1. Chapter 24
Development

2. Fertilization and the Stages of Mitosis

3. What is embryonic Development?
Do Now:
What is embryonic Development?

4. (I) Embryonic Development
In the early stages of development, the organism is called an embryo
The process of embryonic development includes:
1. Cleavage
2. Gastrulation
3. Differentiation

5. (A) Cleavage
Cleavage is a series of mitotic divisions where the cell increases in cell number but NOT in cell size
Cleavage converts a single fertilized egg (zygote) into many cells

6. As cleavage continues, the cells form a hollow ball-type structure filled with fluid. At this point, the embryo is called a blastula

7. Stages of Development (Cleavage)
Zygote cells cells cells Morula Blastula
Gastrula
2 layers layer

8. Stages of Development (Cleavage)

9. (B) Gastrulation
When the blastula reaches several hundred cells, gastrulation occurs
In this stage, the cells on one side of the blastula push in and form a two-layered embryo called the gastrula

10. Gastrula The gastrula consists of 3 layers:
a) endoderm – inner layer of cells
b) mesoderm –middle layer of cells
c) ectoderm - outer layer of cells

11. (C) Differentiation
Differentiation- series of changes that transform the unspecialized embryonic cells into specialized cells, tissues and organs

12. Ectoderm Mesoderm Endoderm
It is the three germ layers that give rise to all the tissues and organs of an animal
Ectoderm
Mesoderm
Endoderm
Nervous system
Digestive System
lining of mouth, nostrils, and anus
epidermis of skin, sweat glands, hair, and nails
bones and muscles
blood and blood vessels
reproductive and excretory system
dermis layer of skin
lining of digestive tract
lining of trachea, bronchi, and lungs
liver, pancreas
thyroid, parathyroid
urinary bladder

13. (C) Growth and Differentiation
Differentiation- series of changes that transform the unspecialized embryonic cells into specialized cells, tissues and organs
Growth- mot only are the number of cells increasing, but the size of the cells are increasing as well, and the embryo as a whole starts to develop

14. Farmer Andy

15. Two types of Development
What are the 2 major types of development?
Provide organisms that represent each.

16. Two types of Development
External Development
Fish, amphibians, reptiles, birds
Internal Development
Mammals
and their is a Lack of Development !

17. Farmer Andy

18. External Development

19. External Development

21. External Development

22. (B) Internal Development
Development occurs inside the female
Three types:
Placental mammals
Marsupials
Monotremes
To be covered later

23. Egg Development What is the difference between these two eggs?

24. Chicken Reproductive System
The ovaries appear like a bunch of grapes and in an adult will contain five to six developing egg yolks.
The oviduct is divided into five regions:
funnel or infundibulum, magnum where albumen is secreted,
isthmus which secretes the shell membranes,
uterus or shell gland,
the vagina which connects to the cloaca.
Chicken eggs are incubated about 21 days before hatching.

25. Chicken Reproductive System

26. Structure of Egg chorion- outer-most membrane, aids in gas exchange
Consists of 4 membranes outside of the embryo
chorion- outer-most membrane, aids in gas exchange
allantois- exchange of O2 and CO2. Also a storage site for wastes
amnion- sac containing amniotic fluid which surround the embryo, provides cushion and acts as a shock absorber
yolk sac- source of food for the embryo. Blood vessels in the yolk sac transport food to the developing embryo

27. Structure of Egg chorion- outer-most membrane, aids in gas exchange
Consists of 4 membranes outside of the embryo
chorion- outer-most membrane, aids in gas exchange
allantois- exchange of O2 and CO2. Also a storage site for wastes
amnion- sac containing amniotic fluid which surround the embryo, provides cushion and acts as a shock absorber
yolk sac- source of food for the embryo. Blood vessels in the yolk sac transport food to the developing embryo

28. Structure of Egg chorion- outer-most membrane, aids in gas exchange
Consists of 4 membranes outside of the embryo
chorion- outer-most membrane, aids in gas exchange
allantois- exchange of O2 and CO2. Also a storage site for wastes
amnion- sac containing amniotic fluid which surround the embryo, provides cushion and acts as a shock absorber
yolk sac- source of food for the embryo. Blood vessels in the yolk sac transport food to the developing embryo
Embryo

29. “Chicken Egg” germinal disc yolk chalaza shell inner shell membrane
outer shell membrane
air cell yolk membranes
outer layer of thin albumen
dense albumen
inner layer of thin albumen
chalaziferous layer
“Chicken Egg”

30. Fertilization
                                                                
In the infertile egg, on the left, the nucleus is merely a light spot on the yolk. The egg on the right is fertilized. In the fertilized egg the ovum has fused with a sperm to begin forming an embryo. By the time the fertilized egg is laid, many cells are divided on the surface of the yolk and formed a blastoderm. Can you see the difference between the nucleus of the infertile egg and the blastoderm of the fertilized egg? Both are indicated by the blue arrow.

31. Day 1
                                                                
After one day in the incubator, the small white spot seen in the fertilized egg above has grown to the size of a nickel or a quarter.

32. Day 2
By 24 hours, pockets of blood cells and developing blood vessels, called blood islands, begin to appear on the surface of the yolk along the outer edges of the area opaca. These are called the vitelline vessels. At the same time, the heart and vessels within the chick embryo have begun to develop.
                                                              

33. Day 3
The embryo is the question mark shape in the center of the image. It has grown considerably since yesterday and the anterior half of its body is curved even more. The heart, located inside the anterior curve of the body is much larger and more developed than in yesterday's photograph.
                                                              

34. At four days, nearly the entire body of the embryo has risen off the yolk and turned to lay on its left side. The upper portion of the embryo is even more curved and the tail is also beginning to curve. The heart is the dark red area within the upper curve of the embryo. Just a fraction of an inch from the heart, the eye is visible. The large node just above and to the right of the eye is a portion of the brain.
Day 4
                                                                

35. Day 5
                                                                  
Yolk
Eye of embryo
Albumen

36. Day 6
                                                         
Yolk
Air space
Eye of embryo
Blood vessels

37. Day 7 A row of feather germs appears on the tail.
The sclera of the eye begins to form.
Feather papillae appear on the thigh.
The leg bends at the knee.
Day 7
                                                
              

38. Day 8

39. Day 9

41. Welcome into the World

42. Hello World

43. I feel so naked

44. Hatching takes a lot out of You

45. 1 hour

46. 1 hour

47. 20 Hours Old and they sleep like teenagers

48. 22 hours

49. Left-Overs aren't always good

50. Do Now 4/28
What are the four membranes found in the adaptation for external development??

51. (B) Internal Development
Development occurs inside the female
Three types:
Marsupials
Monotremes
Placental mammals

52. Marsupials Are mammals that do not have a placenta
The embryo is born at a relatively premature stage, and completes its development externally in a pouch that contain mammary glands
Examples are kangaroos, wombat, Tasmanian devil and opossum

53. Marsupials

54. Fainting: Adaptations that my not always work
Marsupials
Fainting: Adaptations that my not always work

55. Monotremes They are the only mammals that hatch their young from eggs.
The echidna and the platypus

56. Monotremes

57. Placental Mammals
These are animals, like humans, that contain a structure called the uterus where the embryo develops
Within the uterus, a specialized structure called the placenta forms
It is through the placenta that the exchange of nutrients, wastes, and respiratory gases between the embryo and the mother take place
The umbilical cord, which contains blood vessels, attaches the embryo to the placenta

58. Placental Mammals

59. Placental Mammals

60. Umbilical cord

61. And now to
Chapter 25,
Sexual Reproduction
and
Development in humans