Objectives

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Objectives

• Define and give examples of an organism, species,
  population, community and ecosystem.
• Distinguish between the biotic and abiotic
  factors in an ecosystem.
• Explain how habitats are important for organisms.

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Defining an Ecosystem

• Ecosystems are communities of organisms and their
  non-living environment.
• Examples are an oak forest or a coral reef.
• Ecosystems do not have clear boundaries.
• Things move from one ecosystem to another. Pollen
  can blow from a forest into a field, soil can
  wash from a mountain into a lake, and birds
  migrate from state to state.

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The Components of an Ecosystem

• In order to survive, ecosystems need several
  basic components energy, mineral nutrients,
  water, oxygen, carbon dioxide, and living
  organisms.
• Most of the energy of an ecosystem comes from the
  sun.

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Biotic and Abiotic Factors

• Biotic factors are environmental factors that are
  associated with or results from the activities of
  living organisms which includes plants, animals,
  dead organisms, and the waste products of
  organisms.
• Abiotic factors are environmental factors that
  are not associated with the activities of living
  organisms which includes air, water, rocks, and
  temperature.

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• Scientists can organize these living and
  nonliving things into various levels.

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Levels of Ecological Organization
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Organisms

• Organisms are living things that can carry out
  life processes independently.
• You are an organism, as is and ant, and ivy
  plant, and each of the many bacteria living in
  your intestines.
• Every organism is a member of a species.
• Species are groups of organisms that are closely
  related and can mate to produce fertile
  offspring.
• Examples

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Are these species?

• Birds
• Cats
• Poodles
• Reticulated Giraffes
• Turtles
• Humans
• European Americans

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Populations

• Members of a species may not all live in the same
  place. Field mice in Maine will not interact with
  field mice in Texas. However, each organism lives
  as part of a population.
• Populations are groups of organisms of the same
  species that live in a specific geographical area
  and interbreed.
• For example, all the field mice in a corn field
  make up a population of field mice.

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Populations

• An important characteristic of a population is
  that its members usually breed with one another
  rather than with members of other populations
• For example, bison will usually mate with another
  member of the same herd, just as wildflowers will
  usually be pollinated by other flowers in the
  same field.
• Other examples?

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Communities

• Communities are groups of various species that
  live in the same habitat and interact with each
  other.
• Every population is part of a community.
• The most obvious difference between communities
  is the types of species they have.

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Identify the organizational level of each of the
following examples. Choose from the following
terms Organism Population Community Ecosystem
Species
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1. All prickly pear cacti in the Sonora Desert
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2. All of the great white sharks found in oceans
worldwide
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3. The red maple tree found in Mr. Holtiens
front yard
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4. The sand, water, rocks, mud, plants, fish,
leeches, frogs, herons.found in Lake Winnebago
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5. The frogs and algae found in the aquarium at
the back of this room
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6. The frogs, algae, rocks and water found in the
aquarium at the back of this room
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7. All grass plants in the lawn surrounding your
house
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8. The one dandelion sprouting in your front yard
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9. All E. coli found growing on food and inside
of digestive tracts worldwide
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10. All bacteria found in your digestive tract
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Organization of Ecosystems Quiz

• Identify which parts of the drawing on the next
  slide fit each of the following categories
• Organism
• Population
• Community
• Ecosystem

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Habitat

• Habitats are places where an organism usually
  lives.
• Every habitat has specific characteristics that
  the organisms that live there need to survive. If
  any of these factors change, the habitat changes.
• Organisms tend to be very well suited to their
  natural habitats. If fact, animals and plants
  usually cannot survive for long periods of time
  away from their natural habitat.

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Objectives

• Describe the three main properties of a
  population.
• Describe exponential population growth.
• Describe how the reproductive behavior of
  individuals can affect the growth rate of their
  population.
• Explain how population sizes in nature are
  regulated.

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What Is a Population?

• A population is a group of organisms of the same
  species that live in a specific geographical area
  and interbreed.
• A population is a reproductive group because
  organisms usually breed with members of their own
  population.
• The word population refers to the group in
  general and also to the size of the population,
  or the number of individuals it contains.

