Unit 3 Populations

Populations change over time in reaction to a variety of factors

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Unit 3 Populations Videos / Clips

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Jordan Smedes Video Notes

Unit 3 Populations

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Supplemental - Feel free to add!

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3.1 Generalist vs. Specialist

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3.2 K - selected & r - selected Species

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3.3 Survivorship Curve

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3.4 Carrying Capacity

Serengeti: Nature’s Living Laboratory

3.5 Population Growth & Resource Availability

Texas Mosquito Mystery Crash Course #2

The Science of Overpopulation

World Population

* I also like to show World in the Balance - Population Paradox here. It’s not available to stream any more, but it gives students a snapshot of what things looked like in several different countries over a decade ago. I close the unit with Don’t Panic, which is more current.

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3.6 Age Structure Diagrams

7 Billion People

Earth’s Most Typical Person

Population Pyramids: Powerful Predictors of the Future - (TED Ed)

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3.7 Total Fertility Rate

Global Population Growth: Box by Box

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3.8 Human Population Dynamics

Human Population through Time

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3.9 Demographic Transition

Don’t Panic - GapMinder

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Bozeman Science Videos - Review

012 - Population Ecology

013 - Human Population Dynamics

014 - Human Population Size

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Videos

Population Pyramid Ted talk

Niche partitioning and species coexistence (3.1)

HHMI Serengeti - survivorship curves

What is a population?

• Group of individuals…..
• Of the same species
• Living in the same area
• Using the same resources
• Responding to the same stimuli

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Topic 3.1 Generalist and Specialist Populations

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Identify differences between generalist and specialist species

• Specialists species tend to be advantaged in habitats that remain constant.
• Generalist species tend to advantaged in habitats that are changing

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Topic 3.2 K-selected r-selected species

Identify differences between k- and r- selected species

• K-selected species tend to be large, have few offspring per reproduction event, live in stable environments, expend significant energy for each offspring, mature after many years of extended youth and parental care, have long life spans/life expectancy, and reproduce more than once in their lifetime. Competition for resources in K-selected species’ habitats is usually relatively high.
• r-selected species tend to be small, have many offspring, expend or invest minimal energy for each offspring, mature early, have short life spans, and may reproduce only once in their lifetime. Competition for resources in r-selected species’ habitats is typically relatively low.
• Biotic potential refers to the maximum reproductive rate of a population in ideal conditions.
• Many species have reproductive strategies that are not uniquely r-selected or K-selected, or they change in different conditions at different times.
• K-selected species are typically more adversely affected by invasive species than r-selected species, which are minimally affected by invasive species. Most invasive species are r-selected species.

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Topic 3.2 K-selected r-selected species

Life history/Reproductive strategies

• Life history/Reproductive strategies influence growth rate of a population
• age of reproduction
• number of offspring
• amount of parental care
• energy cost of reproduction

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• Life history/Reproductive strategies are shaped by evolution, natural selection

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• Two main life history/reproductive strategies- r selected, k selected

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• Many species have reproductive strategies that are not uniquely r-selected or K-selected, or they change in different conditions at different times.

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J shaped- r selected species

S shaped- k selected species

K-selected species

• few offspring per reproduction event
• Do best in constant/stable conditions
• Put in significant energy for each offspring
• mature after many years of extended youth and parental care
• have long life spans/life expectancy, and reproduce more than once in their lifetime.
• High Competition for resources in K-selected species’ habitats
• Density-dependant mortality
• S shaped population growth curve
• Stable Populations are close to carrying capacity (K) over long periods of time
• Exhibit type 1 or 2 survivorship curve
• Examples- humans, large trees, polar bears, elephants, most mammals and birds

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r-selected species

• small
• have many offspring
• expend or invest minimal energy for each offspring
• mature early
• Short life spans
• Reproduce only once in their lifetime.
• Poor competitors- Competition for resources in habitats is low.
• Density independent mortality
• Population not stable, does not hover around K, cycle between rapid growth and die offs
• J shaped population growth curve (exponential growth)
• Show a Type 3 survivorship curve

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• Examples - bacteria, algae, annual plants, dandelions, insects, cockroaches, rodents, oysters

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Invasive species

• Threaten the biodiversity of ecosystems worldwide

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• Transported via Ships, Crates/Cargo containers, Pets or food sources let loose, Planted as ornamentals

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• Eat/Kill native species: Northern Snakehead, Wild Boar, Brown snakes, Emerald Ash borer, Asian longhorn beetle, Sea lamprey

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• Outcompete native species

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• Examples Asian carp, zebra mussels/quagga mussels, Japanese knotweed, kudzu

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• Can change the entire ecosystem!!

