what is biology
study of life and living things
7 characteristics of living things
1) have cells
2) reproduce
3) DNA
4) grow/development
5) use energy
6) respond to surroundings
7) change over time
specialized cells
have specific roles and functions
homeostasis
maintain a stable internal environment
element
a pure substance made up of the SAME type of atom
atom
smallest unit of matter
molecule
two or more atoms bonded together. atoms may be the same or different
compound
a substance containing two or more different elements in a fixed ratio
valence electrons
electron on the outermost shell, involved in bond formation
covalent bond
when electrons are shared between atoms (2 electrons)
double covalent bond
when 2 pairs(4) electrons are shared
ionic bond
electrons are transferred from atom to another. results in the formation of ions
ions
atoms that have gained or lost electrons
ions that lose electrons are positive, ions that gain are negative
nucleus
center of an atom, made up of protons and neutrons
neutron
mass=1
no charge
proton
mass=1
positive charge
electron
no mass
negative charge
orbit the nucleus
which four elements make up 96% of the human body?
CHON
carbon, hydrogen, oxygen, nitrogen
all atoms of a particular element have
the same number of protons
the atomic number is equal to
the number of protons of an atom
the atomic mass equals the sum of
protons and neutrons
chemical bond
any time atoms share or transfer electrons
why do atoms form chemical bonds?
to fill their outer shells
hydrogen ion
H+
More of it makes a substance acidic
positive
hydroxide atom
OH-
makes substance more basic
negative
pH range of acids
0-6
pH range of bases
8-14
buffer
any solution that prevents sharp changes in pH
why do biological fluids contain buffers?
to prevent sharp changes in pH (in blood)
chemical reaction
bonds being made or broken
reactant
what goes into a chemical reaction
product
what comes out of a chemical reaction
hypothesis
Statement that predicts the likely outcome of an experiment.
scientific inference
a logical conclusion based on incomplete data and observations
scientific theory
explanation of why things happen
scientific law
statement of something that happens
backed up by a lot
independent variable
the group with the changed variable
dependent variable
the results (what is being recorded)
controls
group that is kept the same
7 levels of organizations starting at atom
atom molecule cell tissue organ organ system organism
sexual
offspring are genetically different
multicellular
asexual
offspring are genetically identical to their parents
unicellular
steps of scientific method
problem hypothesis experiment collect data conclude publish/share