35.1 A population is a local group of organisms of one species
I. Defining Populations A.A populations size is determined by the
availability of food and space, weather conditions, and breeding
patterns B.When scientists study populations they must determine
its boundaries, such a lake, a state or the whole country
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Boundaries Regional Local
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What is a species? Distinct form of life Population of
organisms which can breed and produce offspring
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What about these? Peacock + Peahen = Peachicks Horse + Donkey =
Mule
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II. Population Density A. Population Density is the number of
individuals of a particular species per unit of area or volume
B.Population density is useful when comparing two populations in
different areas Class Example.
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III. Sampling Techniques A. Since it is impossible to count
every member of a population scientists use sampling techniques to
estimate the size of a population 1.Quadrats- scientists mark off a
square boundary at several locations and take an average (plants)
2.Indirect Counting- counting nests, burrows or tracks instead of
the organisms themselves (insects) 3.Mark-Recapture- scientists
trap and mark individuals (birds) B. Most sampling techniques
involve making assumptions about the populations being studied
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Which sampling technique? Black bear: indirect Bats:
mark-recapture Cactus: quadrat
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Population Distribution
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Which distribution pattern? Termite MoundRattlesnake Clumped
Random
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35.2 Limits to population growth I. Exponential Growth of
Populations A. A populations ability to grow partly depends on the
rate at which its organisms can reproduce B. Exponential Growth is
when the population multiplies at a constant factor at constant
time intervals i.e. bacteria doubling every 20 minutes
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Transparency 35A-5 1. Compare and contrast the two growth
curves. Both curves show a period of rapid population growth, but
the fur seal population eventually levels off. The bacterial
population appears to continue growing exponentially.
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Transparency 35A-6 2. Which curve do you think more closely
resembles the growth of most populations in nature? Explain.
Limited growth curve; populations in nature are subject to limiting
factors that prevent long-term exponential growth.
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II. Carrying Capacity A.A population may start to grow
exponentially, but eventually one or more environmental factors
will limit its growth B. A limiting factor is a condition that can
restrict a populations growth C. The carrying capacity is the
number of organisms in a population that the environment can
maintain or carry
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III. Factors Affecting Population Growth A.Density-Dependent
Factors is a factor that limits a population more as a population
density increases B. Density-Independent Factors are factors that
limit population but are unrelated to population density
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Population Growth Food availability Temperature and humidity
Density- Independent Density-dependent
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IV. Population Cycling A.A boom and bust growth cycle is one
that increases rapidly followed by a sharp decline B. Other growth
cycles are influenced by those of other populations in their
environments
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Population Cycling
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35.3 Predicting the impact of human population growth
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http://www.worldometers.info/world- population/
http://www.worldometers.info/world- population/
http://www.eahdfoundation.org/world_live_c lock.php
http://www.eahdfoundation.org/world_live_c lock.php
http://www.census.gov/main/www/popclock. html
http://www.census.gov/main/www/popclock. html
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10 Largest Countries - 2006 CountryPopulation (Millions) 1.
China1,311 2. India1,122 3. United States299 4. Indonesia225 5.
Brazil187
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10 Largest Countries - 2006 CountryPopulation (Millions) 6.
Pakistan166 7. Bangladesh147 8. Russia142 9. Nigeria135 10.
Japan128
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10 Largest Countries - 2050 CountryPopulation (Millions) 1.
India1,628 2. China1,437 3. United States420 4. Nigeria299 5.
Pakistan295
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10 Largest Countries - 2006 CountryPopulation (Millions) 6.
Indonesia166 7. Brazil147 8. Bangladesh142 9. Rep. of Congo135 10.
Ethiopia128
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History of Human Population
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Human Pop Graph
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I. History of Global Population Growth A.For most of human
history, the human population has grown very slowly or not at all
B. Human population growth depends on birth rates and death rates
C. The introduction of farming has provided a stable food supply so
birth rates have gone up D. Advances in modern medicine, nutrition
and sanitation have caused death rates to go down E. These factors
have caused the human population to increase dramatically
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Transparency 35B-2 1. Which age group forms the largest bulge
in the age-structure graph of the United States? Of Kenya? 4044;
under 5
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Transparency 35B-3 2. Which country is likely to undergo the
greatest increase in population in the next 20 years? Explain.
Kenya; the majority of the population is under 25 years old, which
is the portion likely to have children in the next 20 years.
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II. Predicting Future Population Growth A.The Age Structure of
a population is the proportion of people in different age groups B.
Prediction of future growth varies because of the difficulty
predicting future birth and death rates of various countries C. The
question remains whether or not Earth will have the capacity for
the human population
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35.4 Species interact in biological communities
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I. Competition Between Species A.Members of a population may
compete for the same limited resource B. Within a community,
interspecific competition takes place when two or more species rely
on the same limited resource C. If two species are so similar in
their requirements that the same resource limits both species
growth it is called competitive exclusion D. A niche includes an
organisms living place, its food source, the time of day it is most
active and many other factors that are specific to that organisms
way of life
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Competitive Exclusion
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II. Predation A.Predation is when one organism eats another B.
Eating and avoiding being eaten are important to survival and
predators and prey have developed many adaptations 1.Predator
adaptations include: being fast and agile, coloring that
camouflages, hunting in groups, acute sense to find prey and having
claws, teeth, fangs and stingers to help catch prey 2. Prey
adaptations include: retreating or fleeing from predators,
camouflage, defensive coloring, mimicry, secreting poisonous
chemicals, having spines and thorns
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Predator- Prey Relations
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III. Symbiotic relationships A.A symbiotic relationship is when
two species live in or on one another B. There are three main types
of symbiotic relationships 1.Parasitism- A parasite gets its food
at the expense of another organism, i.e. mosquitos and humans 2.
Mutualsim- Both organism benefit from the relationship, i.e. E.Coli
and humans 3. Commensalism- One organism benefits and the other is
neither hurt nor helped, i.e. sharks and remoras
Symbiosis - Which is it? Liver Fluke Mongoose & Cobra
Predator-Prey Parasitism
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Symbiosis - Which is it? Clownfish & Anemone Air Plant
Commensalism Mutualism
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35.5 Disturbances in communities I. Disturbances to Communities
A. Natural Disturbances are events such as fires, volcanic
eruptions, floods, storms, and droughts all destroy resources such
as shelter and water B. Disturbances can be either positive or
negative C. Humans also have an impact on communities which can be
either positive or negative
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Surviving Environmental Change
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II. Ecological Succession A.The series of changes in the
species in a community, often following a disturbance is known as
ecological succession B.There are two types of succession:
1.Primary succession which is when new community arises from a
previously lifeless area i.e. plants growing on a volcanic island
2. Secondary succession is when a new community arises from a
previous community i.e. a forested area which has been cleared and
abandoned
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Primary Succession
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Secondary Succession
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III. Human activities and species diversity A.60% of the Earths
land is used by humans, mainly for cropland or rangeland B.Humans
usually have a negative effect on species in two ways 1.Clearing
the Land- Humans clear vast amounts of land to make way for farming
and building 2. Introduced Species are species that are moved from
one location to another either accidentally or on purpose. These
new species may take over an area and prey on native species or
drive them from their niches
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Invasive species in Washington
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Invasive species in Ohio Emerald ash borer Canada thistle Zebra
mussel Dutch Elm disease
