Figure 1.1 Life’s Calendar

Origin of Life

Oldest fossils

Photo-synthesis evolves

Eukaryotic cells evolve

Multi-cellular organisms

Abundant fossils of aquatic life

First land plants

First land animals

Coal-forming forests

Insects abundant

First mammals

Dinosaurs dominant

First birds

First flowering plants

Rise of mammals

First hominids

Figure 1.2 The Basic Unit of Life Is the Cell

Haloferax mediterranei Membrane

Figure 1.4 The Tree of Life

Life

Plants

Protists

Protists

Protists

Protists

Protists

Protists

Animals

Fungi

10,000

260

270,000

80,000

1,300,000

98,000

1,000–1 million

400,000–500,000

500,000–1 million

10 million–100 million

1–2 million

MillionsBACTERIA

ARCHAEA

EUKARYA

Mito

ch

on

dri a

Ch

l oro

pl a

sts

Number of known (described)

species

Estimated total number of living

species

Figure 1.5 DNA Is Life’s Blueprint

One nucleotide

DNA

Gene

DNA

Protein

Figure 1.6 Biology Is Studied at Many Levels of Organization (Part 1)

(A) Atoms to organisms

Atoms

Oxygen

Carbon

Hydrogen

Water

Small molecules

Methane

Carbon dioxide

Large molecules, proteins, nucleic acids

Cells

Colonial organisms

Unicellular organisms

Cell specialization

Tissues

Organs

Organs systemsMulticellular organism

(leopard frog)

Organism

Figure 1.6 Biology Is Studied at Many Levels of Organization (Part 2)

(B) Organisms to ecosystemsEcosystem

PopulationCommunity

Biosphere

Figure 1.7 Adaptations to the Environment (Part 1)

(A) Dyscophus guineti

Figure 1.7 Adaptations to the Environment (Part 2)

(B) Xenopus laevis

Figure 1.7 Adaptations to the Environment (Part 3)

(C) Agalychnis callidryas

Figure 1.7 Adaptations to the Environment (Part 4)

(D) Rhacophorus nigropalmatus

Figure 1.8 Scientific Methodology

1. Make observations.

2. Speculate, ask a question.

3. Form a hypothesis to answer the question.

4. Make a prediction: What else would be true if your hypothesis is correct?

5. Design and conduct an experiment that uses quantifiable data to test your prediction.

Use statistical tests to evaluate the significance of your results.

Significant results support hypothesis.

Results do not support hypothesis.

Experiment repeated and results verified by other researchers.

Reexamine the experiment for uncontrolled variables.

Revise your hypothesis.

Ask new questions.

Figure 1.9 Controlled Experiments Manipulate a Variable (Part 1)

Exposure to atrazine during larval development causes abnormalities in the reproductive tissues of male frogs.

1. Establish 9 tanks in which all attributes are held constant except the water’s atrazine concentration. Establish 3 atrazine conditions (3 replicate tanks per condition): 0 ppb (control condition), 0.1 ppb, and 25 ppb.

2. Place Rana pipiens tadpoles from laboratory-reared eggs in the 9 tanks (30 tadpoles per replicate).

3. When tadpoles have transitioned into adults, sacrifice the animals and evaluate their reproductive tissues.

4. Test for correlation of degree of atrazine exposure with the presence of abnormalities in the gonads (testes) of male frogs.

Figure 1.9 Controlled Experiments Manipulate a Variable (Part 2)

Oocytes (eggs) in normal-sized testis (sex reversal)

Atrophied testes

Testicular oogenesis

Ma

le f

rog

s

wit

h g

on

ad

al

ab

no

rma

liti

es

(%

)

Atrazine (ppb)Control

Exposure to atrazine at concentrations as low as 0.1 ppbinduces abnormalities in the gonads of male frogs. The effect is not proportional to the level of exposure.

Figure 1.10 Comparative Experiments Look for Differences among Groups (Part 1)

Presence of the herbicide atrazine in environmental water correlates with gonadal abnormalities in frog populations.

1. Based on commercial sales of atrazine, select 4 sites (sites 1–4) less likely and 4 sites (sites 5–8) more likely to be contaminated with atrazine.

2. Visit all sites in the spring (i.e., when frogs have transitioned from tadpoles into adults); collect frogs and water samples.

3. In the laboratory, sacrifice frogs and examine their reproductive tissues, documenting abnormalities.

4. Analyze the water samples for atrazine concentration (the sample for site 7 was not tested).

5. Quantify and correlate the incidence of reproductive abnormalities with environmental atrazine concentrations.

Figure 1.10 Comparative Experiments Look for Differences among Groups (Part 2)

Atrophied testes

Testicular oogenesis

Atrazine level

Atra

zine

(pp

b)

Ma

le f

rog

s w

ith

go

na

da

l a

bn

orm

ali

tie

s (

%)

Reproductive abnormalities exist in frogs from environments in which aqueous atrazine concentration is 0.2 ppb or above. The incidence of abnormalities does not appear to be proportional to atrazine concentration at the time of transition to adulthood.

Site