Wednesday, August 18, 2021

Characteristics of Living Things

Biology Index

Where are we going with this? The information on this page should increase understanding related to this standard: Compare and contrast existing models, identify patterns, and use structural and functional evidence to analyze the characteristics of life. Engage in argument about the designation of viruses as non-living based on these characteristics.

Article includes ideas, images, and content from Troy Smigielski (2021-08)

Characteristics of Living Things
(Huh… That seems like something we should know…)

In the classic horror movie, Frankenstein, (in some versions, at least) the mad scientist, as his created monster rises from the lab table, declares, "It's alive!"

How did he know?

What makes something alive? What is the criteria used to determine if something is or is not living?


We should discuss this!

The following are eight characteristics of living things.

Cells… Cells… Cells… An important aspect of being alive is being made of cells. (Not phones! Not rooms for detaining people. You know… biology cells.)

 1. All living things are composed of cells.
    • A cell is the smallest unit of life.

    • Every living thing is composed of at least one cell.

    • Some things are unicellular (such ad bacteria) and others are multicellular (for example, humans and trees).
      • unicellular: being composed of only one cell.
      • multicellular: begin composed of more than one cell.


2. Living things maintain a stable internal environment.

All living things can control their internal conditions to keep them at a point called homeostasis, which is the equilibrium point. (Wait! What is this thing you call homeostasis? We should define that!)

Homeostasis (Greek prefix "homoios" (ομοιος) meaning "same" and the English root "stasis" meaning state or condition) is the state in which something stays the same. If a store only allows 300 people inside and admits people only when others leave, then they are keeping homeostasis with regard to people inside. 

Examples: Body temperature, solute levels in bloodstream…


3. Living things need to acquire energy to survive.

Organisms must take in materials and energy to grow, develop, and reproduce.
    • Autotrophs are organisms that can make their own food. For instance, plants can make energy by means of photosynthesis.

    • Heterotrophs are organisms that get their food from a different source.


4. Living things evolve, change, and adapt (as a group) over time.

All living things can adapt to their surroundings causing changes over many generations. (ex: bacterial resistance to antibiotics).
For instance, only the genes for coloring in rabbits that help them survive in certain terrain would be passed on. 


5. Living things reproduce.

All living things can make more organisms either sexually (plants and animals) or asexually (bacteria).

Sexual reproduction: the production of new living organisms by combining genetic information from two individuals of different types (sexes). In most higher organisms, one sex (male) produces a small motile gamete which travels to fuse with a larger stationary gamete produced by the other (female). (Source)

Asexual reproduction: Asexual reproduction occurs when an organism makes more of itself without exchanging genetic information with another organism through sex. (Source, 2021-08-19

Following are the examples of asexual reproduction:

Bacterium undergoes binary fission in which the cell divides into two along with the nucleus.

Blackworms or mudworms reproduce through fragmentation.

Hydras reproduce through budding.

Organisms such as copperheads undergo parthenogenesis.

Sugarcane can be grown through vegetative propagation. 

(Source 2021-08-19) 


6. Living things are built on a universal genetic code.

All organisms use the same code to store their genetic information. It is stored in a molecule called DNA.


7. Living things grow, mature, and develop.

    • Each organism has a pattern of growth and development.

    • In humans, we start as one cell. That cell replicates via mitosis into 2 > 4 > 8 > 16 > 32… > 30,000,000,000,000


8. Living things respond to their environment.

Organisms detect and respond to stimuli from their environment. As things happen around it, a living organism can change. A plant may grow toward the light. A human may be startled and jump when hearing a loud noise. 

To be considered a living thing, an organism must have all eight of the characteristics of life.

And… That brings us back to Frankenstein's monster… Was it alive? Hmm… If not, which of the eight characteristics of living things did it lack?

Feel free to speculate and talk among yourselves!

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