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Properties of Populations

• Size is the actual number of individuals in the
  population
• Density is the number of individuals of the same
  species in that live in a given unit of area.
• Dispersion is the pattern of distribution of
  organisms in a population. A populations
  dispersion may be even, clumped, or random.
• Size, density, dispersion, and other properties
  can be used to describe populations and to
  predict changes within them.

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Population size
Population size
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Population Density
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Population dispersion
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How Does a Population Grow?

• A population gains individuals with each new
  offspring or immigration
• A population loses individuals with each death or
  emmigration
• A population will grow if

Births and immigration gt Deaths and emmigration
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• A population will shrink if

Births and immigration lt Deaths and emmigration
A population will remain stable if
Births and immigration Deaths and emmigration
A population would remain the same if each pair
of adults produced exactly two offspring, and
each offspring survived to reproduce.
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How Does a Population Grow?

• Growth rate is an expression of the increase in
  the size of an organism or population over a
  given period of time. It is the birth rate minus
  the death rate.
• Overtime, the growth rates of populations change
  because birth rates, death rates, immigration
  rates, and emmigration rates increase or
  decrease.
• For this reason, growth rates can be positive,
  negative, or zero.

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How Fast Can a Population Grow?

• Populations usually stay about the same size from
  year to year because various factors kill many
  individuals before they can reproduce.
• Examples?
• These factors control the sizes of populations.

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Reproductive Potential

• Reproductive potential is the maximum number of
  offspring that a given organism can produce.

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Reproductive Potential

• Reproductive potential increases when individuals
  
• 1. produce more offspring at a time
• 2.reproduce more often
• 3. reproduce earlier in life.
• According to these characteristics, what types of
  organisms would have the greatest reproductive
  potential?
• Which would have the smallest reproductive
  potential?

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• Reproducing earlier in life has the greatest
  effect on reproductive potential.
• Reproducing early shortens the generation time,
  or the average time it takes a member of the
  population to reach the age when it reproduces.
• Examples of early reproducers?

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Reproductive Potential

• Small organisms, such as bacteria and insects,
  have short generation times and can reproduce
  when they are only a few hours, days, or weeks
  old. As a result, their populations can grow
  quickly.
• In contrast, large organisms, such as elephants
  and humans, become sexually mature after a number
  of years and therefore have a much lower
  reproductive potential than insects.
• Darwin calculated that it could take 750 years
  for a pair of elephants to produce 19 million
  descendants. While bacteria could produce that in
  a few days or weeks.

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How Many Mice?

• 2 mice have a family 1 pair x 8 8 new mice
• 8 4 new pairs having baby mice 4 x 8 32
• 32 16 new pairs having baby mice 16 x 8 128
• Etc.
• If we graphed this data for ten generations what
  would it look like?

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Exponential Growth

• Exponential growth is growth in which a
  population increase a greater amount each
  generation.
• Exponential growth occurs in nature only when
  populations have plenty of food and space, and
  have no competition or predators.
• For example, population explosions occur when
  bacteria or molds grow on a new source of food.

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Exponential Growth
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Exponential Growth
J-curve

• In exponential growth, a large number of
  individuals is added to the population in each
  succeeding time period.

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What Limits Population Growth?

• Because natural conditions are neither ideal nor
  constant, populations cannot grow forever.
• Eventually, resources are used up or the
  environment changes, and deaths increase or
  births decrease.
• Under the forces of natural selection in a given
  environment, only some members of any population
  will survive and reproduce.

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Carrying Capacity

• Carrying capacity is the largest population that
  an environment can support at any given time.
• A population may increase beyond this number but
  it cannot stay at this increased size.
• Because ecosystems change, carrying capacity is
  difficult to predict or calculate exactly.
  However, it may be estimated by looking at
  average population sizes or by observing a
  population crash after a certain size has been
  exceeded.

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Carrying Capacity
S-curve
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Resource Limits

• A species reaches its carrying capacity when it
  consumes a particular natural resource at the
  same rate at which the ecosystem produces the
  resource.
• That natural resource is then called a limiting
  resource.
• Examples for animals?
• Examples for plants?
• The supply of the most severely limited resources
  determines the carrying capacity of an
  environment for a particular species at a
  particular time.

