CHARACTERISTICS OF LIVING THINGS CHARACTERISTICS OF LIVING THINGS *Caveat: There is ongoing discussion among biologists as to what this list should be. If you would like to have an opinion…you’ve gotcherself a bucket-o-research to do There are eight characteristics that all living things share*: Cellular organization Obtain and use Energy=Metabolism Growth and development Response to stimuli Reproduce Homeostasis Heredity/DNA Adaptation through evolution

1. CELLULAR ORGANIZATION Cells are the basic building blocks of life…of it’s alive…it’s made of cells. Every living thing is composed of one or more cells. All cells have DNA as some point in their lives, so…all living things have DNA) Organisms (that’s a living thing) can be single-celled or made of many cells. Viruses aren’t made of cells…guess what…they’re not alive. Too bad for them…they can’t get into the movies or play the drums…as far as I know anyway.

2. Obtain & Use ENERGY=METABOLISM Metabolism is the term that refers to all of the activities that go on within a single cell or an entire organism. Energy is required in order to carry out all of these cellular activities. ATP! Metabolic processes include making food, breaking down food, moving materials in and out of cells, and building cells and their components (parts). It’s a lot of work…teenaged cells are lazy…look for them on the couch watching TV…tragic 

3. GROW AND DEVELOP All living things grow at some period of their lives. Unicellular (single-celled) organisms simply grow larger. Multi-cellular organisms (made of many cells) grow by increasing their number of cells. Many organisms go through stages of development. Some just a few…others have many.

4. Response To Environmental Stimuli All living things encountering a change in their environment will respond to that change. Some responses are drastic and some are more subtle…you can’t even see it happen. If you hear a loud noise you might jump…BOO! See? Calm down now. That’s a response. A plant might grow toward a light source…that’s a response too, but you can’t see it happening. Go ahead try to frighten a plant…it’ll ignore you and you’ll just look silly. A stimulus can be: gravity, light, chemicals, vibration, sound, temperature, electricity, etc.

5. REPRODUCE All organisms make other organisms like themselves. Some living things reproduce asexually, others sexually…some…both…no kidding! Asexual Reproduction – single parent produces offspring (fission, budding). Offspring is genetically identical to the parent. Sexual Reproduction– two parents required for reproduction (conjugation) and offspring are a combination of genetic material from both.

6. Homeostasis This fancy word means…a body’s (or a cell’s) tendency to resist change in order to maintain a stable internal environment. Whaaaaa? Ok…your body temperature is about 37⁰C (98.6⁰F). It needs to stay in the neighborhood in order to do all the “body stuff” it needs to do to keep you alive. Keeping your temperature constant…homeostasis! Usually a negative feedback loop is involved (something goes up or down…your body senses it…does something about it…something goes back down or up).

7. Heredity/DNA All living things pass on their genetic information to their progeny (offspring…errr…kids). DNA is the molecule (DEOXYRIBONUCLEIC ACID) that makes it happen.

8. Adaptation through Evolution All organisms are subject to change over time as the environment changes. It’s linked directly to genetics and heredity, so when we study that stuff…we’ll go into a lot more detail. It’s like this…you know how plate tectonic theory explained continental drift (sure ya do)? Well…genetics explains evolutionary theory!

A brief reconnection with… Biomolecules Carbohydrates – made of monosaccharides (sugars), used for short-term energy…structural too! Proteins-made up of amino acids. Can be structural (for building), enzymes (needed for chemical reactions), or messengers. Lipids, fats, and oils – long-term energy storage, cell membrane construction, neurotransmission. Nucleic Acids (DNA & RNA)– made of nucleotides. Provide the cell’s genetic instructions; also needed to make proteins. Starburst (Cherry only)- needed to rot your teeth and make you all hyper from too much sugar…seriously…why are you writing this down?

If We Decide You’re Alive…Then What? Well…you’ll (any organism actually) need four basic things: Water: Almost ever living thing consists of about 70% water. It’s needed for most chemical reactions that take place within an organism…and there are A LOT of them…reactions, that is 

2. A Source of Energy: These are called nutrients (some of those chemicals we talked about). You can make your own (if you’re an autotroph…such as most plants), or…you can eat another organism…your choice. Well…not really. 3. Maintain Homeostasis: Wow! That’s a big word! So, basically it means that organisms maintain their internal conditions (like temperature, respiration, blood pressure…in vertebrates). So like, if your body is hot…you sweat and that cools you off (that’s a simple example).

4. Physical Space: All organisms need someplace to exist 4. Physical Space: All organisms need someplace to exist. Don’t confuse this with “shelter!” There are plenty of living things that live in some crazy rough places like The Dead Sea, deserts, The Poles, boiling hot springs, and deep sea hydrothermal vents. Those are some crazeeee conditions, and shelter? That just ain’t happenin’ So…there you have it… 8 Criteria for Living Things and 4 Basic Needs