Chapter 1

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 1

Exploring Life


• Overview: Biology’s Most Exciting Era• Biology is the scientific study of life• Biologists are moving closer to understanding:

– How a single cell develops into an organism– How plants convert sunlight to chemical

energy– How the human mind works– How living things interact in communities– How life’s diversity evolved from the first

microbes


• Life’s basic characteristic is a high degree of order

• Each level of biological organization has emergent properties

Video: Seahorse Camouflage


Some Properties of Life


• Concept 1.1: Biologists explore life from the microscopic to the global scale

• The study of life extends from molecules and cells to the entire living planet

• Biological organization is based on a hierarchy of structural levels

Themes Connect Biological Concepts

Ecosystems

The biosphere

Organisms

Populations

Communities

Cells

Organelles

MoleculesTissues

Organs and organ systems

Cell1 µm

Atoms

10 µm

50 µm


A Hierarchy of Biological Organization

1. Biosphere: all environments on Earth

2. Ecosystem: all living and nonliving things in a particular area

3. Community: all organisms in an ecosystem

4. Population: all individuals of a species in a particular area

5. Organism: an individual living thing


A Hierarchy of Biological Organization (continued)

6. Organ and organ systems: specialized body parts made up of tissues

7. Tissue: a group of similar cells

8. Cell: life’s fundamental unit of structure and function

9. Organelle: a structural component of a cell

10. Molecule: a chemical structure consisting of atoms


A Closer Look at Ecosystems

• Each organism interacts with its environment

• Both organism and environment affect each other

• The dynamics of an ecosystem include two major processes:

– Cycling of nutrients, in which materials acquired by plants eventually return to the soil

– The flow of energy from sunlight to producers to consumers


Energy Conversion

• Activities of life require work

• Work depends on sources of energy

• Energy exchange between an organism and environment often involves energy transformations

• In transformations, some energy is lost as heat

• Energy flows through an ecosystem, usually entering as light and exiting as heat

LE 1-4

Sunlight

Ecosystem

Heat

Heat

Chemicalenergy

Consumers(including animals)

Producers(plants and otherphotosynthetic

organisms)


A Closer Look at Cells

• The cell is the lowest level of organization that can perform all activities of life

• The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms


The Cell’s Heritable Information

• Cells contain DNA, the heritable information that directs the cell’s activities

• DNA is the substance of genes

• Genes are the units of inheritance that transmit information from parents to offspring


• Each DNA molecule is made up of two long chains arranged in a double helix

• Each link of a chain is one of four kinds of chemical building blocks called nucleotides


Two Main Forms of Cells

• Characteristics shared by all cells:

– Enclosed by a membrane

– Use DNA as genetic information

• Two main forms of cells:

– Eukaryotic: divided into organelles; DNA in nucleus

– Prokaryotic: lack organelles; DNA not separated in a nucleus

LE 1-8

Membrane

Cytoplasm

EUKARYOTIC CELL PROKARYOTIC CELL

DNA(no nucleus)

Membrane

1 µmOrganellesNucleus (contains DNA)


The Three Domains of Life

• At the highest level, life is classified into three domains:

– Bacteria (prokaryotes)

– Archaea (prokaryotes)

– Eukarya (eukaryotes)Eukaryotes include protists and the kingdoms Plantae, Fungi, and Animalia

LE 1-15

Bacteria 4 µm 100 µm

0.5 µm

Kingdom PlantaeProtists

Kingdom AnimaliaKingdom FungiArchaea


• Concept 1.4: Evolution accounts for life’s unity and diversity

• The history of life is a saga of a changing Earth billions of years old


Discovery Science

• Discovery science describes nature through careful observation and data analysis

• Examples of discovery science:

– understanding cell structure

– expanding databases of genomes


Types of Data

• Data are recorded observations

• Two types of data:

– Quantitative data: numerical measurements

– Qualitative data: recorded descriptions


Induction in Discovery Science

• Inductive reasoning involves generalizing based on many specific observations

In science, inquiry usually involves proposing and testing hypothesesHypotheses are hypothetical explanations

Hypothesis-Based Science


The Role of Hypotheses in Inquiry

• In science, a hypothesis is a tentative answer to a well-framed question

• A hypothesis is an explanation on trial, making a prediction that can be tested

Observations

Question

Hypothesis #1:Dead batteries

Hypothesis #2:Burnt-out bulb

LE 1-25b

Hypothesis #1:Dead batteries

Hypothesis #2:Burnt-out bulb

Test prediction

Test falsifies hypothesis

Prediction:Replacing batterieswill fix problem

Prediction:Replacing bulbwill fix problem

Test prediction

Test does not falsify hypothesis


Deduction: The “If…then” Logic of Hypothesis-Based Science

• In deductive reasoning, the logic flows from the general to the specific

• If a hypothesis is correct, then we can expect a particular outcome


A Closer Look at Hypotheses in Scientific Inquiry

• A scientific hypothesis must have two important qualities:

– It must be testable

– It must be falsifiable


The Myth of the Scientific Method• The scientific method is an idealized process of

inquiry

• Very few scientific inquiries adhere rigidly to the “textbook” scientific method


• In mimicry, a harmless species resembles a harmful species

• An example of mimicry is a stinging honeybee and a nonstinging mimic, a flower fly

A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations

Flower fly (nonstinging)

Honeybee (stinging)


• This case study examines king snakes’ mimicry of poisonous coral snakes

• The hypothesis states that mimics benefit when predators mistake them for harmful species

• The mimicry hypothesis predicts that predators in non–coral snake areas will attack king snakes more frequently than will predators that live where coral snakes are present

LE 1-27

Scarlet king snake

Eastern coralsnake

Scarlet king snake

Key

Range of scarlet king snake

NorthCarolina

Range of easterncoral snake

SouthCarolina


Field Experiments with Artificial Snakes

• To test this mimicry hypothesis, researchers made hundreds of artificial snakes:

– An experimental group resembling king snakes

– A control group resembling plain brown snakes

• Equal numbers of both types were placed at field sites, including areas without coral snakes

• After four weeks, the scientists retrieved the artificial snakes and counted bite or claw marks

• The data fit the predictions of the mimicry hypothesis

LE 1-28

(a) Artificial king snake

(b) Artificial brown snake that has been attacked

In areas where coral snakes were present, most attacks were on brown artificial snakes.

In areas where coral snakeswere absent, most attacks

were on artificial king snakes.

LE 1-29

% of attacks onartificial king snakes

% of attacks onbrown artificial snakes

Field site withartificial snakes

83%

NorthCarolina

SouthCarolina

17%

16%

84%

Key


Designing Controlled Experiments

• Scientists do not control the experimental environment by keeping all variables constant

• Researchers usually “control” unwanted variables by using control groups to cancel their effects


Limitations of Science

• The limitations of science are set by its naturalism

– Science seeks natural causes for natural phenomena

– Science cannot support or falsify supernatural explanations, which are outside the bounds of science


Theories in Science• A scientific theory is much broader than a

hypothesis and has been rigorously investigated.

• A scientific theory is:

– broad in scope

– general enough to generate new hypotheses

– supported by a large body of evidence


Science, Technology, and Society

• The goal of science is to understand natural phenomena

• Technology applies scientific knowledge for some specific purpose

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Chapter 1

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