Download Species richness and diversity

Chapter 56
Community ecology
Community
a group of different species living
in one area
Species richness
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The number of species in a community
Increases near equator
Relative abundance
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population of a given species in a specific size ecosystem
Compares the percent of each species
EX. Percent of mallards in pond compared to total bird
population
Species diversity

Relates the number of species to the
“relative abundance” of each
Species area effect
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Larger areas usually contain more species
than smaller ones
Evident on islands
Individualistic concept

Community is made of nothing more than
different species that happen to be living
in same area
Holistic concept
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Communities are an integrated unit that
depend on each other for survival.
“super organism”
Keystone Species

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A species that has great influence on
other species in ecosystem
Ex. Sea stars
Trophic cascade
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There is a ripple effect from one eating
level to another when keystone specie is
affected
Orcas increase
otters decease
Urchins increase
Kelp decreases
Ex. Elk eat Aspen trees
Wolves eat elk
 wolves influence vegetation
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Wolf predation near aspen trees increases
Elk change browsing habits
Aspen increase
Community stability

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Resistance to change
Biodiversity increases stability
Biodiversity
55.2 Ecological Niche concept
Niche

The role an organism fills in its community
Niche determined by
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Habitat
Place in food chain
Specific food types
When they eat or hunt
Great horned owl and red tailed
hawk have different niches
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Both eat small
rodents
Both live in same
area
BUT owls hunt at
night, hawks
hunt during day
Fundamental niche
• Potential niche – without any competition
Realized niche
• The part they actually use due to
competition. Usually smaller
Competition exclusion

One Species is eliminated from a
community because of limited resources.
Can not occupy same niche
Example paramecium

P. Caudatum paramecium declines in
presence of other paramecium
Resource partitioning
When several similar species subdivide a
niche for resources
Ex. 5 different warbler species eating
different areas of a tree
Character displacement
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One Phenotype is selected because of
competition
Ex anoles.
on same island there are populations that
eat different things and occupy different
niches,
Character displacement can lead
to different selection models

Directional, stabilizing and disruptive
Symbiosis and community
Interactions
Chp 56.3 - 56.4
Food chain

One specific sequence
of eating levels
Food web – all the consumer
interactions within ecosystem
Trophic levels = eating level

herbivore
Carnivore
Omnivore
Scavenger

Consumer/carnivore that does not hunt
Predation +/
Predator captures and kills prey
Predator Prey adaptations

Predators – camouflage, sharp teeth, web,
infrared sensors, etc
Trap door spider
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Makes camouflaged lair
Angler fish

Spider web
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Green pit viper
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Has infra red heat sensors in pits
Prey - Survival techniques
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camouflage – hide
Aposematic – Advertize poison or
impalatability by coloration
Monarch butterfly
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Larva eats poison milk weed
Monarch advertise poison. Aposematic
Predators adapt to monarch poison
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Black backed oriole
Black headed oriole
Black-eared mouse
Poison dart frogs
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Advertise poison
Aposematic
Camouflage
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Stick insect
Walking leaf insect
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flounder
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Leaf Frog
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Mimicry
One species looks like another
 metalmark moths
mimic jumping spiders.
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Batesian mimicry
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A normal species mimics a poisonous one
Monarch Batesian mimic
Coral snake Batesian mimic
Caterpillar mimics coral snake
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Batesian
Müllerian mimicry
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More than one unpalatable /poisonous
species resemble each other
Bees, wasps and hornets

Mimicry in Butterflies Is Seen here on These Classic “Plates”
Showing Four Forms of H. numata, Two Forms of H. melpomene,
and the Two Corresponding Mimicking Forms of H. erato.
Multiple coral snake mimicry
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Batesian
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Plant / herbivore interactions
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Plants may use physical defenses
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Thorns
Sticky Hairs
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Tough leaves
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chemical defenses secondary
compounds
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Poisonous
Irritating
Bad-tasting
Poisonous
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Mild poison
Daffodils - nausea, vomiting, cramps and
diarrhea
Poison hemlock
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Deadly poison
Irritating chemicals
Hot peppers
have capsaicin
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Bad-tasting
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Bitter melon
mushrooms
Parasitism +/
Like very slow predation. A parasite will
feed on a host but does not result in
immediate death
Endoparasites – Live in host
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Tape worm
Bacteria
Liver fluke
Exoparasites - External
Ticks
Leeches
Lampreys
mosquitoes
Mutualism
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A cooperative relationship where both
species benefit pos/pos
Pollinators
Mutualism
Ex. Acacia trees and fire ants
Acacia trees have thorns that secrete nectar
Ants protect and defend plant from animals
that would eat it
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Mutualism - pollinators
Insects
Birds
and others
Commensalism (+, 0 )
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Benefits one species with little or no effect
on the other
Commensalism
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Birds follow army ants to find food
Cape buffalo
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The buffalo stirs up the insects and the
egrets can then feed on them
parasitism and mutualism.
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Aphids are a major plant pest. They such the sap out of
the plant and their sweet secretions may cause a heavy
growth of sooty mildew on the leaf surfaces. These
same aphids are ‘farmed’ by ants. The ants feed on the
sugar rich secretions of the aphids, move them to better
sites, and protect them from predators.
Competition (-/+) or (+/-)?
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Only one organism will win
Competition exclusion
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One Species is eliminated from a
community because of limited resources.
Can not occupy same niche
Ecological succession 56.5
Succession
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The gradual growth of species in an area
Primary succession
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The development of a community in an
area that has not supported life previously.
Primary succession occurs on
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bare rock,
After volcanic eruption,
sand dunes
Primary succession
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Very SLOW – few minerals available can
take 100s of years
Stages of primary succession
1) Lichens
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mutualism between fungi and algae or
cyanobacteria.
Fungi protect, algae provides food by
photosynthesis
Acids from Lichens turn rock to soil
(chemical weathering)
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Lichens eventually die and become
part of soil
2) Mosses
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Need a little soil. Can also grow on dirty
rock
3) Grasses
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Need thin layer of soil
4) shrubs
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Need thick layer of soil
5) trees
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Need established thick soil layer
Secondary succession
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Occurs when an existing community has
been cleared such as
forest fire
land slide
Climax Community
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Stable end of succession
High bio diversity
High relative abundance
Succession summary
Eutrophication
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“good eating”
The slow process of a lake ecosystem
dying due to over growth of algae which
kills other plants beneath and then the
fish and animal life
Eutrophication
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Mostly from pollution – fertilizers,
detergents
Algae grow on surface from HIGH
nutrients, block light to other plants
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Plants below die
O2 decreases
Fish die
Sediment fills in water
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A stream flowing in can add sediment
faster
Eutrophication of Caspian sea
Biodiversity
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Increases survival of an ecosystem