Biodiversity, Species Interactions, and Population Control / Chapter 5!! ?

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BIODIVERSITY, SPECIES INTERACTIONS, and
POPULATION CONTROL! ?
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How do Species Interact?

• 5 major ways!
• Interspecific Competition
• Predation
• Parasitism
• Mutualism
• Commensalism
• Interactions help limit population size. These
  interactions influence abilities of interacting
  species to survive and reproduce thus serving as
  agents of natural selection.

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Competition

• Each species has a niche.(some are generalists
  with broad niches, others are specialists with
  narrow niches)
• When niches overlap, competition occurs. No two
  species can share a niche for very long
  (competitive exclusion principle)

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PREDATORS!
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• In predation, a member of one species feeds
  directly upon all or part of another living
  organism as part of a food web.
• Herbivores, carnivores, and omnivores are
  predators. (Decomposers and detritovores are not)
• See page 102 to read about how predators catch
  prey and how prey tries to keep from being eaten.
  Vivid reading!

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PREY!! PREDATOR!!
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Read about Kelp! p. 104
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PARASITISM! (Feeds on the body or energy of
another organism)
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MUTUALISM! Both Benefit!
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Commensalism!Benefits one, but doesnt help or
harm other. (bromeliads and tree.whale and
barnacle)
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Reduce Competition by Resource Partioning!

• Species competing for similar scarce resources
  evolve specialized traits that allow them to use
  shared resources at different times, in different
  ways, or in different places.
• Examples are warblers and honey creepers.

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We all live in the same tree! But we eat
different things in different places in our tree!
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Limits to Population Growth!!

• Populations differ in factors such as
  distribution, numbers, age structure, and
  density.
• Age structure(number of individuals in different
  age groups)
• Density(number of individuals in a certain space)
• Population dynamics is a study of how these
  characteristics of populations change in response
  to environmental conditions.(Temperature,
  presence of disease or harmful chemicals,
  resource availability, and arrival or
  disappearance of a competitor)

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Snow bird to beach bunny! (NY to FLA) (Mice leave
when cat moves in)
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(No Transcript)
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CLUMPS and PATCHES

• Most populations live in clumps or patches.
  (Desert vegetation near water, wolf packs, fish
  schools, bird flocks, herds)
• Groups cluster where resources are
• Searching in groups is better than alone
• Groups protected more from predators
• Better hunting in packs
• Group together for mating and raising young.
• The Living World is Clumpy and Patchy!!

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We are happy! We Clump!
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Uniform RandomDispersion
Dispersion
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4 Variables Govern Population Size!

• Births(come in)
• Deaths(go out)
• Immigration(move in)
• Emigration(move out)
• (Age structure is important in determining if a
  population is likely to grow or decrease. )

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Biotic Potential

• Biotic potential is the capacity for populations
  to grow under ideal conditions.
• Huge animals like elephants and whales have low
  biotic potential.
• Bacteria and insects have high biotic potential

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• The INTRINSIC RATE OF INCREASE (r) is the rate at
  which the population of a species would grow if
  it had unlimited resources.
• Populations with high (r) have individuals that
  reproduce early, have short generation times,
  reproduce many times, and have many offspring
  each time they reproduce.(ExampleBacteria)
• No population can grow indefinitely because of
  limiting factors such as light, water, space, and
  food, or exposure to competitors, predators, or
  disease. THERE ARE ALWAYS LIMITS TO POPULATION
  GROWTH)

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• Environmental Resistance is the combination of
  all factors that act to limit population growth.
• Together, biotic potential and environmental
  resistance determine CARRYING CAPACITY (K) the
  maximum population of a given species that a
  particular habitat can sustain indefinitely
  without being degraded.
• The growth rate of a population decreases as its
  size nears the carrying capacity of its
  environment.

