Chapter 13 Part 1 Flashcards

1
Q

how do populations fluctuate?

A

naturally, over time

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2
Q

Wild population numbers undergo significant

amounts of variation from year to year

A

variations
that occur in invertebrates as well as vertebrates ….
in plants as well as bacteria, fungi and even viruses

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3
Q

wild population numbers are dependent on

A

changing environmental conditions over time (weather/climatic conditions) - these factors can influence such things and competitive interactions, predation rates, herbivory, parasitism

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4
Q

variation in the density of a population depends on:

A
  1. the amoung of environmental fluctuation (both density dependent and density independent factors)
  2. the inherent stability in the population
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5
Q

all populations experience fluctuations due to factors such as

A

availability of resources, predation, competition, disease, parasites, and climate

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6
Q

Fluctuations include

A

random and cyclic changes through time

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7
Q

Some populations tend to remain

A

relatively stable over long periods

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8
Q

In contrast, some populations exhibit

A

much wider fluctuations

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9
Q

Small organisms (e.g., algae) tend to reproduce much faster than larger organisms (e.g., red deer), so their populations often respond

A

faster to favorable and unfavorable conditions (high surface areas)

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10
Q

Larger organisms have a lower surface-area-to-volume ratio, which allows them to

A

maintain homeostasis in the face of unfavorable environmental changes

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11
Q

some of the most pronounced population fluctuations in nature are the predictable cycles of certain

A

mammal and bird species at high latitudes

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12
Q

When an age group contains a high or low number of individuals, the population likely experienced

A

high birth or death rates in the past

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13
Q

Long-term fluctuations in age structure can be determined for a forest by

A

examining tree rings

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14
Q

Populations in nature rarely follow a smooth approach to their

A

carrying capacity

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15
Q

overshoot

A

when a population grows beyond its carrying capacity

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16
Q

when does overshoot occur

A

often when the carrying capacity of a habitat decreases from one year to the next

17
Q

die-off

A

a substantial decline in density that typically goes well below the carrying capacity

18
Q

when do die-offs often occur

A

when a population overshoots its carrying capacity

19
Q

Populations With High Growth Rates Track
Environmental Fluctuations More Closely
Than

A

Those With Low Growth Rates

20
Q

Environmental changes continually increase and
decrease the carrying capacity of the environment
for each population. How a population responds to such
changes through density-dependent effects, depends on …

A

the intrinsic capacity of the population to increase
in size … that is, its r value (which ultimately is
influenced by the extent to which the species is “r”
or “k” selected)..

21
Q

The faster the potential rate of growth or decline
of the population – i.e., the higher the fecundity and
the shorter the life span of individuals

A

the greater is
its capacity to track change in its environment (e.g.
r-selected species).

22
Q

Populations with r > 1 tend to

A

track environmental

changes

23
Q

populations with r < 1 may

be

A

unresponsive to short-term environmental change

24
Q

A population

with a higher growth rate (r = 0.5) tracks

A

a population with

a lower growth rate (r = 0.1)

25
Population Cycles May Result From
Intrinsic | Demographic Processes
26
Environmental changes generally tend to be
irregular rather than predictable
27
biological responses to environmental changes are also frequently
random and unpredictable
28
The sizes of many populations do, however, | change with
periodic frequency
29
a number of small mammal cycles have become part of the
lore of population ecology
30
Charles Elton, in 1924, showed that the lynx, and its | main prey, the snowshoe hare, display
large, regular fluctuations in population size - with each cycle lasting about 10 years
31
Fluctuations in population numbers may result in
a time delay
32
Fluctuations in population numbers may result in a | time delay in the response of
births and deaths to changes in the environment - just as the momentum imparted to a pendulum
33
The momentum provided to a population with high birth rates at low densities or high death rates at high densities …. results in
the population “swinging” past its equilibrium point when demographic responses are time-delayed
34
Times delays are inherent in models based on
discrete generations
35
Population cycles
regular oscillation of a population over a longer period of time
36
Some populations can exhibit
highly regular fluctuations in size
37
Cyclic populations can occur among
related species and across large geographic areas (e.g., the synchronous cycles of the capercaillie, black, and hazel grouses in Finland).