Chapter 2 Section 2 –Necessities of Life

4 Necessities of Life Water (Most chemical reactions for “metabolism” – all organisms activities, including getting energy from food, growing. etc – requires water. May get from food.) Air (Need for chemical process to get energy from food. Some organisms (anaerobic) do not need air; some types of bacteria are examples.) Shelter (Actually means having a place to live with access to all needs.) Food (Need to have energy and materials to carry out life processes.)

Competition Organisms often have to compete for food, water, shelter or other necessities.

“Making” vs. “Taking” Food Producers: Make their own (produce) food via photosynthesis Consumers: Must eat other (consume) organisms to get food Types of Consumers: Herbivores (eat producers; ex: zebra) Carnivores (eat consumers; ex: lion) Omnivores (eat both; ex: brown bear) Detritivores (eat dead organisms; ex: vulture) Decomposers (detritivores that break down complex molecules in dead tissue/ wastes into simpler molecules; ex: mushrooms)

Putting It All Together All organisms need to breakdown food to get/use nutrients. Nutrients are made of molecules (substance made of >2 atoms). Organisms’ molecules mostly made from 6 elements: carbon / hydrogen / nitrogen / oxygen / phosphorus / sulfur Elements combine to make: proteins/ carbohydrates / lipids / ATP / nucleic acids

Proteins Necessary for almost all life processes of cell Made of amino acids (smaller molecules) Many functions: Some form structures (hair, spider webs) Some help cells do jobs ( hemoglobin delivers oxygen thru body) Some are enzymes (speed chemical reactions) Needed to build and repair the body

Carbohydrates (Carbs) Made of sugars Provide and store energy Simple Carbs Made from 1 sugar or just a few sugar molecules Examples: table sugars and fructose (sugar in fruit) More common than complex carbs Complex Carbs Made from 100’s of sugar molecules which are linked Example: potato starch

Lipids Molecules that cannot mix with water Have many jobs Some store energy Fats - animals Oils – plants Phospholipids Make cell membranes Pair up; “heads” attracted to water, and “tails” avoid water

ATP Molecules called Adenosine Triphosphate Job: major energy carrying molecule of cells Energy from carbs or lipids are transformed to ATP to provide fuel

Nucleic Acids Molecules that carry directions for how to make proteins Made of smaller molecules called nucleotides Sequence stores information DNA is an example of a nucleic acid which directs making proteins

Additional Information For additional information…especially chemistry…go to http:\\my.hrw.com . User name: minerva13 password: minerva Then visit the visual concepts for Ch 2 Section2