INTRODUCTION
CHAPTER 1
THE SCIENCE OF LIFE
WHAT IS BIOLOGY ?
According to Webster: “ Biology is the study of animals and plants; of their physical and
other characteristics, their habits and mode of life generally. Their genealogical relations one
to another. The distribution of the various genera and species over the Earth. The facts
concerning their birth and as far as is ascertainable, of the origin of LIFE itself.”
“It has been estimated that 40 million species of organisms inhabit the Earth, but only 2
million of these species have been studied so far. Thus much of the world of Biology remains
to be explored and studied. Fortunately, there are guideposts to help chart a course through
this vast and fascinating world. These guideposts are the six unifying themes of Biology.”
THE STUDY OF LIFE.
The first life probably arose on Earth more than 3.5 BILLION years ago.
Most of the evidence suggests that these first organisms were single celled.
These microscopic creatures dominated the planet for millions of years.
Ultimately they began to change, and “new” organisms began to appear.
The microbial organisms and the macro-organisms make of the diverse population of the
planet that we call EARTH.
Biology is the study of ALL living things.
The science of Biology is itself, a diverse subject.
This science is unified by certain themes that come into play no matter what kind of organism
or interaction is being studied.
The SIX unifying Themes
Cell Structure and Function
Stability and Homeostasis
Reproduction and Inheritance
Evolution
Interdependence of Organisms
Matter, Energy and Organization
CELL STRUCTURE AND FUNCTION
The cell is the basic unit of all life.
Organisms are either UNICELLULAR or MULTICELLULAR.
Cells are small but they are highly organized.
While there are many different types of cells, they are ALL similar in several ways.
Cellular Similarities
All cells are surrounded by a membrane.
All cells contain a set of instructions necessary for making new cell parts, new cells and
chemicals. These instructions are in the form of GENETIC MATERIAL.
In Multi-cellular organisms, certain cells take on particular functions. This is called
DIFFERENTIATION.
Examples. Nerve cells, Excretory cells, Muscle cells, etc.
STABILITY AND HOMEOSTASIS
All living organisms must maintain a very stable set of internal conditions in order to survive.
This stable level of internal conditions is called HOMEOSTASIS.
Examples of items that must be stable:
temperature, blood pressure, salt and water levels.
REPRODUCTION AND INHERETANCE
Reproduction is the ability to produce new organisms.
This can be through sexual or asexual means.
Reproduction is the method by which organisms transmit hereditary information to the next
generation.
This information can be contained in either DNA or RNA.
SEXUAL REPRODUCTION
The hereditary information that is passed is from two sources.
It can come from two
parts of a single organism, OR it can come from two separate organisms of the same
species.
The new generation has one half or its genetic material from each parent.
Provides for greater genetic variability
ASEXUAL REPRODUCTION
The hereditary information from different individuals is NOT combined.
In this type of reproduction you get two daughter cells (organisms) that are IDENTICAL to
the mother.
EVOLUTION
 Definition of Evolution: “a change.”
 Populations of organisms CHANGE over generations.
 These changes can be in response to environmental conditions, competition for food and /
or mates, changing habitats, etc.
 It has been suggested that the driving forces of these factors is called NATURAL SELECTION.
NATRUAL SELECTION
 According to the theory of EVOLUTION BY NATURAL SELECTION, The changes that
occur within the population as a result of environmental influences produces favorable traits
that make the organisms better suited to the current conditions.
 These changes make the organisms that carry the favorable trait better able to reproduce than
those organisms that do not have the trait.
 Ultimately NATURAL SELECTION IS DRIVEN BY COMPETITATION.
INTERDEPENDENCE OF ORGANISMS
 The study of individual organisms is an important part of biology.
 However, it is becoming more apparent that to fully understand the biology of the world We
must study and attempt to understand the interactions between organisms And their
interactions with the environment.
 This revelation has given rise to ECOLOGY.
ECOLOGY
 This is the study of the interactions between the various organisms that exist in a
habitat, as well as the interactions that exist between the organisms and the
Environment.
 To survive, Organisms need substances from the environment (nutrients, water and gases).
 The stability of the environment is dependent of the healthy functioning of the organisms
in that environment.
EVERYTHING LIVING THING ON THE EARTH DEPENDS UPON ALL OF THE
OTHER LIVING THINGS ON THE EARTH TO CONTINUE TO SURVIVE!
Example: Deforestation, over fishing, pollution of the water.
MATTER, ENERGY AND ORGANIZATION
All living things have highly organized structures that MUST be maintained in their
orderly state by a constant supply of energy.
How organisms obtain, use and transfer energy is a major topic in Biology.
AUTOTROPHS
All of the energy on the planet has its origins from the sun.
Organisms that use the sun’s light (energy) to make their own energy are called
AUTOTROPHS.
PLANTS (PHOTOSYNTHESIS)
BACTERIA (CHEMOSYNTHESIS)
HETEROTROPHIS
Organisms that utilize Autotrophs to get their energy are called HETEROTROPHS.
MAMMALS (FROM Plants, and other Animals).
THE CIRCLE OF LIFE
The nutrients that an organism contains are returned to the environment when the
organism dies and decomposes.
This means that all of the nutrient material (matter) that was here when the earth was
formed is still here in some manner.
The 7 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:
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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.