Transcript You Light Up My Life

Invitation to Biology
Chapter 1
Life’s Levels of Organization
• The world of life shows levels of
organization, from the simple to the
complex, which extend through:
– cells
– populations
– communities
– ecosystems
– the 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
Energy Is the Basis
of Metabolism
Energy = Capacity to do work
Metabolism = Reactions by which
cells acquire and use energy to
grow, survive, and reproduce
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
energy input (mainly sunlight)
producers
(plants and other self-feeding organisms;
they make their own food from simple raw materials)
nutrient
cycling
consumers, decomposers
(animals, most fungi, many protists,
many bacteria that can’t make their own food)
energy output (mainly metabolic heat)
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
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
Three-Domain Classification
• Bacteria
• Archaea
• Eukarya (includes protists, plants, fungi,
and animals)
Bacteria
(EUBACTERIA)
Archaea
(ARCHAEBACTERIA)
Eukarya
(EUKARYOTES)
Life’s Diversity
Prokaryotes
Archaea and Bacteria
• Single-celled
• No nucleus or organelles
• Include producers, consumers,
decomposers
Eukaryotes
Eukarya (plants, fungi, animals, protists)
• DNA is inside a nucleus
• Most are larger and more complex than the
prokaryotes
Plants
• All are multicelled
• Most are photosynthetic
producers
• Make up the food base for
communities, especially on
land
Fungi
• Most are multicelled
• Consumers and decomposers
• Extracellular digestion and
absorption
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
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
Artificial Selection
• Breeders favor some form of traits over
others
• Individuals exhibiting favored traits are
bred
• Favored traits increase in the population
Observations, Hypotheses,
and Tests
• Observe phenomenon
• Develop hypotheses
• Make predictions
• Devise test of predictions
• Carry out test and analyze results
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
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
Make Prediction
If Olestra® potato chips cause
intestinal distress then people
who eat them will get cramps
CONTROL GROUP
Gets regular
potato chips
EXPERIMENTAL GROUP
Gets Olestra
potato chips
Perform Experiment
Eat potato chips
Eat potato chips
Analyze Results
93 of 529 people (17.6%)
suffer from cramps later
89 of 563 people (15.8%)
suffer from cramps later
About the same number of people in each group get cramps
Draw Conclusion
Eating Olestra potato chips
does not cause intestinal distress
Control Group
34 H. cydno
individuals
with yellow markings
Experimental
Group
46 H. cydno
individuals
with white markings
Field Experiment
• Study of Heliconius
butterflies
Experiment
Both yellow and white forms
of H. cydno butterflies are
introduced into isolated
rain forest habitat of yellow
H. eleuchia butterflies.
Numbers of individuals
resighted recorded on a
daily basis for two weeks.
Results
Experimental group (H. cydno individuals
without yellow wing markings) is selected
against. 37 of the original group of 46
white butterflies disappear (80%), compared
with 20 of the 34 yellow controls (58%).
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