Life History Evolution - 3 | Growth & Maturation

• Biologie
• Middelbare school
• vmbo b
• Leerjaar 3

Lecture Marc Naguib
Growth and sexual maturity

Growth & Sexual maturity

- Age and size at maturity

- Sex differences in age and size at maturity

- Age at maturity in humans

Fitness effects in fish

- Growth curves and reaction norms

- Growth and sexual maturity in guppies

- Effects of the social context in guinea pigs

Grows slowly

Reaches 60 cm

Matures at 14 years

Lives 30 years

Grows fast

Reaches 25 cm

Mature at 3 years

Lives 6 years

What makes fish good examples for age and size of maturity?

What components for the differences could researchers investigate? 

In

In what region do you expect which factor? 

Newfoundland

Scotland

Warmer water

no feeding in winter (stress)

maturation during winter is costly

cold water

increase in investment will cause more stress and lower white muscle fibre weight, which leads to lower predator avoidance

pays to grow to size where predation is low and to mature at that size

no winter fasting

less predation pressure so maturing earlier pays off

What are benefits of later maturation?

What are costs of late maturation?

What are benefits of early maturation?

What are costs of early maturation?

1. What is similar for fish and mammals?

2. What is different? 
3. How could the differences be explained?

1. When can it be beneficial to start as a female?

2. When can it be beneficial to start as a male? 

If there's an optimum situation for time of maturation and reproduction, why does not everyone follow it? (Why are individuals not born with a fixed decision rule?)

Why are guppies a very usefull species for research?

What answer is least correct?

1. Strong variation in life history traits among populations, short generation time (as do birds)
2. Fecundity is size dependent
3. More similar physiology to humans than other species
4. Experimental possibilities in field and lab

females produce fewer offspring

females produce bigger offspring

females produce many offspring

females produce smaller offspring

Intro | Become large with compensatory growth or stay small....
When there are poor nutritional conditions, it pays off to remain small, but larger individuals have higher fecundity. What are the trade-offs?

Blue line: you're in good conditions, you mature early / red line: you're not in good conditions and you age differently

What is a heterogeneous environment?

1. An unpredictable and diverse environment (div nesting situations / nutrional / predator wise)
2. Environment that is predictable an not diverse

What is the conclusion drawn from the graph?

What is a life-history trait?

What is a life-history trade-off?

How can intrinsic AND extrinsic factors influence phenotypic plasticity

Why does demography depend on life history events?

Why does the evolution of life history traits depend on the demography of a population?

A. Give a definition and an implication of the “Predictive Adaptive Response” (PAR) hypothesis. B. Give two conditions required for the evolution of a predictive adaptive response.

ANWERS: See Dr. Piter Bijma’s lectures. The PAR hypothesis is also explained in the second paragraph of the introduction of the paper by Rickard and Lummaa(2007). Two conditions for the evolution of PAR are i) the environment that the mother experiences must be predictive of the offspring environment, ii) the environmental fluctuation that elicits the hypothesized PAR must be of sufficient frequency to maintain the selective advantage of plasticity. (These are just two answers, there are more in the paper: Rickard, I. J., & Lummaa, V. (2007). The predictive adaptive response and metabolic syndrome: challenges for the hypothesis. Trends in Endocrinology & Metabolism, 18(3), 94-99.

Discuss the trade-off between parental care and alticiality/precociality.

ANSWER: Altricial species require a higher investment in parental care than precocial species. Precocial species prioritize investment in prenatal development (eg offspring size and relative independence at birth/hatching), altricial species prioritize postnatal investment in offspring (parental care). In mammals, altricial species generally have larger litters while precocial species have few or one offspring at a time (i.e., trade-off between offspring quantity and offspring size, limited by female uterus), while in birds precocial species tend to have larger clutches (i.e., trade-off between offspring quantity and demands of parental care). 

Here you see a so-called cohort life table, in which a cohort of individuals is followed over its lifetime. Calculate: i) the net reproductive rate; ii) the geometric growth rate

The early environmental conditions can affect various classic life history traits. Life history decisions, like reproductive decisions, include the choice of a partner. Female songbirds prefer specific male songs.

Describe an experiment, which controls for other males traits, on how you can test such a preference.

The early environmental conditions can affect various classic life history traits. Life history decisions, like reproductive decisions, include the choice of a partner. Female songbirds prefer specific male songs.

QUESTION: Song of male songbirds should honestly reflect information about the male but males learn their song. Name two arguments why early nutritional conditions are expected to affect song

What is the definition of the Lack’s principle(or Lack clutch)?

I. Are clutch sizes observed in the wild usually smaller, similar or larger than the Lack clutch size? Explain why

II. Provide two reasons for the phenomenon described in question I, one focused on the parents and one focused on the offspring. Provide arguments for your answers

This figure illustrates fertility and survival as a function of age in three different species.

a. What general trend do you see in fertility and annual probability of survival in all three species?

b. What biological process do these trends describe?

c. Why are these trends considered an evolutionary puzzle?

d. Name two theories that provide a solution for this puzzle.

Considering that selection pressures drop with age, how did ageing develop in the context of life history evolution?

Many human generations ago, most women worldwide began childbearing in their mid-teens. Today, a large proportion of women worldwide delays childbearing until their 20s. Among higher-educated women in developed nations, the trend in delaying reproduction has been taken even further; with childbearing often delayed until past 30 due to education and career pressures. Suppose that the majority of women worldwide were to delay childbearing until 30, and that women were to continue to make this choice for many human generations. Make a prediction about how human lifespan and fertility might evolve in response. Give a short evolutionary explanation for your predictions on these traits.