Transcript Chapter 46 PowerPoint

COMMUNITIES AND
ECOSYSTEMS
Chapter 45
A. Community
All populations of organisms living in a
defined area.
Habitat - the physical place where an
organism lives.
What is habitat of a koala?
Niche - the role the organism has in the
community (producer).
What is niche of a koala?
1. Community Interactions
Organisms in communities interact through
competition, symbiosis or predation.
 Interspecific
Competition
Individuals of different species compete
for same resources (food, shelter, space).
What are possible outcomes of
interspecific competition?
 one individual excludes the other
(principle of competitive exclusion)
 they coexist (resource partitioning)
Principle of competitive exclusion
Two species cannot coexist indefinitely in
the same niche.
When present alone,
each has the same
fundamental niche
(all resources a
species is capable
of using).
When present together, each has a different
realized niche (all resources a species
actually uses).
When a new species enters an area,
competition may lead to the extinction
of a native population or species.
Resource partitioning
Competing species can coexist if they use
the same resource in a slightly different
way or at a different time.
 Symbiosis
One species living in or on another.
 mutualism
- both species benefit.
 commensalism
- one
species benefits with no
apparent effect on the
other.
 parasitism
- one
species benefits &
the other is harmed.
 parasitoidism
- one
species benefits & the
other dies as a result.
 Predation
One species (predator)
kills another (prey)
for food.
Prey species often have adaptations that
help them avoid being eaten.
warning coloration
camouflage
mimicry
2. Ecological Succession
Change in the species composition of a
community over time.
 Primary succession
Occurs in an area where no community
previously existed.
 Caused
by volcanoes, road cuts & glaciers.
 Pioneer species are lichens & mosses.
 Takes hundreds of years for a climax
community to develop.
 Secondary
succession
Occurs in an area where a community
is disturbed but not decimated (some
soil & life remain).
 Caused by fires, hurricanes & agriculture.
 Pioneer species are herbs & weeds.
 Occurs faster than primary succession.
Few communities ever reach true climax
conditions.
Lupines
 Lupines
are legumes that add
nitrogen to the soil
 They are pioneer species in volcanic
soil
B. Ecosystem
All the biotic (living organisms) and
abiotic (nonliving environment)
components in a defined area.
 Ecosystems interact.
 All ecosystems require a constant
input of energy.
 Chemicals are cycled within
ecosystems.
1. Energy Flow
Energy flows in one direction through
an ecosystem.
Route of energy flow is determined by an
ecosystem’s trophic structure.
animals that eat carnivores
animals that eat herbivores
animals that eat producers
photo- or chemoautotrophs
Food web - several
species function at more
than one trophic level.
Test Your Cerebrum:
 What
is the niche of (think food
chain) chemoautotrophic bacteria?
Is all of the energy stored by individuals
at one trophic level available to the
next?
No - energy needs of individual, second law
of thermodynamics.
On average, ~10% (2-30%) is transferred.
Energy transfer in Cayuga Lake:
humans store 1.5 kcal
smelt fish store 15 kcal
aquatic herbivores store 150 kcal
algae store 1,500 kcal
Food chains rarely extend
beyond 4 trophic levels.
Other types of pyramids can be used to
describe ecosystems.
 pyramid of numbers - shows number of
organisms at each trophic level.
 pyramid
of biomass - shows total weight
of organisms at each trophic level.
Consider the food chain:
hawk – rabbit – clover.
Clover contains 10 calories of food value,
rabbit 500 calories, hawk 1200 calories.
Each species has a different daily caloric
requirement:
clover: sunlight
rabbit: 100 calories of food
hawk: 300 calories of food
How many clover plants, per day, does it take
to support a hawk?
Hawk needs 300 calories from eating rabbits, so
needs 3,000 rabbit calories available since only
10% moves up the food chain.
3,000 rabbit calories (where food energy is 500
calories per rabbit) means you need 6 rabbits to
feed the hawk.
6 rabbits then need 100 calories of grass
each, or 600 grass calories total.
SO they feed on 6,000 calories of grass
(since only 10% is available to them).
Each clover plant is 10 calories so 600
clover plants = 6,000 calories.
SO it takes 600 clover plants PER DAY to
support one hawk!
2. Biogeochemical Cycles
The biological & geological processes
that recycle chemicals vital to life.
 Water cycle
 Carbon
cycle
 Nitrogen
cycle
N Cycle Quiz
 What
is the original source of nitrogen
on Earth?
 What fixes N from a gas into a usable
form? (2 things)
 In what form do plants take in N?
 How do plants use N?
 How do humans get N and why do they
need it?
 How does N return to the atmosphere?
How do humans interrupt the N Cycle?
 Fertilizer:
producing N fertilizer
started from leftover weapons
Runoff into water from crop fields
Causes birth defects
We overload the nitrate pool
 Industry: air emissions
 Domesticated cattle: farts & burps
(maybe modify with kangaroo
fart/intestinal bacteria DNA)
New N Cycle Study
U
of CA researchers have found that
forest trees can use N found in
sedimentary rock and boost their
productivity.
 Forests over N-rich rock were 50%
more productive than forests over
N-poor rock.
 N was traced using radio-isotopes
 Another factor in the N & C cycles!
 Phosphorous
cycle
Certain elements or compounds taken up
by organisms cannot be metabolized or
excreted.
They accumulate in the organism
(bioaccumulation) and may reach toxic
levels.
 heavy
metals (lead, arsenic, mercury)
 nonbiodegradable pesticides (DDT)
The effects of bioaccumulated materials
are magnified through the food web
(biomagnification).
of DDT
What effect does DDT have on top
predatory birds?
DDT affects their ability to secrete a
firm, calcium-rich eggshell.
DDT Controversy
DDT is used to kill female Anopheles
mosquitos – most carry a plasmodium
parasite that can infect and kill humans. (in
106 nations it is a problem)
In sub-Saharan Africa, about 3,000 children
die EACH DAY from malaria.
In WW II, more people died from malaria
than combat.
DDT Use Today
(read the handout!)
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In 2006 the WHO approved DDT indoor use
in African countries needing malaria control.
Sanaria in MD is the only company in the
world working on a malaria vaccine: 30
scientists in a mini-mall lab. Artesunate is an
anti-malarial drug for early treatment.
ALSO counterfeit drug trade is causing 20%
of the 1 million malaria deaths each year.
Let’s Review with a Problem
 Food
chain:
Bamboo (100 K) – needs sunlight
baby panda (2,500 K) – needs 500 K
snow leopard (6,000 K)–needs 1,500 K
How many bamboo plants, per day,
does it take to support a snow
leopard?
Note: snow leopards really eat goats & mountain sheep 
 You
Solution:
need 6 baby pandas per day to
feed a snow leopard
 6 baby pandas need 3,000 K total
from bamboo
 They feed on 30,000 calories of
bamboo (to get the 10% or 3,000)
 30,000 bamboo K = 300 plants
 It takes 300 bamboo plants per day
to feed a snow leopard