Topic 1 Introduction to the Study of Life 1.1 The Unifying Characteristics of Life Biology 1001 September 9, 2005.

Topic 1Introduction to the Study of Life

1.1 The Unifying Characteristics of Life

Biology 1001September 9, 2005

Why Study Biology?

• Rooted in the human spirit

Curiosity, recreation, enjoyment of nature

Our connectedness to living things

Conservation of biodiversity important

E. O. Wilson’s biophilia

Why is Biology Important?

• Woven into the fabric of society

- Health and disease

- Nutrition

- Agriculture

- Management of natural resources

• Applicable in diverse disciplines

- Psychology, sociology, criminal science

- Even architecture!

Life Is A Myriad of Diverse Forms

So How Do We Recognize Life?Unifying Properties & Processes Characterize Living Things

• Order• Evolutionary adaptations

Cells as the basic unit of structure

DNA as the hereditary material

The study of life has both horizontal and vertical dimensions!

• Response to environment• Reproduction• Energy processing• Growth and development• Regulation and homeostasis

Figure 1.2 Some properties of life

(c) Response to the environment

(a) Order

(d) Regulation

(g) Reproduction (f) Growth and development

(b) Evolutionary adaptation

(e) Energy processing

Examples – Order & Energy Utilization

Examples – Reproduction, Growth & Development

A Hierarchy of Biological Organization

• The study of life– Extends from the microscope scale of molecules and

cells to the global scale of the entire living planet

• The hierarchy of life– Extends through many levels of biological

organization

• The challenge is integration across dimensions!

Figure 1.3 Exploring Levels of Biological Organization1 The biosphere

2 Ecosystems

3 Communities

4 Populations

5 Organisms

8 Cells

6 Organs and organ systems

7 Tissues

10 Molecules

9 Organelles

50 µm

10 µm

1 µmCell

Atoms

Cells

• A diversity of cell form!

• The cell– Is the lowest level of organization that can perform all activities

required for life

• All cells share certain characteristics– They are all enclosed by a membrane– They all use DNA as genetic information– They all contain a cellular fluid and ribosomes

• There are two main forms of cells– Eukaryotic– Prokaryotic

Cells

• Pro=first, eu=true, karyon=nucleus

• Eukaryotic cells– Are subdivided by internal membranes into various membrane-enclosed organelles– Nucleus, mitochondria, chloroplasts– All other organisms

• Prokaryotic cells– Lack the kinds of membrane-enclosed organelles found in eukaryotic cells– Are smaller than eukaryotic cells– Prokaryotes

Prokaryotic Vs. Eukaryotic Cells

EUKARYOTIC CELL

Membrane

Cytoplasm

Organelles

Nucleus (contains DNA) 1 µm

PROKARYOTIC CELL

DNA

(no nucleus)Membrane

Figure 1.8

DNA - The Cell’s Heritable Information

• Cells contain chromosomes made partly of DNA, the substance of genes– Which program the cells’ production of proteins and transmit

information from parents to offspring

Egg cell

Sperm cell

NucleicontainingDNA

Fertilized eggwith DNA fromboth parents

Embyro’s cells with copies of inherited DNA Offspring with traits

inherited fromboth parents

The molecular structure of DNAaccounts for its information-rich nature

DNA

Cell

Nucleotide

ACTA

T

A

CC

G

G

TA

TA

(b) Single strand of DNA. These geometric shapes and letters are simple symbols for the nucleotides in a small section of one chain of a DNA molecule. Genetic information is encoded in specific sequences

of the four types of nucleotides (their names are abbreviated here as A, T, C, and G).

(a) DNA double helix. This model shows

each atom in a segment of DNA.Made up of two long chains of building blocks called nucleotides, a DNA molecule takes the three-dimensional form of a double helix.

Nucleus

Feedback Regulation in Biological Systems

• A “supply-and-demand” feature regulates some of the dynamics of living systems

• The output, or product, of a process regulates that very process

Feedback can be Negative or Positive

In negative feedbackAn accumulation of an end product slows the process that

produces that product

In positive feedbackThe end product speeds up production

The Emergent Properties of Biological Systems

A system is a combination of components that form a more complex organization

Biological systems are much more than “the sum of their parts”

New properties emerge with each step upward in the hierarchy of biological organization

Examples of Emergent Properties

Non-Living Examples

• Graphite vs. diamond • NaCl

• A hammer

Biological Examples

• Ecosystems

• Feedback regulation

• Consciousness

• Photosynthesis

• Enzymes & other proteins

Systems Biology Systems biology seeks to create models of the dynamic

behavior of whole biological systems

With such models scientists will be able to predict how a change in one part of a system will affect the rest of the system

Is now taking hold in the study of life at the cellular and molecular levels

Includes three key research developments: high-throughput technology, bioinformatics, and interdisciplinary research teams

Examples of Systems BiologyCELL

Nucleus

Cytoplasm

Outer membraneand cell surface

Figure 1.10

CELL

Nucleus

Cytoplasm

Outer membraneand cell surfaceCELL

Nucleus

Cytoplasm

Outer membraneand cell surfaceCELL

Nucleus

Cytoplasm

Outer membraneand cell surface

Figure 1.10

2. A systems map of interactions between proteins

in a cell

1. The “greenhouse effect”

3. The Human Genome Project

Correlation Between Structure and Function at All Levels of Biological Organization