embryology

Question 1

embryogenesis

Answer 1

fertilised egg or oocyte

morula - solid ball of cells

blastula - hollow ball of cells around a blastocoel

gastrula - multi layered ball of cells

Question 2

morulation

Answer 2

formation of morula - solid ball of cells
cell cleavage - spiral or radial

stops for basal metazoans

Question 3

blasulation

Answer 3

formation of blastula

hollow ball of cells around a blastocoel

Question 4

gastrulation

Answer 4

formation of gastrula
formation of germ cell layers
formation of the mesoderm and the coelom

Question 5

radial cleavage

Answer 5

blastomeres arranged directly above or below each other

cells appear above or below where they came form

Question 6

spiral cleavage

Answer 6

blastomeres arranged in a spiral pattern around the embryos axis

half twist creates spiral view

Question 7

importance of the type of cleavage

Answer 7

affects how cells form in morula
therefore affects how they appear in blastula and gastrula

Question 8

Haeckel

Answer 8

development of the embryo mirrors the successive stages of evolution
- ontology recapitulates phylogeny

things evolved from each other have similar embryos
but over represented the biological significance of features in diagrams

Question 9

recapitulation theory

Answer 9

evolutionary development biology
changes in the timing and positioning of embryonic development affects the change of the shape of a descendants body compared to it ancestor

embryos do reflect evolution but not in way Haeckel suggested