11.1 Embryonic development

Question 1

A zygote is a ….

Answer 1

Multicellular organism (diploid cell resulting from union of 2 haploid gametes - 1st cell of next generation)

Question 2

An embryo is a…

Answer 2

Young anima or plant while still contained in protective structure (seed coat, egg shell, uterus)

Question 3

Two major processes occurring during embryonic development?

Answer 3

1. Cleavage: first cell divisions in the embryo (forming many cells from one cell)
2. Gastrulation: in-folding, invagination (forms embryonic tissue layers from first layers of cells)

Question 4

In Gastrula, the layers of embryonic cells are formed. They are called…

Answer 4

Germ layers

Question 5

Different part of germ layers?

Answer 5

1. Ectoderm (epidermis, nervous system)
2. Endoderm (lining of digestive and respiratory system)
3. Mesoderm (most internal organs: muscles, skeletal system, heart, stomach)

Question 6

Organisms with 2 germs layers are?

Answer 6

Diploblastic (ectoderm + endoderm)

Question 7

Organisms with 3 germ layers are?

Answer 7

Triploblastic

Question 8

What is called the digestive space (gut cavity) during the gastrula?

Answer 8

Archenteron

Question 9

What is called the mouth or anus during gastrula?

Answer 9

Blastopore

Question 10

Tissues enable …., while gut enables ….

Answer 10

• Complex body organization

- Extracellular digestion

Question 11

Types of symmetry?

Answer 11

1. Asymmetrical (no axis devides body into equal halves - some sponges)
2. Radially symmetrical (equal halves from many angles - cnidarians)
3. Bilaterally symmetrical (single axis, midsagittal plane)

Question 12

Development of a digestive tract enables?

Answer 12

1. Specialization of gut regions
2. Sequential food processing
3. Continuous operation

Question 13

Two ways to develop digestive tract?

Answer 13

1. Protostomes (first mouth: blastopore is the mouth, the second opening is the anus)
2. Deuterostomes (second mouth: blastospore is anus, second opening is mouth)

Question 14

Three different plans with respect to body cavities

Answer 14

1. Acoelomate
2. Pseudocoelomate
3. Coelomate

Question 15

Acoelomate

Answer 15

No body cavity (solid except digestive space)

Question 16

Pseudocoelomate

Answer 16

False coelom - mesoderm lines outside of speudocoel - nematoda

Question 17

Coelomate

Answer 17

Mesoderm lines entire cavity as ‘peritoneum’ - lining derives from mesoderm

Question 18

2 ways to make coelom

Answer 18

1. Schizocoely (splitting with mesoderm - protostomes)

2. Enterocoely (mesoderm forms pockets from gut - deuterostomes)