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Zebra Mussels

• Native to freshwater rivers in E. Europe and W. Asia
• Found in the US in michigan in 19888
• Spread through great lakes from minnesota to gulf of mexico, now in Nevada,
• Came on ballast water on vessels from Europe
• The anchor themselves on native mussels making it impossible for them to function
• Increible filters- filter out algae which would be food for native microscopic organisms.
• Stop the spread
• Good boat hygiene
• Do not transport water from live wells and bait buckets from one waterbody to another

Asian Carp and the great lakes

• Fish are native from southern China to eastern Russia.
• Eat 5-20% body weight/day

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• The US brought Asian carp over to see if the planktivores—bighead and silver carp—could provide a non-chemical, environmentally friendly way to remove algae from wastewater treatment ponds.

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• Bighead and Silver carp - filter feeders, eat plankton, which native mussels and fish depend on

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• Spread by jumping over barriers, low lying dams, and release of live bait containing young carp

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• Excaped from Mississippi-connected ponds, in the mississippi river, they can go almost anywhere—from the Gulf of Mexico inland as far as Minnesota, Oklahoma, and Pennsylvania, and out through the five Great Lakes to the North Atlantic—because most of the country’s major water bodies were connected to facilitate transportation.

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• Efforts have focused on protecting the Great Lakes. The fear is that the invaders will out-compete native fish in the lakes, leading to the decline of a commercial and sport fishery said to be worth at least $7 billion.

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Invasive species video

• Asian carp BBC, jumping - 2 mins
• Why do the carp jump when boats go by?
• Stunned asian carp leap from kentucky lake 1 min

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• Strange days on planet earth 53 mins
• For each species
• how did it get here
• how does it reproduce
• how is it studied
• how are humans increasing the rate of spread of invasives.

The Calumet River meets Lake Michigan in Chicago. This is where the carp Anderson and Brown caught could have entered the lake. Credit: Alyssa Schukar for Undark

https://www.scientificamerican.com/article/navigating-a-sea-of-superlatives-in-pursuit-of-the-asian-carp/

3.3 Survivorship Curves

• A survivorship curve is a line that displays the relative survival rates of a cohort—a group of individuals of the same age—in a population, from birth to the maximum age reached by any one cohort member. There are Type I, Type II, and Type III curves.

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• Survivorship curves differ for K-selected and r-selected species, with K-selected species typically following a Type I or Type II curve and r-selected species following a Type III curve.

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Draw or insert a image of survivorship curve on right side of notes

Survivorship curves

Type 1 - high survivorship to old age, then rapidly decreasing survivorship (dying) (high parental care- K selected)

Type 2- survivorship decreases at a regular,steady rate

Type 3 - high mortality early in life, but those that survive early years live a long life. (low parental care- r selected)

High Parental Care (K selected)

Low Parental Care (r selected)

Topic 3.4 Carrying Capacity

Describe carrying capacity

Describe the impact of carrying capacity on ecosystems

• When a population exceeds its carrying capacity (carrying capacity can be denoted as (K), overshoot occurs. There are environmental impacts of population overshoot, including resource depletion.

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• A major ecological effect of population overshoot is dieback of the population (often severe to catastrophic) because the lack of available resources leads to famine, disease, and/or conflict.

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3.4 Carrying Capacity

Population size is affected by . . .

• Limiting factors (from unit 2 too)
• Density dependent factors -the size of the population will influence and individuals probability of survival
• Effects are more significant as population grows
• Any limiting resources- Competition, Predation, disease
• Density independent factors- the size of the population has no effect on the individual's probability of survival- effects the same percentage no matter the density
• Any Environmental stressor (earthquake, tsunami, volcanic eruption, fire, landslide, pesticides, habitat destruction)

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• Carrying capacity- (K) the limit to the number of individuals that can exist in a population

Carrying Capacity

• Carrying Capacity is determined by biotic potential (maximum reproductive rate of a population)

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• As population reaches carrying capacity, growth rate decreases because resources become more scarce, among other factors
• Which letter is the biotic potential? (A)
• Which letter is the max number of individuals that can be supported on a long term basis? (E)

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• Population Size (N)
• Population density
• number of individuals/ area
• Aquatic - individuals/ volume

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• Population Distribution
• No pattern to growth - Forest
• Uniform growth -plantation/ farms
• Clumped distribution- schooling fish, herding animals, flocking birds

Why would different types of dispersion occur?

