Chapter 15-1 & 15-2 THE BASIC UNIT OF LIFE— THE CELL

Characteristics of Life All living things: use energy develop and grow maintain themselves can reproduce are part of evolving populations

All living things use energy. Plants use electromagnetic energy from sunlight. Animals convert food energy from plants or other animals into chemical energy. How living things use energy is consistent with the laws of physics.

All living things develop and grow, changing over time. Unicellular organisms go through division and cell change over time Most multicellular organisms begin as 1 cell and become many cells, often having specialized tissues.

Living things also maintain themselves. They build structures (bones, stems). They repair damage (immune system). They maintain an internal environment that is consistent (body temperature, ion balance), this is known as Homeostasis.

All living things are capable of reproducing. Asexual reproduction occurs when an organism reproduces by itself. Sexual reproduction occurs when organisms produce sperm and eggs that join to form new individuals. Sexual Reproduction creates Variation.

All living things are part of populations that evolve. Populations do not remain constant. Populations change over time, across generations.

Macromolecules Needed for Life Proteins (C,H,O,N,& S) Carbohydrates (C,H,O – 1:2:1) Lipids (C,H,O, - little O) Nucleic acids (C,H,O,N,P)

Importance of Macromolecules As stated last semester macromolecules are important to living things because: They help to construct cell organelles and tissues. Provide energy for life processes Used in hair, feather, nails, muscles, and cell movement. Lubricate and cushion cells, and help to make other chemicals like hormones. Storage of genetic information.

Cell Types Prokaryotic cells have no nucleus. Prokaryotes are almost always single-celled microscopic organisms. * Their DNA is found in a single circular chromosome. They usually have an outer cell wall. Many have a 2nd small circular Chromosome with extracellular DNA called a plasmid.

Cell Types They: contain their DNA inside the nucleus Eukaryotic cells have a nucleus and may be single celled or multicellular. They: contain their DNA inside the nucleus have linear chromosomes contain organelles are larger cells than prokaryotes