Characteristics of Living Things

Biotic vs. Abiotic

What makes something living, or biotic, or part of the bios of this planet? What makes me different than the zombies in Walking Dead, or better yet, Night of the Living Dead? Why is Young Frankenstein’s monster here not living? Or is he? Ever see this movie? You should. Great comedy.
You probably have a feel for what a living thing is, but it’s hard to explain. Some people will say something is living if it is breathing or if it can move. But what about bacteria? Or a jellyfish? They don’t have lungs, are they not breathing? The qualities of living things is actually much more broad than something like “breathing.” And, yes, bacteria and jellyfish are exchanging gases with the environment, it’s just that they are small enough that this happens by way of diffusionPassive movement of molecules from areas of high to low concentration..

Characteristics of Living Things

Every living thing shows order. This sunflower has its female reproductive organs surrounded by the male reproductive organs, then surrounded by the attractive petals. Order. I know that we may never see each other in person, and I’m surely never going to tape a video of myself when I’m sick, but when I’m ill, my body has a hard time maintaining order. I definitely look disorderly. Are you the same? Just an incredible mess when you’re sick? Your body is spending so much of its energyThe capacity to do work or cause change. making white blood cellsThe basic structural and functional units of life., you divert your energy to that instead of things like brushing your hair, or taking a shower, or even brushing your teeth. Ever been so sick you can’t even brush your teeth? Order is an implication that your body, and bodies of other living things, maintain homeostasisThe maintenance of a stable internal environment in the body. or an internal steady state despite fluctuations in the external environment.

This rabbit with the crazy ears shows a property of regulation. Your body temperature, your blood pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange., your blood glucoseA simple sugar that is the main source of energy for cells. levels, and even the sheer arrangement of your bodily structure is a reflection of regulation. This guy here is using the thin membranes of his ears to help maintain his body temperature. Can you see the blood vessels in his ears? These vessels, so close to the surface on both front and back sides, are helping him blow off body heat in the hot prairie environment. Elephants do the same thing. This is why you always see them flapping their ears when they are hot. They are regulating their internal environment by increasing their exchange with the external environment.

Characteristics of Living Things

These three characteristics of living things are very inter-related. Growth, developmentThe process of growth and differentiation., and reproductionThe process of producing offspring. all require energy. We consider reproduction and development of organisms in the second part of this course. We also consider growthAn increase in size and number of cells. of not only individuals, but of populations, like the human population. In this course, we talk in depth about energy processing, which indicates how organisms acquire energy (both plants and animals) and how they convert it within their bodies to something that their cells can use, a little molecule called ATPThe energy currency of cells used for muscle contraction..

Characteristics of Living Things

I’m sure you can recognize the plant on the left as a Venus Fly Trap, but what is that on the right? These plants are what are known as photoheterotrophs. They are able to do photosynthesis, but since the soil in which they usually live is so poor, they look for sources of food other than those from their own photosynthesis (heterotroph). These plants are responding to their environment and the food that they can acquire from it. When conditions are poor, they eat bugs. So, don’t fertilize your Venus Fly Trap if you want to see it eat a bug!
The other picture is a moth, not an owl. This moth is clever, in that it is camouflaged to look like an owl, a vertebrate predator, that lives in its environment. By looking like this owl, the moth is able to avoid its own predators who are usually prey for the owl. In any given generation, there may be variations of this patterning in the moths. Those that survive predation the most, probably those that look the closet to the owl, will survive, make babies, and pass on their genes. This could be called evolution by way of natural selection. There are many ways to evolution, not just natural selection. These topics are also discussed in more detail in the second part of this course.

Characteristics of Living Things

Are these valid qualities of living things? Maybe. Maybe just for now, based on life as we know it. All living things, whether they have many cells or one cell, are made of cells. In factA statement based on direct observation that is repeatedly confirmed., there’s something called cell theoryA well-tested and widely accepted explanation. that says that all cells come from preexisting cells. As a good science student, this should make you ask: then where did the first cell come from? That’s a topic for next semester. These cells here are plant cells. You can see the little chloroplasts in the cells. These are the organellestructures within a cell that perform specialized functions. that convert sunlight to energy that is useable by the plant.
I’ve also included here DNA because every living thing we currently know has DNA. Here’s the thing though, if we were to discover life on a different planet, they may have subunits of their structure, but maybe not cells. There may be a language on which their life is based, but it may not be DNA. So, I guess this slide is a remind that what we know now will change as our abilities to explore the universe advance.

Characteristics of Living Things

Let’s start here with organisms you know, like frogs, and kitties, and tuna fish and various ungulates (hoofed mammals). These things are also familiar, grape vines, algae, and Methusala, this tree here which is the oldest living organismA living individual made up of cells.. I just have to point out that the grapes and the tree are plants. The algae is something different called Protists.

Characteristics of Living Things

These fungi look kinda familiar to some students. We have some shelf fungus and a blue mushroom. This microscope picture on the bottom left is penicillin, which is a fungus used to the great advantage of humans. And the other microscope picture is of yeast, which many people think is a bacteria, but it is a fungus. These pictures up here are of bacteria. This is a guitar string with colonies of bacteria living on it that you see as dirt on the coils of the string. This picture has a big brown white blood cell that is surrounded with green pill-shaped bacteria. And finally we have the most baffling of organisms, something called protists. These are celled dinoflagellates, which cause the red tides in the ocean, and diatoms. Diatoms are microscopic and live most in marine environments. These would be the photosynthesizers of the ocean.

Domains of Life

All the organisms we just looked at are obviously living, but how do we make it simple in starting to look at and categorize them? Well, based on rRNA(ribosomal RNA) – RNA that forms part of the ribosome and helps in protein synthesis. sequences, we can divide all life into 3 large groups that we call domains. We have the domain bacteria and the domain archaea which contain single celled organisms that are simple in design or prokaryotic, a word meaning “simple kernel.” The domain eukarya contains the organisms with which most student are familiar like plants, animals, fungi, and even the protists. In this course, we focus on the complex cells of eukaryotic organisms. Do you see the sloth on the bottom right. A former student of mine too a trip to the Galapagos Island and she brought me a calendar of sloths. She said she saw it an instantly thought of me. I’m not sure if it’s because I use sloths as examples a lot or if I’m an extremely slowly moving person. Either way, awesome calendar.