EcologyEcologyPart 2Part 2

Honors Biology

Population DynamicsPopulation Dynamics

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

Demography: statistical study of populations, make predictions about how a population will change

Population DynamicsPopulation Dynamics

Three Key Features of Populations

•Size

•Density

•Dispersion

• (clumped, even/uniform, random)

Population DynamicsPopulation Dynamics

#1: Size

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).

Three Key Features of Populations

PRE-REPRODUCTIVE

REPRODUCTIVE

POST-REPRODUCTIVE

Population of a Stable Country  

US Baby BoomUS Baby Boom

19701970 19851985

Time unit Births DeathsNatural

increase

Year 130,013,274 56,130,242

73,883,032

Month 10,834,440 4,677,520 6,156,919

Day 356,201 153,781

202,419

Hour 14,842 6,408 8,434

Minute 247

107 141

Second 4.1

1.8 2.3

Three Key Features of PopulationsThree Key Features of Populations

#2: Density:

Number of individuals ÷ Unit of space

ex: 50 mice/square mile

1. 1. Immigration-Immigration- movement of movement of individuals into a populationindividuals into a population

2. 2. Emigration-Emigration- movement of movement of individuals out of a populationindividuals out of a population

4 Factors that affect density4 Factors that affect density

4 Factors that affect density4 Factors that affect density

3. 3. Density-dependent factors-Density-dependent factors- Biotic Biotic factors in the environment that have an factors in the environment that have an increasing effect as population size increasing effect as population size increasesincreases

   Ex.Ex. diseasedisease

competitioncompetition

parasitesparasites

4. 4. Density-independent factors-Density-independent factors- Abiotic factors in the environment that Abiotic factors in the environment that affect populations regardless of their affect populations regardless of their densitydensity

   Ex.Ex. temperature temperature

stormsstorms

habitat destructionhabitat destruction

droughtdrought

4 Factors that affect density4 Factors that affect density

Immigration

Emigration

Natality MortalityPopulation+

+

-

-

Factors That Affect Future Population Growth

Three Key Features of PopulationsThree Key Features of Populations

#3: Dispersion: describes organisms’ spacing

• even or uniform

• clumped

• random

clumped

even (uniform)

random

Population Dispersion

Other factors that affect population growthOther factors that affect population growth

Limiting factor-Limiting factor- any biotic or any biotic or abiotic factor that restricts the abiotic factor that restricts the existence of organisms in a existence of organisms in a specific environment.specific environment. EX.-EX.- Amount of waterAmount of water

Amount of foodAmount of foodTemperatureTemperature

Carrying Capacity- the maximum population size that can be supported by the available resources

Other factors that affect population growthOther factors that affect population growth

Carrying CapacityCarrying Capacity

Carrying Capacity (k)

Nu

m

b

e

r

Time

J-shaped curve (exponential growth)

S-shaped curve (logistic growth)

2 Life History Patterns2 Life History Patterns

1. R Strategists1. R Strategists short life span short life span small body sizesmall body size reproduce quickly reproduce quickly have many young have many young little parental care little parental care Ex: cockroaches, Ex: cockroaches,

weeds, bacteria weeds, bacteria

2 Life History Patterns2 Life History Patterns

2. K Strategists long life span large body size reproduce slowly have few young provides parental

care Ex: humans,

elephants

Squid vs. Sperm WhaleSquid vs. Sperm Whale Lives 1 yearLives 1 year Lays up to 9,000 eggsLays up to 9,000 eggs Length 20 cmLength 20 cm Embryos develop ~ 1 monthEmbryos develop ~ 1 month No care for offspringNo care for offspring Safety in numbers (mating Safety in numbers (mating

and eggs)and eggs) Dramatic population Dramatic population

fluctuations between years.fluctuations between years. Can quickly repopulate new/ Can quickly repopulate new/

unstable environmentsunstable environments

Lives 70 yearsLives 70 years Length 18 meters Length 18 meters

(male)(male) Gestation – 15 monthsGestation – 15 months Calf nurses ~ 2 yearsCalf nurses ~ 2 years Female calves every 4 Female calves every 4

years (max)years (max) Invest energy into Invest energy into

individual offspring.individual offspring. Best in stable/ Best in stable/

established established environmentsenvironments

Human Population GrowthHuman Population Growth

Human Population GrowthHuman Population Growth

World BiomesWorld Biomes

Succession in Succession in EcosystemsEcosystems

SuccessionSuccession--

a series of changes in a community a series of changes in a community in which new populations of in which new populations of organisms gradually replace organisms gradually replace existing ones existing ones

Primary successionPrimary succession--

colonization of new sites by colonization of new sites by communities of organisms communities of organisms – takes – takes place on bare rockplace on bare rock

Primary successionPrimary succession--

New bare rock comes from 2 New bare rock comes from 2 sources:sources: 1. volcanic lava flow cools and 1. volcanic lava flow cools and

forms rockforms rock

Primary successionPrimary succession--

New bare rock comes from 2 New bare rock comes from 2 sources:sources: 2. Glaciers retreat and expose 2. Glaciers retreat and expose

rockrock

Pioneer organisms-Pioneer organisms-

the first organisms to colonize a the first organisms to colonize a newnew site site Ex: lichens are the first to colonize Ex: lichens are the first to colonize

lava rocks lava rocks

Primary SuccessionPrimary Succession--

Rock

Climax community-Climax community-

a stable, mature community that a stable, mature community that undergoes little or no successionundergoes little or no succession

Climax community-Climax community-

Ex: In most of Virginia, the climax Ex: In most of Virginia, the climax community would be acommunity would be a deciduous deciduous oak–hickory forest oak–hickory forest

                                                                                                                                

Primary succession-

Secondary succession-Secondary succession-

sequence of community changes sequence of community changes that takes place when a that takes place when a community is disrupted by natural community is disrupted by natural disaster or human actions disaster or human actions – takes – takes place on existing soilplace on existing soil

Secondary succession-Secondary succession-

Ex: Ex: A fire levels A fire levels

portions of a portions of a forestforest

Secondary succession-Secondary succession-

Ex: Ex: A farmer A farmer

plows his plows his fieldfield

Secondary succession-

Secondary succession-

Pond SuccessionPond Succession

A newly formed pond near the beach has sandy borders bare of vegetation

After two years such a pond is ringed by low vegetation including cottonwood saplings.

A 50-yr old pond is bordered by mature cottonwood trees. Such much sediment is produced by organisms growing in the pond that only a small area of water, choked with weeds, remains.

After 150-250 years the area has become a meadow.

Pond SuccessionPond Succession

Write the letters of the ponds in order from the youngest, to the oldest

Pond SuccessionPond Succession