Scientific Method
For centuries, people based their beliefs on their
interpretations of what they saw going on in
the world around them without testing their ideas
using the scientific method.
Their conclusions were based on untested observations.
Scientific Method
Since the time of Aristotle (4th Century BC), people
believed that simple
organisms could come
into being by spontaneous
generation. This was the idea
that non-living objects can
give rise to living organisms.
Spontaneous Generation
Observation: Every year in the spring, the Nile River
flooded areas of Egypt along the river, leaving behind
nutrient-rich mud that enabled the people to grow
that year’s crop of food. Along with
the muddy soil, large numbers of frogs
Appeared that had not been there in drier times.
“Conclusion”: It was obvious that
muddy soil gave rise to the frogs.
Spontaneous Generation
Observation: In many parts of Europe, medieval
farmers stored grain in barns with thatched roofs.
As a roof aged, it was not uncommon for it
to leak. This could lead to spoiled or moldy
grain, and lots of mice.
“Conclusion”: It was obvious that the
mice came from the moldy grain.
Spontaneous Generation
From this came a number of interesting recipes, such as:
Recipe for bees: Kill a young bull, and bury it in an
upright position so that its horns protrude from the
ground. After a month, a swarm of bees will fly out
of the corpse.
Recipe for mice:
Place a dirty shirt or some rags in an open
pot containing a few grains of wheat,
and in 21 days adult mice will appear.
Scientific Method
Scientific Method
We guess what the answer to the problem might be:
this is called the hypothesis
Scientific Method
We execute an experiment to test the validity of the
hypothesis.
Experiments must include a control and be able to be
replicated
Scientific Method
Results
Scientific Method
Replication
Scientific Method
Components of Experiment
Scientific Method
Cyclical nature of the scientific method
Levels of organization
Atoms
Water
molecule
Levels of organization
Cell
Levels of organization
Tissue
Levels of organization
Organ
Organ System
Levels of organization
Organism
Population
Levels of organization
Community
Ecosystem
Levels of organization
Biosphere
Ecology: The study of how all species in an area
interact with each other and the environment
Organism
Ecosystem
Population
Biosphere
Community
Symbiosis
Mutualism
Commensalism
Competition
Predation and Parasitism
Energy flows through
Ecosystems
Recall the laws of Thermodynamics.
#1 Energy is never gained or lost, only
transformed.
#2 Energy flows spontaneously in one
directions, from ordered to less ordered.
Heat is the ultimate destination of all
energy.
Energy in an ecosystem starts with the
sun and flows through a given ecosystem.
Model of an ecosystem showing the one-way flow of
energy and the cycling of nutrients between autotrophic
and heterotrophic organisms. Most of the energy
originally fixed by the autotrophs is lost to the
environment as metabolic heat.
Food chain and trophic lines
Simple Food Chains
Food web
Diatoms and dinoflagellates are single-celled
photosynthetic organisms. They are part of the marine
phytoplankton, which is the basis of most marine food
webs. The phytoplankton synthesize at least 35 percent
of all food made by photosynthesis.
Pyramid of biomass and energy flow
STOP
Exponential or J-shaped growth
curve
Bacteria can grow exponentially
Logistic or S-shaped growth curve
Carrying
capacity
“K”
Equilibrium
Real World Population Curve
Birth Rate – Death Rate
Birth Rate

Number of individuals born in a given time period
(expressed as a proportion of the whole)
Population is 1000
Number of births = 100
Birth rate is 10% or 0.10
Death Rate

Number of individuals that die in a given time
Population is 1000
Number of deaths = 80
Death rate is 8% or 0.08
r or intrinsic rate of increase
Birth – death = r

Intrinsic rate of increase
Can use this number to predict what will
happen to the population in the future.

