CHAPTER 3 REVIEW
By: Geoffrey Powers
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1. Atmosphere is a thin layer of gases surrounding earth’s surface. The
atmosphere consists of several layers of gas:
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Troposphere - The troposphere is the lowest layer of Earth's atmosphere. It extends from
Earth's surface to an average height of about 12 km, although this altitude actually varies
from about 9 km (30,000 ft) at the poles to 17 km (56,000 ft) at the equator with some
variation due to weather.
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2. The stratosphere is the second-lowest layer of Earth's atmosphere. It lies above the
troposphere and is separated from it by the tropopause. This layer extends from the top of the
troposphere at roughly 12 km (7.5 mi; 39,000 ft) above Earth's surface to the stratopause at an
altitude of about 50 to 55 km (31 to 34 mi; 164,000 to 180,000 ft) It contains the ozone layer,
which is the part of Earth's atmosphere that contains relatively high concentrations of that gas.
This rise in temperature is caused by the absorption of ultraviolet radiation (UV) radiation from
the Sun by the ozone layer, which restricts turbulence and mixing.
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Hydrosphere - The hydrosphere is the liquid water component of the Earth. It includes the
oceans, seas, lakes, ponds, rivers and streams. The hydrosphere covers about 70% of the
surface of the Earth and is the home for many plants and animals. The hydrosphere is always
in motion.
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Biosphere - The biosphere is the global sum of all ecosystems. The biosphere covers the
whole terrestrial ecosystem, to the ocean depths and onto an area above six kilometers to the
above sea level.
SECTION 1
THREE FACTORS SUSTAIN THE EARTH’S LIFE
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The one-way flow of high-quality and energy from the sun - The sun warms the planet, drives
the hydrologic cycle and makes life on Earth possible. The amount of sunlight received on
Earth's surface is affected by the reflectivity of the surface, the angle of the sun, the output of
the sun, and the cyclic variations of Earth's orbit around the sun. Essentially 100% of the
energy that fuels the earth comes from the sun. To maintain a constant global average
temperature, all of the sun’s radiation that enters Earth’s atmosphere must eventually be sent
back to space. This is achieved through Earth’s energy balance.
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Cycling of nutrients - the nutrient cycle is a concept that describes how nutrients move from the
physical environment into living organisms and subsequently are recycled back to the physical
environment. This circular movement of nutrients is essential to any given ecosystem, and it
must be balanced and stable for the system to be maintained. In many cases, human activities
have had a major impact on these processes, resulting in adverse effects. There are many
different nutrient cycles, each with its own particular pathways, but perhaps the most important
are those involving the elements carbon, oxygen, nitrogen, and phosphorous.
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Gravity - this allows Earth to maintain its atmosphere that allows the mobilization and cycling of
chemicals through air, water, soil, and organisms.
NATURAL GREENHOUSE EFFECT- HE GREENHOUSE EFFECT IS A NATURAL PROCESS THAT WARMS THE EARTH’S
SURFACE. WHEN THE SUN’S ENERGY REACHES THE EARTH’S ATMOSPHERE, S OME OF IT IS REFLECTED BACK TO
SPACE AND THE REST IS ABSORBED AND RE-RADIATED BY GREENHOUSE GASES.
GREENHOUSE GASES INCLUDE WATER VAPOR, CARBON DIOXIDE, METHANE, NITROUS OXIDE, OZONE AND SOME
ARTIFICIAL CHEMICALS SUCH AS CHLOROFLUOROCARBONS (CFCS).
THE ABSORBED ENERGY WARMS THE ATMOSPHERE AND THE SURFACE OF THE EARTH. THIS PROCESS
MAINTAINS THE EARTH’S TEMPERATURE AT AROUND 33 DEGREES CELSIUS WARMER THAN IT WOULD OTHERWISE
BE, ALLOWING LIFE ON EARTH TO EXIST.
SECTION 2
ECOSYSTEMS HAVE LIVING AND NONLIVING
COMPONENTS
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The biosphere and the ecosystems in it are made up of biotic (living) and non-biotic (nonliving) parts. Non-living
parts would be air, soil, water, or rocks. Living components would be animals, plants, or microbes.
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Ecology is the focus on science of interactions between organisms in nature.
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Ecologists assign each organism to a trophic or feeding level which is determined by its source of food and
nutrients.
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Ecosystem-Parts of the earth's air, water, and soil where life is found
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Community-A community of different species interacting with one another and with their nonliving environment of matter and energy
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Population-A group of individuals of the same species living in a particular place
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Organism- An individual living being
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Cell-The fundamental structural and functional unit of life
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Molecule-Chemical combination of two or more atoms of the same or different elements
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Atom-Smallest unit of a chemical element that exhibits its chemical properties
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Photosynthesis - the process by which green plants and some other organisms use
sunlight to synthesize foods from carbon dioxide and water. Photosynthesis in plants
generally involves the green pigment chlorophyll and generates oxygen as a byproduct.
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Chemosynthesis- the synthesis of organic compounds by bacteria or other living organisms using energy
derived from reactions involving inorganic chemicals, typically in the absence of sunlight.
