Human Impacts on the BiospherePopulation Ecology

Lecturer: Chenyu Huang

Managing Canada Geese (1 of 3)

• Canada geese were hunted to near extinction in the late 1800s• Protection laws passed in early 1900s

• In recent decades, the number of geese has soared

• Michigan had about 9,000 of these birds• in 1970 and today has more than 300,000.

• Considered pests because they soil grassy areas in parks and golf courses

An Oakland, California park overrun by Canada geese

• Canada geese pose a more serious problem for air traffic- one of the species commonly involved in collisions with aircraft

In 2009, US Airways Flight 1549 floats in New York’s Hudson River aftercollisions with geese incapacitated both of its engines.

Managing Canada Geese

• Most Canada geese still migrate, but some populations have lost this trait• Biggest population increase has been among nonmigratory birds, living

near humans• Unnatural abundance of food• Unnatural lack of predators

• Wildlife managers looking for ways to reduce nonmigratory populations of Canada geese

Population Demographics (1 of 6)

PopulationGroup of organisms of the same species that live in the same area and interbreed.

• Ecology生態學• how populations interact with each other and the environment

• Demographics族群統計學• Statistics about a population’s traits

• Population size• Number of individuals in a population• Usually estimated using sampling techniques

Population Demographics (2 of 6)

• Plot sampling• Estimates total number of individuals in an area

Based on direct counts in a small part of the area

For example,measuring the number ofindividuals in several 1 unitsquare plots, averagenumber of individuals per plot,then multiplied by the size of thetotal area.

Plot sampling question:

• (Left) Sampling 16 square units • Total area =200 square units• Estimate: • Number of each species• 1.• 2.• 3.• 4.• 5.

Google forms: https://forms.gle/42V7SF6yNHKat5GS9

Mark–recapture sampling– Technique for sampling mobile

animal population size1) Some representatives of the population are

tagged and released. 2) After a time, a second sample of the

population is captured.3) The portion of marked animals in the

second sample is taken to be representative of those marked in the whole population.

Example, 100 deers were captured and released, later, the scientists capture 100 deer again. 50 of these deer were previously marked, implying that marked deer constitute half of the population. Total= 200 individuals

Mark–recapture sampling question:

• Suppose scientists capture, mark, and release500 deer in an area. Later, the scientists returnand again capture 500 deer. They find 150 ofthese deer were previously marked.

• How many individuals in total population ?• Google forms: https://forms.gle/zudw2vGqunmF3aGDA

Population Demographics (3 of 6)

• Population density• Number of individuals per unit area

or volume

• Population distribution• Describes the location of individuals

relative to one another Clumped distribution Equal distance apart Random distribution

Population Demographics (4 of 6)

• Most populations have clumped distribution• Due to uneven distribution of resources

Such as a water source, or sunshine on the south face of a mountain• Limited dispersal ability increases likelihood of a clumped distribution• Asexual reproduction (無性生殖) also results in clumping

Population Demographics (5 of 6)

• Near-uniform distribution• Competition for limited resources can produce this distribution• Example: creosote bushes in deserts

• Random distribution• Occurs when resources are uniformly available• No benefit or harm from proximity to others• Example: dandelion seeds blown onto a lawn

Population Demographics (6 of 6)

• Age structure• Refers to the number of individuals in

various age categories• Individuals are often characterized as pre-

reproductive, reproductive, or post-reproductive

• Pre-reproductive and reproductiveindividuals constitute a population’s reproductive base

• Timing of the study can influence observed demographics• Whether animals are breeding/nesting at

a given time, migrating, or other event

Definitions 1._________ Of a population, the number of individuals in each of several age categories.2._________ Statistics that describe a population.3._________ Study of how populations interact with one another and with their nonliving environment.4._________ Method of estimating population size of mobile animals by marking individuals, releasing them, then checking the proportion of marks among individuals later recaptured.5._________ Method of estimating population size of organisms that do not move much by making counts in small plots, and extrapolating from this to the number in the larger area.6._________ Number of individuals per unit area.7._________ Describes whether individuals are clumped, uniformly dispersed, or randomly dispersed in an area.8._________ Total number of individuals in a population.9._________ Of a population, all individuals who are of reproductive age or younger.

Reproductive baseDemographicsEcologyAge structurePopulation densityMark–recapture samplingPlot samplingPopulation distributionPopulation size

Google forms: https://forms.gle/Ei7x9DiGcX9eHs9p8

Modeling Population Growth

• Learning Objectives:• Give the equation that describes exponential

growth and explain what the terms in the equation mean.

• Define biotic potential生殖潛能 and give examples of organisms that differ in their biotic potential.

Modeling Population Growth

• Immigration• Arrival of new residents that previously belonged to another population

• Emigration• Departure of individuals who take up residence elsewhere

• In many animal species, young of one or both sexes emigrate to breed elsewhere (i.g., freshwater turtles)

• Seabirds typically breed where they were born

✔ Populations fluctuate in size as individuals come and go.

