Download LECTURE NOTES – CHAPTER 5

LECTURE NOTES – CHAPTER 5
I. Photosynthesis – the process when energy from the sun enters an ecosystem and a
plant uses sunlight to make sugar molecules
A. conducted by plants, algae, & some bacteria
B. requires carbon dioxide and water
C. results in the production of sugars know as carbohydrates
1. energy-rich molecules
2. organisms use to carry out daily activities
3. As organisms consume carbohydrates, energy travels from one to another
organism
D. Formula for photosynthesis:
6CO2 + 6H2O + solar energy
C6H12O6 + 6O2
E. producer – an organism that makes its own food
1. also called autotrophs – self-feeders
2. get energy directly from the sun
a. exception are the deep-ocean organisms that use hydrogen sulfide to make
their own food
F. consumers – organisms that get their energy eating other organisms
1. also called heterotrophs – other feeders
2. get energy indirectly from the sun by eating producers or other consumers
3. Types of consumers:
a. herbivores – consumers that eat only producers; plant-eaters
b. carnivores – consumers that only eat other consumers; flesh-eaters
c. omnivores – consumers that eat both plants & meat; eaters of all
d. decomposers – consumers that eat/break down dead organisms
1) return nutrients in the decayed material to return to soil
2) Examples: bacteria & fungi
II. Cellular respiration – the process of breaking down food to yield energy
A. cells absorb oxygen & use it to release energy from food
B. sugar and oxygen produced during photosynthesis combined
C. results in carbon dioxide, water, & energy
D. Reverse of photosynthesis
E. Formula for cellular respiration:
C6H12O6 + 602
6CO2 + 6H2O + energy
1. energy is used to fuel daily activities
2. energy is used to make more body tissues
3. energy is used to fight diseases
F. excess energy is stored as fat or sugar
G. ALL organism utilize cellular respiration to obtain energy from carbohydrates
III. Energy transfer
A. transfer of energy can be traced as it travels through an ecosystem by three
methods:
1. food chains
2. food webs
3. trophic levels
B. can determine how the energy is transferred
C. can determine how much energy is transferred
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D. can tell which organisms depend on other organisms to survive
E. food chains – a sequence in which energy is transferred from one organism to the
next as each organism eats another
F. food webs – shows many feeding relationships that are possible in an ecosystem
1. multiple food chains linked together
2. each ecosystem contains more species than a single food chain contains
3. most organisms eat more than one kind of food
G. trophic levels – each step in the transfer of energy through a food chain or food
web
1. each time energy is transferred from one organism to another, some energy is
lost as heat
2. less energy is available to the next trophic level
3. some energy is lost during cellular respiration
4. about 90% of energy is used at each trophic level for body functions
5. about 10% of energy is stored in the organism’s body
a. this percentage is all that is available to the next trophic level
6. Energy pyramids – demonstrates the loss of energy from one trophic level to
another
a. each layer of pyramid represents one trophic level
b. producers form the base of pyramid which is the lowest trophic level
1) contains the most energy
c. herbivores make up second level
1) contains less energy than base
d. carnivores that feed on herbivores make third level
e. carnivores that feed on other carnivores make up top level
1) store less energy than lower levels
2) fewer organisms at higher levels
3) because of energy loss, ecosystems usually have only four or five trophic
levels
a) not enough energy left to support higher levels
b) organisms that feed on top level are usually small and need little
energy; Example: parasitic worms & fleas
IV. The Carbon Cycle – the process by which carbon is cycled between the atmosphere,
land, water, and organisms
A. carbon makes up proteins, fats, & carbohydrates which make up organisms
B. Short-term cycle
1. Carbon enters ecosystems when producers convert atmospheric CO2 into
carbohydrates
2. Consumers obtain carbon when they eat producers
a. when consumers break down food during cellular respiration, some
carbon is released into atmosphere as CO2
b. Producers also release CO2 during cellular respiration
C. Long-term cycle
1. Begins like short-term cycle
2. some carbon is converted into carbonates
a. make up hard parts of bones & shell
b. do not break down easily
c. over million of years, creates formations of limestone rock
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1) limestone is one of largest carbon sinks or carbon reservoirs
3. some carbon is converted into fats, oils, & other molecules that store energy
a. carbon is released into the soil or water from molecules when organism dies
b. released molecules can form deposits of fossil fuels (coal, oil, and natural
gas) underground
1) fossil fuels are stored carbon left from bodies of plants & animals that