If r = 2
If r = 6
1000, 1020, 1420
1000, 1060, 3200

If r < 0
population is in decline

A Population’s Potential for
Growth
Carrying Capacity or K
The maximum population density of a
given species that a given geographic
area can sustain over time.
Environmental Resistance begins to assert
itself.
K can be used to predict change in a
population’s size (mathematic formula).
Exceeding the Carrying Capacity
Reproductive Strategies
Characteristics that have the effect of
increasing the number of fertile offspring
that an organism bears.

K - selected species (large species)
limited by carrying capacity
pressures are density dependent
biological forces

r – selected species (small species)
limited by their reproductive rate
pressures are density independent
physical forces (rain, temperature, etc.)
Not a perfect theory, there are exceptions.
These affect K-selected
species most
These affect r-selected
species most
Survivorship Curves
late loss, constant loss, early loss
Also referred to as Type I, Type II, Type III
Human Population Survivorship
Curves
Originally developed by British actuaries
for life-insurance companies
Also called population pyramids
Population growth in a sampling of different countries
Rate of human growth, estimated
to be 9 billion by 2050.
Age structure diagrams for the United States population.
Gold bars track the baby boomer generation.
Exponential growth of the human population
Today it appears to be stabilizing.
Human Population and the
Environment
Humans are the greatest threat to the
environment.
The use of natural resources (per person)
Amount of waste pumped into the
environment
Reduction of the species habitat
Decimation of species through hunting and
fishing
Communities
Where populations interact
Biodiversity, variety among living things
3 types



Variety in a given area or species diversity
Variety in populations around the globe or
geographic diversity
Variety within the genetics of a population or
genetic diversity
Effects of Diversity
More productive community

A measure of how much of the sun’s energy
is used by plants to make living material or
biomass
A more stable community

Species diversity leads to more stable
communities
Habitat – the physical surroundings in
which a species can be found
(neighborhood)
Niche – a characterization of an
organism’s way of making a living (habitat,
food, behavior)
Interspecific competition – competition
between two or more species

Usually indirect, a competition for resources
Competitive Exclusion Principle – when
two or more species compete for
resources, one will outcompete and
extinction will follow.
Competitive exclusion in Paramecium species
Grown separately
Grown together
Resource Partitioning
Resource partitioning among root systems of weeds.
Dividing up scarce resources among species that have
similar requirements.
Predation
Predator – Prey Dynamics
Social parasite: Cuckoo bird
Mimicry
The ability to fool opponent, one species
evolves to assume the appearance of
another
A mimic, a model and a dupe
Batesian mimicry – the evolution of one
species to resemble a species with a
superior protective capability.
Müllerian mimicry – several species with
protection against predators come to
resemble each other.
Example of a model and its mimics
Fly
Beetle
Stingless wasp
Batesian mimics
Yellow jacket
model
Two South
American butterflies
are different in some
ways but both taste
bad to predators.
Over time, they
evolved to look
alike.
Covevolution
Interdependent evolution of two or more
species.

Flowers and bees
Fragrance to attract
UV color patterns to guide

The bee’s color vision evolved in response to
the plant coloration.
Camouflage
When approached by a predator, the bittern thrusts its
beak in the air and sways like the reeds that surround it.
Examples of camouflage
Prey
Predators
Lithops,
hiding from
herbivores
Warning Coloration
Succession
In ecology, a series of replacements of
community members at a given location
until a stable final state is reached.


