IB Biology Concepts and Methods of Exploring Life.

IB Biology

Concepts and Methods of Exploring Life

Biology: the study of life.IB Biology: a life of study!Seven characteristics of life:

Order- DNA is the genetic code (instructions for building molecules) Reproduction Growth and development of cells Energy Processing- metabolismResponsivenessHomeostasis/Regulation Evolution

Some properties of life

(c)

(a)

(d)

(g) (f)

(b)

(e)

Some properties of life

(c)

(a) Order/instruction

(d)

(g) (f)

(b)

(e)

Some properties of life

(c)

(a) Order/instruction

(d)

(g)(f)

(b) Evolutionary adaptation

(e)

Some properties of life

(c) Response to the environment

(a) Order/instruction

(d)

(g)(f)

(b) Evolutionary adaptation

(e)

Some properties of life

(c) Response to the environment

(a) Order/instruction

(d) Homeostasis

(g) (f)

(b) Evolutionary adaptation

(e)

Some properties of life

(c) Response to the environment

(a) Order/instruction

(d) Homeostasis

(g)(f)

(b) Evolutionary adaptation

(e) Energy processing

Some properties of life

(c) Response to the environment

(a) Order/instruction

(d) Homeostasis

(g)(f) Growth and development

(b) Evolutionary adaptation

(e) Energy processing

Some properties of life

(c) Response to the environment

(a) Order/instruction

(d) Homeostasis

(g) Reproduction (f) Growth and development

(b) Evolutionary adaptation

(e) Energy processing

Seven Characteristics

1. DNA is the genetic code which is organized into genes within cells.Genes: sets of instructions for making proteinsMutation: Changes in DNAHeredity: the passing of traits from parents to offspring

2. ReproductionEverything living must reproduce either by producing new cells within oneself or for the purposes of combining with another’s cells.

The molecular structure of DNAAccounts for its information-rich nature

DNA

Cell

Nucleotide

A

CT

A

T

A

C

C

G

G

T

A

T

A

(b) Single strand of DNA. These geometric shapes and letters are simple symbols for the nucleotides in a small section of one chain of a DNA molecule. Genetic information is encoded in specific sequences of the four types of nucleotides (their names are abbreviated here as A, T, C, and G).

(a) DNA double helix. This model shows each atom in a segment of DNA.Made up of two long chains of building blocks called nucleotides, a DNA molecule takes the three-dimensional form of a double helix.

Nucleus

The Cell’s Heritable Information

Cells contain chromosomes made partly of DNA, the substance of genes

NucleicontainingDNA

The Cell’s Heritable Information

Cells contain chromosomes made partly of DNA, the substance of genes

Egg cell

Sperm cell

NucleicontainingDNA

The Cell’s Heritable Information

Cells contain chromosomes made partly of DNA, the substance of genes

Egg cell

Sperm cell

NucleicontainingDNA

Zygote = Fertilized Egg with DNA fromboth parents

Embyro’s cells with copies of inherited DNA

The Cell’s Heritable Information

Cells contain chromosomes made partly of DNA, the substance of genes

Which program the cells’ production of proteins and transmit information from parents to offspring

Egg cell

Sperm cell

NucleicontainingDNA

Fertilized eggwith DNA fromboth parents

Embyro’s cells with copies of inherited DNA

Offspring with traitsinherited fromboth parents

A Closer Look at Cells

The cellIs the lowest level of organization that can perform all activities required for life

25 µm

Seven Characteristics

3. Growth and Development of Cells

Cells typically grow in size before dividing into two new cells.Increase in overall number of cells is typical for organism that develop from zygotes to full size adults.Cells within an organism share the same DNA but may have different jobs associated with the genes that are used by particular cells.

Seven Characteristics4. Metabolism: the sum of all chemical reactions

Organisms use energy to do thingsAlmost all energy that organisms use originally was captured from the sun by plants.Energy flows from sun to plants to other living things.

5. Responsiveness: change to environmental stimuli requires the use of receptors which can sense shifts in the surrounding world.

