Biol 364 Unit 1

Study guide for Bio 364 Unit 1 test

4 parameters that increase or decrease population size

Births, deaths, immigration, emigration

Exponential growth

-J-shaped growth curve

-Resources adundant/unlimited

-Ignores migration

-Density independent

-Typical for bacteria in culture, r-selected species, invasive species, insects, cormorants

-Intrinsic rate of increase = r = births - deaths

-Rate of growth = slope of curve = change in N/change in T =rN, r is a constant, N increases

Logistic growth

-S shaped growth curve

-models conditions with limited resources or other density dependent factors

-density dependent

-typical of k-selected species, endangered species, and flattening the curve of COVID

-K=carrying capacity

-Rate of growth = slope = rN (K-N/K)

-(K-N/K) serves as dampening factor

Density dependent factors

-have a stronger negative effect as population size increases

ex: lack of food, lack of space, disease, increased predation

-regulate the population

Density independent factors

-impacts the population the same no matter the size

ex: natural disasters

4 other growth models/deviations

1. Overshooting carrying capacity: leads to a crash, common in ungulate species on islands with no predators

2. Predator-prey population cycles: hares and lynx, hares increase and then lynx increase, then hare crash and lynx crash

3. Linear growth

4. Faster than exponential: humans through early 20th century? Covid at Calvin

Uses of population growth models

1. May fit real world data for certain scenarios

2. Important conceptually to understand real data that does or doesn’t fit the model

3. Changing parameters in the models can give insight into the behavior of biological systems, even if they aren’t perfect

4. Provide conceptual and mathematical basis for more advanced models and applications:

   1. studies of population dynamics

   2. sustained yield models

   3. ecotoxicology

   4. pandemic models

Metapopulation

Spatially separated subpopulations of the same species that interact through migration. Populations on a landscape scale.

Sink population

Deaths > Births, a subpopulation that survives through immigration

Source population

Births > Deaths, a subpopulation that individuals emigrate from to sustain sink populations

Thomas Robert Malthus (1766-1834) ideas

-Human growth is exponential

-Food production growth is arithmetic

-Human population with exceed food production

-Predicted famine in context of 18th/19th century Europe

-Influenced Darwin

Ehrlich

-Indefinite population growth will lead to catastrophe

-Population growth outpaces food production in developing countries

-Developed countries consume more than they produce so are overpopulated

-Not only starvation, but social and environmental problems will increase

-Humans must slow birth rate otherwise death rate will increase through war/famine/disease

Simon

-Children contribute more than they require

-Throughout history both the population and better living conditions have increased, no reason for the trend to change now

-all economic indicators are improving

-as humans need more resources, there might be short term setbacks, but in the long run human ingenuity will enable the use of more resources

-resources aren’t finite

Current world population

8.3 billion

World population increase/year

70-90 million

Population increase since I was born + in lifetime at 80 years old

1.7 billion

5.6 billion (12.2 total)

Human population growth model

Exponential growth

Date that population reached 1 billion

1800

Date that population reach 2 billion

1900ish

Carrying Capacity Increase Reasons for Humans

-Discovery of fire and tools

-Agricultural revolution

-Industrial revolution

End of century Population projection

-11-12 billion with predicted stabilization

-Most growth in less developed regions: Sub-Saharan Africa and Asia

Demographic Transition significance

-essential for limiting population growth

-has already occurred in some developed countries

-means population must increase before stabilization

Demographic trap

A country gets stuck in phase 2 or 3 with low death rates but birth rates don’t decrease so population growth continues

Demographic transition Phase 1

Predevelopment

-High birth rate

-High death rate

-Births=Deaths

-Low population

-Stable population

Demographic transition phase 2

Development progresses

-High birth rate

-Falling death rate

-Births>deaths

-Population grows

Demographic transition Phase 3

Development progresses

-Falling birth rates

-Stable low death rates

-Births>deaths

-Population increases

Demographic transition Phase 4

Developed

-stable low birth rates

-stable low death rates

-births=deaths

-high, stable population

Pronatalist forces

-lack of power for women

-low cost of having children

-children provide status and security

-high infant mortality

-religion

Causes for decline in births in developed countries

-improved social, educational, and economic status for women

-greater say for women in family decisions

-more women working outside the home

-social security and political stability allow parents to plan for future without relying on children

