Characteristics of Life

Summary

Join the Amoeba Sisters as they dive into what makes something alive. Unlike toys that only enlarge in water, living organisms undergo growth and development based on genetic material. Exploring the characteristics of life, including metabolism, homeostasis, and evolution, reveals the complexity and intricacies involved. Homeostasis maintains balance, metabolism drives energy processes, and evolution reflects adaptive changes over time. Despite the general attributes of life like response to stimuli or reproduction, debates exist, such as the status of viruses, which lack several key life features. So, what truly marks something as living? These ongoing discussions highlight the dynamic nature of biological sciences and encourage curiosity.

Highlights

• Toys can grow in size, but only organisms grow based on genetic instructions 🧬.
• Understanding life involves exploring complex processes like metabolism, homeostasis, and reproduction 🌿.
• Metabolism involves converting energy for use in life processes, essential for sustaining life 🔥.
• Living organisms grow, develop, and respond to stimuli based on their genetic makeup 🌱.
• Homeostasis is vital for maintaining internal stability amidst external changes 🌡️.
• Evolution showcases how life forms adapt over time, but not all entities like viruses fit the living criteria 🦠.
• Viruses reproduce and evolve, yet defy the typical classification of living organisms.
• Biological sciences are ever-evolving, continuing to explore and redefine what it means to be alive 🌌.

Key Takeaways

• Living things grow based on genetic instructions, unlike toys that just get bigger in water 🧬.
• Homeostasis is crucial for life, keeping conditions inside stable even when outside changes 🌡️.
• Metabolism involves chemical reactions to release energy, fueling life processes such as growth and reproduction 🔥.
• Life can reproduce through various methods, including cellular division or more complex forms like conception and gestation 🐣.
• Evolution illustrates life’s adaptability, leading to the development of new traits and species over time 🌱.
• Viruses challenge our definitions of life since they can reproduce and evolve but need a host 🦠.
• The study of life's characteristics remains dynamic and continually evolving, inviting endless questions and curiosity 🌌.

Overview

The video kicks off by contrasting toys that swell in water with living organisms, which grow by following genetic instructions. This sets the stage for an exploration into the defining characteristics of life. The journey begins with the cell theory, homeostasis—a balancing act for survival, and metabolism—the process that fuels life itself.

As the discussion unfolds, reproduction and development emerge as crucial life processes. Whether it’s a simple cellular split or complex conception, the role of genetic material is crucial. Response to stimuli gets a nod here, as living beings react to internal and external cues, from a pony’s hunger pangs to a cactus leaning towards light.

The video also dives into more advanced territory with evolution—a testament to life's adaptability, explaining how gene frequencies shift over time due to natural selection. Yet, this characterization isn’t crystal clear, highlighted by the enigma of viruses, which can reproduce and evolve but don't tick all the life boxes. This invites viewers to ponder: what exactly defines life?

