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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

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Chapter 1

Chapter 1

Exploring Life


Chapter 1

  • 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


Chapter 1

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

  • Each level of biological organization has emergent properties

  • Properties not found in the previous level

Video: Seahorse Camouflage


Chapter 1

  • 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


A hierarchy of biological organization

A Hierarchy of Biological Organization

  • Biosphere: all environments on Earth

  • Ecosystem: all living and nonliving things in a particular area

  • Community: all organisms in an ecosystem

  • Population: all individuals of a species in a particular area

  • Organism: an individual living thing


A hierarchy of biological organization continued

A Hierarchy of Biological Organization (continued)

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

  • Tissue: a group of similar cells

  • Cell: life’s fundamental unit of structure and function

  • Organelle: a structural component of a cell

  • Molecule: a chemical structure consisting of atoms


Chapter 1

The biosphere

Organelles

1 µm

Cell

Ecosystems

Cells

Atoms

Molecules

10 µm

Communities

Tissues

50 µm

Populations

Organs and organ systems

Organisms


A closer look at ecosystems

A Closer Look at Ecosystems

  • Each organism interacts with its environment

  • Both organism and environment affect each other


Ecosystem dynamics

Ecosystem Dynamics

  • 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

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

LE 1-4

Sunlight

Ecosystem

Producers

(plants and other

photosynthetic

organisms)

Heat

Chemical

energy

Consumers

(including animals)

Heat


A closer look at cells

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

  • Basic concept of the Cell theory.


Le 1 5

LE 1-5

25 µm


The cell s heritable information

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


Le 1 6

LE 1-6

Sperm cell

Nuclei

containing

DNA

Fertilized egg

with DNA from

both parents

Embryo’s cells

With copies of

inherited DNA

Egg cell

Offspring with traits

inherited from both parents


Chapter 1

  • 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


Le 1 7

LE 1-7

Nucleus

DNA

Nucleotide

Cell

DNA double helix

Single strand of DNA


Two main forms of cells

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

LE 1-8

PROKARYOTIC CELL

EUKARYOTIC CELL

DNA

(no nucleus)

Membrane

Membrane

Cytoplasm

Organelles

Nucleus (contains DNA)

1 µm


Chapter 1

  • Concept 1.2: Biological systems are much more than the sum of their parts

  • A system is a combination of components that form a more complex organization

  • Cells, organisms, and ecosystems are some examples of biological systems


The emergent properties of systems

The Emergent Properties of Systems

  • Emergent properties result from arrangements and interactions within systems

  • New properties emerge with each step upward in the hierarchy of biological order

  • Emergent properties are more difficult to study in living systems due to complexity.


The power and limitations of reductionism

The Power and Limitations of Reductionism

  • Reductionism is reducing complex systems to simpler components that are easier to study

  • But only see part of the whole.

  • The studies of DNA structure and the Human Genome Project are examples of reductionism


Systems biology

Systems Biology

  • Systems biology seeks to create models of the dynamic behavior of whole biological systems

  • An example is a systems map of interactions between proteins in a fruit fly cell

  • Why use fruit flies?

  • Such models may predict how a change in one part of a system will affect the rest of the system

  • Examples, ecosystems and sugar levels in the blood


Le 1 10

LE 1-10

Outer membrane

and cell surface

CELL

Cytoplasm

Nucleus


Chapter 1

  • Systems biology uses three key research developments:

    • High-throughput technology: methods to generate large data sets rapidly, such as..?

    • Bioinformatics: using computers and software to process and integrate large data sets

    • Interdisciplinary research teams


Feedback regulation in biological systems

Feedback Regulation in Biological Systems

  • Regulatory systems ensure a dynamic balance in living systems

  • Chemical processes are catalyzed (accelerated) by enzymes

  • Many biological processes are self-regulating: the product regulates the process itself


Chapter 1

  • In negative feedback, the accumulation of a product slows down the process itself

  • In positive feedback (less common), the product speeds up its own production, example blood clotting.

