Independent study unit

What is population ecology

• the study of populations, particularly the size, density, distribution, and changes over time

WHat are uses of population ecology

• Gather’s data to predict growth trends in populations

• help determine the health of different species/ ecosystems in which the species live in

• research in ecology is often linked to genetics, physiology, anatomy, behaviour, evolution, etc…

• info from population ecology allows scientists to manage the size of populations

  • ecologists must determine how environments influence organisms and how organisms change the environments in which they live

What 3 factors describe the distribution of a population

• its geographic range

• population size and density

• the way that individuals are dispersed through the area

What is geographic range

• the total area that is occupied by a population

• varies between species

what is a habitat and how is it characterised

• a habitat is a specific environment in which an organism lives in

• characterized by its biotic (living) and abiotic (non living) features

  • biotic : plants, animals

  • abiotic: soil, sunlight, temp, water

What is population size and density

• population size (Nt) : the number of individuals that make up a population at a specified time

• population density (D): the number of individuals per unit area or per unit volume (of their habitat)

What do species with a larger body size tell u about their population density compares to species with a smaller body size

• species with a larger body size generally how a lower population density than species with a small body size

What are the 2 types of population density

• crude density: population density measured in terms of individuals of the same species within the total area of their entire habitat

• ecological density: population density measured in terms of individuals of the same species per unit area or volume

how is population density calculated

• by dividing the total numbers of individuals in the population (N) by the space occupied by the population (S)

• D = N/S

Researchers identified 860 mature sugar maple trees (Acer saccharum) growing in a 4 ha (hectare) forested area of central Ontario.

a) What is the density of the trees?

b) in the same study, the researchers estimated that there were 75000 maple seedlings in a 0.5 ha in a plot. What is the density of the seedlings

What are the 3 methods of estimated population sizes

• quadrat method

• mark-recapture method

• technological tracking

Define quadrat and describe the quadrat method for estimating population sizes

• quadrat : a sampling frame that is used for estimating population size

  • frame can be real or virtual (Ex: square made of wood, plastic, etc…)

A biologist wants to estimate the population size and density of snails on a beach. The beach measures 100m by 1.0m quadrats on the beach. Estimate the population size and density if the biologist counts 55, 13, 42, and 35 snails in the 4 quadrats

Describe the mark-recapture method

• a sampling technique for estimating population size and density by comparing the proportion of marked and unmarked animals that are captured in a given area (sometimes called the capture-recapture method)

• Accuracy of this method depends on 5 assumptions:

  • chances that each individual in the population to be caught are equal and constant for both the initial capture and recpature

  • proportion of marked to unmarked animals remains the same between captures

  • enough time is allowed between the initial capture and the subsequent recapture for all marked individuals to disperse randomly

  • the captured animals are not affected by their marks

  • marked animals do not lose their marks

• Based on these assumptions, estimated pop size is calculated using:

  • total number marked (M) / total pop (N) = number of recaptures (m) / size of the second sample (n)

  • M/N = m/n

What are the 5 assumptions when using the mark-recapture method to estimate population size

• Accuracy of this method depends on 5 assumptions:

  • chances that each individual in the population to be caught are equal and constant for both the initial capture and recpature

  • proportion of marked to unmarked animals remains the same between captures

  • enough time is allowed between the initial capture and the subsequent recapture for all marked individuals to disperse randomly

  • the captured animals are not affected by their marks

  • marked animals do not lose their marks

what is the formula used for mark-recapture method

• Based on these assumptions, estimated pop size is calculated using:

  • total number marked (M) / total pop (N) = number of recaptures (m) / size of the second sample (n)

  • M/N = m/n

Biologists were studying a saw-whet owl population of unknown size. They captured, banded, and released 30 individuals. They waited until they assumed that the released individuals had moved randomly through the population. Then they captured a second sample of 80 individuals and found that 12 individuals were marked. Use these values to estimate the population size

Describe technological tracking

• technological tracking is essentially done through special transmitters using GPS technology and sateillites

• tracking can also be done with DNA sampling

  • by collecting and testing their droppings and other biological materials

• tracking animals provides useful information about their behaviour

• biologists have been able to learn a great deal about the range, distribution, and population density of various species with these techniques