Modeling Population Growth (2 of 4)

• Zero population growth• Time period in which the number of births equals the number of deaths

• Per capita growth rate, r• Per capita birth rate minus per capita death rate

• If r remains constant and greater than zero:• Exponential growth will occur, which means that the• population’s size will increase by the same proportion

of its total in every successive time interval

Modeling Population Growth (3 of 4)

per capita rate of growth (r)of 0.4 per mouse per month and a population size of 2,000

a. 0.1b. 0.2c. 0.3d. 0.4e. 0.5

1.The per capita growth rate (r) is ____ per mouse per month in a population of 1,000 mice where 500 mice are born and 400 mice die monthly.

2.There will be approximately ____ mice in four months in a population of 1,000 mice where 500 mice are born and 400 mice die monthly.

a. 1,000

b. 1,100

c. 1,200

d. 1,300

e. 1,400

Ans=(500-400)/1000=0.1

Ans=(500-400)*4+1000=1400

Modeling Population Growth (4 of 4)

• Biotic potential生殖潛能 : the theoretical rate of population growthfor a population under ideal conditions (if essential resources were unlimited and there were no predators or pathogens)• Factors: reproductive age • Duration of reproductive years• number of offspring per reproduction event, affect the biotic potential

• Microbes (such as bacteria) have highest biotic potentials • Large-bodied mammals have some of the lowest

25% dying between division

Regardless of the species, populations seldom reach their biotic potential because of the effects of limiting factors.

No population can grow exponentially forever!!!!

Limits on Population Growth

Limits on Population Growth

• Density-dependent factors• Predation• Parasitism and disease• Competition for a limited resource• As density increases, birth rate slows and death rate rises

• Intraspecific competition (competition among members of the same species)• Has a detrimental effect on the species

Limits on Population Growth

Human Population Growthwww.census.gov/popclock

Human Population Growth

• Domestication of animals • Invention of agriculture

• More dependable food supply

• Innovations increased food supply stability and decreased the impact of diseases

• Use of fossil fuel energy opened the way for mechanized agriculture and improved food distribution systems

Human Population Growth

• Use of synthetic nitrogen fertilizersand synthetic pesticides dramatically increased crop yields

• Disease has historically dampened human population growth• Increased understanding about microorganisms and illness

Led to improvements in food safety, sanitation, and medicine Example: pasteurizing food and drinks

Human Population Growth

• Vaccines and antibiotics help prevent disease• Decline in death rates is occurring without an equivalent decline in

birth rates• Population projected to grow from seven billion to nine billion by 2050

Human Population Growth

• Most highly developed countries– Lowest fertility rates– Lowest infant mortality– Highest life expectancy

© 2019 Cengage. All rights reserved.

Critical Thinking Questions

The age structure diagrams for two hypothetical populations are shown below. Describe the growth rate of each populationDiscuss the current and future social and economic problems that each is likely to facehttps://forms.gle/PKFzwZSbkHKydtUQ9

© 2019 Cengage. All rights reserved.

Human Impacts on the Biosphere

Core Concepts-Systems

Systems: Complex properties arise from interactionsamong components of a biological system.• Plowing grasslands, cutting forests - soil erosion

altering the habitat• Raising the temperature of the land and seas

causes cascading effects by altering feeding,migration, and breeding patterns.

Human activities that alter one component of ahabitat can have long-term and long-range effects.

Core Concepts-Evolution

• Evolution演化: Evolution underlies the unity and diversity oflife. Unity(organism in common), diversity (different organism)

• All living species are products of an ongoing evolutionaryprocess that stretches back billions of years, and eachspecies has a unique combination of evolved traits thatsuit it to its habitat.

• Extinction removes that collection of traits from the worldforever. Humans have increased the frequency ofextinctions, and the extent and effects of these losses arenot fully known or understood.

Harmful Land Use Practices

DesertificationDeforestation

Debate:Dirty Palm oil?

How do we fix the palm oil problem? (Green peace)

單純抵制?並不是最好的解決方法

認證標章?

• FSC (Forest Stewardship Council )• PEFC(Programme for the Endorsement of Forest

Certification )• Rainforest Alliance Certified• NSF Sustainability Certified• Green Tick

https://forms.gle/WUJjk5KGuVGaRajC7

環保或永續發展可可、咖啡、生質燃料（biofuel）、棕櫚油、大豆和木材

Pollution

Pollutants: Natural or man-made substances released into soil, air, or water in greater than natural amounts

Airborne sulfur and nitrogen oxides-combine with water and fall as acidic precipitation

https://www.ted.com/talks/joseph_goffman_whatever_happened_to_acid_rain/transcript?language=zh-tw#t-77492

Acid rainpH of unpolluted rain water is 5 or higher• Acid rain can be ten times

more acidic• Consequences

Prevents fish eggs from developing、Kills adult fish、Burns tree leaves and alters the soil

Pollution-Bioaccumulation

In animals, pollutants accumulate in fatty tissues1. Amount increases over time2. Long-lived species have higher percentage of

pollutants in body tissues3. Older individuals have higher pollutant load

than younger individuals

Pollution-Bioaccumulation DDT

Rachel Louise Carson

https://www.youtube.com/watch?v=Ipbc-6IvMQI本來應該是蟲鳴鳥叫的春天?

Solid waste• Dump into oceans harms marine life• Trash was buried unground contaminates groundwater

Death by plastic

The year the earth change