6. Homeostasis: the maintenance of a stable internal environment-Ex. Blood sugar levels in humans.

Biologists explore life from the microscopic to the global scale

The study of lifeExtends from the microscopic scale of molecules and cells to the global scale of the entire living planet

Levels of Biological OrganizationThe hierarchy of life

Extends through many levels of biological organization

From the biosphere to organisms

1 The biosphere

From the biosphere to organisms

1 The biosphere

2) The ecosystem

3) The community

4) The population

5) The organism

From cells to molecules

Cell

6 Organs and organ systems

50 µm

10 µm

1 µm

Atoms

From cells to molecules

Cell

6 Organs and organ systems

7 Tissues

50 µm

10 µm

1 µm

Atoms

From cells to molecules

Cell

8 Cells

6 Organs and organ systems

7 Tissues

9

50 µm

10 µm

1 µm

Atoms

From cells to molecules

Cell

8 Cells

6 Organs and organ systems

7 Tissues

10

9 Organelles

50 µm

10 µm

1 µm

Atoms

From cells to molecules

Cell

8 Cells

6 Organs and organ systems

7 Tissues

10 Molecules

9 Organelles

50 µm

10 µm

1 µm

Atoms

A Closer Look at Ecosystems

Each organismInteracts with its environmentBoth organism and environment are affected by the interactions between them

Ecosystem Dynamics

The dynamics of any ecosystem include two major processes

Cycling of nutrients, in which materials acquired by plants eventually return to the soilThe one-way flow of energy from sunlight to producers to consumers• Dung Beetle Example

Energy Conversion

Activities of lifeRequire organisms to perform work, which depends on an energy source

All Living Things are Connected

The exchange of energy between an organism and its surroundings

Often involves the transformation of one form of energy to another

Energy flows through an ecosystemUsually entering as sunlight and exiting as heat

Producers

(plants and other

photosyntheticorganisms)

Consumers(including animals)

Sunlight

Chemical

energy

Heat

Heat

Ecosystem

Seven Characteristics

7. Evolution: a change in the inherited traits of a species over timeSpecies: a group of organisms that can interbreed to produce fertile offspringNatural selection: process by which evolution takes place, survival of the fittest

Two Main Forms of Cells

All cells share certain characteristicsThey are all enclosed by a membraneThey all use DNA as genetic information

Two Main Forms of CellsEukaryotic cells• Are subdivided by internal membranes

into various membrane-enclosed organelles

Prokaryotic cells• Lack the kinds of membrane-enclosed

organelles found in eukaryotic cells

Two Main Forms of Cells

EUKARYOTIC CELL

Membrane

Cytoplasm

Organelles

Nucleus (contains DNA) 1 µm

PROKARYOTIC CELL

DNA

(no nucleus)Membrane

Taxonomy seeks to classify

Biologists explore life across its great diversity of species

Classifying life

Domain

Eukarya

Classifying life

Kingdom Domain

Animalia

Eukarya

Classifying life

Phylum Kingdom Domain

Chordata

Animalia

Eukarya

Classifying life

Class Phylum Kingdom Domain

Mammalia

Chordata

Animalia

Eukarya

Classifying life

Order Class Phylum Kingdom Domain

Mammalia

Carnivora

Chordata

Animalia

Eukarya

Classifying life

Family Order Class Phylum Kingdom Domain

Mammalia

Ursidae

Carnivora

Chordata

Animalia

Eukarya

Classifying life

Genus Family Order Class Phylum Kingdom Domain

Mammalia

Ursus

Ursidae

Carnivora

Chordata

Animalia

Eukarya

Classifying life

Species Genus Family Order Class Phylum Kingdom Domain

Mammalia

Ursusameri-canus(Americanblack bear)

Ursus

Ursidae

Carnivora

Chordata

Animalia

Eukarya

The Three Domains of Life

At the highest level, life is classified into three domains

BacteriaArchaeaEukarya

Domain Bacteria and domain Archaea

Consist of prokaryotes

Domain Eukarya, the eukaryotesIncludes Protista, Plantae, Fungi, and Animalia

Life’s three domains

100 µm

0.5 µm

4 µmBacteria are the most diverse and widespread prokaryotes and are now divided among multiple kingdoms. Each of the rod-shapedstructures in this photo is a bacterial cell.

