<u>Answer:</u>
Recent evidence suggest that feathers evolved from scales and suggest that 'feathers and pycnofibers' could be homologous.
<u>Explanation:</u>
- One of the major difficult issue related to bird evolution is the evolution of feathers.
- Feathers are considered as the most 'complex integumentary structures' which are found in vertebrates.
- Evolutionary developmental biology suggests that the 'planar scale structure' is been modified for developing into feathers by 'splitting' to form web like structures.
- Scales and Feathers consist of 'two distinct form of keratin' so it was thought that 'each type was exclusive skin structure' but recent study suggests that they are developmental expressions of same skin structures.
Answer: It is because it makes it more efficient to study organisms.
Explanation: Biologist classify organisms by considering similarities between them. The organisms which have closely related characteristics are placed in a separate domains by biologists. Domains are further divided into 6 Kingdoms. According to modern classification system, domain is largest unit of biological classification.
Answer:
gymnosperms produce male cones and female cones, and the pollen from a male cone fertilize the egg inside a female cone