Primary succession – succession in which the
starting state is one of little or no life and a
soil that lacks nutrients
Secondary succession – the final state of a
habitat has been disturbed by some force, but
life remains and the soil has nutrients.
Common Elements
Lichens and photosynthetic bacteria are
pioneer species
A steady increase in Biomass
General movement towards longer-lived
species
Trend towards species diversity
Facilitation of the growth of some later
species through the actions of earlier
species
Competition drives out other species
Primary succession
Glacial retreat
Volcanic island
Land surfaces consisting of rock, lava, volcanic ash,
sand, clay, or some other exclusively mineral substrate.
The soil lacks nutrients
Primary succession
Secondary succession
fire
abandoned farmland
Secondary succession is caused by fire, flood,
windstorm, abandoned cropland.
Secondary succession
Biochemical Cycling
Water and nutrients move back and forth
between biotic and abiotic realms.
Carbon, nitrogen, sulfur, phosphate, water
all have complex biochemical cycles.
All the elements we will ever possess are
on the earth now. The question is, where
are they?
Carbon Cycle
Carbon is used by all living organisms.
The most carbon is stored in the tissues of
living organisms.
Only 0.035% of the atmosphere is CO2
Carbon reservoirs
Carbon Cycle
The level of carbon dioxide in the earth's atmosphere is
increasing as a result of the burning of fossil fuels and
the removal of vegetation that could use it for
photosynthesis.
Reconstruction of a Carboniferous forest. Fossil fuels,
including coal, petroleum (oil), and natural gas, are the
remains of plants that lived millions of years ago. It
took millions of years to convert such vegetation to
usable fuels.
Nitrogen Cycle
Nitrogen is used by living organisms to
make protein and nucleic acids (RNA and
DNA)
Most of the Nitrogen is found in our
atmosphere (80% of the atmosphere is
Nitrogen)
Plants cannot directly access the
atmospheric nitrogen. Bacteria fixes
atmospheric nitrogen and makes it
available to plants.
Nitrogen Cycle
Legumes such as peas, soybeans, and clover interact
with mutualistic, nitrogen-fixing bacteria. The bacteria
enter the root and take up residence in root nodules.
These soybean plants are growing in nitrogen-poor
soil. The plants on the right were inoculated with
Rhizobium, one type of nitrogen-fixing bacterium.
Notice that they are much larger and greener than the
uninoculated plants on the left.
Phosphorus Cycle
Found in ATP and DNA
Does not have atmospheric reservoir
Always attached to oxygen
Phosphorus Cycle
Cycling of Water
Water is stored in ice and in the oceans
(95%).
The ocean water evaporates and falls
back to earth as rain.
Water is also cycled through transpiration.
1 billion people lack access to sanitary
water.
70% of the groundwater we withdraw goes
to agricultural irrigation, a very inefficient
process.
Hydrologic cycle
Hydrologic cycle
Human Impact on Resources
a. Nearly a quarter of the current atmospheric carbon dioxide concentration is produced
by human activity, primarily through the burning of fossil fuels
b. Over half of terrestrial nitrogen fixation comes about because of some human activity,
including the manufacture of fertilizer for agriculture.
c. Over half of the Earth’s accessible surface water is now diverted for use by humans,
mostly for agriculture.
Composition of Earth’s atmosphere
Malignant melanoma, a type of skin cancer that can be
fatal. Exposure to ultraviolet light is the major risk
factor for the development of such cancers. Unless
CFCs (ozone-depleting chemicals) are reduced, the
rates of such cancers will rise.
Nonrenewable energy sources
Nuclear
Coal, oil, natural gas
Renewable energy sources
Solar
Hydrogen
Geothermal
Wind
Biodegradable
Capable of being broken down in nature
Recyclable
Possible to use again; can be reprocessed to
form a new product
Biomes
Biomes
Tundra
Biomes
Deciduous forest
Taiga or Coniferous
Forest
Biomes
Grasslands biome
Biomes
Kansas prairie
African savannah
Organisms in similar biomes, even on different continents
are strikingly similar
Chaparral
Biomes
Desert biome
Tropical rainforest
Ocean zones
Coral Reefs
Temperate Nearshore
Ecosystems
Estuary
Intertidal Zone
Lake zonation
photic zone
An oligotrophic lake. Such newly formed lakes are
nutrient-poor, with low primary productivity. They tend
to be deep, with steep banks and crystal-clear water.
photic
zone
A eutrophic lake. Such lakes are nutrient-rich, with high
primary productivity. They tend to be shallow, and the
water tends to be of limited transparency. In warm
summer months, the bottom of a eutrophic lake may
become depleted of dissolved oxygen
Wetlands