Transcript Intro to Biology

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- metabolism
Responsiveness
Homeostasis/Regulation
Evolution
Some properties of life
(b)
(a)
(c)
(e)
(d)
(f)
(g)
Some properties of life
(b)
(a) Order/instruction
(c)
(e)
(d)
(f)
(g)
Some properties of life
(a) Order/instruction
(b) Evolutionary
adaptation
(c)
(e)
(d)
(f)
(g)
Some properties of life
(a) Order/instruction
(b) Evolutionary
adaptation
(c) Response to the
environment
(e)
(d)
(f)
(g)
Some properties of life
(a) Order/instruction
(b) Evolutionary
adaptation
(c) Response to the
environment
(e)
(d) Homeostasis
(f)
(g)
Some properties of life
(a) Order/instruction
(b) Evolutionary
adaptation
(c) Response to the
environment
(d) Homeostasis
(e) Energy
processing
(f)
(g)
Some properties of life
(a) Order/instruction
(b) Evolutionary
adaptation
(c) Response to the
environment
(d) Homeostasis
(e) Energy
processing
(f) Growth and
development
(g)
Some properties of life
(a) Order/instruction
(b) Evolutionary
adaptation
(c) Response to the
environment
(d) Homeostasis
(e) Energy
processing
(f) Growth and
development
(g) Reproduction
Seven Characteristics
1. DNA is the genetic code which is
organized into genes within cells.
Genes: sets of instructions for making proteins
Mutation: Changes in DNA
Heredity: the passing of traits from parents to
offspring
2. Reproduction
Everything living must reproduce either by
producing new cells within oneself or for the
purposes of combining with another’s cells.
The molecular structure of DNA
Accounts for its information-rich nature
Nucleus
DNA
Cell
A
Nucleotide
C
T
A
T
A
C
C
G
T
A
G
T
A
(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.
(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).
The Cell’s Heritable Information
Cells contain chromosomes made partly of
DNA, the substance of genes
Nuclei
containing
DNA
The Cell’s Heritable Information
Cells contain chromosomes made partly of
DNA, the substance of genes
Sperm cell
Nuclei
containing
DNA
Egg cell
The Cell’s Heritable Information
Cells contain chromosomes made partly of
DNA, the substance of genes
Sperm cell
Nuclei
containing
DNA
Egg cell
Zygote = Fertilized
Egg with DNA from
both 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
Sperm cell
Nuclei
containing
DNA
Egg cell
Fertilized egg
with DNA from
both parents
Embyro’s cells
with copies of
inherited DNA
Offspring with traits
inherited from
both parents
A Closer Look at Cells
The cell
Is 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 Characteristics
4. Metabolism: the sum of all chemical reactions
Organisms use energy to do things
Almost 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 life
Extends from the microscopic scale of
molecules and cells to the global scale of the
entire living planet
Levels of Biological
Organization
The 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
1 µm
Cell
Atoms
10 µm
50 µm
6 Organs and organ systems
From cells to molecules
1 µm
Cell
Atoms
10 µm
7 Tissues
50 µm
6 Organs and organ systems
From cells to molecules
9
1 µm
Cell
8 Cells
Atoms
10 µm
7 Tissues
50 µm
6 Organs and organ systems
From cells to molecules
9 Organelles
1 µm
Cell
8 Cells
Atoms
10 µm
7 Tissues
50 µm
6 Organs and organ systems
10
From cells to molecules
9 Organelles
1 µm
Cell
8 Cells
Atoms
10 µm
7 Tissues
50 µm
6 Organs and organ systems
10 Molecules
A Closer Look at Ecosystems
Each organism
Interacts with its environment
Both 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 soil
The one-way flow of energy from sunlight
to producers to consumers
• Dung Beetle Example
Energy Conversion
Activities of life
Require 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 ecosystem
Usually entering as sunlight and exiting as heat
Sunlight
Ecosystem
Producers
(plants and other
photosynthetic
organisms)
Heat
Chemical
energy
Consumers
(including animals)
Heat
Seven Characteristics
7. Evolution: a change in the inherited
traits of a species over time
Species: a group of organisms that can
interbreed to produce fertile offspring
Natural selection: process by which
evolution takes place, survival of the
fittest
Two Main Forms of Cells
All cells share certain characteristics
They are all enclosed by a membrane
They all use DNA as genetic information
Two Main Forms of Cells
Eukaryotic 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
PROKARYOTIC CELL
DNA
(no nucleus)
Membrane
Cytoplasm
Organelles
Nucleus (contains DNA)
1 µm
Taxonomy seeks to classify
Biologists explore life across its great
diversity of species
Classifying life
Domain
Eukarya
Classifying life
Kingdom
Animalia
Eukarya
Domain
Classifying life
Phylum
Chordata
Animalia
Eukarya
Kingdom
Domain
Classifying life
Class
Phylum
Mammalia
Chordata
Animalia
Eukarya
Kingdom
Domain
Classifying life
Order
Class
Phylum
Carnivora
Mammalia
Chordata
Animalia
Eukarya
Kingdom
Domain
Classifying life
Family
Order
Class
Phylum
Ursidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya
Kingdom
Domain
Classifying life
Genus Family
Order
Class
Phylum
Ursus
Ursidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya
Kingdom
Domain
Classifying life
Species Genus Family
Order
Class
Phylum
Ursus
americanus
(American
black bear)
Ursus
Ursidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya
Kingdom
Domain
The Three Domains of Life
At the highest level, life is classified into
three domains
Bacteria
Archaea
Eukarya
Domain Bacteria and domain Archaea
Consist of prokaryotes
Domain Eukarya, the eukaryotes
Includes Protista, Plantae, Fungi, and
Animalia
Life’s three domains
4 µm
Bacteria are the most diverse
and widespread prokaryotes
and are now divided among multiple
kingdoms. Each of the rod-shaped
structures in this photo is a bacterial cell.
