Chapter 36.4 LBL - LBL PDF

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Biol 106 10th edition

Learn Before Lecture Chapter 47

Animal Development Chapter 47 – Animal Development Concept 47.1: Fertilization & Cleavage Fertilization: The events following contact of a single sperm and egg ensure that the nucleus of only one sperm enters the egg cytoplasm. Q1. Sperm: What is the function of the acrosomal reaction? That is, what does it accomplish in the process k eaho l ei nt hej e l l yc oa t .Pr o t e i n sont hes ur f a c eo ft hea c r os o ma lp r oc e s sb i ndt o of fertilization? ma r e c e p t o r si nt h ee g gp l a s mame mb r a ne . Q2. Ovum: What is the function of the cortical reaction? Co r t i c a lgr a n ul e si nt hee ggf u s ewi t ht hep l a s ma me mb r a ne . Th es e c r e t e dc o nt e n t sc l i po ffs p e r mbi n d i n gr e c e p t o r sa ndc a us et hef e r t i l i z a t i one n v e l o p et o f or m. Q3. Mammals have internal fertilization so the issue of making sure the right species’ sperm is fertilizing the egg is not an issue by the time the sperm reaches the egg. a. Sperm: Briefly explain what “capacitation” is: a functional maturation of the spermatozoon. The changes take place via the sperm cell membrane in which it may be that receptors are made available through the removal of a glycoprotein layer. The area of the acrosomal cap is also so altered thereby that the acrosome reaction becomes possible. b. Ovum: Explain the “zona pellucida” – what is it and what does it do in the process of fertilization? the thick transparent membrane surrounding a mammalian ovum before implantation. Note: A fertilized egg is called a zygote.

Cleavage The zygote undergoes division (cleavage) creating a ball of two cells … then four cells … then eight cells. Q4. What name is given to the cells? Fertilized egg, four-cell stage, early blastula, later blastula. Blastomere Q5. In animals with large yolks, in which end is it concentrated? Circle one: Animal pole / Vegetal pole Concept 47.2: Morphogenesis Gastrulation: This process begins once the blasula has become a ball of cells surrounding an internal cavity. Gastrulation establishes the three germ layers No Yolk: Yolk affects the cleavage and gastrulation processes: trace the process in eggs with differing amounts of yolk: Read the description of gastrulation in sea urchins. Q6. What is an archenteron? the rudimentary alimentary cavity of an embryo at the gastrula stage.  endoderm and mesoderm. Q7. What is a blastopore? the first opening in development, the blastopore, becomes the animal's mouth. In deuterostome development, the blastopore becomes the animal's anus. Q8. Now examine Figure 47.8 in detail. a. In Step 1: What germ layer does the mesenchyme cells become? mesoderm b. In Step 2: What is happening with the yellow-colored cells? What are they doing? Endoderm, mouth and anus.

c. In Steps 3 & 4: What are the mesenchyme cells at the tip of the archenteron doing? What happens to the archenteron as a result of this? Forming the skeleton d. In Step 5: What has the archenteron (yellow) become? Digestive system Q9. Examine Figure 47.9. For each, state which layer it is and list 3 things it becomes as the embryo develops: Germ Layer Which layer it is: What tissues it becomes: a. Endoderm Yellow (3) Digestive tract b. Mesoderm

Red (2)

Skeleton

c. Ectoderm

Blue (1)

Outer layer

Yolk forces modifications of this basic process. Read over the descriptions for gastrulation in eggs with moderate yolk and large yolk. Focus only on how they differ. We will not discuss these in BIOL 106 but you should be familiar enough with the differences to realize that what we will focus on is the simplest model. Developmental of Amniotes Q10. Use Figure 47.13 to label the extra-embryonic membranes of an amniotic egg. Indicate the function of each as well.

Chorion – contributes to placenta formation. Allantois – forms part of the placenta, under-gut. Amnion – innermost membrane, encloses the embryo Yolk sac – provides early stage nourishment

Q11. Organogenesis: Formation of the notochord, nervous system and vertebrae and muscle blocks. a. From which cells is the notochord created? Mesoderm b. From which cells is the neural tubed formed? ectoderm c. What are somites? a division of the body of an animal or embryo. Somites are bilaterally paired blocks of paraxial mesoderm that form along the head-to-tail axis of the developing embryo in segmented animals. d. ….. and what do they give rise to? vertebrae...