Science NotesFriday 8/29

Characteristics of Life

How do we know something is living? We see living things around us every day – we are a living thing. How would you define “life”?

Scientists generally agree that all living things share a few characteristics that make them alive.

These characteristics include: Cellularity, acquiring and using energy, growth, responding to the environment, homeostasis, and reproduction.

Cellularity

The “cell” was named by Robert Hooke after he observed cork material under a microscope and determined the small components of the material to look similar to the cells monks lived in at a monastery.

All living things are composed of at least one cell. The cell is the smallest unit of life, and is able to carry out the most basic functions of life. Cells obtain and use energy, they maintain a constant internal environment by eliminating wastes and toxins, and they reproduce to form new cells. Cells can also repair themselves. We will be learning about cells this next week in class.

Acquiring and Using Energy

Metabolism – this is the chemical process that living things use to break down the energy that they take in from their environment so that it is usable to them as they carry on their life activities. As humans, we eat a sandwich, and then our body breaks that sandwich down with enzymes and acids to create usable energy in the form of ATP. Below is a link that briefly describes metabolism, something we will be looking at in more detail as the year progresses.

http://highered.mheducation.com/sites/0073522732/student_view0/chapter4/animation_-_digestion_metabolism_overview.html

All living things can “eat” – that is, they can seek out and get energy from the environment around them and then use this energy to carry on their daily activities.

Growth

We will be examining cell growth and division (reproduction) as the quarter progresses. For an early start, you might want to take a look at the link below which describes how cells reproduce and grow normally:

http://www.cancerresearchuk.org/cancer-help/about-cancer/what-is-cancer/cells/how-cells-and-tissues-grow - how_cells_reproduce

All living things have the ability to grow, often changing form as they go through this process. During growth, multicellular organisms add more cells to their body form, and these cells begin to “differentiate”, or change into specific cell types that have specific jobs for the body. Even single-celled organisms grow, as cells grow in size and complexity.

Responding to the EnvironmentAll living organism have the ability to respond to stimuli (conditions, objects or other things that are encountered by organisms in their environment) as they exist in their environment. This allows living things to adapt, evolve (or change) with changing environmental conditions. Thus living things can maintain consistency in their environment and protect themselves from harmful situations.

HomeostasisThis word is derived from the Latin language: “homoe” – like or similar and “stasis” – standing or state. Homeostasis refers to a living object’s ability to maintain a stable internal condition despite changing environmental conditions around it. Although the Montana winter gets very cold, you body still maintains and internal temperature of 98.6° F or 37° C.

You sweat to maintain your internalbody temperature on a hot day.

ReproductionAll living things can reproduce more of themselves. A cell can make another cell, and a female dog can have puppies. We will examine both sexual and asexual reproduction in class, but first we will examine how the cell reproduces through mitosis.