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Mahopac Central School
District Curriculum 2003-04
Ecosystems
A. Evolution is the change in a species over time
1. Evidence for evolution is found in the fossil record, by comparing DNA, and in the
developmental patterns of living things
a. organisms in the same groups or phylums show similar patterns of
development
2. Jean Lamarck
a. Lamarck believed that if an organ was used more it would get bigger, if used
less it would get smaller
b. this idea was called the Theory of Use and Disuse
c. he proposed that if a parent acquired a new trait during its lifetime (like bigger
muscles) it would be passed on to the offspring
d. his ideas proved wrong
3. Charles Darwin – he spent many years making observations about the reasons
for the variety in living things on Earth
a. his Theory of Natural Selection is based on several ideas
b. natural events can change the environment and a struggle for survival
occurs.
1) this struggle is greatest between organisms that are similar and have the
same needs
c. the individuals that survive are the best adapted to their environment –
adaptations that help may be differences in structure, behaviors, or in how
the organisms body works
d. survivors are a better fit in their environment because they have certain
differences or variations that help them to survive better than others
1) variation provides diversity or a wide range of traits within a species
e. individuals that survive longer are more likely to reproduce – they may
transfer these beneficial differences to their offspring
f. the beneficial variations may be passed on generation after generation
g. the shorter the natural lifespan of an organism, the faster it reproduces, and
the faster the effects of natural selections can be seen
1) think of antibiotic resistant bacteria, for example
4. In summary:
a. in any population of organisms, there are differences or variations among the
individuals
b. a change in environmental conditions can affect which of these variations is
most useful
c. those members of a species best adapted to their environment live longer,
reproduce more like themselves, and over time pass their beneficial
adaptations on to their relatives
5. There are two main sources of variations within a species: sexual reproduction
and mutations
a. in sexual reproduction the offspring receive genetic material from both
parents
1) this new combination of genetic material creates a new, unique,
individual
2) no two individuals produced by sexual reproduction are completely alike
Mahopac Central School
District Curriculum 2003-04
b. mutations are changes in the sequence of base pairs that determine the traits
of an organism
1) mutations may be beneficial, harmful, or have no effect on survival
2) every so often, a mutation might produce a variety that may be more fit to
survive
3) small differences between parent and offspring can build up, generation
after generation, until the new generations are very different from their
ancestors
6. Genetic Engineering – the alteration of an organisms genetic material to
eliminate undesirable traits or to produce desirable traits
a. selective breeding is a common form of genetic engineering
b. scientists can now transfer genes from one organism to another to create a
new variety with a desirable trait
7. Extinction
a. if a species does not adapt quickly enough to environmental changes, all of
its kind may die off
b. extinction of species is common
c. a study of the fossil record shows that the vast majority of species who have
lived on the Earth over time are now extinct
8. The fossil record
a. a major source of evidence supporting the Theory of Evolution comes from
studying the layers of rock underground
b. inside the many layers of sedimentary rock there is evidence of the long
history of life on Earth
c. the remains of an organism that once lived, such as imprints, are called
fossils
d. life forms have changed over time
e. more recently deposited layers contain fossils resembling species that exist
today
f. life has progressed, from the simple to the complex, over geologic time
1) the ancestors of most modern species had simpler structures than those
of their descendants
B. The world presents living things with a constantly changing environment – to survive,
organisms must be able to respond and adjust to the changes
1. Depending on an organisms activities, its needs for energy might vary greatly but
all living things require energy to live
2. Energy may come from combining oxygen with food, in the form of glucose, in
the cell’s mitochondria (glucose + oxygen  water + carbon dioxide + energy)
a. water and carbon dioxide are waste products created by this process
b. a few living things can make energy without oxygen although the breakdown
of the glucose doesn’t release as much energy as it does with oxygen
present
3. Scientists have divided organisms into groups based on how they get their
energy
a. producers make their own food
1) green plants use light energy to convert simple chemicals into ones useful
for energy
2) chlorophyll traps the Sun’s energy and converts it to chemical energy
3) carbon dioxide + water + energy  glucose + oxygen + water
Mahopac Central School
District Curriculum 2003-04
4) CO2 + H2O + energy  C6H12O6 + H2O + O2
b. consumers cannot make their own food
