Question of the dayQuestion of the day

All of the following are examples of abiotic All of the following are examples of abiotic factors exceptfactors except

a.a. temperaturetemperature

b.b. pHpH

c.c. windwind

d.d. salinitysalinity

e.e. vegetationvegetation

NOTESNOTES

Chapter 9-1Chapter 9-1

Population Dynamics Population Dynamics & Carrying Capacity & Carrying Capacity

Core Case Study: Core Case Study: Southern Sea Otters: Are They Back Southern Sea Otters: Are They Back

from the Brink of Extinction?from the Brink of Extinction?

Sea otters are an important Sea otters are an important keystone species for sea keystone species for sea urchins and other kelp-eating urchins and other kelp-eating organisms.organisms.

They were over-hunted to the They were over-hunted to the brink of extinction by the early brink of extinction by the early 1900’s and are now making a 1900’s and are now making a comeback.comeback.

Figure 8-1Figure 8-1

Key Terms & Concepts Key Terms & Concepts (1 of 2)(1 of 2)

PopulationPopulation- the number of individuals of a - the number of individuals of a species that inhabit a particular area.species that inhabit a particular area.

Population structure- Population structure- the density and spacing of the density and spacing of individuals within a landscape.individuals within a landscape.• SpacingSpacing (or dispersion) refers to the dispersion (or dispersion) refers to the dispersion pattern of individuals in a population.pattern of individuals in a population.

Geographic distribution – a species’ range; the range can change with changing population dynamics.

Population dynamics- Population dynamics- population changes over population changes over time.time.

Population Spacing or Dispersal Population Spacing or Dispersal

Spacing is dependent on the availability of resourcesSpacing is dependent on the availability of resources Clumped Spacing Clumped Spacing - individuals are clustered in groups, most - individuals are clustered in groups, most

common. common. Uniform spacing Uniform spacing – regular spacing or dispersal– regular spacing or dispersal Random spacing Random spacing - no spacing pattern is apparent - no spacing pattern is apparent

Key Terms & Concepts Key Terms & Concepts (2 of 2)(2 of 2)

NatalityNatality Number of individuals added through Number of individuals added through

reproductionreproduction Crude Birth Rate - Births per 1000Crude Birth Rate - Births per 1000 Total Fertility Rate – Average number of children Total Fertility Rate – Average number of children

born alive per woman in her lifetimeborn alive per woman in her lifetime

MortalityMortality Number of individuals removed through deathNumber of individuals removed through death Crude Death Rate Deaths per 1000Crude Death Rate Deaths per 1000

Age Structure Age Structure - proportion of individuals in each - proportion of individuals in each age group in populationage group in population

Population GrowthPopulation Growth Population growth depends upon Population growth depends upon

birth rates (+) birth rates (+) death rates (-) death rates (-) immigration rates (+ into area)immigration rates (+ into area) emigration rates (- exit area)emigration rates (- exit area)

Population = PopPopulation = Pop00 + (b + i) - (d + e) + (b + i) - (d + e)

Zero Population Growth (ZPG) Zero Population Growth (ZPG) (b + i) = (d + e)(b + i) = (d + e)

Age Structure: Young Populations Age Structure: Young Populations Can Grow FastCan Grow Fast

How fast a population grows or declines How fast a population grows or declines depends on its age structure.depends on its age structure.

Prereproductive agePrereproductive age: not mature enough to : not mature enough to reproduce.reproduce.

Reproductive ageReproductive age: those capable of reproduction.: those capable of reproduction.

Postreproductive agePostreproductive age: those too old to reproduce.: those too old to reproduce.

Age Structure DiagramsAge Structure DiagramsPositive Growth Zero Growth Negative Growth (ZPG)Pyramid Shape Vertical Edges Inverted Pyramid

Biotic potential Biotic potential is a population’s capacity for is a population’s capacity for growth.growth.

• Biotic potential is limited by environmental factors.Biotic potential is limited by environmental factors.• Thus no population can increase its size indefinitely. Thus no population can increase its size indefinitely.

Environmental resistanceEnvironmental resistance: all the factors that act : all the factors that act to limit the growth of a population. to limit the growth of a population.

• Biotic factorsBiotic factors: reproductive rate, niche, food : reproductive rate, niche, food supply, disease resistance, etc. supply, disease resistance, etc.

• Abiotic factorsAbiotic factors: light, temperature, chemical : light, temperature, chemical environment (i.e. pH)environment (i.e. pH)

Limits on Population Growth

The intrinsic rate of increase (The intrinsic rate of increase (rr) is the rate at which ) is the rate at which a population would grow if it had unlimited a population would grow if it had unlimited resources.resources.

