Biology is designed for multi-semester biology courses for science majors. It is …
Biology is designed for multi-semester biology courses for science majors. It is grounded on an evolutionary basis and includes exciting features that highlight careers in the biological sciences and everyday applications of the concepts at hand. To meet the needs of today’s instructors and students, some content has been strategically condensed while maintaining the overall scope and coverage of traditional texts for this course. Instructors can customize the book, adapting it to the approach that works best in their classroom. Biology also includes an innovative art program that incorporates critical thinking and clicker questions to help students understand—and apply—key concepts.
By the end of this section, you will be able to:Discuss how …
By the end of this section, you will be able to:Discuss how fertilization occursExplain how the embryo forms from the zygoteDiscuss the role of cleavage and gastrulation in animal development
Once sperm has entered the the oocyte, an ootid is formed. During …
Once sperm has entered the the oocyte, an ootid is formed. During early stages the ootid will contain male and female pronuclei along with the first and second polar bodies. Fusion of the male and female pronuclei will result in a single diploid nucleus or syngamy. Once syngamy has occurred, the zona pellucida then develops into an imprenetrable layer that prevents polyspermy and so polyploidy. Once the zona pellucida has developed, the ootid is now referred to as a zygote (diploid) and will begin undergoing mitotic divisions via a cleavage process that will begin to give rise to daughter cells called blastomeres. These cleavage divisions will begin to produce a 4-celled embryo and then an 8-celled embryo.
We've reached the grand finale of our four-part series on human reproduction: …
We've reached the grand finale of our four-part series on human reproduction: BABIES! Today Hank walks you through the stages of pregnancy, beginning with how a zygote develops into blastomeres to a morula to a blastocyst, and finally to an embryo and a fetus. He also explains some of the amazing anatomical changes that take place in the mother and the hormonal sequence of events that lead to labor.
Chapters: Introduction: How Did You Get Here? Cleavage Stage: Zygote, Blastomeres, Morula, Blastocyst Implantation The Placenta Embryonic Stage Female Anatomical Changes During Pregnancy Hormonal Sequences Leading to Labor Stages of Labor: Dilation, Expulsion, Placental Delivery Review
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