L. 25 - Groups & Populations Flashcards

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1
Q

L.O.

A
  • Be able to describe and understand exponential and logistic models of population growth
  • Define instantaneous growth rates in discrete and continuous exponential growth models
  • Become familiar with demographic rates and how they are measured
  • Understand what a stage/age structure model is
  • Understand what a spatially structured population is
  • Understand the principles and implementation of population viability analysis
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2
Q

Groups

A
  • Multiple organisms of some or different species in a common space
  • Ephemeral or consistant
  • Social, indirect or accidental
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3
Q

Populations

A

A number of organisms of same species in a defined geographical area
- Populations can move geographical locations or stay put

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4
Q

Properties of populations

A
  • number of individuals/ population size
  • Area they occupy
  • Age structure
  • Sex ratio
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5
Q

Populations are essential for

A

Ecology:
- Distribution and abundance of individuals and how it might change
- Densities

Evolution:
- Populations of organisms evolve, not individuals
- Gene flow

Conservation management:
- Invasive species
- Defining threat status
- Translocation and restorations

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6
Q

Population biology

A
  • Understand temporal dynamics of populations
  • Understand spatial distribution of a population (in some areas but not others)
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7
Q

Population growth

A
  • Change in numbers over time (positive or negative)
  • Rate (r) = change/ unit of time
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8
Q

Demographic rates:
Variables that drive changes in populations

A
  • Birth
  • death
  • emigration
  • immigration
  • Growth
  • age at maturity
  • sex ratio
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9
Q

Birth and death rates

A
  • balance of additions and losses determine growth rate
  • Inherent to all population growth models

When there is NO emi/ immigration, the population in ‘closed’

Nt = # of indiv. in pop. at time ‘t’

Nt + 1 = Nt + (births - deaths)

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10
Q

Exponential growth

A

Geometic:
- Populations grow faster as they grow bigger

Discrete:
- Population = periodically

Continuous:
- Reproduction = year-round

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11
Q

Resource limited growth

A
  • Pop. growth is often resource limited
  • Numbers cannot increase beyond the carrying capacity ‘k’
  • Log curve graph, plateau at point when ‘k’ is reached
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12
Q

Estimating birth rates

A
  • Count new-born individually

(monitor active bird nests)

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13
Q

Estimating death rates

A
  • Difficult

Common methods:
Tagging
- Following indivs
- Possibility based

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14
Q

Population growth in ‘open’ systems

A

Nt + 1 = Nt + (birth-deaths) + (immigrants - emigrants)

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15
Q

Estimating demographic rates - Migrants

A

Tracnking movement

Tagging:
- Physical
- GPS
- Radio telemetry
- Acoustic

Population genetics

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16
Q

Estimating population size method

A

Mark-Release- Recapture (MRR)
- Estimates total population from sample proportion of recatures of mobile species.

Assumtions often hard to satisfy
- Closed population
- All organisms are equally able to be caught again
- tags not lost

17
Q

Mark-Release- Recapture (MRR) equaiton

A

M/T = r/n

M = Number Marked
T = est. pop. size

r = recaptures
n = number caught on second attempt

18
Q

Spacially structured populations

A

Metapopulations:
- Local population but individuals move
- Demographic rates vary spacially
- Large-scaled dynamics depends on local demographics and connectivity

19
Q

Estimating growth and age

A

trees = rings

mammals = teeth

Fish = otoliths

20
Q

Understanding age and size-structured population dynamics

A

Age and/ or size of individuals affects:
- Fecundity
- Survival

21
Q

Population viability analysis (PVA)

A
  • Tool to model dynamics over time

Uses:
- pop size/ carrying capacity
- Fecundity
- Mortality
- Inter-annual variations in parameters

22
Q

Extinctions

A

Processes of chance that contributes to an extinction event:

  • Catastrophes
  • Human impacts

Stochasticity:
- Genetics
- Demographic
- Environmental