Chapter 1Introduction: Themes in the Study of Life

Big Picture

•Evolution: the process of change that has transformed life on Earth.•Biology: the scientific study of life.• It is about asking questions:•HOW?•WHY?

Themes in Biology

Order

Evolutionary adaptation

Responseto theenvironment

Reproduction

Growth anddevelopment

Energyprocessing

Regulation

8 Themes of AP Biology

1. Science as a Process2. Evolution3. Energy Transfer4. Continuity and Change5. Relationship of Structure to Function6. Regulation7. Interdependence in Nature8. Science, Technology, and Society

Concept 1.1Themes connect the concepts of biology.

Evolution

•Overarching theme of biology.•Makes sense of everything we know about living organisms.•All organisms living on Earth are modified descendants of common ancestors.

Biological Hierarchy•Life at different levels.

The biosphere

Communities

Populations

Organisms

Ecosystems

Organs and organ systems

Cells

Cell

Organelles

Atoms

MoleculesTissues

10 µm

1 µm

50 µm

Emergent Properties:• Result from the arrangement and interactions of

parts within a system.

Reductionism:• The reduction of complex systems to simpler

components that are more manageable to study.

Systems Biology:• Constructs models for the dynamic behavior of

the whole biological system – function together.

Organisms Interact with their Environments•Every organism interacts with its environment, including nonliving factors and other organisms.

Ecos

yste

m D

ynam

ics

Sunlight

Ecosystem

Heat

Heat

Cyclingof

chemicalnutrients

Producers(plants and other

photosyntheticorganisms)

Chemical energy

Consumers(such as animals)

Ener

gy C

onve

rsio

n

Structure and Function

(a) Wings

(c) Neurons

(b) Bones

Infoldings ofmembrane

Mitochondrion

(d) Mitochondria0.5 µm100 µm

Cells are the basic unit of structure and function.

•Lowest level of organization that can perform all activities required for life.

1 µmOrganelles

Nucleus (contains DNA)

Cytoplasm

Membrane

DNA(no nucleus)

Membrane

Eukaryotic cellProkaryotic cell

Continuity of life is based on heritable information in the form of DNA

• DNA is the substance of genes.• Genes are the units of inheritance that transmits

information from parents to offspring.

NucleicontainingDNA

Sperm cell

Egg cell

Fertilized eggwith DNA fromboth parents

Embryo’s cells withcopies of inherited DNA

Offspring with traitsinherited fromboth parents

Feedback mechanisms regulate biological systems•Negative Feedback: as more of a

product accumulates, the process that creates is slows and less of the product is produced.•Positive Feedback means that as

more of a product accumulates, the process that creates it speeds up and more of the product is produced.

Excess Dblocks a step

(a) Negative feedback

Negativefeedback

D

D D

D

C

B

A

Enzyme 1

Enzyme 2

Enzyme 3

–

Excess Zstimulates a step

(b) Positive feedback

Z

Positivefeedback

Enzyme 4

Enzyme 5

Enzyme 6Z

Z

Z

Y

X

W

+

Concept 1.2The Core Theme: Evolution accounts for the unity and diversity of life.

“Nothing in biology makes sense except in the light of evolution”—Theodosius Dobzhansky

Organizing the Diversity of Life

•Approximate 1.8 million species have been identified.• Estimates of species that actually exist

from 10 to over 100 million.•Organized in groups: Taxonomy

Species Genus Family Order Class Phylum Kingdom Domain

Ursus americanus(American black bear)

Ursus

Ursidae

Carnivora

Mammalia

Chordata

Animalia

Eukarya

(a) DOMAIN BACTERIA

(b) DOMAIN ARCHAEA

(c) DOMAIN EUKARYA

Protists

Kingdom Fungi

KingdomPlantae

Kingdom Animalia

Thre

e D

omai

n Sy

stem

Unity in the Diversity of Life

•A striking unit underlies the diversity of life:•DNA is the universal genetic

language common to all organisms.•Unity is evident in many features of

cell structure.

Cilia ofParamecium

Cross section of a cilium, as viewedwith an electron microscope

Cilia ofwindpipecells

15 µm 5 µm

0.1 µm

Evolution, Darwin and Natural Selection• 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”

Darwin observed that:

• Individuals in a population have traits that vary•Many of these traits are heritable

(passed from parents to offspring)•More offspring are produced than

survive• Competition is inevitable• Species generally suit their environment

Darwin inferred that:

• Individuals that are best suited to their environment are more likely to survive and reproduce• Over time, more individuals in a

population will have the advantageous traits

• In other words, the natural environment “selects” for beneficial traits

Populationwith variedinherited traits.

Eliminationof individualswith certaintraits.

Reproductionof survivors.

Increasingfrequencyof traits that enhance survival and reproductive success.

4321

Darwin proposed that natural selection could cause an ancestral species to give rise to two or more descendent species

COMMONANCESTOR

Warbler finches

Insect-eaters

Seed-eater Bud-eater

Insect-eaters

Tree finches

Green warbler finch Certhidea olivacea

Gray warbler finch Certhidea fusca

Sharp-beakedground finch Geospiza difficilisVegetarian finch Platyspiza crassirostris

Mangrove finch Cactospiza heliobates

Woodpecker finch Cactospiza pallida

Medium tree finch Camarhynchus pauper

Large tree finch Camarhynchus psittacula

Small tree finch Camarhynchus parvulus

Large cactusground finchGeospiza conirostrisCactus ground finchGeospiza scandens

Small ground finchGeospiza fuliginosa

Medium ground finchGeospiza fortis

Large ground finchGeospiza magnirostris

Ground finches

Seed-eaters

Cactus-flower-

eaters

Concept 1.3:Scientists use two main forms of inquiry in their study of nature

• Inquiry is the search for information and explanation•There are two main types of scientific inquiry: discovery science and hypothesis-based science

Discovery Science• This approach is based on

observation and the analysis of data• Data fall into two

categories• Qualitative, or descriptions

rather than measurements• Quantitative, or recorded

measurements, which are sometimes organized into tables and graphs

Inductive Reasoning

• Inductive reasoning draws conclusions through the logical process of induction

• Scientific method…

Observations

Question

Hypothesis #1:Dead batteries

Hypothesis #2:Burnt-out bulb

Test prediction

Hypothesis #1:Dead batteries

Hypothesis #2:Burnt-out bulb

Test prediction

Prediction:Replacing batterieswill fix problem

Prediction:Replacing bulbwill fix problem

Test falsifies hypothesis Test does not falsify hypothesis

Deduction: Logic of Hypothesis Based Science

• Deductive reasoning uses general premises to make specific predictions• For example, if organisms are made of

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

•A hypothesis must be testable and falsifiable•Failure to falsify a hypothesis does not prove that hypothesis

The Myth of the Scientific Method

• The scientific method is an idealized process of inquiry• Hypothesis-based science is based on the

“textbook” scientific method but rarely follows all the ordered steps• Discovery science has made important

contributions with very little dependence on the so-called scientific method

Limitations of Science

• In science, observations and experimental results must be repeatable• Science cannot support or falsify

supernatural explanations, which are outside the bounds of science