Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Conservation > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

Which populations are most at risk?

A

Rare species - small geographic range or low population density
Because higher risk of extinction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Minimum viable population size

A

Minimum number of individuals needed in a population

Small isolated populations have reduced viability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Study on population viability of British birds

A

6-12 breeding pairs = 7.5 years to extinction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

PHVA

A

Population and habitat viability analysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Environmental risk and natural catastrophes

A

Both affect species irrespective of population size

General pattern on isolated island populations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Example of effect of natural catastrophe on species (1)

A

Rodrigues fruit bag
Cyclones devastate population irrespective of numbers
Solution may be increasing population size on Rodrigues or establishing a second population on nearby Diego Garcia
O’Brien et al., 2007

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Example of effect of natural catastrophe on species (2)

A

Sisserou parrot (Amazona imperialis)
Dominican parrots live in one patch forest
After hurricane, shortage of fruits for some time
Parrot numbers decline for couple of years after hurricane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is demographic stochasticity?

A

The result of chance independent events of individual mortality and reproduction, causing random fluctuations in population growth rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How are small populations negatively affected by demographic stochasticity?

A

Small populations closer to extinction

Problem with small populations and reproductive rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

BIDE

A

Births
Immigration
Deaths
Emigration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Carrying capacity (K)

A

The natural limit set on populations by availability of resources

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What affects carrying capacity?

A

Interspecific competition - one species affects resources available to another (varies between habitats)
Facilitation - when one species benefits from the other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is irruptive growth?

A 
Explosions and crashes in population numbers
Regulated by resource availability
Wide variation around carrying capacity
Typical r-strategists
Few species
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is logistic growth?

A

Sigmoidal curve
Growth rate regulated by intrinsic factors (density-dependent mortality, birth rates)
Typical K-strategists
Most species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

K-strategist small populations

A

In small populations, individuals reproductive rates are high but numbers are low
If population is reduced, early recovery is slow
At half the carrying capacity there is a rapid escalation in numbers
Near carrying capacity the rate of population growth declines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the maximum sustainable yield?

A

Half carrying capacity
Inflection point K/2
Aims at a balance between too much and too little harvest to keep the population at an intermediate abundance with a maximum replacement rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Example of problem with getting maximum sustainable yield wrong

A

Orange roughy fish found around seamounts discovered in 1990s
By 2008 only 10% of original stocks
This was due to using demographic factors from other fish to calculate MSY

18
Q

Problems with calculating MSY for small populations

A
  • Calculating population growth rates more difficult if wide variation in numbers
  • Small populations suffer erratic size swings due to demographic stochasticity
19
Q

Problems when applying MSY

A
  1. Very difficult to get accurate estimates of population size
  2. Carrying capacity changes; impossible to estimate
  3. Basic demographic data rare as varies between populations
  4. Difficult to get measures of other forms of mortality
  5. Social systems and mating strategies often unknown
  6. Pays to over-harvest long-lived species as they will be driven to extinction
20
Q

What is the threshold response to habitat change over time?

A

Populations crash because response to perturbation not linear

21
Q

Who wrote the paper showing the three basic responses of British mammals to habitat fragmentation?

A

Bright, 1993

22
Q

What is the species pool of genetic diversity?

A

Total genetic variation of species partitioned into within versus between population diversity

23
Q

Species pool of genetic diversity in 3 levels

A
  1. Variation within individuals
  2. Variation within populations
  3. Variations between populations
24
Q

Species pool of genetic diversity level 1: variation within individuals

A
  • Heritable genetic variation (basis for evolution)

- Species should be heterozygous

25
Q

Species pool of genetic diversity level 2: variation within populations

A
  • Gene pool

- Type of alleles and frequency they occur across the population

26
Q

Species pool of genetic diversity level 3: variation between population

A
  • Rare for a single species to be one large panmictic population
  • Allows for individual populations to adapt to local circumstances
27
Q

Is heterozygosity important?

A

Not much evidence but likely that it is
Correlations between fitness and heterozygosity are weak
Variation in natural populations
Don’t know how heterozygosity is translated into fitness

28
Q

In what species is heterozygosity important?

A

Common toad

Less abnormalities with increasing heterozygosity

29
Q

In what species is heterozygosity less important?

A

South African cheetahs

Low genetic diversity

30
Q

Rule of thumb with heterozygosity

A

Larger populations have higher heterozygosity

Smaller populations lose heterozygosity over time

31
Q

How is genetic diversity lost?

A
  1. Founder effects
  2. Demographic bottleneck
  3. Genetic drift
  4. Inbreeding
32
Q

How is genetic diversity lost - founder effect

A
  • Only a few individuals establish a new population
  • New population biased
  • Not representative of the whole population
  • Lower genetic diversity
33
Q

How is genetic diversity lost - demographic bottleneck

A
  • Occurs when temporary reduction in population size

- Relatively few animals go through bottleneck so a lot of genetic variability is lost

34
Q

How is genetic diversity lost - genetic drift

A
  • Change in frequency of an existing allele in a population due to random sampling of organisms
  • The rate of allele loss increases with disparity of adult sex ratio, and bias in mating success (e.g. polygynous species)
35
Q

How is genetic diversity lost - inbreeding

A
  • When individuals mate with close relatives
  • Increases homozygosity
  • Progeny can inherit deleterious traits
36
Q

General results of inbreeding on offspring

A
  • Reduced fecundity
  • Offspring smaller
  • Less likely to survive
  • Increased physical deformities
37
Q

How to help maintain genetic diversity?

A
  • Understanding the genetic problems that small populations face
  • Encourage heterosis (outbreeding/producing hybrids) as offspring have increased vigour and are fitter than both parents
38
Q

Effective population size

A

Number of breeding individuals in population (not all animals breed)

39
Q

Rate of genetic loss taking into account effective population size

A

N(e) is the effective population size

The rate of genetic loss is 1/2N(e)

40
Q

What is the 50/500 rule?

A

Minimum effective population of 50 will limit deleterious effects of inbreeding
Longer-term minimum effective population size 500 will maintain genetic variation for adaptive evolution

41
Q

What two species recovered from very low population sizes?

A

Arabian oryx

Przewalski’s horse

42
Q

To allow for non-breeders, what is the alteration to the 50/500 rule for different animals?

A

100/200 for birds

1000/2000 for mammals

Conservation (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions