Name: __________________________________
Unit 8: Ecology
Per. _______
Part A: Environmental Organization
ecology
levels of organization
 population
 community
 ecosystem
 biosphere
abiotic factors
biotic factors
biomes


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tundra
taiga
temperate deciduous forest
tropical forest
grassland
desert
marine
Part B: Energy and Nutritional Relationship
nutritional relationships
 autotroph
 heterotroph
 carnivore
o predator
o scavenger
 herbivore
 omnivore
 saprophyte
symbiotic relationships
 mutualism
 commensalisms
 parasitism
energy flow
 food chain
 food web
 pyramid
material cycle
 carbon-oxygen cycle
 nitrogen cycle
 oxygen cycle
Part C: Populations & Communities
population
 stable populations
 unstable populations
 exploding populations
population growth
competition
limiting factors
community






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biodiversity
habitat
niche
community development
ecological succession
pioneer organisms
climax community
Part D: Human Impact on Ecosystems
renewable resources
 food
 soil
non-renewable resources
 water
 fossil fuels
human activities and loss of diversity
 poaching
 deforestation
 imported species
pollution of natural resources
 industrialization
 water pollution
 air pollution
o global warming
o ozone depletion
conservation of natural resources
 recycling
 conserving available resources
 wildlife preservation
 biological controls
1
Part A: Environmental Organization
Ecology- the study of interaction of organisms with their environment
Today’s environment is influenced by:
 exploding human population: 6.9 billion today (and growing)
 6th mass extinction of species (30,000 species/ year): now more than ever.
 thinning of the ozone layer: 1% of UV radiation gets through causing sunburns and a half million deaths
per year.

Greenhouse Effect: trapping greenhouse gases (like carbon dioxide) against the earth’s surface and
causing warming.
Levels of organization:
Environment is made up of:

Abiotic Factors- non-living, physical factors
ex. temperature, weather, altitude, minerals, air, soil, availability of water, and sun

Biotic Factors- living things affecting an ecosystem
ex. food supply, other organisms (producers, consumers, decomposers)
1. Ecosystems involve interactions between biotic and abiotic factors. Name five abiotic and five biotic factors
that might make up an ecosystem.
Abiotic- temperature, amount of sun, amount of water, minerals, gases
Biotic- trees, grasses, bacteria, human, dog
______________________________________________________________________________________
2. Identify one abiotic factor that would directly
affect the survival of organism A shown in the diagram.
-amount of water
-temperature of water
-dissolved oxygen
2
Terrestrial Biomes
Biome- areas of the biosphere that can be identified by dominant plant and animal species
 Climax Vegetation- group of plants that dominate a terrestrial biome
o climate influences the type of vegetation and therefore types of animals that live in an area
1. The Tundra
 permanently frozen subsoil (perma-frost)
 lichens, mosses, and grasses
 caribou, snowy owl
2.
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

The Taiga
long sever winters, summers with thawing subsoil
conifers (spruce, firs, pines)
moose, black bear
3.
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

The Temperate Deciduous Forest
moderate rainfall, cold winters, warm summers
deciduous trees (oak, maple, elm)
gray squirrels, fox, deer
4.
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

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The Tropical Forest
heavy rainfall, constant warmth
many species of broad-leaved plants (bamboo, ferns); fertile soil
snakes, monkey, leopard
a lot of biodiversity
5.



The Grassland
considerable variability in rainfall and temperature; strong prevailing winds
grasses (savannah= grassland with scattered trees)
pronghorn antelope, prairie dogs, bison
6.



The Desert
sparse rainfall; extreme daily temperature fluctuations
drought- resistant shrubs and succulent plants (cactus)
kangaroo, rats, lizards
Aquatic Biomes
largest ecosystem on earth
more than 70% of earth covered by water
typically more stable than land biomes
temperature varies less
affected by:
o amounts of O2 & CO2
o temperature & light
o amounts of dissolved minerals & suspended particles
1. Marine
 saltwater
 photosynthesis carried out by algae on surface
 light only penetrate about 30 meters (no autotrophs below 30 meters)


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2. Freshwater
 ponds, lakes, streams, and rivers
 variation in size and speed of current, temperature, and concentrations of dissolved gases
3
Practice:
1. Which is an abiotic factor that would affect the ability of a species of tree to survive in a particular habitat?
(1) availability of minerals in the soil
(3) climax vegetation of the area
(2) type and number of tree parasites present
(4) type and number of herbivores present
2. What is the major environmental factor limiting the numbers of autotrophs at great depths in the ocean?
(1) type of seafloor
(3) availability of minerals
(2) amount of light
(4) absence of biotic factors
3. An example of a population is
(1) all the Zapus hudsonicus in New York State
(2) all the fish in Lake Erie
(3) the numbers of different species of felis in a geographic area
(4) the number of maples, white oaks, spruce, gray squirrels, and owls in a forest
4. The maintenance of a self-sustaining ecosystem requires a
(1) constant temperature
(3) greater number of herbivores than producers
(2) soil that is acidic
(4) cycling materials between organisms and their environment
5. Many more species of plants and animals live in a tropical forest than live in a desert. This difference most likely
is due to the fact that, compared to a tropical forest, a desert
(1) has less available sunlight
(3) contains soil with sand
(2) contains less water
(4) has more carbon dioxide in the atmosphere
6. Which type of biome occupies the largest area of Earth?
(1) marine
(2) grassland
(3) tropical rain forest
(4) temperate deciduous forest
7. Which statement concerning an ecosystem is correct?
(1) It can exist with or without a constant course of energy input.
(2) It must contain consumers but can exist without producers.
(3) It involves interactions between biotic and abiotic factors.
(4) It can exist on land, but it cannot exist in lakes, rivers, or oceans.
8. Which abiotic factor has the least effect on the ability of aerobic organisms to live and reproduce in a cave?
(1) shape of rocks in the cave
(3) amount of energy present in the cave
(2) amount of oxygen in the cave
(4) availability of moisture in the cave
9. A moss-covered log is overturned by a hungry bear looking for insects to eat. The bear disturbs an ant colony,
and some chipmunks leave the hollow log to search for another home in the forest. Which relationship do these
organisms have with each other?
(1) They are all the same species
(3) They all require the same type of food
(2) They are part of a community
(4) They are abiotic factors in a forest
10. The fact that an organism cannot live without interacting with its surroundings is a basic concept in the field of
study known as
(1) anatomy
(2) embryology
(3) ecology
(4) physiology
11. The portion of Earth in which all life exists is known as
(1) the climax stage
(2) the biosphere
(3) a population
(4) a biotic community
12. Which group can be best described as a population?
(1) all the honeybees in an orchard
(3) the living and nonliving factors in a meadow
(2) all the plants and animals in a forest
(4) the life in Earth’s atmosphere
4
Part B: Energy & Nutritional Relationships
Nutritional Relationships
Nature of Ecosystems
 Biosphere - the part of the atmosphere that contains living things
 Ecosystem - all the organisms in an environment (community) plus the nonliving physical factors (temperature,
soil.etc)
 Biotic Components of an Ecosystem
o Autotrophs = Producers - the producers of food, usually plants, they create organic nutrients using an
outside energy source (photosynthesis)
o Heterotrophs = Consumers - gain their energy by feeding on other organisms
 Carnivores: eat other animals
 predators: kill and consume their prey
 scavengers: feed on dead animals they find
 Omnivores: eat both plants and animals
 Herbivores: eat plants only
 Saprophytes (decomposers): feed on dead bodies
Symbiotic Relationships

