Ch 35 Population/ Community Ecology

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Ch 35 Population/ Community Ecology

• By Miss Dreher

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35.1 Population Density

• Population density is the number of individuals
  of a particular species per unit area or volume.
•  
• Examples
• 35 alligators per square km of a swamp
•  1,000,456 bacteria per cm2 of an agar plate
• 120 earthworms m2 of soil

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Population density problems

• On rare occasions you can count all the
  individuals in
• a population, such as the number of beech trees
  in a
• forest measuring 50 square kilometers (km2).
•  
• Population density Individuals 1000 trees
  20 trees
  
• Unit area
  50 km2 km2
•  Population density is a helpful measurement for
  comparing populations in different locations.

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Population Dispersion
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35.2 There are limits to a populations growth

• Exponential growth growth of a population that
  multiplies by constant factor
• Limiting factorcondition that restricts a
  populations growth, such as space, disease and
  food availability.
• Carrying capacity number of organisms in a
  population that an environment can maintain.

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Exponential Growth

• Figure 35-5This table shows how many bacteria
  are in a population that doubles every 20
  minutes. The graph is another way to show the
  same data.

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CARRYING CAPACITY

• Figure 35-6Before the early 1900s, hunting kept
  this population of fur seals below the carrying
  capacity of the environment. Then, after hunting
  was reduced, the population grew almost
  exponentially for two decades. The population
  began to level off as it reached the carrying
  capacity.

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Changes in Population Size

• Growth factors (increase in pop.)
• Immigration individuals moving into a population
• Births
• Shrinking factors (decrease in pop.)
• Emigration individuals moving out of a
  population
• Deaths

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Exponential Growth J curve

• Early phase of growth
• High availability of resources
• Little competition
• Little predation

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Logistic Growth S curverepresent Carrying
capacity

• Limits on growth appear
• Competition for resources
• Predation
• Parasitism
• Illness

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35.3 Human Population
Growth

The human population is now growing at a rate of
about 3 people/second or 260 thousand/day or
1.8 million per week or 93 million/year Earths
Carrying Capacity about 50 Billion
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HUNGER
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Human Population Growth
Are humans in exponential or logistic growth?
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35.4 Interactions in Communities Competition
Between Species

• An elephant, cannot survive without other
  organisms.
• elephant ?herd of elephants (population)? an
  elephants community
• An elephants community gazelles, giraffes,
  birds, ants, beetles, fungi, bacteria, grasses,
  trees
• Members of a population compete for limited
  resources in the environment.
• -Competition within a single species limits the
  growth of the population.
• Interspecific competition when two or more
  species rely on the same limited resource
• (competition between 2 different species)
• exampleduring times of drought in an African
  savanna community, grasses may be in short
  supply, and competition becomes intense.

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Competitive Exclusion

• Competitive exclusion One species succeeding
  over another, when the growth of both species is
  limited by the same resource.
• Figure 35-14Two similar species may each thrive
  in separate locations, but one may exclude the
  other when they are placed together. The results
  of an experiment with two Paramecium species
  demonstrate this principle of competitive
  exclusion.

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NICHE

• Niche a unique living arrangement of an
  organism defined by its living place (habitat),
  its food sources, the time of day it is most
  active, and other factors  
• The local loss of a species is likely to occur if
  2 species have niches that are very similar
• niches are rarely identical.
• Example one lizard in a tropical forest feeds
  on insects in low shrubs, while a similar lizard
  may eat insects high in the trees.
•  

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Predation

• Predation an interaction in which one organism
  eats another.
• The lion attacks and eats an injured zebra or an
  egret catches and eats a fish.
• Predator the organism that kills/ eats the
  prey.
• Prey the organism that gets eaten.
• eating and avoiding being eaten are important to
  survival,
• many effective adaptations have evolved in both
  predators and prey.

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Predator/ Prey
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• Predator Adaptations
• fast and agile
• camouflage
• teaming up in packs acute senses
• claws, teeth, fangs, and stingers

Ex. Rattlesnakes locate their prey with
heat-sensing organs located between each eye and
nostril.
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• Prey Adaptations
• retreat to safe locations
• flee from predators
• camouflage to hide
• "warning coloration" is a caution to predators.
• mimicry -look like organisms that are poisonus or
  dangerous.
• Plants have poisonous chemicals and structures
  such as spines and thorns.