Animation: Negative Feedback

Animation: Positive Feedback


Le 1 11

LE 1-11

A

A

Negative

feedback

Enzyme 1

Enzyme 1

B

B

Enzyme 2

C

C

Enzyme 3

D

D

D

D

D

D

D

D

D

D

D


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LE 1-12

W

W

Enzyme 4

Enzyme 4

X

X

Positive

feedback

Enzyme 5

Enzyme 5

Y

Y

Enzyme 6

Enzyme 6

Z

Z

Z

Z

Z

Z

Z

Z

Z

Z

Z

Z

Z

Z

Z

Z

Z

Z

Z


Chapter 1

  • Concept 1.3: Biologists explore life across its great diversity of species

  • Biologists have named about 1.8 million species

  • Estimates of total species range from 10 million to over 200 million


Grouping species the basic idea

Grouping Species: The Basic Idea

  • Taxonomy is the branch of biology that names and classifies species into a hierarchical order

  • Kingdoms and domains are the broadest units of classification


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LE 1-14

Family

Phylum

Order

Kingdom

Domain

Species

Genus

Class

Ursus

americanus

(American

black bear)

Ursus

Ursidae

Carnivora

Mammalia

Chordata

Animalia

Eukarya


The three domains of life

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


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LE 1-15

Protists

Kingdom Plantae

Bacteria

4 µm

100 µm

Archaea

Kingdom Animalia

Kingdom Fungi

0.5 µm


Unity in the diversity of life

Unity in the Diversity of Life

  • Underlying life’s diversity is a striking unity, especially at lower levels of organization

  • In eukaryotes, unity is evident in details of cell structure

  • Example structure of the organelles


Le 1 16a

LE 1-16a

5 µm

15 µm

Cilia of Paramecium

Cilia of windpipe cells


Le 1 16b

LE 1-16b

0.1 µm

Cross section of cilium,

as viewed with an

electron microscope

Cilia of windpipe cells

Cilia of Paramecium


Chapter 1

  • 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


Chapter 1

  • The evolutionary view of life came into sharp focus in 1859, when Charles Darwin published On the Origin of Species by Natural Selection

  • “Darwinism” became almost synonymous with the concept of evolution


Chapter 1

  • The Origin of Species articulated two main points:

    • Descent with modification (the view that contemporary species arose from a succession of ancestors)

    • Natural selection (a proposed mechanism for descent with modification)

  • Some examples of descent with modification are unity and diversity in the orchid family


Natural selection

Natural Selection

  • Darwin inferred natural selection by connecting two observations:

    • Observation: Individual variation in heritable traits

    • Observation: Overpopulation and competition

    • Inference: Unequal reproductive success

    • Inference: Evolutionary adaptation


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LE 1-20

Population

of organisms

Overproduction

and competition

Hereditary

variations

Differences in

reproductive success

Evolution of adaptations

in the population


Chapter 1

  • Natural selection can “edit” a population’s heritable variations

  • An example is the effect of birds preying on a beetle population


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LE 1-21

Population with varied inherited traits

Elimination of individuals with certain traits

Reproduction of survivors

Increasing frequency of traits that enhance

survival and reproductive success


Chapter 1

  • Natural selection is often evident in adaptations of organisms to their way of life and environment

  • Bat wings are an example of adaptation

Video: Soaring Hawk


The tree of life

The Tree of Life

  • Many related organisms have similar features adapted for specific ways of life

  • Such kinships connect life’s unity and diversity to descent with modification

  • Natural selection eventually produces new species from ancestral species

  • Biologists often show evolutionary relationships in a treelike diagram

[Videos on slide following the figure]


