Ppt from population ..class 12 biology

2. TOPIC – POPULATION
CONTENT -
MIGRATE
SUSPEND
ADAPTATION
POPULATION
 ATTRIBUTES
 METHODS TO CALCULATE POPULATIOM DENSITY
POPULATION GROWTH
GROWTH MODELS
 EXPONENTIAL
 LOGISTIC

3. MIGRATE
The organism can move away
temporarily from the stressful
habitat to a more hospitable area
and return when stressful period
is over.
Eg.-Every winter the famous
keolado National Park
(bharatpur) in Rajasthan host
thousands of migratory birds
(Siberian crane)coming from
Siberia and other extremely cold
northern region.

4. SUSPEND
In bacteria, fungi, and lower plants, various kinds of thick-walled
spores are formed which help them to survive in unfavorable
conditions - these germinate on the availability of a suitable
environment. The higher plants, seeds, and some other vegetative
reproductive structures helps to overcome this period .They do as
such by lessening their metabolic action and going into a state of
‘dormancy’.
The natural instance of bears hibernating during winter is an example
of an escape in time. Some of the snails and fish go into aestivation
to avoid the summer-related problems (heat and desiccation).Under
unfavorable conditions, many zooplankton species in lakes and
ponds are known to enter the diapause phase, a stage of suspended
development.

5. ADAPTAION
Adaptation is any attribute of organism that enables them to survive
and reproduce in its habitat. Many adaptations are genetically fixed.
KANGAROO RAT
Found in north American desert is capable of meeting all its
water requirement through its internal fat oxidation, it also has a
unique ability to concentrate its urine so that minimum water is
used for excreting waste material.
DESERT PLANTS
Have thick cuticle on their leaf surface ,and sunken stomata to
minimize water loss through transpiration. Some plants like
Opuntia have no leaves they are reduced to spines and the
photosynthesis function is taken by stem(phylluclade).

6. .
ALLENS RULE
Mammals from colder climates generally have short limbs
and ears to minimize heat loss. Aquatic mammals like seal
have a thick layer of fat (blubber)below their skin that acts
as insulator and reduce loss of body heat.
ALTITUDE SICKNESS
It is an illness due to low atmospheric pressure at high
altitudes places(>3500m Rohtang pass near Manali and
Leh). It is characterized by nausea , fatigue and heart
palpitation. The body does not get enough oxygen.
DESERT LIZARD
They bask in the sun and absorb heat when their body
temperature drops below the comfort. Some species are
capable of burrowing into the soil to hide and escape from
the above-ground heat.

7. POPULATION
 A population is defined as a group of
individuals of the same species living and
interbreeding within a given area. A
group of individual resulting from even
asexual reproduction is also generally a
population for ecological studies.
 A population has certain attributes
whereas, an individual organism does not.
An individual have birth and death while
a population has birthrates and death
rates. In a population these rates refers to
per capita births and deaths.

8. POPULATION ATTRIBUTES
BIRTH RATES
DEATH RATES
POPULATION
DENSITY
SEX RATIO
AGE PYRAMID
POPULATION
AGE

9. BIRTH RATE
The birth rate in a
period is the total
number of live births
per 1,000 population
divided by the length
of the period in year.
Natality in population
ecology is the
scientific term
for birth rate.
DEATH RATE
Death rate is a
measure of the death
in a particular
population, scaled to
the size of that
population, per unit
of time. Mortality rate
is typically expressed
in units of deaths per
1,000 individuals per
year.
POPULATION
DENSITY
Population density
is the concentration
of individuals within
a species in a specific
geographic locale. It
is also known as
population size
denoted by :N.

10. POPULATION
AGE
Population ageing
is an increasing
median age in a
population because
of declining fertility
rates and rising life
expectancy. The aged
population is
currently at its
highest level in
human history.
SEX RATIO
Sex ratio is defined as
the number of
females per 1000
males in the
population. This
information is an
important social
indicator to measure
the extent of equality
between males and
females in a society at
a given time
AGE PYRIMID
Also known as an
"age-gender-
pyramid". It is a
graphical illustration
that shows the
distribution of varied
age groups in a
population that
forms the figure or
shape of a pyramid
when the population
is growing.