Protists (multiple kingdoms)are unicellular eukaryotes and their relatively simple multicellular relatives.Pictured here is an assortment of protists inhabiting pond water. Scientists are currently debating how to split the protistsinto several kingdoms that better represent evolution and diversity.

Kingdom Plantae consists of multicellula eukaryotes that carry out photosynthesis, the conversion of light energy to food.

Many of the prokaryotes known as archaea live in Earth‘s extreme environments, such as salty lakes and boiling hot springs. Domain Archaea includes multiple kingdoms. The photoshows a colony composed of many cells.

Kindom Fungi is defined in part by thenutritional mode of its members, suchas this mushroom, which absorb nutrientsafter decomposing organic material.

Kindom Animalia consists of multicellular eukaryotes thatingest other organisms.

DOMAIN ARCHAEA

The History of Life

Is a saga of a changing Earth billions of years old

Evolution accounts for life’s unity and diversity

The evolutionary view of life

Came into sharp focus in 1859 when Charles Darwin published On the Origin of Species by Natural Selection

The Origin of Species articulated two main points

Descent with modificationNatural selection• Ex. Orchids show

remarkable similarities and differences in their ability to attract pollinators

Natural Selection• The mechanism

for evolutionary adaptation of populations to their environments

Populationof organisms

Natural Selection• The mechanism

for evolutionary adaptation of populations to their environments

Populationof organisms

Hereditaryvariations

Overproductionand struggle forexistence

Natural Selection• The mechanism

for evolutionary adaptation of populations to their environments

Populationof organisms

Hereditaryvariations

Differences in reproductive success

Overproductionand struggle forexistence

Natural Selection• The mechanism

for evolutionary adaptation of populations to their environments

Populationof organisms

Hereditaryvariations

Differences in reproductive success

Evolution of adaptationsin the population

Overproductionand struggle forexistence

The products of natural selectionAre often exquisite adaptations of organisms to the special circumstances of their way of life and their environment

The Tree of Life

Darwin proposed that natural selection

Could enable an ancestral species to “split” into two or more descendant species, resulting in a “tree of life”Large

ground finchSmallground

finch

Geospiza

magnirostris

Seed eater

Sharp-beaked

ground finch

Camarhynchus

psitacula

Green

warbler

finch

Large

tree finchLarge cactusground finch

Ground finches Tree finches

Insect eaters Bud eater

Warbler finches

Common ancestor fromSouth American mainland

Gray

warbler

finch

Certhidea

olivacea

Certhidea

fuscaGeospiza

difficilis

Cactus flowereater

Geospizascandens

Seed eater

Geospiza

conirostris

Geospiza

fortis

Mediumground

finch

Geospizafuliginosa

Mangrovefinch

Cactospiza

heliobates

Cactospizapallida

Woodpecker

finch

Mediumtree finch

Camarhynchuspauper

Small tree finch

Vegetarianfinch

Camarhynchusparvulus

Platyspizacrassirostris

Cactusground finch

Each species is on twig of a branching tree of life

Extending back in time through ancestral species more and more remote

Using inquiry to explore life

At the heart of science is inquiryA search for information and explanation, often focusing on specific questions

Biology blends two main processes of scientific inquiry

Discovery scienceHypothesis-based science

The Scientific Method

Step #1: ObservationStep #2: Make hypothesesStep #3: Test or ExperimentStep #4: Draw ConclusionsStep #5: Publish or Communicate Results

The Scientific Process

Observation: the act of noting or perceiving objects or events using the senses

Asking a question: after making observations ask about what you want to find out.

Hypothesis: an explanation to your question that might be true and is testable.

