Unit 2 - Ecological Organizations - part 1
Unit 2 - Ecological Organizations - part 1
Important introductory terminology (Levels of Organization):
An individual living thing, ex: frog, humans
Member of a particular biological population
a group of the same species (individuals) that live together in one area at a
certain time, ex: number of gophers in Balgonie area, in 2011
A group of populations (different species) that live together in one area at a
certain time, ex: gophers, grasses, hawks in a field north of Balgonie
includes all organism (living things) in a certain area as well as the non-living
things (climate, soil, water, rocks, etc), ex; dugout north of Pilot Butte
major regional or global community of
organisms, commonly named for the
dominant plant life present, ex: grassland
biome, rain forest biome
Anywhere on planet Earth where life can be
found, from the highest mountains to the
deepest ocean trenches
The study of the interactions among living
things, and between living things and their
Questions 1-2, page 400
What are the five different levels of organization
studied by ecologists?
- organism, population, community, ecosystem, biome
Describe the three general methods used by
ecologists to study organisms.
Observations is the act of watching something over
time, such as a population of birds
Experimentation can occur in the lab or in the field
and involves testing a hypothesis
Modeling is a computer-based or math-based method
used to predict how changes in one variable may
Questions 3-4, page 400
What ecological research methods would you use to study bird
migration? Explain your choices.
Observations: band birds capture them at each end of their
migratory route to record their movement.
Experimentation: devise an experiment to test what triggers
Modeling: develop a computer model that includes different
variables that might predict the time and path of migration.
How might an ecologist use modeling to study a forest fire
ecosystem? What might be key variables used to create the
Ecologist could use models to determine movement of fire,
locations where prescribed burns should take place, and areas
with the potential for fire outbreaks. Key variables: forest
density, types of trees, plant and animal populations, wind
patterns, and weather conditions.
Question #5, p400
Ernst Haeckel was greatly influenced by the writings
of Charles Darwin. How do the principles of
ecology relate to the understanding how adaptations
Species are adapted to their environments. The
concept is directly related to the study of ecology, in
which the interactions between organisms and the
environment are studied. By understanding the
interactions within an ecosystem, scientists can
develop an understanding of how populations evolve
in response to their environments.
Random Quadrat Analysis - Used to sample a stationary
population to estimate it’s size
Best way to determine a population’s size????
Count them!! But this is commonly not practical and/or
Some individuals move around and are hard to count
Some individuals are spread out over a large area
Other sampling and population size estimation methods:
mark-recapture – used for mobile populations, mark a
caught individual and then release it. Capture many
individuals, if you recapture the same individuals = small
population, if you capture new individuals each time = large
Questions 1-3, page 404
Select an ecosystem that is familiar to you and describe the
and abiotic factors that exist there.
Answers should show that students understand that biotic
factors are living things and abiotic factors are nonliving.
2. How would the removal of a keystone species affect an
- The removal of a keystone species would decrease the
3. Explain how a change in an abiotic factor such as sunlight
would affect biodiversity.
Changes in amount of sunlight might affect local
temperatures, leading to a change in the numbers and types
of species in an ecosystem. New species may now move into
the area, taking the place of those that cannot survive.
Questions 4 & 5, page 404
Humans are sometimes described as being a keystone
species. Does the label fit? Why or why not?
Keystone species are those that help to establish and maintain
a complex web of life. Humans do not fit this label because
human activities often decrease, rather than increase
What role might an abiotic factor such as temperature play in
the evolution of a species?
A long-term temperature change could result in selective
pressure that selects individuals better adapted to the
temperature, causing populations to evolve. It could alter
the types of food available, again creating selective pressure
toward individuals that can take an advantage of different
Biotic and Abiotic Factors
Biotic factors – living things such as bacteria,
fungus, plants and animals
Abiotic factors – non-living things such as
moisture, temperature, wind, sunlight and soil.
Biodiversity – variety of living things in an
Keystone Species – species that has an
unusually large effect on an ecosystem.
Energy in Ecosystems
get their energy from non-living sources (make their
own food), sometimes called autotrophs
Get their energy either by photosynthesis (from
light) or chemosynthesis (from chemicals)
get their energy by consuming/eating another living
thing (dead or alive), sometimes called
Questions 1-3, page 407
How does the stability of an ecosystem depend on its
What are the two processes used by producers to
Producers bring energy into an ecosystem
Photosynthesis and chemosynthesis
Few producers live deep below a lake’s surface.
Suggest an explanation for this pattern.
- sunlight cannot penetrate the water to a great
depth, so photosynthesizing organisms are more
common near the surface.
Could producers survive without consumers? Explain why
or why not?
