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Unit 7 Notes
Teacher's note: Unit 7 was rewritten this school year. Not all of the vocabulary words in the student unit
outline are included on the exam. Be sure to study the underlined words in these notes. They are the
vocabulary words that may appear on your exam!
Topic 1: Principles of Ecology
Ecology is the study of relationships among living organisms and the interaction that the organisms have
with their environments.
The focus of ecologists is in the biosphere - the portion of the earth that supports life. It is a thin layer at
and below the earth's surface.
Consider the shared environments of various living organisms.
A biotic factor is any other living organism in an environment. For example, the biotic factors in a tree
frog's environment include:
 insects and other bugs
 trees and plants providing habitat
 microscopic organisms living on plants in the habitat
 other animals that prey on frogs
An abiotic factor is any nonliving factor in an organism's environment. Examples include:
 temperature
 air or water currents
 sunlight
 soil type
 rainfall
 available nutrients
If an organism is moved to a new environment with differing abiotic factors than the natural environment,
the organism may not adapt quickly enough to survive.
We often refer to living things in terms of how large the population of organisms is. There are different
levels of organization involved. The following levels of organization are listed from smallest to largest as
you go from left to right:
Organism → Population → Biological Community → Ecosystem → Biome → Biosphere
**small**
**large**
A habitat is the area where an organism lives.
A niche is the role or position that an organism has in its environment. How does the organism meet needs
for food, shelter, and reproduction?
Community interactions must be studied in order to understand the biological community. We will look at
three types of community interactions:
1. Competition occurs when multiple organisms use a resource at the same time.
2. Predation is when an organism consumes another organism.
3. Symbiotic relationships occur when survivability of an organism relies on living in a close
relationship with another or multiple organisms (symbiosis).
a. Mutualism (+,+) is when both organisms benefit from each other.
o An example is that lichens are created from algae and fungi living in mutualism. Algae
provide food for the fungi; fungi provide habitat (shelter) for the algae.
b. Commensalism (+,0) is when one organism benefits and the other organism is neither helped nor
harmed.
o An examples is lichens and trees. Lichens receive more sunlight from being on the tree
and the tree is not harmed or benefited.
o Another example is clownfish and sea anemones. Clownfish receive protection and the
anemones are neither harmed nor helped.
o Another example is humans and eye mites. Humans provide a home and the mites
neither harm nor benefit the human.
c. Parasitism (+,-) is when one organism benefits at the expense of another organism. The parasites
can be external or internal.
o An example is heartworms and dogs. The heartworms thrive in the heart of the dog while
weakening or harming the dog's heart tissue.
o Another example is mosquitoes and humans. The mosquito takes blood (food) from the
human and can leave a virus in the human that could cause harm.
The flow of energy in an ecosystem is important. There are different ways to obtain energy.
An autotroph produces its own food.
A heterotroph meets its energy requirements by consuming other organisms.
 Herbivores eats only plants, e.g., cows, rabbits, grasshoppers
 Carnivores prey on (eat) other heterotrophs, e.g., wolves, lions, lynxes
 Omnivores eat both plants and animals, e.g., bears, humans, hummingbirds
 Detritivores eat fragments of dead items, e.g., worms, many aquatic insects
Scientists model the flow of energy in living organisms in different ways. We will study three of these
methods. In each method, each step of the energy flow model represents a trophic level. The first level is
always an autotroph. Organisms at each trophic level get their energy from the previous trophic level. The
three different models we will study are listed below.
1. Food chains are simple flow models that shows energy flowing through a line of organisms in an
ecosystem. **See diagram of food chain from class**
2. Food webs are models representing the many interconnected food chains and pathways in which
energy flows through a group of organisms. ** See diagram of food web in class**
3. Energy pyramids are a triangular representation of trophic levels in an ecosystem, with autotrophs
at the bottom level of the triangle and the top consumer at the peak of the triangle. Only about
10% of the energy from one trophic level is passed to the trophic level above it - the other 90% is
lost, mostly through cellular respiration, then heat loss. There are also pyramid models that show
biomass or population instead of energy.
We will be studying four biochemical cycles in class. Biochemical cycles show the exchange of matter
throughout the biosphere. The cycles studied in class are for water, carbon and oxygen, nitrogen, and
phosphorus. See diagrams below. (Except for phosphorus - I don't have a copy of that diagram and
therefore it won't appear on the test!)
Topic 2: Organizing Life's Diversity
Why organize or group items? To make it easier to locate, understand, or discuss living organisms.
We will study two systems of classification.
1. Aristotle (a Greek scientist and philosopher) divided all living organisms into the categories of plants or
animals.
 Plant classification was based on the size and structure of the plants. ex.: trees, shrubs, herbs
 Animal classification was divided into bloodless or red-blooded animals (this is similar to our
current invertebrate and vertebrate classifications), then further grouped the animals according to
habitats and morphology.
2. Carolus Linnaeus came up with a structured taxonomy of living organisms. Taxonomy is a discipline of
biology primarily concerned with identifying, naming, and classifying organisms based on morphology and
natural relationships. He established binomial nomenclature.
Binomial nomenclature is a scientific name with two parts which uses the Latin language (because is
unchanging). It is broken into the genus and species for the organism. For example, we are Homo sapiens!
Dichotomous keys are tools used to classify organisms. There are two main kinds of dichotomous keys:
tree and line. A tree structure lets you follow the classification scheme like a flow chart. The line structure
is a series of yes or no questions which eventually lead you to the correct classification for the organism.
The current taxonomy used by scientists classifies living organisms into seven different levels. Each level
is called a taxon. The chart below provides the classification of six organisms according to this system.
Animal
Kingdom Phylum
Class
Order
Family
Genus
Species
Common Name
Human
Animalia Chordata Mammalia
Primates
Hominidae
Homo
sapiens
North American
Black Bear
Animalia Chordata Mammalia
Carnivora
Ursidae
Ursus
americanus
Striped Skunk
Animalia Chordata Mammalia
Carnivora
Mephitidae
Mephitis
mephitis
Earthworm
Animalia Annelida Oligochaeta
Terricolae
Lumbricidae Lumbricus
Freshwater
Ribbon Leech
Animalia Annelida Hirudinea Arhynchobdellida Erpobdellidae Nephelopsis obscura
Southeastern
Pygmy
Rattlesnake
Animalia Chordata Reptilia
Squamata
Viperidae
Sistrurus
terrestis
miliarius
The highest level of classification (taxon, plural is taxa) is kingdom and contains the most members.
Species is the lowest taxon and has the least members.
Notice that the last two taxa are genus and species, which are used in binomial classification and are
italicized. The species name is not capitalized, but the genus and all higher taxa are capitalized.
Know the five kingdoms and their characteristics!
Topic 3: Population Ecology
Studying the characteristics of a population allows us to learn more about the organisms we are examining.
We will be studying four population characteristics.
Population density is the number of organisms per unit area.
Spatial distribution is the pattern of spacing of a population within an area. Three examples of spatial
distribution and examples for humans are:
 Uniform distribution, e.g., apartment living
 Clumped distribution, e.g., subdivision living
 Random distribution, e.g., rural living
Population range is the area the population uses as a habitat.
Growth rate is the rate of offspring production.
Be sure to know about population estimation using quadrats! (Like in our activity.)
There are factors which limit the population of an organism. We will study two factors.
A density-independent factor is any factor that does not depend on the number of members in a population
per unit area. Some of these factors are natural, abiotic factors such as drought or flooding, extreme heat or
cold, fires, tornadoes, and typhoons. Some of the factors are due to human interference such as air, land, or
water pollution, and alterations to the landscape such as dams on rivers.
A density-dependent factor is any factor in the environment that depends on the number of members in a
population per unit area. Some examples of density-dependent factors are:
 Predator density - Wolves and moose population - see p. 96 in the book for details
 Disease - When high population density occurs, the transmission of disease becomes easier and
quicker, thus more prevalent.


