Unit 6Unit 6Populations Populations DynamicsDynamics

Define these 26 terms:

• CommensalisCommensalismm

• HabitatHabitat• HerbivoryHerbivory• MutualismMutualism• NicheNiche• ParasitismParasitism• PredatorPredator• PreyPrey• Resource Resource

PartitioningPartitioning• SymbiosisSymbiosis

• Age structureAge structure• Population Population

densitydensity• Population Population

distributiondistribution• Population Population

sizesize• Sex ratioSex ratio• Carrying Carrying

capacitycapacity• EmigrationEmigration• ImmigrationImmigration• MigrationMigration

• Age Age structure structure diagramdiagram

• PopulationPopulation• Biotic Biotic

potentialpotential• Density Density

dependent dependent factorfactor

• Survivorship Survivorship curvecurve

• Invasive Invasive speciesspecies

• SuccessionSuccession

Population DynamicsSpecies

InteractionsUnit 6AChp. 5.2

REVIEWEcosystems:

Everything is ConnectedWhat is an ecosystem?An ecosystem includes all the different organisms living in a certain area, along with their physical environment

Two parts of an ecosystem:Biotic Factors:The living parts of an ecosystem which interact with each other and the nonliving parts

Abiotic Factors:The nonliving parts of the ecosystem

Hierarchy•Biosphere•Ecosystem•Community•Population•Species•Organism

Niche v.s. Habitat………•Niche: •all of the organism’s relationships with its environment (both living and nonliving), a way of life

•Examples: what it eats, what its parasites are, rotting when it dies, when & how it reproduces, biorhythms, …

•Habitat:•The actual place an organism lives

•Examples: rain forest, freshwater pond, coral reef,…

Tolerance & Tolerance & CompetitionCompetition

•Tolerance – ability to survive and reproduce under changing environmental conditions–Specialists – very restricted tolerance ranges

•Competition – when multiple organisms seek the same limited resources

Competitive Competitive ExclusionExclusion

•When a competitor species is very effective and excludes another species from the resource use entirely.–Example: the invasive species zebra mussels outcompeted 20 native mussels in Lake St. Clair by 1997.

Resource Resource PartitioningPartitioning

•When competing species partition or divide the resource they use in common by specializing in different ways

•Ex. – birds specialize by particular types of insects & parts of the tree ; can lead to evolution - Galapagos Is.

SYMBIOSISSYMBIOSIS

A long-term and physically close

relationship between two organisms from different species in which at least one organism benefits.

Ways species interact with each other:

•Predation•Competition•Parasitism•Mutualism•Commensalism

Predation1.Predation – one organism

kills and eats another organism

2.Prey – the organism that is eaten

3.Predator – the organism that does the eating

4.Example: lynx and hare

Competition:

A relationship between species in which they attempt to use the same limited resource

Can be direct or indirect

Parasitism1.Parasite – organisms that live

in or on another organism and feed on it without immediately killing it

2.Host – the organism the parasite takes its nourishment from

3.Parasitism – the relationship between parasite & its host

Mutualism•A cooperative

partnership between two species

•Both benefit•Examples?•Barn cat and farmer•Sea Anemone and

Anemonefish

Commensalism

•A relationship in which one species benefits and the other is neither harmed nor helped

•Example?•Bromeliad and tree•Shark and ramoras

Herbivory• The interaction when an animal

feeds on a plant• Most common type: insects• In most cases, herbivory does

not kill a plant directly but it may affect its growth and reproduction

• Plant defenses: toxic chemicals, thorns, spines, irritating hairs, hormones that stimulate growth

Unit 6A (5.2) ReviewUnit 6A (5.2) Review• Explain how competition can affect

an organism’s niche.• How are predation, parasitism, &

herbivory similar? Different?• Human digestive tract is filled with

bacteria that get nutrients by helping digest food. Is this symbiotic? Mutualism or commensalism? Explain.

• Section 5.2 review packet

Population DynamicsPopulation DynamicsUnit 6BUnit 6B

Describing Describing PopulationsPopulations

Chp. 4.2Chp. 4.2

Population Population SizeSize

• The # of individual organisms present in a given population at a given time

• May increase, decrease, undergo cyclical change or remain the same over time (healthy pop.)

