First six weeks
First Six Weeks Review Guide
“Analyze factors responsible for the changes associated with biological succession.”
Changes that occur in an ecosystem are called ecological succession.
There are 2 types: If you start off on land that has NO SOIL (never had any growth on it before), that’s called
primary succession. If growth begins on land that HAS SOIL it is called secondary succession.
Examples of Primary Succession are:
 Growth on cooled lava from a volcano
 Abandoned parking lot or sidewalk cracks
 Rocks
 Glaciers melting
The first type of growth on primary succession is called the pioneer species (because they are the
first). Examples of pioneer species are mosses and lichens. Lichens and weather break down the rock into
rubble. When the lichens die, it adds nutrients and you have SOIL!! Growth continues then with grasses, then
bushes, then small trees and finally with big trees. After the big trees are established, the area is called a
climax community.
Examples of Secondary Succession are:
 Growth after a forest fire, tornado, or any natural disaster (not volcanoes though!)
 Abandoned farm field
“Interpret a diagram that illustrates energy flow in an ecosystem.”
“Predict how population changes of organisms at different trophic levels affect an ecosystem.”
Energy flows thru an ecosystem. IT CAN NOT BE CREATED OR DESTROYED. IT IS ALWAYS RECYCLED!
We use a triangle shape to represent the way
energy flows thru an ecosystem, because energy
decreases as you go up the levels and released as heat.
This is why it is a TRIANGLE SHAPE.
90% is released as heat. 10% is available for the next level.
The triangle is called an energy pyramid
and is shown to the right.
A trophic level is a FEEDING LEVEL. The bottom of the pyramid is trophic level I. Above that is trophic level
II. Above that is trophic level III and above that is trophic level IV.
1. Trophic Level I – located at the bottom of an energy pyramid. Strictly plants. Feed on the SUN. Plants
make their own food SO WE CALL THEM autotrophs or producers. “P” for PLANTS. “P” for
PRODUCERS.
2. Trophic Level II – Strictly herbivores (plant eaters). Feed on trophic level I. Also called PRIMARY
CONSUMERS because they are the FIRST CONSUMERS ON THE PYRAMID.
3. Trophic Level III – Strictly carnivores (meat eaters) and omnivores (both meat and plant). Feed on
trophic level II and I. Also called SECONDARY CONSUMERS because they are the SECOND
CONSUMERS ON THE PYRAMID.
4. Trophic Level IV – Strictly carnivores and omnivores again. These are your top predators. They are
TERTIARY CONSUMERS because they are the THIRD CONSUMERS ON THE PYRAMID. Feed on
trophic level III, II and I.
Other Vocabulary to Remember:
Decomposers work on ALL LEVELS because they break down dead materials and return nutrients to the
earth. (examples: earthworms, bacteria, fungus)
Detritvores work on ALL LEVELS because they eat dead things. They do NOT return nutrients to the earth
though (example: Vulcher) – can NOT make their own food
Heterotroph – “Consumers” eat other organisms
Autotroph – “Producers” make their food using the sun (plants only)
A food chain shows one feeding relationship. It shows who eats who. The arrows
always point to the FLOW OF ENERGY or who is GAINING THE ENERGY.
For example, looking that the food chain at the right, the energy from the leaves
will enter the slug’s stomach. The energy from the slug will flow into the frog’s stomach.
A food web shows many feeding relationships
& is made of many food chains like the one below:
Be able to PREDICT what will happen if you manipulate the food chain or
web. Increase the blossoms…the bees will also increase because their
food source has increased. So will the bears.
Another example is if the deer decrease, then the nuts will increase due
to less predators. However, wolves will decrease because there is less
food (deer for them).
Life is organized in the following way:
1st) Species – an organism that can interbreed and produce fertile offspring. (a deer)
2nd) Population – organisms of the same species. (many deer)
3rd) Community – different species living together. (deer, wolves, insects, plants, mice, etc.)
4th) Ecosystem – all the living (biotic) and non-living (abiotic) factors (rain, temp, rock, etc.)
“Interpret the relationship between environmental factors and fluctuations in population size.
Determine how the carrying capacity of an ecosystem is affected by interactions among organisms”.




Emigration – when an individual leaves a population
Immigration – when an individual enters a population
Population Density – refers to how close individuals live to one another. For example, farms out in
the country have a low population density, compared to people living in downtown Chicago would have
high population density.
Limiting Factors – Things that limit a population size; there are two types of limiting factors…
1. Density – Dependent Factors: these factors depend on how close organisms live to one another.
For example, competition, space, disease, predators
2. Density – Independent Factors: these factors do NOT depend on how close organisms live to
one another. For example, weather, natural disasters and human activities.
Organisms grow exponentially –
this means the rate is always increasing.
For example, looking at the image to the right,
one multiplies to 2… 2 multiplies to 4…
4 multiplies to 8… 8 multiplies to 16… etc.
Exponential growth makes a “J” shaped curve.
A population CAN NOT GROW FOREVER. It eventually will run out of space, food, etc.
Limiting factors stop a population from growing forever. These factors bring a population to its maximum
number it can hold creating an “S” shape graph. That maximum number of organisms an environment can
hold is called CARRYING CAPACITY.
Carrying Capacity – IS A NUMBER.
You find it on the y-axis on a graph like
the graph to the right.
Like an elevator or restaurant says
“carrying capacity – 25 people or 2500 people.”
Be able to PREDICT if the carrying capacity (C.C)
will increase or decrease if you:
 Increase the predators – C.C will decrease
 Increase disease – C.C. will decrease
 Increase the food supply – C.C. will increase
 Decrease the food supply – C.C. will decrease
 Increase the space – C.C. will increase
Etc.
“Predict how various types of human activities affect the environment.”
“Make inferences about how a specific environmental change can affect the amount of biodiversity.”
“Predict how a specific environmental change may lead to the extinction of a particular species.”
Biodiversity – refers to all the different kinds of life there is; the tropical rainforest has the highest amount
of biodiversity where as a cornfield has the lowest amount.



