what is sex ratio question mark why sex ratio been unfavourable to females? Explain any eight reasons as briefly
Answers
Answer:The sex ratio is the ratio of males to females in a population. In most sexually reproducing species, the ratio tends to be 1:1. This tendency is explained by Fisher's principle.[2] For various reasons, however, many species deviate from anything like an even sex ratio, either periodically or permanently. Examples include parthenogenic species, periodically mating organisms such as aphids, some eusocial wasps such as Polistes fuscatus and Polistes exclamans, bees, ants, and termites.[3]
The human sex ratio is of particular interest to anthropologists and demographers. In human societies, however, sex ratios at birth may be considerably skewed by factors such as the age of mother at birth,[4] and by sex-selective abortion and infanticide. Exposure to pesticides and other environmental contaminants may be a significant contributing factor as well.[5] As of 2014, the global sex ratio at birth is estimated at 107 boys to 100 girls (1000 boys per 934 girls).[6]
Explanation:In most species, the sex ratio varies according to the age profile of the population.[7]
It is generally divided into four subdivisions:
primary sex ratio — ratio at fertilization
secondary sex ratio — ratio at birth
tertiary sex ratio — ratio in sexually mature organisms
Also called adult sex ratio and abbreviated to ASR. ASR is defined as the proportion of adults in a population that are male.[8]
Operational sex ratio abbreviated as OSR is the proportion of adults in the sexually active population that are males. 'OSR' has often been confused with 'ASR' although these are conceptually different.[9]
quaternary sex ratio — ratio in post-reproductive organisms
These definitions can be somewhat subjective since they lack clear boundaries.
Sex ratio theory
The theory of sex ratio is a field of study concerned with the accurate prediction of sex ratios in all sexual species, based on a consideration of their natural history. The field continues to be heavily influenced by Eric Charnov’s 1982 book, Sex Allocation.[10] He defines five major questions, both for his book and the field in general (slightly abbreviated here):
For a dioecious species, what is the equilibrium sex ratio maintained by natural selection?
For a sequential hermaphrodite, what is the equilibrium sex order and time of sex change?
For a simultaneous hermaphrodite, what is the equilibrium allocation of resources to male versus female function in each breeding season?
Under what conditions are the various states of hermaphroditism or dioecy evolutionarily stable? When is a mixture of sexual types stable?
When does selection favour the ability of an individual to alter its allocation to male versus female function, in response to particular environmental or life history situations?
Biological research mostly concerns itself with sex allocation rather than sex ratio, sex allocation denoting the allocation of energy to either sex. Common research themes are the effects of local mate and resource competition (often abbreviated LMC and LRC, respectively)
Answer:
The sex ratio is the ratio of males to females in a population. In most sexually reproducing species, the ratio tends to be 1:1. This tendency is explained by Fisher's principle.[2] For various reasons, however, many species deviate from anything like an even sex ratio, either periodically or permanently. Examples include parthenogenic species, periodically mating organisms such as aphids, some eusocial wasps such as Polistes fuscatus and Polistes exclamans, bees, ants, and termites.[3]
The human sex ratio is of particular interest to anthropologists and demographers. In human societies, however, sex ratios at birth may be considerably skewed by factors such as the age of mother at birth,[4] and by sex-selective abortion and infanticide. Exposure to pesticides and other environmental contaminants may be a significant contributing factor as well.[5] As of 2014, the global sex ratio at birth is estimated at 107 boys to 100 girls (1000 boys per 934 girls).[6]
Explanation:
In most species, the sex ratio varies according to the age profile of the population.[7]
It is generally divided into four subdivisions:
primary sex ratio — ratio at fertilization
secondary sex ratio — ratio at birth
tertiary sex ratio — ratio in sexually mature organisms
Also called adult sex ratio and abbreviated to ASR. ASR is defined as the proportion of adults in a population that are male.[8]
Operational sex ratio abbreviated as OSR is the proportion of adults in the sexually active population that are males. 'OSR' has often been confused with 'ASR' although these are conceptually different.[9]
quaternary sex ratio — ratio in post-reproductive organisms
These definitions can be somewhat subjective since they lack clear boundaries.
Sex ratio theory
The theory of sex ratio is a field of study concerned with the accurate prediction of sex ratios in all sexual species, based on a consideration of their natural history. The field continues to be heavily influenced by Eric Charnov’s 1982 book, Sex Allocation.[10] He defines five major questions, both for his book and the field in general (slightly abbreviated here):
For a dioecious species, what is the equilibrium sex ratio maintained by natural selection?
For a sequential hermaphrodite, what is the equilibrium sex order and time of sex change?
For a simultaneous hermaphrodite, what is the equilibrium allocation of resources to male versus female function in each breeding season?
Under what conditions are the various states of hermaphroditism or dioecy evolutionarily stable? When is a mixture of sexual types stable?
When does selection favour the ability of an individual to alter its allocation to male versus female function, in response to particular environmental or life history situations?
Biological research mostly concerns itself with sex allocation rather than sex ratio, sex allocation denoting the allocation of energy to either sex. Common research themes are the effects of local mate and resource competition (often abbreviated LMC and LRC, respectively)..
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