Fertilisation and embryonic development
Answers are for parents and teachers.
1
Compare external and internal fertilisation with one example each.
External: fish, gametes meet in water; internal: bird, fertilisation inside the body.
2
In a plant whose egg cell has n = 12, how many chromosomes does the endosperm have?
36
3
If a zygote divides 6 times in succession, how many blastomeres are there?
64
4
List in a table the organs formed from ectoderm, endoderm and mesoderm.
Ectoderm: skin, nervous system; endoderm: gut lining, liver, lung; mesoderm: muscle, skeleton, blood, heart.
5
Write the essence of embryonic induction in 2 sentences.
One part of the embryo influences other parts and sets their direction of development. Spemann’s experiments showed this.