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Food and Space are getting scarce ? Carrying
capacity reached. Fewer fishes.
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• EXPONENTIAL GROWTH starts slowly, accelerates
  quickly. (Few limitations on growth. Many
  resources.) This is shown on graph as a J-shaped
  curve.
• LOGISTIC GROWTH involves rapid exponential
  growth followed by a steady decrease until
  population levels off. (Dwindling resources) This
  is shown as an S-shaped curve on a graph.

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• Changes in the population of a keystone species
  such as the southern sea otter or the American
  alligator can alter the species composition of an
  ecosystem.
• Example Decline in sea otters caused a decline
  in species dependent on them, such as giant kelp.
  This reduced species diversity in kelp forests
  and altered its functional biodiversity by
  upsetting food webs and reducing energy flows and
  nutrient cycles.

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I am endangered. ? Read about my plight on p. 110
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I EAT SEA OTTERS!!
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Parasites in my tummy make sea otters sick!!
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Moving on..

• Sometimes a population grows so fast that it
  doesnt transition from exponential to logistic
  growth smoothly.alas, it temporarily OVERSHOOTS,
  or exceeds the carrying capacity of the
  environment. (Caused by reproductive time lag)
• Then the population suffers a DIEBACK, or CRASH,
  unless the excess individuals move to new
  resources or switch to new resources.

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REPRODUCTIVE PATTERNS

• R-SELECTED SPECIES species with a capacity for a
  high rate of population increase (r).
• Have many small offspring. Little parental care.
• Big numbers of babies offset large losses.
  Reproduce and disperse rapidly when conditions
  are right.
• Opportunistic.

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We take advantage!!
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• K-SELECTED SPECIES These are competitor species.
  
• Reproduce later in life. Have fewer offspring.
  Born larger. Cared for by parent.
• More competitive for resources.
• Follow logistic growth curve.
• Can be prone to extinction, especially if heavily
  hunted.

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We are K-Select
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r-select K-select on the
farm!!
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Genetic Diversity in Small Populations! It can be
lost!

• Founder Effect a few individuals in a population
  colonize a new habitat that is geographically
  isolated from the rest of the population.
• These foxes live in isolated areas.

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• Demographic bottleneck Only a few individuals
  survive a catastrophe. Lack of genetic diversity
  may limit their ability to rebuild population. ?
• Even if population increases, lack of genetic
  diversity may lead to an increase of genetic
  diseases.

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• Genetic Drift Random changes in gene frequency
  may lead to unequal reproductive success.
• Some individuals may breed more, so their genes
  dominate. This could help or hinder the
  populations survival.
• This is similar to founder effect or bottleneck.
• Example polydactyly in Old Order Amish.

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• Inbreeding Occurs when individuals in a small
  population mate with one another.
• Can occur through bottleneck.
• Increases frequency of defective genes.
• Example Hapsburg royal family

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POPULATION DENSITY

• Population Density the number of individuals in
  a population found in a certain area.
• Density-dependent population controls include
  predation, parasitism, infectious disease, and
  competition. These have a greater effect as
  population density increases.
• Density-independent population controls are not
  dependent on population density severe freeze,
  floods, hurricanes, fire, pollution, habitat
  destruction.

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4 Patterns of Variation in Population Size

• STABLE fluctuates only slightly above or below
  carrying capacity.
• Example tropical rainforest species

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• IRRUPTIVE explodes with a high peak, then crash!
  Gets stable or goes low.
• Example Temperate climate insects

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• CYCLIC cyclic fluctuations or boom and bust
  cycles.
• Examples lemmings, lynx and hare.
• Top-down regulation is through predation.
• Bottom-up regulation is by scarcity of resources.

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• IRREGULAR No recurring pattern. Chaos,
  catastrophe, severe weather.
• Examples Bubonic plague, potato famine, AIDS

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YAY!! TECHNOLOGY!!

• Technological, social, and other cultural changes
  have extended the earths carrying capacity for
  the human species.

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Read about the White-Tailed Deer. pp.114-15