Studying life What does it mean to be alive? How do Biologists study life?

Living understanding-cells-the- characteristics-of-life-video.htmhttp://videos.howstuffworks.com/hsw/ 8490-understanding-cells-the- characteristics-of-life-video.htm

To be alive you must - Reproduce. Genetic code. Grow, develop. Obtain and use energy. Respond to the environment. Maintain a stable internal environment. Change over time.

Reproduction Reproduction: to copy, to produce again… 1.Sexual reproduction: two cells from two organisms unite to produce one for one new organism. (two parents) 2.Asexual reproduction: a cell from a single organism divides to form the cell for a new organism. (one parent)

Genetic code Offspring must arise from an organism with similar genetic material. – DNA or RNA (in rare cases proteins) –A brown eyed mother and a blue eyed father produce a hazel eyed child. The genes for eye color are different but they share common human DNA- they are all three human!

Grow, Develop All living things grow during some part of the life span.

Obtain and Use Energy Metabolism: burning organic fuel to produce energy for life processes. All life gets its energy from the sun- some organisms collect sun energy directly (plants), some organisms eat organisms that collect sun energy (everything else).

Respond to the Environment Living things respond to stimuli (signals) from the environment. –Plants respond to light by? –Humans respond to eating lots of candy by?

Maintain an Internal Env. Homeostasis: process that living things use to maintain a stable internal environment. What happens when you cannot maintain a stable internal env? –Fever! –Hypothermia! –Dehydration! –Etc

Change Over Time All living things evolve.

Cells Smallest unit of life - all living things are made up of cells. Cell: collection of living material separated from the environment.

Questions?