symbiosis- relationship between two or more species where at least one member benefiting
o
mutualisim - both organisms benefit
ex: nitrogen-fixing bacteria
o
commensalisms - beneficial to one, other not affected
ex: sharks and the remora
o
parasitism - one benefits (parasite), the other harmed (host)
ex: athlete’s foot fungus; tapeworms
Energy Flow



energy flows through an ecosystem starting from the sun, then to the producers and consumers. At each level,
some of the energy is lost as heat
Food Chains
o single path of animals eating
o producers  primary consumer  secondary consumer  higherlevel consumers  ecosystem
o ex: Plants  Caterpillars  Sparrows  Hawks
o decomposers present at all levels to break down
Food Webs show more connections among members in a community
o shows how plants and animals are connected by different paths
5
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
Trophic levels - the level of nourishment within a chain or a web, there should be fewer organisms as you go up
each level
this leads to Ecological Pyramids
Pyramid of Numbers
Pyramid of Biomass
Practice:
1. The diagram below represents a pyramid of energy that includes both producers and consumers.
The greatest amount of available energy is found at level
(1) 1
(2) 2
(3) 3
(4) 4
2. A sequence of events associated with ecosystem stability is represented below.
sexual reproduction  genetic variation  biodiversity  ecosystem stability
The arrows in this sequence should be read as
(1) leads to
(2) reduces
(3) prevents
_
3. A food web is represented on the right.
A continuous decrease in the size of the rabbit population would most
likely cause a decrease in which other population?
(1) frog
(2) cricket
(3) grass
(4) mountain lion
4. Which sequence shows a correct pathway for the flow of energy in a
food chain?
(1) bacteria  grass  fox  owl
(2) grass  grasshopper  frog  snake
(3) fungi  beetle  algae  mouse
(4) algae  snake  duck  deer
6
(4) simplifies
Material Cycles
Carbon-Hydrogen-Oxygen Cycle
 photosynthesis: carbon dioxide + water  glucose (C6H12O6) + oxygen (O2)



respiration: glucose + oxygen  carbon dioxide + water (H2O)
one process provides materials for the other
in balanced communities, supplies of the elements carbon, oxygen, and hydrogen should be self-sustaining
Nitrogen Cycle
 making nitrogen available for protein synthesis
 decomposers and other soil bacteria convert nitrogenous wastes of animals to a form useable by plants
(denitrification)
 nitrogen fixing bacteria capture atmospheric nitrogen in nodes of plant roots
Water Cycle
 water is required for all life forms
 involves: precipitation, evaporation, condensation, percolation, and runoff
 all help to distribute water throughout the environment
Review:
1. carnivores include all of the organisms that are meat eaters.
2. An animal which feeds on animals which have been already killed is called a(n) scavengers.
3. All plant eating organisms are known as herbivores.
4. Organisms that consume both plants and animals are collectively called omnivores.
5. Ecology is the study of the interactions of living things with each other and their environment.
6. A(n) population includes all of the organisms of the same species that inhabit a given location.
7. A carnivore which kills its own food is called a(n) predator.
8. All of the interacting organisms of different species in a given location comprise a(n) community.
9. Biotic factors are those living factors in the environment, such as disease and predation.
10. An organism such as a mushroom on a rotting log, which ingests decaying organic material is called a(n)
decomposer/saprophyte.
11. The entire region of the world where living things are found is called the biosphere.
7
Practice:
1. An owl cannot entirely digest the animals upon which it preys. Therefore, each day it expels from its mouth a
pellet composed of materials such as fur, bones, and cartilage. By examining owl pellets, ecologists are able to
determine the
(1) autotrophs that owls prefer
(3) organisms that feed on owls
(2) pathogens that affect owls
(4) consumers that owls prefer
2. Animals that feed excluseively on herbivores are known as
(1) primary consumers
(2) carnivores
(3) omnivores
(4) producers
3. Decomposition and decay of organic matter are accompanied by the action of
(1) green plants
(2) bacteria and fungi
(3) viruses and algae
(4) scavengers
4. As water cycles through an ecosystem, which process returns it to the atmosphere?
(1) hydrolysis
(2) transpiration
(3) condensation
(4) decomposition
5. The first organism in most natural food chain is
(1) an herbivore
(2) a decomposer
(3) photosynthetic
(4) carnivorous
6. Young rabbits that eat grass are sometimes eaten by raccoons, which also eat seeds and berries. Bacteria help
to decompose the excretions of the raccoon. Which statement about these nutritional relationships is accurate?
(1) Bacteria are scavengers.
(3) Rabbits are secondary consumers.
(2) Raccoons eat only producers.
(4) Raccoons are both primary and secondary consumers.
7. The diagram shows living and nonliving factors and the interaction between them.
The diagram best represents
(1) a species
(2) a population
(3) a community
(4) an ecosystem
8. Which statement best describes an energy pyramid?
(1) There is more energy at the consumer level than at the producer level.
(2) There is more energy at the producer level that at the consumer level.
(3) There is more energy at the secondary-consumer level than at the primary-consumer level.
(4) There is more energy at the decomposer level than at the consumer level.
9. The exchange of useful chemicals between organisms and their abiotic environment is an example of
(1) a material cycle
(3) a limiting factor
(2) competition
(4) succession
10. When animals excrete nitrogenous wastes into the soil, certain soil bacteria convert these wastes into nitrates,
which are absorbed by plants. These soil bacteria function as
(1) autotrophs
(2) secondary consumers
(3) decomposers
(4) abiotic factors
8
Use the diagram below to answer questions 11 through 14.
11. Which level of the pyramid contains autotrophic organisms?
(1) level A
(2) level B
(3) level C
(4) level D
12. Which organism is a primary consumer?
(1) alga
(2) crustacean
(4) great blue heron
(3) sunfish
13. Which is a possible food chain sequence derived from this energy pyramid?
(1) sunfish – algae – great blue heron – crustaceans
(2) great blue heron – crustaceans – sunfish – algae
(3) algae – crustaceans – sunfish – great blue heron
(4) crustaceans – great blue heron – algae – sunfish
14. Which level of the pyramid contains the greatest number of organisms?
(1) level A
(2) level B
(3) level C
(4) level D
15. The diagram illustrates some ecological interactions.
The diagram best represents the
(1) number of populations in the biosphere
(2) ecological succession in a biotic community
(3) pathway of energy as it is transferred
through an ecosystem
(4)physical interactions between the organisms
in a population
9
Part C: Populations and Communities
Population
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Stable Populations- number of organisms in population remains constant with only small periodic changes
Unstable Populations- number of population drastically reduced
o endangered species- without some form of human protection, entire species may become extinct
o ex: blue whale, timber wolf
Exploding Populations- rapid reproduction of a species
Population Growth


