Evolution and Life History Lecture BIO 4083

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Questions and Answers

What type of selection is described in the text?

Sexual selection

Frequency-dependent selection (correct)

Natural selection

Artificial selection

In genomic imprinting, gene expression is silenced by:

Both parents

Methylation by one parent (correct)

Offspring

Environmental factors

In hybrid inviability between a male donkey and female horse, the offspring may result in:

Liger

Hinny (correct)

Mule

Zebroid

What is the phenomenon where offspring express either the maternal or paternal copy of a gene, but not both?

Genomic imprinting Signup and view all the answers

Which of the following terms refers to heritable changes in gene expression possibly due to an individual's lifetime experiences?

Epigenetics Signup and view all the answers

What are mules and hinnies?

Both hybrids of horses and donkeys Signup and view all the answers

Females may alter sex ratios of offspring depending on their condition as proposed by the Trivers-Willard ______

hypothesis Signup and view all the answers

Organisms may regulate the number of offspring to maximize fitness through mechanisms like ______

miscarriage Signup and view all the answers

Siblings may compete for parental investment, leading to potential conflicts over ______

care Signup and view all the answers

In the context of parental care, the balance between leaving the nest earliest and the risk of offspring mortality is a trade-off in terms of ______

risk Signup and view all the answers

Some organisms may cannibalize eggs or offspring to ensure the ultimate goal of higher fitness and survival in the ______

offspring Signup and view all the answers

What aspect of life history traits involves an organism's age when it first reproduces?

The duration and schedule of reproduction Signup and view all the answers

What is a possible trade-off for organisms living longer according to the text?

Producing fewer offspring Signup and view all the answers

What is the primary factor that natural selection optimizes life history in light of?

Trade-offs between survival, maintenance, and reproduction Signup and view all the answers

Which of the following best describes a life history strategy involving continually reproducing over a long life?

Continually reproducing over a long life Signup and view all the answers

In terms of life history traits, what does having a limited amount of energy to invest result in?

Trade-offs between survival, maintenance, and reproduction Signup and view all the answers

What is a common outcome of different species having varying life history traits?

Wide variation in reproduction patterns Signup and view all the answers

What is the main driving factor of life history evolution in guppies according to the text?

More offspring Signup and view all the answers

In the context of parental investment, which sex is more likely to provide care according to the text?

Females Signup and view all the answers

What does the trade-off between reproduction and growth/survival reveal in guppies?

A visible link during an individual's lifetime Signup and view all the answers

In species where sex role reversal occurs, what behavior is observed in male jacanas compared to females?

Incubate eggs and protect chicks Signup and view all the answers

What is the operational sex ratio (OSR) in jacanas based on the provided information?

More males than females Signup and view all the answers

Why is mate choice important in male pipefishes as mentioned in the text?

To compete with other males for mates Signup and view all the answers

Why do females adjust the sex ratio of offspring according to the Trivers-Willard hypothesis?

To maximize the fitness of their offspring based on environmental conditions Signup and view all the answers

In the context of parental care, what is the primary downside of leaving the nest too early?

Increased risk of predation on offspring Signup and view all the answers

How do barn swallows adjust numbers and sex ratios of offspring to maximize fitness?

By increasing the number of females in good conditions Signup and view all the answers

What is a common strategy used by some organisms to regulate the number of offspring produced?

Practicing cannibalism on weaker offspring Signup and view all the answers

Why might females produce more males when in good condition according to the Trivers-Willard hypothesis?

Because males are more likely to attract mates when large Signup and view all the answers

What is the primary reason behind organisms regulating the sex ratios of offspring?

To maximize the fitness and survival of offspring Signup and view all the answers

What is a possible mechanism responsible for the difference in sex ratio adjustment between birds and mammals?

Some species switch sex in a 'Trivers-Willard-predicted' manner Signup and view all the answers

Why do birds and mammals differ in their sex ratio adjustment mechanisms?

Some species switch sex in a 'Trivers-Willard-predicted' manner Signup and view all the answers

What is a possible benefit of females favoring daughters under high resources in Seychelles warblers?

Functionally equivalent to haplodiploidy Signup and view all the answers

What leads to the prediction of sex role reversal in Bluestreak cleaner wrasse according to cost-benefits analysis?

