Ch. 8 Development

Question 1

Explain how the concept of epigenesis differs from preformation

Answer 1

mini adult in sperm/egg vs fertilized egg has building materials and it develops

Question 2

Understand why development is an irreversible process

Answer 2

series of progressive changes

Question 3

Explain what role fertilization plays in development

Answer 3

first development event

union of m and f gametes
restores diploid number
activates egg

Question 4

Describe how marine organisms with external fertilization ensure successful fertilization

Answer 4

eggs have chemotactic factor (attracts sperm of correct species)

Question 5

Understand how development patterns are related to the classification of animal phyla

Answer 5

nuclear fusion
fast in sea urchins 12 min, slow in mammals 12 hours

Question 5

Explain how organisms prevent polyspermy and why this is important

Answer 5

changes cell membrane:
fast block - electrical potential change
creates fertilization membrane

Question 6

Distinguish between a blind gut and a complete gut

Answer 6

blind - dipoblastic - 2 germ layer (ecto and endoderm)

complete - tripoblastic - 3 germ layer (+mesoderm) formation of coelom (mesoderm surrounds)

Question 7

Explain what happens during the processes of blastulation and gastrulation

Answer 7

embryo divides repeatedly -> makes blastomeres
(little vs much yolk indirect vs direct development)
cleavage: blastula with blastocoel cavity
(one layer)

one side of blastula caves in -> archenteron (new cavity) with blastopore opening
(2 layer)
ecto and endoderm
if you stop here its incomplete/blind gut

Question 8

Distinguish between organisms with 1, 2, or 3 germ layers

Answer 8

1 layer - sponges
2 layer - sea anemone , flatworms
3 - everyone else

Question 9

Understand the difference between protostomes and deuterostomes (there are 4 developmental characters) and be able to list some example of organisms in each category

Answer 9

protostomes (lophotrochozoans and ecdysozoans)
spiral cleavage, mosaic development, blastopore becomes mouth, form coelom via schizocoely

deuterostomes (echinoderms, hermichordates, chordates)
radial cleavage, regulative development, blastopore becomes anus, forms coelom via enterocoely

Question 10

Explain the concept of nuclear equivalence and how, despite this equivalence, cells are able to differentiate themselves

Answer 10

every blastomere has same genetic information

cytoplasmic specification - cells inherit some parts of egg’s cytoplasm

embryonic induction - cells affected by nearby cells

Question 11

Explain what role homeotic genes play in development

Answer 11

segment specific genes , regulate gene expression in that segment

Question 12

Be able to list the three general stages of development

Answer 12

1. pattern formation
2. determination of position in body
3. induction of limbs and organs

Question 13

Describe what chordate characteristics vertebrate embryos share (5)

Answer 13

-dorsal neural tube
-notochord
-pharyngeal gill pouches
-ventral heart
-postanal tail