Species Interaction

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Species Interaction
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Species Interact in Five Major Ways

• Interspecific Competition
• Predation
• Parasitism
• Mutualism
• Commensalism

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Interspecific Competition

• Occurs when members of two or more species
  interact to gain access to the same limited
  resources such as food, light, or space

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Predation

• Occurs when a member of one species (the
  predator) feeds directly on all or part of a
  member of another species (the prey)

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Parasitism

• Occurs when one organism (the parasite) feeds on
  the body of, or the energy used by another
  organism (the host), usually by living on or in
  the host

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Mutualism

• Is an interaction that benefits both species by
  providing each with food, shelter, or some other
  resource.

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Commensalism

• Is an interaction that benefits one species but
  has little, if any, effect on the other.

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These interaction

• have significant effects on the resource use and
  population sizes of the species in an ecosystem.
• also influence the abilities of the interacting
  species to survive and reproduce, thus serve as
  agents of natural selection

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Competition

• The most common interaction
• The niches of two species overlap when they are
  competing for the same resources.

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Competitive exclusion principle

• Two species cant occupy exactly the same
  ecological niche for very long.

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If one species can take over the largest share of
one or more key resources, the other competing
species must

• Migrate to another area (if possible)
• Shift its feeding habits or behavior through
  natural selection
• Suffer a sharp population decline
• Become extinct in that area

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PREDATION
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Predators

• Herbivores
• Carnivores
• Omnivores

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Methods to capture preys

• Herbivores just walk, swim, fly
• Carnivores
• pursuit,
• ambush,
• camouflage,
• chemical warfare

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Prey Adaptations

• Avoid detection
• camouflage, mimics,
• diurnal/nocturnal

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Prey Adaptations

• Avoid detection
• camouflage, mimics,
• diurnal/nocturnal
• Avoid capture
• flee
• resist
• escape

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Prey Adaptations

• Avoid detection
• camouflage, mimics,
• diurnal/nocturnal
• Avoid capture
• Protective shells
• Thick bark
• Spines and thorns
• Chemical warfare

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• At the individual level, members of the predator
  species benefit and members of the pray species
  are harmed.
• At the population level, predation plays a role
  in evolution by natural selection.

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Coevolution

• Evolution in which two or more species interact
  and exert selective pressures on each other that
  can lead each species to undergo adaptations.
• Ex. Predator-prey, parasite-host

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Symbiosis Mutualists, Commensalists and Parasites
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Parasitism

• Occurs when one species (the parasite) feeds on
  the body of, or the energy used by, another
  organism (the host), usually by living on or in
  the host.
• The parasite benefits and the host is harmed but
  not immediately killed

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Parasitism

• Parasite usually is smaller than host
• Live on
• Live in
• Little contact

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Mutualism

• DEFINITION
• An interaction between two individuals of
  different species that benefits both partners in
  this interaction

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Pollination

• Animals visit flowers to collect nectar and
  incidentally carry pollen from one flower to
  another
• Animals get food and the plant get a pollination
  service

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Yucca and Yucca Moth

• Yuccas only pollinator is the yucca moth. Hence
  entirely dependent on it for dispersal.
• Yucca moth caterpillars only food is yucca
  seeds.
• Yucca moth lives in yucca and receives shelter
  from plant.

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Lichen (Fungi-Algae)

• Symbiotic relationship of algae and
  fungaeresults in very different growth formas
  with and without symbiont.
• What are the benefits to the fungus?

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Commensalists

• Benefit from the host at almost no cost to the
  host
• Birds nesting in trees
• Eyelash mite and humans
• Sharks and remora

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To avoid or reduce Competition

• Some species develop adaptations that allow them
  to reduce or avoid competition with other species
  for resources. In other words, some species
  evolve to reduce niche overlap.

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Resource Partitioning

• Process of dividing up resources in an ecosystem
  so that species with similar needs (overlapping
  ecological niches) use the same scarce resources
  at different times, in different ways, or in
  different places.

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Population Growth

• No population can continue to grow indefinitely
  because of limitations on resources and because
  of competition among species for those resources.

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Populations Have Certain Characteristics

• Populations differ in
• Distribution
• Numbers
• Age structure
• Density

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Population dynamics

• Is a study of how these characteristics of
  populations change in response to changes in
  environment conditions.

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Changes in population characteristics due to

• Temperature
• Presence of disease organisms or harmful
  chemicals
• Resource availability
• Arrival or disappearance of competing species

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Most Populations Live Together in Clumps or
Patches

• Population distribution
• Clumping (Ex. Wolf packs, desert vegetation
  around springs,)
• Uniform dispersion ( Ex.Creosote bushes in a
  dessert)
• Random dispersion (Ex. Dandelions)

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Why clumping?