They start as females when young, then switch to males when large Signup and view all the answers

What is a potential outcome for species with sex ratios often balanced according to life history theory?

The ultimate goal of higher fitness and survival Signup and view all the answers

In the context of parental investment, what trade-off may occur between offspring mortality risk and leaving the nest earliest?

The trade-off between offspring mortality risk and leaving the nest earliest Signup and view all the answers

What is the term for the phenomenon where offspring express either the maternal or paternal copy of a gene, but not both?

Genomic imprinting Signup and view all the answers

In the context of parental investment, what are mules and hinnies?

Species resulting from male horse x female donkey mating Signup and view all the answers

What type of selection might lead to conflicts between sexes within the genome?

Frequency-dependent selection Signup and view all the answers

What is the term for heritable changes in gene expression possibly due to an individual's lifetime experiences?

Lamarckism Signup and view all the answers

In terms of trade-offs in life history traits, what might influence the balance between leaving the nest earliest and offspring mortality?

Predation risk Signup and view all the answers

Which phenomenon can lead to male donkey x female horse hybrids being different species depending on the father's species?

Genomic imprinting Signup and view all the answers

What are some examples of life history traits mentioned in the text?

An organism’s age at first reproduction, the duration and schedule of reproduction, the number and size of offspring produced, and life span. Signup and view all the answers

What do life history traits involve according to the text?

Trade-offs between survival, maintenance, and reproduction. Signup and view all the answers

What is the main focus of natural selection in optimizing life history traits?

Maximizing the number of offspring surviving to maturity. Signup and view all the answers

What is a potential trade-off for organisms living longer according to the text?

Having fewer offspring. Signup and view all the answers

What type of traits vary widely among different species?

Life history traits. Signup and view all the answers

What drives life history evolution in guppies?

Predation risk Signup and view all the answers

In the context of parental investment, which sex is more likely to provide care?

Females Signup and view all the answers

What is the primary factor that natural selection optimizes life history in light of?

Reproductive success Signup and view all the answers

What trade-off can be visible during the lifetime of an individual in guppies?

Reproduction and growth/survival Signup and view all the answers

What is the operational sex ratio (OSR) in jacanas based on the provided information?

Up to 2.22 females to 1 male Signup and view all the answers

What is the Trivers-Willard hypothesis regarding sex ratios of offspring?

Mothers alter sex ratios depending on conditions Signup and view all the answers

How do organisms regulate the number of offspring to maximize fitness?

Adjusting numbers and sex ratios of offspring Signup and view all the answers

What is the term for the balance between leaving the nest earliest and the risk of offspring mortality?

Trade-off in terms of offspring mortality risk and leaving the nest earliest Signup and view all the answers

Why might females produce more males when in good condition according to the Trivers-Willard hypothesis?

Males likely benefit more from being large and attract mates more readily Signup and view all the answers

Which phenomenon can lead to conflicts over parental investment among siblings?

Siblings competing for parental investment Signup and view all the answers

Why do females in Seychelles warblers favor daughters under high resources?

Daughters can help raise more offspring, which is beneficial. Signup and view all the answers

What is a possible mechanism responsible for the difference in sex ratio adjustment between birds and mammals?

Some species switch sex in a 'Trivers-Willard-predicted' manner. Signup and view all the answers

Why are sex ratios often balanced?

To maximize fitness through mechanisms like parental investment. Signup and view all the answers

What might influence the balance between leaving the nest earliest and offspring mortality in terms of trade-offs in life history traits?

Parental care. Signup and view all the answers

What aspect of life history traits involves an organism's age when it first reproduces?

The age of first reproduction. Signup and view all the answers

Study Notes

Life History Traits

Life history traits include an organism's age at first reproduction, the duration and schedule of reproduction, the number and size of offspring produced, and life span.
Life history traits vary widely among different species.
Examples:
- Short life, many eggs: reproduce once in a short life.
- Long life, fewer offspring: continually reproduce over a long life.

Evolution of Life History Traits

Life history traits involve trade-offs between survival, maintenance, and reproduction.
Natural selection optimizes life history in light of trade-offs.
Goal: maximize number of offspring surviving to maturity.
Depends on likelihood of survival to different age classes.

Data from Opossums

Supports predictions from life history theory.
Sapelo Island, GA: no predators, island opossums live longer, have fewer offspring.
But what could be a trade-off for living longer?

