population ecology - biology

what are the key concepts of population ecology

understanding populations, demography, how populations grow, human population growth

what is population?

group of interbreeding individuals occupying the same habitat at the same time

what are examples of population

water lilies in a particular lake, humans in New York City

what is the study of factors affecting population size and how they change over space and time?

population ecology

what is density?

number of organisms in a given unit area or volume

what knowledge comes with density?

knowledge about population growth and density help us make species management decisions

what are species?

entities capable of interbreeding

do all species exchanges genes in the same way? which one is different?

no not all species do, ex: bacteria

What are gray zones in ecological and evolutionary contexts?

Areas where it's difficult to distinguish between ecological and evolutionary processes or between native and non-native species.

Why are gray zones described as dynamic?

Because ecosystems and species are constantly changing through ecological interactions and evolutionary adaptation.

How does evolutionary theory explain gray zones?

Evolutionary theory views species as evolving entities, meaning species are defined more by their evolutionary history than by static ecological roles.

Why are species considered more evolutionary than ecological entities?

Because species evolve over time — their identities are shaped by genetic and evolutionary changes rather than fixed ecological functions.

what are repeating niches? what does this lead to?

similar abiotic conditions may favour convergent evolution. this leads to ecological equivalents

what is an example of a repeating niche?

Hummingbird (America)

Sunbird (Africa)

Giant armadillo (North America)

Giant Anteater (South America)

Spiny Anteater (Australia)

Giant pangolin (Africa)

area must be small and organisms relatively large

what does simple visual count consist of?

what is estimation of abundance over large area by extrapolating from a smaller sample apart of?

quantifying population denisty

what does estimation of abundance over large area by extrapolating from a smaller sample consist of?

Quadrates and line transects - sessile species and traps more mobile species

what is the mark-recapture technique?

it is a method for estimating population size

What do animals have on them so they are recognizable when captured again?

tags or other systems

What equation is used following resampling?

((#of individuals marked in first catch) / (total pop. size (N))) = ((# of marked recaptures in second catch) / (total # of second catch))

what does the total population size equal?

((# of marked individuals in first catch) x (total # of second catch) / (# of marked recaptures in second catch))

What are the limitations of the Mark recapture technique?

• Animals may learn to avoid traps

• capture rate will be low results, in overestimate of population size

• Some animals can become "trap-naps", especially if baited with food

• results in underestimate of population size

What are some other methods instead of the mark recapture technique?

1. Antennal tracking of fitted radio collar

2. On man aircraft systems to document abundance

3. Obtaining pelt records from trading stations

4. Examinations of cash per unit effort

What are examples of quantifying population density?

• Satellite imaging

• EDNA

• acoustic monitoring

• citizen science

what are the 3 types of dispersion patterns

1. clumped

2. uniform

3. random

what is clumped dispersion patterns?

this is most common, resources tend to be clustered in nature, social behaviour may promote this pattern

what causes uniform dispersion pattern? what is the result?

competition may cause this pattern, may also result from social interaction

what is random dispersion dispersion patterns

it is is rarest dispersion pattern, resources are rarely randomly spaced, and may occur where resources are common and abundant

What are some considerations that dictate distribution and ranges?

1. tolerances

2. specialization

3. life history needs

4. predators

5. competition

what are: climate shifts, chance, and humans examples of?

history and future effects on distributions

what are some characteristics about migration?

1. life history facts

2. affects distribution (dispersion)

3. ecological impacts

what are 3 parts of Irruptions with examples

1. mass dispersals, i.e Spruce Budworm

2. Synchronous emergencies - predator saturation (ex: acorns, cicades)

3. Ecological release, i.e., fire

when does homogenize occur?

if dispersers breed with residents, homogenize's occur.

What happens when populations are isolated (e.g., islands) with small population sizes?

They experience rapid genetic drift and natural selection.

What evolutionary outcome can occur when isolated populations undergo drift and selection?

Speciation, following the allopatric model.

How does dispersal relate to gene flow?

Dispersal increases gene flow, which prevents divergence and speciation.

What is genetic drift and when is it most significant?

Genetic drift is a random change in allele frequencies within a population. It's most significant in small or isolated populations, where chance events can greatly affect genetic variation.

what is the founder affect

a few individuals form a population, start a new population with a different allele frequency from the original population

what are Metapopulations?

