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Chapter 1
Introduction: The Scientific Study of
Life
Biology: The study of life.
Greek origin:
Bio: Life
Logos: Study of
I. Life is based on many structural levels
Levels of biological organization:
 Atoms
 Molecules
 Subcellular
organelles
 Cells
 Tissues*
 Organs*
 Organ
systems*
 Organism: May consist of a single cell or a
complex multicellular organism.
* Level of organization not found in all organisms
Levels of organization beyond organism:
 Population:
Group of organisms of the same species
that interact with one another.
 Community:
Several different populations living
together in same area (e.g.: lake, forest, jungle).
 Ecosystem: Interactions of community with non-living
environment (air, water, soil).
 Ecosphere:
•
•
•
•
All ecosystems on planet earth. Includes:
Biosphere: All biological communities on earth.
Atmosphere (air)
Hydrosphere (water)
Lithosphere (crust)
Common features of all organisms:
1. Cells: Basic structural and functional unit of
life. Genetic information contained in DNA.
2. Growth and Development:
 Growth:
Occurs by an increase in cell size, cell
number, or both.
 Development: Changes that take place during an
organism’s life.
3. Energy use and metabolism:
 All
organisms must take in and transform energy to
do work, to live.
 Metabolism: All chemical reactions and energy
transformations essential for growth, maintenance,
and reproduction.
4. Regulation
 External
environment may change, but internal
environment remains fairly constant.
• Homeostasis: Organisms constantly strive to maintain a
“steady state” (e.g.: constant body temperature or blood pH)
despite changes in the internal and external environment.
• Metabolism is regulated by homeostatic mechanisms.
5. Movement:
 Internal
movement: Characteristic of all life.
 Locomotion: Self-propelled movement from point A to
point B. Not observed in all life forms.
6. Respond to environmental stimuli: Organisms
respond to internal and external changes (visual
stimuli, temperature, light, sound, pressure, etc.).
7. Order: Organisms are highly organized,
when compared to nonliving environment.
8. Reproduction: Organisms come from other
organisms. Reproduction may be sexual or
asexual.
9. Evolutionary adaptation: Populations, not
individuals, “evolve” or change over many
generations so they can survive in a changing
world.
The cell is the basic unit of life
 Lowest
level of structure capable of
performing all of life’s activities
 All
organisms are composed of cells
 VIRUSES:
Not considered living organisms by
most biologists because they lack:
• Cells
• Self-regulated metabolism
 May
exist as unicellular or multicellular
organism
Comparison of Cells and Viruses
Evolution Explains the Unity and Diversity of Life
Charles Darwin (1809-1882)
Evolution is the core theme of biology
Darwin: Wrote “On the Origin of
Species by Means of Natural Selection” (1859)
in which he proposed the theory of evolution.
 Charles
Evidence that led to the principle of evolution:
 Fossils:
Most species that ever existed are
extinct; appear to be gradual progression
 Artificial selection of domestic/farm animals
 Adaptations:
Organisms appear uniquely
suited to their environment (especially in
Galapagos).
 Darwin’s
finches are a classic example
The theory of evolution by natural selection:
1. Genetic Variation: Due to genetic differences
there is variation within a population (size, color,
structure, etc.). These differences can be passed
on to an individual’s offspring.
2. Overproduction: Many more organisms are
born, than those that survive and reproduce.
3. Limits on population Growth: Limited
resources (food, water, space, sunlight, etc.)
creates competition
4. Differential reproduction: Organisms with
features that help them compete will be more
likely to survive and reproduce.
Natural Selection Changes Populations
Theory of evolution by natural selection:
Consequences of natural selection
Over time, the characteristics of a population
will “evolve” and assume those features
that are “naturally selected”.
What is the heritable molecule with the
blueprints for the traits of an organism?
DNA:
Deoxyribose nucleic acid
All life can be classified taxonomically
 Taxonomy:
The branch of biology concerned
with naming and classifying organisms
 Most
Biologists Recognize Five Kingdoms:
Monera, Protista, Plantae, Fungi, and Animalia
 However,
biologists have recently discussed a
new classification system:
 Domain
Bacteria
 Domain Archaea
 Domain Eukarya
 All
life can be classified taxonomically
 1.
Kingdom Monera (Procaryotae): Most
widespread organisms.
 Procaryotes
(“Before nucleus”):
• Lack nuclear membrane around DNA.
• Lack membrane bound organelles (mitochondria,
chloroplast, golgi, endoplasmic reticulum).
 Unicellular:
Single celled organisms.
 Have a cell wall.
 Include:
Bacteria.
Kingdom Prokaryotae: Bacteria lack
nucleus and membrane bound organelles
Five Kingdoms of Living World:
2. Kingdom Protista:
 Eucaryotes
(True nucleus):
• Have nuclear membrane around DNA.
• Have membrane bound organelles (mitochondria,
chloroplast, golgi, endoplasmic reticulum).
 Unicellular
or simple multicellular.
 Most
are larger and more complex than bacteria.
 Some
have cell walls, others don’t.
 Some
make their own food (phothosynthetic),
others must eat other organisms.
 Include:
Protozoa, algae, slime molds.
Kingdom Protista: Eucaryotic Unicellular or
Simple Multicellular Organisms
Five Kingdoms (Continued):
3. Kingdom Fungi:
 Most
are multicellular.
 Eucaryotes:
• Have nuclear membrane around DNA.
• Have membrane bound organelles (mitochondria,
chloroplast, golgi, endoplasmic reticulum).
 Have
cell walls.
 Heterotrophs:
Obtain food from other organisms.
 Most
are decomposers, which absorb food from
dead organisms.
 Include:
Mushrooms, yeasts, and molds.
Five Kingdoms (Continued):
4. Kingdom Plantae:
 Complex
multicellular organisms.
 Cellulose
cell walls.
 Eucaryotes:
Have nuclear membrane around DNA
and membrane bound organelles.
 Autotrophs:
Convert sunlight, water, and carbon
dioxide into food through photosynthesis.
 Other
features:
• Waxy cuticle that prevents water loss.
• Multicellular sex organs.
• Openings in leaves and stems for gas exchange (stomata).
 Include:
Trees, flowering plants, and mosses.
Five Kingdoms (Continued):
5. Kingdom Animalia:
 Complex
 Lack
multicellular organisms.
cell walls.
 Eucaryotes:
Have nuclear membrane around DNA
and membrane bound organelles.
 Heterotrophs:
Obtain chemical energy from living
sources. Eat other organisms for nourishment.
 Features
of complex animals:
• High degree of tissue specialization and body
organization.
• Locomotion.
• Well developed sense organs, nervous system, and
muscles.
 Include:
Sponges, worms, insects, and vertebrates.
Interdependence of Biological Groups
1. Producers or Autotrophs:
Self-nourishing organisms (plants, algae, etc.).
 Produce food from simple raw materials.
 Most carry out photosynthesis:
CO2 + H2O + Sunlight -----> Food + Oxygen
 Depend on nonproducers for carbon dioxide

