Population growth

Ronaldo C. Francisco
Florentino Senior Torres High School
SDO Manila
Population
Growth:
Biotic Potential
and
Environmental
Resistance

Mabuhay!!!
I'm Captain Planet
And I will be Joining you in
learning the factors that
affects Population Growth
rfrancisco_populationgrowth

Please be informed that
our discussion will be
guided by this outline
TOPIC OUTLINE
a. Biotic Potential and Environmental Resistance
b. Population Distribution/Dispersal patterns
c. Population Size and Density

Remember

Define the
following
terms• Population
• Population Growth
• Immigration
• Emigration

For a head start
please answer the
following questions
• What is population explosion?
• What causes population explosion?
• Is there a human population
explosion?

a biological community of interacting
organisms and their physical
environment
What is an ecosystem?

Biotic Potential measures how
well a species has adapted to
survive (by defense mechanisms,
resistance to adverse conditions,
migration, and seed dispersion)
Did you know that the rate of population
growth is dependent on BIOTIC POTENTIAL
and ENVIRONMENTAL RESISTANCE?

Environmental resistance is
adverse biotic and abiotic factors
that raise the death rate of a
population. Example: predators,
parasites, unfavorable
temperature, and lack of water.
Did you know that the rate of population
growth is dependent on BIOTIC POTENTIAL
and ENVIRONMENTAL RESISTANCE?

The combination of the biotic and abiotic factors
determines the CARRYING CAPACITY of an ecosystem.
Carrying capacity is the optimal maximum density of a
population that can be supported by a defined space. If
the population approaches or exceeds the carrying
capacity, competition for resources will set limits to the
population density.
Now, lets talk about facts

Population explosion is a result
when all conditions favorable to the
population occurs for an extended
period of time.
Now, lets talk about facts

1. What are the factors that affect
the population growth?
2. Explain, Carrying Capacity
3. What is population explosion?
Ooopsss! Lets review first

DISTRIBUTION/DISPERSAL is the pattern of spacing among
individuals of the population. Three types:
a. CLUMPED dispersion - individuals aggregate in patches; may be
influenced by resource availability and behavior (efficiency in
hunting, guarding the young).
b. UNIFORM dispersion - individuals are evenly distributed; May
be influenced by social interactions such as territoriality.
c. RANDOM dispersion - The location of one individual is
independent of others members of the population.
Now, lets continue learning

Population size is the number of individuals in
a population.
For example, a population of insects might
consist of 100 individual insects, or many
more. Population size influences the chances
of a species surviving or going extinct.
Generally, very small populations are at
greatest risk of extinction.
How about Population size
and Density

Population density is the average number of
individuals in a population per unit of area or
volume. For example, a population of 100
insects that live in an area of 100 square
meters has a density of 1 insect per square
meter.
How about Population size
and Density

POPULATION GROWTH is due to a higher birth
rate than death rate. New individuals are
recruited into the population through growth
and immigration. The maturation of newborn
into the adult breeding population, is
considered a more important basis of the
potential population growth.
And now Population
growth…

Population growth models discusses the rate at which the density of a
population increases through time.
At this point let me share with you the
population growth models
Exponential Growth Curve • population increase
under idealized conditions. The rate of reproduction is
at its maximum, called the intrinsic rate of increase.
Cannot be sustained for long in any population
• The J-shaped curve of exponential growth is a
characteristic of some populations that are rebounding.
• A more realistic population model incorporates the
carrying capacity (represented by k) of the
environment.

Population growth models discusses the rate at which
the density of a population increases through time.
At this point let me share with you the
population growth models
Logistic Growth Curve As populations grow, the
resources become limited. When the increase in
animal population is plotted over a long period, the
early increase is rapid, then gradually slows down
as the carrying capacity is reached. The pattern in
which the growth of the population slows down as
it reaches k is called logistic growth curve.

1. Density-dependent–mortality factor whose influence varies with the
density of the population; may reduce population densities and stabilize
them at equilibrium levels. Examples: parasitism, predation, competition.
More individuals of the population are killed when densities are high and
less when densities are low. Predators kill relatively few of prey species
that is rare; they kill relatively more of the common species.
Populations are not only affected by the availability of
resources but also the presence of natural enemies/predators,
parasites and competition with other species. These mortality
factors can be classified into:
Moving on, MORTALITY
FACTORS

2. Density-independent – Mortality factor whose influence is
not affected by changes in the population size or density.
Moving on, MORTALITY
FACTORS
Populations are not only affected by the availability of
resources but also the presence of natural enemies/predators,
parasites and competition with other species. These mortality
factors can be classified into:

1. Name and differentiate the 3
types of dispersion.
2. Differentiate Population growth
and density
3. Name the 2 factors that affects
mortality
Before we continue, lets do
some understanding Check

A. Semelparity – (“Semel” - Latin “once”): Organisms can
produce all their offspring in one reproductive event.
Common in insects and some invertebrates, salmon,
bamboo grasses and agave plants. They reproduce only
once and die. Agaves live to several years before
reproducing; Some are annual plants that develop from
seed, flower and drop their own seed within a year.
Factors affecting Population Density
1. Number of Reproductive Events: Semelparity vs. Iteroparity