Carrying capacity (Carrying capacity (KK): the maximum population of a ): the maximum population of a given species that a particular habitat can sustain given species that a particular habitat can sustain indefinitely without degrading the habitat.indefinitely without degrading the habitat.

• Determined by the interaction of biotic potential and Determined by the interaction of biotic potential and environmental resistance.environmental resistance.

• Growth rate (r) decreases as its size nears the K. Growth rate (r) decreases as its size nears the K. Why? Why?

Limits on Population Growth

Population GrowthPopulation Growth Populations show two types of Populations show two types of

growthgrowth Exponential Exponential

• J-shaped curveJ-shaped curve• Growth is independent of population Growth is independent of population

densitydensity

Logistic Logistic • S-shaped curveS-shaped curve• Growth is not independent of population Growth is not independent of population

densitydensity

Exponential and Logistic Population Exponential and Logistic Population Growth: J-Curves and S-CurvesGrowth: J-Curves and S-Curves

Populations Populations grow rapidly with grow rapidly with ample ample resources, but resources, but as resources as resources become limited, become limited, its growth rate its growth rate slows and levels slows and levels off.off.

Figure 8-4Figure 8-4

Logistic GrowthLogistic Growth Because of Environmental resistance, population Because of Environmental resistance, population

growth decreases as density reaches carrying growth decreases as density reaches carrying capacitycapacity

Graph of individuals vs. time yields a sigmoid or S-Graph of individuals vs. time yields a sigmoid or S-curved growth curvecurved growth curve

Reproductive time lag causes population overshootReproductive time lag causes population overshoot

Population will not be steady curve due to resources Population will not be steady curve due to resources (prey) and predators(prey) and predators

Population Dynamics and Population Dynamics and Carrying Capacity (K) Carrying Capacity (K)

Over time, populations of species in an ecosystem Over time, populations of species in an ecosystem are usually in a state of equilibrium (balance are usually in a state of equilibrium (balance between births and deaths)between births and deaths)

There is a dynamic balance between biotic potential There is a dynamic balance between biotic potential and environmental resistanceand environmental resistance

Exponential curve is not realistic due to carrying Exponential curve is not realistic due to carrying capacity of areacapacity of area

Exceeding Carrying Capacity: Move, Exceeding Carrying Capacity: Move, Switch Habits, or Decline in SizeSwitch Habits, or Decline in Size

Members of Members of populations which populations which exceed their exceed their resources will die resources will die unless they adapt or unless they adapt or move to an area with move to an area with more resources.more resources.

Figure 8-6Figure 8-6

Exceeding Carrying Capacity: Move, Exceeding Carrying Capacity: Move, Switch Habits, or Decline in SizeSwitch Habits, or Decline in Size

Over time species may increase their Over time species may increase their carrying capacity by developing adaptations.carrying capacity by developing adaptations.

Some species maintain their carrying Some species maintain their carrying capacity by migrating to other areas.capacity by migrating to other areas.

So far, technological, social, and other So far, technological, social, and other cultural changes have extended the earth’s cultural changes have extended the earth’s carrying capacity for humans.carrying capacity for humans.

Population Density and Population Population Density and Population Change: Effects of CrowdingChange: Effects of Crowding

Population density: the number of individuals in a Population density: the number of individuals in a population found in a particular area or volume.population found in a particular area or volume.

Density depends upon social/population structure, Density depends upon social/population structure, mating relationships, time of yearmating relationships, time of year

A population’s density can affect how rapidly it can A population’s density can affect how rapidly it can grow or decline. e.g. biotic factors like diseasegrow or decline. e.g. biotic factors like disease

Some population control factors are not affected by Some population control factors are not affected by population density.population density.

e.g. abiotic factors like weathere.g. abiotic factors like weather

Types of Population Change Types of Population Change Curves in NatureCurves in Nature

Population sizes may stay the same, increase, Population sizes may stay the same, increase, decrease, vary in regular cycles, or change decrease, vary in regular cycles, or change erratically.erratically. StableStable: fluctuates slightly above and below carrying : fluctuates slightly above and below carrying

capacity.capacity. IrruptiveIrruptive: populations explode and then crash to a : populations explode and then crash to a

more stable level.more stable level. CyclicCyclic: populations fluctuate and regular cyclic or : populations fluctuate and regular cyclic or

boom-and-bust cycles.boom-and-bust cycles. IrregularIrregular: erratic changes possibly due to chaos or : erratic changes possibly due to chaos or

drastic change. drastic change.

