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Eco & Evo 2 > Population growth & life histories > Flashcards

Population growth & life histories Flashcards

1
Q

Which 4 processes affect population size?

A

Births
Immigration
Deaths
Emigration

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2
Q

What is the calculation for change in population size?

A

Change in pop size = (births + immigration) - (deaths + emigration)

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3
Q

What are intrinsic factors?

A

Factors that affect a population size from within a population
e.g. age of 1st reproduction

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4
Q

What are extrinsic factors?

A

Factors that affect a population size from outside the population
e.g. predation, weather

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5
Q

How can intrinsic factors be divided up?

A

Density-dependent factors
= population rate decreases as population size & crowding increase
e.g. effects of food supply & breeding sites

Density-independent factors
= influence populations independently of population size
e.g. effects of weather & catastrophes - volcanoes

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6
Q

What happens to the populations of most plants & animals over time?

What is the most likely reasoning behind fluctuations in a population size?

A

Fluctuate

Extrinsic factors

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7
Q

What does r represent?

A

Intrinsic growth rate = b-d
(per capita)

where:
b = per capita birth rate
d = per capita death rate

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8
Q

What is the equation for the tangent on a population growth curve?

A

dN/dt = rN

r at that instant

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9
Q

What is the equation for the change in population size over a time?

A

/\N / /\t = rN

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10
Q

Describe pop growth when growth rate is constant.

What prevents populations growing indefinitely?

A

Exponential

Limited resources

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11
Q

When does growth decrease?

Define K

A

As the no. of indivs approaches the carrying capacity of the environment (K)

Limit at which populations stop growing

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12
Q

The rate at which growth slows depends on what?

A

How close the pop size is to K

When N=K, no growth

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13
Q

What is an example of a factor besides K that can affect real pop growth?
(Not shown by the logistic model)

A

Lag-time in response to change in conditions

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14
Q

r is the same for which types of growth?

A

logistic & exponential

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15
Q

Exponential growth describes pop growth when?

A

There’s no shortage of supplies

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16
Q

The logistic model describes what?

A

Approx growth of most natural pops

17
Q

What are life history traits?

A

The pattern of survival & reproduction events typical for a member of that species.
Represent optimisation of trade-offs between growth, survival & reproduction

18
Q

Give examples of life history traits.

A 
>Age & size at reproduction 
>No. of reproductive seasons
- semelparous = once
- iteroparous = many 
>Life span
- annual vs perennial
>No. & size of offspring
19
Q

Describe the perfect life history

Why doesn’t this exist?

What is thus generated?

A

Sexually mature at birth
Continuously produces high-quality offspring in large no.s
Lives forever

Amount of resources available = finite

Trade-offs

20
Q

What happens to your reproductive output as you max lifespan increases?

A

Decreases

21
Q

Define life span

Define senescence

A

The avg length of life
(determined by senescence if in protected enviro)

Gradual deterioration of functional characteristics
aka ageing

22
Q

Even if orgs had the ability to live forever, why wouldn’t they?

A

Random chance
Predators
Parasites

23
Q

The probability of reproducing reduces with…?

A

Age

24
Q

Why don’t orgs reproduce v young?

A

Due to small size + no. of low quality offspring that would be produced
–> low chance of survival

25
Q

Describe the example that shows reproduction is costly

A

Red deer

Mothers caring for infants have higher chance of dying than those not nursing

26
Q

What are the 2 commonly studied trade-offs shaped by natural selection?

A

Life span vs reproductive output

offspring size vs no. of offspring

27
Q

What was David Lack’s (1947) hypothesis?

A

Natural selection will favour the clutch size that produces the most surviving offspring

28
Q

If it’s better to maximise the no. of offspring, why do such extremes exist where an org will produce 1 large offspring?

A

Diff envrios may favour diff strategies

29
Q

What features do ‘r-selected’ populations have?

A

Reproduce rapidly
Use resources wastefully
Success replies upon finding new resources elsewhere

30
Q

What features do ‘K-selected’ populations have?

A

Breed slower

Use resources more efficiently

31
Q

What are the pros of r-selected populations?

A

Large progenies
High dispersal
Unlimited enviro
Low competition

32
Q

What are the cons of r-selected populations?

A

Short life time

High predation

33
Q

What are the cons of K- selected species?

A

Slow to mature
Competitive enviros
High mortality risk
High parental care

Eco & Evo 2 (16 decks)

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