2. Consumers
 Mainly
animals.
 Heterotrophs that obtain food directly or indirectly
from producers.
 Carry out cellular respiration:
Food + Oxygen -----> CO2 + H2O + ENERGY
Gas exchange between producers and consumers helps
maintain balance of life-sustaining gases in atmosphere.
Interdependence of Biological Systems
3. Decomposers:
 Some
bacteria, fungi, and animals.
 Recycle nutrients by breaking down products and
bodies of dead organisms.
 Process is vital because makes nutrients available
for use by other organisms.
All organisms interact with each other and
the environment they live in.
 Interactions between producers,
consumers, and decomposers are essential
to maintain proper conditions for life on
earth.

Relationships Between Producers,
Consumers, and Decomposers
Nutrient Cycling and Energy Flow in
an Ecosystem
SCIENCE AS A METHOD OF INVESTIGATION
Scientia (Latin): To know
Science is a systematic way of thinking, answering
questions, and solving problems.
Steps of scientific method:
1. Observations
2. Question
3. Hypothesis
4. Predictions
5. Test predictions (Experiments)
Results of experiments may:


Support (but not prove) hypothesis
Disprove hypothesis -----> Change hypothesis.
Scientific method (Continued):
Hypothesis:




Proposed explanation for observations
An “educated guess”, should be consistent with established facts
Capable of being tested, should generate predictions.
Falsifiable, may be proven false (but not proven true).
Variables in an Experiment



Dependent Variable: What a scientist measures.
Independent variable: What a scientist controls or manipulates.
Standardized variables: What remains the same throughout
experiment. E.g.: Age, sex, race, nutrition, health, etc.
Control Treatment:

Independent variable is eliminated or set at a standard value.
Levels of Treatment

Values set for the independent variable.
Scientific method:
Replication



Experiments are repeated numerous times.
Consistent results increases confidence in results.
Sample size: Larger sample sizes are generally better.
Theory:


Hypothesis supported by a large body of observations and
experiments.
Good theories relate previously unrelated facts and grow as new
information is obtained.
Principle:


A theory that over time has yielded true predictions.
Almost universally accepted.
Law:


A principle of great basic importance.
Law of gravity or biogenesis.
Biology is connected to our lives in many
ways
 Birth,
development, reproduction, aging, and
death
 Disease and infections
 Human population
 Nutrition & exercise
 Agriculture
 Biodiversity and endangered species
 Genetic engineering and reproductive technology
 Pollution and environment