11. METHODS TO CALCULATE POPULATION DENSITY
BIOMASS OR PERCENTAGE
COVER
Area covered by a species is
considered. Eg. In an area carrot
grass 200 plants and only 1 banyan
tree. Then N of banyan<N of
parthenium.
TOTAL NUMBER
Number of individual of a species is
counted. Eg. < 10 crane in
bharatpur wetlands in any year,
millions of chlamydomonas in a
pond.
RELATIVE DENSITY
For some ecological
investigations there is no need
of absolute population densities
relative density serve the
purpose equally well. Eg.
Bacteria culture in labs.
INDIRECT COUNT
We are mostly obliged to estimate
population sizes indirectly, without
actual calculating them or seeing
them. Eg. Tiger census in national
parks is often based on pug marks.

12. INDIAN STATISTICS REGARDING POPULATION
The current population of India is 1,400,309,632 as of Saturday, January
1, 2022.
India 2020 population is estimated at 1,380,004,385 people at mid year
according to UN data.
India population is equivalent to 17.7% of the total world population.
India ranks number 2 in population.
The population density in India is 464 per Km2 (1,202 people per m2).
35.0 % of the population is urban (483,098,640 people in 2020)
The median age in India is 28.4 years.
Males are conventionally shown on the left and females on the right side.

13. POPULATION GROWTH
The size of population of any species in not a static parameter. It
keeps on changing with time, depending on various factors including
food availability, predation pressure and adverse weather.
The population of a given area during a given period, fluctuates, due
to change in four basic process. That are as follows:
1. Natality
2. Immigration
3. Mortality
4. Emigration
Contributes to increase in population.
Contributes to decrease in population

14. :if the N is the population density at time t, then its density at time
t1 is:
Nt+1=Nt+[(B+I)−(D+E)]
NATALITY
It refers to the
number of births
during a given
period of time.
IMMIGRATION
The no. of
individual that
have come into a
habitat from
elsewhere.
↑se MORTALITY
It refers to the no.
of deaths during a
given period in a
population.
EMIGRATION
The no. of
individuals who
left the habitat
and gone out.
↓se

15. GROWTH MODEL
A population growth model tries to predict the population of an
organism that reproduces according to fixed rules. Depending on how
many times an organism reproduces, how many new organisms it
produces each time.
FEATURES EXPONENTIAL LOGISTIC
Resources Unlimited Limited
Environmental
resistance
Does not effect exponential
growth
Effects logistic growth
Growth curve ‘J’-shaped ‘S’-shaped (sigmoid)
Real occurence Less common More common
Example Algal bloom, insects Birds, human
Equation dN/dt rN or Nt No e^rt dN/dtrN[(K-N)/K]
N-population density at time t; Nt- population density after time t; No-population
density at time zero
r-intrinsic rate of natural increase; e-the base of natural logarithm(2.71828)

17. mcqs
 When births are equal to deaths, it is:
(a) Plateau stage
(b) Exponential stage
(c) Early growth stage
(d) Acceleration stage
Answer: (a) Plateau stage
 Animals undergo inactive stage during
winters. It is called :
(a) Acclimatization
(b) Hibernation
(c) Aestivation
(d) Adaptation
Answer: (b) Hibernation
 The maximum growth rate occurs in :
(a) Lag phase
(b) Exponential phase
(c) Stationary phase
(d) Senescent phase
Answer: (b) Exponential phase
 The plants of this group are adapted to
live partly in water and partly above
substratum and free from water
(a) Xerophytes
(b) Thallophytes
(c) Hydrophytes
(d) Helophytes
Answer: (d) Helophytes

18.  Which of the following would necessarily
decrease the density of a population in a
given habitat?
(a) Immigration > emigration
(b) Natality and immigration
(c) Natality > mortality
(d) Mortality and emigration
Answer (d) Mortality and emigration
 When the number of immigration and
births is more than emigration and deaths,
the growth curve of the population will
show
(a) Declining phase
(b) Steady phase
(c) Exponential phase
(d) Lag phase
Answer (c) Exponential phase
 The number of births in polygamous
population is often directly related to :
(a) number of males
(b) number of females
(c) both (a) and (b)
(d) none of these
Answer (b) number of females
 The population growth curve is sigmoid if
the growth pattern is
(a) Geometric
(b) Accelerating
(c) Logistic
(d) Exponential
Answer (c) Logistic

