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BIOL 370 > Problems with small populations (class 15) > Flashcards

Problems with small populations (class 15) Flashcards

1
Q

“No population lasts forever”- Name 3 reasons why every population eventually goes extinct.

A
  • changing climate
  • succession
  • disease
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2
Q

What is conservation biology concerned with in this section?

A

Whether populations go extinct sooner rather than later, and whether other populations of the same species will continue elsewhere

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3
Q

What is “the key to conserving species”?

A

Protecting populations, as endangered species often consist of a few populations

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4
Q

What is the ideal goal of a conservation plan?

A
  • to protect as many individuals as possible within the greatest possible area of high-quality protected habitat
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5
Q

What does MVP stand for?

A

Minimum viable population

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6
Q

What is MVP?

A

The number of individuals necessary to ensure the long-term survival of a species (through both average and harsh years)

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7
Q

Numerically, how is MVP defined?

A

The smallest isolated population having a 99% chance of remaining extant (surviving) for 1000 years despite the foreseeable effects changes/catastrophies

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8
Q

For vertebrates, what does the MVP value average around?

A

between 3000-5000 individuals

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9
Q

A greater length of persistence requires what?

A

Greater population size

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10
Q

Graph about bighorn sheep- survival time vs initial population size. What is the number of individuals that last 50 years?

A

Populations with more than 100 individuals lasted about 50 years.
Populations with less than 50 animals often went extinct within 50 years

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11
Q

Channel island bird populations- How many breeding pairs were needs for a 90% chance of surviving 80 years?

A

Over 100 breeding pairs needed for 90% chance of survival for 80 years

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12
Q

What is MDA?

A

Minimum dynamic area. The area of suitable habitat necessary for maintaining the minimum viable population

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13
Q

How can MDA be estimated?

A

can be estimated by studying the home range size of individuals and colonies of endangered species

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14
Q

What is the MDA or small mammals vs large carnivores?

A

100-1000 km2 for small mammals.

10,000 km2 needed for large carnivores

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15
Q

Why does genetic variability occur?

A

Occurs as a result of individuals having different alleles (dif. forms of same gene)

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16
Q

What does a population’s genetic variability affect?

A

It affects the population’s ability to adapt to a changing environment

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17
Q

Population declines in small populations result in what?

A

Lower genetic diversity

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18
Q

True or false:

species with low genetic diversity have small populations

A

FALSE. Species with low genetic diversity do not necessarily have small populations

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19
Q

In small populations, why might allele frequencies change significantly in one generation?

A

CHANCE! Based on which individuals survive to sexual maturity and mate

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20
Q

The random process of allele frequency change is called…?

A

Genetic drift

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21
Q

What is the risk of an allele that occurs at a low frequency in a population?

A

That it has a significant chance of being lost in each generation

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22
Q

What does maintenance of genetic diversity depend on?

A

The effective population size

(Ne)= the number of breeding individuals in a population

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23
Q

What does this equation show: H= 1-1/ (2Ne) ?

A

The proportion of original heterozygosity remaining after each generation (H), with (Ne) being effective pop size

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24
Q

What 2 processes increase genetic variability of a population?