3.5 Population Growth and Resource Availability

Explain how resource availability affects population growth

• Population growth is limited by environmental factors, especially by the available resources and space.
• Resource availability and the total resource base are limited and finite over all scales of time.
• When the resources needed by a population for growth are abundant, population growth usually accelerates.
• When the resource base of a population shrinks, the increased potential for unequal distribution of resources will ultimately result in increased mortality, decreased fecundity, or both, resulting in population growth declining to, or below, carrying capacity.

Population Growth Modules

• Population growth modules- math equations that predict population size at any moment in time
• Rapid growth→ when not limited by resources
• What are some limiting resources- think back to unit 2
• Population growth rate-number of offspring an individual can produce in a given time period, minus the death of the individual or its offspring
• Intrinsic growth rate- r - Under ideal conditions, with unlimited resources, every population has a max potential for growth
• Ideal conditions for rapid growth-
• Short generation time
• Reproduce early in life
• Reproduce many times
• Many offspring (high fecundity)

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The Drama Correlation Law

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Spreadsheet for some of the questions on population math

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Calculating Exponential Growth N_t = N_o e^rt

N₀ = Initial population size

r = rate of growth

e = a constant (2.7)

t = amount of time

N_t = Final population size

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Consider a population of mice that has an initial population size of 20 individuals. The intrinsic rate of growth for mice is r=0.2 (or 20%), meaning each mouse produces a net increase of 0.2 mice each year. Predict the size of the mouse population 5 years from now. ¡

N_t = N_o e^rt

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N_t = (20) (2.7^(0.2)(5))

N_t = (20) (2.7¹)

N_t = 54.4 mice

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J shaped- r selected species

S shaped- k selected species

Even MORE realistic

•Populations tend to overshoot K

•This is followed by a die-off or population crash

• If food becomes scarce, the population will experience an overshoot by becoming larger than the spring carrying capacity and will result in a die-off, or population crash.

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Population fluctuations

• Stable- fluctuates slightly above and below carrying capacity
• Tropical rainforest
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• Irrupt- usually stable, but sometimes explodes then crashes
• Algae, insects, due to seasonal changes, nutrient availability

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• Cyclic- rise and fall in predictable pattern
• Predator/prey
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• Irregular - no recurring pattern

Video Texas Mosquito mystery crash course

www.youtube.com/watch?v=RBOsqmBQBQk

Population Growth Rates

FRQ Practice time

�The zebra mussel is originally native to the Black and Caspian Seas of Asia. Zebra mussels were first detected in the Hudson River of New York in 1991. Before the arrival of zebra mussels, the Hudson River supported populations of native unionid mussels.�(a) Describe one way an invasive species, such as the zebra mussel, can decrease the carrying capacity for a native species in an ecosystem.�

Ok- so you just read the prompt….. What do you “get” what do you “not get”…. On the AP exam I can’t help you…. So, using what you’ve learned how can you think through this???

Answer (a):

• The response describes one way that invasive species can decrease the carrying capacity for native species in an ecosystem, such as:
• Invasive species can prey on the food sources of the native species. (describe situation)
• Invasive species can outcompete native species for resources such as food or water. (describe)
• Invasive species can outcompete native species for habitat. (how so)
• Invasive species can act as pathogens for the food sources of the native species, reducing the amount of food available for the native species.

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Below are the things you could have chosen to DESCRIBE… not just write the one sentence.

b) Identify one characteristic of an r-selected species that could increase the likelihood of the r-selected species being a more successful invasive species than K-selected species.

Just IDENTIFY… no extra info needed. Don’t waste time!

Answer (b)

• If the response contains more than one characteristic, only the first characteristic is scored.

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• Higher reproductive rates
• Shorter gestation periods
• Thrives in disturbed/changing environments
• Matures quickly
• More offspring
• More reproductive events in a life span
• Shorter generation times

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C.

• Based on the data shown in the table, calculate the percent change in the population density of unionid mussels from 1991 to 1997. Show your work.
• Based on the pattern shown in the table, calculate the percent change in the population density of zebra mussels from 2009 to 2015.

• The students must show their work for full credit.
• Need set-up (or no credit)
• Need x 100… or no credit (really- not joking… show your work)

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C (i)

C (ii)

• (d) Scientists want to reduce the population of zebra mussels in the Hudson River.
• (i) Propose a realistic solution for reducing the zebra mussel population in the Hudson River.