died millions of years ago
D. Human affect on carbon cycle
1. burning fossil fuels releases carbon into atmosphere as carbon dioxide
2. cars, factories, & power plants burn fossil fuels
a. In 2000, 1/3 of carbon dioxide emitted in US was from vehicles
3. 6 billion metric tons of carbon per year are released as carbon dioxide
a. about half remains in the atmosphere
1) over the years, amount has steadily increased
2) may contribute to global warming – overall increase in the temperature
of Earth
b. Over a billion metric tons of carbon dioxide dissolves into oceans (a carbon
sink)
c. Plants absorb remaining carbon dioxide
V. The Nitrogen Cycle – a process in which nitrogen is cycled between the atmosphere,
bacteria, an other organisms
A. all organisms need nitrogen to build proteins
1. proteins are used to build new cells
B. Nitrogen makes up 78% of gases in atmosphere
1. most organisms cannot use atmospheric nitrogen
2. it must be altered or “fixed” before organisms can utilize it
C. nitrogen-fixing bacteria – the only organisms that can fix atmospheric nitrogen
into chemical compounds
1. all other organisms depend on these bacteria to supply nitrogen
2 .bacteria live within nodules of roots of plants called legumes
a. include peas, beans, & clover
b. bacteria use sugars made by legumes to produce nitrogen-containing
compounds such as nitrates
c. excess nitrogen fixed by bacteria is released into soil
d. some bacteria actually live within soil
1. plants that do not have nitrogen-fixing bacteria in roots get nitrogen
from soil
D. animals get nitrogen from consuming plants or other animals
E. Decomposers – bacteria break down dead plants and animals which release
nitrogen back into atmosphere
1. only a small amount is returned to atmosphere
2. most nitrogen stays within ecosystem once it enters it
a. cycles between organisms and the soil & is constantly reused
VI. The Phosphorus Cycle – the movement of phosphorus from the environment to
organisms & back to environment
A. does not occur in atmosphere because phosphorus is rarely a gas
B. phosphorus is part of many molecules that make up cells
1. essential for formation of bones & teeth in animals
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C. Plants get phosphorus from soil
D. animals get phosphorus from eating plants or other animals
E. How phosphorus enters soil & water; several ways
1. erosion of rocks
a. small amount dissolves as phosphates
b. plants absorb phosphates through soil
2. excretion of wastes
3. decomposition of organisms
4. some washes off land & ends up in ocean
a. many phosphate salts are not soluble in water
1) accumulate as sediment
VII. Effects of fertilizers on nitrogen & phosphorus cycles
A. Fertilizers contain both nitrogen & phosphorus
B. Used to stimulate & maximize plant growth
C. If excessive, can enter ecosystems through run-off
1. excess in aquatic ecosystems can cause rapid & over-abundant growth of
algae
a. results in algal bloom
1) dense visible patch of algae near surface of water
2) can deplete ecosystem of important nutrients such as oxygen
VIII. Acid Precipitation – combination of nitric acid in rain or snow
A. Burning fuel (coal, wood, or oil) releases nitric oxide into atmosphere
B. Nitric oxide is harmful
C. When released into atmosphere, combines with oxygen & water vapor to form
nitric acid which creates acid precipitation
IX. Ecological succession – a gradual process of change & replacement of the types of
species in a community
A. may take hundreds or thousands of years
B. each new community that forms makes it harder for previous community to
survive
C. Primary succession – a type of succession that occurs on a surface where no
ecosystem exited before
1. occurs on rocks, cliffs, & sand dunes
2. Pioneer species – first organisms to colonize any newly available area &
begin ecological succession
a. make new area habitable for other species
1) break down rocks to create soil
2) larger plants then grow in newly created soil
b. lichens & bacteria
3. takes several hundred to thousands of years to produce fertile soil
D. Secondary succession- occurs on a surface where an ecosystem has previously
existed
1. more common type of succession
2. occur in ecosystems that have been disturbed or disrupted by humans,
animals, or natural disasters
3. natural fires caused by lightning is a necessary part of secondary succession
a. some plant species release seeds after exposure to intense heat
b. remove accumulations of brush & deadwood
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c. some animals feed only on new plant sprouts that appear after fire
d. foresters allow some natural fires to burn unless they are a threat
4. Old-field succession – a type of secondary succession which occurs when
farmland is abandoned
a. takes about 50 years to return to community before farming
E. Climax community – a final, stable community
1. continues to change in small ways, but essentially remains the same unless
disturbed
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