1.2 Biology is the science of life-
• Properties of living and non-living things: movement, complexity, and stimulation
• 5 fundamental properties of living organisms:
o Cellular organization
o Energy utilization
o Growth, development, and reproduction
• Hierarchical organization of living systems:
o Cellular level: atoms are joined together by chemical bonds into stable assemblies
called molecules. Large complex molecules are called macromolecules, an example
of this is DNA. Complex biological molecules are assembled into tiny structures
called organelles within which cellular activities are organized. The mitochondrion is
an organelle within which the cell extracts energy from food molecules. Membrane-
bounded united called cells are the basic unit of life.
o Organismal level: tissue is a group of similar cells that act as a functional unit. Nerve
tissue carried electrical signals. Tissues are then grouped into organs- body
structures composed of several different tissues that act as a structural and
functional unit. Organs are then grouped into organ systems, for example the
o Population level: individual organisms occupy several hierarchical levels within the
living world. The most basic of these is the population- a group of organisms of the same species living in the same place. All populations of a particular kind of
organism together form a species, its members similar in appearance and able to
interbreed. At a higher level of biological organization, a biological community
consists of all the populations of different species living together in one place.
o Ecosystem level: The highest tier of biological organization, a biological community
and the physical habitat (soil composition, available water, temp. range, wind, and a
host of other enviro. Influences) within which it lives together constitiute an
ecological system or ecosystem. The entire planet can be thought as a global
ecosystem that we call the biosphere.
• Emergent properties- novel properties arising from the way in which components interact.
They often can’t be deduced solely from knowledge of the individual components. For
example, water makes up 50 to 70 % of the human body’s weight and ice is also made up of
H2O but they are different in the way that one is a liquid and the other is a solid because the
H2O molecules are more organized.
1.3 Science is based on both observation and reasoning
• Descripted science: in