Download Answers for Anchor 8 Packet

ANSWERS
KEYSTONE REVIEW PACKET ANCHOR 8: ECOLOGY
LEARNING OBJECTIVES:
 Describe the ecological levels of organization in the biosphere
o Describe the levels of ecological organization (i.e., organism, population, community, ecosystem,
biome, biosphere)
o Describe characteristic biotic and abiotic components of aquatic and terrestrial ecosystems.
 Describe interactions and relationships in an ecosystem.
o Describe how energy flows through an ecosystem (e.g., food chains, food webs, energy pyramids).
o Describe biotic interactions in an ecosystem (e.g., competition, predation, symbiosis).
o Describe how matter recycles through an ecosystem (i.e., water cycle, carbon cycle, oxygen cycle, and
nitrogen cycle).
o Describe how ecosystems change in response to natural and human disturbances (e.g., climate
changes, introduction of nonnative species, pollution, fires).
o Describe the effects of limiting factors on population dynamics and potential species extinction.
Vocabulary:
Abiotic
Aquatic
Biogeochemical Cycle
Biome
Biosphere
Biotic
Concepts To Know:
Main Idea #1:
Levels of
Biological
Organization
There are many
different levels of
organization in living
things. The diagram
to the right shows all
of the different levels.
Ecology is the study
of how organisms
interact with their
environment and
therefore is
concerned with the
higher levels on the
diagram (Organism 
Biosphere)
Community
Competition
Consumer
Decomposer
Ecology
Ecosystem
Endemic species
Endosymbiosis Habitat
Energy Pyramid
Energy Transformation
Environment
Food Chain
Food Web
Limiting Factor
Nonnative Species
Population
Population Dynamics
Producer
Succession
Symbiosis
System
Terrestrial
Trophic Level
1. Using the headings from the diagram on the previous page, label the missing levels of ecological organization on the
diagram below:
Biosphere
Biome
Ecosystem
Population
Organism
Community
Main Idea #2: Abiotic vs Abiotic Factors
Ecosystems have
both living
components (biotic
factors such as the
trees, birds, and fish)
and nonliving
components (abiotic
factors such as how
much rain or sun an
area gets).
2. Looking at the
diagram to the right,
categorize each
labeled item as either
biotic or abiotic:
Wind, soil, water
Trees
deer fish
Sun
Duck
butterfly
soil
rocks
soil
Main Idea #3: Flow of Energy in an Ecosystem
All ecosystems need energy, and the most basic form of energy comes from the sun. Producers (also known as
autotrophs or “self-feeders”) are able to make their own food. Producers are eaten by consumers (also
known as heterotrophs or “other feeders”). We can track the flow of energy linearly using a food chain or
look at a more detailed flow of energy using a food web. An organisms trophic level is its position with in
these.
Within an ecosystem, we can track the number of organisms, the amount of energy available and amount of
biomass (relative amount of organic matter). In all ecosystems, the amount of these three will decrease as
you move up through the trophic levels, therefore they take on the shape of a pyramid. Below are examples
of each of these pyramids.
3. What is a trophic level? List and describe different trophic levels in ecosystems.
Trophic level is the position of an organism in a food chain or web, can be a producer, consumer (primary,
secondary, etc) or decomposer.
4. How do producers and consumers differ in how they obtain energy?
Producers make their own food (ex/plants via photosynthesis), consumers have to eat (consume) their
food. Consumers can eat plant material (herbivores), meat (carnivores), or both (omnivores).
5. What happens to energy as it moves through the trophic levels of an ecosystem?
The amount of usable energy decreases as you move through a food chain/web’s trophic levels. Only about
10% of the energy from the previous trophic level moves on to the next.
6. What happens to biomass and numbers of organisms as you move through trophic levels of an ecosystem?
These also decrease, since there is less and less energy available at each higher trophic level, an ecosystem
cannot support as many organisms in higher levels.
7. What is the ultimate source of all energy on earth? The SUN
Main Idea #4: Interactions Between Living Things in an Ecosystem
Organisms can interact with each other in many
different ways. Symbiosis is the general term for
organisms that closely interact with each other.
8. Using information in the chart to the right, list
which type of relationship is being described in each
situation below:
___MUTUALISM_____ a. Cleaner fish eat parasites and
dead cells from other fish, such as grouper. The
cleaner fish get food, and the grouper avoid disease
__COMMENSALISM_____ b. Some mites attach to
flies for transportation. The mites are able to move
from one place to another, and the flies are not
affected.
__PARASITISM___ c. Fleas feed on the blood of dogs.
The fleas get food, but the dogs experience itching and
discomfort.
__PREDATION____ d. A wolf hunts and kills a sheep
_COMPETITION____ e. Plant species grow taller to reach
more sunlight
NICHE vs HABITAT –