- Producers do not require consumers to fill material needs
as a food source. So in that sense, producers do not
need consumers to survive.
5. How might chemosynthetic organisms help scientists to
understand how life developed on Earth?
- Chemosynthetic organisms live in environments that may be
similar to those that existed on Earth billions of years ago,
when life was beginning to develop. Studying these
organisms enables scientists to infer how different life
forms may have evolved as Earth changed.
Questions 1-2, p411
Why are food chains especially useful for describing
the relationships of specialists?
Specialists have specific diets that include only one type of
organism, which produces a simple food chain.
What happens to energy as it flows through a food
Some energy is stored in the organism (10%), but much
energy is dissipated into the environment (90%).
Only a small percentage of all consumers are
specialists. What danger does a specialist faces that a
generalist does not?
If a specialist’s food source becomes scarce or disappears,
the population may die out. A generalist facing the loss of
one of its food sources can shift to a different food
How might the stability of an ecosystem be affected
if all the decomposers were suddenly removed?
The stability of the ecosystem would be negatively
affected because without decomposers, vital nutrients
would not be returned into the environment.
How might an oil spill in the ocean affect an aquatic
food web? What might happen to the food web on
land located near the spill? Explain your answers.
- The entire food web would be affected by the oil spill. Oily
water may kill off phytoplankton. The loss of smaller fish
would affect larger fish, which in turn affect tertiary
consumers. Plants and animals that live along the coast
would also be affected as the oil seeped onto the shore.
The overall effect would be a decline in the availability of
food sources both within and outside the ocean.
Questions 1-3, p416
How does the hydrological cycle move water through the
Precipitation falls to Earth, and transpiration and
evaporation transfer water back into the atmosphere as
What are four elements that cycle through ecosystems, and why
are they important?
- oxygen, carbon, nitrogen and phosphorus; they are all
necessary for life on Earth.
Why might farmers plant legumes such as peas to improve the
nitrogen levels in their soil?
- Legumes have root nodules, which contain nitrogen-fixing
bacteria. Increased levels increase the fertility of the soil.
Explain the importance of decomposers to the
overall biogeochemical cycle.
Decomposers break down organisms and release various
elements, including nitrogen and phosphorus, which other
organisms can then use.
How might Earth’s biogeochemical cycles help
scientists to understand the early history of life on
- Studies of the biogeochemical cycles and how they interact
may help scientists reconstruct the sequence of events that
led to changes at Earth’s surface that would enable
different types of organisms to evolve.
Questions 1-3, p419
How does an energy pyramid help to describe energy
flow in a food web?
An energy pyramid shows the relative contribution to
energy flow made by each trophic level in an ecosystem.
What is the difference between a biomass pyramid
and a pyramid of numbers?
A biomass pyramid compares the mass of organisms that
make up each trophic level in an ecosystem; a pyramid of
numbers compares the number of individual organisms
that make up each trophic level.
How would you draw a pyramid of numbers for a
dog with fleas? What shape would it take?
- The bottom level would be the dog, and the fleas would be
the top level. This would be an inverted pyramid because
there are many fleas to just one dog.
If each level in a food chain typically loses 90 percent
of the energy it takes in, and the producer level uses
1000 kcal of energy, how much energy is left after the
third trophic level?
The first trophic level uses 1000 kcal; the second trophic
level uses 100 kcal; the third trophic level uses 10 kcal,
leaving 1 kcal
Question 5, p419
Why is a herbivorous diet more energy efficient
than a carnivorous diet? Explain your answer.
a herbivorous diet is more energy efficient
because it is the closest trophic level to
producers, meaning there is more available
energy to use.
Questions 1-3, page 430
What are the three parts of an organism’s ecological niche?
Food type, abiotic conditions, and behavior
What does the principle of competitive exclusion say will happen
when two species compete for the same resource?
One species will be better suited to the niche and the other
species will either be pushed into another niche or become
If a group of mantella frogs were transported to the ecosystem of
the poison dart frogs, what might happen to the two species’
As ecological equivalents, they share a similar niche. The
population better suited to the niche might deprive the other of
resources, causing the other to die off. Or one population
might respond to limited resources by altering its niche.
Questions 4 & 5, page 430
A bison and an elk live in the same habitat and feed on the same
grasses. Does this mean that the competitive exclusion principle
does not apply? Explain.
The competitive exclusion principle only applies if the two
species occupy the same niche and habitat. These two species
use the same use the same food resource but occupy different
Exotic Species – Considering the competitive exclusion principle,
why may it be harmful to transport a species, such as a rabbit, to
another habitat where it currently does not exist?
