Chapter 2: Principles of Ecology

Chapter 18:Ecology Notes
Ecology
Study of interactions that take place between organisms and their environments
Living things are affected by nonliving and living parts of the environment
Abiotic factors: nonliving parts of the environment
o Air, temperature, moisture, light, soil
Biotic factors: living organisms in the environment
o Producers: Organisms that take in energy from their surroundings to make their own food
(Plants and some bacteria)
o Consumers: Organisms that eat (consume) other organisms for energy (animals)
o Decomposers: Consumers that eat waste products for energy. Waste products are feces,
urine, fallen leaves, dead animals. (Fungi, some bacteria)
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Ecology studies the relationship of organisms and their environment on several levels
Organism
Population: group of organisms, all of the same species, which interbreed and live in the
same area at the same time
o Organisms may compete with each other for resources such as food, water, space, mates, etc.
Biological community: group of populations that live in the same area at the same time
o A change in one population can cause a change in another population
Ecosystem: a biological community and the nonliving things in the community’s environment
o Terrestrial ecosystem: located on land
o Aquatic ecosystem: located in water
Biosphere: portion of the Earth that supports living things
o Air, land, fresh water, salt water

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Habitat
the place where an organism lives out its life
Niche: all the strategies and adaptations a species uses in its environment
o Includes all its interactions with the biotic and abiotic parts of the environment
o Each type of organism occupies its own niche to avoid competition with other types of
organisms
Two species can share the same habitat but not the same niche
o Example: Ants and bacteria both live in the dirt (habitat) but have different niches.
Ants eat dead insects and bacteria eat dead leaves, dead logs, and animal waste. So
ants and bacteria don’t compete for resources.
Survival relationships
Predator-prey: predators are consumers that hunt and eat other organisms called prey
Symbiosis: relationship in which one species lives on, in, or near another species and
affects its survival
o There are 3 types of symbiosis
1. Mutualism: type of symbiosis in which both species benefit
‣ Ants living in the tropical acacia trees- trees are protected when ants attack
animals that try to feed on the tree and ants receive nectar and shelter from the
tree.
2. Commensalism: type of symbiosis in which one species benefits and the other species
is neither harmed nor benefited
‣ Spanish moss grows on the branches of trees. The moss gets a habitat and the
tree gets nothing.
3. Parasitism: type of symbiosis in which one species benefits and the other species is
harmed
‣ Parasite: organism that harms but does not kill another organism
‣ Host: organism that is harmed by a parasite
‣ Ticks feed on dogs, people, etc. The ticks get food (blood) and the hosts lose
blood and can be infected with disease.
Feeding relationships
Autotrophs: Organisms that make their own food (plants and some bacteria)
Heterotrophs: Organisms that cannot make their own food and must eat other organisms
o Herbivores: eat plants (cows)
o Carnivores: eat meat (wolves)
o Omnivoes: eat plants and meat (humans)

Bacteria
Food Chains
Trophic levels and food chains
• Trophic level: A feeding level in an ecosystem
• Food chain: lineup of organisms that shows who eats who
o Shows how matter and energy move through an ecosystem
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Eaten
by
1 st trophic level:
producers
(make their own
food)
Eaten
by
2 nd trophic
level: primary
consumer
(eats plants)
3 rd trophic
level: secondary
consumer (eats
meat)
Eaten
by
4 th trophic
level: tertiary
consumer (eats
meat)
Eaten
by
Last trophic
level:
decomposer
(eats dead
animals)

Energy pyramid
• Every time an organism eats, it obtains energy from its food
• So energy is transferred from the 1 st trophic level to the 2 nd trophic level to the 3 rd
trophic level and so on.
• Some of this energy is lost along the way during an organism’s metabolism and as heat
• Energy pyramid: picture showing how much energy is transferred to the different
trophic levels in a food chain
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Trophic Level
4 th
Tertiary
consumers
Energy Available
10 kcal/m 2 /year
2 nd
Primary
consumers
1 st
Producers
3 rd
Secondary
consumers
100 kcal/m 2 /year
1000 kcal/m 2 /year
10,000
kcal/m 2 /year

