121 ch1 introduction
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Biology 121 – Concepts of BiologyDr. Fritzler
Chapter 1Chapter 1
Introduction: Biology Today
• We are living in a golden age of biology.
• Biology provides exciting breakthroughs changing our culture.
– Genetics and cell biology are revolutionizing medicine and agriculture
– Molecular biology is solving crimes and revealing ancestries.
– Ecology helps us address environmental issues.
– Neuroscience and evolutionary biology are reshaping psychology and sociology.
Biology and Society: Biology All Around Us
• Biology is the scientific study of life.
– How does “life” differ from “non-life”?
– Where does “life” start?
– What is “nature”?
The Properties of Life
1) Order – complex but ordered organization
2) Regulation – outside environment may change, but organism can regulate inner environment
- Homeostasis
The Seven Properties of Life
3) Growth & Development – DNA controls pattern of growth and development
- Every organism arises through reproduction- Inheritance transmits DNA
from parents to offspring
4) Energy Utilization – take in energy and use it to perform all of life’s activities
The Seven Properties of Life
5) Response to the Environment – all organisms respond to environmental stimuli
6) Reproduction – organisms reproduce their own kind
The Seven Properties of Life
7) Evolution – populations evolve (change) over time
- Evolution is the central, unifying feature of life since life arose nearly 4 billion years
ago
The Seven Properties of Life
Seahorse Camouflage
• Biologists explore life at levels ranging from the biosphere to the molecules that make up cells.
• “Life” emerges at the level of cells
– A cell is the smallest unit that can live and reproduce on its own (perform all properties of life)
– All organisms consist of one or more cells
• Life is more than a sum of its parts, it is an emergent property
Life at Its Many Levels
BiosphereEcosystems
Communities
Populations
BiosphereEcosystems
Communities
Populations
Organisms
Organ Systemsand Organs
Tissues
BiosphereEcosystems
Communities
Populations
Organisms
Organ Systemsand Organs
Tissues
Cells
Organelles
Molecules and AtomsAtom
Nucleus
Ecosystems• Each organism interacts continuously with living
and nonliving factors in its environment.
– The interactions between organisms and their environment take place within an ecosystem.
• The dynamics of any ecosystem depend on two main processes:
– Cycling of nutrients
– One-way flow of energy
Energy and Nutrients• All organisms require energy and nutrients to
sustain their organization and activities
– Nutrients – required for growth and survival
– Producers – make their own food; get energy from sun
– Consumers – obtain energy and nutrients by eating other organisms
– Decomposers – consumers (bacteria, fungi) that recycle complex molecules
Inflowof lightenergy
Chemicalenergyfood
Cyclingof
nutrients
Consumersanimals
Producersplants and otherphotosyntheticorganisms
Decomposersin soil
Loss ofheat
energy
ECOSYSTEM
- Nutrients are cycled
- One-way flow of energy
If So Much Unity, Why So Many Species?
• All organisms
– Made from same materials
– Function on same laws of energy
– Have same properties of life
• Diversity is the hallmark of life
– The diversity of known life includes 1.8 million species.
– Estimates of the total diversity range from 10 million to over 100 million species.
Grouping Species: The Basic Concept
• Biodiversity can be beautiful but overwhelming.
• Species – One kind of organism
• Two part name – Genus species
• Ex. Homo sapiens
The Three Domains of Life• The three domains of
life are:
– Bacteria – single-celled, prokaryotes (no nucleus), most ancient
– Archaea – single-celled, prokaryotes
– Eukarya – eukaryotes (with a nucleus), single- and multi-celled
DO
MA
IN B
AC
TE
RIA
DO
MA
IN A
RC
HA
EA
• Eukarya includes
– Kingdom Plantae
– Kingdom Fungi
DOMAIN EUKARYA
Kingdom Plantae Kingdom Fungi
Kingdom Animalia Protists multiple kingdoms
– Kingdom Animalia
– Protists (single-celled)
Unity in the Diversity of Life• How can organisms be so much alike and still
show tremendous diversity?
• Underlying the diversity of life is a striking unity, especially at the lower levels of structure.
– For example, all life uses the genetic language of DNA.
– Changes in DNA (mutations) which are inherited from parents give rise to diversity
• Biological evolution accounts for this combination of unity and diversity.
EVOLUTION: BIOLOGY’S UNIFYING THEME• Mutations give rise to different forms of traits
• Some trait forms are more adaptive than others
– Those that have them are more likely to survive and reproduce in their environment
• Over generations, adaptive forms of traits tend to become common in a population
– Less adaptive forms of the same traits become less common or lost
Evolution• Evolution is heritable change which occurs in a
line of descent over time
• Populations evolve…not individuals!
