3. look at the illustration in figure 25-2. which letter points to the endoderm
1.a
2.b
3.c
4.d

4. the difference between a prostone and a deuterostome is that
1. a deuterostome only has to germ layers
2. a protostome always develops into an acoelomate
3. the blastopore in a deuterostome develops into the animals anus
4. only prostomes can develop into radially symmetrical adults.

5. which of the following is a fertilized egg?
1. a blastula
2. a zygote
3. a blastophere
4. a pseudocoelom

lol

3. The correct answer is C. Endoderm refers to one of the three primary germ layers found in the initial phase of an embryo. The endoderm is the innermost layer. The cells going inwards along the archenteron produce the inner layer of the gastrula that forms into endoderm.  

4. The correct answer is 3. The blastopore in a deuterostome develops into the animal's anus.  

5. The correct answer is 2. A zygote refers to an amalgamation of a sperm cell and the egg cell. It is also called fertilized ovum, the zygote starts as a single cell, and however, it differentiates briskly in the days after fertilization.