chapter 1 biology is the scientific study of life

Chapter 1

Biology is the scientific study of life

• Life is investigated from the microscopic (microbiology) to the global scale (global warming)

• Biological organization is based on a hierarchy of structural levels

Exploring Life

A Hierarchy (levels) of Biological Organization

Biosphere: all environments on Earth (the part of the earth, including air, land, surface rocks, and water, within which life occurs, and which biotic processes in turn alter or transform their envirnment).

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)

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.

Ecosystems

The biosphere

Organisms

Populations

Communities

Cells

Organelles

Molecules

Tissues

Organs and organ systems

Cell1 µm

Atoms

10 µm

50 µm

Life, a lot going on

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

Each organism interacts with its environment Both organism and environment affect each

other

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

Sunlight

Ecosystem

Heat

Heat

Chemicalenergy

Consumers(including animals)

Producers(plants and otherphotosynthetic

organisms)

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

25 µm

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

Sperm cell

NucleicontainingDNA

Egg cell

Fertilized eggwith DNA fromboth parents

Embryo’s cells With copies of inherited DNA

Offspring with traits inherited from both parents

DNA double helix Single strand of DNA

Nucleotide

Cell

Nucleus DNA

Eukaryotic and Prokaryotic 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

Membrane

Cytoplasm

EUKARYOTIC CELL PROKARYOTIC CELL

DNA(no nucleus)

Membrane

1 µm

Organelles

Nucleus (contains DNA)

Biologists explore life across a great diversity of species (1.8 million named)

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

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

Kingdoms and domains are the broadest units of classification

Taxonomy (naming species)

Ursidae

Ursus

Carnivora

Mammalia

Chordata

Animalia

Eukarya

Species Genus Family Order Class Phylum Kingdom DomainUrsusamericanus(Americanblack bear)

The Three Domains of Life

Bacteria (Most of the Known Prokaryotes )

Archaea (Prokaryotes of Extreme Environments )

Eukarya (eukaryotes) Eukaryotes include protists and the kingdoms

Plantae, Fungi, and Animalia

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Bacteria 4 µm 100 µm

0.5 µm

Kingdom PlantaeProtists

Kingdom AnimaliaKingdom FungiArchaea

Evolution accounts for life’s unity and diversity

The history of life is a continuing saga of a changing Earth billions of years old

How did we get where we are?

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

Gregor Johann Mendel 1822 - 1884

Evolution

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

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

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

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

Natural Selection (continued)

Population with varied inherited traits

Elimination of individuals with certain traits

Reproduction of survivors

Increasing frequency of traits that enhancesurvival and reproductive success

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.

Largeground finch

Large cactusground finch

Sharp-beakedground finch

Geospizamagnirostris

Geospizaconirostris

Mediumground finch

Geospizafuliginosa

Smallground finch

Woodpecker finch

Camarhynchuspsittacula

Large tree finch

Medium tree finch

Cactusground finch

Geospizadifficilis

Cactus flowereaters

Geospizascandens

Seed eater

Ground finches

Seed eaters

Tree finches

Common ancestor fromSouth American mainland

Insect eaters Bud eater

Warbler finches

Mangrove finchGeospiza

fortis

Cactospizapallida Small

tree finch

Camarhynchuspauper

Camarhynchusparvulus

Greenwarblerfinch

Graywarblerfinch

Certhideaolivacea

Certhideafusca

Vegetarianfinch

Platyspizacrassirostris

Cactospizaheliobates

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 (natural history): describing

nature Hypothesis-based science: explaining nature

Discovery Science (natural history)

Discovery science describes nature through careful observation and data analysis

Examples of discovery science: understanding cell structure expanding databases of genomes

Types of Data

Data are recorded observations

Two types of data: Quantitative data: numerical measurements Qualitative data: recorded descriptions

Induction in Discovery Science

Inductive reasoning involves generalizing based on many specific observations

The premises of an argument are believed to support the conclusion but do not ensure it.

• The stove top is hot: all stove tops are hot• A bird flies: all birds fly

Deduction: If the premises are true then the conclusion must be true

Hypothesis-Based Science

In science, inquiry usually involves proposing and testing hypotheses.

Hypotheses are hypothetical explanations.

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.

Hypothesis #1:Dead batteries

Hypothesis #2:Burnt-out bulb

Observations

Question

Observation: Flashlight does not work

Hypothesis #1:Dead batteries

Hypothesis #2:Burnt-out bulb

Test prediction

Test falsifies hypothesis

Prediction:Replacing batterieswill fix problem

Prediction:Replacing bulbwill fix problem

Test prediction

Test does not falsify hypothesis

Deduction: The “If…then”

Deductive reasoning, the logic flows from the general to the specific; thus, If a hypothesis is correct, then we can expect a particular outcome.

A scientific hypothesis must have two important qualities: It must be testable It must be falsifiable

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 – probably more true in biology than physics or chemistry.

In mimicry, a harmless species resembles a harmful species

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

A Case Study in Scientific Inquiry: Investigating Mimicry in Snake

Populations

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Flower fly (nonstinging)

Honeybee (stinging)

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

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Scarlet king snake

Eastern coralsnake

Scarlet king snake

Key

Range of scarlet king snake

NorthCarolina

Range of easterncoral snake

SouthCarolina

Field Experiments with Artificial Snakes

Artificial snakes:

An experimental group resembling king snakes

A control group resembling plain brown snakes

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(a) Artificial king snake

(b) Artificial brown snake that has been attacked

Equal numbers of both types were placed at field sites, including areas without coral snakes

After four weeks the artificial snakes were retrieved and bite/claw marks recordered

The data fit the predictions of the mimicry hypothesis

Field Experiments with Artificial Snakes (continued)

In areas where coral snakes were present, most attacks were on brown artificial snakes.

In areas where coral snakeswere absent, most attacks

were on artificial king snakes.

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% of attacks onartificial king snakes

% of attacks onbrown artificial snakes

Field site withartificial snakes

83%

NorthCarolina

SouthCarolina

17%

16%

84%

Key

• QUESTION:  How will the amount of fertilizer used  affect plant growth?

• HYPOTHESIS:  Increased dosages of fertilized will cause greater growth in tomato plants.

• TEST VARIABLE:  The amount of fertilizer used. • TEST CONSTANTS: • The seeds must all come from the same package. • All seeds must be planted in the same sized pots with similar soil. • All plants must receive exactly the same amount of water and light. • The temperature should be the same for all test plants. • More than one plant should be used in each test group (in case one

type of seed grows better at this time of year than another). • More than one seed should be placed in each container (in case one

seed is damaged). • Set one group as the CONTROL GROUP.  This group is not given

fertilizer. • Set up two other test groups.  Once receives a certain amount of

fertilizer and the other receives twice as much.