Aim: How did life begin ? HW11 Chap 17 History of Life Read pages Pg. 428 section 17-2 answer Q 1-4

Billions of years ago, life on Earth is thought by many scientists to have begun as simple, single organisms. About a billion years ago, increasingly complex multi-cellular organisms began to evolve.

Do Now:KWL (What is Life ?) KWL

Conditions of Primitive Earth H 2 He CH 4 NH 3

Evolution of the Present Atmosphere

The heterotroph hypothesis describes the possible change of the earth’s atmosphere to support life, as we know it.

Organic compounds are compounds found in living things. They contain carbon, Hydrogen and Oxygen Nucleic acids Carbohydrates Proteins Lipids

Stanley Miller's (and subsequent) experiments have not proven life originated in this way, only that conditions thought to have existed over 3 billion years ago were such that the spontaneous (inorganic) formation of organic macromolecules could have taken place.macromolecules

KWL Go back and fill in the L column

Aim: How do we define Life ? What do living things do that non-living things cannot do?

Life Functions Digestion - breakdown of food to simpler molecules which can enter the cells Circulation - the movement of materials within an organism or its cells

Life Functions Movement - (locomotion) change in position by a living thing Excretion - removal of waste products by an organism (wastes may include carbon dioxide, water, and urea in urine and sweat)

Life Functions Respiration - process which converts the energy in food to ATP (the form of energy which can be used by the cells) Reproduction - the making of more organisms of one's own kind -- not needed by an individual living thing but is needed by its species

Life Functions Regulation - the control of the various activities of an organism (mostly involves the nervous system and endocrine glands in complex animals) Synthesis - the production of more complex substances by combining two or more simpler substances

All living things perform life functions from the smallest organism to the largest Uni-cellular protozoan Whale Shark

Digestion

Circulation and Movement

Excretion

Respiration

Reproduction Paramecium Conjugation Marsupial birth

Regulation Phototropism in plant shoots

Synthesis All cells synthesize compounds for use in and out of the cell