Characteristics of Life Mrs. Stewart Honors Biology I

Objectives  Define life in terms of the scientific characteristics that identify living organisms  Evaluate specimens for those characteristics  All living things are composed of cells that perform the necessary functions of life Standard:

What is biology? Biology Life Study of

Define Life Biologists have formulated a list of characteristics by which we can identify and classify living vs. non-living specimens

Characteristics of Life  Cells and Organization  Homeostasis  Response to Stimuli  Metabolism  Growth and Development  Reproduction  Changes over time (adaptation) ***Organisms must have all seven characteristics in order to be considered alive***

Cells  Basic units of structure and function for all living things  Every organism consists of at least one cell  Organism = an individual that possesses all characteristics of life

Cells and Organization Unicellular – made up of only one cell Multicellular – consist of more than one cell

Levels of Organization - Living things have order and complexity not found in lifeless objects. Living things are organized on several levels. Each level higher up on the hierarchy represents an increase in complexity.

Think – Pair - Share Monkeys – summarize the heirarchy of organization found in complex organisms to your dog

Think – Pair - Share Dogs – Both cells and organisms share the characteristics of life. Tell your monkey how cells and organisms different.

Response to stimuli  Organisms respond to a stimuli in order to maintain homeostasis  Senses: make observations that lead to responses Reflexes: unconscious responses to stimuli Behaviors: learned and instinctive responses to stimuli

Stimulus = a physical or chemical change in the internal or external environment. Light Temperature chemical mechanical

Think – Pair – Share  Dogs  Give an example of a reflex response to stimuli  Monkeys  Give an example of a learned behavior response to stimuli

Homeostasis  Ability to maintain a stable internal environment  Examples:  Heart rate  Body temperature  pH levels  Water levels  Others?  Homeostasis – body temperature explanation Homeostasis – body temperature explanation

Think – Pair – Share  Brainstorm together: why is homeostasis important for an organism’s survival?

Metabolism  The sum of all chemical reactions in the body  Some substances are broken down to yield energy and some substances are synthesized, which requires energy.

Metabolism (aka: energy use)  Organisms obtain energy by one of 2 methods:  Autotrophic – organisms that make their own food that they will then convert into energy (ex: photosynthesis)  Heterotrophic – organisms that must take in food from an outside source to convert into energy (examples???)

Growth  Growth occurs in two ways:  1) cell enlargement – gets bigger  2) cell division (reproduction) – cells split to produce more cells

Development  Development: process by which an organism becomes a mature adult through cell differentiation, or specialization.

Reproduction  Process by which an organism produces offspring Asexual -One parent -Genetically identical offspring (Examples: budding & fission) Sexual -requires 2 parents -genetically different offspring -sex cells from each gender join

Heredity  Living things inherit traits from their parent(s)  Genes = basic unit of inheritance  DNA molecules contain genes that code for proteins which are important for proper functioning of an organism

Change through time  Adaptations – changes made by a population in response to the environment in order to survive.  Why do organisms adapt?  SURVIVAL

Assignment  Characteristics of life Scavenger Hunt

Reflection- Exit Ticket  Which of the 7 characteristics do you think is the most important one to define life.  Explain your choice.