Threatened Species – refers to a species that is in danger of becoming endangered
Endangered Species – refers to a species of animal that is in danger of extinction because of low
population numbers
Extinct – a species that no longer exists (cannot be brought back- ex. Dinosaurs )
Threats to Biodiversity:
#1 HABITAT LOSS – animals losing their homes (THIS IS THE NUMBER 1 THREAT!!)
#2 POLLUTION
#3 INVASIVE OR EXOTIC SPECIES
#1 Habitat Loss examples:
 Deforestation
 Fragmentation – chopping up land into smaller pieces
 Coral Bleaching
 Construction of homes, businesses
#2 Pollution: 3 types: Land, Air, Water
Land
Pesticides – kill insects and pests that eat vegetation. This falls onto land and works its way up the food chain.
Herbivores eat the plants with pesticide. Carnivores eat the herbivores. The pesticide accumulates as it moves
up the food chain and causes health problems in animals. This leads to a decrease in biodiversity. (Example:
Bald Eagle and cracking egg shells due to pesticide accumulation)
Air
Ozone Depletion – Chemicals like CFC’s chip away at the
ozone layer creating a hole that lets in more UV rays.
This can melt polar ice caps and cause a decrease
in biodiversity. See image at right.
Acid Rain – Automobile and factory exhaust combine with
water vapor in the air and falls down as “acid rain” damaging
plant tissue and leaching nutrients in the soil away from plants.
Global Warming – burning fossil fuels (coal, oil, natural gas)
puts more carbon dioxide in the air. Carbon dioxide blocks
heat from escaping into space. This warms up our planet
more than we need and causes environmental
problems that lead to loss in biodiversity. See image at right.
Problems: increasing ocean levels, flooding, draughts,
worse natural disasters, habitat loss
Water
Fertilizers - loaded in Nitrogen to help plants grow. Rain carries fertilizers off into nearby lakes and ponds.
Algae love fertilizer and grow out of control. This is called an ALGAL BLOOM. Algae are producers, however,
they take in oxygen instead of carbon dioxide. CAUSES FISH TO SUFFOCATE DUE TO LOSS OF OXYGEN.
Other Vocabulary to Remember:
 Pollutant – harms an environment / usually created by humans
 Renewable resources – examples are wind, water, solar
 Non-Renewable resources – cannot be replaced! Examples are all the fossil fuels (oil, natural gas
and coal)
 Sustainability - means the ability to survive; we want to use our resources yet be able to continue on
living, not damaging the planet.
#3 Invasive or Exotic Species – species that DO NOT belong in an area.
 These species have no natural predators so they grow exponentially and eat up all the food.
 Causes other species that are native to the area to have to compete for food and space.
 Native species can drop in numbers and possibly become endangered or extinct. LOSS OF
BIODIVERSITY.
Preventing Biodiversity Loss:
1. LAWS!! Fishing and hunting laws protect animals and plants so they do not become endangered or
extinct.
2. Zoos and Captivity – breed animals and re-release them into the wild
3. Parks and Preserves – like Yellowstone National Park and local nature preserves
“Predict how changes in biogeochemical cycles can affect an ecosystem.”
The Carbon Cycle:
Enters the Ecosystem:
 Burning of Fossil Fuels (coal, oil, natural gas)
 Respiration by animals
 Volcanoes
 Open burning
 Decay and death of animals and plants
Leaves the Ecosystem:
 Photosynthesis (plants take in carbon dioxide)
Nitrogen Cycle:
Enters the Ecosystem:
 Fertilizers
 Nitrogen-Fixing bacteria fix gas nitrogen in the air into
 a form so plants can use
 Death and decay of plants and animals
Leaves the Ecosystem:
 De-nitrifying bacteria put nitrogen used by plants
back into the air
Water Cycle:
Enters the Ecosystem:


Precipitation – gas to liquid; rain / snow
Condensation – gas to liquid; on the outside of a drinking glass
Leaves the Ecosystem:
 Transpiration – liquid to gas, specifically water released by plants
from pores in their leaves
 Evaporation – liquid to a gas
Phosphorus Cycle:
Enters the Ecosystem:


Rock containing phosphorus weathers away and is washed
Into nearby lakes, rivers, streams, oceans, etc.
Plants and animals containing phosphorus decompose
Leaves the Ecosystem:

Phosphorus in bodies of water settles to the ground and
turns into bedrock. Millions of years later it is exposed again
and weathers back into lakes, rivers, etc.
For ALL NUTRIENT CYCLES...
Be able to understand that if you increase or decrease carbon, water, nitrogen, or
phosphorus…what will that do to the cycle and the entire ecosystem?
For example, which nutrient cycle could put more oxygen in the atmosphere? Answer: Carbon Cycle
Why? Because plants take in carbon dioxide and put out OXYGEN. If you increase the plants, you
increase the oxygen content in the atmosphere and decrease the carbon dioxide content.