Lecture 15

Question 1

Compare the pollen grains (microgametophytes) of Gymnosperms & Angiosperms

Answer 1

• The pollen grains of angiosperms are composed of fewer cells than those of gymosperms

Question 2

Compare the ovules (location & structure) of Gymnosperms & Angiosperms

Answer 2

• In the base of the stigma/style of angiosperms
• angiosperms ovules are better protected from environment and predators
• angiosperms have 2 integuments (Inner/outer)
• ovule is in ovary

Question 3

Compare the megagametophytes (location & structure) of Gymnosperms & Angiosperms

Answer 3

• called embryo sac in angiosperms
• has only 8 nuclei within 7 cells in angiosperms
• no archegonia in angiosperms
• embryo sac is in ovule

Question 4

Draw and label an embryo sac, and explain functions of different parts

Answer 4

do this on ipad

Question 5

Discuss the formation and function of the endosperm

Answer 5

• double fert leads to production of endosperm
• pollen tube delivers 2 sperm cells into embryo sac through the synergid cells
• one sperm fertilizes egg and forms zygote
• second sperm fuses with the polar nuclei which produces a triploid nucleus, that undergoes mitotic divisions to produce endosperm

Question 6

what is endosperm?

Answer 6

food source for the embryo