DOMAIN ARCHAEA
Many of the prokaryotes known
0.5 µm
as archaea live in Earth‘s
extreme environments, such as salty lakes
and boiling hot springs. Domain Archaea
includes multiple kingdoms. The photo
shows a colony composed of many cells.
100 µm
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 protists
into several kingdoms that better represent evolution
and diversity.
Kindom Fungi is defined in part by the
nutritional mode of its members, such
as this mushroom, which absorb
nutrientsafter decomposing organic
material.
Kingdom Plantae consists of
multicellula eukaryotes that carry
out photosynthesis, the conversion
of light energy to food.
Kindom Animalia consists of
multicellular eukaryotes that
ingest other organisms.
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
modification
Natural 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
Population
of organisms
Natural Selection
• The mechanism
for evolutionary
adaptation of
populations to
their environments
Population
of organisms
Hereditary
variations
Overproduction
and struggle for
existence
Natural Selection
• The mechanism
for evolutionary
adaptation of
populations to
their environments
Population
of organisms
Hereditary
variations
Overproduction
and struggle for
existence
Differences in
reproductive success
Natural Selection
• The mechanism
for evolutionary
adaptation of
populations to
their environments
Population
of organisms
Hereditary
variations
Overproduction
and struggle for
existence
Differences in
reproductive success
Evolution of adaptations
in the population
The products of natural selection
Are 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”
Each species is on
twig of a branching
tree of life
Extending back
in time through
ancestral species
more and more
remote
Large
ground finch
Large cactus
ground finch
Small
ground
finch
Large
tree finch
Camarhynchus
Green
Geospiza
Gray
Geospiza
magnirostris
psitacula
warbler
warbler
Sharp-beaked
fuliginosa
Woodpecker Medium
Geospiza Medium
finch
finch
tree
finch
ground finch
finch
conirostris ground
finch
Certhidea Certhidea
GeospizaCactus
Cactospiza Camarhynchus olivacea fusca
difficilis ground finch
pauper
pallida
Geospiza Mangrove
Small tree finch
finch
fortis
Geospiza
Camarhynchus
Cactospiza
scandens
parvulus
heliobates
Vegetarian
Seed eater
Seed eater Cactus flower
finch
eater
Platyspiza
crassirostris
Insect eaters
Ground finches
Tree finches
Bud eater
Warbler finches
Common ancestor from
South American mainland
Using inquiry to explore life
At the heart of science is inquiry
A search for information and explanation,
often focusing on specific questions
Biology blends two main processes of
scientific inquiry
Discovery science
Hypothesis-based science
The Scientific Method
Step
Step
Step
Step
Step
#1:
#2:
#3:
#4:
#5:
Observation
Make hypotheses
Test or Experiment
Draw Conclusions
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 reasoning
Scientists 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 hypothesis
Is a tentative answer to a well-framed
question, an explanation on trial
Makes 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 batteries
will fix problem
Prediction:
Replacing bulb
will fix problem
We all use
hypotheses in
solving everyday
problems
Observations
Questions
Hypothesis # 1:
Dead batteries
Hypothesis # 2:
Burnt-out bulb
Prediction:
Replacing batteries
will fix problem
Prediction:
Replacing bulb
will 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 batteries
will fix problem
Prediction:
Replacing bulb
will fix problem
Test prediction
Test falsifies hypothesis
Test prediction
Test does not falsify hypothesis
Deduction: The “If…then” Logic
of Hypothesis-Based Science
In deductive reasoning
The logic flows from the general to the
specific
If a hypothesis is correct
Then 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 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 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.
A Case Study in Scientific Inquiry: Investigating
Mimicry in Snake Populations
In mimicry
A harmless species resembles a harmful
species
Flower fly
(non-stinging)
Honeybee (stinging)
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
Key
Range of scarlet king snake
Range of eastern color snake
North
Carolina
South
Carolina
Eastern coral snake
Scarlet king snake
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
Key
Key
% of attacks on artificial king snakes
% of attacks on brown artificial snakes
Field site with artificial snakes
17%
In areas where coral snakes
were absent, most attacks
were on artificial king snakes
North
Carolina
South
Carolina
83%
X
XX
X
XX
X
X X
X
XX
X
X
16%
84%
In areas where coral
snakes were present,
most attacks were on
artificial brown snakes
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