Transcript Populations - Cathedral High School

Ecology
• Branch of biology that
studies the
interactions between
organisms and their
environment
• All of the
locations on
Earth that can
support life
Biosphere
Abiotic Vs. Biotic
Abiotic
• Non living
factor in an
environment
Examples
• rocks
• water
• sunlight
Abiotic Vs. Biotic
Biotic
• Living factors in
an environment
Examples
• plants
• animals
• bacteria
Levels of life
• Ecologists look at
individual
organisms (level
1)
• organisms that
have similar
characteristics can
mate and produce
fertile offspring
are a species
Population
• Group of
organisms
of a single
species that
live in a
given area
Community
• A collection
of
interacting
populations
in a given
area
Ecosystem
Collection of organisms
that interact with
each other and with
abiotic factors in the
environment
Landscape
a group of
ecosystems which
affect one another
Ecotone (edge
effect)
a transition
area between
ecosystems,
with blended
characteristics
Ecotones are often caused by
underlying environmental gradients
Energy in the
Ecosystem
Organisms
• Autotrophsmake own food
producers
• Heterotrophmust get
nutrients from
outside sources
consumers
Organisms
• Carnivore
• Herbivore
• Omnivore
Organisms
• Decomposers:
break down dead
organisms into
simple molecules
• Scavengers: feed
off dead animals
Trophic Level
• Feeding level on food,
energy, or biomass
pyramid
• Starts with primary
producers
• Ends with highest level
consumer
Food Chain
• One set of organisms moving
up through the trophic levels
• Grass
mouse
fox
hawk
Food Web
• Interconnecting food
chains in an ecological
community
• More than one food
chain
Importance of decomposers
• Because of
decomposers
the same atoms
that made up
the dinosaur's
cells make up
our cells!!
Energy Pyramid
• Illustrates that energy
decreases at each
succeeding trophic level
• Usually square shaped
• Only 10% energy moves
up
Populations
populations
• Group of organisms of the
same species living in the
same location
• Change in population size is
called growth rate (can be +
or -)
Populations Can Grow,
Shrink, or Remain Stable
• Population size governed by
–
–
–
–
Births
Deaths
Immigration
Emigration
• Population change =
(births + immigration) – (deaths +
emigration)
Growing population
• Ideal conditions
• Healthy organisms reproduce faster
• Birth rate is higher than death rate
Species Have Different
Reproductive Patterns
r-Selected species
•
•
•
•
•
Short life
Rapid growth
Early maturity
Many small offspring
Low on trophic level
Characteristics of r-selected
reproductive pattern species
• Unpredictable
environments
• Small body
size
• Mature rapidly
• Reproduce
early
• Short life span
Species Have Different
Reproductive Patterns
K-selected species
•
•
•
•
•
Long life
Slow growth
Late maturity
Few, larger offspring
High on trophic level
Characteristics of K-selected
reproductive species
• Reproduce and
mature slowly
• Long-lived
• Large body
size
Carrying capacity (k)
• Largest number of
individuals that can survive
over long periods of time in a
given environment
• Size of population is
stabilized
Many species grow until capacity is
reached and then level off BUT….
Boom and Bust
Some species exponential growth and
then fast crash
can rise again or wait for
some time before another
boom
Exponential Growth, Overshoot, and
Population Crash of a Reindeer
Density Dependent Limiting
Factors
• Operate more strongly on large
populations
• Usually works on stable populations
Density Dependant Factors
• Disease
• Parasites
• Competition (food,
space)
• Stress
Density Independent
Limiting Factors
• Weather –
storms, fires,
droughts, heat,
cold, floods,
hurricanes
• Human activities –
toxic waste spill,
pesticides, clear
cutting
Coevolution
• the evolution of complementary
adaptations in two or more species of
organisms because of a special
relationship that exists between
them
Examples
Predator/ prey relationship
• Cheetah can run very fast but lacks
stamina
• Gazelles have evolved stamina to
escape cheetahs
Batesian Mimicry
• A harmless species (non poisonous)
resembles a poisonous species
Which butterfly has a bitter
taste?
Mullerian Mimicry
• Two poisonous species look alike
Queen Butterfly and
Monarch are both poisonous
Population Interactions
Influence Abundance
• When populations of different
species interact, the effects on one
on the other may be positive (+),
negative (-) or neutral (0).
• By comparing populations living alone
and together, several types of
interactions can be identified.
FIVE IMPORTANT
INTERACTIONS BETWEEN
TWO SPECIES
•
•
•
•
•
COMMENSALISM (+/0)
MUTUALISM (+/+)
COMPETITION (-/-)
PARASITISM (+/-)
PREDATION (+/-)
The symbols +, - and 0 refer to the effect of one
species on another when both are living together.
Competition
LIVING ALONE LIVING TOGETHER
COMPETITION
0 0
[When both populations live together, abundance of each is lower.]
Law of Competitive Exclusion
• No two species will occupy the same niche
and compete for exactly the same
resources for an extended period of time.
• One will either migrate, become extinct,
or partition the resource and utilize a subset of the same resource.
• Given resource can only be partitioned a
finite number of times.
Resource Partitioning
Competition
• Interspecific - Competition between
members of different species.
• Intraspecific - Competition among
members of the same species.