• Species tend to cluster where resources are
  available
• Groups have a better chance of finding clumped
  resources
• Protects some animals from predators
• Packs allow some to get prey
• Temporary groups for mating and caring for young

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• The living world is mostly clumpy and patchy

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Populations Can Grow, Shrink, or Remain Stable

• Population size governed by
• Births
• Deaths
• Immigration
• Emigration
• Population change
• (births immigration) (deaths
  emigration)

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Age structure

• Pre-reproductive age
• Reproductive age
• Post-reproductive age
• The size of a population with a fairly even
  distribution among these three age groups tends
  to remain stable.

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No Population Can Grow Indefinitely J-Curves
and S-Curves

• Biotic potential capacity for population growth
  under ideal conditions.
• Low
• High
• Intrinsic rate of increase (r) is the rate at
  which the population of a species would grow if
  it had unlimited resources.
• Individuals in populations with high r
• Reproduce early in life
• Have short generation times
• Can reproduce many times
• Have many offspring each time they reproduce

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No Population Can Grow Indefinitely J-Curves
and S-Curves

• Size of populations limited by
• Light
• Water
• Space
• Nutrients
• Exposure to too many competitors, predators or
  infectious diseases

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• Environmental resistance Is the combination of
  all factors that act to limit the growth of a
  population.
• 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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Exponential or geometric growth

• Exponential growth starts slowly but then
  accelerates as the population increases, because
  the base size of the population is increasing
  (J-shaped growth curve)

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Logistic growth

• Involves rapid exponential population growth
  followed by a steady decrease in population
  growth until the population size levels off.

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Why logistic growth?

• This slowdown occurs as the population encounters
  environmental resistance from declining resources
  and other environmental factors and approaches
  the carrying capacity of its environment.

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• After leveling off, a population fluctuates
  slightly above and below the carrying capacity.
• The size of such population may also change as
  the carrying capacity does.
• Read page 110

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When a Population Exceeds Its Habitats Carrying
Capacity, Its Population Can Crash

• Carrying capacity not fixed
• Reproductive time lag may lead to overshoot
• Dieback (crash)
• Damage may reduce areas carrying capacity

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Reproductive Patterns

• r-selected species
• Have many, usually small, offspring
• Little or no parental care or protection
• Massive losses of offspring.
• Ex. Algae, bacteria, rodents, frogs,..
• Tend to be opportunists

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Reproductive Patterns

• k- selected species
• Tend to reproduce later in live
• Have a small number of offspring with fairly long
  life spans
• For k-selected mammals, the offspring develop
  inside their mothers, are born fairly large,
  mature slowly and are cared
• They do well in competitive conditions

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Genetic Diversity and small populations

• Several genetic factors can play a role in the
  loss of genetic diversity and the survival of
  small, isolated populations.
• Founder effect
• Demographic bottleneck
• Genetic drift
• Inbreeding

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Founder effect

• Can occur when a few individuals in a population
  colonize a new habitat that is geographically
  isolated from other members of the population. In
  such a cases, limited genetic diversity may
  threaten the survival of the colonizing population

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Demographic bottleneck

• It occurs when only a few individuals in a
  population survive a catastrophe such as a fire.
  Lack of genetic diversity may limit the ability
  of these individuals to rebuild the population
  (increase in the frequency of harmful genetic
  deseases)

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Genetic drift

• It involves random changes in the gene
  frequencies in a population that can lead to
  unequal reproductive success. The founder effect
  is one cause of genetic drift.

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Inbreeding

• It occurs when individuals in a small population
  mate with one another.
• This can occur when a population passes through a
  demographic bottleneck

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Minimum viable population size

• Conservation biologists use these concepts to
  estimate the minimum viable population size or
  rare and endangered species the number of
  individuals such populations need for long-term
  survival.

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Density-dependent population controls

• Population density is the number of individuals
  in a population found in a particular area or
  volume.
• Density-dependent population controls
• Predation
• Parasitism
• Infectious disease
• Competition for resources (mates, food,
  sunlight,)

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Density independent

• Some factors (mostly abiotic) that can kill
  members of a population are density independent.
• Ex. Severe freeze, flood, pollution, fire,

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Several Different Types of Population Change
Occur in Nature

• Stable
• Irruptive
• Cyclic fluctuations, boom-and-bust cycles
• Top-down population regulation
• Bottom-up population regulation
• Irregular

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Humans Are Not Exempt from Natures Population
Controls

• Ireland
• Potato crop in 1845
• Bubonic plague
• Fourteenth century
• AIDS
• Global epidemic

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Ecological Processes
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Ecological Succession

• Primary and Secondary Succession
• gradual fairly predictable change in species
  composition with time
• some species colonize become more abundant
• other species decline or even disappear.