Why are scientists concerned about studying wild populations

• marking and tracking can be excellent techniques for monitoring and sampling a population

• but there is also an ethical debate about their potential impact on the animals involved

  • concerns that the handling of animals during data collection (for pop size/density) may alter their behaviour after their release or reduce their reproductive ability

  • concerns about trapping methods that may be harmful

What is the canadian council on animal care (CCAC) and what do they do

• the CCAC are developing a set of guidelines for ethical wildlife research by encouraging researchers to:

  • reduce their use of animals in studies as much as possible

  • support and develop techniques minimize pain and distress

  • replace trapping with computer estimations where possible

what is distribution

Distribution: the spatial distribution of individuals within a geographic range

a)

• clumped dispersion : individuals are grouped more closely to each other than if they were randomly dispersed (groups of clumps)

• random dispersion : individuals are distributed independently of each other

• uniform distribution: individuals are more widely separated from each other than if they were randomly dispersed

b) No, dispersion patterns do not always match what you might expect, because they depend on more than just where resources are found. Competition, territorial behavior, social grouping, and environmental patchiness can all change the pattern.

For example, even if a habitat seems evenly suitable, animals may still be clumped because they live in groups, or uniformly spaced because they defend territories.

• more in notes

Define demography

• the study of the growth rate, age structure, and other characteristics of populations

define emmigration

• movement of individuals out of a population

define immigration

• movement of individuals into a population

define natality (birth)

• birth rate in a population

define mortality (death)

• death rate in a population

WHat is a life table

• a life table summaries the demographic characteristic of a population

How do demographers collect life table data

• demographers usually mark a group of individuals born around the same time (cohort) and then monitor the survival of these individuals until all of them die

WHat are the 2 ways mortality rate can be viewed

• age-specific mortality: proportion of individuals that were alive at the start of an age interval but died during the age interval

• age-specific survivorship: the proportion of individuals that were alive at the start of an age interval and survived until the start of the next age interval

Whats the formula for age-specific mortality rate

Formaula for age-speceifc survivorship?

When u add age-specific survivorship and age-specific mortality together what do u get

• age-specific survivorship + age-specific mortality = 1

What are survivorship curves

• a graphic display of the rate of survival if individuals over the lifespan of a species

What are the 3 types of survivorship curves and describe them

• Type I curves

  • relatively flat at the start, reflecting a low death rate in early and middle years

  • drop steeply as the death rate increases in the older age groups

• Type II curves

  • reflect a relatively constant rate of mortality in all age groups

  • provides a steadily declining survivorship

• Type III curves

  • drop rapidly at the start, reflecting a high death rate early in life

  • flattens as the death rate declines for the few individuals that survive the critical stage

For each type of survivorship curve, what types of organism are usual for each curve

Type I:

• These curves are typical for large animals that produce few young and provide their young with extended care, reducing mortality

Type II:

• organisms that have type II curves generally have a relatively short gestation (pregnancy) period

• often feed on type III organisms but are preyed on by type I organisms

Type III:

• this type of curve is common of species that produce a large number of offsprings

Define fecundity

• the potential reproductive capacity of an individual or population

WHat is fecundity dependent on

• environmental conditions

  • in years where food is high and climate is optimal, species have higher fecundity

  • years where food is little and little precipitation, fecundity is low

• generation time

  • (time needed to complete one generation between the birth of an organism to the birth of its offspring)

• sex ratio

  • (relative proportion of males and females in a population)

  • number of females has a bigger impact cause they are the ones producing and one male can mate with several females hence the reason why number of females have a bigger impact

Define generation time

• the time needed to complete one generation between the birth of an organism and the birth of the offspring

define sex ratio

• the relative proportion of males and females in a population

Describe the relationship between fecundity and parental care

• an animal that has many offspring (high fecundity) normally does Little to care for them

• in contrast, animals that have just one or 2 offspring per year tend to be very protective and take good care of their offspring

What is the change in population size formula

• pop change = (births + immigration) - (deaths + emigration)

• natality

  • Births increase population size because new individuals are added.