– Traits that help characterize a population (and a species) can change over generations
– Each species is one twig of a branching tree of life extending back over 3 billion years.
– Species that are very similar, such as brown bears and polar bears, share a more recent common ancestor.
Ancestralbear
Common ancestor ofpolar bear and brown bear
Giant panda
Spectacled bear
Sloth bear
Sun bear
American black bear
Asiatic black bear
Polar bear
Brown bear
30 25 20 15 10 5
Millions of years ago
Evolution via Selection• Natural Selection
– Natural populations– Differential survival and
reproduction among individuals that vary in one or more heritable traits
• Artificial Selection– Captive populations– Traits selected are not
necessarily adaptive
rock pigeon
Observing Natural Selection
Population with varied inherited traits
Elimination of individuals with certain traits
Observing Natural Selection
Reproduction of survivors
Increasing frequency of traits that enhancesurvival and reproductive success
Reproduction of survivors
Observing Artificial Selection
Domesticated dogs descended from wolves
Domesticated dogs Gray wolves
THE PROCESS OF SCIENCE• The word science is derived from a Latin verb
meaning “to know.”
– Science is a way of looking at the natural world
– Minimize bias in judgments
– Focus on testable ideas about observable aspects of nature
Scope and Limits of Science• Limit science to only that which is observable in
nature
– Allows us to be objective, not subjective
• Science does not address the supernatural or anything beyond nature
How Science Works• The Scientific Method
– Observe something in nature
– Form hypothesis (testable assumption) about it
– Make predictions about what might occur of the hypothesis is not wrong
– Test predictions by observations or experiments
– Repeat for consistency
– Report tests and conclusions
Experiments• Tests used to support or falsify a prediction
– Variable group – characteristic is measured and changed
– Control group – characteristics do not change
• Experiments focus on cause, effect, or function of one variable at a time
– Minimizes bias and controls potential bias in results
Observation:My flashlightdoesn’t work.
Question:What’s wrong
with myflashlight?
Hypothesis:The flashlight’s
batteriesare dead.
Prediction:If I replace thebatteries, theflashlight will
work.
Observation:My flashlightdoesn’t work.
Question:What’s wrong
with myflashlight?
Prediction:If I replace thebatteries, theflashlight will
work.
Experiment:I replace the
batteries withnew ones.
Experimentsupports
hypothesis;make additional
predictionsand test them.
Hypothesis:The flashlight’s
batteriesare dead.
Observation:My flashlightdoesn’t work.
Question:What’s wrong
with myflashlight?
Prediction:If I replace thebatteries, theflashlight will
work.
Experiment:I replace the
batteries withnew ones.
Experimentsupports
hypothesis;make additional
predictionsand test them.
Experiment doesnot support
hypothesis; revisehypothesis orpose new one.
Revise
Hypothesis:The flashlight’s
batteriesare dead.
HypothesisOlestra® causes intestinal cramps.
PredictionPeople who eat potato chips made with Olestra will be morelikely to get intestinal cramps than those who eat potato chipsmade without Olestra.
Experiment Control Group Experimental Group
Percentages are about equal. People who eat potato chipsmade with Olestra are just as likely to get intestinal crampsas those who eat potato chips made without Olestra.These results do not support the hypothesis.
Conclusion
Eats regularpotato chips
Eats Olestrapotato chips
93 of 529 peopleget cramps later(17.6%)
89 of 563 peopleget cramps later(15.8%)
Results
Sampling Error in Experiments• Small sample size increases the likelihood of
sampling error in experiments
• In such cases, a subset may be tested that is not representative of the whole
• Larger sample size and repetition can reduce sampling error
30% green
70% black
Out of 50:
10 (20%) green, 40 (80%) black
Theories in Science• What is a scientific theory, and how is it different from a
hypothesis?
– A theory is a set of well-tested hypotheses that explain some aspect of the natural world
– Explains a broad range of observations (each hypothesis is narrow)
– NOT the absolute truth; can only be relatively certain that it is or is not correct (ex: gravity)
– Opinion and belief are NOT scientific theory
– Science and religion are two very different ways of trying to make sense of nature
Evolution Connection:Evolution in Our Everyday Lives• Antibiotics are drugs that help fight bacterial
infections.
• When an antibiotic is taken, most bacteria are typically killed.
• Those bacteria most naturally resistant to the drug can still survive.
• Those few resistant bacteria can soon multiply and become the norm and not the exception.
• Those few resistant bacteria can soon multiply and become the norm and not the exception.
• The evolution of antibiotic-resistant bacteria is a huge problem in public health.
• Antibiotics are being used more selectively.
• Many farmers are reducing the use of antibiotics in animal feed.