1) all animals are consumers – a predator hunts, kill, and eats other animals
– prey are the animals hunted and killed
2) herbivores are plant eaters (also known as primary consumers),
carnivores are meat eaters, omnivores eat both plants and animals
3) secondary consumers eat primary consumers
4) tertiary consumers eat secondary consumers
5) people can be primary, secondary or tertiary consumers, predators or
prey
c. decomposers gain energy by breaking down the complex chemicals in waste
or from dead organisms
1) fungus are decomposers as are many bacteria
C. Organisms respond to stimuli in their environment
1. The ability to sense and respond to messages is important to the survival of an
organism
a. a response to a stimuli requires energy
b. organisms acquire energy through their food
c. food provides the molecules that serve as fuel and building materials for all
organisms
2. The sum of all the chemical reactions in your body is called metabolism – it is
influenced by several factors
a. hormones regulate the rate of metabolism
b. how much exercise you get influences metabolism
c. what kinds of food you eat has something to do with it, too
3. Groups of substances needed by living things include:
a. carbohydrates for quick energy
b. fats for stored energy
c. proteins for growth and repair
d. vitamins for disease prevention
e. minerals for bones, teeth, red blood cells, and muscle
f. water for cell cytoplasm, blood, and tissue fluids
4. If an organism does not get the correct amount of any one of the nutrients, it
may:
a. gain weight it does not need
b. lose weight it does need
c. become diseased
5. The amount of energy in foods is measured in calories
a. one calorie is the amount of energy needed to raise the temperature of 1000
grams of water by 1Celsius
b. the number of calories an individual needs varies with:
1) weight, age, gender, activity level, and metabolic rate
c. carbohydrates and proteins contain 4 calories per gram
d. fats contain 9 calories per gram
6. Too much or too little of a substance may cause problems for your body
a. too much of a good thing can be bad, too
b. tobacco, alcohol, and drugs can seriously harm your body
1) the effects of these substances may show up quickly or the effects may
not be seen for years
Mahopac Central School
District Curriculum 2003-04
c. expectant mothers must be extremely careful about what they put in their
bodies
D. Most energy used by living things originates from the Sun
1. Energy from the Sun helps plants grow and humans eat plants or the animals
that eat plants for energy
a. most of the energy that enters our environment from the Sun is not captured
by livings things and eventually is lost as heat escapes from the Earth
2. Using the energy from sunlight (in the presence of chlorophyll), plants make food
from carbon dioxide and water
a. oxygen is released as a by-product (waste) and glucose (food) is produced
b. algae are organisms that also contain chlorophyll
c. the algae in the oceans produce most of the oxygen for the Earth
3. Photosynthesis:
a. is the major source of atmospheric oxygen
b. removes carbon dioxide from the atmosphere
c. is a major source of chemical energy for use by organisms
4. Carbon/Oxygen Cycle – they are kept in balance by photosynthesis and
respiration
a. carbon dioxide is used by plants, and plants produce oxygen
(photosynthesis)
b. animals use the oxygen and animals produce carbon dioxide (respiration)
5. The Nitrogen Cycle – nitrogen is an essential element for living things and is
needed to build proteins
a. bacteria in the soil and in the roots of certain plants can take nitrogen out of
the air and convert it to a useful form
b. plants absorb the nitrogen and use it to build proteins
c. animals get nitrogen by eating plants and other animals
d. animals use some of the protein they take in for energy – nitrogen is released
in their wastes and some bacteria convert this waste nitrogen into a form
usable by plants
e. when plants and animals die, other bacteria (decomposers) break them down
and convert the nitrogen into a usable form
f. plants absorb this nitrogen and it’s recycled (used again)
g. other bacteria break down nitrogen-bearing materials and the nitrogen is
released back into the air and it’s recycled (used again)
E. Food Chains and Webs
1. Food chain – it shows the path of energy transfer from green plants through a
series of organisms each of which consumes the preceding organism
a. green plants to cricket to frog to snake to owl, for example
2. A food web better illustrates what really happens to energy in an ecosystem
a. this is because most organisms eat more than one kind of other organism
b. a food web shows the branching connections between an organism and its
energy sources
3. An energy pyramid illustrates what happens to the amount of energy left in an
ecosystem as it progresses from green plants to the highest level consumer
a. at each transfer, energy is lost to the system
b. this is because the organism consuming the organism before it on the chain
or web cannot use all of the energy from that organism
c. energy is lost as body heat
d. green plants are the base on which life on Earth is supported
Mahopac Central School
District Curriculum 2003-04
F. Ecology – the study of how all living things interact with one another and how they
interact with their physical environment
1. A population is all the members of the same type of living thing in a given area