-contraception

-reproductive education

-government incentives

-high cost of raising children

Reasons for decline in deaths with development

-Improved medicine and healthcare

-Improved nutrition and agriculture

-Improved sanitation: clean water and sewage disposal

I=PAT

For environmental impacts of a population

I = impact (environmental degradation, resource depletion)

P = population

A = affluence (consumption/person) (energy, materials, information, transformation)

T = technology (impacts/consumption)

Ways to reduce impact from PAT

P=population (slow population growth)

A=affluence (satisfy more with what we have, sublimate wants for greater good)

T=technology (shift to less harmful consumption, shrink energy and materials, substitute information for energy and materials)

Human footprint numbers

-transformed >40% of land

-added >30% CO2 to atmosphere

-use 40% NPP

-Since 1970, 68% decline in vertebrate populations

Main ways humans change earth

-agriculture

-industry

-recreation

-international trade

-hunting, fishing

-forestry

-grazing

-clearing land

-aerosols

-invasive species

-synthetic chemicals

Sustainable development

“Development that meets the needs of the present without compromising the ability of future generations to meet their needs”

“Changing consumption of resources through behavior and technology to meet the true needs of the present without compromising the ability of future generations, and other species, to meet their needs.”

Rubric for sustainability

Venn diagram with environment, economy, and community with health/sustainability in the center.

Cairns

-possibility of planetary state shift if human population and consumption continues to grow

-must live more sustainably to avoid tipping point in biosphere

-if tipping point does occur, state shift will make survival difficult and lead to die off

-earth has finite resources, indefinite growth of any kind is suicidal

-says humans must learn to live within scientific limits (change consumption patterns and slow population growth through government regulation)

Epidemiology

The study of the distribution and determinants of disease frequency in human populations

Key aspects:

-distribution: patterns in a population and what population

-determinants: causes

-frequency: in human populations, quantitative

Epidemiology goals

1. to determine the causes of disease

   1. new diseases

   2. outbreaks

   3. hidden causes or risk factors

   4. prevention and intervention requires knowing the cause

2. monitor trends and distributions in disease frequency (surveillance)

3. test the effectiveness of preventative or therapeutic measures

Epidemiological triad of disease distribution

-person (who is getting the disease) (epidemiology looks at disease among population groups, not individuals)

-time (when is the disease occurring and is frequency changing over time) (periodic and seasonal outbreaks) (long term (secular) trends over years or decades)

-place (where is the disease occurring) (place of exposure, provide clues about causal factors)

Pandemic

an epidemic on the worldwide scale

Epidemic

short-term (sudden) outbreak of a disease above previous frequency in that population

Secular trend

long term trends (over years and decades) in a disease distribution

Periodic outbreaks

Increases in disease frequency at regular intervals/seasonally

Risk factors

Potential causal factors of a disease that need evaluating

Epidemiological triad of causation

-Agent (microbe, pollutant, nutritional deficiency, radiation)

-Host (generally people, look at demographics, genetics, physiological status, social and economic factors, behavior (exercise, diet, tobacco, etc.)

-Environment (surrounding physical, biological, and social environment)

Definition of a causal relationship

Factors form part of the complex of circumstances which increases the probability of occurrence of the disease and that a diminution of one or more of these factors decreases the frequency of the disease

Criteria for determining causation

1. Statistical probability: is the relationship statistically significant

2. time order: did the cause come before the effect

3. specificity: is a disease specific to a cause or produced by many

4. strength of association: relative risk (incidence in population exposed:incidence in population not exposed), is the effect little or big

5. Consistency upon replication: do studies agree

6. Predictive performance: do hypotheses drawn from this relationship predict what happens in new situations

7. coherence: biologically plausible and dose response

Risk

the likelihood of an unwanted occurrence coupled with an element of uncertainty about when the risk might occur

-what is unwanted depends on community values

-risk probabilities act over space, time, and population size

Risk assessment and three steps after

1. Risk assessment (for new chemicals or cleaning polluted sites)

2. risk management and mitigation

3. risk communication

4. risk ethics

RA steps

1. Hazard identification: identify chemicals that are potentially hazardous (identification is mandated by legislation, but actual testing only required for pesticides, very few industrial chemicals)

2. Dose-response assessment: determine Toxicity Reference Value (TRV), what amount is toxic?

3. Exposure assessment: how likely are people or animals to be exposed to the chemical?

4. Risk characterization: Risk Quotient=exposure/TRV, is RQ>1 suggests significant risk, RQ<1 no or minimal risk

RA uncertainties

-uncertainty in TRV due to extrapolating between species, ages, human population, beyond tested exposures

