Presentation 3: Development

Question 1

Types of Eggs based on yolk

Answer 1

-. Oligolecithal (Amphioxous and most mammals, very little yolk)
- Isolecithal (Very little yolk + even distribution of yolk)
- Mesolecithal (Moderate amount of yolk i.e. lampreys, amphibians)
- Telolecithal (Large amounts of yolk unevenly throughout egg i.e. most fishes, birds, reptiles, and monotremes)

Question 2

Oligolecithal

Answer 2

Type of Egg
(Amphioxous and most mammals, very little yolk)

Question 3

Isolecithal

Answer 3

Type of Egg
(Very little yolk + even distribution of yolk)

Question 4

Mesolecithal

Answer 4

Type of Egg
(Moderate amount of yolk i.e. lampreys, amphibians)

Question 5

Telolecithal

Answer 5

Type of Egg
(Large amounts of yolk unevenly throughout egg i.e. most fishes, birds, reptiles, and monotremes)

Question 6

Types of Cleavage Division

Answer 6

Holoblastic (Oligolecithal eggs, complete division, equal sized blastomeres)
Meroblastic (telolecithal eggs limited cleavage to animal pole, unequal sized blastomere)

Question 7

Holoblastic

Answer 7

Type of cleavage
Eggs with little or no yolk (i.e. Oligolecithal or isolecithal eggs, total cleavage, equal sized blastomeres)
Ex. amphioxous and most mammals

Question 8

Meroblastic

Answer 8

Type of Cleavage
Eggs w/ large amounts of yolk (embryo forms thin cap on yolk), telolecithal eggs, cleavage limited to animal pole, unequal sized blastomere)
Ex. most birds, reptiles, and egg laying mammals

Question 9

Steps of Embryo Development

Answer 9

1. Fertilization (result in zygote)
2. Morulation = Morula (no inner cavity)
3. Blastulation = Blastula (layer of cells surrounding blastocoel / inner cavity)
4. Gastrulation => Gastrula (primary germ layers form from blastopore)

Question 10

Primary Germ Layers

Answer 10

Ectoderm, mesoderm, endoderm

Question 11

Gastrulation in Oligolecithal

Answer 11

Invagination (blastopore invaginates endoderm cells which form a cavity called an archenteron)

Question 12

Archenteron

Answer 12

inner cavity that occurs during gastrulation

Question 13

Gastrulation in Telolecithal eggs

Answer 13

Epiboly and Involution (blastoderm spreads during epiboly and is then involuted at blastopor and folds upwards along edge to form archenteron

Question 14

Coelom Formation

Answer 14

Telolecithal = Schizocoelous (cavitization of mesoderm)
Oligolecithal = Enterocoely (outpocketings of archenteron

Question 15

Coelom

Answer 15

cavities in mesoderm

Question 16

Protostomes vs Deuterostomes gastrulation

Answer 16

Protostomes: blastopore becomes mouth, schizocoelous formation

Deuterostomes: blastopore becomes anus, enterocoelous

Question 17

Neurulation

Answer 17

Induction of neural tissue
1. Thickening and elongation (neural plate formation with adjacent neural crest and epidermis)
2. Folding (neural crest/groove formation)
3. Convergence (dorsal hinge points fold to produce a tube like structure
4. Fusion (neural tube formed by dorsal most cells on each side of neural tube begin to fuse as well as epidermis
4. Neural crest cells migrate away as fusion is complete

Question 18

Cleidoic Egg / Amniotic Egg

Answer 18

Chorion, amnion, embryo, allantois, and yolk sac.

Question 19

Chorion

Answer 19

Outermost part of Amniotic egg

Question 20

Amnion

Answer 20

Membrane surrounding fetus

Question 21

Allantois

Answer 21

More posterior side of embryo - accumulates waste

Question 22

Yolk Sac

Answer 22

More anterior side of embryo, provides nutrients

Question 23

Mammal Amniotic Egg

Answer 23

Chorion combines w/ uteran wall to form placenta and provide embryo w/ extra nutrients and oxygen.
Umbilical cord wraps around membranes

Question 24

Phylogeny

Answer 24

Evolutionary history of a species

Question 25

Ontogony

Answer 25

Lifespan of a single individual

Question 26

Von Baer’s Laws

Answer 26

1. Gen. characters appear before specialized characters
2. from gen. characters specialized characters develop
3. during development, animal departs from form of others
4. Early stages of development in an animal are not like adult stages of other animals, stages do resemble younger stages of animal in lower part of ‘great chain of being’