B. Iteroparity – (“itero” L = to repeat); Pattern of repeated
reproduction at intervals; common in most vertebrates and
perennial plants such as trees; number of reproductive events
and number of offspring per event vary among species.
i. Seasonal Iteroparity – Have distinct breeding seasons such
as temperate animals and forest trees.
ii. Continuous Iteroparity – individuals reproduce repeatedly
and at any time of the year; found in tropical species,
parasites and many mammals.
1. Number of Reproductive Events: Semelparity vs. Iteroparity

Number of Offspring per Reproductive Event Organisms that live in stable
environments tend to make few, "expensive" offspring. Organisms that live in
unstable environments tend to make many, "cheap" offspring.
(1) r – strategists These animals live in unstable environments and the
ability to reproduce rapidly (exponentially) is important. Such organisms
have high fecundity, give relatively little parental care in any one offspring,
and are vulnerable to predation and the “dictates” of their environment.
The “strategic intent” is to flood the habitat with progeny so that, regardless
of predation or mortality, at least some of the progeny will survive to
reproduce. Organisms that are r-selected have short life spans, are generally
small, quick to mature and waste a lot of energy.

Number of Offspring per Reproductive Event Organisms that live in stable
environments tend to make few, "expensive" offspring. Organisms that live in
unstable environments tend to make many, "cheap" offspring.
(2) k – strategists They are larger in size and have longer life expectancies.
They are stronger or are better protected and generally are more energy
efficient. They produce, during their life spans, fewer progeny, but place a
greater investment in each. The resulting offspring have higher chances of
survival. Their reproductive strategy is to grow slowly, live close to the
carrying capacity of their habitat and produce a few progeny each with a
high probability of survival.

(A) Density-Dependent Regulation Population growth
rates are regulated by the density of a population. Most
density-dependent factors are biological (biotic) in
nature and includes predation, inter- and intra- specific
competition, accumulation of waste, and diseases such
as those caused by parasites. Usually, the denser a
population is, the greater its mortality.
POPULATIONS are regulated by

Density-Dependent Regulation
(A) Competition for Resources Increasing population
density intensifies competition for nutrients and other
resources, reducing reproductive rates.

(B) Predation can be an important cause of
density- dependent mortality if a predator
captures more food as the population density of
the prey increases. As a prey population builds
up, predators may also feed preferentially on
that species. Predator-prey relationship of some
animals like the snowshoe hare and the lynx
demonstrate a cyclic pattern.

(C) Territoriality can limit population density
when space becomes the resource for which
individuals compete. Cheetahs (Acinonyx jubatus)
use a chemical marker in urine to warn other
cheetahs of their territorial boundaries. The
presence of surplus, or nonbreeding, individuals is
a good indication that territoriality is restricting
population growth.

(D) Disease If the transmission rate of a disease
increases as a population becomes more
crowded, then the disease’s impact is density
dependent. In humans, the respiratory diseases
influenza (flu) and tuberculosis are spread
through the air when an infected person sneezes
or coughs. Both diseases strike a greater
percentage of people in densely populated cities
than in rural areas.

(B) Density-Independent Regulation Factors that are
typically physical or chemical (abiotic) in nature that
influence the mortality of a population regardless of its
density. They include weather, natural disasters (storms,
forest fires, flooding, pollution and others). Example, a
bird may be killed during an oil spill regardless of how
many birds were present in that area. Its chances of
survival are the same whether the population density is
high or low.

• http://www.life.illinois.edu/bio100/lectures/s10lects
/04s10-population.html
• https://study.com/academy/lesson/factors-that-
affect-animal-population-size.html
• https://www.youtube.com/watch?v=cZbvJD8TK3A
If you still want to have further
learnings and readings, just click on
the links below…

1. Which of the following is described as typically
physical or chemical (abiotic) in nature that influence
the mortality of a population regardless of its density
a. Density-Independent Regulation
b. Population density
c. Population growth
d. Carrying Capacity
At this point, after all that has been
shared lets us now check your
understanding

2. One of the factors whose influence is not affected by
changes in the population size or density.
a. Density-Independent Regulation
b. Density-Independent Mortality
c. Population Density
d. Carrying Capacity
understanding

3. Which of the following is known as the pattern of
spacing among individuals of the population
a. R strategies
b. Density-Independent Mortality
d. Dispersal
understanding

4. What condition is described as the optimal maximum
density of a population that can be supported by a
defined space.
a. R strategies
b. Carrying Capacity
d. Dispersal
understanding

5. When all conditions favorable to the population
occurs for an extended period of time, this will result to
what?
a. Population Expolsion
b. Carrying Capacity
d. Population Growth
understanding

Hope you were able to answer all
the questions correctly…
Again I'm Captain Planet, I hope you
have enjoyed our journey for
today…
See you all again for our next
adventure… CIAO

Population growth

Recommended

Recommended

More Related Content

What's hot

What's hot (19)

Similar to Population growth

Similar to Population growth (20)

Recently uploaded

Recently uploaded (20)

Population growth