CHAPTER 1 - INTRODUCTION - THEMES IN BIOLOGY
What is Biology?
• The study of life.
• Amultidisciplinary science that can be unified by some fundamental themes.
Theme 1 – New properties emerge at each level in the biological hierarchy
Biological organization is based upon a hierarchy of structural levels; each level has emergent
Complex biological molecules
The hierarchy extends beyond the individual organism (Fig 1.4)
Population localized group of organisms belonging to the same species
Community populations of species living in the same area
Ecosystem an energy processing system of community interactions that includes abiotic
environmental factors (e.g., soil, water)
Biomes major ecosystem types classified by predominant vegetation and distinctive
combinations of plants and animal
Biosphere sum of the earth's ecosystems 2
New properties emerge as you step up the biological hierarchy. These properties were absent
from the lower levels and are a reflection of the interactions between the components
contributing to the make up of each organizational level (“The whole is much greater than the
sum of its parts.”). These properties are called emergent properties (Fig 1.3).
Scientists studying life often use a combination of two approaches to tackle the complexity of
Holism = the principle that a higher level of order cannot be explained by examining the
component parts in isolation. Systems biology attempts to address the complexity of living
things by modeling the dynamic behavior of whole biological systems through the study of
interactions among the system parts.
Reductionism = The principle that a complex system can be understood by studying the
Theme 2 - Organisms interact with each other and their environment
• Organisms are open systems that continually interact with their environments (biotic and
• Both organisms and environment are affected by the interactions between them.
Theme 3 - Life requires energy transfer and transformation
• All living things must perform work, which requires energy – they use energy to carry out
• Living systems often transform energy from one form to another
• Ecosystem dynamics include two major processes: nutrient cycling and energy flow. (Figure
• Energy flows from sunlight to producers to consumers
Theme 4 – Structure and Function are correlated at all levels of biological organization
• Form fits function
• Knowing structure gives insights into how it functions and vice versa
Theme 5 – Cells are the basic unit of structure and function for all life on Earth
• The title of this course is “The Cellular Basis of Life”
• Recall the Hierarchy of Biological Organization – In this hierarchy, life exists at the cellular
level and the levels above in the hierarchy
2 Reece et al. 9 Edition
Important developments and individuals in the discovery of the cellular basis of life
• Invention of the light microscope in the 17th century made the study of cells possible.
• Robert Hooke (1665) - Coined the term cell.
• Anton van Leeuwenhoek - used a microscope (300 x) to observe blood cells, sperm cells and
living cells found in pond water. Reported the discovery of protozoa (1674) and bacteria
• Schleiden (botanist - 1838) and Schwann (zoologist -1839) are credited with the development
of the cell theory:
1. cells are the universal building blocks of all forms of life.
2. all living cells are formed by the division of existing cells
Common features of all cells
• enclosed in membranes
• all cells use DNA as their genetic information.
Two major types of cells distinguished on the basis of structural organization
Prokaryotic (before nucleus) cell Eukaryotic (true nucleus) cell
• Domains: Bacteria &Archaea ▯ Domain: Eukarya
• Kingdoms:… ▯ Kingdoms: Protista, Plantae, Fungi,Animalia
• no membrane bound nucleus ▯ membrane bound nucleus
• no membrane bound organelles ▯ membrane bound organelles
• least complex ▯ most complex
• generally smaller than eukaryotic cells ▯ generally larger than prokaryotic cells
Theme 6 – The continuity of life is based on heritable information in the form of DNA
• Order requires information and the cellular information for living systems is
deoxyribonucleic acid (DNA; Figure 1.11)
The genetic code is nearly universal
Gene expression -
Theme 7 – Feedback mechanisms regulate biological systems
• Regulatory mechanisms ensure a dynamic balance in living systems.
• Cells are complex entities with many chemical processes occurring simultaneously.
• Order is maintained by regulatory processes that control when, where, and how fast certain
reactions occur in the cell.
Many of the processes are self-regulating
• Negative feedback – output or end product slows the process (Figure 1.13)
• Positive feedback – output or end product accelerates the process (Figure 1.13)
Theme 8 - The Core Theme - Evolution
• Evolution is the one unifying biological theme - species change over time.
• Evolutionary theory provides a plausible explanation for the diversity of life on earth as well
as the similarity (i.e., unity) of all life on earth.
Diversity of Life
• >1.8 million species have been identified.
• Despite this great number of species all these organisms are related.
Organisms are grouped into categories on the basis of similarities. Taxonomy is the branch of
biology concerned with the naming and classification of organis