A

1) regular mutation of genes

2) migration of even a few individuals from distant populations

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25
What is an average mutation rate?
Between 1/10,000 and 1/one million
26
Is mutation enough to counterbalance effects of drift in populations of less than 100 individuals?
No
27
What is the percentage of mutation rate per gene per generation to counteract effects of drift?
1% per gene per generation
28
Is migration or mutation better at counteracting drift?
Migration, even low frequency of migration among populations helps. Migration of 1-2 individuals per gen. in pop of 100 can minimize loss of genetic diversity
29
What number of migrants in a generation with pop of 100 fully negates the effects of drift?
4-10 migrants (high migration is good)
30
Rare and endangered species often have _____ _____ populations
Small and isolated
31
Give an example of a rare species in Australia with little genetic variation
Wollemi pine, species consists of 40 plants in 2 nearby populations, lacks genetic variation completely
32
How big should a population be? What's a rule to show this?
50/500 rule. 50 reproductive individuals needed to avoid short-term inbreeding depression. 500 needed to generate adequate mutation to balance loss of alleles through drift
33
What is the 50/500 rule best used for?
Urgent conservation efforts. Larger population numbers needed for long-term health of populations and species
34
What are the 3 consequences of reduced genetic variability?
1) inbreeding depression 2) outbreeding depression 3) loss of evolutionary flexibility
35
What is inbreeding depression?
condition that occurs when an individual recieves identical copies of a defective allele from both parents.
36
What is inbreeding depression characterized by?
Higher mortality of offspring, fewer offspring, or offspring that are weak, sterile, or have low mating success
37
What populations are prone to inbreeding?
Small captive populations in zoos, or small isolated populations in the wild
38
In a study of 51 bird species, what is the consequence of small population sizes?
Hatching failure due to inbreeding depression in the wild
39
What is outbreeding depression?
When an individual mates with an individual of a different related species. (can also happen from mating between dif subspecies or divergent populations of the same species)
40
What can outbreeding depression result in?
Weakness, sterility, or lack of adaptability to the environment
41
Give an example of outbreeding.
horse and donkey = sterile mule | - could also be captive bred individuals with wild individuals (weaken the gene pool)
42
What have studies found about outbreeding depression?
Many studies have failed to demonstrate it
43
What is hybrid vigor? (related to outbreeding)
Often, many hybrid individuals are more vigorous than their parents
44
Explain the loss of evolutionary flexibility
loss of genetic variability limits ability to respond to new conditions and long-term changes in the environment
45
rare alleles and unusual combos of alleles that are harmless may turn out to be what...?
They may be uniquely suited for a future set of environmental conditions, and give an advantage later to the individuals that have them
46
What are 3 ways an environment could change that a unique allele could be an advantage?
pollution, climate change, new diseases
47
What are the 4 factors that determine effective population size?
1) unequal sex ratio 2) variation in reproductive output 3) population fluctuations and bottlenecks 4) managing for genetic variation
48
What is effective population size?
Mature individuals that can mate | - it is lower than total pop. size b/c many individuals do not mate
49
Effective pop size- Describe unequal sex ratio.
As the sex ratio of breeding individuals becomes less equal, Ne goes down. Can also occur when a few individuals of one sex make up a disproportionate amount of genetic material in the next gen (elephant seals- one dominant male)
50
What is the problem with climate change for the sex ratio?
Climate change skews the sex ratio of species with temperature dependent sex-determination (ex. fish)
51
Effective pop. size- Describe variation in reproductive output
Occurs in species where a number of offspring varies substantially among individuals. Ex. large plants produce more seeds than small plants
52
Effective pop. size- Describe population fluctuation and bottlenecks
Ne is largely determined by years in which the population has the smallest number of breeding individuals
53
Effective pop size- define population bottleneck
Occurs when a population is greatly reduced in size and loses rare alleles if no individuals possessing those alleles survive and reproduce
54
Effective pop size- Define founder effect
special type of bottleneck that occurs when a few individuals leave one population to establish a new one. New pop has less genetic variabiliy
55
Give one example of a bottleneck population
Ngorongoro Crater lions were reduced from 9 females and 1 male at one point
56
Name a less prevalent factor that affects the persistence of small populations
- stochasticty (random variation) | - can be environmental or demographic (variation of birth and death rates among years)
57
Define the allee effect
The interaction between population size, density, growth rate, and behaviour.
58
Why are many small populations demographically unstable? And give an example.
because social interactions can be disrupted once population density falls below a certain level (ex. Bears live in widely dispersed pop and can have a hard time finding a mate if density is too low)
59
What is an extinction vortex?
tendency of a small population to spiral towards extinction
60
What are the factors that can cause an extinction vortex?
The smaller a population becomes, the more vulnerable it is to further demographic variation, environmental variation, and genetic factors that tend to lower reproduction
61
To what extent does each factor of an extinction vortex increase vulnerability?
Each factor increases vulnerability to the other 2, they build on each other
62
How can extinction vortices be handled?
Only addressing the original cause of pop. decline may not be enough to recover the pop.. Need to do more than this.

BIOL 370 (9 decks)

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