If the new species is introduced to an area, it may occupy a
similar niche as a native species and be better adapted for the
niche or have no natural predators. This could drive native
species to extinction.
Questions 1-3, page 434
During the fall spawning of salmon, grizzly bears fight over
space on the banks of a river. What type of competition is
The bears are fighting among themselves, so it is
considered intraspecific competition.
Describe and give examples of the three types of symbiosis.
Mutualism: bee and flower, Commensalism: remora and
shark, parasitism: tick and human
How are predation and parasitism similar? How do they
They are both relationships in which one organism benefits
while the other is harmed. In predation, the predator
needs to kills its prey in order to benefit. In parasitism, the
parasite benefits by keeping the host alive.
Questions 4 & 5
After a lion has made a kill, birds will sometimes arrive to
pick at the leftover carcass. Which are the predators: the
birds, the lion, or both? Why?
The term predator is restricted to an organism that finds
and eats another living organism. The lion is the predator,
the birds are scavengers.
Animal Behavior - You have probably heard the saying
“There is safety in numbers.” Why might traveling in a large
group be beneficial to prey species?
A predator may become overwhelmed when facing a large
number of prey. Although a predator may have the speed
to chase down and kill a single prey animal., it may switch
from chasing one individual to another when faced with a
large group of prey and tire before it is successful.
Page 439, questions 1-3
A shoreline mussel species has a population density of one
organism per square meter. Will all mussels be found one meter
No, population density simply describes the number of
individuals per unit of area, not the dispersion pattern
Draw and label a diagram showing the three population
Student diagrams should include three dispersion patterns:
clumped, uniform and random. Like illustration on page 437!
How do survivorship curves show three types of reproductive
If the curve shows a low level of infant mortality, the parents
probably care for their young. If the curve shows a very high
infant mortality rate, the organisms probably have a high birth
rate and provide little or no parental care.
Question 4 & 5, page 439
What might be the advantages of having a clumped dispersal
Individuals do not have to move very much to find mates,
organisms have better protection from predators, and
there is more access to food resources from other
An organism has ten offspring. Two of these offspring die
each year over a five-year period. Is the organism more likely
to be a bird or an insect? Explain.
The organism is a bird because the mortality pattern
described is closest to type II. Insect tend to be type III,
with many offspring and high mortality in the early life
Abiotic Factors - On the African savannah, what
types of abiotic factors may lead to high population
density and clumped dispersion patterns?
Answers may include limited water supplies, high
temperatures, and little or no precipitation.
Question 1-3, page 444
What four factors determine the growth rate of a population?
immigration, births, deaths, emigration
How does carrying capacity affect the size of a population?
Carrying capacity limits the size of a population
What is the main difference between a density-dependent limiting
factor and a density-independent limiting factor? Give examples
A density-dependent limiting factor is affected by the number
of individuals in a given area, but a density-independent
limiting factor in not affected by population size. Examples of
density-dependent limiting factor includes predation,
competition and disease. Examples of density-independent
limiting factors include weather, natural disasters and human
Questions 4-6, p444
What might cause exponential growth to occur only for a
short period when a new species is introduced to a
Eventually, the growing population will consume all
available resources, and the species may experience a
Synthesize - How might density dependent limiting
factors be affected by a flood or some other natural
Answers might include effects such as a flood or other
natural disaster destroying resources, predators, or prey in
a area, which are density-dependent factors.
Symbiosis - Give an example of how a
symbiotic relationship could cause a population
If a parasite or disease spreads in a dense
population, it could cause a population to
decline dramatically over a short period of
Questions 1-2, p447
How is primary succession different from secondary
- Primary succession begins with bare rock, worn down and
colonized by pioneer species.
Why are pioneer species so important for primary
Pioneer species, such as mosses and lichens, can
break down rock into smaller pieces. When they die,
their remains mix with tiny pieces of rock to form a
thin layer of soil. They change the ecosystem in ways
that enable the support of more diverse species.
Infer - Does the process of primary succession take longer in tropical
or arctic areas? Explain.
Primary succession takes longer in arctic areas because rock is
covered with snow part of the year, the growing season is shorter,
and cold temperatures slow growth and decomposition. Soil takes
much longer to form.
Predict - During succession, what might become the limiting factor
for sun-loving mosses as taller plants begin to grow?
the amount of sunlight that reaches them.
Niche - At what point during primary succession does an ecosystem
provide the fewest habitats for organisms? Explain your reasoning.
There are no habitable areas in the earliest stages of succession
because there is no soil to support producers. Land becomes
habitable once rock has weathered enough to support mosses and
lichens. Over time, the mosses and lichens will provide the
resources needed to support other organisms.