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Overview: Inquiring About Life

An organisms adaptations to its environment

are the result of evolution

For example, the ghost plant is adapted toconserving water; this helps it to survive in the

crevices of rock walls

Evolution is the process of change that has

transformed life on Earth

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Order

Regulation

Reproduction

Response to the

environment

Evolutionary adaptation

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Concept 1.1: The themes of the book

make connections across differentareas of biology

Biology consists of more than memorizing

factual details

Themes help to organize biological information

to aid scaling across space and time.

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Theme: New Properties Emerge at

Each Level in the Biological Hierarchy

Life can be studied at different levels, frommolecules to the entire living planet

The study of life can be divided into differentlevels of biological organization

Global.Molecular

Emergent properties result from the

arrangement and interaction of parts within asystem and characterize non-biological entities aswell

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The Biosphere

Ecosystems

Communities

Organisms

Organs and

organ systems

Tissues

Organelles Cells

Molecules

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The Power and Limitations of

Reductionism

Reductionism is the reduction of complexsystems to simpler more easily studiedcomponents

For example, studying the molecular structure of DNAhelps us to understand the chemical basis of inheritance

An understanding of biology balancesreductionism with the study ofemergent

properties For example, new understanding comes from studyingthe interactions of DNA with other molecules

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Systems Biology

A system is a combination of componentsthat function together

Systems biology constructs models for the

dynamic behavior of whole biological systems

The systems approach poses questions suchas

How does a drug for blood pressure affect otherorgans?

How does increasing CO2 alter the biosphere?

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Humans have modified our environment

For example, half the human-generated CO2 staysin the atmosphere and contributes to global

warming

Global warming is a major aspect ofglobal

climate change

It is important to understand the effects of

global climate change on the Earth and its

populations

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Theme: Structure and Function Are

Correlated at All Levels ofBiological

Organization

Structure and function of living organisms are

closely related

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Theme: The Cell is the basic unit of an

Organisms 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

Prokaryotic cells (no organelles) Eukaryotic cell (organelles)

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Theme: The Continuity of Life Is Based

on Heritable Information in the Formof DNA

Chromosomes contain most of a cells genetic

material in the form ofDNA (deoxyribonucleicacid)

DNA is the substance of genes

Genes are the units of inheritance thattransmit information from parents to offspring

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DNAStructure and Function

Each chromosome has one long DNA molecule

with hundreds or thousands of genes

Genes encode information for building proteins

Proteins are the ones that do the work in the cell

(development and makes the organism)

DNA is inherited by offspring from their parents

DNA controls the development and maintenanceof organisms

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Cells and heredity through DNA

Cells contain chromosomes made partly of

DNA (the substance of genes) which program

a cells production of proteins and transmit

information from parent to offspring

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Each DNA molecule is made up of two long chainsarranged in a double helix

Each link of a chain is one of four kinds ofchemical building blocks called nucleotides andnicknamed A, G, C, and T

Genes control protein production indirectly

DNA is transcribed into RNA then translated intoa protein (central dogma)

Gene expression is the process of convertinginformation from gene (DNA) to cellular product

Genome - The entire library of geneticinstructions that an organism inherits

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Theme: Feedback Mechanisms

Regulate Biological Systems Feedback mechanisms allow biological processes

to self-regulate

Negative feedback means that as more of aproduct accumulates, the process that creates it

slows and less of the product is produced

Positive feedback means that as more of aproduct accumulates, the process that creates it

speeds up and more of the product is produced

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Evolution: An Overarching Biological

Theme

Evolution makes sense of everything we know

about biology and explains patterns ofunity

and diversity in living organisms

Organisms are modified descendants of common

ancestors

Similar traits among organisms are explained by

descent from common ancestors Differences among organisms are explained by

the accumulation of heritable changes

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Concept 1.2: The Core Theme:

Evolution accounts for the unity anddiversity of life or.Uhh, you know

the same, but different Nothing in biology makes sense except in the light of

evolutionTheodosius Dobzhansky Approximately 1.8 million species have been identified

6300 Prokaryotes

100,000 Fungi

290,000 Plants 52,000 Vertebrates

1,000,000 Insects

total number of spp estimated at 10 M to 100 M

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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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Unityin the Diversityof 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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Charles Darwin published On the Origin of

Species by Means of Natural Selection in 1859 Darwin made two main points

Species showed evidence of descent with

modification from common ancestors

Natural selection is the mechanism behind

descent with modification

Darwins theory explained the duality of unity

and diversity

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Darwin observed that

Individuals in a population vary in their traits, many ofwhich are heritable

More offspring are produced than survive, andcompetition is inevitable; surviving individuals generallysuit their environment

Darwin inferred that Individuals that are best suited to their environmentare more likely to survive and reproduce

Over time, more individuals in a population will have

the advantageous traits Evolution occurs as the unequal reproductive

success of individuals

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Or the environment selects for the

propagation of beneficial traits that promotesurvival and reproduction

4

Darwin called this process natural selectionthat could cause a single ancestral species togive rise to two or more descendent

species..

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Concept 1.3: In studying nature,

scientists make observations andthen form and test hypotheses

Inquiry is the search for information andexplanation and Biologists observe & describenatural structures and processes

Biology blends two main processes of scientific

inquiry Discovery science (describing nature)

Hypothesis-based science (explaining nature)

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Data

Data are recorded observations or items of

information; that may be:

Qualitative data, or descriptions rather than

measurements (e.g., Jane Goodalls observations of

chimpanzee behavior)

Quantitative data, or recorded measurements,

which can be presented in tables and graphs

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Inductive Reasoning and Hypotheses

Inductive reasoning draws conclusions through thelogical process of induction

Generalization on instances

Repeating specific observations can lead to importantgeneralizations: E.g., the sun always rises in the east

Observations and inductive reasoning can lead us toask questions and propose hypothetical explanations(tentative answers) called hypotheses

A scientific hypothesis leads to predictions that can be tested byobservation or experimentation

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Deductive Reasoning and Hypothesis

Testing

Deductive reasoning uses general premises tomake specific predictions

For example, if organisms are made of cells

(premise 1), and humans are organisms (premise 2),then humans are composed of cells (deductiveprediction)

Hypothesis-based science often makes use of

two or more alternative hypotheses, butfailure to falsify a hypothesis does not provethat hypothesis correct

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Questions without testable

hypotheses

cannot be Addressed by Science A hypothesis must be testable and falsifiable

For example, a hypothesis that ghosts fooled with

the light switch cannot be tested Hypotheses that cannot be tested e.g.

supernatural and religious explanations are

outside the bounds of science

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The Flexibility (slop) in the

Scientific Method

The scientific method is an idealized processof inquiry

Hypothesis-based science is based on the

textbook scientific method, but rarelyfollows all the ordered steps as biologicalsystems are complex and may not easily fitthe textbook method.

In science, observations and experimentalresults must be repeatable

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Concept 1.4: Science benefits from a

cooperative approach and diverse

viewpoints Most scientists work in teams, which often

include graduate and undergraduate studentsand rely on good communication (seminars,publications, and websites, etc)

Scientists check each others claims byperforming similar experiments

Scientists cooperate by sharing data aboutmodel organisms (e.g., the fruit fly Drosophilamelanogaster) or anything that they publish.

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Science, Technology, and Society

The goal of science is to understand naturalphenomena marked by discoveries

The goal oftechnology is to apply scientific

knowledge for some specific purpose marked by inventions

Ethical issues can arise from new technology,

but have as much to do with politics,economics, and cultural values as with scienceand technology