Parental Investment

Females are more likely than males to provide parental care.
Males have less investment, uncertain paternity.
Roles are reversed in some species.

Operational Sex Ratio (OSR)

Sexual selection becomes an important agent when members of one sex compete with each other to mate.
Sex role reversal in jacanas: males incubate eggs and protect chicks, females guard harems of males and are larger.
OSR is male-biased (up to 2.22 F:1 M).

Conflict in Life History Traits

Conflict between parents: conflict over parental care.
Strategies to maximize offspring produced over a lifetime can differ for the sexes.
Balance between leaving the nest earliest (don't have to care for the offspring), but too early is risk (offspring can die).
Competition among siblings: siblings may compete for parental investment.

Adjusting Numbers and Sex Ratios of Offspring

Organisms may regulate the number of offspring to maximize fitness.
Miscarriage, cannibalism.
Trivers-Willard hypothesis: mothers alter sex ratios depending on conditions.
Produce females when in poor condition; daughters will likely have some offspring even if in poor condition.
Produce males when in good condition; males likely to benefit more from being large and will more readily attract mates.

Sex Ratio Adjustment

In Seychelles warblers, with high resources, females are favored, daughters can help raise more offspring = beneficial.
With low resources, males are favored, disperse away from poor habitat.
This type of sex ratio adjustment from mothers seems to be rare in mammals.

Haplodiploidy

Fig wasp: females alter sex ratios of offspring.
Thrips are haplodiploid too.
Sex ratio controlled by Wolbachia bacteria.
Sex ratios controlled by unique genetic elements in some species of booklice.

Genomic Imprinting and Parental Conflict

Gene expression silenced by methylation by one parent.
Offspring express either maternal or paternal copy of gene, but not both.
Example: mules and hinnies (hybrids of horses and donkeys, but different species is the father).
Differences in phenotype linked to genomic imprinting.
Epigenetics: heritable changes in gene expression (perhaps accrued during the individual's lifetime: behavior and environment).

Please note that the formatting might not be perfect due to the text formatting limitations.### Antagonistic Pleiotropy

Island opossums on Sapelo Island, GA, with no predators, live longer and have fewer offspring.
Predation risk drives life history evolution in guppies, resulting in more offspring, lower weight, and younger reproductive age in high-predation environments.

Life History Traits

Transplant experiments demonstrate rapid evolution of life history traits, such as trade-offs between reproduction and growth/survival.
Brown anolis lizards: removing ovaries led to larger females, highlighting the trade-off between reproductive investment and growth.

Parental Investment

Females are more likely to provide parental care, while males have less investment due to uncertain paternity.
These roles are reversed in some species, such as jacanas and pipefishes.

Operational Sex Ratio (OSR)

Sexual selection becomes an important agent when members of one sex compete with each other to mate.
In jacanas, OSR is female-biased, with up to 2.22 F:1 M, due to males incubating eggs and protecting chicks.

Sex Role Reversal

In jacanas and pipefishes, males make greater parental investment, leading to "male choice" and sex role reversal.
In pipefishes, males compete for mates, and mate choice is important.

Competition and Parental Care

Parents may compete for parental care, with strategies to maximize offspring produced over a lifetime differing between sexes.
Balance is needed between leaving the nest early and ensuring offspring survival.

Competition among Siblings

Siblings may compete for parental investment, with adjustments to numbers and sex ratios of offspring to maximize fitness.

Trivers-Willard Hypothesis

Mothers may alter sex ratios depending on conditions, producing females when in poor condition and males when in good condition.
This hypothesis is supported by evidence from various species, including Seychelles warblers.

Sex Ratio Adjustment

Some organisms, such as fig wasps and thrips, can adjust sex ratios of offspring through haplodiploidy (arrhenotoky).
In Seychelles warblers, females favor daughters when resources are high and males when resources are low.

Mechanisms of Sex Ratio Adjustment

In some species, sex ratios are controlled by unique genetic elements, such as Wolbachia bacteria in certain species of booklice.
Paternal genome elimination, or pseudo-arrhenotoky, is functionally equivalent to haplodiploidy in some species.

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Description

Explore the evolution of life history traits, parental investment, sex ratios, and life history strategies in this lecture. Learn about the patterns of investment in growth and reproduction, age at first reproduction, reproduction schedule, offspring size and number, and lifespan.