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Two Types of Population Regulation

• Population size can be limited in ways that may
  or may not depend on the density of the
  population.
• Causes of death in a population may be density
  dependent or density independent.

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Population Regulation

• When a cause of death in a population is density
  dependent, deaths occur more quickly in a crowded
  population than in a sparse population.
• This type of regulation happens when individuals
  of a population are densely packed together.
• Limited resources, predation and disease result
  in higher rates of death in dense populations
  than in sparse populations.

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Population Regulation

• When a cause of death is density independent, a
  certain proportion of a population may die
  regardless of the populations density.
• This type of regulation affects all populations
  in a general or uniform way.
• Severe weather and natural disasters are often
  density independent causes of death.

STOP AND DO POPULATION ACTIVITY
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Objectives

• Explain the difference between niche and habitat.
• Give examples of parts of a niche.
• Describe the five major types of interactions
  between species.
• Explain the difference between parasitism and
  predation.

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An Organisms Niche

• A niche is the unique position occupied by a
  species, both in terms of its physical use of its
  habitat and its function within an ecological
  community.
• A niche is different from a habitat. An
  organisms habitat is a location or type of
  ecosystem. However, a niche is an organisms
  pattern of use of its habitat.
• A niche can also be though of as the functional
  role, or job of a particular species in an
  ecosystem.
• Whitetail deer habitat vs. Whitetail deer niche
  example

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Ways in Which Species Interact

• The five major types of species interactions are
• Competition
• Predation
• Parasitism
• Mutualism
• Commensalism

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Ways in Which Species Interact

• These categories are based on whether each
  species causes benefit or harm to the other
  species in a given relationships in terms of
  total effects over time.

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Competition

• Competition is the relationship between two
  different species in which both species attempt
  to use the same limited resource such that both
  are negatively affected by the relationship.
• Examples

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Competition

• Members of the same species must compete with
  each other because they require the same
  resources because they occupy the same niche.
• Examples

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Indirect Competition

• Species can compete even if they never come into
  direct contact with each other.
• For example, suppose that one insect feeds on a
  certain plant during they day and that another
  species feeds on the same plant during the night.
  Because they use the same food source, the two
  species are indirect competitors.
• Humans rarely interact with the insects that eat
  our food crops, but those insects are still
  competing with us for food.

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Adaptations to Competition

• When two species with similar niches are placed
  together in the same ecosystem, we might expect
  one species to be more successful than the other.
• One way competition can be reduced between
  species is by dividing up the niche in time or
  space.

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Adaptations to Competition

• Niche restriction is when each species uses less
  of the niche than they are capable of using. It
  is observed in closely related species that use
  the same resources within a habitat.
• For example, C. stellatus, a barnacle species, is
  found only in the upper level of the intertidal
  zone when another barnacle species is present.
  When the other species is removed, C. stellatus
  can be found at deeper levels.
• The actual niche used by a species may be smaller
  than the potential niche.

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Niche restriction
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Predation

• Predation is an interaction between two species
  in which one species, the predator, feeds on the
  other species, the prey.
• In complex food webs, a predator may also be the
  prey of another species.
• Most organisms have evolved some mechanisms to
  avoid or defend against predators. (see this in
  video)

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• This is not predation.

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Predators

• Some predators eat only specific types of prey.
  In this kind of close relationship, the sizes of
  each population tend to increase and decrease in
  linked patterns, as shown below.

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Parasitism

• An organism that lives in or on another organism
  and feeds on the other organism is a parasite.
  Examples include ticks, fleas, tapeworms,
  heartworms, and bloodsucking leeches.
• The organisms the parasite takes its nourishment
  from is known as the host.
• Parasitism is a relationship between two species,
  the parasite, benefits from the other species,
  the host, and usually harms the host.

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What is this parasite?
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Parasitism vs. Predation

• The differences between a parasite and a predator
  are that a parasite spends some of its life in or
  on the host, and that the parasites do not
  usually kill their hosts.
• In fact, the parasite has an advantage if it
  allows its host to live longer.
• However, the host is often weakened or exposed to
  disease by the parasite.

