• We have learned that evolution is the process
of DNA mutations creating new species over
• What determines if different organisms are
different species? What is a species?
A species consists of all individuals that can
breed together and produce fertile offspring.
This definition is called the Biological Species
A female donkey mated to a male horse
A mule (which is sterile)
Hence, donkeys and horses
are separate species.
Criticisms of the Biological Species Concept
• Cannot be used with asexual organisms
• Cannot tell if fossil specimens were capable of
• Doesn’t account for isolation:
– Behavioral isolation: having different
courtship rituals or behaviors
– Geographic isolation: separated by
– Temporal isolation: reproduce at different
How are different species named?
• Taxonomy- The science of naming and classifying
• A Swedish biologist named Carolus Linnaus came
up with a two-word system for naming organisms.
It is called binomial nomenclature.
• There are 7 levels of classification:
• In binomial nomenclature, the first word is the
organism’s genus name and the second word is
the species name.
Species: Sapien (means “wise”)
• Using binomial nomenclature, we are
Homo sapiens. Always capitalize the genus
and italicize or underline both the genus
and species names.
The levels get more
specific as you work
down to the species.
Have all living things been
• NO! Our knowledge of all living things is
• Classification is based on anatomy,
embryology, DNA, behavior, and when the
• If you are unsure of the binomial nomenclature
of an organism, you can use an identification
system called a dichotomous key.
Example of a Dichotomous Key
Interdependence of Life
• Ecology- The study of relationships
between living things and their environment.
• Biosphere- The area around the earth
where life exists.
– includes the hydrosphere, lithosphere, and
Levels of the Biosphere
• Biome- a large area characterized by certain
animal and plant species as well as climate
• Ecosystem- All of the living and non-living
components of a particular geographic area.
• Community- A naturally occurring group of
plants and animals living in a particular area.
• Population- A group of organisms of one
type (species) living in a particular area.
• Habitat- The physical area in which an
• Climate- The prevailing weather conditions
of a geographic area.
Levels of a Biosphere
(Habitat and Climate)
Components of an Ecosystem
• Abiotic- Non-living
• Biotic – Living
Trophic Levels of Ecosystems
A trophic level is a
– The relationship
between what an
organism eats and
what eats it.
– Where it fits into a
– The 1st Trophic Level
is at the bottom of
the food chain.
How Biotic Factors Obtain Energy
• Organisms that can make their own food =
organic (carbon containing) materials
• At the 1st Trophic Level
• Examples: plants and bacteria
• Photosynthetic- Use energy from sunlight
and convert it into organic energy
• Chemosynthetic- Use energy from
inorganic compounds and covert it into
Organisms that cannot make their own food
and must get it from an external source.
• Primary (1st) consumer- herbivore- eats only
• Secondary (2nd) consumer- carnivore- eats
• Tertiary (3rd), quaternary (4th), etc.
• Omnivore- eats producers and consumers
• Detritivore- breaks down wastes and dead
• Decomposer- fungi, bacteria: return nutrients
to the soil for absorption
• Food Chain: Specific feeding sequence in
which organisms obtain energy in an
Grass Caterpillar Sparrow Snake Coyote
Arrows always point in the direction of energy flow!
• Food Web: Interrelated food chains
FOOD WEB :
• What is/are the producer(s)?
• What is a herbivore?
• What is a primary consumer?
• What is a secondary consumer?
• What is a tertiary consumer?
• What would be 3 consequences in the fish population died out?
How do we keep track of energy in
• Ecological Pyramids- A diagram that shows the
amounts of energy at each trophic level in a food chain
or food web. (3 types)
1. Numbers Pyramid: counts the # of individuals
(does not discriminate by size) – can be an
inaccurate indicator of energy at that level
– Ex. Caterpillars outnumber the trees that they feed on
2. Biomass Pyramid: measures amount of living
tissue (dry weight) in grams
3. Energy Pyramid: measures amount of energy
stored in tissues (ex. fats = 9 Cal/gram;
carbohydrates/proteins = 4 Cal/gram)
• Amount of energy available to do work
decreases as energy passes through a
• 10% transfer of energy (90% energy lost)
from one level to the next. Most is lost to the
air as heat.
• How much energy would be transferred to
each level of the following food chain?
GrassCaterpillarSparrow Snake Coyote
• Studying changes in population size is
called population ecology.
• This helps scientists predict future changes
in populations and better understand how to
• Counting members of a population is often
impossible. Estimation of population size
can calculated using the Capture-Recapture
• In the Capture-Recapture Method, a sample
of animals are caught and tagged. They are
then released back into their habitat. Other
samples are then captured at various times
and each time the total number and marked
number of animals are noted.
• The following equation is then used to
estimate population size.
N= # originally marked x total # animals captured
# of animals marked that were captured
20 fish were captured, marked and put back into
a pond. On 10 different occasions, samples
were taken from the pond. What is the
estimated population size?
# obtained in the sample
# marked in the sample
How do populations grow?
• Most populations grow either exponentially
• Exponential growth occurs when
resources are plentiful and the
reproduction rate is greater than the death
• On a graph, exponential growth looks like
How do populations grow?
• Logistic growth occurs if there are limited
resources and growth of the population
begins to slow as competition for those
resources increases. The growth of the
population eventually slows to nearly zero
as the population reaches the carrying
capacity for the environment.
• On a graph, logistic growth looks like a