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• (ii) Describe one potential negative ecological consequence of your proposed solution for reducing the zebra mussel population in the Hudson River.

So these relate to each other!

• D (i)
• Introduce a predator to eat the zebra mussels
• Introduce a chemical to kill the zebra mussels
• Introduce a pathogen to kill the zebra mussels
• Physically remove the zebra mussels

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• D (ii)

Unit 3 populations

Human populations change in reaction to a variety of factors, including social and cultural factors

3.6 Age Structure Diagrams

• Population growth rates can be interpreted from age structure diagrams by the shape of the structure.

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• A rapidly growing population will, as a rule, have a higher proportion of younger people compared to stable or declining populations.

Factors that drive Human population growth

• Demography -the study of human populations and population trends
• Changes is population size
• Immigration In
• Emmigration - Exit
• Net migration rate
• Population
• Age structure
• Affected by Growth Rate = (Birth rate + immigration) - (death rate + emigration)
• Migration
• Fertility
• Life expectancy

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Population Age Structures diagrams

Age structure diagram-

Groupings by age and sex

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•Shows if a population is growing or shrinking and the males vs. females

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Population sex ratios

• Usually 50/50
• Some populations have many more females (fig wasps have 20:1 ratio)
• More females = higher population growth
• Environmental factors can affect sex ratios (chemical/temperature changes)

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Intersex

Intersex (sometimes called “Differences in Sex Development,” or DSD) describes diversity in sex characteristics whereby reproductive organs, genitals, or other sexual anatomy differ from traditional expectations for female or male. Sometimes intersex traits are noticed at birth and sometimes not until puberty or later. This is not the same as transgender, as sex development is different from gender identity. Intersex can be used as an identity term for someone with one of these traits. Intersex people may identify with a range of sexual orientations and gender identities.

Sex- which refers to the different biological and physiological characteristics of females, males and intersex persons, such as chromosomes, hormones and reproductive organs.

Gender- Gender refers to the characteristics of women, men, girls and boys that are socially constructed. This includes norms, behaviours and roles associated with being a woman, man, girl or boy, as well as relationships with each other. As a social construct, gender varies from society to society and can change over time.

Gender and sex are related to but different from gender identity. Gender identity refers to a person’s deeply felt, internal and individual experience of gender, which may or may not correspond to the person’s physiology or designated sex at birth.

Guevedoces - 2 min pbs - Dominican Republic known as 'guevedoces', who are born looking like girls but grow up to become men, all because of a misfiring of the gender defining hormone testosterone long before birth.

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•Animated pyramids: http://www.swissinfo.ch/blob/42152854/6f002b6af069e92ecbb1bd7a3b3e9f2c/int-populationstrucutres-en-data.gif

https://www.census.gov/dataviz/visualizations/055/

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Topic 3.7 Total Fertility Rate

• Total fertility rate (TFR) is affected by the age at which females have their first child, educational opportunities for females, access to family planning, and government acts and policies.

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• If fertility rate is at replacement levels, a population is considered relatively stable

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• Factors associated with infant mortality rates include whether mothers have access to good healthcare and nutrition. Changes in these factors can lead to changes in infant mortality rates over time.

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• Crude growth rate- net number added per 1,000 individuals per year
• Crude birth rate minus the crude death rate
• Crude Birth Rate- number of births per 1,000 individuals “crude” because population age structure is not taken into account
• Crude death rate- number of deaths per 1,000 individuals

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• Total fertility rate (TFR)-average number of children expected to be born to women throughout her childbearing years
• Doubling time- number of years it takes for a population to double, assuming a constant rate of natural increase
• TFR Developed countries
• level about 2.0 due to high levels of industrialization and income
• TFR Developing countries
• 2.2 or even greater is necessary due to high levels of infant/child mortality

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The difference between when women start families biggest reasons is education!

Women with college degrees have children an average of seven years later than those without — and often use the years in between to finish school and build their careers and incomes.

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3.8 Human Population dynamics

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7 Billion People

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Earth’s Most Typical Person

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Watch Hans Rosling: 200 Countries, 200 Years, 4 minutes (on hw)

Don’t panic Hans Rosling 58 mins (not on HW)

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Human Population Through Time—AMNH (6:24) https://www.youtube.com/watch?time_continue=311&v=PUwmA3Q0_OE

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Topic 3.8 Human Population Dynamics

• Birth rates, infant mortality rates, and overall death rates, access to family planning, access to good nutrition, access to education, and postponement of marriage all affect whether a human population is growing or declining.
• Factors limiting global human population include the Earth’s carrying capacity and the basic factors that limit human population growth as set forth by Malthusian theory.
• Population growth can be affected by both density-independent factors, such as major storms, fires, heat waves, or droughts, and density-dependent factors, such as access to clean water and air, food availability, disease transmission, or territory size.
• The rule of 70 states that dividing the number 70 by the percentage population growth rate approximates the population’s doubling time.

