Populations have characteristics like size, density, and age distribution that can vary over time. Populations can be categorized into three types based on their growth: expanding, stable, or declining. Biotic potential refers to the maximum growth rate of a population with unlimited resources and no predators or environmental resistance. Factors like litter size, breeding frequency, reproductive span, and survival rate determine a species' biotic potential. Populations cannot grow exponentially indefinitely due to environmental resistance and eventually reach carrying capacity, where growth stabilizes.

1. Changes in the
Ecosystems

2. Populations
• There are different characteristics that refer to the group of
individuals or population in an ecosystem:
• Size of the population (Number of individuals)
• Density (Number of individuals/km2)
• Age distribution

3. Changes in Populations
• Population size, density or age distribution may vary.
Populations are represented with population pyramids.
• We find 3 types of populations according to their growth:

5. Biotic potential
• Populations vary in their capacity to grow.
The maximum rate at which a population can increase when
resources are unlimited and environmental conditions are ideal is
termed the population's biotic potential.
Unlimited resources
Maximum growth
rate
No predators

6. Variations in biotic potential
• Each species will have a different biotic potential due to
variations in :
1. “Litter size“: how many offspring are born each time.
2. The breeding frequency : how often an individual can
reproduce.
3. The species' reproductive span: how long an individual is
capable of reproducing.
4. Survival rate: how many offspring survive to reproductive age.

7. Factor Rabbit Horse
Litter size High: 4-10+ Low: 1
Breeding frequency High: 30 days Low: 11 month
Reproductive span Short Long
Survival rate Poor Good
Biotic High Low
Potential

8. Unrestricted growth or J growth
• Ilimited resources.
• However, there are
always limits to
population growth in
nature. Populations
cannot grow
exponentially
indefinitely.

9. Environmental resistance
• Exploding populations always reach a size limit imposed by the
shortage of one or more factors such as water, space, and
nutrients or by adverse conditions such as disease, drought
and temperature extremes.
• The factors which act jointly to limit a population's growth are
termed the environmental resistance.
https://www.wou.edu/las/physci/ch371/lecture/popgrowth/carrying.htm

10. S growthof the populationor Logisticgrowth
• Resources are limiting.
• The population increases until
it reaches it’s carrying capacity
Maximum number of
individuals of a given species
that an area's resources can
sustain indefinitely without
significantly depleting or
degrading those resources.
• Below carrying capacity,
populations normally increase.
• Above carrying capacity
populations usually decrease.
https://www.wou.edu/las/physci/ch371/lecture/popgrowth/carrying.htm

11. Logistic growth

12. Population Growth

13. Regulating factors
• A factor that keeps population size at equilibrium is known as
a regulating factor.
• Population size decreases above carrying capacity due to a
range of factors depending on the species concerned, but can
include insufficient space, food supply, or sunlight.
• The carrying capacity of an environment may vary for different
species and may change over time due to a variety of factors,
including: food availability, water supply, environmental
conditions and living space.