7 Characteristics of Life
Introduction: For many centuries, and longer, people have argued about the characteristics that separate life from non-life. While some of these arguments are unresolved, there are seven characteristics of life that are generally accepted. Anything that possesses all seven of these characteristics of life is known as an organism.
1. The scientific term for a living thing is _____________________________________.
Directions: Read each of the following sections below and answer each of the questions.
1. ORGANIZATION AND ORDER – MADE OF ONE OR MORE CELLS All living things are organized. The smallest unit of organization of a living thing is the cell. A cell is a collection of living matter enclosed by a barrier known as the plasma membrane that separates the cell from its surroundings. Cells can perform all of the functions associated with life. Cells are organized and contain specialized parts for particular functions. Cells are very different from each other. A single cell by itself can form an entire living organism. Organisms consisting of a single cell are called unicellular. For example, bacteria are unicellular. However, most organisms that humans are familiar with, such as dogs and trees, contain many cells – they are multicellular. Multicellular organisms contain hundreds, thousands, even trillions of cells. Multicellular organisms may have their cells organized into tissues, organs, and systems with specific functions in the body. Whether it is unicellular or multicellular, all structures and functions of an organisms come together to form an orderly living system. Functional cells are not found in nonliving matter. Structures that contain dead cells or pieces of cells are considered dead. For example, wood from a tree is made mostly from the cell walls of cells that are no longer functional.
2. All living things are ____________________________________________________.
3. What is the simplest level at which life can exist?
4. What is the function of the plasma membrane?
5. What is the difference between a unicellular and a multicellular organism? Give an example of each.
6. Multicellular organisms can be organized into what other levels?
2. REPRODUCTION All life must be capable of producing offspring – having “children.” To reproduce, new individuals are created from existing individuals. Organisms do not live forever, and must replace themselves. Not only is reproduction essential for an organism’s survival, it is also essential for the survival or the organism’s species. Some organisms use asexual reproduction to reproduce. These organisms make a copy of themselves without the help of other individuals. Other, more familiar organisms reproduce through sexual reproduction that requires two cells to unite (sperm and egg) to form the first cell of the new organism.
7. Define reproduction:
8. What is the major difference between the two main types of reproduction?
3. GROWTH AND DEVELOPMENT All organisms begin as single cells. Over time, organisms grow and take on characteristics of their species. Growth is the result of an organism increasing the amount of material it is made of and the formation of new structures. Unicellular organisms may change little over the course of their lives, but they do grow, while multicellular organisms will often produce more cells. Consider how you, or other humans, have grown, and changed, over the course of your life. All of the changes that take place during the life of an organism are known as development. A snowball grows when you roll it in fresh snow! Why isn’t it a living thing? The growth of the snowball does not come from inside, but from outside. It does not grow from producing more cells; it just adds more snow to the outside. Someone has to roll the snowball. It will not grow bigger by sitting in the snow, and cannot change either water or ice into new snow to help it grow larger. This is one of the differences between living things and nonliving things.
9. How do all organisms begin life?
10. Define growth:
11: Define development:
12: What is the difference between growth and development?
13. How is growth of a living thing different from growth of a nonliving thing?
14. Label which graphic BEST shows growth. Label which graphic BEST shows development?
4. OBTAIN AND USE ENERGY – ENERGY PROCESSING Energy is the ability to do work, or make things change. Energy is important because it powers life processes. It provides organisms with the ability to maintain balance, grow, reproduce, and carry out other life functions. Some organisms obtain energy from the food they eat, while other organisms, like plants, obtain energy from the food they make. Organisms that get energy from the food they eat are called heterotrophs. Organisms that use energy from the sun to produce their own food, like plants, are called autotrophs. Energy does not only flow through individual organisms, but also flows through communities of organisms, ecosystems, and determines how organisms interact with each other and their environment.
15. Define energy:
16. Why is energy important to a living organism?
17. What is the difference between an autotroph and a heterotroph?
18. Identify each of the organisms below as an autotroph or heterotroph.
5. RESPOND TO A STIMULUS – RESPOND TO THE ENVIRONMENT Living things live in constant connection with the environment, which includes the air, water, weather, temperature, any organisms in the area, and many other factors. These external factors act as stimuli and can cause a response from living things. Organisms need to respond to these changes in order to stay alive and healthy. For example, if you go outside on a bright summer day, the sun might cause you to sprint. This is your response to a particular environmental stimulus. Just as you are sensing and responding to changes in your environment, other organisms are also responding. In another example, a specialized leaf of the Venus flytrap senses the footsteps of a fly and responds by rapidly folding its leaves together in order to eat the fly.
19. What are some external environmental factors that organisms respond to (at least three)?
20. Give two examples of how living things respond to changes in their environment.
6. MAINTAIN HOMEOSTASIS Not only must an organism respond to changes in the external environment outside of its own body, but it must respond to internal changes within its own body. Internal conditions include the level of water, nutrients and minerals inside the body. These conditions also include body temperature and hormone levels. Small adjustments to internal changes help organisms maintain a stable internal environment. The regulation of an organism’s internal environment to maintain conditions suitable for life is called homeostasis. This can also be thought of keeping everything in balance! For example, you have a “thermostat” in your brain that responds whenever your body temperature varies, even slightly, from 98.6οF (37οC). If this internal thermostat detects a slight increase in body temperature, maybe on a hot day, the brain signals your skin to produce sweat which helps cools the body. If the thermostat detects a slight decrease in body temperature, the brain signals for muscles to shiver which helps warm the body. Methods of homeostasis help organisms to regulate their internal environment despite changes in their external environment. 21. What are some internal environment factors that organisms respond to (at least three)?
22. Define homeostasis:
7. EVOLUTIONARY ADAPTATION Individual organisms of a species may change during their lifetime; however, the basic traits they inherited from their parents usually do not change. As a group, however, any species can evolve, or change over time. Life can evolve, or change, in response to interactions between organisms and their environment. Over a few generations change may not appear to be significant, however over a very long period of time this change may be dramatic. These changes are due to changes in the genetic material of the organism, the DNA. Instructions in the DNA determine the inherited traits of an organism, or their features that are passed from parents to offspring.
Describe the relationship between evolution and DNA.
Identify the characteristic of life that is illustrated by each of the following statements. (Note! Do not write the number of the characteristic, but the name of the characteristic)
1. ________________________________ “That boy shot up five inches in one year!”
2. ________________________________ “Our cat had a litter of kittens yesterday!”
3. ________________________________ “My dog has become much less clumsy now that he is a year old.”
4. ________________________________ “Eat a good breakfast and you will be able to run longer.”
5. ________________________________ “When the car pulled into the driveway, my cat ran to hid under the porch.”
6. ________________________________ “That owl’s night vision allows it to see the movement of mice on even the darkest nights.”
7. ________________________________ “Single-celled organisms live in the pond behind the school.”
8. ________________________________ “Your body uses hormones to adjust internal sugar levels after eating.”
9. ________________________________ “Hummingbirds have long, thin beaks to reach the nectar inside flowers.”
Poster: Create a poster that represents the seven characteristics of life. Remember in creating your poster, that posters should be eye catching, neat, colorful and include only needed words. Be certain to include the following items to receive full credit:
1. Include each of the seven characteristic of life
2. Define homeostasis, evolution, and growth
3. Include color pictures to represent each of the seven characteristics of life
4. Include a clear and simple title