Familiarity with Developmental Characters and Terms

Question 1

what happens after the zygote is formed? (sperm fertilizes egg)

Answer 1

embryonic development begins

1. there are 2, 4, and 8 cell stages
2. morula (solid ball of cells) is formed
3. blastula (hollow ball of cells)
4. cleavage ends
5. at the blastopore, wall of cells turn inward forming an internal cavity called the archenteron

Question 2

what does the blastopore become in protostomes?

Answer 2

the mouth

Question 3

what does the blastopore become in deuterostomes?

Answer 3

the anus

Question 4

what are germ layers?

Answer 4

embryonic layers that give rise to new tissues and ultimately organs

Question 5

what are diploblastic animals?

Answer 5

they have 2 germ layers

ectoderm and endoderm

Question 6

what are triploblastic animals?

Answer 6

have 3 germ layers

ectoderm, mesoderm, endoderm

Question 7

what is ectoderm?

Answer 7

• outermost layer in the embryo

- gives rise to the outer body (epidermis) and in some cases the nervous system

Question 8

what is endoderm?

Answer 8

innermost layer in the embryo

-gives rise to digestive tract and associated internal organs

Question 9

what is mesoderm?

Answer 9

middle layer in the embryo

• gives rise to muscles, circulatory + excretory systems, and gonads
• tissues from mesoderm also line the coelum

Question 10

definition of a tissue

Answer 10

groups of one or more types of cells which perform a specific function

Question 11

what are the main categories of tissues?

Answer 11

epithelial
muscular
connective
nervous

Question 12

what is the coelum?

Answer 12

fluid-filled body cavity between the digestive tract and the outer body wall

• lined by mesoderm derived tissues
• ONLY triploblastic animals can have a coelum

Question 13

what is a pseudocoelomate?

Answer 13

(ex. roundworms, nematodes) have an inlined body cavity called a “pseudocoel” lies between their gut and outer body wall

Question 14

what is a true coelomate?

Answer 14

(ex. all vertebrates, annelids) have a coelum, body cavity lined with peritoneum which is derived from mesoderm tissue
- cushions and protects internal organs, allows them to move more independently

Question 15

what is an acoelomate?

Answer 15

(ex. flatworm) do not have a body cavity

- region between gut and body wall is filled with tissues

Question 16

what two types of symmetry can animals have?

Answer 16

asymmetry 
symmetry (radial or bilateral)

Question 17

what are radially symmetrical animals?

Answer 17

• tend to be circular or cylindrical
• can be divided into two equal halves by many planes
  (ex. hydra)
• usually have a nerve net

Question 18

what are bilaterally symmetrical animals?

Answer 18

can only be divided by one body plane (midsaggital)

- results in right and left halves
ex. frog

Question 19

define cephalization

Answer 19

refers to the concentration of sensory and nervous structures primarily at the anterior end of the body (formation of eye spots, antennae, eyes, brain, etc.)
-it is possible that an animal can be cephalized but not posses a head

Question 20

define segmentation

Answer 20

refers to the presence of repeated body segments as well an internal/external structures attached to these segments
-can provide greater support and specialization

Question 21

what is the “complete digestive tract”?

Answer 21

refers to the alimentary canal

-long tube with two separate openings (mouth and anus)

Question 22

what is an articulated limb?

Answer 22

refers to legs with joints
allows for greater range of coordinated movement
-these appendages are paired