One individual, however, expresses only a small number of these molecules—up to six different class I molecules and 12 or more different class II molecules.

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#XL - T Zoology

Parental investment - Parental investment refers to the contributions each sex makes in producing and rearing offspring.

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#XL - T Zoology

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#XL - T Zoology

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#XL - T Zoology

A- Parental investment is high in females than male

Reason - Eggs are much larger than sperm.

Females are responsible for gestation and lactation.

B - Parental investment is high in males than female - very rare

Male Mormon crickets transfer a protein-containing spermatophore to females during mating. Almost 30% of a male’s body weight is made up by the spermatophore.

C- Parental investment of males is equal to female

Degree of mate choice should be equal between the sexes.

No sexual dimorphism

Present in bird

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#XL - T Zoology

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#XL - T Zoology

Bateman’s principle

In most cases, it is the male’s secondary sexual traits that are exaggerated.

This shows that sexual selection is more common and intense on males than females