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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