Chapter 3: Populations

Survivorship curves

Survivorship curves

It show age-distribution characteristics of species, reproductive strategies, and life history

Reproductive success

It is measured by how many organisms are able to mature and reproduce, with each survivorship curve representing a balance between natural resource limitations and interspecific and intraspecific competition

Carrying capacity (K)

It refers to the number of individuals that can be supported sustainably in a given area

Population dispersal pattern

It is how individuals or species of animal become distributed in different spaces over certain periods of time

Clumped

Some areas within a habitat are dense with organisms, while other areas contain few members

Random

Occurs in habitats where environmental conditions and resources are consistent

Uniform

Space is maximized between individuals to minimize competition

Biotic potential

The maximum reproductive capacity of an organism under optimum environmental conditions

Environmental Resistance

Any factor that inhibits an increase in the number of organisms in the population

J-Curve

It represents a population growth occurs in a new environment when the population density of an organism increases rapidly in an exponential or logarithmic form, but then stops abruptly as environmental resistance or another factor suddenly impacts the population growth

S-Curve

It occurs when, in a new environment, the population density of an organism initially increases slowly but then stabilizes due to the finite amount of resources available

Limiting Factor

It can be any resource or environmental condition that limits the abundance, distribution, and/or growth of a population

Density-dependent limiting factors

These are factors whose effects on the size or growth of the population vary with the density of the population

Density-independent factors

These are factors that limit the size of a population, and their effects are not dependent on the number of individuals in the population

Rule of 70

It helps to explain the time periods involved in exponential population growth occurring at a constant rate

Doubling time

It is the amount of time it takes for a population to double in size

Age-structure diagrams

These are determined by birth rate, generation time, death rate, and sex ratios

Pyramid-shaped age-structure diagram

It indicates that the population has high birth rates and the majority of the population is in the reproductive age group

Bell shape age-structure diagram

It indicates that pre-reproductive and reproductive age groups are more nearly equal, with the post-reproductive group being smallest due to mortality

Urn-Shaped age-structure diagram

It indicates that the post-reproductive group is largest and the pre-reproductive group is smallest, a result of the birth rates falling below the death rate, and is characteristic of declining populations

Total fertility rate (TFR)

The average number of children that each woman will have during her lifetime

Earth Wisdom

Natural cycles that can serve as a model for human behavior

Frontier Worldview

Viewed undeveloped land as a hostile wilderness to be cleared and planted, then exploited for its resources as quickly as possible

Planetary Management

Beliefs that as the planets most important species, we are in charge of Earth

Earth Wisdom

Beliefs that nature exists for all Earths species and we are not in charge of Earth; resources are limited and should not be wasted

Demographic transition

It is the transition from high birth and death rates to lower birth and death rates as a country or region develops from a pre-industrial to an industrialized economic system

Stage 1

Pre-Industrial (High Stationary)

Stage 2

Transitional (Early Expanding)

Stage 3

Industrial (Late Expanding)

Stage 4

Post-Industrial (Low Stationary)

Stage 5

Sub-Replacement Fertility (Declining)

Stage 5: Sub-Replacement Fertility (Declining)

• Some theorists believe a fifth stage is needed to represent countries with sub-replacement fertility.

• Death rates exceed birth rates in most European and East Asian nations.

• Unless mass immigration continues, population aging and decline will occur in this stage.

Stage 4: Post-Industrial (Low Stationary)

• Population growth is zero when birth and death rates are equal.

• The standard of living is higher, and birth and death rates are low.

• In some countries, birth rates are lower than mortality rates, resulting in population losses.

Stage 3: Industrial (Late Expanding)

• Urbanization reduces economic incentives for large families.

• Urban families are increasingly discouraged from having large families as costs rise.

• Female education and employment lower birth rates.

• Leisure time and food are not priorities.

Stage 2: Transitional (Early Expanding)

• This stage occurs after the start of industrialization.

• Hygiene, medical advances, sanitation, cleaner water, vaccinations, and higher education lower the death rate, resulting in a significant population increase.

• Population rises rapidly.

Stage 1: Pre-Industrial (High Stationary)

• Poor agricultural practices, pestilence, and living conditions make food scarce and medical care is poor.

• High birth rates replace high mortality, resulting in low population growth.

• Sub-Saharan Africa has 54% of the world's AIDS-HIV cases but only 6% of the population.

Present to 2050 C.E.

Estimates are as high as 9.8 billion.

Earth Wisdom

1650 C.E. to present

• Currently ~ 7.5 billion humans.

• In 1650 C.E., the growth rate was ~ 0.1%.

• Today it is ~ 1.2%.

