Grade 10 - Population Ecology

sir awan

Ecology - Study of interactions among organisms and their environment

Conservation biology, environmentalism:preservation of natural world

• Biosphere

• Bioma

• Ecosystemas

• Community

• Population

• Individu

• Organ system

• Organ

• Tissue

• Cell

• Molecular

ECOSYSTEM LEVELEucalyptus forest

COMMUNITY LEVELAll organisms ineucalyptus forest

POPULATION LEVELGroup of flying foxes

ORGANISM LEVELFlying fox

ORGAN SYSTEM LEVELNervous system

ORGAN LEVELBrain

Brain Spinal cord

Nerve

TISSUE LEVELNervous

tissue

CELLULAR LEVELNerve cell

MOLECULAR LEVELMolecule of DNA

Population: All the individuals of a species that live together in an area

Demography: The statistical study of populations, allows predictions to be made about how a population will change

Three Key Features of Populations Size Density Dispersion

Three Key Features of Populations

Size: number of individuals in an area

Three Key Features of Populations

Growth Rate: Birth Rate (natality) - Death Rate

(mortality) How many individuals are born vs. how

many die Birth rate (b) − death rate (d) = rate of

natural increase (r)

Density: measurement of population per unit area or unit volume

Pop. Density = # of individuals ÷ unit of space

Three Key Features of Populations

Immigration: movement of individuals into a population

Emigration: movement of individuals out of a population

Density-dependent factors: Biotic factors in the environment that have an increasing effect as population size increases (disease, competition, parasites)

Density-independent factors: Abiotic factors in the environment that affect populations regardless of their density (temperature, weather)

Immigration

Emigration

Natality MortalityPopulation+

+

-

-

Factors That Affect Future Population Growth

Population Dispersion

Dispersion: describes the spacing of organisms relative to each other– Clumped - often correlates with resources

– Uniform: interactions among individuals

– Random: no pattern

Three Key Features of Populations

Population density = number of individuals in a given area or volume

Count all the individuals in a population

Estimate by sampling Mark-Recapture Method

Idealized models describe two kinds of population growth:

1. Exponential Growth has no upper limit and populations grow very quickly

2. Logistic Growth has a limit and growth approches this limit in a sigmoidal fashion

Logistic growth is more realistic in real life, but exponential growth is a better model for bacterial cultures, etc. that have unlimited resources and space

Carrying Capacity (k): The maximum population size that

can be supported by the available resources

There can only be as many organisms as the environmental resources can support

• A J-shaped growth curve, described by the equation G = rN, is typical of exponential growth

– G = the population growth rate

– r = the intrinsic rate of increase, or growth rate in an ideal environment (births-deaths)

– N = the population size

Figure 35.3A

– K = carrying capacity

– The term (K - N)/K accounts for the leveling off of the curve

During the initial stage, during the lag phase, the rate of plant growth is slow. Rate of growth then increases rapidly during the exponential phase. After some time the growth rate slowly decreases due to limitation of nutrients. This phase constitutes the stationary phase.

Declining birth rate or increasing death rate are caused by several factors including: Limited food supply The buildup of toxic wastes Increased disease Predation

About every 10 years, both hare and lynx populations have a rapid increase (a "boom") followed by a sharp decline (a "bust")

r Selection (many offspring)

Short life span Small body size Reproduce quickly Have many young Little parental care Ex: cockroaches,

weeds, bacteria

• K Selection (few offspring)

Long life span Large body size Reproduce slowly Have few young Provides parental

care Ex: humans,

elephants

Distribution of males and females in each age group of a population

Used to predict future population growth

J curve growth Why doesn’t environmental resistance take

effect? Altering their environment Technological advances

The cultural revolution The agricultural revolution The industrial-medical revolution

Doubled three times in the last three centuries

About 6,1 billion and may reach 9.3 billion by the year 2050

Improved health and technology have lowered death rates

What next?