Habitat = where an organism lives
Niche = that organism’s role in it’s habitat (what it eats,
how it interacts with other organisms, when it
reproduces, etc)
NO TWO SPECIES CAN OCCUPY THE SAME NICHE AT THE SAME
TIME (OR COMPETITION RESULTS) Species can divide up a niche
to make smaller niches – see warblers to right.
Main Idea #5: Cycles of Matter
Nutrient Cycles
Important nutrients such as carbon, nitrogen, phosphorus, and water are cycled through living things and the
environment through biogeochemical cycles. The following pictures are overviews of the carbon, phosphorus,
and nitrogen cycles.
Carbon Cycle
Nitrogen Cycle
9. How is the movement of matter in an ecosystem different than the movement of energy?
Matter is recycled, energy does not get recycled
10. What processes add water to the atmosphere? What process removes water from the atmosphere?
Add: Transpiration & evaporation
Removes: Precipitation
11. What process adds carbon to the atmosphere? What process removes it?
Adds: Cellular respiration (all organisms release carbon dioxide gas)
Removes: Photosynthesis (plants/algae consume carbon dioxide gas)
12. What process makes nitrogen available to living things? Who does this process?
Nitrogen fixation converts nitrogen gas to usable compounds for plants. This is done by bacteria living in the soil.
Main Idea #6: Responses to Natural and Human Disturbances
Succession: The orderly process by which an ecosystem changes over time. First species to arrive are called pioneer
species, which get replaced systematically over time, eventually ending with a stable climax community. Succession
occurs in one of two patterns – primary or secondary.
Primary Succession
Begins with a surface that did not previously support life
(bare rock)
No soil present
Lichen (can break down rock) and moss come first
Occurs more slowly
Secondary Succession
Begins in an area that previously supported life, but has
been removed or been abandoned
Soil present
Grasses & annuals come first
Occurs more quickly
Impact of Invasive Species: Invasive (nonnative) species live outside of their normal range and compete with native
(endemic) species. They may be introduced by shipping or as discarded pets. Populations of invasive species grow
rapidly because:



They have fewer predators or no predators in their new ecosystem
They use more of the ecosystem’s resources or use available resources more effectively
They may reduce other endemic populations directly through predation
13. A tornado completely destroys a cornfield on a farm. The farmer decides to not re-plant his crops, and
instead sells the farm. Describe what type of succession would follow if no one buys the farm for 20 years.
Secondary succession, because soil was already present and life had previously been supported on the farm.
14. You decide it would be cool to buy a couple of piranhas and add them to your fish tank. After they have
killed all of your fish, you decide to throw them into the large lake behind your house. Why would this be a
bad idea?
The piranhas would be a non-native, or invasive species to the lake. They would have few or no predators,
could & could quickly reproduce and start to impact the native (endemic) fish species already in the lake.
This could upset the whole lake ecosystem.
Human Impact on the Environment:
A) Agricultural Runoff and Eutrophication
Agricultural runoff – when fertilizers added to crops dissolve in rain and get carried
to nearby bodies of water.
Eutrophication - demonstrates how changing nutrient levels affect the organisms in
an ecosystem. Eutrophication occurs in stages:
1. Increase of nutrients (usually nitrogen and phosphorus because they are
limiting nutrients) in body of water due to runoff.
2. Photosynthesis increases (sometimes called an algal bloom because the
algae covers the top of the body of water)
3. As these producers die, the decomposers come in to feed off of them.
4. These decomposers are going through respiration and lower the oxygen
available to all organisms that can cause many to die.
B) Atmospheric and Climate Change
Greenhouse gases: trap heat energy in the atmosphere EX/ water vapor, carbon dioxide, nitrous oxide, methane

Many human activities raise greenhouse gases in the atmosphere (burning fossil fuels, deforestation)
Greenhouse effect: natural process in which certain gases in the atmosphere retain heat radiating from Earth’s surface
Global warming: an increase in average temperatures worldwide; contributes to climate change

Increasing average temps even a few degrees will have large effects on ecosystems (EX/melting ice caps causing
sea levels to rise – flooding coastal areas)
Ozone layer: region of the upper atmosphere in which high concentrations of ozone gas absorb much of the sun’s UV
radiation


Holes in the ozone layer are caused by CFC’s (commonly used in cooling agents) – can destroy ozone
Holes increase amount of UV radiation reaching Earth’s surface (can harm crops and marine organisms like
plankton)
C) Habitat Destruction


