Transcript Population

Populations
A Population
• group of organisms of the
same species living in the
same place at the same time
• Different populations are all connected!
• When one population decreases or increases in
an ecosystem, another population can be
affected!
• Example: The story of the sea otters!
Figure 1.15 page 18
When the sea otters are absent…
Carrying Capacity
•The maximum
population that an
environment can
sustain or support.
•Seychelles Paradise
Flycatcher needs one acre of
mixed forest per breeding
pair. They live on the little
island of Madagascar
Carrying Capacity
• a population remains at its carrying capacity when in
balance (number of individuals added and the number
of individuals that leave or die are the same)
Factors Determining Carrying
Capacity
1. materials & energy: energy, water, carbon, and
other essential nutrients (Abiotic Factors)
Factors Determining Carrying
Capacity
2. Food chains: the population size is limited by
the size of the populations at lower trophic levels
Factors Determining Carrying
Capacity
• 3. Competition: each organism has the same
need as any other; they compete for resources
such as food, water, mates and space
3. A closer look at Competition:
Two types of competition:
• Intraspecific competition: among members of the
same species
– ex: two wolves compete for a rabbit
• Interspecific competition: between different species
– ex: cheetah and lion compete for zebra
4. Population Density: depending on their size,
environment and way of life, different species
have different needs for space
Density Dependent Factors
• Occur when the density has gone
beyond an appropriate level
• Over-population can:
– Increase stress & lead to easier
spread of diseases and parasites
– Increases aggression & causes
parents to neglect offspring
• This causes the population to decrease
Density Independent Factors
• Limits the population- no matter what
the density is.
• Forest fires
• Earthquakes
• Volcanic Eruptions
• Tornadoes
• Floods
To Do:
• Vocabulary Words and questions at the end of
your sheet of notes
• Sheet - Population Terms
• Video - Populations Ecology - Crash Course
Population Growth Curves
Population Growth
• if unlimited resources are
present, growth will be
exponential
• the curve will always be a “J”
curve or an exponential
growth curve
• resources are never
unlimited
• 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)
• Video - The Importance of Predators
• more often what happens is that the resources slowly
decrease, the growth rate slowly increases, and they meet
• this point that they oscillate around is the carrying
capacity of the environment for that particular organism
• this is called an
s-shaped or logistic
curve
To do:
• Notes: Population Growth Curves/
Practice Sheet: Carrying Capacity
• Practice Sheet: Fruit Flies and population
growth
Human Population Growth
What are the causes of this huge increase in the human population?
What are some possible consequences for us?
Our future? (Think: the elk)
To Do:
• Video: 7 Billion
• Current World Population
• Activity: Human Population Growth
• Video – How many people can live on planet
Earth? (45 min)
• Video – How Many People Can Earth Support
(10 min)
• Movie – Future Earth (45 min)
• Movie - World Population to hit 11 Billion in 2100
(45 minutes)
• Movie – Overpopulated (1 hour)
• Video – The Science of Overpopulation (crash
course) – 10 minutes