Introduction to Biology

1. Introduction
to Biology
NSCI101

2. Characteristics of
Living Things
It is not always an easy thing to tell the difference between living,
dead, and non-living things. Prior to the 1600's many people believed
that nonliving things could spontaneously turn into living things. For
example, it was believed that piles of straw could turn into mice. That
is obviously not the case. There are some very general rules to follow
when trying to decide if something is living, dead, or non-living.

3. 1. Living things
are made of cells
 Cell, from the Latin word
cella meaning “small room”, is
the basic structural, functional,
and biological unit of all known
living organisms.
 Cells are the smallest unit
of life that can replicate
independently, and are often
called “building blocks of life”.

4. 2. Living things
obtain and use
energy Living organisms need energy
to grow, develop, repair damage,
and reproduce.
 Autotrophs – organisms that
can make their own food. Ex.
Plants
• Photosynthesis is process
through which plants obtain
their energy.
 Heterotrophs – organisms that
cannot make their own food. Ex.
Animals
• Herbivore: plant eater
• Carnivore: flesh eater

5. 3. Living things grow and develop
 Unicellular organisms may stay as one cell but they
grow too.
 Multicellular organisms add more and more cells to
form more tissues and organs as they grow.
 Growth and development of living organisms are not
the same things.
• Growth is the increase in size and mass of that
organism.
• Development involves transformation of the organism
as it goes through the growth process.

6. 3. Living things grow and develop
 Mitosis is a part of the cell cycle in which chromosomes in
a cell nucleus are separated into two identical sets of
chromosomes, each in its own nucleus.
• Prophase: stage of mitosis in which the chromatin
condenses into double rod-shaped structures called
chromosomes in which the chromatin becomes visible.
• Pro-metaphase: the nuclear membrane breaks apart into
numerous "membrane vesicles", and the chromosomes
inside form protein structures called kinetochores.
• Metaphase: stage of mitosis in the eukaryotic cell cycle in
which chromosomes are at their most condensed and coiled
stage.
• Anaphase: the stage of mitosis when chromosomes are
split and the sister chromatids move to opposite poles of the
cell.
• Telophase: the nuclear membrane reforms, nucleoli
reappear, chromosomes unwind into chromatin.

7. 4. Living things reproduce
Sexual Reproduction
This involves two individuals of the
same species, usually a male and
female. Here the male and female sex
cells come together for fertilization to
take place. After this the newly
fertilized cell goes on to become a new
organism, the offspring. Note that not
all sexual reproduction involve mating.
Asexual reproduction
This form of reproduction occurs without
the involvement of another. Asexual
reproduction is very common in single cell
organisms and in many plants. There are
many forms of asexual reproduction.
Mitosis, fission, budding, fragmentation,
sporulation and vegetative reproduction
are all examples of asexual reproduction.
Reproduction is the process by which new organisms (offspring) are
generated. A living organism does not need reproduction to survive, but as a
species, they need that for continuity and to ensure that they are not
extinct. There are two main types of reproduction:

8. 5. Living things respond
to their environment
Response to stimuli is an important characteristic of life. Anything that
causes a living organism to react is called a stimulus (plural is stimuli)
Stimuli can be external or internal.
For instance, if you feel like going to the bathroom, it is an internal
stimulus that is controlled by the brain. If the sun comes up on a warm
day, it is an external stimulus that can cause a snake to come out and
bask. The ability of the organism to react is called ‘irritability’.
It helps the organism to stay in balance. Living organisms have some
senses (sight, smell, touch, taste, hearing) that help them to detect
changes in their external environment, as well their internal balance
and respond to them.
Some organisms (such as herbivores) respond to stimuli much quicker
than others (such as plants).

9. 6. Living things adapt to their environment
Homeostasis the ability of an organism to maintain balance in its internal
environment. It is achieved by a mechanism involving three components:
 The Receptor (or Sensor): Sensors on your skin can detect when the
temperature outside increases.
 The Control Center (Processor): The brain receives the signal from the
sensor and processes it (finds a solution).
 The Effector: Sweat glands get to work, and blood flow increases to
produce sweat, which cools the organism down. This way, the organism’s
original balance is restored.
Adaptation is the process that helps an organism survive in its environment.
For example, a polar bear will struggle to survive in a hot climate, because the
temperature will be too much for it. The polar bear's heavy fur is best suited for
colder regions, therefore we say that polar bears are adapted to colder
regions.

10. If something follows one or just a few of the rules listed above, it does
not necessarily mean that it is living. To be considered alive, an
object must exhibit all of the characteristics of living things. Sugar
crystals growing on the bottom of a syrup container is a good
example of a nonliving object that displays at least one criteria for
living organisms.

