跟读练习: How Large Can a Bacteria get? Life & Size 3 - 通过YouTube学习英语口语
C2
In and out.
145 句
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In and out.
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In and out.
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Staying alive is about doing things.
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This very second, your cells are combusting glucose molecules with oxygen to make energy available,
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which keeps you alive for another precious moment.
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To get the oxygen to your cells, you're breathing.
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Breathing is an answer to a very hard problem.
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How do you get the resources that your cells need to survive from the outside to the inside of your cells?
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Every living thing has to solve this problem
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and the solution is surprisingly different depending on one of the most important regulators of life, size.
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As we've discussed in other videos,
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at different scales the physical laws of the universe have different consequences for its inhabitants.
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Simple things like temperature, microgravity or surface tension might not matter to you or be a deadly danger,
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depending on how big you are.
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Living things need a lot of different materials to keep themselves going.
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And they somehow need to transport them from the outside to the inside.
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This was a huge problem for the first things on the verge of being alive,
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because doing anything in our universe requires energy.
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And the first living beings on Earth did not have the abundance of tools
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and techniques available that life has today after billions of years of evolution.
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So, at the very beginning,
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life needed to find a way to get good stuff inside and bad stuff outside of itself without using energy.
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Luckily, the very first forms of life were very, very small.
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And because they were so small,
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they were able to use a free form of transport that was based on a physical law called diffusion.
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Diffusion is the rule of the universe that molecules,
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especially in liquids or gases,
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are constantly moving around in all directions.
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And because they move around and bump into each other and other molecules,
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they tend to spread.
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For example, if you drop a sugar cube into water,
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then there is a lot of sugar in one place,
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and in another place, there's none.
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As sugar molecules dissolve in the water,
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they will start randomly bumping against the water molecules and other sugar molecules.
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Slowly, all the sugar molecules will spread out and form multiple phases of different concentrations.
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These random movements continue endlessly until at some point the sugar will be spread evenly in the water.
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The great thing about diffusion is that life can use it for free.
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It doesn't require energy.
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And life loves free things.
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So all life on earth relies on diffusion.
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Let's look at the smallest living being on earth, a bacterium.
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Specifically its surfaces.
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Cell membranes allow for diffusion of certain molecules.
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This specific bacterium consumes oxygen to live while carbon dioxide is produced inside as a waste product.
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So inside the bacterium there isn't a lot of oxygen but a lot of carbon dioxide.
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Because of diffusion these molecules will eventually spread evenly
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so the carbon dioxide diffuses out while oxygen is constantly replenished from the outside.
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But this kind of breathing only works for the very small world,
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for bacteria, amoeba or your cells,
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and a few very small animals.
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Insects, for example, have a fine network of trachea,
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tunnels with a pressure gradient where air very slowly can diffuse in and exchange gases with the insect cells.
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But even insects seem to be able to contract their trachea,
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and at least some even have specialized breathing organs like spiracles and air sacs.
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At certain scales, diffusion is just too slow to keep cells alive.
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The fundamental problem is that the exchange with the environment can only happen at the surface
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and diffusion of materials can only sustain a certain amount of inside.
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Tiny living things have only a little bit of inside or volume and a lot of outside or surface area.
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But what if we wanted to create a bacteria the size of a blue whale and had a very convenient enlargement machine?
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We would sadly be messed up by the square cube law.
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In a nutshell, it means that if you make something 10 times larger,
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its outside or surface would grow by 100,
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but its insides or volume grows by 1000 times.
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If we compare the bacterium Pseudomonas aeruginosa with a blue whale,
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we see that the bacterium has 10 million times more surface in relation to its volume than the whale.
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The bacterium has a lot of outsides,
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while the whale has a lot of insides.
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If we make a bacterium the size of a whale,
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our giant bacteria now has too much insides,
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and most of its inside is now very far from its surface.
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The oxygen our bacterium needs would never reach the inside before it would run out of oxygen.
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Our giant bacterium would just die.
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Still, being bigger has many upsides.
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From making it harder to be eaten to making it easier to eat others.
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But the size of cells is limited by the distance oxygen
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and nutrients can effectively diffuse to provide the inside with enough resources.
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So, life avoided this problem by forming multicellular structures.
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Beings composed of many cells instead of one.
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Because diffusion works better if you have many small units instead of one much bigger one.
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Over time, the cell buddies began to share work and specialize.
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Some cells concentrated on sensing the environment,
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others on digestion, others on movement.
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But that still wasn't enough.
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The problem of diffusion and surface and energy production remained,
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limiting the size these first multicellular forms of life could attain.