Habitat destruction is the leading cause of extinction of endangered species
Habitat destruction decreases the amount of biodiversity (variety of life forms) in an area
Pollution: addition of substances, objects or other factors that cause harmful changes to an ecosystem
Deforestation: clearing of all trees from an area; can greatly affect organisms in an ecosystem
15. Briefly describe one impact that humans have on the environment:
Answer: summary of one of the areas listed above: Agricultural runoff, atmospheric and climate change, or
habitat destruction
Main Idea #7: Limiting Factors on Population Dynamics
Population Dynamics: Study of the changes in population size.
 Factors that increase population size: births, immigration
 Factors that decrease population size: deaths, emigration
A limiting factor is some sort of factor (biotic or abiotic) that is going to limit the population’s growth. It could
be an important nutrient that is cycled through the ecosystem (such as water, nitrogen, carbon, or
phosphorus), or it could be a food source or predator. A great example of limiting factors are predator-prey
graphs. It is easy to see how the size of the population is affected.
Here, the size of the populations depends on the number or prey and
predators. The predator population peaks after the prey population
because of the lag time in reproduction. When the predator population is at
its highest, the prey is at its lowest. With limited food, the population size of
the predator decreases. This allows the prey population to increase, and
the cycle continues again…
Carrying Capacity is the maximum population size
an ecosystem can support, and is determined by
the effects of different limiting factors.
Growth curves: exponential (growth under ideal
conditions) vs logistic (growth with limiting
factors):
PRACTICE QUESTIONS:
1. Which of the following is a biotic-biotic interaction?
a. A snake warming on a sunny rock
b. A rainstorm washing nutrients from the soil
c. A human shivering because of cold weather
d. A squirrel gathering acorns from an oak tree
2. Which statement correctly describes a part of an ecosystem?
a. A community consists of both biotic and abiotic factors
b. A community is made up of different types of organisms
c. A population is an abiotic factor affecting the ecosystem
d. A population consists of different species living in an area
3. Which piece of evidence best supports the following statement?
“In an ecosystem, the total amount of matter remains constant, even though its form and location
change”
a. Producers capture energy from sunlight
b. Most food chains have three levels or fewer
c. Decomposers return nutrients to the environment
d. Multiple food chains can be combined into a food web
4. Small birds eat insects from the backs of rhinoceroses. The birds obtain food, and the rhinoceroses eliminate
biting insects from their skins. Which ecological relationship is not represented by this situation?
a. Commensalism
b. Mutualism (birds get food, rhinos get rid of bugs)
c. Parasitism (insects biting rhinos)
d. Predation (birds hunting insects)
5. Which trophic level is generally the smallest in a terrestrial ecosystem?
a. Producer
b. Primary consumer
c. Secondary consumer
d. Tertiary consumer
6. Which statement describes the function of producers in Earth’s biogeochemical cycle?
a. Producers add nitrogen to the atmosphere and remove oxygen from the atmosphere
b. Producers remove carbon dioxide from the atmosphere and add oxygen to the atmosphere
c. Producers add carbon dioxide to the atmosphere and remove oxygen from the atmosphere
d. Producers remove nitrogen from the atmosphere and add carbon dioxide to the atmosphere
7. The carbon dioxide in the atmosphere is an inorganic form of carbon. Organic compounds contain both carbon
(C) and hydrogen (H). Which process in the carbon cycle changes carbon to an organic form?
a. Respiration
b. Photosynthesis
c. Burning of fossil fuels
d. Burial of dead organisms
8. A multicellular consumer can obtain nitrogen for use by its cells in which of the following forms?
a. Nitrites (plants get from soil)
b. Nitrates (plants get from soil)
c. Amino acids (consumers get from eating plants or animals)
d. Nitrogen gas (bacteria get from atmosphere)
9. Forests of American beech and sugar maple trees are a type of climax community found in parts of western
Pennsylvania. Which statement is most likely true concerning these plant species?
a. Their roots change environments of bare rock to fertile soil
b. Their seeds grow best in bare soil with little other plant life
c. They reduce the ecosystem’s carrying capacity for grasses and shrubs
d. They alter the ecosystem so that it is better suited for other plant species
10. Flooding can impact aquatic ecosystems by increasing turbidity. Turbidity refers to the amount of solid material
suspended in water. Turbid water appears cloudy or muddy. What is the most likely effect of increased
turbidity on an aquatic ecosystem?
a. The water contains less dissolved oxygen (bc not as much light – so not as much photosynthesis)
b. Large fish are able to take in more energy
c. The water contains fewer dissolved nutrients
d. Small fish are more easily caught by predators