Factors that determine how much a population will change:
1. births
2. deaths
3. migration
Stable populations occur when there are as many individuals joining (birth or immigration) as leaving (death or
emigration)
Biotic Potential: maximum rate at which a population could grow given optimal conditions (food, water, space)
Factors that influence biotic potential:
1. age of reproduction (20 minutes like bacteria or 15-20 years like people?)
2. frequency of reproduction (time between birth events)
3. number of offspring produced (100s like frogs & fish, or 1 at a time like people & elephants?)
4. reproductive life span
5. average death rate under ideal conditions
Population Growth Patterns
J-shaped curve showing exponential growth of a
population
Lag Phase then Exponential Growth
This population has not yet reached its carrying
capacity.
Requires unlimited resources
10
S-shaped curve shows how a population becomes
limited by environmental factors
Lag Phase, exp growth phase, Deceleration, Stable
Carrying capacity: the maximum size of a population
that an area can support
Environmental Limits on Population Size
Competition- struggle for resources among organisms
Limiting Factors- anything that limits the growth of population
Population Density- number of organisms in a specific area
Density Independent Factors: weather and other natural disasters, pollution
Density Dependent Factors: food, space, water, parasitism, competition, disease
 parasitism and disease- parasitism more frequent in dense populations

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parasite rarely kills its host
predation- most populations controlled by predators
stress- high population density causes aggression, disease, declines in births, etc.
space and food- acts as limiting factors in natural environments
in some populations, a high density can be an advantage
ex. honeybees, school of fish, herd of zebras
Human Population Growth
1. The human population is now in an exponential part of a J-shaped growth curve.
2. World population increases the equivalent of one medium-sized city (216,000) per day and 79 million per
year.
3. The doubling time is the length of time for a population size to double, now 53 years.
Community
Community = assemblage of populations interacting with one another
Ex. squirrel, moose, bear, fox, wolf, pine tree, termites, bacteria....etc
Composition: what organisms live there | Diversity: abundance of different
species (biodiversity)

Structure of the Community
 Habitat - particular place an organism lives
 Ecological niche - the role it plays in the community


competition: struggle for resources between different species
Competitive Exclusion Principle - no two species can occupy the same niche
P. caudatum dies out as a result of competition
11
Predator-Prey Interaction
*You can see an obvious cycle: prey numbers go up followed by predator numbers going up, then prey drops,
predators drop

Prey Defenses
o Camouflage (cryptic coloration) - blending in
o Mimicry - one species resembles another as a defense (milk snake)
o Herding Behavior (zebra)
o Startle Behavior (blowfish)
o Anatomical defense (porcupine)
o Chemical defense (skunk)
Which of these snakes is
venoumous?
Community Development
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Ecological sucession - involves a series of species replacements
Primary Succession - occurs where there is no soil formation
(volcanic island)
Pioneer organisms- first organism to populate a given area
Secondary Succession - occurs after an area is disturbed (prairie
fire)
Pioneer Species - first species to inhabit an area
Climax Community - when the species replacement slows and the
ecosystem stabilizes
Community Biodiversity
moderate disturbances in an ecosystem are necessary to maintain
biodiversity
Keystone Species - needed to maintain biodiversity (often top
predators)
o Ex. Kelp, Sea otters, Sea urchins, Abalone - what
happens when you remove the otters?
12

