this is a step-by-step process all right our next guy also discovered an important guas uh you may not know it as deep Logistic Air nowadays we call it oxygen um but again he didn't know the importance of his Discovery sometimes discoveries uh don't see seem so important at the time but our next guy Joseph Priestley who did actually um do some work as a pastor for for a while so
• 04:30 - 05:00 his name wasn't entirely inappropriate uh Joseph Priestley did a very important experiment involving candles and some dead mice so he noticed that a candle if you put it into a closed container just like if you put a mouse in a closed container both of them would die the candle would go out if you put it in the closed container and the mouse yes he abused mice or Mouse uh if you
• 05:00 - 05:30 put a mouse in a closed container it would die now we know yes the mouse ran out of air but he didn't really know what was in the air remember he had just barely discovered oxygen at the time we didn't know all the components of air so what he thought was both mice and candles did something to break the air to injure it to make it not useful anymore but then he did a second experiment and found out that if he took a plant and put it in the container with
• 05:30 - 06:00 his Mouse the mouse actually would survive it wouldn't die so he concluded since the plant made it so the mouse didn't die that the plant could somehow repair the air that had been injured by the mouse so his important Discovery here was that animals and also cannibals basically did a process that was the opposite of whatever plants did so we now know these as photosynthesis
• 06:00 - 06:30 and respiration but this was a big Discovery at the time that plants and animals were sort of opposites of each other that something was happening with plants that fixed whatever animals caused then of course you know I I think we should have stuck with eup fisticated air I think it has a much nice nicer ring to it but you know Oxygen's okay too okay so now we know that air getss injured that animals gets rested by plants what happens next