• If a population declines rapidly, it can mean extinction is coming (ex. Passenger pigeon)

Determining Population Determining Population SizeSize

• In almost all cases, population size is estimated using sampling techniques.–Ecologists count the # in a smaller sample area, then estimate the # in the larger overall area

–Sometimes it is easier to find signs of organisms instead of the organisms themselves

Population Population DensityDensity

• # of individuals within a population per unit area

• Higher population densities make it easier to find mates or group together, however crowding leads to parasites and competition

Population Distribution• Describes how organisms are

arranged within an area• Random distribution – individuals

arranged in no particular pattern• Uniform distribution – organisms

are spread evenly in an area• Clumped distribution – individuals

arrange themselves based on availability of resources

Age Structure & Sex Age Structure & Sex RatiosRatios

• # of organisms of each age within a population

• Age structure diagrams – tools scientists use to show the age structure of populations

• Sex ratio – proportion of males to females

4.2 Review• How is a population’s size related to

its well-being?• Which population of flamingos is

more dense: 15 flamingos in a 5-square-meter area, or 40 flamingos in a 10-square-meter area?

• Describe the 3 patterns of population distribution. Which of these is the most common distribution in nature?

• 4.2 review packet

Population DynamicsPopulation DynamicsUnit 6CUnit 6C

Population GrowthPopulation GrowthChp. 4.3Chp. 4.3

Factors that determine Population

Growth• Births, deaths, immigration, emigration

• Natality – rate of birth• Mortality – rate of death• Survivorship curve –

shows how likelihood of death varies with age, Types I, II, & III

•Type I – individuals are most likely to die when they are old

•Type II – mortality remains constant throughout an individual’s lifetime

•Type III – mortality is highest for young members of the population

Migration• Seasonal movement into or

out of an area• Immigration – arrival of

individuals from outside a given area

• Emigration – departure of individuals from a given area

• Births & immigrations add individuals to a population; deaths & emigrations subtract

Calculating Population Calculating Population GrowthGrowthindividuals added – individuals subtracted

•Tells us net change in population size•Ex. – annual birthrate = 18/1000, annual death rate = 10/1000, annual immigration rate = 5/1000, annual emigration rate = 7/1000. Calculate annual growth rate•(18 + 5) – (10 + 7) = 6 •Usually expressed as a percent•(6/1000) x 100% = 0.006 x 100% = 0.6%

How Populations How Populations GrowGrow

• Exponential Growth – when a population increases by a fixed % each year, J curve

• Logistic Growth – describes how a population’s exponential growth is slowed and finally stopped by limiting factors which determine its ultimate carrying capacity

• In nature, usually populations fluctuate or rise & crash

Limiting FactorsLimiting Factors• Density-dependent factors –

high population density increase competition for resources; ex. – predation, disease, food & water

• Density-independent factors – limiting factors whose influence is not affected by pop. density; ex. – floods, fires, landslides, climate change

Biotic PotentialBiotic Potential•The maximum ability of an

organism to produce offspring in ideal conditions

• Influenced by gestation time (embryo to birth) and generation time (birth to sexual maturity), as well as # of offspring born at a time

4.3 Review• A population has a birthrate of 10/1000, a

death rate of 9/1000, an immigration rate of 3/1000, and an emigration rate of 7/1000. What is its growth rate? Is the population getting larger or smaller?

• What is the difference between exponential growth & logistic growth? Which is more common over long terms in nature?

• In your own words, define limiting factor and biotic potential.

• 4.3 review packet

Population DynamicsPopulation DynamicsUnit 6DUnit 6D

Community StabilityCommunity StabilityChp. 5.4Chp. 5.4

Ecological Ecological SuccessionSuccession

• Somewhat predictable series of changes over time experienced by a community

• Primary succession – when a disturbance is so severe, no vegetation or soil life remains

• Secondary succession – begins when a disturbance dramatically alters an existing community but does not destroy all living things

• Pioneer species – colonize newly exposed land first in primary succession; ex. – lichen take firm hold on rock, capture moisture, release acids, soil begins to form

• Climax community – a stable community that “completes” the succession process; ex. – beech-maple forests, old growth forests

Invasive Invasive SpeciesSpecies• Non-native organisms that

spread widely in a community because they lack limiting factors

• Not all exotic species become invasive as some stay small & localized

• Not all invasive species are bad, ex. – European honeybee

• Bad ex’s – zebra mussels, cane toad, kudzu vine

5.4 Review5.4 Review• Explain how disturbances can throw a

community out of a balanced state and into a period of adjustment.

• List examples of primary & secondary succession and describe the stages; identify the factors that determine the type of succession that will occur.

• Identify a pioneer species & list several examples in different ecosystems.

• Describe the how, when, where of climax communities.

• List examples of invasive species in Florida.