Question

In black Swan, invariable cross-fertilization takes place.
(a) True
(b) False

Answer 1

Hint: The black swans are big waterbirds, which are a species of Cygnus that is commonly found in the river banks and near other water bodies of Australia. Black swans migrate and breed within Australia depending on the climatic changes.

Complete answer:
The statement is false, because, In the black swan’s population, twenty-five percent of the males show bisexual characteristics. They are also known for having intercourse with more than one pair at the same time with the involvement of both the sex. Therefore black swans don’t involve in invariable cross-fertilization.

Additional information:
- Black swans are huge birds that are black in color and have bills that are red in color. They are commonly monogamous partners, where both partners share the duties of taking care of the progeny.
- Currently, black swans are present in different countries as they are grown as ornamental birds. The trading of black swans was common in the 1800s.
- A small group of black swans live as wild swans on the River Thames at Marlow and the River Itchen, but the majority of the wild black swans don’t exist now, due to human hunting.
So, the correct answer is 'False'.

Note:
- Even though the Black swans are majority black- feathered birds, the flight feathers are white in color. They have legs which are grey in color and help in swimming.
- The males are larger than females and are known as Cobs and Pens respectively. The immature birds are not completely black but have slight grey color, and are called Cygnets.
- Adult black swans have an average length of 145 centimeters and an average weight range of 3.5 to 9.5 kilograms. They have an 'S' shaped neck and an average wing length of 2 meters.