-uncertainty in exposure due to complex exposure pathway models and variable or unmeasured exposures

-In TRV and RQ due to applied safety factors which can sometimes overtake the real data

Loon study

1. Hazard identification: Mercury potential cause of reproductive issues for loons

2. Dose-Response: Lab study raised loon chicks and exposed them to mercury, those exposed to higher levels of mercury had decreased antibody production. Combined with 15 other studies on methyl Mercury and loons, TRVs were developed for productivity failure, impaired productivity, and impaired behavior

3. Exposure looked at mercury levels in fish across many Canadian lakes and was extrapolated to determine the resulting exposure in loons based on their diets and biomagnification

4. Calculated RQ values for each lake, determined that eastern Canada had a lot of lakes with RQ>1

One Health

The collaborative effort of multiple disciplines - working locally, nationally, and globally - to attain optimal health for humans, animals, and our environment

-integrates human, veterinary, and environmental health disciplines

-emphasizes increased communication and collaboration

-hopes integration of knowledge will lead to novel solutions

-infectious diseases increase in degraded environments

-decrease in biodiversity leads to more disease exposure and immunosuppression

-naive populations lack herd immunity

-RNA viruses more able to jump between species because they mutate quickly

One health conceptual model

Human health and well being inside robust and resilient economy inside environmental integrity

Ape case study

-West Africa ebola is often traced back to human contact with wildlife, especially ape carcasses

-WCS teaches locals to avoid touching and eating wildlife carcasses

-Hunters report ape carcasses to WCS and WCS tests carcasses for ebola

-allows ebola to be tracked and provided potential early warning system for crossover to humans

Pakistan case study

-Pakistan lacks good healthcare and surveillance infrastructure

-WCS working with locals to protect fragile environments

-WCS campaign to vaccinate cattle and domestic yaks against foot and mouth disease (FMD) to prevent spread to wildlife

-WCS surveillance of diseases in livestock that could possibly spread to humans, livestock, and wildlife

-WCS training local veterinarians in disease screening and standard reporting

-One health contributes to discussions around rebuilding Pakistan’s health infrastructure

Sickness in developing countries

80% waterborne disease or inadequate sanitation

worst in sub-saharan africa

People lacking sanitation

2 billion

People lacking safe drinking water

2 billion

Waterborne disease

-The pathogen is freeliving in water that is ingested

-Feco-oral (fecal contamination of water that is then ingested)

ex: giaardia, E. coli

Water washed/scarce disease

-Person to person transmission (direct touch or through surfaces) because of a lack of water for hygeine

-not enough water to bathe, wash hands, clean surfaces

-skin and eye infections

ex: scabies, pink eye

Water based disease

-Transmission via an aquatic intermediate host (snail, duck)

-multiplies in hosts, not free-living in water

ex: swimmer’s itch, guinea worm

Water related insect vector disease

-transmission by insects that breed in water or bite near water

ex: dengue, malaria

Disease prevention options

1. safe human excreta disposal

2. personal hygiene

3. domestic hygiene

4. food hygiene

5. water hygiene

6. Drainage

Malaria burden

700,000-2.7 million deaths per year

75% children in africa

2 deaths/minute

old numbers, have improved by 50%

Malaria regions

-41% of the world population is in areas where malaria is endemic

-wet tropics

-South America, Africa, southeast asia

Breaking Malaria Cycle

Host factors:

-immunity (partial after repeated infections)

—need to watch out for reactivation

—vaccines

-treatments

—medicine given to the sick and also those infected last year

-Rapid diagnosis

-Sickle cell

—those heterozygous for sickle cell are immune to malaria

-Behavior

—domestic hygiene, healthcare,

-Socioeconomic

—access to healthcare

—poverty

—traditional medicine

Environment factors:

-Bednets

-move livestock away from homes

-water management

—dump out buckets and tires (domestic hygiene)

—keep water flowing

—pesticides

—vegetation management (remove algae)

-Pesticides

—in natural areas

—Indoor residual spraying

—livestock

Malaria Vaccines?