2. A community is all the plant and animal populations interacting in a given area
3. Physical factors are all the non-living variables the living things interact with
a. physical factors greatly influence the type of plant life in an area, which in
turn, influences the animals that depend on the plants
b. these physical factors include:
1) climate – the long term average weather – influences the amount of light
available for photosynthesis and ambient temperatures
2) soil – effects plant growth, erosion, and mineral content
3) water – vital to all life forms
4) air – controls the amount of oxygen available and its cleanliness
influences the amount of light available to plants
4. An ecosystem is the communities of plants and animals and the non-living
physical factors with which they interact
5. When populations exist in balance with one another, the environment is stable –
this stable state is called a climax community
a. there is usually a balance between predators and prey in such environments
b. their populations change in lockstep (they change in the same direction)
c. if some major change occurs, this balance may be upset
1) pesticide (insect poison) abuse has caused bird populations to diminish
when they lost their source of food
d. when a community is forced to respond to the change, it goes through a
series of changes as it regains its balance and becomes stable again
e. the stages of change are called ecological succession
6. Ecological Succession
a. variations within members of a population may allow certain individuals to be
better adapted to change
b. new species may replace other, older species as the environment changes
c. these new species can lead to further change in the environment
7. Limiting Factors – those things that can slow down the growth of a population
a. these factors include: light, food, shelter, water, climate, and predation
G. Pollutants – substances that are harmful to living things
1. Pollutants may contaminate the air, water, and soil (atmosphere, hydrosphere,
and lithosphere)
a. burying waste underground commonly contaminates the well water in that
area
b. burning waste just moves it into the air where eventually it will return in some
form
c. farmers use of pesticides and herbicides may poison the soil and render it
uninhabitable for useful microbes
2. Waste products from industry, cars, and homes often add to pollution
3. A growing human population has placed large demands on the environment
a. since the industrial revolution – when people started burning large quantities
of fossil fuels – a large amount of pollution has been created
4. The Greenhouse Effect says that the Earth’s atmosphere is getting warmer as a
result of the build-up of heat absorbing gases
a. carbon dioxide, methane, ozone, nitrogen oxides, and water vapor are all
greenhouse gases
Mahopac Central School
District Curriculum 2003-04
b. since the industrial revolution, the amount of carbon dioxide in the atmosphere
has increased by 27%
1) the burning of coal, natural gas, and oil are the cause
c. since the industrial revolution, the amount of methane in our atmosphere has
increased by 100%
1) farming practices and landfills are the primary causes
d. ozone in the lower atmosphere is produced from the exhaust of automobiles
interacting with the energy in sunlight
e. nitrogen oxides come from the burning of fossil fuels, too
f. all of these greenhouse gases allow light to enter our atmosphere, but won’t
allow heat to escape
5. Ozone depletion in our upper atmosphere
a. ozone acts to block dangerous ultraviolet radiation which causes skin cancer
and damages crops and some types of animal life
b. the use of chlorofluorocarbons (CFC’s) is the major cause of the depletion
c. CFC’s are used as refrigerants, a propellant in spray cans, and in the
manufacture of styrofoam products
d. it chemically reacts with ozone molecules, breaking them down
H. Renewable and Nonrenewable resources
1. Natural resources are materials and energy that are used by living things
2. Conservation is the wise use of natural resources
3. Any resource that is used up faster than nature can replace it is a nonrenewable
resource
a. fossil fuels are nonrenewable – they contain trapped solar energy
b. many strategic metals are nonrenewable – when they’re gone, they’re gone
forever
1) the United States has 5% of the world’s population but we use 25% of the
world’s energy
4. Any resource that can’t be used up faster than nature can replace it is a
renewable resource
a. sunlight is renewable
1) solar collectors on roofs can heat water and heat homes
2) photovoltaic cells can convert sunlight to electricity
b. wind is renewable – wind farms can generate electricity
c. falling water (hydroelectric projects) is renewable
1) falling water turns turbines which generate electricity
d. tides are renewable – rhythmic rise and fall of sea level can turn turbines to
generate electricity
e. geothermal energy (heat from the Earth’s interior) is renewable
1) the heat can warm homes, schools, and businesses
2) the heat can be used to generate electricity
f. biomass/wood is renewable
1) wood burning stoves can heat homes
2) biomass can be used to make alcohol – a liquid fuel
5. The supply of nonrenewable resources can be extended by recycling
a. recycling is the process of reusing resources to make new products