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:Describe how soils are formedExplain soil compositionDescribe a soil profile

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:

"All living things need phosphorus to survive. However, its low availability in soil is often a limiting factor for plant and microbial growth. Microorganisms in the plant root-soil interface (rhizosphere) can convert non-labile phosphorus into bioavailable forms. One way microbes do this is the mineralization of organic phosphorus compounds like phytate. Rising atmospheric CO₂ levels may accelerate mineralization, but the molecular mechanisms are not yet understood. Recent research confirmed that elevated CO₂ (eCO₂) increased the mineralization of phytate in the rhizosphere of wheat. Tracing the carbon flow showed that plants grown under eCO₂ increased the release of bioavailable carbon belowground, which corresponded to increased microbial growth and altered community composition. The bacterial community under eCO₂ favored groups of bacteria capable of degrading aromatic phosphorus compounds and the mycorrhizal fungi benefited from the increased supply of phosphorus and carbon..."

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:

"Plants are shaped by the many microbes they host. But scientists are only beginning to understand how, especially in underexplored plant structures like aerial roots. A new study shows that the mucilage secreted by these roots can create a microbiome unlike that found in underground roots and nurture an environment that caters to beneficial, nitrogen-fixing bacteria. Researchers made these discoveries by examining the aerial roots of pink lady shrubs—a fast-growing invasive plant. Metabolite profiling of aerial root mucilage revealed a rich cocktail of nutrients that would be expected to support an equally rich variety of microbes. But genomic analyses suggested a mucilage community dominated by nitrogen-fixing diazotrophs. This homogeneous community structure was linked to the presence of the fungus C. raphigera. The antibacterial activity of this fungus was such that only diazotrophs were allowed to thrive, to the benefit of the pink lady shrubs..."

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:

"With the world’s population expected to grow to over 9 billion by 2050, food is a major concern. Much of our increased food needs could be met by improving the yield of agricultural crops. A recent study examined one aspect of plant health: the plant microbiome, which plays a critical role in host health and productivity. Researchers focused on oilseed rape (OSR), the third most cultivated crop in the UK and a major source of vegetable oil. Field experiments have indicated that OSR yield declines proportionally with how often it is grown in rotation and while this has been associated with changes to the rhizosphere microbiome, it is unknown which microbes negatively affect plant yield. Comparing rhizosphere soil and bulk soil samples from 37 farms across the UK, they found that protists, bacteria, and fungi were influenced differently. Fungi were more widely influenced by the rotation frequency, but specific bacteria and protist species were also affected..."

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:

"Long-term mono-cropping often suppresses plant growth, but the mechanisms behind this are poorly understood. The key may lie in the soil surrounding the plants’ roots. This region, the rhizosphere, is filled with important microbes and the carbon-containing photosynthesis products, rhizodeposits, that plants exude from their roots. Rhizodeposits are part of the link between plants and their rhizosphere microbes. So, a team of researchers examined the interactions among rhizodeposits, rhizosphere microbes, and mono-cropping long-term. They found that years of mono-cropping led to a gradual decrease in carbon deposition and the chemical diversity of the rhizodeposits. These decreases were strongly correlated with decreases in the rhizosphere microbial diversity and metabolic functioning. Mono-cropping long-term also slowly led to a decrease in the abundance of plant-beneficial microbial groups..."

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:

"Root and rhizosphere microbiota play a critical role in the health and success of plants, but selectively breeding plants for a healthy microbiome has proven difficult. Plants will often directly influence their root microbiota via compounds exuded from their roots. Examining these pathways for potentially heritable traits could improve our ability to selectively breed for healthy microbiomes. One such pathway is a class of defense compounds secreted by maize roots called benzoxazinoids (BXs). Researchers examined the root and rhizosphere microbiotas of BX-producing and BX-defective lines of maize across several locations and soil types. BX secretion affected the community composition in both root and rhizosphere microbiotas. The root microbiota of BX-exuding lines consistently had less Flavobacteriaceae and Comamonadaceae..."

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:

"Nanotechnology has enabled numerous advances in communications, medicine, energy, and agriculture. But as the proliferation of nanomaterials ramps up, unintended consequences are becoming increasingly visible. A recent study examined the effects of silver nanoparticles on soils supporting the growth of maize. Findings revealed a 30% decrease in the relative abundance of members of the archaea community, which are important for nitrogen cycling in soil, vital for plant growth. Nanosilver also increased the abundance of certain possibly phytopathogenic fungi, possibly by eliminating bacteria that normally keep these harmful fungi in check. Finally, increased root growth seems unsustainable because it is probably caused by these stress factors, and not by beneficial effects. While this study was limited to relatively small, pot experiments, the findings suggest that the microbiome is an essential inclusion for studying the long-term effects of nanomaterials on the environment..."