– Often intense due to same space and
nutritional requirements.
• Territoriality - Organisms defend specific area
containing resources, primarily against members of
own species.
• Resource Allocation and Spacing
Intraspecific Competition
Reindeer on St Mathews Island
7000
6000
6000
5000
Number
• Resource depletion may
result in too many
individuals in the
population. Thus, the
population crashes.
• Reindeer on Saint
Matthews Island died off
as the result of depletion
of lichens (food).
4000
3000
2000
1350
1000
0
1940
42
29
1945
1950
1955
Year
1960
1965
1970
Intraspecific Competition
• A seed company tells
gardeners that
planting plants too
far apart or too
close together will
only produce a few
seeds. Why?
Intraspecific Competition
• Territorial behavior
has evolved in many
species as a response
to intraspecific
competition.
• Male red wing
blackbirds stake out a
territory in defense of
nests and mates.
Interspecific Competition
Predation
LIVING ALONE
LIVING TOGETHER
PREDATION
+
+
[Prey (A) are in greatest abundance when predators are absent.
Predators (B) are in greatest abundance when prey are present.]
Predation
• Feeds directly upon another living
organism
• Prey most successfully on slowest,
weakest, least fit members of target
population.
– Reduce competition, population overgrowth,
and stimulate natural selection.
symbiosis
Intimate living together of members of
two or more species.
• Commensalism - One member benefits
while other is neither benefited nor
harmed.
– Cattle and Cattle Egrets
• Mutualism - Both members benefit.
– Bees and flowers
• Parasitism - One member benefits at the
expense of other.
– Humans and Tapeworms
COMMENSALISM
» LIVING ALONE
A
B
LIVING TOGETHER
A
B
COMMENALISM
0
0
+
0
Species A is more abundant when there are more of
species B present. Species B is not affected by
the presence of A
COMMENSALISM
• The cattle egret
and cattle or other
grazing African
ungulate species.
• The egret benefits
from catching
insects that cattle
“scare-up” while
grazing.
• Cattle unaffected.
COMMENSALISM
• Bromeliads are a
group of flowering
plants that attach
to trees
(epiphytes). They
gain access to
sunlight and catch
water.
• The trees are not
harmed or
benefited.
Mutualism
LIVING ALONE
A
B
LIVING TOGETHER
A
B
MUTUALISM
+
+
[Both populations are found in greatest abundance when together.]
MUTUALISM
• pollination of flowering
plants by an insect or
humming bird.
• The pollinator benefits
from the interaction
by receiving nectar.
• The plant gets its
pollen transferred
from one plant to
another.
MUTUALISM
• The lichen is a
mutualistic association
between a species of
algae and a species of
fungus.
• The fungus retains water
and takes up minerals.
• The algae provides
carbohydrates and other
organic nutrients as the
result of photosynthesis.
Parasitism
LIVING ALONE
A
B
Parasitism
+
-
LIVING TOGETHER
A
B
-
+
Parasitism
• Tick feeds off
mammal
benefitting the
tick but harming
the mammal.
• How would this
ecosystem be
affected if the
butterfly
population
decreased?
• How would this
ecosystem be
affected if the
coyote population
decreased
• How would this
ecosystem be
affected if the
raven population
increased?
Limitations of where a
species can live
1. Physiological stress due to
environmental conditions
2. Competition with other species
3. Predation
4. Parasitism and disease
5. luck
Critical Environmental
Factors
• Single factor in shortest supply
relative to demand is the critical
determinant in species distribution.
– Example: a cactus species can not survive
if temperature drops below 30º F for
more than 12 hours.
Tolerance Limits
• Each environmental factor has both
minimum and maximum levels,
tolerance limits, beyond which a
particular species cannot survive
– Combination of many factors:
temperature range, food availability,
competitors, predators
Tolerance Limits
Limits of Range
1. Physical Barriers
a. Oceans (humans, cattle, marsupials)
b. Mountains (house finch)
c. Ice (cactus, coral reefs)
2. Climatic
3. Altitude
4. Food
5. Water
6. Competitors
Indicators
• If we know the tolerance range of
species, we can deduce the conditions
in the environment based on the
presence of a particular species
– Example: trout require cool, clean well
oxygenated water; if you see an
abundance of trout, what does that tell
you about the environment?
Ecological Niche
• Habitat - Place or set of environmental
conditions where a particular organism lives.
• Ecological Niche
– Role a species plays in a biological community
(e.g. large grassland herbivore)
– Total set of environmental factors that
determines a species’ distribution.
– Generalists - Broad niche
– Specialists - Narrow niche
• When generalists and specialists collide,
generalists usually win.
Generalists
North and
Central America
Omnivorous:
berries,
insects, eggs,
small animals
Specialists
China
Eat Bamboo
Keystone Species
• A keystone species is a species that plays a
critical role in maintaining the structure of an
ecological community and whose impact on the
community is greater than would be expected
based on its relative abundance or total biomass
– Large predators
– Critical food organisms (bamboo and pandas)
– Often, many species are intricately
interconnected so that it is difficult to tell
which is the essential component.
Starfish:
Keystone
Species
Feeds on
muscles and
sea urchins
Muscles will
outcompete other
species
Sea Urchins over
populate: decrease
in corals