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So, in order to become even bigger,
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life solved the diffusion problem by having holes and caves and tunnels and by folding in on itself,
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so diffusion could happen easily in each one of the cells.
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Take yourself.
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What you consider your outside,
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your skin, has a surface area of about 2 square meters.
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But your lungs have a surface area of about 70 square meters.
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They aren't like balloons.
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They're more like sponges filled with many tiny packed tiny balloons surrounded by blood vessels.
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When you breathe in, all these tiny balloons fill up with fresh air.
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Blood filled up with CO2 is pumped around the balloons.
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And then the magic of diffusion happens.
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The oxygen diffuses into the blood where it's picked up by red blood cells.
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And the CO2 diffuses out of the blood and into your lungs where it can be breathed out again.
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Your blood then carries oxygen-rich blood into the furthest corners of your body and picks up the CO2 waste.
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Diffusion in the body is effective at about 1 mm one millimeter
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so every cell in your body is at most one millimeter away from a blood vessel.
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So medium-sized animals like you need a lot of blood vessels to reach every cell in the body.
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Your body has around 100 000 kilometers of capillaries alone,
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the tiniest of your blood vessels,
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with a surface area of around 1 000 square meters.
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This is true for all parts of you that want to exchange something with the outside world.
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Your body needs surfaces to take in nutrients from your food,
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so your gut has the surface area of half a badminton court,
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roughly 40 square meters.
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The larger you are, the more hidden surfaces you need.
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Take a tree.
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Its way to stay alive is to create sugar out of thin air and sunlight.
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So, it needs as much surface area as possible.
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An orange tree with 2,000 leaves has a leaf surface area of 200 square meters.
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But the surface inside the leaves where diffusion actually occurs is 6,000 square meters.
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The same with roots where water diffuses from the soil into countless tiny hairs that maximize the surface area.
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The roots of one square meter of grass add up to around 350 square meters of surface.
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If we look at the breathtaking diversity of life on this planet,
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it seems like everything is pretty different.
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And it is.
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But some basic principles are the same for everybody and have not changed significantly for billions of years.
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If we look at the very,
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very small or the very,
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very big, waste goes out and fresh fuel comes in.
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Big animals just need a lot of complex plumbing to make it possible.
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This bird has magical powers.
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Let's see a demonstration.
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Bring in the latest scientific research.
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Wow, that's a lot of complicated stuff about the immune system and all its cells.
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How could someone possibly understand all of this?
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Incredible!
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This overview is delightful and easy to grasp, but still scientifically accurate.
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Let's make it a bit more difficult.
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Can she make all of evolution visible at a glance?
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This is brilliant!
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You can clearly see the relationships between species and how they evolved.
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And look at those illustrations!
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These posters are ready to be shared with the world.
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These very special pieces of Kurzgesagt are now available on our shop along with many other sciencey products,
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all researched with care and created with love by the Burbs with magical powers.
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Every Kurzgesagt product you buy directly funds another moment we get to spend working on our videos.
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Thank you so much for being a part of our story and for making this channel possible.
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Thank you.
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背景與脈絡
在這段影片中，講者深入探討了細胞如何獲取氧氣以維持生命的過程，並闡明了不同大小的生物所面臨的獨特挑戰。尤其是細菌等微小生物，它們如何利用擴散這一物理法則將所需的物質從外部轉移到內部。在理解這些原理的過程中，學習者可以獲得更豐富的科學知識，同時提升英語聽說能力。
日常交流的五個關鍵短語
- 保持活著 (Staying alive)
- 獲取氧氣 (Get the oxygen)
- 運輸資源 (Transport resources)
- 能量 (Energy)
- 擴散作用 (Diffusion)
這些短語不僅幫助了解生命運作的基本概念，同時也可以用於日常生活中，例如討論健康和生物學時。可以在shadowspeaks上找到更多此類的實用表達，進行英文的影子講述練習。
逐步影子模仿指南
要有效地學習這段影片中所呈現的資訊，以下是建議的逐步學習策略：
- 收聽與理解：首先，完整觀看影片，對內容建立基本理解。注意講者的口音和語調。
- 選擇短片段：選擇影片中的一句或兩句進行重複學習，例如“保持活著”或“擴散作用”。
- 進行影子講述：重複講者的句子，努力模仿其語調和節奏。可以使用shadowing site工具幫助對比。
- 錄音並回聽：錄下自己的朗讀，與原聲帶進行比較，找出需要改進之處。
- 持續練習：每天安排定時的口語練習，特別是利用這些科學術語，例如在雅思口語練習中運用這些知識。
透過這些步驟，學習者將能夠不僅增強英語口說能力，亦能在生物學的知識上拓展邊界，這對於學習者的全面發展是非常有益的。
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。