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 fertilization occursExplain how the embryo forms from the zygoteDiscuss the role of cleavage and gastrulation in animal development

Embryo, when applied to mammals, is the term given to the developing organism from fertilisation to birth. Developmental biology, or embryology, is the study of the embryo as it transforms from a unicellular zygote to a multicellular, mulitsystemed organism which in some cases is ready to function autonomously at birth. Developmental biology is of interest to vets in understanding why organs and systems are the way they are, but also in understanding genetic diseases and applying cell based therapies to treat loss or damage to tissues.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Small metabolites produced by gut microbes can directly affect the central nervous system, but it’s unclear if these molecules influence very early stages of neural development. To find out, researchers recently compared normal and germ-free zebrafish embryos. There were no gross morphological differences, but neural gene expression was significantly suppressed in the germ-free embryos and this suppression was eliminated by treatment with zebrafish gut metabolites. Specifically, 354 genes were downregulated in germ-free compared with normal embryos and just a single treatment with zebrafish gut metabolites restored the normal expression levels of 39 of these genes. The downregulated genes were involved in important neurodevelopmental pathways, such as transcriptional regulation and Wnt signalling and closer investigation at the cellular level confirmed that Wnt-dependent developmental features were disrupted in the germ-free embryos..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

Hair germs begin from an aggregation of keratinocytes in the stratum basale of the epidermis. The initiating factor is the underlying dermal fibroblast cells. The keratinocytes elongate, divide and relocate to the dermis. Dermal fibroblasts then form a dermal papilla beneath the hair germ. This causes stimulation of the basal stem cells to up-regulate their cycle, producing cells that will keratinise and form the hair shaft.

The limbs develop from the lateral plate mesoderm. Limb development is highly conserved; in all land vertebrates there are only four limbs and they are always opposite each other with respect to the midline of the body. All vertebrate limbs have the same patterning of; stylopod - proximal part of the limb which produces the humerus or femur; zeugopod - intermediate part of the limb which produces the radius and ulna or tibia and fibula; autopod - distal part of the limb that produces the carpals and metacarpals or tarsals and metatarsals. Other animals also follow this limb pattern including the greatly modified bird's wing.

This lesson presents an overview of how plants are propagated. Upon completion of this unit students will know how to propagate plants both sexually and asexually. 

Psychology is designed to meet scope and sequence requirements for the single-semester introduction to psychology course. The book offers a comprehensive treatment of core concepts, grounded in both classic studies and current and emerging research. The text also includes coverage of the DSM-5 in examinations of psychological disorders. Psychology incorporates discussions that reflect the diversity within the discipline, as well as the diversity of cultures and communities across the globe.Senior Contributing AuthorsRose M. Spielman, Formerly of Quinnipiac UniversityContributing AuthorsKathryn Dumper, Bainbridge State CollegeWilliam Jenkins, Mercer UniversityArlene Lacombe, Saint Joseph's UniversityMarilyn Lovett, Livingstone CollegeMarion Perlmutter, University of Michigan

By the end of this section, you will be able to:Describe the stages of prenatal development and recognize the importance of prenatal careDiscuss physical, cognitive, and emotional development that occurs from infancy through childhoodDiscuss physical, cognitive, and emotional development that occurs during adolescenceDiscuss physical, cognitive, and emotional development that occurs in adulthood

n the verterbrate embryo, as the primitive streak is regressing, the paraxial mesoderm divides into blocks of cells called somites. These divisions can be seen either side of the notochord. Somites are transient structures that will give rise to cells of the vertebrae and ribs, dermis of the dorsum, skeletal muscle of the body wall, back and limbs. Somites begin to develop at the anterior of the embryo first, and appear at regular intervals.

By the end of this section, you will be able to:Describe the stages of prenatal development and recognize the importance of prenatal careDiscuss physical, cognitive, and emotional development that occurs from infancy through childhoodDiscuss physical, cognitive, and emotional development that occurs during adolescenceDiscuss physical, cognitive, and emotional development that occurs in adulthood

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Pregnancy loss and infertility affect one in six couples, and better understanding of the underlying mechanisms is needed for treatment. A good place to start is embryo implantation -- the first step of pregnancy. Unfortunately, few studies have evaluated the mechanisms affecting embryo implantation potential. A new study evaluated the signaling mechanisms behind a cell polarization process called epithelial-mesenchymal transition (EMT). EMT directs both the formation of the placenta by trophoblast cells and cell differentiation in the developing embryo. Researchers evaluated embryo implantation in wild-type mice and mice lacking components of the Wnt/β-catenin-lin28a signaling pathway. Their results showed that active β-catenin was present in the pre-implantation embryonic membrane, and silencing Wnt/β-catenin signaling reduced the embryo implantation rate..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Wnt signaling plays key roles in many processes, including cell polarity, proliferation, differentiation, and migration. The pathway is centrally involved in neurite and synapse development and maintenance. Wnt activity can be inhibited by Porcupine, an acylase that modifies Wnt ligands. A new study sought to understand how Wnt ligands affect neurite development. Using Wnt-C59, a Porcupine inhibitor, researchers blocked the secretion of endogenous Wnts in rat embryonic hippocampal neurons. They found that inhibiting Porcupine changed the morphology of the dendritic arbors and neurites of hippocampal neurons, while axonal polarity was not affected. β-catenin and Wnt3 levels decreased with Porcupine inhibition, while GSK-3β increased. Adding exogenous Wnt3a, 5a, and 7a ligands rescued the changes in neuronal morphology. Wnt3a restored neurite length to near the control, while Wnt7a increased the neurite length beyond that of the control..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"A fundamental law of genetics states that offspring do not inherit traits from their parents that were acquired in response to environmental conditions. Recent research in the field of epigenetics, however, is turning this principle on its head. Several recent studies have come to the remarkable conclusion that unhealthy diets in males can contribute to the development of metabolic diseases in their offspring. Even when those offspring are raised with healthy diets_._ Now, a study has identified small RNAs as the molecules responsible for the transmission of these disorders. For a long time scientists thought that inheritance of traits only occurred via DNA being passed from parent to offspring. It is now clear, however, that the experiences of one generation can have an effect on the next. When parents have a high-stress lifestyle or an unhealthy diet, for example, chemical modifications can occur on genes that are then passed to their children. This is termed ‘epigenetic inheritance..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

This video (3:29) briefly explains why early embryonic zebrafish are ideally suited to identify chemical biological activity.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Congenital heart defects (CHDs) are common, affecting 9 out of every 1000 babies born. CHDs are caused by various gene mutations that prevent the heart chambers and/or valves from forming properly. However, the precise mechanisms of chamber development and how they are dysregulated in fetuses with CHDs are unclear. To learn more, researchers recently investigated the molecular signals of heart development in a zebrafish animal model. They found that all heart cells expressed the gene sema3fb, which encodes the cell guidance cue Sema3fb. However, only ventricle-specified cells expressed the gene encoding this cue’s receptor, Plxna3, effectively restricting Sema3fb signaling to the ventricle. In zebrafish embryos with sema3fb mutations (ca305 and ca306), heart chamber development was impaired. Specifically, the atrium and ventricle were too small because the cells were shrunken, which caused the heart to pump less blood and fill with fluid..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.