Life- How do we define life?

What do each of these things have in common?

6 Characteristics of Life Living things have cells A cell is a membrane covered structure that contains all the materials necessary for life. Unicellular organisms have one cell Multicellular organisms have more than one cell. Cells perform specialized functions

2- Living Things Sense and Respond to Change All organisms have the ability to sense change in their environment (stimulus) and to respond to that change. Stimuli can be chemicals, gravity, darkness, light, sound, smell, taste, temperature….. Ex.) Sweating (yuck!) is your body’s response to high temperatures (stimulus).

What is the stimulus and response in these pictures?

How do living things manage stimuli? Even though an organism’s external environment may change, the organism must maintain a stable internal environment in order to survive, called homeostasis Your body maintains an average temperature of about 98.6º F, (37ºC) How does it accomplish this?

3- Living Things Reproduce There are two main branches of reproduction Asexual reproduction involves a single parent (mostly unicellular), producing offspring which are identical to that parent.

Living Things Reproduce Sexual reproduction almost always requires two parents to produce offspring that will share characteristics of both parents. Most plants and animals reproduce in this way. Sperm cells on an egg

4- Living Things Have DNA DNA (deoxyribonucleic acid) is a special molecule which provides instructions for making proteins. These proteins take part in almost all of the organism’s characteristics. When organisms reproduce, they pass on copies of DNA to their offspring.

DNA is responsible for heredity Heredity is the transmission of characteristics from one generation to the next.

5- Living Things Use Energy Organisms use energy to carry out activities, such as, making food, breaking down food, building cells, and moving materials in and out of cells. An organism’s metabolism is the total of all of the chemical activities that it performs.

Describe some energy/organism relationships.

6- Living Things Grow and Develop Whether unicellular or multicellular, living things grow throughout their lives. Unicellular organisms increase their cell size, while multicellular animals increase their cell number.

Life keeps growing!!

In your journal, answer the following questions using your notes What characteristics of living things does a river have? Is it alive? What does the fur coat of a bear have to do with homeostasis? How is reproduction related to heredity? What are some stimuli in your environment? How do you respond to these stimuli?

Answers A river has energy (it moves) and can grow larger (after rain, or when snow melts). But, it is not alive because it not is made of cells, cannot respond to stimuli, has no DNA, and cannot reproduce. Homeostasis is the maintenance of a stable internal environment. The fur coat of bear helps it keep a stable temperature.

Answers Heredity is the passing of characteristics from parents to offspring. When organisms reproduce, offspring inherit copies of their parents’ DNA One example of a stimulus is thirst. I was really thirsty the other day, so I got a drink of water as soon as I could to replace the fluids in my body.

Characteristics of Life Review Questions Name four living and non-living things that you interact with daily. What do you do when you go outside and it is cold? How do people use technology to improve their ability to respond to environmental stimuli? Is your alarm clock a stimulus? Explain. Why is it important to respond to stimuli?