Competition - Populations may increase to a point that resources will diminish and competition for
the remaining resources occurs. If competition is not necessary due to an abundance of resources,
a population may increase in size.
Parasites - Parasites can decrease populations similarly to disease when populations are at high
densities.
The population growth rate can be calculated if certain factors are known:
 Natality (N) is the birth rate
 Mortality (M) is the death rate
 Immigration (I) is the number of individuals moving into a population
 Emigration (E) is the number of individuals moving away from a population
Population Growth Rate = (N + I) - (M + E)
Two growth models can be used to graph the rise in population of a community. See notes from class for
the graphs.
The exponential growth model has a J-shape (due to growth without any hindrance), a lag phase followed
by exponential growth, and is not very realistic.
The logistic growth model has an S-shape (due to population growing exponentially until reaching the
carrying capacity), a lag phase followed by exponential growth, then a leveling off due to reaching the
carrying capacity.
The carrying capacity is the maximum number of individuals in a species that an environment can support
for the long term.
Topic 4: Evolution
Charles Darwin sailed around the world on the H.M.S. Beagle in 1831. It was a five-year voyage on which
Darwin was hired as a naturalist. He collected many biological and geological samples (plants, animals,
rocks, and fossils) on his trip.
The most important stop on his trip was in the Galapagos Islands. Darwin collected mockingbirds, finches,
and other animals. He introduced species to John Gould who noted the new species as different from
European and South American species. Darwin's suspicion was that the species changed when leaving the
mainland because the environment is different on the islands.
Consistent environmental differences in habitats on different islands in the Galapagos, as well as the
availability of different food sources, have produced more than a dozen distinct species of finches, all
unique to the archipelago.
Darwin continued his study and hypothesized that new species would appear gradually through small
changes in ancestral species. Gradual changes such as these are now considered to occur in one of two
methods.
In natural selection, some competitors in the struggle for existence would be better equipped for survival
than others, while those less equipped would die.
In artificial selection (a.k.a selective breeding), the process of direct breeding is used to produce offspring
with desired traits.
Charles Darwin came up with four basic principles to his Theory of Evolution by Natural Selection. These
principles are:
1. Individuals in a population show differences/variations.
2. Variations can be inherited (passed down from parent to offspring).
3. Organisms have more offspring than can survive on available resources.
4. Variations that increase reproductive success will have a greater chance of being passed on than
those that do not increase reproductive success.
Darwin wrote a book about his ideas titled "On the Origin of Species by Means of Natural Selection." The
book explains how natural selection may provide a mechanism for the origin of species. It provided a
solution to how evolution may happen. It also provided evidence that evolution occurred on our planet.
Evolution is the cumulative change in a group of organisms through time. Natural selection is NOT
evolution. It is the mechanism for evolution to occur.
There are six different types of support for evolution:
1. The fossil record shows ancient species that can be compared with current species. The fossil record
is important for ancestral and evolutionary classification.
2. Two major classes of traits are seen in fossils.

