Transcript 04populations2 3564KB Nov 01 2012 07:59:58 AM

Species
• All individuals that are capable of
interbreeding and produce fertile offspring
A Population
• Group of organisms of
the same species
living in the same
place at the same
time
• Individuals may come
and go, but the
population can remain
the same
• Ex: The flamingos of
Lake Victoria in Africa.
– Assembled for yearly
migration.
• In a food web, each organism survives by
gaining energy from the trophic level below
it.
• The size of the populations are continually
adjusted by the species interactions with
both its food supply and its predators.
Carrying capacity: the largest
population of a species that an
environment can support.
4 factors that determine the
carrying capacity:
1. materials and energy (energy, water, carbon, and
other essential nutrients
2. food chains: the population size is limited by the size
of the populations at lower trophic levels. (Prey
limited by their predators and their food supply).
3. competition: each organism has the same need as
any other. They compete for resources such as
food, water, mates, space).
4. density: depending on their size, environment and way
of life, different species have different needs for
space.
Closer look at competition:
Two types of competition:
1. intraspecific: among
members of the
same species
2. interspecific: between
different species
A closer look at population density:
• Two types of factors can also limit population sizes.
1. density-dependent factors: a factor that gets worse as
the population size increases
* overcrowding
*parasites/disease
*aggression amongst members
* neglect of offspring
• 2. density-independent factors:
does not depend on the size of the population
* forest fire
* flood
* volcano
Population Growth
• Not all populations
grow the same
way...
Population Growth
• Since all organisms
reproduce, populations
tend to grow over time
• If unlimited resources are
present, growth will be
exponential
• It will proceed very quickly
for rapidly reproducing
organisms and more slowly
for slowly reproducing ones
• The curve, however, will
always be a “J” curve or an
exponential growth curve
Generation
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
# of bacteria
1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16,384
32,768
65,536
131,072
262,144
524,288
1,048,576
2,097,152
4,194,304
8,388,608
16,777,216
time
0
15min
30min
45min
1hr
75min
90min
105min
2hrs
3hrs
4hrs
5hrs
6hrs
Population Growth 2
• Resources are never
unlimited, though.
• As population rises,
resources decline.
• If the growth is too rapid,
resources are rapidly
depleted and a population
crash can occur
• This pattern occurs often
with many populations
(including humans)
• For example...
Gypsy moth caterpillar
Population Growth 3
• More often what
happens is that the
resources slowly
decrease, the growth
rate slowly decreases,
and they meet.
• This point that they
oscillate around is the
carrying capacity of the
environment for that
particular organism
S - shaped curve
Population Growth 3 Continued
• Predator-Prey Relationship
– Most food chains show this kind of growth,
where as one organism increases in numbers,
the other will decrease and vice versa.
Human Growth Patterns
What are the causes of the rapid growth of human populations?
What are some possible consequences of this growth pattern?
What will our future look like? (Remember the Reindeer?)
Niche
• The way an organism occupies a position
in an ecosystem, including all the
necessary biotic and abiotic factors
• So for a brown bat,
• Biotic: they eat insects, they compete with
the common nighthawk, and are prey
• Abiotic: where they roost or hibernate,
when they hunt
• Overall, they control insect population!
Adaptations for Niche/Habitat
• Pitcher plants can survive bogs, which
have lots of water and sunlight, but it is an
acidic place and is low in N
• They consume insects (water will sit in
plant and insect will drown and
decompose, providing nutrients)