Download Communities: How Do Species Interact?

Communities: How Do
Species Interact?
Chapter 27
• Succession – the predictable change in the
numbers and kinds of organisms in a particular
area over time.
• Habitation of a completely new environment is
called primary succession.
• Reestablishment of life after serious damage is
called secondary succession.
• Pioneer community – the first community in
a succession.
• Climax community – the long-lived
community at the end of a succession.
• “successional” communities – the
intermediate communities between the
pioneer and climax communities
• Pioneer and successional communities
change over periods of 1 to 500 years.
• Climax communities last for more than 500
years.
Successional communities
• We tend to think primarily of plants since
they are the producers.
• A deer carcass or a pile of dung can also
have successional communities
Why does succession occur?
• Non-climax communities may degrade
their environments
• Species in early successional stages can
– Facilitate succession
– Tolerate succession
– Inhibit succession
• Pioneer communities always facilitate
succession
• The character of a climax community
depends on abiotic factors such as
climate, soil and terrain.
• May depend on the history of the region
– Sequoia forests and fires
Are communities integrated or
individualistic?
• Integrated communities consist of
characteristic species that always interact
with each other in predictable ways
• Individualistic communities are
separate populations that merely inhabit
the same habitat. Every community is
unique.
• Competition between trees?
• Mycorrhizae – soil fungus that supports
the growth of certain plants
• Replanting issues
The First Law of Ecology
• Every species affects every other species.
– Predator – prey interactions
– Herbivore-plant interactions
– Parasite –host interactions
• A parasite consumes only part of its host,
and does not necessarily kill the host.
• A “good” parasite would harm its host as
little as possible so it would have a place
to live.
• A predator usually kills its prey and
consumes most of the prey’s body.
– Use swiftness, intelligence, acute senses and
sharp teeth to obtain food
• Herbivores use patience and a good
digestive system.
How does one keep from being
eaten?
• Camouflage or crypsis – blending into
your surroundings
Plant defenses
• Mechanical defenses:
– Waxy cuticle keeps bacteria and fungi out
– Hairy or sticky leaves discourage tiny
herbivores
– Spines, thorns and prickles fend off larger
predators
Plant defenses
• Chemical defenses – secondary plant
compounds:
– Terpenes –lipids- such as pyrethriods,
essential oils, saponins, and gossypol
– Phenolic compounds – carbon ring
compounds -repel herbivores and pathogens
or attract pollinators and fruit dispersers. Also
lignin and tannins
– Alkaloids –nitrogen containing compounds –
nicotine, atropine, cocaine, morphine,
strychnine and caffeine
– Mustard oil glycosides – cabbage family
Animal chemical defenses
• Bees and wasps inject a powerful acid
• Skunk uses noxious chemicals
• Poison dart frog and the pitohui bird have
deadly toxins in their skin
Warning coloration
• Keeps animals from being attacked
repeatedly by warning off attackers
• These organisms have bright colors and
memorable designs
• Harmless organisms can use mimicry
– Batesian mimicry – when something harmless
(and tasty) mimics something harmful
– Mullerian mimicry – two equally harmful organisms
develop the same warning patterns
• Protects both predator and prey
How do organisms live together?
• Symbiosis – “living together.”
• Parasitism – one species benefits and the
other is harmed
• Predation - one species benefits and the
other is harmed
• Mutualism – lichen – algae and fungus
• Commensalism – one species benefits,
and the other is neither helped nor harmed.
Coevolution
• The acacia and the ants
• Bacteria and plants
• mycorrhizae
Competition
• One organism uses a resource that is in
limited supply, negatively affecting another
species’ ability to survive and reproduce.
• Organisms can compete for:
– Territory
– Prey
– Other resources
• Habitat – the place where an organism
lives, along with the set of environmental
conditions characterize that place.
– Address
• Niche – the way an organism uses its
environment
– occupation
• When there is a limiting resource and
two different species compete directly for
the same resource, the more efficient
species will eliminate the other. – the
competitive exclusion principle
• No two species can occupy the exact
same niche in the same habitat
indefinitely.
How can competing species
coexist?
• Resource partitioning – dividing up the
niche