Download Unit III- Ecology (Guided Notes)

Ecology: Populations and Species Interactions
Standards:
Biology 6c: Students know how fluctuations in population size in an ecosystem are
determined by the relative rates of birth, immigration, emigration, and death.
Biology 6e: Students know a vital part of an ecosystem is the stability of its producers and
decomposers.
Biology 6f: Students know at each link in a food web some energy is stored in newly
made structures but much energy is dissipated into the environment as heat. This dissipation may
be represented in an energy pyramid.
Changes in Population
Biology 6c
Population size over time depends on four variables:
1. Birth rate
2. Death rate
3. The rate of immigration into the population
4. The rate of emigration out of the population.
http://www.brainpop.com/science/ourfragileenvironment/populationgrowth/
What is it?
Does this increase or decrease the size of a population?
Birth
Death
Immigration
Emmigration
Types of Population Growth:
Growth
Define
Reasons for this
type of growth
Logistic Growth
Exponential
Growth
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Graph
Read the following paragraph and write a summary sentence.
Fluctuations in the size of a population are often difficult to measure directly but may be
estimated by measuring the relative rates of birth, death, immigration, and emigration in a
population. The number of deaths and emigrations over time will decrease a population’s size,
and the number of births and immigrations over time will increase it. Comparing rates for death
and emigration with those for birth and immigration will determine whether the population shows
a net growth or a decline over time.
Summary Sentence:
Which events will increase the size of a population?
Which events will decrease the size of a population?
CST Practice questions:
Step 1- Read Question
Step 2- Underline Key words
Step 3- Predict what your answer should look like
Step 4- Cross out incorrect answers and match your prediction to your answer choices
1. The population of Spain has declined over
the last two generations. What might be the
most logical explaination?
A. Immigration into Spain has been
greater than the combined birth and
death rates.
B. The birth rate in Spain has been
greater than the combined death and
emmigration rates.
C. The death rate in Spain has been
less than the combined birth and
emmigration rates.
D. The birth rate in Spain has been less
than the combined death and
emmigration rates.
2. In Ethiopia, the sweet potato butterfly can
cause major damage to crops. The
population of the butterfly can vary
considerably between years.
How can scientists determine when the
population of butterflies is increasing?
A. by comparing the numbers of
butterflies to their predators
B. by comparing the amount of damage
to the crops each year
C. by comparing the population of
other butterfly species to the
population of sweet potato
butterflies
D. by comparing the birth and
immigration rates to the death and
emigration rates of sweet potato
butterflies
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3. In the United States in 2005, the number
of births per 1,000 people was 14. The
number of deaths per 1,000 people was 8.
6. The salamander is an amphibian that lives
in or near water. During one year the
salamander population of a pond increases.
Based only on this information, and if this
trend were to continue, the population of the
United States most likely will
A. fluctuate.
B. increase.
C. decrease.
D. not change.
Which of these factors would best explain
the population increase?
A. an increase in the emigration rate of
the salamander
B. an increase in the birth rate of the
salamander
C. an increase in the population of the
salamander's predators
D. an increase in the immigration rate
of the salamander's predators
4. Wastes tend to accumulate in the
environment as a population reaches the
carrying capacity.
A. True
B. False
5. As a population reaches its carrying
capacity, there is an increase in competition
for
A. food.
B. shelter.
C. mates.
D. All of the above
Species Interactions
Biology 6e, 6f
What level study are species interactions?
Interactions
Competition
Define
Example
Food Chain
Symbiosis
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The Food Chain
Biology 6f
All organisms need energy in order to grow, reproduce, and perform the activities necessary for
survival. The amount of organic matter in an ecosystem is its biomass. The rate at which an
ecosystem’s producers build biomass is the ecosystem’s primary productivity.
Define primary productivity:
On average, only about 10 percent of the energy at one trophic level becomes available to the
next level. The other 90 percent is lost through:
• Uneaten organisms
• Heat lost to the environment
• Feces
• Individual animal’s body maintenance
Does that mean energy is lost or gained as it moves up the food chain? Why?
*Note: kcal stands for kilocalories. This measures the amount of energy in food. 1 kcal is actually what
we consider 1 “calorie” of food
Notice how as you move up the food chain less and less energy becomes available for the
next trophic level.
Why are there only 4-5 trophic levels in a given food chain?
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Read the following paragraph and write a summary sentence.
The energy pyramid illustrates how stored energy is passed from one organism to
another. At every level in a food web, an organism uses energy metabolically to survive and
grow, but much is released as heat, usually about 90 percent. At every link in a food web, energy
is transferred to the next level, but typically only 10 percent of the energy from the previous level
is passed on to the consumer.
Summary Sentence:
Draw your own energy pyramid that includes 4 levels:
As energy moves up the food chain, energy is _______. Only ____ % of the energy moves
up a trophic level.