• Mortality

  • Deaths decrease population size because individuals are removed.

• Immigration

  • Immigration increases population size when individuals move into the population.

• emigration

  • Emigration decreases population size when individuals move out of the population.

a) = 1

b) 0.703

• by summarizing the demographic characteristics of a population

a) 7-9

b) 22-24

c) 0.171

d) type I

• environmental conditions

  • years where food is high and climate is optimal, fecundity is high

  • years where food is little and precipitation is little, fecundity is little

• generational time

  • time needed to complete one generation between the birth of an organism to the birth of its offspring

• sex ratio

  • relative proportion of males and females in a population

  • number of females have a bigger impact cause they are the ones reproducing while one male can mate with several females

• 360

Define population dynamics

• the change in a population over time

• if positive → population is growing

• if negative → population is decreasing

• if 0 → no change in pop size

What is the exponential model of population growth

• a pattern of population growth in which organisms reproduce continuously at a constant rate

• ex:bacteria production

What is the per Capita growth rate (r)

• the difference between the per Capita birth rate and the per capita death rate of a population

What is the per Capita birth rate (b)

• the number of births in a population during the specified time period divided by the population size

What is the per Capita death rate (d)

• the number of deaths divided by the population size

In a population of 2000 field mice, if 1000 mice are born and 200 mice die during one month, the per capita birth rate of the mice would be? and what about per Capita death rate?

What is zero population growth

• a situation where the death rate and the birth rate are in equilibrium

  • population size doesn’t change

  • births and deaths still occur, but they are at equal amounts

WHat happens to the per Capita death rate and per Capita birth rate when there are limited ressources

• per Capita birth rate decrease

• per Capita death rate increase

• ZPG

What is the carrying capacity (k)

• the max number of individuals in a population that the environmental resources can support

• different for every poipulation

• varies from one habitat to another

What is doubling time?

• the doubling time of a population is the amount of time that is required for the population to double in size

• td = 0.69/r

• r = per Capita growth rate

a population of single-celled marine algae grows exponentially. A sample of single-celled marine algae provided an estimate of 125000 cells on the initial sampling date. The intrinsic growth rate (r) is 0.16 per day. Calculate the following:

a) the initial instantaneous growth rate of the population

b) the time it will take for the population to double in size

the size of the population after five doubling periods

d) exponential increase followed by a sharp decline caused by antibiotics

What are the limitations of the exponential growth model

• environmental limits

  • limited resources prevent continuous growth in populations

• resource competition

  • as populations grow and outnumber resources, individuals compete, leading to increased death rates and decreased birth rates

• reproductive patterns

  • many populations do not reproduce continuously as they have specific breeding periods

• geometric growth patterns

  • reproduction at fixed intervals, following by population decline until next breeding period

  • growth rate determined by comparing year-to-year population size

what is the carrying capacity (k)

• the max number of individuals in a population that the environmental resources can support

What is the logistic model of population growth

• describes growth that levels off as the size of a population reaches the carrying capacity

• if a population is very small ( N much less is K)

  • plenty resources are available

  • r approaches rmax

  • value of (K - N) / K is close to 1

• if a population is large (N close to K)

  • few resources available

  • r is very low

  • (K - N) / K is small

• is population is K (N =K)

  • (K - N) / N becomes 0

  • situation defined as zero population growth

  • r becomes 0

• IF size of a population (N) exceeds carrying capacity (N bigger than K)

  • population decreases

  • when graphed, this type of population growth creates an S-shaped curve,or sigmoid curve (logistic)

describe the conditions of logistic model of growth

• if a population is very small ( N much less is K)

  • plenty resources are available

  • r approaches rmax

  • value of (K - N) / K is close to 1

• if a population is large (N close to K)

  • few resources available

  • r is very low

  • (K - N) / K is small

• is population is K (N =K)

  • (K - N) / N becomes 0

  • situation defined as zero population growth

  • r becomes 0

• IF size of a population (N) exceeds carrying capacity (N bigger than K)

  • population decreases

  • when graphed, this type of population growth creates an S-shaped curve,or sigmoid curve (logistic)

