Transcript Levels of Organization and Classification of Life

The Characteristics of Life
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juxLuo-sH6M
Why Study Biology?
• To learn how organisms are
constructed, how they function, where
they live, and what they do
• To help you develop, modify, and refine
your ideas about life
What is Biology?
 The study of living
things (organisms)
The study of
interactions of living
things
 “bio”-life
“ology”-study of
1. Living Things are made up
of Cells.
Unicellu
lar
a.) CELL: Collection of living
material enclosed within a
barrier
b.) cells are basic unit of life
c.) Unicellular: made up of one
cell
d.) Multicellular: made up of
many cells
Multicellular
Asexual
2. Living Things Reproduce:
a.) produce offspring which
resemble parents
b.) asexual reproduction: has
only one parent
Sexual
c.) sexual reproduction:
requires two parents, usually
with egg and sperm.
3. Living things are based on a universal
genetic code.
a. Offspring always resemble their
parents
b. Genetic code of DNA determines
inherited traits
4. Living things Grow and Develop
a.) GROWTH: increase in size & shape
b.) DEVELOPMENT: mature over time
c.) living things have a lifespan
Growth
Development
As development occurs
process called aging
takes place. Death, too, is
a process of change that
separates living and
nonliving things. Cell
Death is called Apoptosis
5. Living Things Use & Need
Energy
a.) energy comes from food, used to
maintain body
b.) AUTOTROPH: produce own food
c.) HETEROTROPH: must consume
food
d.) DECOMPOSER: breaks down dead
material for food
6. Living things respond to
their surroundings
a.) they react to a stimulus
b.) an action causes a reaction
c. ) reaction is called a response
d.) this involves one individual
7. Living things maintain a stable internal
environment
a.) HOMEOSTASIS: internal balance
b.) examples: sweating, panting, shivering, etc.
8. Living things Evolve
a.) adapt to long-range
changes in environment
b.) change to better survive in
environment
c.) these changes take place
over a long period of time &
involve the entire species
8. Taken as a group, living things change over
time (evolution– individuals don’t usually change
basic traits over lifetime, but as group can evolve,
or change over time)
B. Branches and Levels of Study
1. The broad field of Biology contains many
branches
a. Some divisions based on type of
organism
studied (ie. Zoologists,
botanist,
microbiologists, herpetologists,
b. Others study life
etc.)
from a particular
perspective (ie.
Ethologist– study
animal behavior,
paleontologists, etc,)
Basic Unit of Life - The Cell
• Characteristics of life emerge at the
level of cells
• A cell is the smallest unit having the
capacity to live and reproduce
Higher Levels of
Organization
Cell
Tissue
Organ
Organ System
Organism
Population
Community
Ecosystem
Biosphere
Molecules of Life
• All things are made up of the same units
of matter:
– atoms, molecules
• Living things are made of up of a certain
subset of molecules:
– nucleic acids, proteins, carbohydrates,
lipids
DNA (Deoxyribonucleic acid)
• The signature
molecule of life
• Molecule of
inheritance
• Directs assembly
of amino acids
Heritability of DNA
Inheritance
– Acquisition of traits by way of
transmission of DNA from parent to
offspring
Reproduction
– Mechanisms by which an organism
produces offspring
– Governed by instructions in DNA
DNA Guides Development
Development
– Transformation from fertilized egg to adult
– Series of stages
– Instructions for each stage in DNA
Nothing Lives Without Energy
Energy = Capacity to do work
Metabolism = Reactions by which
cells acquire and use energy to
grow, survive, and reproduce
Sensing and Responding
• Organisms sense changes in their
environment and make responses to
them
• Receptors detect specific forms of
energy
• The form of energy detected by a
receptor is a stimulus
Homeostasis
• Maintenance of internal environment
within range suitable for cell activities
• Pancreas maintains level of sugar in
blood by secreting hormones
Higher Levels of Organization
Cell
Multicelled Organism
Population
Community
Ecosystem
Biosphere
Interdependencies Among
Organisms
Producers
Make their own food
Consumers
Depend on energy stored in tissues
of producers
Decomposers
Break down remains and wastes
Energy Flow
• Usually starts with energy
from sun
• Transfer from one organism
to another
• Energy flows in one direction
• Eventually, all energy flows
back to the environment
P roducers capture, convert, and
use or store some energy from
the sun.
PRODUCERS
NUTRIENT
CYCLING
CONSUMERS,DECOMPOSERS
ONE-WAY FLOW
OF ENERGY
Energy gets transferred from one
organism to another; in time, all flows
back to the environment.