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Warning Coloration
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Monarch w/ warning coloration
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Viceroy Butterfly- mimics Monarch
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Symbiotic Relationships

• Symbiotic relationship is a close interaction
  between species in which one of the species lives
  in or on the other.
• 3 main types of symbiotic relationships
  parasitism, mutualism, and commensalism.
• 1.) Parasitism is a relationship in which the
  parasite obtains its food at the expense of the
  host.
• Usually the parasite is smaller than the host.
  (blood-sucking mosquitoes and tapeworms)

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Ticks
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• Mutualism both organisms benefit from the
  symbiotic relationship.
• Your large intestine is inhabited by millions of
  bacteria.
• The bacteria benefit by having a warm, moist home
  and food.
• Intestinal bacteria produce vitamin K. Vitamin
  K is essential for blood clotting.
• Both you and the bacteria benefit from this
  relationship.

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Mutualism
                                                
                              Pair of Coleman
Shrimp on fire urchin
                                                
                                  Manta Ray with
Remoras

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•  
• Commensalism is a relationship in which one
  organism benefits, while the other organism is
  neither harmed nor helped significantly.
• Example
• A spider crab may place seaweed on its back. The
  crab benefits by being camouflaged from its
  predators. The seaweed is not affected.
• commensalism in nature is rare, since most
  interactions harm one species (parasitism) or
  help both species (mutualism) to some degree.

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Commensalism
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35.5 Disturbances are common in communities
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Ecological Succession

• Ecological succession. Series of changes in the
  species of a community, often followed by a
  disturbance.
• Primary Succession- process by which a community
  arises in a lifeless area that has no soil
• barren ground ?lichen/mosses? grass? shrubs? pine
  trees ? hardwood trees
• Examples
• Forest devastated by a fire, or volcano
• new islands created by erupting volcanoes
• bare rock left behind a retreating glacier.

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Primary Succession

• The establishment and development of an ecosystem
  in an area that was previously uninhabited

Lichens and mosses
Grasses And small shrubs
Large shrubs and small trees
Large trees
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Primary Succession
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Surtsey A Case Study

• The island of Surtsey formed by volcanic eruption
  off of the coast of Iceland during the period
  from 1963 - 1967

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Surtsey Post Eruption
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Surtsey Today
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Secondary Succession

• Secondary succession when a disturbance damages
  an existing community but leaves the soil intact
• Grasses ? shrubs? trees similar to the original
  forest.
• Example when a forested area is cleared for
  farming and then abandoned.

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Secondary Succession

• The recovery of a damaged ecosystem in an area
  where the soil was left intact

Fireweed
Sequoia seedling
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Case Study Yellowstone National Park

• 1988 Devastating forest fires burn much of
  Yellowstone National Park.

Photo National Parks Service
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Yellowstone National Park

• 1988 Park map
• showing areas
• (1.6 million acres)
• burned by the
• series of fires.

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Yellowstone National Park

• 1988 fires The immediate aftermath.

Photo National Parks Service
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Yellowstone National Park

• One year after the fires
• Note the appearance of fireweed

Photo National Parks Service
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Yellowstone National Park

• Ten years after the fires (1998)

Photo National Parks Service
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Yellowstone National Park

• Twenty years after the fires (2008)

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Case Study - Chernobyl

• In April, 1986, a nuclear power plant in the
  former USSR experienced a core meltdown and a
  catastrophic release of radioactivity into the
  environment.

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Chernobyl

• Surrounding towns and villages had to be
  immediately, permanently abandoned.

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Chernobyl Twenty Years Later
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Chernobyl Twenty Years Later
Pripyat town square.
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Chernobyl Twenty Years Later
Pripyat Soccer Stadium opened in 1986.
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Chernobyl Twenty Years Later
A local highway.
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Secondary succession trees are colonizing
uncultivated fields and meadows

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Human Activities and Species Diversity

• humans have had the greatest impact on
  communities worldwide.
• 60 Earth's land is used by humans, mostly as
  cropland or rangeland.
• Human disturbances have a negative effect on
  species diversity
• Clearing the Land
• for lumber
• land for farming
• Land for building.
• paved over or eventually recolonized by weeds and
  shrubs, as in abandoned city lots.

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Invasive Species
Courtesy www.lab-initio.com
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Invasive Species

• Introduced species any organism that was
  brought to an ecosystem as the result of human
  actions
• Invasive species A species that takes advantage
  of an unoccupied niche, or that successfully
  out-competes native species

Kudzu an invasive vine
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Introduced Species

• Introduced species are organisms that humans
  move from the species' native locations to new
  geographic areas, either intentionally or
  accidentally (exotic species).
• Kudzu, a Japanese plant planted widely in the
  American South (1930s) to help control erosion.
  especially along irrigation canals. But kudzu
  soon grew out of control, taking over vast
  expanses of landscape.
• Some introduced species gain a foothold and may
  disrupt their new community.
• Some introduced species prey on native species or
  outcompete native species
•  