Prediction: the expected outcome of the test, assuming the hyp. is correct

Induction in Discovery Science

In inductive reasoningScientists derive generalizations based on a large number of specific observations

Hypothesis-Based Science

In science, inquiry that asks specific questions

Usually involves the proposing and testing of hypothetical explanations, or hypotheses

The Role of Hypotheses in Inquiry

In science, a hypothesisIs a tentative answer to a well-framed question, an explanation on trialMakes predictions that can be tested

We all use hypotheses in solving everyday problems

Observations

Questions

Hypothesis # 1: Hypothesis # 2:

We all use hypotheses in solving everyday problems

Observations

Questions

Hypothesis # 1:Dead batteries

Hypothesis # 2:Burnt-out bulb

We all use hypotheses in solving everyday problems

Observations

Questions

Hypothesis # 1:Dead batteries

Hypothesis # 2:Burnt-out bulb

Prediction:Replacing batterieswill fix problem

Prediction:Replacing bulbwill fix problem

We all use hypotheses in solving everyday problems

Observations

Questions

Hypothesis # 1:Dead batteries

Hypothesis # 2:Burnt-out bulb

Prediction:Replacing batterieswill fix problem

Prediction:Replacing bulbwill fix problem

Test prediction Test prediction

We all use hypotheses in solving everyday problems

Observations

Questions

Hypothesis # 1:Dead batteries

Hypothesis # 2:Burnt-out bulb

Prediction:Replacing batterieswill fix problem

Prediction:Replacing bulbwill fix problem

Test prediction

Test does not falsify hypothesis

Test prediction

Test falsifies hypothesis

Deduction: The “If…then” Logic of Hypothesis-Based Science

In deductive reasoningThe logic flows from the general to the specific

If a hypothesis is correctThen we can expect a particular outcome

A Closer Look at Hypotheses in Scientific Inquiry

A scientific hypothesis must have two important qualities

It must be testableIt must be falsifiable

The Myth of the Scientific Method

• The scientific method– Is an idealized process of inquiry

• Very few scientific inquiries– Adhere to the “textbook” scientific

method

Test or Experiment Experiment: planned procedure to

test a hypothesis Control group: experimental group

that receives no experimental treatment

Independent variable: the factor that is varied.

Dependent variable: the variable that is measured, result of experiment.

Types of Data

• Data– Are recorded

observations– Can be

quantitative or qualitative

Jane Goodall observing chimpanzee behavior

Drawing conclusions: deciding if the data supports the hypothesis

Publish: Usually communicate your findings with others.

• In mimicry– A harmless species resembles a

harmful species

Flower fly(non-stinging)

Honeybee (stinging)

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

Snake Mimicry case study• Mimicry in king snakes is examined• The 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

Scarlet king snake

Scarlet king snakeKeyRange of scarlet king snake

Range of eastern color snake

Eastern coral snake

NorthCarolina

SouthCarolina

Field Experiments with Artificial Snakes

• To test this mimicry hypothesis– Researchers made hundreds of artificial snakes,

an experimental group resembling king snakes and a control group of plain brown snakes

(a) Artificial king snake

(b) Brown artificial snake that has been attacked

• After a given period of time– The

researchers collected data that fit a key prediction

In areas where coral snakes were present, most attacks were onartificial brown snakes

Key

% of attacks on artificial king snakes

% of attacks on brown artificial snakes

Field site with artificial snakes

17%

83%

NorthCarolina

SouthCarolina

XX

XX X

XX

X XX

XXXX

In areas where coral snakeswere absent, most attacks

were on artificial king snakes

84%

16%

Key

Designing Controlled Experiments

• Experiments must be designed to test– The effect of one variable by testing

control groups and experimental groups in a way that cancels the effects of unwanted variables

Theories

• Theory: a set of related hypotheses that have been tested and confirmed many times.

• Theories to scientists are what they believe is true.– Ex. Spontaneous Generation (Redi’s

experiment followed by Needham & Spallanzani and finally Pasteur)

Limitations of Science

• Science cannot address supernatural phenomena– Because hypotheses must be

testable and falsifiable and experimental results must be repeatable