Which among the following produce seeds?

The 'Origin of Species' was written by:

Identify the phylum for the following characteristics given:
$(a)$ Organisms with jointed appendages.
$(b)$ Organisms are generally flatworms.
$(c)$ Body is segmented.
$(d)$ Skin of organisms is full of spikes.

Which of the following features is not a characteristic of $Protochordata$?

State whether the following statement is true or false:
Gymnosperms are usually perennial,evergreen,and woody.

Give reasons for the following:
$(a)$ Echidna and Platypus lay eggs but are considered as mammals.
$(b)$ Birds have pneumatic bones.