Transcript Communities and Ecosystems

Communities &Ecosystems
Community
• Define: _______________________________
___________________________________
Population- group of organisms
of the same species
Habitat- place, location, defined
by its abiotic and
biotic features.
Ecosystem
• Ecosystems are dynamic interactions between plants,
animals, and microorganisms and their environment
working together as a functional unit.
• The water, water temperature, plants, animals, air, light
and soil all work together.
• Examples of Ecosystems: _______________________
______________________________________________
A community includes all the organisms
inhabiting a particular area
 Community Ecology is concerned with
factors that
• influence species composition and
distribution of communities and
• affect community stability.
Interspecific interactions are fundamental to
community structure
• 3 types of Symbiosis:
1.
2.
3.
• Predation
• Herbivory
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Types of Symbiosis
Mutualism benefits both partners
 Reef-building corals and photosynthetic dinoflagellates
illustrate the win/win nature of mutualism. Photosynthetic
dinoflagellates
• gain shelter in the cells of each coral polyp,
• produce sugars used by the polyps, and
• provide at least half of the energy used by the coral animals.
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Competition may occur when a
shared resource is limited
 An ecological niche is the sum of an organism’s use of
the biotic and abiotic resources in its environment.
 Interspecific competition occurs when the niches of two
populations overlap.
 Competition lowers the carrying capacity of competing
populations because the resources used by one population
are not available to the other population.
Competition between members of
the different species can result in:
• Extinction (competitive exclusionG.F. Gause experiment)
• Subdividing an essential
resource (Resource Partitioning)
MacArthur'
s Warblers
Competition may lead to an altered niche.
Theoretical Niche = Fundamental Niche
Actual Niche = Realized Niche
Effect of competition: COMPETITIVE EXCLUSION
Paramecium caudatum
Species competing for the
same, limited resources will
result in one being
more successful &
ultimately eliminating the
other
both sp. grown together
Paramecium aurelia
Effect of competition:
RESOURCE
PARTITIONING
Bristly
foxtail
Indian
mallow
Smartweed
Competitors use
resources in different
ways or at different
times to minimize
competition & allow
for coexistence
Ex: competition for soil
nutrients= roots different
lengths!
Predation, another form of community interaction,
leads to adaptations in prey species
• Predation benefits the predator but kills the prey.
• Prey adapt using protective strategies that include
– ____________________
– ____________________
– ____________________
PREY DEFENSES
Camouflage
cryptic coloration
Warning
Aposematic coloration
Disruptive
Chemicals
Secondary Compounds
PREDATOR RESPONSES
adaptations that overcome prey defenses
Examples- behaviors, stealth,
camouflage…
poisonspraying
tail
http://www.sciencefriday.com/program/archives/201108
053
PREY DEFENSES (con’t)
Batesian
Mimicry
Types of
mimicry
Muellerian Mimicry
Stinging bee
Stinging wasp
Stinging fly
Herbivory leads to diverse adaptations in plants
• Herbivores and plants undergo coevolution,
– a series of reciprocal evolutionary adaptations in two
species,
– in which change in one species acts as a new selective
force on another.
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Coevolution: the evolutionary arms race
Coevolution is the mutual evolutionary influence between two
species (the evolution of two species is dependent on each other).
Each of the species involved exerts selective pressure on the
other.
• Moth collects pollen
• Flies to another
flower
• Pierces the ovary
• Lays eggs inside
ovary
• Pollinates that flower
• Seeds develop
• Moth eggs hatch
• Larvae eat a few
seeds
BOTH ORGANISMS
REPRODUCE!
EVOLUTION CONNECTION: Herbivory leads to
diverse adaptations in plants
• A plant whose body parts have been eaten by an
animal must expend energy to replace the loss.
– Thus, numerous defenses against herbivores have
evolved in plants.
– Plant defenses against herbivores include
• spines and thorns and
• chemical toxins.