What is the sigmoid curve (logistic)

• an s-shaped curve, typical of population growth that starts slow, accelerates or grows rapidly, and then levels out over time

analyze these sigmoid curve (logistic)

• population grows slow when population size is small because few individuals are reproducing

• population grows slow when population is large because as population approaches k,the per Capita population rate is low

• populations grow quickly at intermediate population sizes, where a large number of individuals are breeding and per Capita population growth rate (r ) is still fairly high

A population of spotted butterflies exhibits logistic growth. The carrying capacity of the population is 500 butterflies, and the maximum growth rate (rmax) is 0.1

a) determine the population growth rates based on a population size of 50, 100,200, 350, 480, 500 and 525 butterflies

b) describe the relationship between population size and growth rate

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What are the assumptions made when it comes to limitations of the logistic growth model

• all individuals reproduce, die, and use resources at the same rate

• carrying capacity (k) remains constant, with no environmental variations

• no migration (immigration or emigration) occurs

What is the difference between open populations and closed populations

• open population →natality, mortality, immigration, and emigration all effect growth rate

• closed population →only natality and mortality affect growth rate

  • immigration and emigration already occur

• exponential growth is represented by a J-shaped curve because the population increases rapidly without constraints,

• while logistic growth is represented by an S-shaped curve because the population’s growth slows down and stabilizes as it approaches the carrying capacity

• carrying capacity is the max number of individuals in a population that the environmental resources can support

• Carrying capacity (K) is an important statistic when describing an environment because it represents the maximum population size of a species that a specific environment can sustainably support over time

define limiting factor

• a factor that limits the growth of a population

  • limiting factors can be biotic or abiotic

  • can cause populations to increase or decrease

What are the 2 types of limiting factors

• density-dependent factors

  • a factor that is influenced by population density, having a greater impact as the population density increases

• density-independent factors

  • a factor that influences population regulation, regardless of population density

    • factors not related to density

What are examples of density-dependent factors?

• competition

  • an interaction in which both competing populations lose access to some resources

  • two types: intraspecific competition and interspecific competition

  • competition is only apparent if population density is high or low

• predation

  • when one organism kills and eats another organisms (interaction between predator and prey)

  • more competitive when population density of predators are high

  • by consuming the prey, predators increase their own population while decreasing the population density of the prey

• disease

  • increases with the density of the population

  • high population density makes the spread of disease easier, and disease can have catastrophic effects on a population, as well as all the populations that interact with it in an ecosystem

• crowding

  • only occurs in high-density population with limited space

  • crowding affects the growth, size, and survival of the individuals in a population

  • individuals living in extremely dense populations are unable to harvest enough resources

  • when resources are more shared, less is in supply, and individuals have less energy for reproduction

  • also allows disease to spread more easily

What are the two types of competition

• intraspecific competition

  • ioccurs when members of the same species compete for ressources

• interspecific competition

  • occurs when members of different species compete for resources

what is the allee effect

• a density-dependent phenomenon that occurs when a population cannot survive or fails to reproduce enough to offset mortality once the population density is too low

  • not crowded enoiugh

  • occurs when population is too small

  • animal species that reach small sizes or low densities experience a decrease in their Capita rate of population growth

  • can lead to extinction

  • small populations are at greater risk for extinction due to the normal variations in natality and mortality, resources limitations,habitat availablitity, predation, competition, and catastrophic events

What is the minimum viable population size

• the least number of individuals that ensures the continued existence of a population for a determined period of time, regardless of environment change or disaster

  • likely to survive both predictable and unpredictable environmental variation

  • if a species drops below it's minimum viable pop size, chances of extinction increase dramatically

  • note: only a prediction

what are the density-independent factors

• natural disturbances

  • like fires, earthquakes, and storms can contribute directly or indirectly to density-independent mortality

• temperature fluctuations

  • also influence the growth and activity of organisms

• warmer climates

  • can have density-independent impacts on the level of atmosphere carbon dioxide

Describe two examples for temperature fluctuations as a density-independent factor

• mountain pine beetles:

