Biology- is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Characteristics of Life
1. Living Things are Composed of Cells:
* Single-cell organisms have everything they need to be self-sufficient. * In multicellular organisms, specialization increases until some cells do only certain things. 2. Living Things Have Different Levels of Organization:
Both molecular and cellular organization.
Living things must be able to organize simple substances into complex ones. Living things organize cells at several levels:
* Tissue - a group of cells that perform a common function. * Organ - a group of tissues that perform a common function. * Organ system - a group of organs that perform a common function. Organism - any complete living thing.
3. Living Things Use Energy:
* Living things take in energy and use it for maintenance and growth. 4. Living Things Respond To Their Environment:
* Living things will make changes in response to a stimulus in their environment. * A behavior is a complex set of responses.
5. Living Things Grow:
* Cell division - the orderly formation of new cells.
* Cell enlargement - the increase in size of a cell. Cells grow to a certain size and then divide. * An organism gets larger as the number of its cells increases. 6. Living Things Reproduce:
* Reproduction is not essential for the survival of individual organisms, but must occur for a species to survive. * All living things reproduce in one of the following ways: - Asexual repoduction - Producing offspring without the use of gametes. - Sexual reproduction - Producing offspring by the joining of sex cells. 7. Living Things Adapt To Their Environment:
* Adaptations are traits giving an organism an advantage in a certain environment. * Variation of individuals is important for a healthy species. Atom- The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. Molecules- the smallest physical unit of a substance that can exist independently, consisting of one or more atoms held together by chemical forces. Proton- a stable elementary particle of the baryon family that is a component of all atomic nuclei and carries a positive charge equal to that of the electron's negative charge. Electron- a stable negatively charged elementary particle with a small mass that is a fundamental constituent of matter and orbits the nucleus of an atom. Neutron- a neutral elementary particle of the baryon family with a zero electrical charge and a mass approximately equal to that of a proton. Proton Number(Atomic Number)- the number of protons in the nucleus of an atom of an element and its isotopes, used to determine that element's position in the periodic table. Mass Number- the number of protons and neutrons in the nucleus of an atom of a particular substance. Dalton(Atomic Mass Unit)- a unit used to express the masses of atoms and molecules, equal to one-twelfth of the mass of a carbon-12 atom or about 1.660 x 10-27 kg. Symbol-u Characteristics of Molecular(Electron) Shell- "1 shell" (also called "K shell"), followed by the "2 shell" (or "L shell"), then the "3 shell" (or "M shell"), and so on further and further from the nucleus. The shell letters K, L, M, ... are alphabetical. Each shell can contain only a fixed number of electrons: The 1st shell can hold up to two electrons, the 2nd shell can hold up to eight electrons, the 3rd shell can hold up to 18, and 4th shell can hold up to 32 and so on. Since electrons are electrically attracted to the nucleus, an atom's electrons will generally occupy outer shells only if the more inner shells have already been completely filled by other electrons. However, this is not a strict requirement: Atoms may have two or even three outer shells that are only...