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Ecology > Chapter 10: Populations Dynamics > Flashcards

Chapter 10: Populations Dynamics Flashcards

1
Q

Populations show different patterns of _______ over time

A

population growth

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2
Q

Population Dynamics

A

refers to the ways in which population sizes change over time

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3
Q

Exponential Growth

A

When rate of growth increases or decreases in proportion to the current number of individuals

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4
Q

How long can populations increase exponentially?

A

when conditions are favorable, a population can increase exponentially for a limited time, but it can’t continue indefinitely

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5
Q

What can lead to exponential growth?

A

dispersal

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6
Q

How does exponential growth work via dispersal?

A

new regions are colonized by long-distance events. Local populations then increase and expand by short-distance dispersal events

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7
Q

Logistic Growth

A

some populations reach a relatively stable population size, or equilibrium, that changes little over time
-numbers of individuals increase rapidly at first, then stabilize as the population reaches carrying capacity

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8
Q

Carrying capacity

A

max population size that can supported by the environment. Population size fluctuates around this number

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9
Q

Population Fluctuations

A

in some populations, numbers increase or decrease erratically from an overall mean
-also many occur as deviations from a population growth pattern (such as exponential or logistic)

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10
Q

Population Outbreak

A

number of individuals in a population explodes at certain times

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11
Q

What organism does population outbreak occur most often in?

A

insects. Mountain Pine Beetles altered ecosystems by killing millions of trees in BC

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12
Q

Factors that can cause population fluctuations?

A

nutrient supplies, temperature, and predator abundance

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13
Q

What is an important factor of disease outbreaks?

A

population fluctuations

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14
Q

Why does population fluctuations affect disease outbreaks?

A

high densities of species can increase contact. Harboring the spread of disease

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15
Q

Population Cycles

A

alternating periods of high and low abundance occur at regular intervals

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16
Q

Causes of Population Cycles

A

-internal factors (hormonal, behavioral changes in response to crowding)
-External factors (weather, food supplies, predators)
-The factors may vary with location and species

17
Q

Delayed Density Dependance

A

may be a factor in population cycles

18
Q

When does delayed density dependance occur?

A

when the number of individuals born in a given time period is influenced by population density or other conditions that were present several time periods ago

19
Q

What can stop population cycles?

A

key changes in environmental factors

20
Q

Fluctuations in population size can increase

A

risk of extinction

21
Q

Why does fluctuation in population size increase risk of extinction?

A

-a population that fluctuates grows slower than one that does not vary
-when variable environmental conditions result in large fluctuations in growth rate, the risk of extinction increases
-small populations are at greatest risk

22
Q

Effective Population Size

A

number of individuals that can contribute offspring to the next generation

23
Q

Extinction Vortex

A

small population sizes leads to further declines in population size, eventually resulting in extinction

24
Q

Factors that place small populations at risk of extinction

A

genetic drift and inbreeding depression

25
Q

Inbreeding

A

mating between related individuals that increases the frequency of homozygotes, including harmful alleles

26
Q

Genetic drift

A

chance events influence which alleles are passed on to the next generation. alleles can be lost or become fixed

27
Q

Demographic Stochasticity

A

chance events affect survival and reproduction of individuals
-more likely in small populations

28
Q

Allee Effects

A

growth rate decreases as population decreases
-at low densities, individuals have difficulty finding mates
-cause the population growth rates to drop, which causes population size to decrease even further in a downward spiral towards extinction

29
Q

Environmental Stochasticity

A

erratic or unpredictable changes in the environment

30
Q

Natural Catastrophes

A

(floods, fires, etc.) can eliminate or greatly reduce even large populations and play a role in extinctions

31
Q

Bottom-Up Control

A

increased nutrient inputs caused eutrophication and increased phytoplankton biomass, decreased oxygen, fish die-off, etc.

32
Q

Top-Down Control

A

top predators control the abundance of populations

Ecology (12 decks)

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