  • burrows into pine trees, eating soft tissue beneath the bark

  • overwhelms and kills trees

  • has not been a problem until recently as beetle populations were kept in check by winter frosts and temps that routinely dropped low

  • recent winter shave not had low enough temps to limit the beetle population significantly

  • higher beetle survival rates and lack of resistance in trees lead to an increased beetle attacks

  • more dead trees means more release of carbon dioxide

  • increases the temp more leading to more beetles surviving

  • called a positive feedback loop

• human effects

  • massive forest fires have turned trees into carbon sources, released the carbon dioxide stores within trees

  • with the increase in temp, leads to reduced precipitation, drought, and storms

  • these issues present great challenges for future planning and species management

a) density-independent

• drought is a natural distater that affects population regardless of pop density

b) density-dependent

• predator population increases cause prey population increase

c) density-independent

• natural disaster

d) density-dependent

e) density-independent

f) density-independent

• limited genetic diversity within the population

• Predation: because of predetors that rely on the population density of deers as their prey to feed on them and increase their own population

• competition: may introduce more competition into an environment where an increased deer pop density leads to more competition for resources

define coevolution

• a process in which one species evolved in response to the evolution of another species

What are the types of coevolutionary relationships and know examples of each

• predation (+/-)

  • when an organism feeds on another organism

  • predators gain nutrients and energy while prey are killed or injured

  • ex: northern lynx (predator) and snowshoe hare (prey)

  • northern lynx gains nutrients and energy while snowshoe hare are killed and injured

• herbivory (+/-)

  • organism feeds on plants

  • herbivores gain nutrients and energy while plants are killed or injured

  • ex: white-tailed deer (herbivore) and foliage plant

• mutualism (+/+)

  • interaction/relationship where both partners benefit each other

  • ex: honey bee (pollinator) and flowering plants

  • honey bee feeds on flowering plants while plants are able to reproduce asexually because of the pollination

• Parasitism (+/-)

  • interaction where one species benefits and the other is harmed

  • parasite benefits from host while reducing the host’s in some way

  • ex: mistletoe, which attaches to a tree and takes water and nutrients from its host; usually stunts growth but can kill the tree with heavy infestation

• Competition (-/-)

  • both competing populations lose access to some resources

  • ex: trees in a forest competing for light

• commensalism (+/0)

  • an interaction where one species recieves benefits from the other organism without affecting them

  • ex: moss growing on a tree getting light and nutrients while the tree is unaffected

compare predation and herbivory

• carnivores use sensory systems to locate their animal prey and specialized behaviours and anatomical structures ro capture and consume it

• herbivores have comparable adaptations for locating and processing food plants

  • herbivorous mammals have specialized teeth to harvest and grind tough vegetation

• it is predicted that an animal’s diet is a compromise between the costs and benefits associated with different types of food

  • an important element in food choice is the abundance of prey

what are the different types of defense mechanisms

• camouflage

  • an organism mimics the pattern of its environment

• chemical defense

  • an organism is chemically unattractive, either by releasing noxious odours or by concentrating poisonous chemicals in its body

• behavioural defence

  • this defense can be passive (such as hiding,freezing or playing dead)

  • or active (such as fleeing, herding,mobbing,or using distraction displays)

• mimicry

  • two types

  • batesian mimicry: a palatable or harmless species (mimic) resembles an unpalatable or poisonous species (model)

  • mullerian mimicry: two or more unpalatable species that share common predators look the same

• spines and armour

  • various animals and plants have dard, thorny, or needle-like structures

Is predation an example of interspecific interaction or intraspecific

• interspecific

  • pop density of one species, predator increases, while pop density of the other species,prey, decreases)

  • when prey population increases, predator population decreases and vise versa

describe population cycles

• when prey population increases, predator population decreases and vise versa

• predation is an example of interspecific competition

• ex: population of lynx (primary eats snowshoe-hares) tended to rise and fall just a year or two after the changes in snowshoe-hare population

  • caused by complex interactions between the hare populatios

  • other factors affecting the cycling of population size: catastrophic natural events, changes in climate, and human interference I.e addition of non native species and habitat destruction)

  • these fluctuations make a sinusoidal graph