Chapters

• 00:00 - 01:00: Introduction and Toy Pony The introduction uses a playful anecdote about toys that grow when placed in water to engage readers. There's a personal story about a toy pony that was expected to grow very large when left in a bathtub for several days. Although it did grow, it did not quite meet the exaggerated expectations set by its packaging, setting up a theme about expectations versus reality.
• 01:00 - 02:00: Exploring Biological Growth The chapter titled 'Exploring Biological Growth' begins by introducing a personal anecdote where the narrator discusses a toy pony that seemingly grows in size, sparking their imagination to consider its liveliness. This is contrasted with a discussion on biological growth and development, clarifying that an increase in size, like that of the toy, does not equate to being alive. The narrative transitions from this imaginative perspective to a more scientific discourse on what constitutes true biological growth.
• 02:00 - 03:00: Defining Life and Characteristics of Living Things The chapter titled 'Defining Life and Characteristics of Living Things' delves into the complexities of understanding what makes an organism alive. It highlights that while life is challenging to define, exploring the characteristics of living things is essential in the study of biology. The text acknowledges that the concept of being 'alive' remains a topic of ongoing inquiry and debate among biologists. Additionally, it notes the continuous discovery of new organisms and emerging information in biological sciences, emphasizing that our understanding of life is always evolving.
• 03:00 - 04:00: Organization in Living Things The chapter discusses the organization in living things, emphasizing that the characteristics of life are not universally agreed upon and can vary. It highlights the fluid nature of these characteristics, cautioning against assigning a specific numerical value or a fixed order to them, and acknowledges the possibility of exceptions or additional characteristics that might not be mentioned.
• 04:00 - 05:00: Homeostasis in Living Organisms This chapter explores the theme of homeostasis in living organisms, emphasizing the importance of understanding what it means for an entity to be alive. It delves into the fundamentals of cell theory, noting that living organisms are made of cells, which can be unicellular, consisting of just one cell. The chapter encourages thinking beyond mere memorization to a deeper comprehension of life's characteristics and organization.
• 05:00 - 06:00: Metabolism and Energy Use The chapter titled 'Metabolism and Energy Use' discusses the biological levels of organization in more complex organisms, such as animals, which are multicellular and comprised of various cells arranged into tissues, organs, and organ systems. It emphasizes the importance of homeostasis, or maintaining a regulated internal balance, which is vital for many biological processes to occur. The example of a 'bathtub-grown pony' highlights the lack of cellular structure in that conceptual scenario, contrasting with the organized structure in living organisms.
• 06:00 - 07:00: Reproduction Mechanisms The chapter 'Reproduction Mechanisms' explains the concept of homeostasis which is vital for enzymes to function properly. It discusses the necessity of maintaining specific conditions such as temperature and water concentration both in complex organisms like ponies and humans, as well as in single-celled organisms such as amoebas. The transcript emphasizes the importance of feedback systems in living organisms for regulating homeostasis, contrasting it with the lack thereof in artificial environments like a 'bathtub-grown pony.'
• 07:00 - 08:00: Growth and Development Based on Genetics This chapter explores the concept of metabolism as essential for life, emphasizing the necessity for organisms to capture and utilize energy. It highlights the role of metabolism in maintaining homeostasis and provides examples of metabolic reactions occurring in living organisms, particularly focusing on plants as autotrophs that convert light energy into glucose.
• 08:00 - 09:00: Response to Stimuli This chapter explores the biological processes of photosynthesis and cellular respiration. Photosynthesis is highlighted as a process used by autotrophic organisms to produce glucose, while cellular respiration is common to both plants and animals for breaking down glucose to produce ATP energy. In animals, which are heterotrophs, the process includes consuming and digesting food to obtain glucose. Furthermore, the chapter briefly touches on the concept of metabolism, using the example of a pony to differentiate between active and inactive metabolic states. Additionally, it introduces the basic idea of reproduction, particularly highlighting the simplicity of unicellular bacterial reproduction through DNA replication and cell division.
• 09:00 - 10:00: Evolution as a Characteristic of Life This chapter discusses the characteristic of evolution as a fundamental aspect of life. It highlights the reproduction processes of living organisms, using bacteria and ponies as examples. Bacteria can reproduce simply through binary fission, resulting in two bacteria from one. In contrast, ponies have a more complex reproduction process involving the unification of sperm and egg cells to create a zygote, which develops into a baby pony, emphasizing the complexity of growth and development. Additionally, the importance of genetic material in guiding the development and growth of living beings is underscored, indicating that instructions contained within the genetic material are crucial for these processes.
• 10:00 - 11:00: Challenges in Classifying Life The chapter discusses the challenges in classifying what constitutes 'life.' It uses the analogy of a bathtub-grown pony, which may increase in size due to water but does not grow based on genetic instructions, emphasizing that growth and development in living organisms are guided by genetics. It also highlights the importance of responding to stimuli as a characteristic of life, noting that organisms respond to both internal stimuli (such as hunger) and external stimuli (such as danger).
• 11:00 - 12:00: Viruses and the Definition of Life The chapter delves into the concept of life, using engaging analogies and real-life examples such as the behavior of cacti responding to light as a stimulus. It discusses the criteria for life, referencing a working definition provided by Dr. Gerald Joyce during a panel discussion among exobiologists. The narrative hints at the complexity of defining life, especially in the context of entities like viruses, which challenge traditional biological boundaries. Overall, the chapter encourages a deeper understanding of how life can be identified and classified based on its responses to various stimuli.
• 12:00 - 13:00: Extraterrestrial Life and Open Questions The chapter explores the concept of life as a self-sustaining system capable of Darwinian evolution. It highlights the process of evolution as a key characteristic of life, noting that changes in gene frequencies occur over time due to mechanisms like natural selection.

