1 an introduction to life on earth. overview: inquiring about the world of life evolution is the...

1An Introduction to Life on Earth

Overview: Inquiring About the World of Life

• Evolution is the process of change that has transformed life on Earth

• Biology is the scientific study of life

• Biologists ask questions such as:

– How a single cell develops into an organism

– Living things are all descended from a single-celled ancestor (a single common ancestor).

– The characteristics shared by all organisms logically lead to the conclusion that all life has a common ancestry

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Order

Evolutionary adaptation

Responseto theenvironment

Reproduction

Growth anddevelopment

Energyprocessing

Regulation

Fig. 1-3

Characteristics shared by all living organisms

Fig. 1-3a

Order

Fig. 1-3b

Evolutionaryadaptation

Fig. 1-3c

Responseto theenvironment

Fig. 1-3d

Reproduction

Fig. 1-3e

Growth and development

Fig. 1-3f

Energy processing

Fig. 1-3g

Regulation

Theme: New properties emerge at each level in the biological hierarchy

• Life can be studied at different levels from molecules to the entire living planet

• The study of life can be divided into different levels of biological organization

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Fig. 1-4

The biosphere

Communities

Populations

Organisms

Ecosystems

Organs and organ systems

Cells

Cell

Organelles

Atoms

MoleculesTissues

10 µm

1 µm

50 µm

The biosphere

Communities

Populations

Organisms

Ecosystems

Fig. 1-4a

Fig. 1-4b

Organs and organ systems

Cells

Cell

Organelles

Atoms

MoleculesTissues

10 µm

1 µm

50 µm

Fig. 1-4c

The biosphere

Fig. 1-4d

Ecosystems

Fig. 1-4e

Communities

Fig. 1-4f

Populations

Fig. 1-4g

Organisms

Fig. 1-4h

Organs andorgan systems

Fig. 1-4i

Tissues50 µm

Fig. 1-4j

Cells

Cell

10 µm

Fig. 1-4k

1 µm

Organelles

Fig. 1-4l

Atoms

Molecules

Life Consists of Organized Systems at a Hierarchy of Scales (1)

Life Consists of Organized Systems at a Hierarchy of Scales (2)

Theme: Organisms interact with their environments, exchanging matter and energy

• Every organism interacts with its environment, including nonliving factors and other organisms

• Both organisms and their environments are affected by the interactions between them

– For example, a tree takes up water and minerals from the soil and carbon dioxide from the air; the tree releases oxygen to the air and roots help form soil

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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

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Fig. 1-5

Sunlight

Ecosystem

Heat

Heat

Cyclingof

chemicalnutrients

Producers(plants and other photosynthetic

organisms)

Chemical energy

Consumers(such as animals)

Theme: Cells are an organism’s basic units of structure and function

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

• All cells:

– Are enclosed by a membrane

– Use DNA as their genetic information

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

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Figure 1-1 The cell is the smallest unit of life

organelles

nucleus

cell wall

plasmamembrane

25 µm

Fig. 1-7

• A eukaryotic cell has membrane-enclosed organelles, the largest of which is usually the nucleus

• By comparison, a prokaryotic cell is simpler and usually smaller, and does not contain a nucleus or other membrane-enclosed organelles

• Bacteria and Archaea are prokaryotic; plants, animals, fungi, and all other forms of life are eukaryotic

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1 µmOrganelles

Nucleus (contains DNA)

Cytoplasm

Membrane

DNA(no nucleus)

Membrane

Eukaryotic cellProkaryotic cellFig. 1-8

Theme: The continuity of life is based on heritable information in the form of DNA

• Chromosomes contain most of a cell’s genetic material in the form of DNA (deoxyribonucleic acid)

• DNA is the substance of genes

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

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DNA Structure and Function

• Each chromosome has one long DNA molecule with hundreds or thousands of genes

• DNA is inherited by offspring from their parents

• DNA controls the development and maintenance of organisms

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NucleicontainingDNA

Sperm cell

Egg cell

Fertilized eggwith DNA fromboth parents

Embryo’s cells withcopies of inherited DNA

Offspring with traitsinherited fromboth parents

Fig. 1-9

• 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

• http://www.youtube.com/watch?v=gbSIBhFwQ4s

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Fig. 1-10

Nucleus DNA

Cell

Nucleotide

(a) DNA double helix (b) Single strand of DNA

Figure 1.9 DNA Is Life’s Blueprint

• Genes control protein production indirectly

• DNA is transcribed into RNA then translated into a protein

• http://www.youtube.com/watch?v=C8OL1MTbGpU

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Grouping Species: The Basic Idea

• Taxonomy is the branch of biology that names and classifies species into groups of increasing breadth

• Domains, followed by kingdoms, are the broadest units of classification

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Fig. 1-14Species Genus Family Order Class Phylum Kingdom Domain

Ursus americanus(American black bear)

Ursus

Ursidae

Carnivora

Mammalia

Chordata

Animalia

Eukarya

Each species has a distinct scientific name,

a binomial:•

Genus name•

Species name

The Three Domains of Life

• The three-domain system is currently used, and replaces the old five-kingdom system

