
- a. What assures that only a sperm of the correct species fertilizes a sea urchin egg?
- b. What assures that only one sperm will fertilize an egg?
a.

To determine: The way to assure that only sperm of correct species fertilizes a sea urchin egg.
Introduction: The process by which the male germ cells fuses with the female germ cell is termed as fertilization. The female germ cells are known as eggs, while the male germ cells are called sperms. The sperms are the mobile cells that have the capability to travel to the eggs.
Explanation of Solution
There are two types of fertilization. These are internal and external fertilization. Internal fertilization is the process in which the fusion of eggs and sperms takes place inside the females. However, if the fusion of egg and sperm takes place in the outer environment, it is called external fertilization.
Sea urchins represent external fertilization as the females release their eggs in the water. The male sea urchins also release the sperms in the water and the fertilization of egg and sperm occurs in the external environment.
There are high chances that the sperms of an incorrect species can mate with the eggs of sea urchin. The sea urchins have a technique by which they avoid the mating of eggs with sperms of incorrect species. The eggs have an outer layer called zonapellucida. The sperms of correct species release specified proteins that bind with the receptors present on zonapellucida of eggs. The complementary binding of proteins released by sperms with receptors of eggs is highly specific. This assures only sperm of correct species fertilizes a sea urchin egg.
Thus, the complementary binding of proteins released by sperms with receptors present on zonapellucida of eggs assures only sperm of correct species fertilizes a sea urchin egg.
b.

To determine: The way to ensure that only one sperm fertilizes an egg.
Introduction: The process by which a single sperm fuses with the egg is termed as monospermy. However, the process by which multiple sperms are able to fertilize a single egg is called polyspermy.
Explanation of Solution
Polyspermy can lead to several abnormal conditions that can affect the offspring. All the organisms generally represent monospermy and not polyspermy. They have developed certain methods to ensure that only one sperm fertilizes with the egg.
The eggs have certain organelles called cortical granules. The function of these granules is to prevent polyspermy. They help in the regulation of monospermy. The complementary binding sperms and eggs activate cortical granules. Activated cortical granules release certain enzymes. These enzymes alter the extracellular matrix of zonapellucida. The enzymes secreted by cortical granules also initiate the formation of a hard outer layer around the zonapellucida. This layer prevents the fusion of other sperms with the eggs. The first sperm causes the membrane depolarization of zona pellucida. This leads to a fast blocking of the fertilized egg to prevent the fusion with other sperms. This process is used by the sea urchins to ensure that only one sperm fertilizes an egg.
Thus, the release of enzymes from cortical granules ensures that only one sperm fertilizes an egg. The first sperm that fuses with the egg causes membrane depolarization and fast blocking. This assures that only one sperm fertilizes an egg.
Want to see more full solutions like this?
Chapter 47 Solutions
Study Guide for Campbell Biology
- What is this?arrow_forwardMolecular Biology A-C components of the question are corresponding to attached image labeled 1. D component of the question is corresponding to attached image labeled 2. For a eukaryotic mRNA, the sequences is as follows where AUGrepresents the start codon, the yellow is the Kozak sequence and (XXX) just represents any codonfor an amino acid (no stop codons here). G-cap and polyA tail are not shown A. How long is the peptide produced?B. What is the function (a sentence) of the UAA highlighted in blue?C. If the sequence highlighted in blue were changed from UAA to UAG, how would that affecttranslation? D. (1) The sequence highlighted in yellow above is moved to a new position indicated below. Howwould that affect translation? (2) How long would be the protein produced from this new mRNA? Thank youarrow_forwardMolecular Biology Question Explain why the cell doesn’t need 61 tRNAs (one for each codon). Please help. Thank youarrow_forward
- Molecular Biology You discover a disease causing mutation (indicated by the arrow) that alters splicing of its mRNA. This mutation (a base substitution in the splicing sequence) eliminates a 3’ splice site resulting in the inclusion of the second intron (I2) in the final mRNA. We are going to pretend that this intron is short having only 15 nucleotides (most introns are much longer so this is just to make things simple) with the following sequence shown below in bold. The ( ) indicate the reading frames in the exons; the included intron 2 sequences are in bold. A. Would you expected this change to be harmful? ExplainB. If you were to do gene therapy to fix this problem, briefly explain what type of gene therapy youwould use to correct this. Please help. Thank youarrow_forwardMolecular Biology Question Please help. Thank you Explain what is meant by the term “defective virus.” Explain how a defective virus is able to replicate.arrow_forwardMolecular Biology Explain why changing the codon GGG to GGA should not be harmful. Please help . Thank youarrow_forward
- Stage Percent Time in Hours Interphase .60 14.4 Prophase .20 4.8 Metaphase .10 2.4 Anaphase .06 1.44 Telophase .03 .72 Cytukinesis .01 .24 Can you summarize the results in the chart and explain which phases are faster and why the slower ones are slow?arrow_forwardCan you circle a cell in the different stages of mitosis? 1.prophase 2.metaphase 3.anaphase 4.telophase 5.cytokinesisarrow_forwardWhich microbe does not live part of its lifecycle outside humans? A. Toxoplasma gondii B. Cytomegalovirus C. Francisella tularensis D. Plasmodium falciparum explain your answer thoroughly.arrow_forward
- Select all of the following that the ablation (knockout) or ectopoic expression (gain of function) of Hox can contribute to. Another set of wings in the fruit fly, duplication of fingernails, ectopic ears in mice, excess feathers in duck/quail chimeras, and homeosis of segment 2 to jaw in Hox2a mutantsarrow_forwardSelect all of the following that changes in the MC1R gene can lead to: Changes in spots/stripes in lizards, changes in coat coloration in mice, ectopic ear formation in Siberian hamsters, and red hair in humansarrow_forwardPleiotropic genes are genes that (blank) Cause a swapping of organs/structures, are the result of duplicated sets of chromosomes, never produce protein products, and have more than one purpose/functionarrow_forward
- Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning
- Biology: The Dynamic Science (MindTap Course List)BiologyISBN:9781305389892Author:Peter J. Russell, Paul E. Hertz, Beverly McMillanPublisher:Cengage LearningHuman Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage LearningBiology 2eBiologyISBN:9781947172517Author:Matthew Douglas, Jung Choi, Mary Ann ClarkPublisher:OpenStax