Fig. 1.6, p. 7
Unity of Life
All organisms:
– Are composed of the same substances
– Engage in metabolism
– Sense and respond to the environment
– Have the capacity to reproduce based
on instructions in DNA
Diversity of Life
• Millions of living species
• Additional millions of species now
extinct
• Classification scheme attempts to
organize this diversity
Scientific Names
• Two-part naming system devised by
Carolus Linnaeus
• First name is genus (plural, genera)
– Homo sapiens - genus is Homo
• Second name is species within genus
Taxa
Kingdom
Phylum
Class
Order
Genus
Species
The Six Kingdoms
Archaebacteria or Archaea
Eubacteria
Protista
Fungi
Plantae
Animalia
Prokaryotic Kingdoms
• Archaebacteria and Eubacteria
• Single cells
• No nucleus or organelles
• Includes producers, consumers,
and decomposers
Eukaryotic Kingdoms
• Protista, Fungi, Plantae, Animalia
• DNA is inside a nucleus
• Most are larger and more complex than
the prokaryotes
Protistans
• Not an easily defined group
• Producers and consumers
• Single-celled and multi-cellular
species
Fungi
• Most are multicelled
• Consumers and decomposers
• Extracellular digestion and
absorption
Plants
• All are multicelled
• Most are photosynthetic
producers
• Make up the food base for
communities, especially on
land
Animals
• Multicelled consumers
– Herbivores
– Carnivores
– Parasites
– Scavengers
• Move about during at least
some stage of their life
Mutation: Source of Variation
• Mutation = change in structure of DNA
• Basis for the variation in heritable traits
• Most are harmful
Adaptive Trait
A trait that gives the individual an
advantage in survival or reproduction,
under a given set of circumstances
Evolution
• Genetically
based change in
a line of descent
over time
• Population
changes, not
individuals
Artificial Selection
• Breeders favor some form of traits over
others
• Individuals exhibiting favored traits are
bred
• Favored traits increase in the population
Natural Selection
• The outcome of differences in survival
and reproduction among individuals that
vary in details of heritable traits
• This process helps explain evolution changes in a line of descent over
generations
Antibiotic Resistance
• Antibiotics are used to kill bacteria
• Mutations for antibiotic resistance exist
or arise in bacterial population
• Antibiotic-resistant bacteria survive and
reproduce better than non-resistant
• Over time, proportion of antibioticresistant bacteria increases
Scientific Method
• Observe phenomenon
• Develop hypotheses
• Make predictions
• Devise test of predictions
• Carry out test and analyze results
Inductive Logic
• Using observations and facts to arrive at
generalizations or hypotheses
• Observation: Eagles, swallows, and
robins have feathers
• Hypothesis: All birds have feathers
Deductive Logic
• Drawing a specific conclusion based on
a generalization
– Generalization - Birds have feathers
– Example - Eagles are birds
– Conclusion - Eagles have feathers
Role of Experiments
• Procedures used to study a
phenomenon under known conditions
• Allows you to predict what will happen if
a hypothesis is not wrong
• Can never prove a hypothesis 100%
correct
Experimental Design
• Control group
– A standard for comparison
– Identical to experimental group except for
variable being studied
• Sampling error
– Non-representative sample skews results
– Minimize by using large samples
Draw samples from some aspect of nature
CONTROL GROUP
The variable being
tested is absent
EXPERIMENTAL GROUP
The variable being
tested is present
Compile results
Compile results
Compare and analyze the test results
Report on experimental design, test results,
and conclusions drawn from results
Fig. 1.10, p. 12
Scientific Theory
• A hypothesis that has been tested for its
predictive power many times and has
not yet been found incorrect
• Has wide-ranging explanatory power
– Darwin’s Theory of Evolution by Natural
Selection
Biological Therapy
Experiments
Can we use viruses that attack bacteria
(bacteriophages) to fight infections?
Experiment 1
• Hypothesis - Bacteriophages can
protect mice against infectious bacteria
• Prediction - Mice injected with
bacteriophages will not die as a result of
bacterial injection
Experiment 1 - Test
• Experimental group
Inject with bacteria and
bacteriophage
• Control group
Inject with bacteria and saline
Experiment 1 Results & Conclusion
• Experimental group
All mice lived
• Control group
All mice died
• Conclusion - Bacteriophage injections
protect mice against bacterial infections
Experiment 2
• Prediction - Bacteriophage injections
will be more effective treatment than
single dose of the antibiotic
streptomycin
• Test - Mice injected with bacteria, then
with saline, streptomycin, or
bacteriophage
Experiment 2 - Results
• When 2nd injection was:
– Bacteriophage - 11 of 12 mice lived
– 60mg/gm streptomycin - 5 of 12 lived
– 100mg/gm streptomycin - 3 of 12 lived
– Saline - all mice died
• Conclusion - Bacteriophage treatment can be
as good or better than antibiotics
Minimizing Variables
• All mice were same age and sex, reared
under same conditions
• Each mouse in each test group received
exact same treatment
• All mice in control group received same
amount of saline
• Variable tested was antibiotic treatment
versus bacteriophage treatment
Limits of Science
• Scientific approach cannot provide
answers to subjective questions
• Cannot provide moral, aesthetic, or
philosophical standards
Science and the Supernatural
• Science has run up against religious
belief systems
– Copernicus suggested that sun, not the
Earth, was center of universe
– Darwin suggested that life was shaped by
evolution, not a single creation event
Asking Questions
• Scientists still ask questions that
challenge widely held beliefs
• The external world, not internal
conviction, is the testing ground for
scientific beliefs