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BB10205 > Evolution 2 > Flashcards

Evolution 2 Flashcards

1
Q

What are processes that affect population size?

A

Births, deaths, emigration and immigration.

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2
Q

What are intrinsic factors that affect population size?

A

Factors such as the age of first reproduction - directly related to the individual and are built into the genetic basis of the individual.

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3
Q

What are extrinsic factors that affect population size?

A

External factors such as predation and natural catastrophes.

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4
Q

What are density dependent factors?

A

Factors that affect the size of the population in a way dependent on the size of the population such as the effects of food supply.

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5
Q

What are density independent factors?

A

Factors that influence populations independently from population size such as the effects of weather and catastrophic events.

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6
Q

What is the population change dependent on?

A

Births-deaths.

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7
Q

What is more useful than calculating births and deaths over a certain time?

A

Per capita birth/death rate.

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8
Q

What is r?

A

Intrinsic growth rate.

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9
Q

What is the exponential population growth curve?

A

dN/dt = r (instant)N where dN is a small change in the number of individuals and dt is a small change in time.

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10
Q

What do we know if we know r?

A

The population dynamics.

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11
Q

What prevents populations from growing indefinitely?

A

Limited resources.

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12
Q

When does growth start to decrease?

A

As the number of individuals approaches the carrying capacity of the environment.

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13
Q

What other factors beside the carrying capacity are important?

A

Lagtime in the response to change in conditions.

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14
Q

What is population growth linked to?

A

Life history traits.

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15
Q

What are life history traits determined by?

A

Evolutionary constraints and natural selection.

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16
Q

Example of animal that lives for a short time but produces lots of offspring?

A

Flies.

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17
Q

Example of animal that lives for a long period of time but only produces a few offspring?

A

Albatrosses.

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18
Q

What is life history?

A

The pattern of allocation to growth, development, reproduction, survival etc.

19
Q

What does semelparous mean?

A

Only one reproductive season.

20
Q

What does iteroparous mean?

A

Have many reproductive seasons.

21
Q

What are some life history traits?

A

Age and size at reproduction, number of reproductive seasons, life span, number and size of offspring.

22
Q

What are the predictions for the perfect life history?

A

Mature at birth, continuously produce high-quality offspring in large numbers and live forever.

23
Q

Why does the perfect life history not exist?

A

The amount of resources available to an organism is finite - this generates trade offs.

24
Q

What may a mutation result in in terms of life history strategies?

A

There may be an increase in the focus on reproduction rather than maintenance or growth.

25
Q

What is a common trade off?

A

Life span vs reproductive output.

26
Q

Why is life span different from senescence?

A

Life span is only determined by senescence if an organism lives in a protected environment.

27
Q

What is senescence?

A

The condition of process of deterioration with age.

28
Q

Even if an organism could live forever, why doesn’t it?

A

Due to random chance, predators and parasites.

29
Q

What is life span a result of?

A

An organisms genetics and its environment.

30
Q

What is a result of the factors influencing lifespan?

A

The probability of reproducing reduces with age.

31
Q

Why do organisms not always reproduce really early?

A

Larger individuals produce more and/or larger offspring.

32
Q

What happens if reproduction occurs too early?

A

There is not sufficient resources and there is selection to reproduce later.

33
Q

What happens if reproduction occurs too late?

A

Death comes before reproduction and there is selection to reproduce earlier.

34
Q

What does natural selection favour?

A

Maximum total fitness - for organisms that reproduce multiple times, the number of progenies is important, and not just the size of the clutch.

35
Q

How does mortality rate differ between deer nursing and deer not nursing?

A

Mortality for deer that are not nursing is much less than for those that are nursing.

36
Q

What did experiments with male drosophila show about reproduction?

A

Males kept with inseminated females/no females lived longer than those kept with virgin females.

37
Q

Why can large numbers of large offspring not be produced?

A

There are limited resources.

38
Q

What does natural selection favour in terms of clutch size?

A

The clutch size that produces the most surviving offspring.

39
Q

What is experimental evidence for the ideal clutch size?

A

Experiment with a magpie - showed that the modal clutch size of 7 is optimum- maximises the size of the offspring.

40
Q

Why do extremes still exist between number and size of offspring?

A

Different environments may favour different strategies.

41
Q

What are r selected populations?

A

They reproduce rapidly and use resources wastefully. Their success relies on finding new resources elsewhere.

42
Q

What are K selected populations.

A

They breed slower and use resources more efficiently.

43
Q

What are the characteristics of R selected populations?

A

They have small organisms, short life time, large progenies, small offspring and high dispersal. There is low competition, high predation.

44
Q

What are the characteristics of K selected species?

A

They are larger individuals that are slow to mature and have few large offspring. There is high parental care and competitive environments. There is a high risk of mortaility in these environments.

BB10205 (15 decks)

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