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Evolutionary Biology Yr 2 > Life history > Flashcards

Life history Flashcards

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1
Q

Life history is the … of an organisms life, including birth, …, … and death

A

maturation, reproduction

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2
Q 
Life history includes:
1. ... and ... at maturity
2. ... and ... of offspring
3 ... allocation to reproduction
4. ... of growth and development
5. ... patterns
6. number of ... events
7. Lifespan and ...
A
  1. age, size
  2. number, size
  3. energy
  4. timing
  5. dispersal
  6. reproduction
  7. ageing
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3
Q

There is huge … in approaches to life histories across the tree of life

A

variety

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4
Q

Selection acts to maximise the … … … of organisms

A

lifetime reproductive success

  • produces very different effects in different organisms
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5
Q

In order to maximise LRS you’d ideally want:

  • … development
  • … maturity
  • high … investment
  • high … rate
  • long …

Why not maximise all of these?

A

fast, rapid, parental, reproduction, life

reproduction is costly, requiring resources and time - trade-off between different methods of maximisation - different species selected for different methods

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6
Q

Give e.g. of two organisms with very different life history strategies to maximise LRS

A

Brown rat - fast development and maturity (2 weeks), high reproductive rate (5 litters of up to 14 individuals/year) but low parental investment (95% die within year) and a short life (3 years max)

African elephant - slow development and delayed maturity (20 years) with a low reproductive rate (1 calf/ 2.5 to 9 years), but high parental investment and a long life (up to 70 years)

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7
Q

What decides life history strategy?

A

Intrinsic factors: e.g. energy/resource constraints, genetic constraints, phylogenetic constraints, mechanical constraints, physiological constraints (e.g. silkmoth adults don’t have mouthparts so rely on resources and nutrition from larval stage)

Extrinsic factors: e.g. ecological factors (predation, mate availability etc.) and climatic constraints

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8
Q

What is senescence?

A

age-related deterioration of an organism leading to a decline in reproduction and probability of survival

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9
Q

Why does senescence occur (from an evolutionary perspective)? what are the main theories?

A
  1. Mutation accumulation
  2. Antagonistic pleiotropy
  3. Disposable soma
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10
Q

Selection is most effective for life strategies with … … …

A

high reproductive rate
(e.g. if an organism is too old to reproduce effectively or at all anymore it won’t pass on any genes to offspring so selection won’t be acting strongly at all anyway)

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11
Q

Mutation accumulation hypothesis for senescence - mutations that are … later in life are more likely to be maintained in the population (selected against far less than mutations that are deleterious earlier in life). These are able to accumulate in the population

A

deleterious

e.g. huntington’s disease in humans (can reproduce before kicks in - doesn’t prevent this like earlier effect mutations)

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12
Q

Antagonistic pleiotropy - pleiotropic genes that effect more than one phenotypic trait can be … for one trait but … for the other, leading to a …-…. Again, selection acts more strongly towards traits that are positive … in life, even if they lead to more negative traits … in life, as it this doesn’t negatively effect LRS as much.

A

positive, negative, trade-off, earlier, later

  • e.g. gene that causes overproduction of sex hormones (e.g. oestrogen and progesterone) - good for reproduction but can lead to cancer later in life
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13
Q

What is the disposable soma hypothesis?

A
  • resources are finite - energy put towards one function (growth, maintenance, reproduction) is unavailable for others
  • limit towards maintenance causes somatic damage (many different types) - if allocating it towards reproduction instead, for example
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14
Q

Overwhelming current view: all hypotheses are linked and we can’t … energy from function

A

decouple

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15
Q

What is the idea behind maturity?

A
  • if you have time and energy to develop and grow then when you come to reproducing you will be a better parent and your offspring are more likely to survive and spread your genes - despite losing out on reproducing offspring while reaching maturity
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16
Q 
Guppies: 
High predation (Crenicichla) - females mature at ... ..., and produce ..., .... offspring. Males also mature at a ... ... (although weaker effect than females.

Low predation (Rivula) - females mature at … … and produce …, … offspring. Males also mature at a … … (although weaker effect than females.

Same replication of effect with gobie and mullet predation

A

smaller size, more, smaller, smaller size

larger size, fewer, larger, larger size

17
Q

There is always a tradeoff between the … and … of offspring. From the offspring’s point of view it is beneficial to be …, as it gives them a better chance of surviving to reproduce and they don’t have to share resources around as much. From the parents’ point of view, a few …, … offspring are better - risky to put all eggs in one basket. There is …-… conflict in selection. Selection will act to … the different parts of this argument

A

size, number, larger, more, smaller, parent-offspring, optimise

18
Q

Tropical bird species tend to have … clutches with a slower growth rate than those living in temperate climates. This goes against what we typically see in these climates (more resources for quicker development in tropical). Why is this?

A

smaller

answered in 2015 by Martin, by using life history theory. - at first thought to do with predation rate being higher (as in guppies) - however found out that for the same predation rate, tropical birds had a lower growth rate as temperate. Also, nest period shorter in tropic for the same growth rate.

  • realised were measuring growth rate wrong by assuming it was continuous
  • collected more data and found out that initial growth rate is slower in tropical species but it becomes faster and reach the same mass
  • temperate species grow more quickly initially but then slow down development
  • The mass is the same at fledging
  • but the growth rate for wings is actually higher in the tropics, so they fledge with longer wings - because predation risk is higher and being able to fly well aids survival
  • growing wings is very expensive - can only increase wing size with parental provisioning
  • the more a parent visits the nest though, the higher the chance of predation of the nest
  • therefore the parent has a smaller clutch (to maximise provision while minimising chance of predation)

Evolutionary Biology Yr 2 (5 decks)

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