Characteristics of Life Transcription

• 00:00 - 00:30 Captions are on! Click CC at bottom right to turn off. Follow us on Twitter (@AmoebaSisters) and Facebook! Have you ever seen those toys that you can put in water for a few days and then they increase in size? They always have this awesome thing on the package like, “Grows a million times larger in water!”---ok I’m exaggerating---but they do grow impressively larger. I had one once. It was a pony. I had dreams for it to grow especially large, so to give it plenty of room, it spent several days in a bathtub. And while it did technically grow larger, the dreams I had imagined for it did not really
• 00:30 - 01:00 come to be. The fact that it could increase in size sort of gave me some kind of thought in my mind that it just might be alive. Because things that are alive do grow, right? Combine that with my overactive imagination and it was difficult for me to come back to reality that this toy pony may increase in size but it’s not alive. When we talk about biological growth and development, this type of increase in size is not the same thing.
• 01:00 - 01:30 And if we’re going to truly explore biology, the study of life, it makes it essential that we understand characteristics of things that are alive. Life is difficult to define, but the characteristics of living things can be explored. We want to mention right here, before we get started, that what makes an organism “alive” still results in a lot of questioning by biologists. Hey, remember, there are many organisms undiscovered on our own planet---and new information revealed in biological sciences all the time---so this is our disclaimer that this information can
• 01:30 - 02:00 change and is still debated. Kind of like what we mentioned in our classification video. This is why we are not going to give a certain numerical value for how many characteristics of life there are, because we do not want to imply they are in a specific order or that what we are listing cannot be expanded upon---- or that this can’t include exceptions that we may not mention. Also, the characteristics we talk about can certainly be titled differently.
• 02:00 - 02:30 See, we’re not trying to talk about a list that one would memorize here. Our goal is actually to get you thinking about what it means for an organism to be alive and characteristics of life that can be explored when trying to study living things. Organization. We can look at the cell theory here and see that, according to this theory, living organisms are made of cells. Some organisms are unicellular- so they can be made up of just one cell.
• 02:30 - 03:00 But more complex organisms, like this pony here, are multicellular and therefore made up of many cells which can be arranged into tissues---the tissues can make up organs----the organs can be a part of organ systems. These are biological levels of organization! As for our bathtub-grown pony? No cells. Homeostasis. Maintaining a regulated balance is so important for many biological processes to even happen---for
• 03:00 - 03:30 example, enzymes typically need a certain pH range to even work correctly. Maintaining homeostasis can mean maintaining a certain temperature and a certain percentage of water concentration. Ponies and your human body have all kinds of feedback systems in place to maintain homoeostasis, but even a single-celled organism---like an amoeba---relies on its cell membrane to maintain homeostasis internally. Living organisms have regulation of homoeostasis---which is not going on here in bathtub-grown pony.
• 03:30 - 04:00 Metabolism.. If you’re alive, you need to have some way to capture energy and use energy for processes, including some processes that keep homeostasis like mentioned previously. Chemical reactions happening in living organisms are part of metabolism. So just to give some examples of reactions that are part of metabolism in living organisms--- plants are autotrophs and can capture light energy to make glucose in a process known
• 04:00 - 04:30 as photosynthesis. Animals are heterotrophs that typically need to eat something and then digest it in order to obtain glucose. Both of these example organisms break down glucose in cellular respiration to make ATP energy. Metabolism is happening in this pony. But not in bathtub pony. Reproduction. This can be very simple, like unicellular bacteria which can copy DNA and split—into
• 04:30 - 05:00 2---and now you have two bacteria. Or it can be more complex, like this living pony, which involves sperm and egg cells uniting to make a fertilized egg known as a zygote which will eventually develop into a baby pony. No reproduction for this bathtub-grown pony. Growth and Development. Living organisms have genetic material which codes for its development and growth. A baby pony will develop and grow up into a grown up pony because its genetic material contains the instructions for this development and growth.
• 05:00 - 05:30 Bathtub-grown pony may increase in size due to water entering it, but it’s not growing and developing based on genetic instructions. Response to Stimuli. Responding to stimuli is often considered a characteristic of life. There can be internal and external stimuli. If this pony feels the need to eat, this can be due to coordination of many body systems internally alerting the pony that it is hungry. If this pony senses danger, this external stimulus may cause it to flee.
• 05:30 - 06:00 Not so for the bathtub pony. But you know, a response to a stimulus might not be obvious. I used to have a lot of cacti when I was a kid. And while I wouldn’t call them especially exciting when I was a kid, I did notice that if I left them in a windowsill and didn’t rotate them, they would bend---at least, over a period of a few weeks. That’s AMAZING, because they are responding to light. Plants responding to light is a response to a stimulus. Evolution. A working definition of life summarized by Dr. Gerald Joyce as part of a panel of exobiologists
• 06:00 - 06:30 describes life as “a self-sustaining system capable of Darwinian evolution.” Fascinating quote. Many scientists view the process of evolution as a characteristic of life, although this would occur over a period of time. The gene frequencies in a population of living organisms can change over time due to mechanisms, such as natural selection.
• 06:30 - 07:00 Some genes can code for certain traits that result in higher reproductive fitness, while some genes may code for traits that lower reproductive fitness---and therefore may be selected against. Over time, these can result in adaptations. Because the bathtub pony cannot even reproduce in the first place…you won’t see that. Characteristics of life are definitely intriguing to explore. Remember that these characteristics can be adjusted-----or potentially have exceptions. Some things are very hard to classify.
• 07:00 - 07:30 Take viruses. In our virus video, we talk about how viruses are considered, by the majority of scientists, to not be living. Viruses, with their genetic material, can reproduce---although they need a host to reproduce. They can evolve. But overall they seem to lack a lot of the other characteristics of life, and aren’t typically classified as living. It’s also interesting to think about the potential of extra terrestrial life, that is, life that is not on Earth.
• 07:30 - 08:00 Would it still have these characteristics of life that we have discussed? Sometimes with science, we find ourselves with even more questions. Well…that’s it for the amoeba sisters and we remind you to stay curious.