What is Life Biologists are scientists who study

What is Life?

• Biologists: are scientists who study living things • • Characteristics of Living Things: Organisms are living things All organisms share six characteristics: (1) cellular organization, (2) contain similar chemicals, (3) use energy, (4) grow and develop, (5) respond to their surroundings, and (6) reproduce.

• (1) Cellular Organization • the cell is the basic unit of structure and function in an organism. • 2 categories of cells: unicellular (single cell) and multi-cellular (many cells) • Bacteria is the most numerous organism on Earth.

• (2) Chemicals of Life • Cells of all living things are composed of 5 chemicals. • Most abundant chemical is water. • Other chemicals are carbohydrates (cells energy source) • Proteins and lipids are the building materials • Nucleic acids are the genetic material that directs the cell’s activities.

• 3) Energy Use • The cells of organisms use energy to do what living things must do, such as grow and repair injured parts.

• 4) Growth and Development • Growth is the process of becoming larger • Development is the process of change that occurs during an organism’s life to reproduce a more complex organism.

• 5) Response to Surroundings • All organisms react to changes in their environment. • A change in the organism’s surroundings that causes the organism to react is called stimulus. • Stimuli include changes in temperature, light, sound, and other factors. • An organism reacts to a stimulus with a response – which is an action, movement or change in behavior of the organism

• 6) Reproduction • Another characteristic is reproduction, the ability to reproduce or produce offspring that are similar to the parents. • 2 types of reproduction: asexual and sexual. • Asexual: some living things reproduce from only one parent (bacteria, yeast, geraniums, African violets) • Sexual: requires two parents

The Needs of Living Things • All organisms need four basic things to stay alive. Living things must satisfy their basic needs for (1) energy • (2) water • (3) living space • (4) stable internal conditions

Energy • Autotrophs use the food they make as an energy source to carry out their life functions. • Heter means “other”(feeds off others) • Auto means “self” (makes its own food)

Water • ALL living things need water to survive. • Water makes up 92% of the liquid part of your blood. • Metabolism would come to a halt without water.

Living Space • Competition is the struggle among living things to get the proper amount of food, water, and energy. • Animals compete for space. • Plants compete for sunlight and water.

Stable Internal Conditions • Homeostasis is the ability to keep the inside condition of the body the same. • Animals are warm-blooded because they have a constant body temperature. • Cold-blooded animals change body temperature according to the outside temperature (fish and reptiles)