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:

"Plants evolved in a world dominated by prokaryotic and eukaryotic microbes. Underneath the surface, plant roots interact with microbes in the soil – the rhizosphere microbiome. But although bacteria and fungi are well-studied in the rhizosphere, other components, including viruses and protists, are less well understood. To better understand the extent to which biological and environmental factors shape protist communities, researchers analyzed protist communities associated with the rhizosphere and bulk soil of switchgrass plants in different developmental stages. They found that the diversity of protists was lower in the rhizosphere than in the bulk soil and that the composition of protist communities changed through the different phenological stages of the plant..."

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:

"At the roots of plants, there is more than meets the eye. The rhizosphere – the soil in contact with plant roots – is home to a rich community of microbes that are tightly associated with plant roots. Microbes can benefit plants by increasing nutrient availability, producing plant growth hormones, and protecting against pathogens, while in contrast, soilborne pathogens can reduce plant growth and cause yield loss. A recent study sought to better understand how plants influence their associated root bacteria. Using a multi-selection system and infection by the soilborne pathogen Rhizoctonia solani AG8, researchers found that successive plantings enhanced disease suppression in wheat cultivars. Distinct bacterial community profiles assembled over successive plantings, and the cluster of bacterial communities in AG8-infected plants was different from those in uninfected plants. In infected plants, bacteria that act as antagonists to AG8 and promote plant growth were enriched..."

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:

"Plant health is essential for food production, but plants are often affected by pathogens that can threaten plant performance including crop yield. Unfortunately, we can often only predict plant health when pathogens have infected plants and can no longer be controlled – and by then it is too late. To counteract pathogens, farmers often apply extensive amounts of pesticides throughout plant growth. But excessive pesticide use is costly and affects the biodiversity of the surrounding species. A recent study sought to find a way to predict plant health before planting. Researchers investigated different classes of soil microbes throughout the growth of tomato plants. They found that bacterial predators called protists were the best predictors of pathogen dynamics in growing plants..."

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:

"Salt marsh ecosystems perform multiple “ecosystem services”. For example, they clean the water, protect coastlines against storm surges, and support fisheries. Sediment microbes in these ecosystems are known to mediate cycling of important nutrients, but their effects on marsh plant productivity are unclear. To learn more, a new study analyzed the sediment and root microbiomes of a dominant marsh plant, _Spartina alterniflora_. The sediment of taller _S. alterniflora_ had greater microbial biomass and faster organic matter mineralization than that of shorter plants, suggesting that the sediment microbes helped support plant productivity. The sediment and root-adjacent (rhizosphere) microbiomes of taller plants were also more diverse. Among _S. alterniflora_ of all sizes, root microbes were less diverse than sediment and rhizosphere microbes, implying that the roots were colonized by highly competitive microorganisms..."

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:

"Designer rootstocks enable fruit trees to thrive under otherwise unbearable conditions, providing strong anchorage and defending against biological and nonbiological stressors. But what role does the root microbiome play in this assistive act? To find out, researchers used 16S rRNA sequencing to examine the rootstocks of Valencia orange trees in Florida. Results showed that the genetic makeup of different rootstocks determined how the root microbiome responded to compost treatment. The aspects of the root microbiome that were rootstock- specific included bacterial abundance, diversity, and community composition. These findings suggest that specific bacteria drive changes in nutrient concentrations accessed by different rootstocks. Understanding this intimate relationship is important to supporting overall plant health and could inspire research into how root microbes might affect other parts of trees..."

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:

"Plants form a close bond with a vast range of microorganisms. In fact, this microbiome could be viewed as an extended phenotype of the plant genome enhancing plants’ ability to cope with environmental stress. To understand this connection, researchers recently examined the microbiome of the model legume Medicago truncatula. They found that bacterial diversity decreased between external and internal plant compartments and that microbiome composition was shaped by strong interactions between compartment type, soil, and plant genotype with the microbial composition of external compartments driven by soil origin and the microbial composition of internal compartments driven by host genetics. All compartments were dominated by Ensifer, the nitrogen-fixing bacteria that form root nodule symbiosis with M. truncatula..."

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:

"Above ground, plants can seem fairly simple, but below, there is a rich world full of hidden activity. To promote their growth, plants secrete chemicals from their roots that can affect the soil and air around them. This helps them adapt to environmental conditions, stressors, and pathogens. But how these chemicals affect the plants’ microbiota is poorly understood. A recent study evaluated chemical interactions between peanut plants and cassava, which are often co-cultivated. The researchers found that cassava plants produced cyanide, which induced stress in peanut plants. This caused the peanut plants to emit ethylene, a volatile hormone that diffuses through gas and water in the soil. Ehtylene, in turn, attracted specific microbial species that helped to remineralize the soil, ensuring that the peanut plants could increase their yield alongside cassava..."

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:

"Soil not only provides the water and nutrients necessary for plant growth but also hosts a huge reservoir of microorganisms with important positive and negative effects on plant health. Scientists are now looking toward harnessing these soil microorganisms to design synthetic microbial communities that can help control plant disease. A team of researchers recently investigated the relationship between soil microorganisms and diseased plants of Astragalus mongholicus, a member of the pea family. They found that bacteria with particular growth-promoting or disease-inhibiting abilities colonized the roots of plants with fungal root-rot disease and the surrounding soil..."

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