Ch. 53 Flashcards by emma lezcano

Population ecology

abundance, dispersion, and age structure of populations

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Example of population ecology

number of loggerhead turtle hatchlings that survive their first journey to the ocean

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Population

group of individuals of a single species living in the same general area

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How are populations described?

boundaries and size

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Population size

number of individuals

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Density

number of individuals per unit area or volume

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Dispersion

the pattern of spacing among individuals within the boundaries of the population

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Sampling techniques

are used to estimate densities and total population sizes

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Population size can be estimated how?

extrapolation from small samples
an index of population size
mark recapture method

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Mark recapture method

capture a small number of individuals, put a harmless mark on them, and release them back into the population

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Population size is estimated by?

N = sn/x

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Immigration

influx of new individuals from other areas

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Emigration

movement of individuals out of a population

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How does a population grow?

births and immigration

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How can a population decrease?

deaths and emigration

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What is the most common pattern of dispersion?

clumped; individuals aggregate in patches

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What are clumped dispersions influenced by?

resource availability
mating behavior
group defense

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Uniform dispersion

individuals are evenly distributed

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What influences uniform dispersion?

social interactions; territoriality

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Territoriality

the defense of a bounded space against other individuals

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Random dispersion

position of each individual is independent of other individuals

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When do random dispersions occur?

absence of strong attractions or repulsions among individuals

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Demography

the study of these vital statistics of a population and how they change over time

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Life table

age specific summary of the survival and reproductive rates within a population

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Cohort

a group of individuals of the same age

Who is ignored when studying sexually reproducing species?

Males

What does the life table of female Belding's ground squirrels reveal about their population?

provides data about the proportions of females alive at each age and the number of female offspring produced per female

What are the three classifications of survivorship curve

Type I Type II Type III

Survivorship curve

a graphic way of representing the data in a life table

Type I survivorship curve

low death rates during early and middle life and an increase in death rates among older age groups

Type II survivorship curve

a constant death rate over the organism's life span

Type III

high death rates for the young and a lower death rate for survivors

Change in N / Change in T = B - D

population growth rate N - change in population size t - time B - number of births D - number of deaths

Change in N / Change in T = R

R - difference between number of births and the number of deaths

Exponential population growth

population increase under idealized conditions

What kind of curve results from exponential population growth

J-shaped

Example situation when J shaped curve was used

elephant population in Kruger National Park, South Africa, grew exponentially after hunting was banned

Carrying capacity (K)

the maximum population size the environment can support (varies with the abundance of limiting resources)

Logistic population growth model

per capita rate of population growth approaches zero as the population size nears carrying capacity

Why is a logistic model useful?

it can be used as a starting point for thinking about how populations grow

What can conservation biologists use the logistic growth model for?

population recovery estimate sustainable harvest rates estimate size below which populations may become extinct

Three components of organism's life history

1. age at first reproduction (maturity) 2. how often the organism reproduces 3. how many offspring are produced per reproductive episode (clutch size)

Semelparity

big-bang reproduction; reproduce one and die

Iteroparity

repeated reproduction; produce offspring repeatedly

Organisms have finite resources which may lead to what?

tradeoffs between survival and reproduction

Example of tradeoff

european kestrels; tradeoff between survival and paternal care

What influences trade offs between the number and size of offspring

selective pressures

Some plants produce a large number of small seeds which does what?

Ensures that at least some of them will grow and eventually reproduce

Other types of plants produce a moderate number of large seeds why?

provide a large store of energy that will help seedlings become established

r species

small size organism many offspring short life expectancy each individuals reproduces once type III survivorship pattern

K species

large size organism few offspring produced long life expectancy individuals can reproduce more than once type I or type II survivorship

r selected species examples?

dandelions, insects

K selected species examples

elephants, humans

Density independent populations

birth rate and death rate do not change with population density

Density dependent populations

birth rates fall and death increase with rising population density

What factors can regulate population size?

density dependent factors

What is an example of negative feedback that regulates population growth?

Density dependent birth and death rates

Competition for resources, disease, predation, territoriality, toxic wastes, and intrinsic factors are examples of?

factors that affect density dependent birth and death rates

When increasing population density?

intensifies competition for resources and results in a lower birth rate

Pathogens spread more rapidly in what populations?

dense populations

What happens as a result of prey population building up?

predators may feed preferentially on that species

Territoriality can limit population when?

individuals compete for limited space

Intrinsic factors

physiological factors can regulate population size

What contributes to density dependent regulation of population size?

accumulation of toxic wastes

Example of boom and bust cycles

lynx populations follow the 10 year boom and bust cycle of hare populations

Emigration increases?

when a population becomes crowded and resource competition increases

Metapopulations

groups of populations linked by immigration and emigration

Where do local populations in a metapopulation occupy space?

patches of suitable habitat surrounded by unsuitable habitat

The global population is now more than?

7.2 billion people

The rate of growth began to slow down when?

1960s

Age structure

relative number of individuals of each age in a population one important factor affecting population growth is the country's

Population in 2050?

8.1 -10.6 billion people