19.  In a population, unrestricted reproductive
capacity is called
(a) Biotic potential
(b) Birth rate
(c) Fertility
(d) Carrying capacity
Answer (a) Biotic potential
 Two opposite forces operate in the growth
and development of every population. One
of them relates to the ability to reproduce
at a given rate. The force opposing to it is
called
(a) mortality
(b) fecundity
(c) biotic control
(d) environmental resistance
Answer (d) environmental resistance
 For human population, the age pyramids
generally show age distribution of
(a) Only males
(b) Only females
(c) Of males and females
(d) None of the above
Answer (c ) of males and females
 The size of the population tells us a lot
about its status in the
(a) Environment
(b) Sex-ratio
(c) Age pyramid
(d) Habitat
Answer (d ) habitat

20.  The semi log of per minute growing
bacteria is plotted against time. What
will be the shape of graph?
(a) Sigmoid
(b) Hyperbolic
(c) Ascending straight line
(d) Descending straight line
Answer (c) Ascending straight line
 The number of deaths in the population
during a given period is referred to
(a) Natality
(b) Mortality
(c) Sex-ratio
(d) None of the above
Answer (b) mortality
 The number of birth during a given
period in the population that are added
to the initial density is referred to
(a) Natality
(b) Mortality
(c) Sex-ratio
(d) None of the above
Answer (a) Natality
 A stage of suspended development in
zooplanktons is called
(a) Diapause
(b) Suspend
(c) Migrate
(d) Aestivation
Answer (a) diapause

21.  Which should be considered more
realistic growth model?
(a) Verhulst-Pearl logistic growth
(b) Geometric growth
(c) Exponential growth
(d) None of the above
Answer (a) Verhulst-Pearl logistic growth
 Human population follows the
(a) J-shaped growth curve
(b) Z-shaped growth curve
(c) S-shaped growth curve
(d) All of the above
Answer (c) S-shaped growth curve
 It Natality is balanced by mortality in a
population at a given time, there will be
a/an
(a) decrease in the population size
(b) increase in the population size
(c) zero population growth
(d) population explosion
Answer(c) zero population growth
 Which of the following would necessarily
decrease the density of a population in a
given habitat?
(a) Immigration > emigration
(b) Natality and immigration
(c) Natality > mortality
(d) Mortality and emigration
Answer(d) Mortality and emigration

22. ASSERTION REASONS
Directions: In the following questions, a statement of assertion is followed by a
statement of reason.
Mark the correct choice as:
(a) If both Assertion and Reason are true and Reason is the correct explanation of
Assertion.
(b) If both Assertion and Reason are true but Reason is not the correct explanation
of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.
(e)If assertion is false reason is true
 Assertion : The rate at which a population can be expected to grow in the future
can be assessed graphically by means of a population pyramid.
Reason : A triangular population pyramid is characteristic of a country whose
population is stable, neither growing nor shrinking.(c)

23.  Assertion : Death is one of the important regulatory process on earth.
Reason : It avoids over-crowding caused by continuous reproduction. (a)
 Assertion : Natality rate increases the population size and population density
both.
Reason : Natality increases the number of individuals in an area by births. (e)
 Assertion: One in every six persons in the world is an Indian.
Reason: In India, there are more females than males.(a)
 Assertion : a population that fits the logistic growth model increases more
rapidly at intermediate size rather than at relatively small and large sizes.
Reason: the population growth rate decreases dramatically as the population
size approaches the carrying capacity. (b)

24. CASE STUDY
 Read the following and answer any four questions from (i) to (v) given below:
Age sex structure of a population can be depicted in the form of a pyramid by plotting
the percentage of population of each sex in each age class. Two age sex pyramids are as
follows.
(i) Which of the following is correct regarding pyramid B?
(a)It represents stable population (b) It represents expanding population.
(c) It represents declining population (d) Both (a) and (b)
(ii) Total number of individuals of a species per unit area per unit time is called
(a) population size (b) population density
(c) demography (d) population dynamics

25. iii) Which of the following is correct regarding age sex pyramid A and B?
(a) A represents the age sex pyramid of developed country.
(b) B represents the age sex pyramid of developing country.
(c) A represents rapidly growing population.
(d) Both (a) and (b)
(iv) A population with a large proportion of older individuals than younger ones will
likely to
(a) grow larger first and then decline (b) continue to grow indefinitely (c) decline
(d) none of these.
(v) Assertion: Bell shaped age pyramid represents a stable population.
Reason : In a stable population, proportion of individuals in reproductive age group
is higher than the individuals in pre-reproductive age group.
(a) Both assertion and reason are true and reason is the correct explanation of
assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of
assertion.
(c) Assertion is true but reason is false.
(d) Both assertion and reason are false.