Destroyer #219 Bio

[themrn]

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Which is false about cell cleavage?

I thought the end result of cleavage is morula. but it's actually blastula?

 

[Xo1991]

Morula becomes the blastula which becomes the gastrula.

Since blastula comes after morula, it has more cells. But the morula has larger cells since the volume doesn't increase. Also the blastula is hollow, while the morula isn't.

We see the gastrula once gastrulation occurs and the blastopore/archenteron is formed.

 

[themrn]

yap, but what's the end result of "cleavage" ??

 

[bluemoon27]

i think u have 2 clewaveges. one that forms morula, then again to form blastula. dont have my destroyer with my at the moment, but if u post a pic i can try to explain the other options.

 

[themrn]

I don't know how to put a pic on this thread so i'm just gona type it

#219

Which is false about cell cleavage?

a) Cleavage patterns vary among diff. animal groups
b) The cell is divided into smaller cells as the number of cells increase and no cell growth occurs
c) The exact cleavage pattern will depend on the amount of yolk in the egg
d) The end result of cleavage is the blastula
e) The nuclear cytoplasmic ratio of the cell decreases

The answer is (e)

During cleavage, the embryo does not grow significantly in mass, as mitosis occurs. Cleavage partitions the cell (zygote) into smaller cells. Gene transcription is shut down during cleavage, as we see an increase in cell number. Thus, the ratio of nuclear to cytoplasmic material increases.

here's what i don't understand.

1) what exactly is the ratio of nuclear to cytoplasmic material
2) i thought the end result of cleavage is the morula and it goes to blastula which don't involve cleavage

pliz help me 🙁

 

[Illfavor]

Nucleus:cytoplasm

Nuclei stay the same size, cytoplasm gets smaller, therefore the ratio increases.

 

[hope_to_match]

1. the end result of cleavage is a blastula not a morula...during cleavage the cells divide in a way that they are more and more smaller and smaller cells so there is no overall growth of the cell. there aren't two cleavages...there is only one cleavage where you go from one cell to 2 cells..4 cells...8 cells...16 cells etc and form a morula in the process...but the end result of the cleavage is a blastula..they are a bit different structures...morula is just a ball of cells..but blastula is hollow on the inside and blastula will be the one to undergo gastrulation and form 3 embryonic tissue layers+blastopore and all other funky business 🙂

2. not sure what this nuclear to cytoplasmic ratio is...can someone help us with this?

 

[hope_to_match]

Nucleus:cytoplasm

Nuclei stay the same size, cytoplasm gets smaller, therefore the ratio increases.

ohh alright that makes sense

 

[themrn]

i got it!! thank you guys!!!