Bài giảng sinh vật học quần thể Population

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Chapter 3
Populations


Chapter 3. Populations
1. Definition and concepts
2. Properties of populations
•

Population size and density

•

Spatial structure

•

Age structure

•

Sex ratios and reproductive structure

3. Interactions of individuals within a population
•

Negative interactions

•

Positive interactions


DEFINITION
is a group of individuals of the same species that inhabit a given area.


POPULATION CONCEPS
Monomorphic species:
 Narrow distribution area,
 Relatively
homogeneous
environmental living condition
 Only one population
 Usually endemic species, easily
be exterminated
 Be preserved

Cá cóc Tam Đảo
(Paramesotriton deloustali)


POPULATION CONCEPS
Polymorphic species:
 Wide distribution area,
 Unhomogeneous
living condition

environmental

 All populations adapt to each local
living condition.
 Set up new ecological
physiological characteristics.
 May have different
originate new species.

Shellfish: Cepaea nemoralis

and

genetics,


POPULATION SIZE

(usually denoted N)
is the number of

individual organisms
in a population.


REVERSE RELATION
Individual size

Individual size is small

Individual size is big

Number of individuals

Many in number of individuals
and low biomass
Few number of individuals
and high biomass

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Tảo xoắn
Spirulina

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bệnh tả

Chim Se Sẻ Tàu


ROLE OF POPULATION SIZE
 Large size

high ability to maintain the life

 Population size of the same species in temperate zone is
usually bigger than it’s in low latitude region.


ROLE OF POPULATION SIZE
Minimum number of individuals

 Typical characteristic of species
 Maintains population’s functions
 If the number of individuals of

one population is lower than
minimum number

this

Maximum number of individuals

 Is affected by environmental
factors
 The maximum number (K) is
equal to environmental capacity.

population will be perished.

Cá Cháy

Cá Mòi


EQUATION OF POPULATION SIZE

Nt +1 = Nt + B – D + I – E
Number of birth and immigration

Births

nhập cư

Population size

Number of death and emigration
chết


POPULATION DENSITY
The number of individuals per unit area (per square kilometer,
hectare, or square meter) or per unit volume (per liter or m3)
Số lượng

Density of Cyprinus carpio
(fish) per 1m3 of water

Khối lượng

400
350
300
250
200
150
100
50
0
Ấu trùng Cá con trọng Cá 1 tuổi
Cá 2 tuổi

trọng lượng
lượng 2g
trọng lượng trọng lượng
25mg
20g
280g


MEANINGS OF DENSITY
 Showing the balance between reproductive potential and
environmental capacity.
 Affecting the impacts of dependent-density factors
 Being the biological signal

 Exposing the average distance between individuals and
controlling function activities and physiological status of

individuals in population.


DENSITY MEASUREMENTS




microorganisms

Active animals (fish, reptile,
amphibian, bird, mammal)

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Bò sát



Phytoplankton and Zooplankton
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nổi



Phytobenthos and



Movement population (determined
population size)



Hard to see population
(dangerous animals).

zoobenthos

ĐV đáy

Hổ

SPATIAL STRUCTURE OF POPULATION



Patterns of the spatial distribution for individuals

within a population


Assemblage, safety area and Allee effect



Isolation and territoriality


PATTERNS OF THE SPATIAL DISTRIBUTION FOR
INDIVIDUALS WITHIN A POPULATION

Uniform

Random

Clumped


UNIFORM DISTRIBUTION
● Homogeneous environmental conditions

● Strong spatial competition between individuals

● Each individual has high territorial property (territoriality)


RANDOM DISTRIBUTION
● Homogeneous environmental conditions
● Individuals have not high territoriality as well as do not tend to
occur in groups.


CLUMPED DISTRIBUTION
● Unhomogeneous environmental conditions

● Individuals occur in groups for searching food,
withstanding enemy attacks…


ASSEMBLAGE
 Partial deferences of environmetal factors
 Influence of weather factors following the cycle of day-nights and
seasons.
 Reproductive process and behavior of species
 Social assemblage behavior of some species

Mối và
tập tính xã hội

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SAFETY AREA

The special assemblage, each individual group
resides in most favourable centre, spreads out
for food or satisfies other demands, then returns
to centre area.


ALLEE EFFECT
The mechanism of population regulation upon density
Birth rate

Death rate

“Allee effect” and the trend of
increasing and decreasing the
individual’s number within a population

(Theo Begon và Mortimer, 1988)
(a)

0

(b)

U

(c)

K

Population size

ISOLATION

The separation of living space among individuals
• Food competition
• Nest competition

• Breeding competition
•

Food resources competition for newborns


TERRITORIALITY

The regulation mechanism of using habitat and living resources

xây tổ


AGE STRUCTURE

The number or proportion of individuals
in different age classes

Physiological
age

Ecological

age


AGE STRUCTURE
Populations can be divided into three ecologically
important age classes or stage:

Prereproductive

Reproductive

Postreproductive