Transcript Chp 5 Niche and Population notes

CHAPTER 5 RAD GUIDE:
INTERACTIONS IN THE
ECOSYSTEM
June 2, 2016
How is niche different than habitat?
Habitat is place where a population lives
 Niche is a species’ role in the habitat

How is a species’ niche defined?

Defined by the biotic (food sources) and
abiotic (temp) factors
How is competitive exclusion related to
the concept of the niche?
Competitive exclusion solidifies the fact
that each species has a unique niche
 If 2 lizard species eat the same size insect,
they will compete for insects of that size
b/c they occupy the same niche and live in
the same habitat
 Could lead to extinction of one of the
populations if a different habitat or new
food source is not found

Hi Anthony!
ARE YOU WIDE
AWAKE
TODAY??
THIS IS THE EXTINCTION OF 1 POPULATION
IN 1 PLACE, NOT THE EXTINCTION OF THE
WHOLE SPECIES!!
 Joseph Grinnell formulated the principle of
competitive exclusion in 1904: "Two species
of approximately the same food habits are not
likely to remain long evenly balanced in
numbers in the same region. One will crowd
out the other"

Fundamental Niche vs. Realized Niche


Warblers who live in branches of
spruce trees have learned to coexist
by eating in different parts of the tree
(narrowing their niche….realized
niche) even though technically they
could all occupy the whole tree
(fundamental niche).
Creates generalized species &
specialized species (ex. Koalas eat
eucalyptus trees)….depends on how
large the niche is…specialized species
are more susceptible to extinction
Predator vs Prey




Keystone Species- predator that promotes a great niche
diversity in its habitat
American Ecologist Robert Paine showed how predators
help form niches. Paine removed the dominant predator, the
sea star (star fish) from tidepools. The number of mussels
then increased until the mussels had “outcompeted” many
other species living in the tidepools. WITHOUT THE STAR
FISH, THE # OF SPECIES LIVING IN THE TIDEPOOLS
DROPPED FROM 15 TO 8.
Keystone Species
Good videoclip
What might happen to an ecosystem if
all the carnivores were removed?

Diversity at all trophic levels would
decrease because herbivore populations
would go uncontrolled and competitive
exclusion might occur
VOCABULARY
1.
2.
3.
4.
5.
Niche:
See notes above for definition!
Competitive Exclusion: extinction of a
population due to direct competition with
another species for a resource in a niche
Predator: organism that actively hunts other
organisms
Prey: organism upon which a predator feeds
Keystone predator: predator that causes a
large increase in diversity of its habitat
How does a species adapt to its niche?

Evolution changes the characteristics of a
species to adapt it to the niche
What’s convergent evolution & how
does it relate to niche? Example?





Independent development (NO COMMON ANCESTOR)
of similar adaptations (called analogous traits) in two
different species with similar niches
Relates to niches because similar niches would require
similar characteristics (both niches require flying)
Examples: wings of birds & bats
Birds vs. Bats
convergent evolution videoclip
Species can shape each other over time.

Two or more species can evolve together through
coevolution.
 evolutionary
paths become connected
 species evolve in response to changes in each other
What’s coevolution & how does it
relate to niche? Example?
Species that interact closely may become
adapted to one another (influence each other)
 Relates to niches because two different species
evolve to share the same niche
 Examples: Acacia tree & ants, bee & flower
 Acacia trees and ants
 coevolution videoclip


Coevolution can occur in competitive relationships,
sometimes called evolutionary.
VOCABULARY
1.
2.
3.
Evolution: a gradual change in a
population of organisms over time
Convergent Evolution:
See notes
above for
Coevolution:
definition!
POPULATION SIZES
Charles Darwin said, “There is no exception to the rule that
every organic being naturally increases at so high a rate, that,
if not destroyed, the Earth would soon be covered by the
progeny (descendants) of a single pair.”
How does a population of organisms
grow?
Produce more viable offspring than simply
replacing parents (2 +)
 Darwin felt overproduction causes
competition for resources, which causes
selection of the most favorable adaptations.

What is exponential growth & what
conditions do populations grow this way?
Population growth in which the rate of growth
in each generation is a multiple of the previous
generation
 If it has perfect environment, any population can
grow exponentially
 Ex. Darwin felt 1 pair of elephants could
produce more than 20 million elephants in 750
yrs if the elephants were not limited by food
or other resources.

Exponential Growth (continued)

Populations can show exponential growth (limited to
short periods) but limited resources will soon
slow/limit the growth
Explain how carrying capacity works &
how it affects population size.
Carrying capacity is when # of births = # of
deaths (maximum # of individuals an
ecosystem can support)
 Population stops growing when reaches
carrying capacity

What factors limit (LIMITING FACTORS)
the growth of population?
Density-Independent



Climate-hot/cold
Human disturbancetoxic waste, spills,
pesticides,
deforestation
Natural disasters-fires,
floods, tornadoes
Density-Dependent






Food Supply
Water Supply
Predation
Living Space
Disease
Parasitism
What do the growth curves look like for a densityindependent & density-dependent populations?
Density-Independent
Density-Dependent

What about the human population?




Growth curve has long been an exponential one…
Possible b/c of many factors: advances in
agriculture, technology, energy development,
transporation, medicine, etc.
NO POPULATION OF ORGANISMS CAN GROW
EXPONENTIALLY FOREVER!
Human population must level off as the planet’s
resources become fully utilized.
Current rates put the human population at 7.125 billion
(2013)…estimated to reach 8 billion by 2024
Human Population Stats






China- 1.39 Billion people (9.5 million square km)
India- 1.27 Billion people (3.2 million square km)
United States- 322 million people (9.6 million square
km)
Indonesia -252 million people (1.9 million square km)
Brazil- 202 million people (8.5 million square km)
Human Population video clip
VOCABULARY
1.
2.
Exponential growth:
Carrying capacity:
See notes
above for
definition!