Exotic Species - a species introduced into a habitat, often causes major disturbance and even extinction of
native species
o Ex: Kudzu, Snakehead catfish, Piranha, Mussels
Are zebra mussels really invading?
In the mid-1980s a new species found its way to North America. The zebra mussel (Dreissena polymorpha), a small,
clamlike mollusk that grows to about 25 cm as an adult, was introduced into the waters of the Great Lakes, probably carried in
the bilge of a Russian freighter. The zebra mussel can reproduce in less than a year, and a single female can release 1 million
eggs each year. In the absence of their natural pathogens, parasites, and predators, the zebra mussel populations in the Great
Lakes has grown enormously and are now invading eight major river systems, including the St. Lawrence, Hudson, Mississippi,
Ohio, Illinois, Tennessee, Susquehanna, and Arkansas rivers. The mussels are spread from one body of water to another by
natural flow, carried on the feathers or feet of migrating waterfowl, or by human transport in bait buckets or on trailered
boats. Most of the freshwater systems in North America are now threatened by invasion of the zebra mussel.
The zebra mussels grow in massive colonies, where nearly a half million individuals may grow on each square meter of
substrate. These colonies encrust the hulls and rudders of ships, the hinges of lock gates, and block the drains and intake ducts
used by industries and power stations. In 1990, for example, Detroit Edison spent over $500,000 to remove zebra mussels from
the intake pipes of its power plants.
The zebra mussels also have severe negative effects on the local ecosystem. As filter-feeders, they take in water and
filter out algae as food, excreting their waste as sediment. A single individual can filter 1 liter of water each day, and a colony
covering 1 square meter of substrate can filter 180 million liters of water per year. Enormous colonies of zebra mussels can
reduce the algal populations of lakes and rivers, thus removing a significant portion of the base of the food chain and resulting
in a decline in the fish populations. Thus, these mussels are a threat to the local biodiversity.
The tremendous filtering capacity of these organisms may have some positive consequences. Zebra mussels have been a
major factor in cleaning Lake Erie after a century of pollution from fertilizers and sewage. After the first 10 years of zebra
mussel existence in Lake Erie, light penetration in the water has increased from only a few centimeters to nearly 10 meters. If
these organisms could be controlled, they may become a useful tool in the treatment of sewage and pollution.
(Adapted from: Bush, Mark B. 1997. Ecology of a Changing Planet. Prentice Hall, Upper Saddle River, N.J.)
Questions
1. Which of the following best summarizes the author's
main point?
a. Zebra mussels are harmful to the great lakes
b. Zebra mussels are harmful to all lakes
c. The importation of zebra mussels should be regulated
d. Many lakes and river systems are polluted
2. Zebra mussels can move from one lake to another by
which method?
a. on the feet of birds
b. carried by the wind
c. moving overland for short periods
d. swimming up canal systems
3. Massive colonies of zebra mussels cause problems
because:
a. they destroy the engines of boats
b. they block the flow of water through ducts
c. they produce waste that pollutes the water
d. they eat large amounts of fish
4. Which of the following is a consequence of the zebra
mussel population in the great lakes
a. cleaner water
c. decline in fish populations
b. decline in algae populations
d. all of these
5. Why are zebra mussels a problem in the Great Lakes but
not in the lake systems where they came from?
a. the other lakes are too cold for them to reproduce in
large amounts
b. they have natural predators in the other lakes
c. they cannot leave these lakes
d. they cannot grow into colonies
6. How might zebra mussels be used to improve lake
systems?
a. they can be grown as food for humans
b. they can be used to strengthen dams and levies
c. they clean the water of pollutants
d. they remove algae from the water
7. What do zebra mussels eat?
a. algae
b. fish c. insects
d. water plants
13
Review:
1. Which statement concerning the climax stage of an ecological succession is correct?
(1) It changes rapidly.
(3) It is the first community to inhabit an area.
(2) It remains until the environment changes.
(4) It consists entirely of plants.
2. A stable climax community is able to exist in a certain geographic region for a long time because it
(1) provides a habitat for parasites
(3) attracts many pioneer organisms
(2) alters the climate of the geographic region
(4) remains in equilibrium with the environment
3. What is a characteristic of a stable environment?
(1) It usually contains only one type of producer.
(2) It usually contains a great diversity of species.
(3) It contains simple food chains that have more consumers than producers.
(4) It contains complex food webs that have more heterotrophs than autotrophs.
4. Compared to a natural forest, the wheat field of a farmer lacks
(1) heterotrophs
(3) autotrophs
(2) significant biodiversity
(4) stored energy
5. An ecosystem will most likely remain stable if
(1) it has more predators than prey
(2) it has a high level of biodiversity
(3) biotic factors decrease
(4) finite resources decrease
6. The widest variety of genetic material that can be used by humans for future agricultural or medical research
would most likely be found in
(1) a large field of a genetically engineered crop (3) a forest that is planted and maintained by a forest service
(2) an ecosystem having significant biodiversity
(4) areas that contain only one or two species
7. What would most likely occur after an ecosystem is disrupted by fire?
(1) The ecosystem would eventually return to its original state.
(2) The ecosystem would return to its previous state immediately.
(3) The ecosystem would evolve into a new ecosystem that is totally different from the original.
(4) The ecosystem would become an ever-changing environment with no stability.
8. Over a period of time, biotic communities sequentially replace one another on abandoned farmland in the process
known as
(1) gradualism
(2) geographic isolation
(3) ecological succession
(4) replication
9. Stage D in the diagram below is located on land that was once a bare field.
The sequence of stages leading from bare field to stage D best illustrates the process known as
(1) replication
(2) recycling
(3) feedback
(4) succession
10. A greater stability of the biosphere would most likely result from
(1) decreased finite resources
(3) increased biodiversity
(2) increased deforestation
(4) decreased consumer populations
14
11. Ecosystems will have a greater chance of maintaining equilibrium over a long period of time if they have
(1) organisms imported by humans from other environments
(3) a diversity of organisms
(2) a sudden change in climate
(4) predators eliminated from the food chains
12. A sequence of events associated with ecosystem stability is represented below.
sexual reproduction → genetic variation → biodiversity → ecosystem stability
The arrows in this sequence should be read as
(1) leads to
(2) reduces
(3) prevents
(4) simplifies
13. If an ecosystem is changed through a natural disaster, organisms will have the best chance of survival if
(1) their environment has few abiotic factors
(3) the population size is small
(2) the organisms are large
(4) their species exhibits genetic variation
14. The diagrams show various stages of plant development on a volcanic island over a 300 year period after it was
formed.
What is most likely the sequence of the stages of development that occurred on the island over the 300-year
period?
(1) A-B-C-D-E
(2) E-B-D-C-A
(3) A-E-B-D-C
(4) B-D-C-E-A
15. In a pond, which change would most likely lead to terrestrial succcession?
(1) a decrease in the number of suspended particles in the pond water
(2) an increase in the current velocity of the pond water
(3) a decrease in the number of diverse organisms in the shallow water of the pond
(4) an increase in sediment, fallen leaves, and tree limbs accumulating on the bottom of the pond
16. For many decades, certain areas of New York State have remained as hardwood forests containing
predominantly oak and hickory trees. These forested areas will most likely
(1) remain indefinitely and not be affected by environmental influences
(2) reach maturity and change in the near future
(3) be destroyed by environmental changes and never return to their present forms
(4) continue in their present forms unless affected by environmental factors
17. Which condition would cause an ecosystem to become unstable?
(1) only heterotrophic organisms remain after a change in the environment
(2) a slight increase in the number of heterotrophic and autotrophic organisms occurs
(3) a variety of nonliving factors are used by the living factors
(4) biotic and abiotic resources interact
18. In a stable, long-existing community, the establishment of a single species per niche is most directly the result
of
(1) parasitism
(2) interbreeding
(3) competition
(4) overproduction
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Part D: Human Impact on Ecosystems
Natural Resources: Renewable Resources- Food & Soil-
Renewable – can be replaced
Food
 food production has not kept up with population growth in many countries
 development of hybrid strains of corn and rice higher in protein
 better utilization of energy to primary consumer
Soil
 soil is renewable, but slowly
Loss of Soil Fertility
 crop rotation reduces depletion of soil nutrients
o alternating peanuts with cotton: crops are often rotated with legumes in a 3 year cycle
o legume provides nitrogen  nitrates are usable by plants
 addition of fertilizer
Erosion of Soil by Wind
 natural vegetation cover ordinarily holds soil in place
 poor farming methods have stripped soil of natural cover
 drought in 1930’s resulted in exposed topsoil being dried out and blown away on prairies and plains
 farming methods of prevention:
o shelterbelts or wind breaks planted along edges of fields
o irrigation during dry periods stops soil from blowing away
o soil-holding cover crops, instead of leaving soil exposed
Erosion of Soil by Water
 depends on slope of land, amount of rainfall and use of land
 soil exposed on hillsides  rills and gullies  gulches and canyons
 soil lifted by flooding in flat areas  soil dropped in new location
o prevented by planting fibrous root plants that hold soil
o build dams across gullies to slow water speed
 farming methods of prevention:
o contour plowing
o terracing
contour plowing
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terracing
water is held in place &
slows water down
has time to get soaked in
need more methods on top of this to stop erosion
Natural Resources: Non Renewable Resources- Water & Fossil FuelsNon renewable- cannot be replaced
Water
 amount of water in biosphere cannot be increased
Fuel Sources
 falling water, solar, nuclear, tidal, wind, geothermal, etc.