Types of Population Change Types of Population Change Curves in NatureCurves in Nature

Population sizes often vary in regular cycles Population sizes often vary in regular cycles when the predator and prey populations are when the predator and prey populations are controlled by the scarcity of resources.controlled by the scarcity of resources.

Figure 8-7Figure 8-7

Question of the dayQuestion of the day

When a population’s growth rate changes When a population’s growth rate changes to match local conditions, it is known as to match local conditions, it is known as

a.a. Exponential growthExponential growth

b.b. Density-independent growthDensity-independent growth

c.c. natalitynatality

d.d. Logistic growthLogistic growth

e.e. Pioneer growthPioneer growth

NOTESNOTES

Section 9-2Section 9-2

Reproductive Patterns & Survival Reproductive Patterns & Survival

REPRODUCTIVE PATTERNSREPRODUCTIVE PATTERNS Some species reproduce without having sex Some species reproduce without having sex

(asexual).(asexual). Offspring are exact genetic copies (clones).Offspring are exact genetic copies (clones).

Others reproduce by having sex (sexual).Others reproduce by having sex (sexual). Genetic material is mixture of two individuals.Genetic material is mixture of two individuals. Disadvantages: males do not give birth, increase Disadvantages: males do not give birth, increase

chance of genetic errors and defects, courtship chance of genetic errors and defects, courtship and mating rituals can be costly.and mating rituals can be costly.

Major advantages: genetic diversity, offspring Major advantages: genetic diversity, offspring protection.protection.

Reproductive Patterns:Reproductive Patterns:Opportunists and CompetitorsOpportunists and Competitors

Large number of Large number of smaller offspring with smaller offspring with little parental care (r-little parental care (r-selected species).selected species).

Fewer, larger Fewer, larger offspring with higher offspring with higher invested parental care invested parental care (K-selected species).(K-selected species).

Figure 8-9Figure 8-9

r - Strategistsr - Strategists Most of their time is in Most of their time is in

exponential growth. High exponential growth. High growth rate (r)growth rate (r)

Max. reproductive lifeMax. reproductive life

Minimum life spanMinimum life span

Pop. size fluctuates Pop. size fluctuates wildly above & below wildly above & below

carrying capacity – (K)carrying capacity – (K)

Generalist nicheGeneralist niche

K

K - StrategistsK - Strategists Maintain population Maintain population

at carrying capacity at carrying capacity (K)(K)

Maximize lifespanMaximize lifespan

Lower population Lower population growth rate (r)growth rate (r)

Specialist nicheSpecialist niche

K

Reproductive PatternsReproductive Patterns

r-selected species tend to be opportunists r-selected species tend to be opportunists while K-selected species tend to be while K-selected species tend to be competitors.competitors.

Figure 8-10Figure 8-10

Survivorship CurvesSurvivorship Curves Survivorship curves represent the age Survivorship curves represent the age

structure of a populationstructure of a population.. Type 1: Type 1: Late loss populationLate loss population live to an old age. live to an old age.

Usually Usually K-strategistsK-strategists

Type 2: Type 2: Constant loss populationConstant loss population die at all ages. die at all ages. Usually Usually intermediate reproductive strategies intermediate reproductive strategies

Type 3: Type 3: Most members of Most members of early loss populationearly loss population, , die at young ages. Usually die at young ages. Usually r-strategistsr-strategists

Survivorship CurvesSurvivorship Curves

The populations The populations of different of different species vary in species vary in how long how long individual individual members typically members typically live.live.

Figure 8-11Figure 8-11

NOTESNOTES

Section 9-3Section 9-3

Effects of Genetic Variations on Effects of Genetic Variations on Population SizePopulation Size

EFFECTS OF GENETIC VARIATIONEFFECTS OF GENETIC VARIATION Small, isolated populations are most vulnerableSmall, isolated populations are most vulnerable

Founder Effect Founder Effect – a few individuals colonize a – a few individuals colonize a geographically isolated habitat. Ex. geographically isolated habitat. Ex.

• Limited genetic diversity may threaten the survival of the Limited genetic diversity may threaten the survival of the population. population.

Demographic BottleneckDemographic Bottleneck: a few individuals survive a : a few individuals survive a catastrophe. catastrophe.

• Lack of genetic diversity limits the ability to rebuild the Lack of genetic diversity limits the ability to rebuild the population population

Genetic DriftGenetic Drift: random changes in the gene frequencies lead : random changes in the gene frequencies lead to unequal reproductive success. to unequal reproductive success.