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Invasive species

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U.S. Invasive Aquatic Plants
Partial list Brazilian Waterweed Caulerpa,
Mediterranean Clone Common Reed Eurasian
Watermilfoil Didymo Giant Reed Giant Salvinia
Hydrilla Melaleuca Purple Loosestrife Water
Chestnut Water Hyacinth Water Lettuce Water
Spinach
Hydrilla
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U.S. Invasive Aquatic Animals
Partial list Alewife New Zealand Mud Snail
Northern Snakehead Asian Carps Nutria
Asian Swamp Eel Quagga Mussel Bullfrog
Round Goby Chinese Mitten Crab Rusty
Crayfish Eurasian Ruffe Sea Lamprey European
Green Crab Sea Squirt Flathead Catfish Spiny
Water Flea Lionfish Veined Rapa Whelk
Zebra Mussel
Zebra Mussel
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U.S. Invasive Invertebrates
Partial list Africanized Honeybee Asian Citrus
Psyllid Asian Long-Horned Beetle Asian Tiger
Mosquito Cactus Moth Emerald Ash Borer
European Gypsy Moth European Spruce Bark
BeetleFormosan Subterranean Termite Giant
African Snail Glassy-Winged Sharpshooter
Hemlock Woolly Adelgid Light Brown Apple Moth
Mediterranean Fruit Fly Mexican Fruit Fly Pink
Hibiscus Mealybug Red Imported Fire Ant Russian
Wheat Aphid Silverleaf Whitefly Sirex Woodwasp
Soybean Cyst Nematode
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U.S. Invasive Vertebrates
Partial list At Risk of Widespread Brown
Tree Snake IntrusionCane Toad
Constrictor snakesEuropean Starling Boiga
snakesWild Boar Gambian pouch rat House
Sparrow Nutria
European Starling
Cane Toad
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U.S. Invasive Plants
Autumn Olive Beach Vitex Canada Thistle Chinese Tallow Cogongrass Common Teasel Dalmatian Toadflax Diffuse Knapweed Downy BromeGarlic Mustard Giant Hogweed Hairy Whitetop Houndstongue Japanese Honeysuckle Japanese Knotweed Johnsongrass Kudzu Leafy Spurge Medusahead Mile-A-Minute Weed Multiflora RoseMusk Thistle Old World Climbing Fern Oriental Bittersweet Purple Star Thistle QuackgrassRussian Knapweed Russian OliveSaltcedarSt. Johnswort Scotch Broom Scotch Thistle Spotted Knapweed Tree-of-Heaven Tropical Soda Apple Whitetop Yellow Star Thistle Yellow Toadflax
Yellow Star Thistle
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U.S. Invasive Microbes
Animal Pathogens Avian Influenza Exotic
Newcastle Disease Fowlpox Viral Hemorrhagic
Septicemia West Nile Virus Whirling Disease
Plant Pathogens Citrus Canker Citrus Greening
Plum Pox Southern Bacterial Wilt Soybean Rust
Sudden Oak Death
West Nile Virus
Citrus Canker
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Kudzu vines
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Zebra Mussels clogging pipes
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35.5 DISTURBANCES
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Definitions

• Bioaccumulation is the process by which
  substances not readily broken down or excreted
  can build up and be stored in living tissue
  (usually in fatty tissue.)
• Biomagnification is the process by which
  substances become more concentrated in the bodies
  of consumers as one moves up the food chain
  (trophic levels).

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Case Study PCBs

• PCBs, or polychlorinated biphenyls, are a group
  of man-made chemicals.
• Introduced in 1929 and widely used in electrical
  transformers, cosmetics, varnishes, inks,
  carbonless copy paper, pesticides and for general
  weatherproofing and fire-resistant coatings to
  wood and plastic.
• The federal government banned the production of
  PCBs in 1976
• PCBs can effect the immune system, fertility,
  child development and possibly increase the risk
  of certain cancers

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Case StudyDDT

• DDT is a pesticide that was widely used until
  being banned in the U.S. in 1972
• DDT accumulates in living tissue, particularly in
  fat tissue
• High concentrations in some bird species caused
  failure of eggs by thinning the shells

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Case StudyMethyl Mercury

What makes methylmercury so dangerous?
Methylmercury is rapidly taken up but only slowly eliminated from the body by fish and other aquatic organisms, so each step up in the food chain (bio)magnifies the concentration from the step below. Bioaccumulation factors (BAF's) of up to 10 million in largemouth bass have been reported for the Everglades.Fish-eating birds, otters, alligators, raccoons and panthers can have even higher bioaccumulation factors.
U.S. Department of the Interior, U.S. Geological
Survey, Center for Coastal GeologyThis page is
http//sofia.usgs.gov/sfrsf/rooms/mercury/achilles
_heel/cause.html
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Mercury Health Effects