Download Chapter 2 Ecosystems

Chapter 2 Ecosystems
“When We Try to Pick Out Anything
by Itself, We Find It Hitched to
Everything Else in the Universe.”
John Muir
Ecosystems
• All the organisms living in a certain area,
and their physical environment.
• Often described as isolated units, but
usually do not have clear boundaries.
• Consist of biotic and abiotic factors.
• Biotic factors – all the living parts.
• Abiotic factors – all the nonliving parts.
Abiotic Factors
• Include temperature, sunlight, humidity,
water supply, soil type, and mineral
nutrients.
• In an ecosystem, everything is
interconnected. Change a biotic or
abiotic factor and the whole system can
be disrupted.
Biotic Disruption
• DDT sprayed to kill mosquitoes that
carry malaria.
• Thatch-eating caterpillars multiply,
destroying thatch roofs.
• DDT covered cockroaches eaten by
geckos. Geckos suffer nerve damage,
move slower and are caught and eaten by
cats.
Biotic Disruption (Cont.)
• Cats suffer from high concentrations of
DDT and die.
• Rat populations increase bringing plague
infected fleas.
• Incidence of the plague increase.
• All because we sprayed DDT to kill
mosquitoes.
Abiotic Disruption
• Farmer over fertilizes his fields (increase
in nitrogen and phosphorus).
• Extra fertilizer runs off fields into
adjacent stream and eventually to a
nearby lake.
• Extra nutrients in the lake cause
phytoplankton populations to expand
dramatically. Lake becomes green.
Abiotic Disruption (Cont.)
• Increase in phytoplankton causes increases in
zooplankton.
• Increases in plankton cause dissolved oxygen
(DO) levels to fall rapidly.
• Low DO levels cause massive fish and plankton
die-off.
• Resulting dead material falls to lake bottom
and decomposes (slowly).
• Lake starts to fill in rapidly.
Ecosystem Structure
• The biotic elements of a ecosystem are
organized in a specific manner.
– Organisms – individual living things.
– Species – a group of organisms that can reproduce
together and share common genes.
– Population – a group of individuals of the same
species living in a particular place.
– Community–- a group of interacting populations.
Niche and Habitat
• Niche – an organisms way of life.
Includes all the relationships with its
environment.
• Habitat – where in the environment an
organism lives.
• Niche includes habitat, as well as other
relationships.
Species Relationships
1. Predation – when one organism kills & eats
another.
• Prey – animal being eaten.
• Predator – animal doing the eating.
• Predator-prey relationships can be simple or
complex.
• Sometimes predators can limit a prey
population size, other times they can have no
affect on prey population size.
Species Relationships (Cont.)
1. Competition – a relationship between
species where they attempt to use the
same limited resource.
–
–
Sometimes species can compete w/o coming
into contact w/ each other. Ex: 2 flowers
competing for pollinators.
Competition almost always results in 1
winner and 1 loser.
Species Relationships (Cont.)
3. Parasitism – the relationship between a
parasite and its host.
– Host – the organism that the parasite gets
its nutrition from.
– Parasite – organisms that live in or on
another organism w/o killing it.
– Parasites usually weaken their host making
them susceptible to other things.
Species Relationships (Cont.)
4. Mutualism – a cooperative partnership
between 2 species.
– Both parties have to benefit.
5. Commensalism – relationship where 1
species benefits & the other is not harmed
nor helped.