BIOLOGY 101

• Scientific Study of Life

• Introduction to Biology

• The lives of gray-headed flying foxes are closely entwined with the lives of the eucalyptus trees that form their habitat

– Eucalyptus trees provide food and roosting sites for the flying foxes

– Flying foxes aid in eucalyptus pollinationand help disperse the resulting seeds

Life in the Trees

• Flying foxes are becoming an endangered species, partly because of habitat destruction

• Biology is the scientific study of life

• Interactions between different kinds of organisms affect the lives of all

– Recall the example of flying foxes and eucalyptus trees

THE SCOPE OF BIOLOGY

• A structural hierarchy of life, from molecules to ecosystems, defines the scope of biology

• An ecosystem consists of:

– all organisms living in a particular area

– all nonliving physical components of the environment that affect the organisms (soil, water)

1.1 Life’s levels of organization define the scope of biology

• At the top of life’s hierarchy is the ecosystem

• Ecosystems include:

– all the organisms in an area, which make up a community

– interbreeding organisms of the same species, a population

ECOSYSTEM LEVELEucalyptus forest

COMMUNITY LEVELAll organisms ineucalyptus forest

POPULATION LEVELGroup of flying foxes

ORGANISM LEVELFlying fox

ORGAN SYSTEM LEVELNervous system

ORGAN LEVELBrain

Brain Spinal cord

TISSUE LEVELNervous

tissue

CELLULAR LEVELNerve cell

MOLECULAR LEVELMolecule of DNA Figure 1.1

• Organisms are made up of:– organ

systems

– organs

– tissues

– cells

– molecules

ECOSYSTEM LEVELEucalyptus forest

COMMUNITY LEVELAll organisms ineucalyptus forest

POPULATION LEVELGroup of flying foxes

ORGANISM LEVELFlying fox

ORGAN SYSTEM LEVELNervous system

ORGAN LEVELBrain

Brain Spinal cord

TISSUE LEVELNervous

tissue

CELLULAR LEVELNerve cell

MOLECULAR LEVELMolecule of DNA Figure 1.1

• In discovery science, scientists describe some aspect of the world and use inductive reasoning to draw general conclusions

– Example: scientists have described how newborn flying foxes cling to their mother’s chest for the first weeks of life

1.2 Scientists use two main approaches to learn about nature

THE PROCESS OF SCIENCE

Figure 1.2

• In hypothesis-driven science, scientists use the “scientific method”– They propose a hypothesis

– They make deductions leading to predictions

– They then test the hypothesis by seeing if the predictions come true

• The main steps of the scientific method

1.3 With the scientific method, we pose and test hypotheses

Observation

Question

Hypothesis

Prediction

Test:Experiment or

additionalobservation

Test does notsupport hypothesis; revise hypothesis or

pose new one

Test supports hypothesis; make

additional predictions and test them

Figure 1.3A

• Deductive reasoning is used in testing hypotheses– starts with a general

explanation which leads to predictions for specific observations supporting it

• Experiments designed to test hypotheses must be controlled experiments

• Control groups must be tested along with experimental groups for the meaning of the results to be clear.

– Controls are used to filter out other explanations. A control is a replica of the experiment with the independent variable omitted. The dependent variable is what is measured (like how much a plant grows from day to day). The control in human drug tests is generally a sugar pill called a placebo.

The scientific method• In order to eliminate human bias most drug tests

are conducted in a double blind fashion. In a double blind experiment researchers and patients do not know whether the pill given is the drug or the placebo until the trial is over.

• Case study: spider mimicry

Control group(untreated flies)

Experimental group(wing markings masked)

Figure 1.3C

Figure 1.3D

• Another test of the spider mimic hypothesis: wing transplants

Wingmarkings

Normalspidermimic

Figure 1.3E

Wingwaving

Mimic withmimic wing transplant

Controls Experimentals

Mimic withhousefly

wing transplant

Housefly with

mimic wing transplant

Normalhousefly

Modern Biology is based on;

• The Cell Theory• The Theory of Evolution by Natural

Selection• Gene Theory • Homeostasis

The Cell Theory:• All cells come

from pre-existing cells

• All organisms are composed of one or more cells.