95% of the energy in the US is from fossil fuels
o ex. coal, oil, natural gas
demand exceeds supply
pollutants resulting from burning fossil fuels causing all kinds of problems
Living Resources
 many species in danger of extinction due to human activity
Forest
 prevent floods, conserve water
Wildlife
 fish
o use of fish ladders to allow migration fish to navigate dams
 birds
o loss of habitat causing loss of nesting and feeding sites
o over-hunting caused extinction of many
 small mammals
o habitat destruction
 large mammals
o wholesale killing of bison, white tail deer, black bear, whales, etc.
o game management techniques have limited hunting season and numbers taken
Human Activities and Loss of Diversity


destroy habitats and ecosystems
destroy diversity in both living and nonliving parts of environment
Direct Harvesting
 destruction or removal of species from their habitats
 can lead to extinction of species
o exotic pets/ plants from distant parts of world
o organisms killed to collect specific body part
o poaching - illegally capturing or killing an organism
Habitat Destruction
 people take over land for their own use
 species can become endangered
 entire ecosystem can be damaged and entire species can become extinct
 deforestation- destruction of forests
o provide people with land farming and places to live
o world’s rain forest is as half as large as 150 years ago
 reduction in species = reduction in biodiversity
 ability to find new medicines or new sources of genes is threatened
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Imported Species
 release species from one environment to another
 inadvertent or intentional
o rabbits in Australia from Europe
o Japanese beetle
o gypsy moth
o zebra mussels: Russia to Great Lakes
 eat all the algae
 clog pipes
Review:
1. Which negative human environmental influence is matched to the positive influence that has helped to correct it?
(1) overhunting – pollution controls
(3) importation of organisms – energy conservation
(2) disposal problems – species preservation
(4) pesticide use – biological control of insects
2. Which activity has had the most negative effect on the environment?
(1) recycling of aluminum cans
(3) importation of the gypsy moth
(2) biological control of insect pests
(4) control of air pollution
3. Which activities most directly control erosion?
(1) use of reforestation and covercropping
(2) establishment of game laws and fisheries
(3) use of phosphates and hydrocarbons
(4) establishment of wildlife refuges and national parks
4. When humans use more ground water for industry than is being replaced, the soil above the ground water may
collapse and disrupt natural habitats. This human activity is an example of
(1) species exploitation
(3) a disposal problem
(2) renewal of natural resources
(4) poor use of finite resources
5. Deforestation would most immediately result in
(1) the disappearance of native species
(2) industrialization of an area
(3) the depletion of the ozone shield
(4) global warming
6. The dotted line on the graph represents the potential size of a population based on its reproductive capacity.
The solid line on this graph represents the actual size of the population.
Which statement best explains why the actual population growth is less
than the potential population growth?
(1) Resources in the environment are limited.
(2) More organisms migrated into the population than out of the
population.
(3) The birthrate gradually became greater than the death rate.
(4) The final population size is greater than the carrying capacity.
7. Which practice would most likely deplete a non-renewable natural
resource?
(1) harvesting trees on a tree farm
(2) burning coal to generate electricity in a power plant
(3) restricting water usage during a period of water shortage
(4) building a dam and a power plant to use water to generate electricity
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Pollution of Natural Resources


industrialization - development of economy where machines produce many products
biodegradable vs. non-biodegradable wastes
Water Pollution
 Industrial Sources
o most industrial waste is non-biodegradable
o heavy metals such as lead and mercury are the worst
o contaminates fish and makes them inedible
o PCB’s: very toxic, once they are in they are never removed
o Oil and petroleum products: makes water unfit
o thermal pollution- addition of heat into rivers or lakes
 warm water can’t hold as much O2 = species suffocate

Domestic Sources
o sewage
o detergents
o garbage

Agricultural Sources
o pesticide pollution- used to kill injurious insects, but kill beneficial ones too
o
o
pesticide levels increase at each level of consumer- biological magnification
also washed into water ways and pollute ground water
 ex. DDT
causing endangering of many birds due to egg shell thinning
o
Air Pollution
 Gaseous Pollutants
o most formed when fossil fuels are burned
o acid rain
 Sulfur Dioxide- one of the most deadly
 combines with water to form sulfuric acid
 Nitrogen Oxide- combined with moisture to form nitric acid
 Carbon Monoxide- auto exhaust
 changes the pH levels of rain
 destructive to plants and animals
 Global Warming
o Greenhouse gases in atmosphere trap & absorb infrared radiation and bounce it back to earth
o Global warming- Earth’s average temperature rising
o change in climate patterns & melting of ice caps at North & South Poles
o carbon dioxide is a major greenhouse gas and is released when fossil fuels are burned
 Ozone Depletion
o ozone shield- layer of ozone gas in upper atmosphere
 protects Earth from some of the sun’s radiation
o allows more ultraviolet radiation from the sun to reach the Earth’s surface
o CFC’s: coolants in refrigerators and air conditioners; propellant in aerosol cans; plastic foam
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Review:
1. Fertilizers used to improve lawns and gardens may interfere with the equilibrium of an ecosystem because they
(1) cause mutations in all plants
(3) can be carried into local water supplies
(2) cannot be absorbed by roots
(4) cause atmospheric pollution
2. Car exhaust has been blamed for increasing the amount of carbon dioxide in the air. Some scientists believe this
additional carbon dioxide in the air may cause
(1) global warming
(3) habitat preservation
(2) increased biodiversity
(4) ozone destruction
3. Which factor is not considered by ecologists when they evaluate the impact of human activities on an
ecosystem?
(1) amount of energy released from the Sun
(3) degree of biodiversity
(2) quality of the atmosphere
(4) location of power plants
4. Which human activity is most responsible for the other three human activities?
(1) increasing demand for food
(3) increasing human population
(2) increasing loss of farmland
(4) increasing air pollution
5. Some factories have a negative impact on Earth's ecosystems because they
(1) have high energy demands that require the use of fossil fuels and nuclear fuels
(2) utilize agricultural technology that decreases soil erosion
(3) decrease the need for finite resources
(4) limit the amount of emissions produced each year
6. Which human activity would have the most direct impact on the oxygen-carbon dioxide cycle?
(1) reducing the rate of ecological succession
(2) decreasing the use of water
(3) destroying large forest areas
(4) enforcing laws that prevent the use of leaded gasoline
7. Changes in the chemical composition of the atmosphere that may produce acid rain are most closely associated
with
(1) insects that excrete acids
(3) industrial smoke stack emissions
(2) runoff from acidic soils
(4) flocks of migrating birds
8. Which animal has modified ecosystems more than any other animal and has had the greatest negative impact on
world ecosystems?
(1) gypsy moth
(2) zebra mussel
(3) human
(4) shark
9. The ozone layer of Earth’s atmosphere helps to filter ultraviolet radiation. As the ozone layer is depleted, more
ultraviolet radiation reaches Earth’s surface. This increase in ultraviolet radiation may be harmful because it can
directly cause
(1) photosynthesis to stop in all marine organisms
(2) abnormal migration patterns in waterfowl
(3) mutations in the DNA of organisms
(4) sterility in most species of mammals and birds
10. Imported animal species often disrupt an ecosystem because in their new environment, they will most likely
(1) eliminate the genetic variation of the autotrophs
(2) increase the number of mutations in the herbivores
(3) have no natural enemies
(4) be unable to produce offspring
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Conservation of Natural Resources
 conservation- protection and wise use of natural resources
1. Recycling wastes
2. Conserving available resources
o walk rather than drive
 drive fuel efficient cars
o lower temperature in house
o water, soil, air, living things
o use less water
o use less paper
3. Wildlife Preservation- help endangered species and protect other forms of wildlife
o protected habitats provided by wildlife refuges and national parks
o lawsto regulate overhunting & overfishing
 bisons & egrets increasing in number
4. Biological Controls
o instead of pesticides and herbicides
o sex hormones: pheromones used to attract pests to lure them into traps
o natural predators or parasites: used on Japanese beetle
o breeding pest-resistant plants: resistant to viruses, fungi, and insects
o release sterilized male insects: females produce infertile eggs; screwworms
5. Cleaner Resources
o solar energy over fossil fuels
6. Farming native plants
7. Planting trees to replace those cut down
8. Rotating crops or planting cover crops to reduce soil loss