Derived traits are newly evolved features that do not appear in the fossils of common ancestors.

Ancestral traits are more primitive features that do appear in ancestral forms.
3. Comparative anatomy is another type of evidence in support of evolution. Three types of structures
are often compared:

Homologous structures are anatomically similar structures inherited from a common ancestor, e.g.,
the similar structure of limbs in land and sea mammals.

Vestigial structures are reduced forms of functional structures in other organisms, e.g., human
appendix, kiwi wings, snake femur.

Analogous structures serve the same purpose in different species yet the species are not closely
related to each other. The structures did not come from a common ancestor. E.g., both beetles and
eagles have wings, but they do not share a common ancestor that had wings.
4. Comparative embryology is another type of evidence for evolution. The embryos of many animals
appear very similar, containing a tail, head, and pharyngeal pouches. In birds, reptiles, and mammals, the
pouches become ears, jaws, and throats. In fish, the pouches develop into gills. This would suggest that all
these animals (vertebrates) shared a common ancestor.
5. Comparative biochemistry is another support for evolution.

Certain amino acids are common in closely related organisms, but are not common in more
distantly related organisms.

DNA and RNA form the molecular basis of heredity in all living organisms. This implies that all
living organisms are all related.
6. Geographic distribution is another piece of evidence to support evolution. The distribution of related
organisms can allow scientists to trace the path of evolution through a region geographically.
Adaptations allow some organisms to survive a change to their environment.
Fitness is the measure of the relative contribution an individual trait makes to the next generation.
Three types of adaptation you should know are camouflage, mimicry, and antimicrobial resistance.
 Camouflage is a morphological adaption that allows an organism to blend in with their
environment.
 Mimicry is when one species evolves to resemble another species.

Antimicrobial resistance is when microbes (bacteria and viruses) become resistant to the drugs
used to treat infections. The drugs become less and less effective with each new generation of
microbe. They become resistant because the microbes that are not resistant die off and the
resistant microbe increase their percent of the total population.