CHAPTER 1 Introduction: The Scientific Study of Life

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Transcript CHAPTER 1 Introduction: The Scientific Study of Life

BIOLOGY

CONCEPTS & CONNECTIONS Fourth Edition

Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor

CHAPTER 1

Introduction: The Scientific Study of Life

Modules 1.1 – 1.3

Life in the Trees

• 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 pollination and help disperse the resulting seeds Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

THE SCOPE OF BIOLOGY

• 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 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

1.1 Life’s levels of organization define 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) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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

ECOSYSTEM LEVEL Eucalyptus forest

• Ecosystems include: – all the organisms in an area, which make up a community – interbreeding organisms of the same species, a population

COMMUNITY LEVEL All organisms in eucalyptus forest ORGANISM LEVEL Flying fox POPULATION LEVEL Group of flying foxes Brain Spinal cord ORGAN SYSTEM LEVEL Nervous system ORGAN LEVEL Brain Nerve TISSUE LEVEL Nervous tissue CELLULAR LEVEL Nerve cell MOLECULAR LEVEL Molecule of DNA

ECOSYSTEM LEVEL Eucalyptus forest COMMUNITY LEVEL All organisms in eucalyptus forest ORGANISM LEVEL Flying fox POPULATION LEVEL Group of flying foxes Brain Spinal cord ORGAN SYSTEM LEVEL Nervous system ORGAN LEVEL Brain Nerve TISSUE LEVEL Nervous tissue CELLULAR LEVEL Nerve cell MOLECULAR LEVEL Molecule of DNA

Figure 1.1

THE PROCESS OF SCIENCE 1.2 Scientists use two main approaches to learn about nature

• 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 Figure 1.2

Inductive vs. Deductive Reasoning

INDUCTIVE REASONING

• •

Discovery science can lead to important conclusions based on inductive reasoning. We derive generalizations based on a large number of specific observations. Example: The sun always rises in the east.

• •

All organisms are made of cells.

DEDUCTIVE REASONING

•

Logic flows in the opposite direction, from general to specific. Example: If all organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans are composed of cells (deductive prediction about a specific case).

• 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 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

1.3 With the scientific method, we pose and test hypotheses Observation

• The main steps of the scientific method

Question Hypothesis Prediction Test does not support hypothesis; revise hypothesis or pose new one Test: Experiment or additional observation Test supports hypothesis; make additional predictions and test them

Figure 1.3A

• Deductive reasoning is used in testing hypotheses – If a hypothesis is correct, and we test it, then we can expect a particular outcome • Case study: flashlight failure Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 1.3B

• 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 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Case study: spider mimicry Figure 1.3C

Figure 1.3D

Control group (untreated flies) Experimental group (wing markings masked)

Examples of hypotheses:

•

1. The markings and wing-waving of spider mimic flies increases their survival by causing jumping spiders to flee.

•

2. If the flies’ wing markings are masked with a dye, then jumping spiders should pounce on the marked flies more often.

• Another test of the spider mimic hypothesis: wing transplants

Wing markings Wing waving Normal spider mimic Mimic with mimic wing transplant Mimic with housefly wing transplant

Figure 1.3E

Controls

Housefly with mimic wing transplant Experimentals Normal housefly

EVOLUTION, UNITY, AND DIVERSITY 1.4 The diversity of life can be arranged into three domains

• 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 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Prokaryotic vs. Eukaryotic Cells

•

Six Kingdoms of Life

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

• 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 Figure 1.5A

• DNA is made of chemical units called nucleotides • Each species has its own nucleotide sequence Figure 1.5B

• 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 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

1.6 Evolution explains the unity and diversity of life

• 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 Figure 1.6A

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

(1) Population with varied inherited traits (2) Elimination of individuals with certain traits

Figure 1.6B

(3) Reproduction of survivors

• Evolution happens when populations of organisms with inherited variations are exposed to environmental factors that favor the success of some individuals over others – Natural selection is the editing mechanism – Evolution is based on adaptations Figure 1.6C

1.7 Living organisms and their environments form interconnecting webs

• The theory of natural selection applies to all levels in life’s hierarchy • In an ecosystem, these interactions make up a complex web of relationships – The functional aspects of an ecosystem come from the structure of the ecosystem’s web Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• A web of interactions in a rain forest ecosystem Figure 1.7A

• Plants, or plant products, are the ultimate sources of food in an ecosystem – This African sunbird is consuming nectar, a plant product Figure 1.7B

• Chemical nutrients cycle within an ecosystem’s web – Energy flows in and out constantly

Sun Inflow of light energy Loss of heat energy Air Chemical energy Organisms Cycling of chemical nutrients

Figure 1.7C

Soil ECOSYSTEM

BIOLOGY AND EVERYDAY LIFE 1.8 Connection: Biology is connected to our lives in many ways

• Biology is connected to a great number of important issues – Environmental problems and solutions – Genetic engineering – Medicine Figure 1.8A

• • Many technological advances stem from the scientific study of life Evaluating everyday reports in the press about a large range of subjects requires critical thinking and some familiarity with many areas of biology – In order to understand how rain forest destruction impacts global climate, it is important to understand biology from the molecular to the ecosystem level Figure 1.8B