Are we already exceeding earth's carrying capacity?

Yes!

• Malthus (1798): human pop is growing exponentially while food supply grows linearly.
• Many agree: demand for resources must soon outstrip our supply!
• Supply of intellect is growing as well--Innovation and creativity

No

• Technological advances can increase carrying capacity

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Scientists disagree on earths carrying

Factors that affect if population is growing or declining

• Birth rates
• Infant Mortality rates
• leading causes- birth defects, preterm birth and low birth weight, maternal pregnancy complications SIDS, injury
• Overall death rates
• Access to health care- Watch how the measles outbreak spreads when kids get vaccinated – and when they don't
• Access to Family planning
• WHO family planning stats
• Family planning is “the ability of individuals and couples to anticipate and attain their desired number of children and the spacing and timing of their births.
• It is achieved through use of contraceptive methods and treatment of involuntary infertility.
• Family planning serves three needs
• It helps couples avoid unintended pregnancies
• Reduces spread of STDs
• By reducing the problem of STDs it helps reduce rates of infertility

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Factors affect if population is growing or declining

• Access to good nutrition -
• Food deserts
• Can you cook at home?
• Percent of time you eat out?
• Access to education
• Women who are educated have babies later, have less babies, babies have more opportunity
• Barriers to education around the world
• Lack of funding, No classrooms, Lack of learning materials, Gender, Distance from home, Hungry and poor nutrition, access to menstrual products
• https://www.globalcitizen.org/en/content/10-barriers-to-education-around-the-world-2/

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• Postponement of marriage and/or having children
• Women who wait until age 30 to marry make much more money, and have fewer kids
• Cultural
• Religion plays a determining role in fertility rates in both developed and developing nations. Less-religious women typically having fewer kids, and it's common for immigrants and religious women in secular, developed countries to have more children than the norm in that culture

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Food Deserts - food desert is an area that has limited access to affordable and nutritious food,^[1][2][3] in contrast with an area with higher access to supermarkets or vegetable shops with fresh foods, which is called a food oasis.^[4]The designation considers the type and quality of food available to the population, in addition to the accessibility of the food through the size and proximity of the food stores.^[5]

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Hungry planet- What the world eats

Photos

•One child policy http://www.nytimes.com/2015/10/30/world/asia/china-end-one-child-policy.html

https://www.nytimes.com/interactive/2018/08/04/upshot/up-birth-age-gap.html•

How we arrived at a Childless Future: https://www.axios.com/how-we-arrived-at-a-childless-future-5e72abef-87d8-45b4-aaca-69bf8f994b0d.html

Population Growth

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Doubling Time- time requires for a population to double in size

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3.9 Demographic Transitions

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• The demographic transition refers to the transition from high to lower birth and death rates in a country or region as development occurs and that country moves from a preindustrial to an industrialized economic system. This transition is typically demonstrated through a four-stage demographic transition model (DTM).

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• Characteristics of developing countries include higher infant mortality rates and more children in the workforce than developed countries.

3.9 Demographic Transitions

Stage ONE: No/Slow Growth

• CBR = CDR
• Short life expectancy, high infant mortality
• Disease, lack of health care, poor sanitation
• US/Europe: before late 18^th Almost no countries now in Stage 1

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Stage TWO: Rapid Growth

• Death rates decline
• Improved health care, access to water & food, vaccinations
• Fertility rates remain high
• Imbalance
• US early 19^th, India now

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Stage THREE: Stable Growth

• Economy/Education improves
• Family income up, #births declines
• More birth control availability
• CBR lowers to = CDR again

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Stage FOUR: Declining Growth

• CBR < CDR
• High affluence/economic development
• More elderly
• Govt may encourage immigration or $$ incentives to have more children

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Not part of the CED

Affluence

• More resources used per person
• HOWEVER…
• More wealth (higher GDP) can lead to environmental improvements and increased efficiency

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Technology

• Destructive: New toxic chemicals, increased resource extraction, manufactured “needs”
• Beneficial: Green solutions that increase efficiency and lower impact (hybrid car)

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Practice problems