trade-off - cost and the benefits for a solution
Practice:
1. Human Impact: Human actions can have both a negative or positive impact on the environment.
2. The primary reason humans have a negative impact on the environment is because the human population is
increasing , which places a higher demand on resources such as food, water and space.
3. There are no easy solutions to any ecological problem. Every solution can have BOTH negative and positive
consequences. This is known as a trade off.
4. What is meant by the statement “the Earth has finite resources”?
Our resources will eventually run out.
5. Explain the difference between renewable and nonrenewable resources.
Renewable- gets replaced. Ex: food, trees
Non-Renewable- not replaced as we use it. Ex: Fossil fuels, water
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6. Actions being taken by humans to reduce or repair damage to the environment include:
1. Recycling wastes
2. Conserving available resources
3. Using cleaner resources (ex: solar/wind energy over fossil fuels)
4. Protection of habitats and endangered species
5. Use of biological controls instead of pesticides and herbicides
6. Farming native plants (ex: cocoa in the rainforest)
7. Replanting trees to replace those cut down.
8. Rotating crops or planting cover crops to reduce soil loss.
9. Passing laws to control pollution, land management, hunting, fishing, etc.
7. The increase in the concentration of a poison as we move up the food chain is called biomagnification.
8. How can an understanding of ecology help limit human damage in the environment?
We have greater understanding of how living things interact with each other and the environment.
How have human technologies harmed the ecosystem?
Human Technology
Harmful Influence
What can be done?
-warm water released into
environment
-less oxygen for aquatic life
cool water before it’s released
burning fossil fuels
-global warming
-acid rain
-smog
-recycle
-carpool
-use alternative energy source
Use of chemical fertilizers
water pollution
-use less fertilizers
-crop rotation
Development and industries
around rivers
-air pollution
-water pollution
-emission control devices
-regulate development
water pollution
-use secondary sewage
treatment
-air pollution
-loss of biodiversity
-recycle
-reforestation
-replant trees
-avoid clear cutting
nuclear power
runoff from sewage
Clear cutting and cutting and
burning the rain forest
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Other Problems:
9. Global warming
a) Increasing amounts of carbon dioxide in the atmosphere appears to be causing a warming of the Earth's
atmosphere. This carbon dioxide is coming from increased burning of fossil fuels such as gasoline, coal, and oil.
b) This may be bad because it is changing sea levels and climate patterns.
c) What can be done? use alternative energy sources/ emission control divices
10. Acid Precipitation
a) Sulfur dioxide (also nitrogen oxides) from coal burning sources + rain = acid rain
b) most of the acid rain damaging New York State comes from the Midwest U.S.
c) acid rain kills aquatic life, crumbles buildings, and has many other effects, etc.
d) What can be done? use alternative energy sources
11. Ozone Depletion -- ozone brings about a reduction of UV rays associated with skin cancer
a) our use of chlorofluorocarbons (CFC’s) is destroying the ozone layer
b) CFC sources: some refrigerants & plastics
c) Problems caused by ozone depletion:
i. more cataracts
ii. more skin cancers
12. What is an exotic or invasive species? a species not native to an area
13. Three examples of exotic or non-native invading species in NY: purple loosestrife, zebra mussels, carp
14. List two reasons non-native species may damage the ecosystem.
-out compete native species
-disrupt existing food webs
15. Name two positive aspects of building a large mall in a community and two negative environmental aspects of
such a project.
Positive Aspects
Negative Environmental Aspects
more jobs
increase in traffic = air pollution
more entertainment
destruction of habitat (loss of biodiversity)
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Unit Review:
1. Which group can best be described as a population?
(1) all the honeybees in an orchard
(3) the life in Earth's atmosphere
(2) all the plants and animals in a forest
(4) the living and nonliving factors in a meadow
2. Which is an abiotic factor that functions as a limiting factor for the
autotrophs in the ecosystem shown at the right?
(1) grasshopper
(2) fish
(3) light
(4) hawk
3. The most likely result of a group of squirrels relying on limited resources would be
(1) competition between the squirrels
(3) increased habitats for the squirrels
(2) an increase in the number of squirrels
(4) a greater diversity of food for the squirrels
4. The following chart lists four groups of factors relating to an ecosystem.
Which group contains only abiotic factors?
(1) group A
(2) group B
(3) group C
(4) group D
5. The graph at the right shows the changes in two populations of herbivores in a grassy field. A possible reason
for these changes is that
(1) all of the plant populations in this habitat decreased
(2) population A consumed the members of population B
(3) population A produced more offspring than population B
did
(4) population B competed more successfully for food than
population A did
6. Termites can be found living in dead trees partially buried under soil and stones. Within the tree trunks, the
termites feed on the wood fiber, creating passageways having a high humidity. The wood fiber is digested by
protozoans living within the digestive tract of the termite. What are the biotic factors in this habitat?
(1) soil and humidity
(3) termites and protozoans
(2) humidity, soil, and stones
(4) tree trunk, stones, and protozoans
7. In an attempt to prevent certain species from becoming extinct, humans have
(1) placed all endangered species in zoos
(2) increased the trapping of predators
(3) increased wildlife management and habitat protection
(4) attempted to mate organisms from different species to create new and stronger organisms
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8. The diagram shows organisms in and around a pond.
Which ecological term refers to all the organisms shown in the
diagram?
(1) heterotroph
(2) community
(3) population
(4) biosphere
9. Which group represents a population?
(1) all the vertebrates living in New York State
(3) all the plant and animal species found in New York State
(2) all the flowering plants found in New York State (4) all the Homo sapiens living in New York State
10. A pond community is represented in the diagram. Which term
includes the interactions between the organisms of this community
and the physical factors of their environment?
(1) population
(2) ecosystem
(3) biotic
(4) competition
11. An abiotic component of the biosphere is represented by the
(1) mushrooms in a cave in the Catskill Mountains
(2) population of deer in a forest at the close of the hunting season
(3) annual range of temperatures in a lake in New York State
(4) interactions of insect species in a cornfield
12. An aquarium ecosystem is shown in the accompanying diagram. A
community in this aquarium consists of the
(1) fish, water, and snails
(2) plants and gravel
(3) water and gravel
(4) fish, plants, and snails
13. Which human activity would most likely have a positive impact on the environment?
(1) using pesticides to decrease populations of birds of prey
(2) increasing emissions into the atmosphere to decrease the pH of lakes
(3) using parasites for biological control of pests to increase crop yields
(4) engaging in uncontrolled hunting and trapping to reduce populations of carnivores
14. To minimize negative environmental impact, a community should
(1) approve the weekly spraying of pesticides on the plants in a local park
(2) grant a permit to a chemical manufacturing company to build a factory by one of its lakes, with no
restrictions on waste disposal
(3) make a decision about building a new road in a hiking area based only on the economic advantages
(4) set policy after considering both the risks and benefits involved in building a toxic waste site within its
boundaries
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15. Deforestation would most immediately result in
(1) disappearance of native species
(2) industrialization of an area
(3) depletion of the ozone shield
(4) global warming
16. What is a characteristic of a stable environment?