DIAGRAM OF TROPHER LEVELS
SECTION 3
ENERGY IN FOOD WEBS
• Food Chain - an arrangement of the organisms of an ecological
community according to the order of predation in which each uses the
next usually lower member as a food source.
• Food Web - a system of interconnected and interdependent food
chains. It can also be defined as a network of food relationships
through which nutrients and energy are passed from one living
organism to another.
• Biomass - the total mass of living matter in a given habitat or per unit
area of a habitat.
• Pyramid of energy flow - a graphical representation used for showing
the biomass or productivity at each tropical level in a given ecosystem.
There are four parts of the energy pyramid. They start from the bottom
and go up. It goes from primary producers, primary consumers,
secondary consumers, and tertiary consumers.
SOME ECOSYSTEMS PRODUCE PLANT MATTER FASTER THAN OTHERS DO
• Gross primary productivity-consists of the amount of light energy
that is converted to chemical energy by photosynthesis per unit
of time.
• Net primary productivity-The rate at which an ecosystem
accumulates energy or biomass, excluding the energy it uses for
the process of respiration.
SECTION 4
NUTRIENT CYCLES
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Nutrients are in continuous motion air, water, soil, and rock through a series of processes
known as biogeochemical cycles or nutrient cycles.
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The Water Cycle - Plants absorb water from soil, and animals drink water or eat animals, which
are made mostly of water. When plants go through the process of transpiration (that's when
water evaporates from a leaf and more water is pulled up from the roots of the plant and out
through the cells on the surface of the leaf), they give off water. When animals create
perspiration, they release water, which is evaporated into the atmosphere. Water also is
released from plants and animals as they decompose. Decomposing tissue becomes
dehydrated, which is what causes the dried-out tissues to break down and fall off into the soil.
As water evaporates into the air, wind moves air over bodies of water, and precipitation (rain,
snow, sleet, hail) releases water into larger bodies of water such as lakes, rivers, oceans, and
even glaciers. Water from precipitation and decomposing tissue also gets into groundwater,
which ultimately supplies larger bodies of water. (Never Ends)
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Carbon Cycle - Plants take in carbon dioxide for photosynthesis. Animals consume plants or
other animals, and all living things contain carbon. Carbon is what makes organic molecules
organic (living). Carbon is necessary for the creation of molecules such as carbohydrates,
proteins, and fats. Plants release carbon dioxide when they decompose. Animals release
carbon dioxide when they decompose or respire. (Animals take in oxygen and release carbon
dioxide when they breathe.) Carbon dioxide also is released when organic matter such as
wood, leaves, coal, or oil are burned. The carbon dioxide returns to the atmosphere, where it
can be taken in by more plants that are then consumed by animals. Decomposing animals and
plants leach carbon into the ground, forming fossil fuels such as coal or oil. Peat also forms
from the decomposition of organic matter. Some carbon is stored in the form of cellulose in the
wood of trees and bushes.
NUTRIENT CYCLES
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Nitrogen cycle - Because amino acids build proteins, nitrogen is pretty important. Nitrogen also is present in
the nucleic acids DNA and RNA. Life could not go on without nitrogen. The nitrogen cycle is the most
complex biogeochemical cycle because nitrogen can exist in several different forms. Nitrogen fixation,
nitrification, denitrification, and ammonification are all parts of the nitrogen cycle .
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Phosphorous cycle - Phosphorus enters the environment from rocks or deposits laid down on the earth
many years ago. The phosphate rock is commercially available form is called apatite. Other deposits may
be from fossilized bone or bird droppings called guano. Weathering and erosion of rocks gradually releases
phosphorus as phosphate ions which are soluble in water. Land plants need phosphate as a fertilizer or
nutrient. Phosphate is incorporated into many molecules essential for life such as ATP, adenosine
triphosphate, which is important in the storage and use of energy. It is also in the backbone of DNA and
RNA which is involved with coding for genetics. When plant materials and waste products decay through
bacterial action, the phosphate is released and returned to the environment for reuse.Much of the
phosphate eventually is washed into the water from erosion and leaching. Again water plants and algae
utilize the phosphate as a nutrient. Studies have shown that phosphate is the limiting agent in the growth of
plants and algae. If not enough is present, the plants are slow growing or stunted. If too much phosphate is
present excess growth may occur, particularly in algae.A large percentage of the phosphate in water is
precipitated from the water as iron phosphate which is insoluble. If the phosphate is in shallow sediments, it
may be readily recycled back into the water for further reuse. In deeper sediments in water, it is available for
use only as part of a general uplifting of rock formations for the cycle to repeat itself.
THREE BIG IDEAS
FIRST IDEA
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Life is maintained by continuous flow energy from the sun through the biosphere, gravity,
and nutrient cycling which is also known as biogeochemical cycles thaat consist of the
phosphorous, nitrogen, carbon, and water cycles.
SECOND IDEA
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Some organisms produce the nutrient they need to live such as plants, other organisms
get nutrients from ingesting other animals, while some organisms recycle nutrients back
to producer organisms.
THIRD IDEA
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A lot of human activities are disrupting he flow of energy through food chains and food
webs and the cycling of nutrients throughout the biosphere.