Food web
• A network of connected food chains
• More realistic than a food chain because most organisms feed on more than one
species for food
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Limiting Factors
There is only a limited amount of resources (water, oxygen, nitrogen, carbon) on the earth
Carrying capacity – number of organisms of 1 species that an environment can support
Populations increase below the carrying capacity
Population decrease above the carrying capacity
Limits of the environment
Reproductive patterns
Example: Mosquitoes reproduce rapidly, and Elephants reproduce very slowly
Density Dependent Factors – the more dense, the more it spreads
o Disease – spreads in a tighter community
o Competition – more people, the more competition
o Parasites
o Food
Density Independent Factors – affect all populations regardless of their density
o temperature
o storms
o floods
o drought
o habitat disruption
o pollution
Predation – when predators eat the prey, the prey decreases, but can this decrease the
predator population as well?
Crowding – when populations become crowded, stress of the animal increases, it can
become very aggressive, decrease its parental care, decrease its fertility, and resistance
to disease decreases

Ch. 18 Notes-Part II
Succession
What is succession? Changes over time. Succession can occur in decades or even centuries.
It can take a really long time.
If you didn’t cut the grass, what would happen to it?
1) It would grow larger
2) Weeds would start to grow
3) The area will look like a meadow
4) Bushes will grow
5) Trees will appear
6) Less light will reach the ground b/c
of the trees
7) The grass will slowly disappear
8) The area will become a forest
Stages of succession
1) Primary succession – colonization of new sites by organisms
Example) Lava from a volcano, an avalanche makes new territory for organisms
2) Climax Community – A stable, mature community that undergoes little or no change in
species
3) Secondary succession – sequence of community changes that takes place after a
community is disrupted by natural disasters or human actions (occurs in areas that
previously contained life, and on land that contains soil)
Example) Forest fire, hurricanes, farmers abandon a field, a building is demolished
BIOLOGICAL DIVERSITY & CONSERVATION
Biodiversity – variety of life in an area (More biodiversity in the warmer environments)
Threatened species-Endangered species-Extinct species
Threats to Biodiversity
1) Habitat loss – when rainforests and coral reefs are wiped out
2) Habitat fragmentation – separation of wilderness areas from other wilderness areas
(like islands)
3) Edge effect – when climate is changed along the edge of an ecosystem
4) Habitat degradation – damage to a habitat by pollution
5) Introduction of exotic animals – introducing a new species into an ecosystem
Conservation biology – new field that studies method and implements plans to protect
biodiversity
How to conserve
1) Legal protection – no one can hunt or kill any animal on the endangered species list
2) Preserving habitats – installing national parks
3) Reintroduction programs – bringing species back to where they once lived
4) Captivity – people holding onto organisms in a zoo
Cycles in nature
There is only a limited amount of resources (water, oxygen, nitrogen, carbon) on the earth
In order to keep these resources available to organisms, they must be recycled after they
are used
Cycle: a process that recycles a resource so that you end up with what you started with
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Nitrogen Cycle
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1. Nitrogen fixation: Bacteria in the
ground change nitrogen from the
atmosphere (N 2 ) to different nitrogen
compounds
5. Denitrification: Bacteria change the
nitrogen compounds back to N 2 and
release it to the atmosphere
2. These bacteria live in plants and
transfer the nitrogen compounds to the
plants
4. Bacteria eat the dead animals and
animal waste and take in the nitrogen
compounds
3. Animals eat the plants and take in the
nitrogen compounds
Bacteria change nitrogen compounds
back to nitrogen and release it into
the atmosphere
Bacteria eat
dead animals
Nitrogen in
atmosphere
Bacteria in roots change
nitrogen to nitrogen
compounds

Water Cycle
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2. Seepage: Water
seeps into the
ground and plants
use it
3. Transpiration:
Plants give off
water to the
atmosphere
1. Precipitation: Rain and snow fall from
the atmosphere to the earth
2. Runoff: Extra
water runs off the
land to lower-lying
bodies of water
3. Evaporation of
water from the
bodies of water
back into the
atmosphere

Oxygen-Carbon Cycle
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1. Carbon dioxide (CO 2 )
and oxygen (O 2 ) are
found in the atmosphere
2. Plants use CO 2 to
make their own food
(photosynthesis)
2. Animals and plants
use the O 2 to make
energy (respiration)
3. During photosynthesis,
plants release O 2 back into the
atmosphere
3. During respiration, animals
and plants release CO 2 back
into the atmosphere