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Skeletons of female (left) and Male (right) black-casqued hornbills (Ceratogymna atrata). The difference between the sexes is apparent in the casque on the top of their bill. This pair is on display at the Museum of Osteology. Sexual dimorphism may also influence differences in parental investment during times of food scarcity.
The human brain. Differences in male and female brain size are relative to body size. [83] Early research into the differences between male and female brains showed that male brains are, on average, larger than female brains. This research was frequently cited to support the assertion that women are less intelligent than men.
In some rodents, males are larger than females, while in others the reverse is true. Male-bias sexual dimorphism is typical for ground squirrels, kangaroo rats, solitary mole rats and pocket gophers; it likely developed due to sexual selection and greater male–male combat. Female-bias sexual dimorphism exists among chipmunks and jumping mice.
The cheek pouch is a specific morphological feature that is evident in particular subgroups of rodents (e.g. Heteromyidae and Geomyidae, or gopher), yet a common misconception is that certain families, such as Muridae (including the common black and brown rats), contain this structure when in fact their cheeks are merely elastic due to a high ...
The smaller gamete is male, a sperm cell, whereas the larger gamete is female, typically an egg cell. Anisogamy is predominant among multicellular organisms. [1] In both plants and animals, gamete size difference is the fundamental difference between females and males. [2] Anisogamy most likely evolved from isogamy. [3]
A female produces an ovum with a full set (two sets of genes) provided solely by the mother. Thus, a male is not needed to provide sperm to fertilize the egg. This form of asexual reproduction is thought in some cases to be a serious threat to biodiversity for the subsequent lack of gene variation and potentially decreased fitness of the offspring.
Rats such as the bandicoot rat (Bandicota bengalensis) are murine rodents related to true rats but are not members of the genus Rattus. [4] [5] Male rats are called bucks; unmated females, does, pregnant or parent females, dams; and infants, kittens or pups. A group of rats is referred to as a mischief. [6]
One difference between the glans penis and the glans clitoridis is that the glans clitoridis packs nerve endings into a volume only about one-tenth the size of the glans penis. Therefore, the glans clitoridis has greater variability in cutaneous corpuscular receptor density (1-14 per 100× high-powered field) compared with the glans penis (1-3 ...