Orthogenesis- “Straight-line evolution,” held that the variation that arises is directed toward fixed goals.

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#Id: 9422

#XL - T Zoology

Intrasexual selection - Members of one sex, usually males, compete over partners, and the winner performs most of the mating.

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#Id: 9423

#XL - T Zoology

Sexual dimorphism in primates

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#Id: 9424

#XL - T Zoology

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

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#Id: 9426

#XL - T Zoology

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#Id: 9427

#XL - T Zoology

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#Id: 9428

#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