CST Practice:
1. The amount of energy available to
individual comsumers in an ecosystem is
limited by
A. the number of producers.
B. the amount of sunlight.
C. the amount of predators.
D. the number of consumers
2. At each step in a food web, only
__________ of the energy is passed to the
next level.
E. 1%
F. 10%
G. 25%
H. 50%
2. In an ecosystem, plankton are eaten by
small fish. The small fish are eaten by larger
fish. About 10% of the energy present in the
tissues of all the plankton can be used by the
small fish.
What happens to a large amount of the
remaining 90% of the energy in the
plankton?
A. It is transferred to the big fish.
B. It is released as heat by the small
fish.
C. It is destroyed when the plankton
die.
D. It is recycled back to the bottom of
the food chain.
4. Which of these statements best explains
why most food webs have no more than four
or five levels?
A. There is natural selection at each
level.
B. There is great energy loss at each
level.
C. There is limited biodiversity at each
level.
D. There is an increase in biomass at
each level.
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5. All organisms in an ecosystem are part of
the food web of that ecosystem.
A. True
B. False
C. decomposer
D. herbivore
7. Animals that feed on plants are at least in
the
A. first trophic level.
B. second trophic level.
C. third trophic level.
D. fourth trophic level
6. In a food web, which type of organism
receives energy from every other type?
A. producer
B. carnivore
Roles of Consumers, Producers, and Decomposers in an Ecosystem
Biology 6e
Every organism (species) plays an important role in the environment. The greater the
biodiversity of an ecosystem, the ____________ the stability of the ecosystem because there are
more species that can perform the essential role.
Main Role
Examples
Picture
Producer
Consumer
Decomposer
The biodiversity of each organism maintains the balance of the ecosystem. The producers,
consumers, and decomposers are responsible for making energy available to other organisms.
The MOST important organisms responsible for the stability of the ecosystem are the
producers and decomposers.
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Read the following paragraph and answer the questions:
An ecosystem’s producers (plants and photosynthetic microorganisms) and decomposers
(fungi and microorganisms) are primarily responsible for the productivity and recycling of
organic matter, respectively. Conditions that threaten the stability of producer and decomposer
populations in an ecosystem jeopardize the availability of energy and the capability of matter to
recycle in the rest of the biological community.
Summary Sentence:
Why are producers important in an ecosystem?
Why are decomposers important in an ecosystem?
CST Practice
1.An ecosystem could survive without
which of the following organisms?
A. producers
B. consumers
C. decomposers
D. detritivores
4. Which of these situations would lead to a
decrease in the number of producers in an
ecosystem?
A. an increase in the number of
predators
B. an increase in the number of
herbivores
C. an increase in the number of
scavengers
D. an increase in the number of
decomposers
2. In a given ecosystem, one dominant
species goes extinct. In order to have the
largest effect on the ecosystem, what type of
food web role would this species have
filled?
A. primary producers
B. top predators
C. primary consumers
D. secondary consumers
5. In an ecosystem, why does the
productivity of each higher trophic level
decline?
A. The producers use all the energy
from the Sun that reaches Earth.
B. A large amount of heat energy is
lost at each level of the food web.
C. Sunlight energy is completely
recycled at each level of the food
web.
D. The primary consumers use all of
the energy present in the producers
3. A given ecosystem in extremely unstable.
What is the best explanation for why the
ecosystem lacks stability?
A. fluctuating populations of top
predators
B. fluctuating populations of
herbivores
C. fluctuating populations of secondary
consumers
D. fluctuating populations of
decomposers
7. The number of trophic levels in an
ecological pyramid
A. is limitless.
B. is limited by the amount of energy
that is lost at each trophic level.
C. never exceeds four.
D. never exceeds three
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Ecology Practice
Write each of the standards in the appropriate location and answer all questions.
Biology 6a:
What is the importance of Biodiversity?
What is a Population?
What is a Community?
What is an Ecosystem?
What are four factors that affect biodiversity in an Ecosystem?
Biology 6b:
What is going to happen to a producer if the number of consumers increases?
What is going to happen to the consumer if the number of producers decreases?
What is going to happen to the consumer if the number of producers decreases?
Biology 6c:
What two factors will increase a population?
What two factors will decrease a population?
What determines if a species grows exponentially or logistically?
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Biology 6d (cycles):
What two ways is Carbon added to the atmosphere?
In what two ways is carbon removed from the atmosphere?
What is the driving force for photosynthesis?
What must happen to nitrogen before it is usable?
How is Oxygen added to the atmosphere?
How is oxygen removed from the atmosphere?
Biology 6e:
What are the two most important trophic roles in an ecosystem?
What is the role of decomposers?
What is the role of producers?
Biology 6f:
What happens to the energy at each trophic level?
Why does the population of species get smaller as you move up the food chain?
Where does the 90% of energy lost go?
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