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Anatomy II Exam 2: Lectures 9-16 > Lecture 16: Life History > Flashcards

Lecture 16: Life History Flashcards

1
Q

What is life history, from a biological perspective?

A

Defined as the sequence of anatomical, physiological, and behavioral changes and events that an organism experiences over the course of its lifetime

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2
Q

What are the 6 primary stages that the life of a mammal can be divided into?

A

1) fetal (gestation)
2) infancy
3) juvenile
4) subadult
5) adult
6) post-reproductive (female)

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3
Q

How does the variation of the 6 primary stages of life define a life history?

A

Variation in the length of these stages along with the way a species allocates resources to each phase defines a life history

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4
Q

How did the phases of life history change with primates (especially apes and humans)?

A

In general, we have extended each phase of life history

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5
Q

There is a relationship between the amount of energy that a species invests in growth and development and what?

A

The number of offspring produced

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6
Q

What is an R strategist?

A

Minimal investment in individual growth with a high reproductive output

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7
Q

What does “R” in R strategist stand for?

A

Rate of increase in population

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8
Q

What is a K strategist?

A

Maximum investment in individual growth and low reproductive output

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9
Q

What does “K” in K strategist stand for?

A

Carrying capacity of environment (max sustainable population size)

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10
Q

What is the logistical population growth model?

A
  • When N (population size) is very small, effect of limited resources is negligible
  • As N approaches K (carrying capacity), rate of population increase declines
  • When N=K, there is no population growth
  • When N>K, the population Celine’s because demand exceeds available resources
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11
Q

R strategy populations tend to have what type of enervironment? What about K strategy pops?

A

R=highly variable and unpredictable

K=stable, predictable environments

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12
Q

Which strategy (R or K or both) has a density dependent mortality rate?

A

K strategy= density dependent mortality

R=density independent

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13
Q

Does K or R strategy show faster growing populations?

A

R

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14
Q

Which strategy (R or K) has a variable population size and where do they fall in relation to carrying capacitys?

A 
R= variable population size and below carrying capacity 
K= stable population and near K
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15
Q

How do R strategy populations compete vs K strategy?

A

R= compete by having high reproductive output and colonizing of new areas
K=compete by exploiting available resources

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16
Q

What does the species success for both R and K strategy populations rely on?

A

R= habitat change and chance

K=quality of offspring

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17
Q

What does high resource allocation go to in R strategy vs K strategy?

A

R=to reproduction

K= to growth and maintenance

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18
Q

What is the parental investment in offspring for R strategy vs K strategy?

A

R= low parental investment

K=large parental investment

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19
Q

How does the offspring birthweight and development compare between R and K strategy?

A 
R= small/low birth weight and rapidly developing
K= offspring large/high birth weight, slow developing
20
Q

How does offspring mortality, life span and gestation compare between R and K strategy?

A 
R= high offspring mortality, short life span, short gestation 
K= low offspring mortality, long life span, long gestation
21
Q

How does weaning occur in R strategy vs K?

A 
R= early weaning
K= Late weaning
22
Q

Why are oysters a good example of a very r-strategy?

A

They produce 500 million fertilized eggs per year and provide no parental care

23
Q

Why are great apes a good example of a very k-strategy?

A

They produce one infant every 5 or 6 years and provide extensive parental care

24
Q

What are indicators of K selection?

A

Increase in animal body size and complexity over time. Larger size and great complexity=K

25
Q

What is the “scala naturae” trend?

A
  • Marine invertebrates release huge numbers of eggs or larvae –>
  • Lower invertebrates show more parental investment–>
  • tetrapods (and lower vertebrates) then encountered more variable environments, requiring slower developmental rates and reduction in # of offspring, greater parental investment –>
  • Mammals increased metabolism to tolerate greater environmental fluctuations, eating to larger brain size, more complex behavior, higher calorie requirements, high level of parental investment, slow growth, fewer young
26
Q

What is the general pattern for primates for first reproduction, fertility rate and life spans?

A
  • relatively late ages at first reproduction
  • low fertility (few offspring)
  • Long life spans
27
Q

What does the general primate life history point toward?

A

A pattern of relatively reduced reproductive effort, but high parental investments

28
Q

The following describes which stage of human life history:

  • gestation period (maternal investment)
  • total dependence on mother
  • maternal energy allocated to fetal growth
  • the more time and energy allocated, the better the chances of survival to birth
  • maternal trade offs include vulnerability to predators and cost of delaying the next offspring
A

Fetal period in general

29
Q

Is the length of human gestation comparable to other primates?

A

Yes, chimps=216-260 days; orangutan=240-270 days; humans=266 days; gorilla=270 days

30
Q

Why is human gestation thought to be unusually short? How is this possible?

A

Unusually short for our large brain size (which is extreme for our body size). Humans are unique in that our brains continue to grow significantly after birth

31
Q

What percent of the adult size are newborn human brains? Newborn chimps?

A

Human newborns=25% of adult size

Chimps=47% of adult size

32
Q

The following describes which stage of human life history:

  • period of continued dependence on mother
  • high energetic demands on mother
A

Infancy

33
Q

What is the average age for humans of weaning, taking into account data from 64 traditional human societies?

A

Just<3 years old

34
Q

The following describes which stage of human life history:

  • Association with dental eruption
  • not reproductively mature
A

Juvenile period

35
Q

When does infancy end by definition?

A

Infancy ends with weaning, when young are able to forage independently and ingest solid food

36
Q

Do humans have a long juvenile period?

A

Compared to other primates, we have a relatively long one

37
Q

The following describes which stage of human life history:

  • puberty, the process of becoming sexually mature
  • Once an individual passes through puberty and is sexually mature, they are biologically an adult
  • Species specific body mass associations
A

Subadult (adolescent)

38
Q

The following describes which stage of human life history:

  • Reproductive decline associated with old age
  • males experience a more gradual long-term decline
  • female humans are unique in experiencing menopause; total and permanent cessation of ovulation
A

Post-reproductive stage

39
Q

What age does menopause in human females occur around?

A

50

40
Q

What is it thought that menopause is a consequence of?

A

The compromise between early intensive investment in offspring and individual longevity

41
Q

What are two reasons (hypotheses) as to why females live past the age of reproduction in humans?

A

“Grandmother” hypothesis and extended kin selection

42
Q

What is the human life expectancy?

A

Now exceeds 80 years of age and continues to increase

43
Q

Is longevity and life expectancy the same thing?

A

No, under “ideal” conditions the human life span can exceed 120 years

44
Q

What plays into human longevity?

A

Environmental factors play a huge role but there is a significant underlying genetic factor. Longevity is subject to selection and has evolved over the years

45
Q

How does higher investment in growth and reproduction alter life span?

A

It can reduce it. It has been observed in many species that lower calorie intake, which reduces growth and potentially reproduction, is also associated with longevity

46
Q

How is brain size correlated to longevity?

A

High brains are associated with slower development, which in turn is associated with long lifespan

Anatomy II Exam 2: Lectures 9-16 (9 decks)

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