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LE 1-23

Large

ground finch

Large

tree finch

Small

ground

finch

Large cactus

ground finch

Camarhynchus

psittacula

Geospiza

magnirostris

Green

warbler

finch

Gray

warbler

finch

Geospiza

fuliginosa

Woodpecker

finch

Medium

tree finch

Sharp-beaked

ground finch

Geospiza

conirostris

Medium

ground

finch

Certhidea

fusca

Certhidea

olivacea

Geospiza

difficilis

Camarhynchus

pauper

Cactus

ground finch

Cactospiza

pallida

Small

tree finch

Mangrove

finch

Geospiza

fortis

Geospiza

scandens

Camarhynchus

parvulus

Cactospiza

heliobates

Vegetarian

finch

Seed eater

Seed eaters

Cactus flower

eaters

Platyspiza

crassirostris

Bud eater

Insect eaters

Ground finches

Tree finches

Warbler finches

Common ancestor from

South American mainland


Chapter 1

Video: Albatross Courtship Ritual

Video: Blue-footed Boobies Courtship Ritual

Video: Galapágos Islands Overview

Video Galapágos Marine Iguana

Video: Galapágos Sea Lion

Video: Galapágos Tortoise


Chapter 1

  • Concept 1.5: Biologists use various forms of inquiry to explore life

  • Inquiry is a search for information and explanation, often focusing on specific questions

  • The process of science blends two main processes of scientific inquiry:

    • Discovery science: describing nature

    • Hypothesis-based science: explaining nature


Discovery science

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

Types of Data

  • Data are recorded observations

  • Two types of data:

    • Quantitative data: numerical measurements

    • Qualitative data: recorded descriptions


Induction in discovery science

Induction in Discovery Science

  • Inductive reasoning involves generalizing based on many specific observations


Hypothesis based science

Hypothesis-Based Science

  • In science, inquiry usually involves proposing and testing hypotheses

  • Hypotheses are hypothetical explanations


The role of hypotheses in inquiry

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


Le 1 25a

LE 1-25a

Observations

Question

Hypothesis #1:

Dead batteries

Hypothesis #2:

Burnt-out bulb


Le 1 25b

LE 1-25b

Hypothesis #2:

Burnt-out bulb

Hypothesis #1:

Dead batteries

Prediction:

Replacing batteries

will fix problem

Prediction:

Replacing bulb

will fix problem

Test prediction

Test prediction

Test falsifies hypothesis

Test does not falsify hypothesis


Deduction the if then logic of hypothesis based science

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 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 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

  • Development of scientific method, industry or Galileo?


A case study in scientific inquiry investigating mimicry in snake populations

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

  • In mimicry, a harmless species resembles a harmful species

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


Le 1 26

LE 1-26

Flower fly (nonstinging)

Honeybee (stinging)


Chapter 1

  • 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

LE 1-27

Scarlet king snake

Key

Range of scarlet

king snake

Range of eastern

coral snake

Eastern coral

snake

North

Carolina

South

Carolina

Scarlet king snake


Field experiments with artificial snakes

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

LE 1-28

(a) Artificial king snake

(b) Artificial brown snake that has been attacked


Le 1 29

LE 1-29

17%

In areas where coral snakes

were absent, most attacks

were on artificial king snakes.

83%

Key

North

Carolina

% of attacks on

artificial king snakes

% of attacks on

brown artificial snakes

South

Carolina

Field site with

artificial snakes

16%

84%

In areas where coral

snakes were present,

most attacks were on

brown artificial snakes.


Designing controlled experiments

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

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

Theories in Science

  • A scientific theory is much broader than a hypothesis

  • A scientific theory is:

    • broad in scope

    • general enough to generate new hypotheses

    • supported by a large body of evidence


Model building in science

Model Building in Science

  • Models are representations of ideas, structures, or processes

  • Models may range from lifelike representations to symbolic schematics


Le 1 30

LE 1-30

From

lungs

From

body

Left

atrium

Right

atrium

Left

ventricle

Right

ventricle

To lungs

To body


The culture of science

The Culture of Science

  • Science is an intensely social activity

  • Both cooperation and competition characterize scientific culture


Science technology and society

Science, Technology, and Society

  • The goal of science is to understand natural phenomena

  • Technology applies scientific knowledge for some specific purpose


Chapter 1

  • Concept 1.6: A set of themes connects the concepts of biology

  • Biology is the science most connected to the humanities and social sciences

  • Underlying themes provide a framework for understanding biology


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