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Primary Succession

• Involves the gradual establishment of biotic
  communities in lifeless areas where there is no
  soil in a terrestrial ecosystem or no bottom
  sediment in an aquatic ecosystem.

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Secondary Succession

• A series of communities or ecosystems with
  different species develop in places containing
  soil or bottom sediment

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Primary Succession

• Bare rock weathers release nutrients for soil
  formation.
• The slow process of soil formation begins when
  early successional plant species or pioneer
  arrive and attach themselves to inhospitable
  patches of rock. Such as lichens, mosses,..
• After hundreds to thousands of years, the soil
  may be deep and fertile enough to store the
  moisture and nutrients needed to support the
  growth of midsuccessional plant species, such as
  herbs, grasses,..

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Primary Succession

• Late successional plant species (mostly trees)
  that can tolerate shade are going to replace the
  midsuccessional plant species.

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Secondary Succesion

• Candidates for secondary succession include
  abandoned farmland, burned or cut forests,
  heavily polluted streams, and land that has been
  flooded.

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Succession Doesnt Follow a Predictable Path

• Traditional view
• Balance of nature and a climax community
• Current view
• Ever-changing mosaic of patches of vegetation
• Mature late-successional ecosystems
• State of continual disturbance and change

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Living Systems Are Sustained through Constant
Change

• Inertia, persistence
• Ability of a living system to survive moderate
  disturbances
• Resilience
• Ability of a living system to be restored through
  secondary succession after a moderate disturbance
  
• Tipping point

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Ecological Succession
Gradual changing environment in favor of new /
different species / communities
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Primary SuccessionGlacier Retreat
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Disturbance

• Event that disrupts an ecosystem or community
• Natural disturbance
• tree falls, fires, hurricanes, tornadoes,
  droughts, floods
• Humancaused disturbance
• deforestation, erosion, overgrazing, plowing,
  pollution,mining
• Disturbance can initiate primary and/or secondary
  succession

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Ecological Stability

• Carrying Capacity maximum number of individuals
  the environment can support

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Ecological Stability - Stress

1. Drop in Primary Productivity
2. Increased Nutrient Losses
3. Decline or extinction of indicator species
4. Increased populations of insect pests or disease
   organisms
5. Decline in Species diversity
6. Presence of Contaminants

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• Which law directed the Secretary of the Interior
  to review every roadless area of 5,000 or more
  acres and every roadless island within National
  Wildlife Refuge and National Park Systems?
• A. Endangered Species Act
• B. Wilderness Act
• C. Lacey Act
• D. National Park Act
• E. Wild and Scenic Rivers Act

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• What are keystone species?
• A. existing in such small numbers that it is in
  danger of becoming extinct
• B. introduced to an environment where it is not
  native, and that has since become a nuisance
• C. likely to become an endangered species within
  the foreseeable future throughout all or a
  significant portion of its range
• D. serve as early warnings of damage to a
  community
• E. presence and role within an ecosystem has a
  disproportionate effect on other organisms within
  the system

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• Who did Roosevelt appoint to head the newly
  created US Forest Service to protect and manage
  the worlds forests?
• A. E.O. Wilson
• B. Aldo Leopold
• C. Robert MacArthur
• D. Stephen Mather
• E. Gifford Pinchot

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• Mutualism benefits
• A) one of the organisms hurts the other
• B) neither of the organisms
• C) both of the organisms
• D) benefits one doesnt hurt the other
• E) only one of the organisms

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• Commensalism
• A) benefits only one of the organisms
• B) benefits both organisms
• C) benefits one, doesnt harm the other
• D) benefits neither of the organisms

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• Biodiversity
• A) decreases with speciation and extinction
• B) decreases with speciation and increases with
  extinction
• C) increases with speciation and extinction
• D) increases with speciation and decreases with
  extinction

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• What is not a pre-zygotic barriers?
• A) behavioral isolation
• B) habitat isolation
• C) mechanical isolation
• D) hybrid isolation

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• Which of the following does species richness not
  depend on?
• A) rate of immigration
• B) island size
• C) distance from mainland
• D) types of species

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• Which is a species on which the persistence of a
  large number of other species in the ecosystem
  depends?
• A) r-strategists
• B) k-strategists
• C) nonnative
• D) keystone

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• What is not characteristic of a k-strategists?
• A) long life
• B) bigger bodies
• C) produce a lot of offspring
• D) produce late in life

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• What is not a predator adaptation?
• A) prey detection
• B) prey capture
• C) eating prey
• D) avoid detection
• E) mass numbers

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