A network of distinct populations linked by gene flow

what type of resource is metapopulations

usually patchy

what is habitat fragmentation

chopping landscape into little blocks

what are 2 forms of reproductive strategies

1. semelparity

2. Iteroparity

what is semelparity?

Produce all offspring in single reproductive event

what is Iteroparity?

Repeated reproduction at intervals throughout the life cycle

what animals do semelparity occur in?

Salmon, bamboo and agave, as well as many insects and other invertebrates

what is common in most vertebrates, perennial plants, and trees?

Iteroparity

what is seasonal Iteroparity?

distinct breeding seasons

what is continuous Iteroparity?

Reproduce repeatedly at any time of the year

what is favoured in unpredictable environments?

Iteroparity

what are 3 examples of different reproductive strategies?

1. Agave lifetime

2. Blue tit lifetime

3. Chimpanzee lifetime

do reproductive strategies have a strong effect on subsequent age classes of a population?

yes

what do semelparous organisms produce? what is their name?

groups of same aged young, called cohorts

true or false: Iterparous organisms have young of different ages?

true

how can age classes be characterized?

by specific categories

How are mammals, insects and plants characterized?

years, stages, and size, respectively

what population has many young?

an increasing population

what population has few young?

decreasing population

what does an imbalance in decreasing population in age classes have an impact on?

An imbalance in age classes can have a profound influence on a population's future

is it practical to follow a cohort from brith to death, for long-lived animals?

no, it is impractical

what are life tables?

Data on the number of individuals alive in a particular age class

which gender is usually not included?

male

what is an example of life tables?

the north American beaver

• 1964-1971, Canadian trappers provided mandibles

• teeth extracted for age classification

what is a survivorship curve

Plot of numbers of surviving individuals at each age

what is generally used to make it easier to examine a wide range of population sizes?

generally use log

which animals shows a fairly uniform rate of decline?

beavers

What are the three types of survivorship curves?

Three types

What is type one survivorship curve pattern?

Rate of loss of juveniles, low and most individuals loss later in life

Which animals are an example of type one

Many large mammal, such as humans

What is type two survivorship curve pattern?

Fairly uniform death rate

What animals is an example of type two survivorship curve pattern

Beaver, birds, reptiles, and some annual plants

What is type three survivorship curve pattern?

Rate of law for juveniles high and then loss for low survivors

What is an example of type three ship curve pattern?

Many fishes, marine invertebrate, insects, and plants

How many models are there for population growth?

Two

What is population growth based on?

Based on whether resources are limiting

What is exponential growth?

Resource is not limiting prodigious growth

What is logistic growth?

resources are limiting, limits the amount of growth

When is population increase rapid?

One reproductive rate "r" is greater than zero

What type of curve does an exponential growth pattern have?

J shaped curve

What does population growth depend on for the population increase to be greater as time passes

The value of "N" as well as the value of "R"

Does exponential growth occur under some conditions?

Yes

---------- of a population to a habitat, growth of introduced exotic species, and global human population

reintroduction

What does intrinsic rate of increase equal?

Rmax = r at maximum

What is a logistic growth curve?

Population growth, slows as it approaches K

What is K?

Carrying capacity

Does the logistic model fit , fit all populations?

No, only some

What type of population does the logistic model fit best?

Laboratory cultures

What causes changes in carrying capacity?

Variations in nature, change resource levels, changing carrying capacity

What can cause temporary overshoots of the logistic model fit?

Time lags

What are density dependent factors?

Mortality factor that varies population density

What is predation?

Predators kill you pray when the prey population is low more pray when the population is higher

What is competition?

Increase competition for scarce resources, reduce reduces offspring, production, and survival

What is parasitism?

Parasites past the new house more easily as population density increases

How is density dependence detected?

Detected by plotting mortality against population density and finding positive slope

Is not affected by changes in population size or density

Density independent factors

What are examples of density independent factors?

weather, drought, flood, fire

What is inverse density dependent factor?

Density Decreases with increasing population size

What is an example of inverse density dependent factors?

A line which feeds on the same number of wheel, the beast per week will act in an inverse manner with an increasing population by taking a smaller portion of the population

What are r-selected species?

High rate of per capita population, but poor competitive ability

How fast do r- selected species grow and when do they reach reproductive age?

Grow quickly and reach reproductive age early

What are 2 examples of r-selected species?

Weeds and insects