(1) it usually contains only one type of producer
(2) it usually contains a great diversity of species
(3) it contains simple food chains that have more consumers than producers
(4) it contains complex food webs that have more heterotrophs than autotrophs
16. Which human activity is most responsible for the other three human activities?
(1) increasing demand for food
(3) increasing human population
(2) increasing loss of farm land
(4) increasing air pollution
17. Human impact on the environment is often more dramatic than the impact of most other living things because
humans have a greater
(1) need for water
(3) ability to adapt to change
(2) need for food
(4) ability to alter the environment
18. Which statement best describes one of the stages represented in the diagram below?
(1) The mature forest will most likely be stable over a long period of time.
(2) If all the weeds and grasses are destroyed, the number of carnivores will increase.
(3) As the population of the shrubs increases, it will be held in check by the mature forest community.
(4) The young forest community will invade and take over the mature forest community.
19. Areas with many different niches will most likely have
(1) large numbers of organisms that will become extinct
(2) no organisms that will become extinct
(3) little diversity among the organisms
(4) great diversity among the organisms
20. Which statement concerning ecosystems is correct?
(1) Stable ecosystems that are changed by natural disaster will slowly recover and may again become stable if
left alone for a long period of time.
(2) Competition does not influence the number of organisms that live in ecosystems.
(3) Climatic change is the principal cause of habitat destruction in ecosystems in the last fifty years.
(4) Stable ecosystems, once changed by natural disaster, will never recover and become stable again, even if
left alone for a long period of time.
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21. A pond ecosystem is shown in the diagram.
Which statement describes an interaction that helps maintain the dynamic
equilibrium of this ecosystem?
(1) The frogs make energy available to this ecosystem through the process
of photosynthesis.
(2) The algae directly provide food for both the rotifers and the catfish.
(3) The green-backed heron provides energy for the mosquito larvae.
(4) The catfish population helps control the populations of water boatman
and water fleas.
22. To minimize negative environmental impact, a community should
(1) approve the weekly spraying of pesticides on the plants in a local park
(2) grant a permit to a chemical manufacturing company to build a factory by one of its lakes, with no
restrictions on waste disposal
(3) make a decision about building a new road in a hiking area based only on the economic advantages
(4) set policy after considering both the risks and benefits involved in building a toxic waste site within its
boundaries
23. Which human activity has probably contributed most to the acidification of lakes in the Adirondack region?
(1) passing environmental protection laws
(2) establishing reforestation projects in lumbered areas
(3) burning fossil fuels that produce air pollutants containing sulfur and nitrogen
(4) using pesticides for the control of insects that feed on trees
24. In some areas, foresters plant one tree for every tree they cut. This activity is an example of
(1) lack of management of nonrenewable resources
(2) a good conservation practice for renewable resources
(3) a good conservation practice for nonrenewable resources
(4) lack of concern for renewable natural resources
25. Which statement illustrates how human activities can most directly change the dynamic equilibrium of an
ecosystem?
(1) A hurricane causes a stream to overflow its banks.
(2) Increased wind increases water evaporation from a plant.
(3) Water pollution causes a decrease in fish populations in a river.
(4) The ozone shield helps prevent harmful radiation from reaching the surface of Earth.
26. One way to help provide suitable environments for future generations is to urge individuals to
(1) apply ecological principles when making decisions that will have an environmental impact
(2) control all aspects of natural environments
(3) agree that population controls have no impact on environmental matters
(4) work toward increasing global warming
27. Communities have attempted to control the size of mosquito populations to prevent the spread of certain
diseases such as malaria and encephalitis. Which control method is most likely to cause the least ecological
damage?
(1) draining the swamps where mosquitoes breed
(2) spraying swamps with chemical pesticides to kill mosquitoes
(3) spraying oil over swamps to suffocate mosquito larvae
(4) increasing populations of native fish that feed on mosquito larvae in the swamps
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Short Answers:
1. In certain areas of the United States, the populations of wolves and other predators have decreased. As a
result, deer populations in these areas have increased. Describe one way that an increase in the deer population can
be harmful to humans.
-more accidents
-loss of vegetation
-more diseases getting spread
Base your answer to question 2 on the information and graph below and on your knowledge of biology.
A Closer Look at Cycles in Predator and Prey Populations
Scientists have hypothesized that the populations of both lynx and snowshoe hares should show cyclic changes with
increases in the predator population size lagging behind increases in prey population size, if the assumption is made
that snowshoe hares are eaten only by lynx.
Does this out-of-phase population cycle of predators and prey actually occur in nature? A classic example of such a
cycle was observed by counting all the fur pelts (skins) from northern Canada lynx and snowshoe hares purchased
by the Hudson Bay Company between 1845 and 1935. Population cycles of snowshoe hares and their lynx predators,
based on the number of pelts received by the Hudson Bay Company, are shown in the graph below.
As with any field investigation, many variables could influence the relationship between hare and lynx. One problem
is that hare populations have been shown to fluctuate even without lynx present, possibly because the carrying
capacity of their environment had been exceeded.
To test this hypothesis about population cycles more scientifically, investigators turned to controlled laboratory
studies on populations of small predators and their prey.
2. Identify two variables other than the size of the lynx population that can affect the size of the hare population.
food supply; humans; habitat; diseases; competition; environmental factors; carrying capacity
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3. Two species of microorganisms were placed in the same culture dish, which included basic materials necessary
for life. The size of each population increased during the first three days. After one week, the population size of
one species began to decline each day. State one possible reason for this decline.
competition
Base your answer to question 4 on the energy pyramid and on your knowledge of biology.
4. In a community where grass, cats, insects, and mice are found, which of these organisms would fill level A?
grass
5. The graphs show the relative population size of two closely related species of microorganisms grown under
identical conditions in culture dishes.
In graph A, what causes the population to level off at letter D?
carrying capacity was reached
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6. Ladybugs were introduced as predators into an agricultural area of the United States to reduce the number of
aphids (pests that feed on grain crops). Describe the positive and negative effects of this method of pest control.
Your response must include at least:
 two advantages of this method of pest control
 two possible dangers of using this method of pest control
ADVANTAGES: no chemicals added to the environment with biological controls
more specific than chemicals
DANGERS:
control organism may get over populated
control insect may eat food for others
7. Some people claim that certain carnivores should be destroyed because they kill beneficial animals. Explain why
these carnivores should be protected. Your answer must include information concerning:
 prey population growth
 extinction
 importance of carnivores in an ecosystem