-Hard to develop because the plasmodium ‘hides’ in liver and red blood cells and doesn’t put markers on the cell surfaces like viruses do

-It is also hard to replicate the plasmodium lifecycle in a lab environment

-Some new vaccines are proving to be effective and they build up an immune response that fights the plasmodium before it can enter the liver

Malaria drugs

-traditional mono therapies lose effectiveness because plasmodium becomes resistant

-new combination therapies that include artemisinin provide rapid treatment and plasmodium have not yet shown signs of resistance

-drugs are given to both the sick and those who were sick last year to avoid reactivation

-unfortunately, need is greater than production and funding

Oaxaca controls for Malaria

-Treating people sick the year before

-pyrethoid pesticide house spraying

-raking algae

-rapid field diagnosis

Indoor Residual Spraying

Environment health:

-indoors

-however, if available will likely be used outdoors

-persists a long time and is harmful

Human health:

-increased exposure increases breast cancer, miscarriages, and disrupts endocrine system

Vs pyrethoids:

-cheaper

-persists longer so it requires less spraying

WHO RA:

-saves net 3 lives in areas with high malaria mortality (24/1000 deaths)

-loses net 9 lives in areas with lower malaria mortality (12/1000)

Even if effective, not a cure all, malaria control requires many components

Microbiome

a community of microbes that naturally inhabits a particular area and encompasses all of the genetic material contained within it

Microbes/pathogens

-date back 3.5 billion years

-immune responses also ancient

-1/3 of biodiversity is pathogens

-types: prions, viruses, bacteria, fungi, protists, multicellular parasites

Innate response

-always on

-first line of defense

-rapid response

-general, not targeted

-causes inflammation

-lots of phagocytosis (engulfing pathogen)

ex: macrophage

Acquired response

-slow response

-specific activation of only the cells that recognize a specific antigen

-very targeted

-more effective

-efficient by only responding with what is needed

-improves with exposure (immunological memory)

ex: antibodies, t-cells

Clonal selection

Expansion in numbers of only the T or B cells that bind to that specific pathogen

Immunological memory

When a T or B cell is produced in an immune response, it reproduces into effector cells which fight the disease and memory cells which hang around until a repeated exposure and then are ready to respond. This means that the first exposure response is weaker and slower but a second response is fast and large.

Affinity maturation

With repeated exposures to a pathogen the immune system becomes more fine tuned. One way is that in the lymph nodes and spleen, the immune system selects for antibodies that have a higher affinity (stronger bonding) for that specific pathogen and those improved antibodies are then ready for the next infection.

Class switching

B cells produce multiple types of antibodies each of which is best for a certain type of pathogen (virus, parasite, bacteria). Class switching refers to B cells producing only the class of response needed for the specific pathogen and this is able to happen due to intercellular communication.

Acquired response terms

-Clonal selection

-Immunological memory

-Affinity maturation

-Class switching

Cell communication

1. Cell to cell contact

2. cytokines (chemical messengers)

1. allows for the correct immune response to be created based on pathogen type

2. allows for fine tuning of immune system with repeated exposure (class switching and affinity maturation)

5 vaccine methods

1. lived killed virus (flu shot)

2. live attenuated (weak) (nasal flu shot)

3. mRNA (tells body to make a pathogen protein) (Moderna and Pfizer)

4. clone a virus to make a harmless one

5. inject a pathogen protein

Good vaccine characteristics

-Safety: tested, side effects, vaccinated compared to unvaccinated, compare risks to risk of disease

-cost effective

-stable for storage

-ease of administration

-efficacy: reduction in rate of disease in vaccinated members in a controlled clinical trial

-effectiveness: reduction in rate of disease in the general population following approval

Passive vaccines

Administration of exogenous antibodies into a person to fight a disease. Created through immunized animals, serums from a previously infected person, and monoclonal antibodies through recombinant DNA methods. They are given usually when a person is already sick and allows for rapid treatment since traditional vaccines require time for a slow immune response. They are used for venom, malaria, ebola, covid (monoclonal), tetanus, rabies, hepatitis.

George Washington

required all soldiers be vaccinated against small pox in revolutionary war

Edward Jenner

-discovered that milk maids exposed to cow pox didn’t get small pox

-created vaccine from cow pus that immunized people to small pox

-first vaccine

US supreme court

Jacobson vs Massachusetts (1905) ruled in favor of a vaccine mandate

Other vaccine things

-important tool

-used to be high confidence

-used to control (measles, polio) or eliminate (small pox) many diseases

-hep vaccines required for first responders

-vaccines required to attend school

-risks of vaccines much less than risks of disease