“Prey”/Plant Defenses
Poison ivy
hemlock
Parasites and pathogens can affect
community composition
• A parasite lives on or in a host from which it obtains nourishment.
– Internal parasites include nematodes and tapeworms.
– External parasites include mosquitoes, ticks, and aphids.
• Pathogens are disease-causing microscopic parasites that include
– bacteria,
– viruses,
– fungi, or
– protists.
• Non-native pathogens can have rapid & dramatic
impacts.
– The American chestnut was wiped out by a protist
(early 1900’s).
– A fungus-like pathogen is currently causing sudden
oak death on the West Coast.
– Emerald ash borer is currently
threatens to kill billions of ash trees in North America
• Non-native pathogens can cause a decline of the
ecosystem.
Species diversity includes relative abundance and
species richness
• Species diversity is defined by two components:
1. Species richness, the number of species in a
community, and
2. Relative abundance, the proportional representation
of a species in a community.
• Plant species diversity in a community affects the
species diversity of animals.
• Species diversity has consequences for pathogens.
• Low species diversity is characteristic of most
modern agricultural ecosystems.
Figure 37.10A
Woodlot A
Keystone species
have a disproportionate impact on diversity
• A keystone species
– is a species whose impact on its community is larger
than its biomass or abundance indicates and
– occupies a niche that holds the rest of its community
in place.
• Examples of keystone species in marine
ecosystems include
– Pisaster sea stars and
– long-spined sea urchins.
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KEYSTONE SPECIES
A species with a very strong or far-reaching
impact
on a community
• Important to food web
• Alters the environment- provide
benefit to other organisms
Disturbance is a prominent feature of most
communities
• Disturbances
– are events that damage biological communities and
– include storms, fires, floods, droughts, overgrazing, or
human activity.
– The types, frequency, and severity of disturbances
vary from community to community.
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Primary SUCCESSION
pioneer species colonize new areas
• Opportunistic: high dispersal rate, grow & mature quickly,
produce many offspring
• Tolerant
• Build and improve soil
• Ex: moss, lichens, grasses
Secondary SUCCESSION
• A disturbed area recovers
• Abandoned farming fields, forest fire, volcanic eruption,…
• Characteristics of soil control rate of recovery
Figure 37.12B
Annual Perennial
plants plants and
grasses
Shrubs Softwood trees Hardwood
such as pines
trees
Time
Invasive species can devastate communities
• Invasive species
– are organisms that have been introduced into non-native
habitats by human actions and
– have established themselves at the expense of native
communities.
– The absence of natural enemies often allows rapid population
growth of invasive species.
• Examples of invasive species include the deliberate introduction of
– rabbits into Australia and
– cane toads into Australia.
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Invasive Species in Australia
• Rabbits introduced as a game species.
– No predators
– Prolific breeders
– Destroyed farm and grazing land
• Cane toad introduced for biological control of
beetles in sugar cane fields
– Skin toxic to other animals
– Did not eat the beetles
Invasive Species in VA
• Kudzu
– Introduced accidentally
from Exposition in 1876
– Grows rapid,
overgrows other plants
• Hydrilla
– released in the 1960s from
aquariums into waterways
in Florida
– Clogs boating channels
You should now be able to
1.
2.
3.
4.
5.
Define a biological community. Explain why the study of
community ecology is important.
Define interspecific competition, mutualism, predation,
herbivory, and parasitism, and provide examples of each.
Define an ecological niche. Explain how interspecific
competition can occur when the niches of two populations
overlap.
Describe the mutualistic relationship between corals and
dinoflagellates.
Define predation. Describe the protective strategies potential prey
employ to avoid predators.
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You should now be able to
6.
Explain why many plants have chemical toxins, spines, or
thorns. Define coevolution and describe an example.
7. Explain how parasites and pathogens can affect community
composition.
8. Describe the two components of species diversity.
9. Define a keystone species.
10. Explain how disturbances can benefit communities. Distinguish
between primary and secondary succession.
11. Explain how invasive species can affect communities
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