  • Planetary Management

1300 C.E. to 1650 C.E.

• ~ 600 million humans.

• Plagues reduced population growth rate.

• Up to 25% mortality rates are attributed to the plagues that reached their peak in the mid-1600s.

0 C.E. to 1300 C.E.

• ~ 500 million humans.

• Population rate increased during the Middle Ages because new habitats were discovered.

• Factors that reduced population growth rate during this time were famines, wars, and disease

• Frontier Worldview

5000 B.C.E. to 1 B.C.E.

• ~ 200 million humans.

• Rate of population growth during this period was about 0.03 to 0.05%, compared with today’s growth rate of 1.3%.

• Frontier Worldview

8000 B.C.E. to 5000 B.C.E.

• ~ 50 million humans.

• Increases due to advances in agriculture, domestication of animals, and the end of a nomadic lifestyle.

• Earth Wisdom

Before Agricultural Revolution

• ~ 1 million to 3 million humans.

• Hunter-gatherer lifestyle.

• Earth Wisdom

Birth Rate (%) = [(total births/total population)] × 100

Birth Rate Formula

CBR = [(b ÷ p) × 1,000]

Crude Birth Rate Formula

Death Rate (%) = [(total deaths/total population)]× 100

Death Rate Formula

CDR = [(d ÷ p) × 1,000]

Crude Death Rate Formula

Doubling Time = 70/% growth rate

Doubling Time Formula

Emigration = number leaving a population

Emigration Formula

Global Population Growth Rate (%) = [(CBR – CDR)]/10

Global Population Growth Rate Formula

Immigration = number entering a population

Immigration Formula

National Population Growth Rate (%) = [(CBR + immigration) – (CDR + emigration)]/10

National Population Growth Rate Formula

Percent Rate of Change = [(new # - old #)/old #] × 100

Percent Rate of Change Formula

Population Density = total population size/total area

Population Density Formula

Population Growth Rate Formula

dt= 70/r

To find how long it takes for a population to double in size we can use the following formula _________

Liebig’s law of the minimum

Based on _________, even if all other factors are favorable, the one that is least favorable will dictate the growth, abundance, or distribution of the population of a species.

Positive feedback loops

_________ stimulate change and are responsible for sudden or rapid changes within ecosystems.

Negative feedback loops

This often provide stability.

• Limiting factors can cause a negative feedback loop because populations cannot exceed the ecosystem's carrying capacity.

carrying capacity

This point of stabilization is known as the _____ of the environment, and it denotes the point at which the upward growth curve begins to level out

density-dependent

This type of population growth is termed “_________” since the growth rate depends on the number of organisms in the population.

density-dependent

This type of population growth rate is known as “_______,” a regulation of the growth rate is not tied to the population density until the resources are exhausted and the population growth crashes.

Type I - Late Loss

Reproduction occurs fairly early in life, with most deaths occurring at the limit of biological life span.

Type I - Late Loss

Low mortality at birth with a high probability of surviving to advanced age.

Type I - Late Loss

Death rates decrease in younger years due to advances in prenatal care, nutrition, disease prevention, and cures, including immunization.

Type II - Constant Loss

Individuals in all age categories have fairly uniform death rates, with predation being the primary cause of death.

Type II - Constant Loss

Typical of organisms that reach adult stages quickly.

Type III - Early Loss

Typical of species that have great numbers of offspring and reproduce for most of their lifetime.

Type III - Early Loss

Death is prevalent for younger members of the species due to environmental loss and predation and declines with age.

r-Strategists

• Not endangered

• Have many offspring and tend to overproduce

• Low parental care

• Mature rapidly

r-Strategists

• Population size limited by density-independent limiting factors, including climate, weather, natural disasters, and requirements for growth

• Short-lived

• Tend to be prey

• Tend to be small

r-Strategists

• Type III survivor curve

• Wide fluctuations in population density

K-Strategists

• Most endangered

• Have few offspring

• High parental care

• Mature slowly

K-Strategists

• Density-dependent limiting factors to population growth stem from intraspecific competition and include competition, predation, parasitism, and migration

• Long-lived

• Tend to be predator and prey

• Tend to be larger

K-Strategists

• Type I or II survivor curve

• Population size stabilizes near the carrying capacity.

Generalists

• Able to use a variety of environmental resources

• Adaptable to a wide range of environments

• Have a high level (range) of tolerance

Generalists

• Have an advantage when environmental conditions change

• Less likely to be extinct

Specialists

• Use specific set of resources

• Less adaptable due to specialized needs

• Have a low level of tolerance

Specialists

• Easily affected when environmental conditions change

• More likely to become extinct