In humans, females inherit an x chromosome from each parent; males inherit their x chromosome from their mother and their y chromosome from their father. the same is true of all other placental mammals: males produce x and y gametes, and females produce only x gametes. in this system, referred to as the xx-xy system, maleness is determined by sperm cells that carry the y chromosome. yet the xx-xy sex determination system does not occur in all animal species. it is only one of a variety of systems within the animal kingdom. above are punnett squares illustrating three examples of gender inheritance patterns: humans, insects and birds. consider both the illustration and the text. compare the inheritance system of bird with that of humans.

In bird, females are heterogametic, produce two type of gametes. The two different sex chromosomes of a female bird has been designated to be the Z and W chromosomes. Whereas males have a pair of Z- sex chromosomes. Males are homogametic produce only one type of gametes with Z-sex chromosomes. Thus sex determination is ZW-ZZ type. In humans sex determination is XX-XY type. Males are heterogametic produce X and Y gametes and females are homogametic produce one type of gametes. Therefore, in bird sex are determined by female gametes.  

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the water molecules are transferred from the roots to the stem or top parts of the tall tree because of important properties of water which are adhesion, cohesion and capillary action. cohesion is the property of water molecules keeps water molecules in a combined state by sharing of bonds between them at the atomic level. adhesion allows the interaction of water molecules with other substances or substrate. adhesion will cause the attachment of water molecules to the wall of the vessel (xylem) of the plant. capillary action occurs when the adhesive force to the vessel wall is stronger than the cohesive force between water molecules. capillary action mimics the transfer of water from a tube or pipe. in this way water utilizes its property to transfer water from down to top level of the plant.  

all matter is made up of atoms

in any element all atoms are the same

elements in a compound are always in a constant ratio: apex