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Humans: Members of the species Homo sapiens.

Biodiversity and Human Values

JoVE 10952

Human civilization relies on biodiversity in many ways. Sudden changes in species biodiversity result in environmental changes that can modify weather patterns and therefore human civilizations.

Humans are dependent on agriculture, which developed when ancestral humans found species that made suitable foods. At least 11,000 years ago, humans started to select plant and animal species to be cultivated on farms. Going back for thousands of years, humans have been artificially selecting species for food, building materials, textiles, and medicine. That progress is ongoing. Human ingenuity continues to benefit from studying the natural world and either directly using or modifying materials and compounds for industrial use. Maintaining the current level of biodiversity will make it substantially more likely that discoveries can be made. For example, in 1969, Thomas D. Brock and Hudson Freeze were studying the Lower Geyser Basin of Yellowstone National Park and discovered a strain of bacteria that is surprisingly heat-tolerant. From this bacteria, an enzyme called Taq polymerase was isolated. This enzyme allows researchers to perform polymerase chain reaction (PCR), which underlies most biotechnological advancements that revolutionized the production of pharmaceuticals, food, and consumer goods among others. For some, discoveries that benefit

 Core: Biology

Color Afterimages

JoVE 10194

Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

Human color vision is impressive. People with normal color vision can tell apart millions of individual hues. Most amazingly, this ability is achieved with fairly simple hardware.

Part of the power of human color vision comes from a…

 Sensation and Perception

Threats to Biodiversity

JoVE 10951

There have been five major extinction events throughout geological history, resulting in the elimination of biodiversity, followed by a rebound of species that adapted to the new conditions. In the current geological epoch, the Holocene, there is a sixth extinction event in progress. This mass extinction has been attributed to human activities and is thus provisionally called the Anthropocene. In 2019 the human population reached 7.7 billion people and is projected to comprise 10 billion by 2060. Indicative of our impact, by biomass (the actual mass of a particular species), humans make up 36% of Earth’s mammals, livestock 60%, and wild mammals only 4%. Approximately 70% of all birds are poultry, so only 30% are wild. To minimize human impact on biodiversity and climate, we have to understand which of our activities are problematic and balance the needs of human civilization and progress with a sustainable plan for future generations. Some of the major threats to biodiversity include habitat loss due to human development, over-farming, and increased carbon dioxide emissions from factories and vehicles. A case study in human impact on the weather can be found in the 1930s event known as the Dust Bowl. In the 1920s and 30s, a large number of farmers moved to the Great Plains and clear cut the land, removing the native ground covering plants in order to

 Core: Biology

Evolutionary Relationships- Concept

JoVE 10561

Humans have been attempting to properly classify living things since Aristotle made the first attempt during the 4th century BC. Aristotle’s system was improved upon during the Renaissance and then, subsequently, by Carolus Linnaeus in the mid 1700’s. These more formal classification and organization systems grouped species by their physical similarity to one another. For example,…

 Lab Bio

Ethics in Research

JoVE 11029

Today, scientists agree that good research is ethical in nature and is guided by a basic respect for human dignity and safety. However, this has not always been the case. Modern researchers must demonstrate that the research they perform is ethically sound.

Research Involving Human Participants

Any experiment involving the participation…

 Core: Psychology

Polygenic Traits

JoVE 10778

When more than one gene is responsible for a given phenotype, the trait is considered polygenic. Human height is a polygenic trait. Studies have uncovered hundreds of loci that influence height, and there are believed to be many more. Due to the high number of genes involved, as well as environmental and nutritional factors, height varies significantly within a given population. The distribution of height forms a bell-shaped curve, with relatively few individuals in the population at the minimum or maximum heights and the majority of the population in the middle height range. Most polygenic traits, like weight, blood pressure, and aspects of fingerprint patterns, also plot as bell-shaped curves. Although Mendel’s seminal work on genetic inheritance focused on traits that arose from single genes, experiments such as genome-wide association studies have revealed that many human traits develop through the cooperation of multiple gene products. The collaboration of numerous genes to influence a phenotype constitutes a polygenic (i.e., “many gene”) trait. One example of a polygenic trait is human height. Hundreds of loci are implicated in human height variability, and it is believed that there are more that have not yet been identified. Many of these genes directly or indirectly affect cartilage in growth plates, which are found in

 Core: Biology

Viral Recombination

JoVE 10826

Cells are sometimes infected by more than one virus at once. When two viruses disassemble to expose their genomes for replication in the same cell, similar regions of their genomes can pair together and exchange sequences in a process called recombination. Alternatively, viruses with segmented genomes can swap segments in a process called reassortment.

Some diseases can infect multiple species. For example, pigs can be infected by some human and bird viruses, in addition to the viruses that usually infect pigs. Because viruses can recombine when they co-infect the same cell, pigs can act like “mixing vessels” that recombine viruses from other species to create new viruses that can sometimes infect humans. This worrisome phenomenon represents a route through which infectious material from other species can enter the human population. Diseases that move from animals to humans are known as zoonoses. Humans can be highly susceptible to such viruses because we have no history of exposure that would have generated immunity. Influenza A is a prime example of the “mixing vessel” theory of viral disease. Research has demonstrated that pig, bird, and human influenza A viruses have reassorted inside pig hosts. These events yielded “double reassortant” viruses that contained genes from human and bird viruses and “triple

 Core: Biology

Microbial and Fungal Diversity- Concept

JoVE 10601

Bacteria and fungi are two highly diverse groups of organisms that can have significant beneficial or detrimental impacts on human health. For this reason, it is important to understand and distinguish between individual species of these groups. As you will recall, biological taxonomists group organisms based on their phylogenetic relatedness. The three domains of life, Bacteria, Archaea, and…

 Lab Bio

DNA Packaging

JoVE 10785

Eukaryotes have large genomes compared to prokaryotes. In order to fit their genomes into a cell, eukaryotes must pack their DNA tightly inside the nucleus. To do so, DNA is wound around proteins called histones to form nucleosomes, the main unit of DNA packaging. Nucleosomes then coil into compact fibers known as chromatin.

Most cells in the human body contain about 3 billion base pairs of DNA packaged into 23 pairs of chromosomes. It is hard to imagine exactly how much DNA these numbers represent. So how much packing has to happen to fit the genome into a cell? We can gain some insight by expressing the genome in terms of length. If we were to arrange the DNA of a single human cell, like a skin cell, into a straight line, it would be two meters long–over 6.5 feet. The human body contains around 50 trillion human cells. This means that each person has a total of about 100 trillion meters of DNA. In other words, each person has enough DNA to stretch from the Earth to the Sun 300 times! And humans do not have particularly large genomes–those of many fish, amphibians, and flowering plants are much larger. For example, the genome of the flowering plant Paris japonica is 25 times larger than the human diploid genome. These figures emphasize the astonishing task that eukaryotes must accomplish to pack their DNA inside cells.

 Core: Biology

Climate Change- Concept

JoVE 10609

The certainty of climate change remains a public controversy despite the consensus among approximately 97% of active climate researchers, who not only agree that the Earth’s climate is changing but also state that this change is intensified by human activity, predominantly carbon emissions 1. The disconnect between the public and the experts is partly due to poor understanding of the…

 Lab Bio
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