• Domain Bacteria and domain Archaea comprise the prokaryotes

• Domain Eukarya includes all eukaryotic organisms

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Fig. 1-15(a) DOMAIN BACTERIA

(b) DOMAIN ARCHAEA

(c) DOMAIN EUKARYA

Protists

Kingdom Fungi

KingdomPlantae

Kingdom Animalia

Fig. 1-15a

(a) DOMAIN BACTERIA

Fig. 1-15b

(b) DOMAIN ARCHAEA

• The domain Eukarya includes three multicellular kingdoms:

– Plantae

– Fungi

– Animalia

• Other eukaryotic organisms were formerly grouped into a kingdom called Protista, though these are now often grouped into many separate kingdoms

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Fig. 1-15c

(c) DOMAIN EUKARYA

Protists

Kingdom Fungi

Kingdom Plantae

Kingdom Animalia

1.3 How Do Scientists Study Life?

• Multicellularity occurs only among the Eukarya

– Unicellular (single-celled) organisms are found in

• Bacteria

• Archaea

– Multicellular (many-celled) organisms are found in Eukarya, within the kingdoms

• Fungi

• Plantae

• Animalia

Unity in the Diversity of Life

• A striking unity underlies the diversity of life; for example:

– DNA is the universal genetic language common to all organisms

– Unity is evident in many features of cell structure

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Fig. 1-16

Cilia ofParamecium

Cross section of a cilium, as viewedwith an electron microscope

Cilia ofwindpipecells

15 µm 5 µm

0.1 µm

Charles Darwin and the Theory of Natural Selection

• Fossils and other evidence document the evolution of life on Earth over billions of years

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Fig. 1-17

1.1 What Is Life?

• Organisms, collectively, have the capacity to evolve

– Evolution is the process by which modern organisms descended, with modifications, from preexisting forms of life

– Changes in DNA within populations occur over the course of generations, which results in evolution

• Populations are groups of the same type of organism living in the same area

1.2 What Is Evolution?

• Evolution explains the diversity of life on Earth

• Evolution provides an explanation for the similarities found among different types of organisms

– Chimpanzees and people have various physical features in common

– DNA of humans differs from that of chimpanzees by less than 5%

Scientists use two main forms of inquiry in their study of nature

• The word Science is derived from Latin and means “to know”

• Inquiry is the search for information and explanation

• There are two main types of scientific inquiry: discovery science and hypothesis-based science

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Discovery Science

• Discovery science describes natural structures and processes

• This approach is based on observation and the analysis of data

• Data are recorded observations or items of information

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Types of Data

• Data fall into two categories:

– Qualitative, or descriptions rather than measurements

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Types of Data

• Data fall into two categories:

– Quantitative, or recorded measurements, which are sometimes organized into tables and graphs

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Hypothesis-Based Science

• Observations can lead us to ask questions and propose hypothetical explanations called hypotheses

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The Role of Hypotheses in Inquiry

• A hypothesis is a tentative answer to a well-framed question

• A scientific hypothesis leads to predictions that can be tested by observation or experimentation

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1.4 What Is Science?

• The scientific method is an important tool of scientific inquiry

– The scientific method consists of six interrelated elements

• Observation

• Question

• Hypothesis

• Prediction

• Experiment

• Conclusion

Fig. 1-24

Observations

Question

Hypothesis #1:Dead batteries

Hypothesis #2:Burnt-out bulb

Prediction:Replacing batterieswill fix problem

Prediction:Replacing bulbwill fix problem

Test prediction Test prediction

Test falsifies hypothesis Test does not falsify hypothesis

• For example,

– Observation: Your flashlight doesn’t work

– Question: Why doesn’t your flashlight work?

– Hypothesis 1: The batteries are dead

– Hypothesis 2: The bulb is burnt out

• Both these hypotheses are testable

Observations

Question

Hypothesis #1:Dead batteries

Hypothesis #2:Burnt-out bulb

A Closer Look at Hypotheses in Scientific Inquiry

• A hypothesis must be testable and falsifiable

• Hypothesis-based science often makes use of two or more alternative hypotheses

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A Closer Look at Hypotheses in Scientific Inquiry

• Failure to falsify a hypothesis does not prove that hypothesis

– For example, you replace your flashlight bulb, and it now works; this supports the hypothesis that your bulb was burnt out, but does not prove it (perhaps the first bulb was inserted incorrectly)

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Determining the Variables

• Dependent Variable

– Measure, counted or observed in response to experimental conditions

• Independent Variable

– Variable or experimental condition manipulated

• Controlled Variable

The Procedure

• Procedure

– Sequence of steps to be performed for experiment

• Replication

– Repeat procedure

• Control

– Independent variable held at established value or omitted

• Prediction

– Tests hypothesis, If……then statements

Scientific Theory

•Broad in scope

•Generates new hypotheses

•Supported by large body of evidence