• Grouping organisms by fundamental features helps make the vast diversity of life manageable for study

• Scientists classify organisms into a hierarchy of broader and broader groups

1.4 The diversity of life can be arranged into three domains

EVOLUTION, UNITY, AND DIVERSITY

Figure 1.8 Evolution

Tree of Life

• Most classification schemes group organisms into three domains:– Domain Bacteria

Figure 1.4A, B

– Domain Archaea

– Domain Eukarya

Figure 1.4C-F

Cells and Organelles

Macromolecules

• All organisms share a set of common features, signs of unity in life’s vast diversity

– All are made of cells

– All have DNA as their genetic blueprint

• These orchids show the variety possible within one species

1.5 Unity in diversity: All forms of life have common features

Figure 1.5A

• DNA is made of chemical units called nucleotides

• Each species has its own nucleotide sequence

Figure 1.5B

Central Dogma

Chromosomes

Cell Cycle

Mitosis

• The genetic information in DNA underlies all of the features that distinguish life from nonlife– Order and regulation

– Growth and development

– Use of energy from the environment

– Response to environmental stimuli

– Ability to reproduce

– Evolutionary change

Molecular Basis of Inheritance

Cells and Tissues• In human body, there are more than

200 different kinds of cells.• These cells make up five main type

of tissue•Epithelial tissue•Connective tissue•Blood•Nervous tissue•Muscle

Connective Tissue

Fibroblasts

Epithelial tissue

From The Cell 2nd ednASM & Sinauer

Bile duct

Granulocyte Lymphocyte Monocyte

Nervous tissue

from http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Nervous/Nervous.htm

Muscle

Smooth muscle Skeletal muscle Cardiac muscle

From http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/h_frame7.html

• Charles Darwin is a central figure in biology

• He synthesized the theory of evolution by natural selection

– A theory in science is a comprehensive idea with broad explanatory power

• Evolution is the core theme of biology

1.6 Evolution explains the unity and diversity of life

Figure 1.6A

• The theory of natural selection explains the main mechanism whereby all species of organisms change, or evolve

Figure 1.6B

(1) Population with varied inherited traits

(2) Elimination of individuals with certain traits

(3) Reproduction of survivors

Model Organisms: E. coli

• Uses medium containing glucose, aa, salts, vitamins; Divide every 20 mins

• Genome contains 4.6 million base pairs; about 4000 genes

• Clonal populations can be selected; those resistant to penicillin

Figure 1.14 Bacterial Colonies

Yeast: S. cerevisiae

• Eukaryotic

• Genome contains 12 million base pairs of DNA; 6000 genes; 16 linear chromosomes

• Can be grown in the lab; replicate every 2 hours grown in colonies

• Can be used to understand DNA replication, transcription, RNA processing, protein sorting, regulation of cell division

Figure 1.15 Electron Micrograph of Saccharomyces cerevisiae

Worm: C. elegans

• Multicellular

• Understanding development

• Genome contains 100 million bps of DNA; 19000 genes

• Contain 959 cells (somatic); 1000-2000 germ cells

• Lineage tracing; genes of development and differentiation

Figure 1.17 Caenorhabditis elegans

Plant: Arabidopsis

• Plant molecular biology and development

• Genome contains 120 million bp of DNA, 15000 genes.

• Can be grown in pots; mutants are available

• Comparisons of cellular mechanisms between plants and animals

Figure 1.19 Arabidopsis thaliana

Vertebrates

• Xenopus laevis: frog

• Danio rerio: fish

Figure 1.20 Eggs of the Frog Xenopus laevis

Figure 1.21 Zebrafish

Model Organisms and Applications

Figure 1.22 Defects in pigmentation (piebaldism) due to mutations in a gene regulate migration of melanocytes

Humans and Flies Alike (Pax6 gene)

Table 1.1 Prokaryotic and Eukaryotic Cells

Table 1.2 DNA Content of Cells

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