11. Principles of
Spontaneous Generation
and Abiogenesis
In modern science, it is understood that living things arise from
other living things. This is cell theory; the knowledge that cells (the
basic units of life) came from pre-existing cells. But life had to begin
at some point. So what is it that makes the discredited theory of
spontaneous generation a fallacy and abiogenesis solid science?

12. What Is Spontaneous Generation?
Spontaneous generation is the belief that, on a daily basis,
living things arise from nonliving material, and this idea was
entrenched throughout most of recorded history.

13. Aristotle's Thoughts on
Spontaneous Generation
Aristotle was one of the first to record his conclusions on the
possible transition from nonliving to living. According to
Aristotle, it was readily observable that aphids arise from the
dew on plants, fleas from putrid matter, and mice from dirty
hay; and this belief remained unchallenged for more than two
thousand years.

14. What Is Abiogenesis?
Spontaneous generation was not a theory that addressed the
origin of life, but instead, had been based on the belief that
living things commonly emerge from nonliving matter.
Although science ultimately established that living things
arise from other living things, the question remained…”Where
did the first living thing come from?” Abiogenesis is the
theory that addresses the actual origins of life on Earth.

15. Abiogenesis and Nucleic Acids
All living things have genetic instructions made of organic
molecules called nucleic acid. These instructions are
essentially the blueprint for each living thing. Therefore the
question of how life on Earth originated, the investigation of
abiogenesis, focuses on how the first nucleic acids came into
being.

16. Chemistry of Life
Life on earth depends on the chemical element Carbon, which is
present in every living thing. Carbon is so important, it forms the
basis for two branches of chemistry, organic chemistry and
biochemistry.

17. The Periodic Table
The Periodic Table is a chart which
organizes the chemical elements.
The elements are categorized
according to the following
attributes:
 Atomic Number - number of protons in the
nucleus
 Atomic Mass - sum of the number of protons
plus neutrons in the nucleus
 Group - columns or multiple columns in the
periodic table. Elements in a group share similar
chemical and physical properties.
 Period - rows from left to right in the period
table. Elements in a period have the same
number of energy shells.

18. Matter Structure
All substances consist of matter. Matter is anything which has mass and takes up space.
Some important concepts to remember about matter are:
Matter is made up of one or more of over 92 naturally-occurring elements. Each element
is a pure substance, made up of only one type of atom. An atom consists of three types
of particles:
 Electrons are negatively-charged particles,
 Protons have a positive charge, and
 Neutrons do not have an electrical charge.
An atom has an inner core called a nucleus, which is where the protons and neutrons
are located. The electrons orbit around the outside of the nucleus. Two main forces hold
atoms together:
 Electric force holds the electrons in orbit around the nucleus. Opposite charges
attract, so the electrons are drawn to the protons in the nucleus.
 Nuclear force holds the protons and neutrons together within the nucleus.

19. Chemical Formula
 Molecule - a molecule is a combination of two or more atoms (could be
from the same or different elements, such as H2 or H2O)
 Compound - a compound is a combination of two or more chemically-
bonded elements. Generally, compounds are considered to be a
subclass of molecules (some people will argue they are determined by
the types of chemical bonds).
A chemical formula is a shorthand way of showing the elements contained
in a molecule/compound and their ratio. For example, H2O, the chemical
formula for water, shows that two atoms of hydrogen combine with one atom
of oxygen to form a molecule of water.
Chemical bonds hold atoms together.
 Ionic Bond - formed when an electron transfers from one atom to
another
 Covalent Bond - formed when two atoms share one or more electrons

20. Phases of Matter
Each phase of matter has its own chemical and physical properties.
The phases of matter you need to know are:
 Solid - a solid has a definite shape and volume
 Liquid - a liquid has a definite volume, but can change shape
 Gas - the shape and volume of a gas can change

21. Phase Changes
These phases of matter can change from one to another. Remember the
definitions of the following phase changes:
 Boiling - boiling is when a substance changes from a liquid to a gas
 Melting - melting occurs when a substance changes from a solid to a
liquid
 Condensing - condensation is when a gas changes to a liquid
 Freezing - freezing is when a liquid changes to a solid

22. Physical and Chemical Changes
The changes that take place in substances may be categorized in two classes:
 Physical Change - does not produce a new substance (e.g., phase
changes, crushing a can)
 Chemical Change - produces a new substance (e.g., burning, rusting,
photosynthesis)
Solution – results from combining two or more substances. Making a solution
can produce either a physical or chemical change. You can tell them apart this
way:
 The original substances can be separated from one another if the solution
produces only a physical change.
 The original substances cannot be separated from one another if a
chemical change took place.