Bài giảng sinh vật học quần thể Population

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

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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

Chapter 3 Populations

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 Đả o (Paramesotriton deloustali )

POPULATION CONCEPS

Polymorphic species:

 Wide distribution area,

 Unhomogeneous environmental living condition

 All populations adapt to each local living condition

 Set up new ecological and physiological characteristics

 May have different genetics, originate new species

Shellfish: Cepaea nemoralis

Individual size is small Many in number of individuals and low biomass

Individual size is big Few number of individuals

and high biomass

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

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

population will be perished

Maximum number of individuals

 Is affected by environmental factors

 The maximum number (K) is equal to environmental capacity

ROLE OF POPULATION SIZE

EQUATION OF POPULATION SIZE

Nt +1 = Nt + B – D + I – E

Number of birth and immigration Births nhập cư

Population size

chết Number of death and emigration

POPULATION DENSITY

0 50 100 150 200 250 300 350 400

Ấu trùng trọng lượng 25mg

Cá con trọng lượng 2g

Cá 1 tuổi trọng lượng 20g

Cá 2 tuổi trọng lượng 280g

Số lượng Khối lượng

Density of Cyprinus carpio

(fish) per 1m3 of water

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

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

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 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

M ối và

t ập 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” and the trend of increasing and decreasing the individual’s number within a population

(Theo Begon và Mortimer, 1988)

TERRITORIALITY

The regulation mechanism of using habitat and living resources

xây t ổ

AGE STRUCTURE

Physiological

age

The number or proportion of individuals

in different age classes

Ecological

age

Populations can be divided into three ecologically

important age classes or stage:

Prereproductive Reproductive Postreproductive

AGE STRUCTURE

AGE PYRAMIDS

(chấm: sau ss; trắng: đang ss; gạch: trước ss)

Degraded population Young population (developing) Stable population

Cross section of tree trunk showing annual growth rings By measuring the width

of each ring, a pattern of radial growth through time can be established

AGE CHARACTERISTICS OF THE POPULATION

 The more complex of age structure – the higher survival and stability

SEX RATIOS INPOPULATIONS

 The proportion of males to females

REPRODUCTIVE STRUCTURE

 The proportion of males to females in the

periods of: prereproductive, reproductive and postreproductive

 Environmental factors

 Reproductive style

1

One to one struggle – Intraspecific competition

2

Parasite – host interaction

3

Prey – peradator interaction

NEGATIVE INTERACTIONS

ONE TO ONE STRUGGLE – INTRASPECIFIC COMPETITION

PARASITE – HOST INTERACTION

PREY – PERADATOR INTERACTION

 Eating each other species, occurs in very special conditions

Assemblage

or herd instinct

Social behavior POSITIVE INTERACTIONS

Assemblage

or herd instinct

Common in nature, supports each others

They can recognize each others by

pheromone or colours

Long –term cooperation by

the herd instinct

Temporary cooperation

Social behavior

http://images.google.com.vn/images?gbv=2&hl=vi&q=ong

bees

http://images.google.com.vn/images?gbv=2&hl=vi&q=ki%E1%BA%BFn ants

http://images.google.com.vn/images?gbv=2&hl=vi&q=m%E1%BB%91i

termites