Cork Cambium

Another meristematic tissue called cork cambium or phellogen develops, usually in the cortex region

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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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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

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Bateman put several males and females together in bottles for several days. 

He concluded that the number of offspring sired by a male increased in proportion to the number of females he mated.

In contrast, the number of offspring produced by a female did not increase with the number of males she mated.