prey population will increase

If too many carnivores are killed, they may become extinct

By eating the herbivores, they keep certain species of plants from being eliminated
8. Identify one process that a producer can accomplish that a carnivore can not accomplish.
photosynthesis
9. Each of the environmental problems listed below has had an impact on ecosystems.
increased ultraviolet radiation
global warming
Select one of these problems and write it in the space below. Explain how this problem has affected an ecosystem.
In your answer, be sure to:
 identify one specific cause of the environmental problem
 identify one organism that has been affected by the problem and state one way that organism has been
affected
 state one action that can be taken to lessen the impact of this problem on the environment
UV radiation

thinning of the ozone shield

humans- more skin cancer

ban CFC’s
Global Warming

increase of carbon dioxide in atmosphere/
deforestation

polar bears- habitat reduced in size

use alternative energy sources/ replant trees
10. Certain insects are kept under control by sterilizing the males with x rays so that sperm production stops.
Explain how this technique reduces the survival of this insect species.
without reproduction no species can survive.
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Use the following passage to answer questions 11-14.
Zebra mussels have caused several major changes in the ecosystem in the Hudson River. Native to Eurasia,
zebra mussels were accidentally imported to the Great Lakes in ships during the late 1980s and first appeared in
the Hudson in 1990.
In regions of the Hudson north of West Point, zebra mussels have depleted the levels of dissolved oxygen
to the point where many native organisms either die or move to other waters. In addition, large amounts of
phytoplankton (small photosynthetic organisms) are consumed by the zebra mussels.
Before the introduction of zebra mussels, one typical food chain in this part of the Hudson was:
phytoplankton → freshwater clams → other consumers
Some long-term changes in the Hudson River ecosystem could be caused by zebra mussels. Base your answer to the
question on the information.
11. State one likely change in the population of each of two different species (other than the zebra mussels) found
in the Hudson.
phytoplankton and freshwater clam populations will decrease
12. Identify one gas in this ecosystem and state how a change in its concentration due to the effects of zebra
mussels would affect organisms other than the zebra mussels.
Oxygen concentration will decrease causing fish & clam populations to decrease
13. State how the death of many of the native organisms could affect the rate of decay and how this would affect
the amount of material being recycled.
rate of decay will decrease
14. Explain why the size of the zebra mussel population would decrease after an initial increase.
limiting factors (food & oxygen)
15. Oak trees in the northeastern United States have survived for hundreds of years, in spite of attacks by native
insects. Recently, the gypsy moth, which has a caterpillar stage that eats leaves, was imported from Europe. The
gypsy moth now has become quite common in New England ecosystems. As a result, many oak trees are being
damaged more seriously than ever before.
State one biological reason that this imported insect is a more serious problem for the trees than other insects
that have been present in the area for hundreds of years.
no natural predators
16. Describe the cycling of carbon in an ecosystem. In your answer be sure to:
 identify the inorganic carbon compound that is obtained by plants from the environment
 identify the process plants use to form more complex organic molecules from this carbon compound
 describe how herbivores use these complex organic molecules
 identify the process herbivores use to return carbon to the environment

carbon dioxide

photosynthesis

source of energy

respiration
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17.
a) Describe some of the relationships in this food web.
In your answer, be sure to:
 identify a carnivore from the food web
 describe the complete path of energy from the Sun to that carnivore
 explain why decomposers are necessary in this food web

wolf; worm; fish

sun  deer  wolves; pond algae  rotifers  worms; pond algae  rotifers  worms  fish

recycle materials in the environment
b) A significant decrease in the wolf population occurs. After a period of one year, what change in the grass
population would most likely be observed?
grass population will decrease
c) A farmer sprayed pesticides on a field next to the pond. Using one or more complete sentences, explain why
several years later the fish population would contain higher pesticide levels than any other pond organisms would
contain.
pond algae takes in pesticide and the pesticides become more concentrated at each succeeding level.
18. Habitat destruction is an environmental problem that affects our own generation and will affect future
generations if it is not solved. Write an essay in which you identify a habitat that is being destroyed and explain
how the destruction of this habitat relates to humans and the overall ecosystem. Your essay must include at least:
 two human activities that contribute to the destruction of this habitat
 three ways the destruction of this habitat has affected plants, humans, and other animals
 two ways to limit further destruction of this habitat
The rainforest is being destroyed by timber logging and by plants being burned to clear the land. These
activities affect organisms by destroying their food supply, breeding grounds, and nesting areas. These
activities also kill predators, leading to rise in some populations. These populations can’t be sustained so they
die. Better farming methods on land already cleared and finding alternatives to wood being harvested could
limit further destruction.
19. Loss of biodiversity is an ecological problem.
Discuss this ecological problem. In your answer be sure to state:
 one human action that may have caused the problem
 one way in which the problem may negatively affect humans
 one positive action that could be taken to reduce the problem



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cutting down forests for farming; destruction of habitat
loss of species; sources of medicine
set up protected areas; restrict logging