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Mutualism

• Many species depend on another species for
  survival. In some cases, neither organism can
  survive alone.
• Mutualism is a relationship between two species
  in which both species benefit.
• Certain species of bacteria in your intestines
  form a mutualistic relationship with you. These
  bacteria help break down food that you cannot
  digest. In return, you give the bacteria a warm,
  food-rich habitat.
• Examples?

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Commensalism

• Commensalism is a relationship between two
  organisms in which one organism benefits and the
  other in unaffected.
• An example is the relationship between sharks and
  a type of fish called remoras. Remoras attach
  themselves to sharks and feed on scraps of food
  left over from the sharks meals.
• Even seemingly harmless activity, however, might
  have an effect on another species.

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Multiple Choice

• 1. What determines the carrying capacity of an
  environment?
• A. growth rates
• B. limiting resources
• C. natural selection
• D. territorial size

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Multiple Choice

• 1. What determines the carrying capacity of an
  environment?
• A. growth rates
• B. limiting resources
• C. natural selection
• D. territorial size

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Multiple Choice, continued

• Which of the following statements can be made
  about competition between organisms in a
  particular ecosystem?
• F. Organisms rarely compete with members of
  their own species.
• G. Organisms compete directly when they require
  the same resources.
• H. Organisms only compete when supplies of a
  resource are unlimited.
• I. Organisms only compete for resources when
  their populations are small.

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Multiple Choice, continued

• Which of the following statements can be made
  about competition between organisms in a
  particular ecosystem?
• F. Organisms rarely compete with members of
  their own species.
• G. Organisms compete directly when they require
  the same resources.
• H. Organisms only compete when supplies of a
  resource are unlimited.
• I. Organisms only compete for resources when
  their populations are small.

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Multiple Choice, continued

• 3. Which of the following describes a species
  niche?
• A. the unique role the species plays in an
  ecosystem
• B. the physical location where the species can
  be found on Earth
• C. the adaptation of a species population to its
  physical environment
• D. the maximum number of offspring all members
  of that species can produce

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Multiple Choice, continued

• 3. Which of the following describes a species
  niche?
• A. the unique role the species plays in an
  ecosystem
• B. the physical location where the species can
  be found on Earth
• C. the adaptation of a species population to its
  physical environment
• D. the maximum number of offspring all members
  of that species can produce

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Multiple Choice, continued

• 4. Which of the following expressions is used to
  calculate the change in population size?
• F. births plus deaths
• G. births plus deaths plus population
• H. births minus deaths
• I. births minus deaths plus population

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Multiple Choice, continued

• 4. Which of the following expressions is used to
  calculate the change in population size?
• F. births plus deaths
• G. births plus deaths plus population
• H. births minus deaths
• I. births minus deaths plus population

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Multiple Choice, continued

• Use this table to answer question 5.

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Multiple Choice, continued

• 5. Which of the interactions listed in the table
  is harmful to both species?
• A. commensalism
• B. competition
• C. mutualism
• D. predation

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Multiple Choice, continued

• 5. Which of the interactions listed in the table
  is harmful to both species?
• A. commensalism
• B. competition
• C. mutualism
• D. predation

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Multiple Choice, continued

• Use this illustration to answer questions 6 and 7.

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Multiple Choice, continued

• 6. What happens to population size between the
  time it overshoots carrying capacity to when it
  recovers and stabilizes?
• F. It remains stable.
• G. It declines steadily.
• H. It decreases before it stabilizes.
• I. It continues to increase at a steady rate.

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Multiple Choice, continued

• 6. What happens to population size between the
  time it overshoots carrying capacity to when it
  recovers and stabilizes?
• F. It remains stable.
• G. It declines steadily.
• H. It decreases before it stabilizes.
• I. It continues to increase at a steady rate.

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Multiple Choice, continued

• 7. If the population size was nearly 2,000 when
  it overshot carrying capacity, and 1,500 when it
  was at its lowest amount of decline during its
  recovery, what is the estimated carrying capacity
  of the population?
• A. 1,600
• B. 1,750
• C. 1,800
• D. 1,950

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Multiple Choice, continued

• 7. If the population size was nearly 2,000 when
  it overshot carrying capacity, and 1,500 when it
  was at its lowest amount of decline during its
  recovery, what is the estimated carrying capacity
  of the population?
• A. 1,600
• B. 1,750
• C. 1,800
• D. 1,950