Birgit Woelker, PhD

Chapter 1

Biology: Exploring Life

THE SCOPE OF BIOLOGY Life’s levels of organization define the scope of biology

1. Biosphere

2. Ecosystem

3. Community

4. Population

5. Organism

6. Organ system

7. Organ

8. Tissue

9. Cell

10. Organelle

11. Molecule Atom

Nucleus

Brain

Spinal cord

Nerve

1 2

3 4

6 5

7 8

9 10

11

Living organisms and their environments form interconnecting webs

•  Ecosystems are characterized by the cycling of chemical nutrients from the atmosphere and soil

–  To producers to consumers to decomposers and back to the environment

•  Energy flows one-way through an ecosystem

–  From the sun to producers to consumers and exits as heat

Sun

Air

CO2

O2 CO2

H2O

Chemical energy

Inflow of

light energy

Loss of

heat energy

Producers

Cycling of

Chemical nutrients Consumers

Decomposers

Soil

Ecosystem

Figure 1.2

Cells are the structural and functional units of life

•  A cell

–  Is the basic unit of life

•  New proper ties emerge

–  From the complex organization of a system, such as a cell

•  All cells contain:

–  DNA

–  Cell membrane

–  ribosomes

•  Eukaryotic cells

–  Contain membrane-enclosed organelles, including a DNA-containing nucleus

•  Prokaryotic cells

–  Lack such organelles

Eukaryotic cell

Prokaryotic cell DNA

(no nucleus) Membrane

Organelles

Nucleus (membrane-

enclosed) DNA

(throughout nucleus)

EVOLUTION, UNITY, AND DIVERSITY

The unity of life: All forms of life have common features

•  DNA is the genetic information

–  For constructing the molecules that make up cells and organisms

•  Each species’ genetic instructions

–  Are coded in the sequences of the four building blocks making up DNA’s two helically coiled chains

A

C

T

A

T

A

C

C

G

T

A

G

T

A

CG

C G

C G

C G

C

G

A T

AT

A TA T

AT

A

T

•  All organisms share a common set of features

–  Ordered structures

–  Regulation of internal conditions

Figure 1.4B Figure 1.4C

–  Growth and development

–  Energy use

–  Response to environmental stimuli

–  The ability to reproduce and evolve

Figure 1.4D Figure 1.4E

The diversity of life can be arranged into three domains

•  Organisms are grouped (classified)

–  Into the prokaryotic domains Bacteria and Archaea and the eukaryotic domain Eukarya

Diversity of Life:

Living Things are categorized into

3 Domains: Bacteria

Archaea

Eukarya

Within the Domain of the Eukarya,

we distinguish :

4 Kingdoms: Plantae

Fungi

Animalia

Protista

SE

M 2

5,00

0!

Figure 1.5B

•  Domains Bacteria and Archaea

SE

M 3

,250!

Figure 1.5A

•  Domain Eukarya includes

–  Protists (protozoans and algae, falling into multiple kingdoms)

–  The kingdoms Fungi, Plantae, and Animalia

275!

Protists (multiple kingdoms)

Kingdom Fungi

Kingdom Animalia

Kingdom Plantae Figure 1.5C

Evolution explains the unity and diversity of life •  Charles Dar win

–  Synthesized the theory of evolution by natural selection

1

2

3

Populations with varied inherited traits

Elimination of individuals with certain traits

Reproduction of survivors

•  Natural selection is an editing mechanism

–  That occurs when populations or organisms, having inherited variations, are exposed to environmental factors that favor the reproductive success of some individuals over others

THE PROCESS OF SCIENCE

Scientists use two main approaches to learn about nature

•  Science

–  Is a way of knowing

–  Seeks natural causes for natural phenomena

Discovery Science

•  In discovery science

–  Scientists describe some aspect of the world and use inductive reasoning to draw general conclusions

Jane Goodall

Hypothesis-Based Science

•  In hypothesis-based science

–  Scientists attempt to explain obser vations by testing hypotheses

In studying nature, scientists make observations and form and test hypotheses

All scientists use the Scientific Method to test a hypothesis.

7 Steps: 1.  Observation 2.  Question 3.  Hypothesis 4.  Prediction 5.  Experiment 6.  Results 7.  Conclusion

Observations

Question

Hypothesis # 1: Dead batteries

Hypothesis # 2: Burnt-out bulb

Prediction: Replacing batteries will fix problem

Prediction: Replacing bulb will fix problem

Test prediction Test prediction

Results: Flashlight does not work. Hypothesis is falsified

Test does not falsify hypothesis

Scientific Method Observations

Question

Hypothesis

Test supports hypothesis; make additional predictions and test

them

Test does not support hypothesis; revise hypothesis

or pose new one Prediction

Test: experiment or

additional observation

Results / Data

Conclusion

•  Biology is connected to many impor tant issues in our lives

–  Environmental problems and solutions

–  Genetic engineering

–  Medicine