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hat is color blindness? A color festival. No. Color blindness or color deficiency is a vision problem. Now, our eyes have light sensitive cells called rods and cones. Can I put ice cream on these cones? You are just unbelievable. Rods are responsible for black and white vision. They do not detect color. Whereas, cones detect color. There are three types of cones. One cone perceives red light, another perceives green and the third perceives blue. Together, these cones help us to see the whole spectrum of colors. Now in some cases, when one or more types of cones do not work properly, it causes color blindness. People with such deficiency have difficulty in distinguishing between certain colors or shades. For example, in red-green color blindness, the apple tree may appear like this.

Normally, male squirrel monkeys can't distinguish between red and green hues-they're what is called color-blind in humans. The South American Saimiri genus lacks a gene that allows color-sensitive cells in the eye, called cones, to differentiate red and green from gray. To these animals, other colors, such as blue, brown and orange, appear faded. But Sam was one of two males in the experimental group of a groundbreaking 2009 ophthalmological study conducted at the Washington National Primate Research Center in Seattle. Husband-and-wife vision researchers Jay and Maureen Neitz injected a viral vector behind the retinas, the part of the eye that responds to color, of Sam and his simian lab partner, Dalton. The virus contained the genetic code in human eyes for red pigment, giving the monkeys an extra class of cone photoreceptor.

We see color because of specialized light-sensing cells in our eyes called cones. One type, L-cones, sees the reds of strawberries and fire trucks; M-cones detect green leaves, and S-cones let us know the sky is blue. But vision scientists have now discovered that not all cones sense color (see video).

When babies are born, their eyes and hair are one color, but change within the first few years of their life! Why do hair and eye colors change? Trace explains the process of inheriting certain traits from your parents, and discusses why the colors change!

Human populations have adapted to varying intensities of sunlight with varying tones of skin coloration. The balanced interplay between melanin content and UV absorption allowed populations to successfully migrate from sub-Saharan Africa by influencing levels of two key vitamins: vitamin D and folic acid. This case study explores the evolutionary advantage of different skin tones for the human race; it also emphasizes the absence of scientific evidence for the correlation of abilities, talents, and other complex traits to skin color, and exposes certain social misconceptions linking skin color to specific traits. Although the discussion of race is not always a comfortable fit for science and biology courses, this case study uses the topic as an inherently interesting and important subject for applying basic biological concepts of DNA, the central dogma, and mutations to real world questions of physical difference and skin color. This case has been used in biology courses for non-science majors but would also be appropriate for advanced high school students.

When ultraviolet sunlight hits our skin, it affects each of us differently. Depending on skin color, it'll take only minutes of exposure to turn one person beetroot-pink, while another requires hours to experience the slightest change. What's to account for that difference, and how did our skin come to take on so many different hues to begin with? Angela Koine Flynn describes the science of skin color.

Some people in the world aren't able to see many colors. The condition is called color blindness, but what exactly causes it?

A data collection and analysis lesson that examines selection for coat color in pocket mouse populations on different color substrates over time.

Focusing on this species of fruit fly, he and the other researchers in the lab of molecular biologist Sean B. Carroll, had made a prolonged assault on one of the key questions in evolutionary biology: how nature endows creatures with their colorful patterns, from a leopard's dark spots to a butterfly's bold swirls. In different species the patterns serve to attract mates, provide camouflage or provide other advantages in the struggle to survive. But what causes the colors to fall so precisely into place?

infographic on vision including color blindness

In this interrupted case study developed for use in a flipped classroom, students read about a picnic that takes place in autumn during the peak of fall color and along the way learn about light absorption by photosynthetic pigments, why leaves turn color in the fall, atmospheric CO2 concentrations and their effect on photosynthesis, and the C3, C4, and CAM photosynthetic pathways. The case is designed to provide introductory biology students with a basic understanding of photosynthetic pathways and how environmental factors affect plants using these pathways. The activity could also be used in an advanced high school biology course covering photosynthesis. The case includes several short videos that students watch as homework before coming to class so that they are prepared to work together in class in small groups to answer the case questions.

Penn State University anthropologist Dr. Nina Jablonski walks us through the evidence that the different shades of skin color among human populations arose as adaptations to the intensity of ultraviolet radiation in different parts of the world.

3:32 video Narrated by anthropologist Nina Jablonski, this engaging animation shows how human skin cells produce the pigment melanin, which gives skin its color.

It's an inevitable side effect of longevity: your hair will turn gray. In this episode, Sophia Cai chats about the chemistry of your natural hair color, why it eventually turns white, and how scientists may be able to slow that graying down.

Links to teacher's guide for October articles Eating with your eyes: The Chemistry of Food Colorings Tooth Decay: A Delicate Balance Probiotics: Good bactria good health Dirt? Who needs it? How hydroponics is poised to change the world Light in the cellar of the sea

This case is based on Kate Chopin's short story "Desiree's Baby," a tragic tale of race and gender in antebellum Louisiana first published in 1893. Students read the story and then answer a series of questions about the genetics and evolution of skin color. The case was developed for a general biology course organized around the general theme of evolution. It could also be used in anthropology and biology courses for non-majors.

The theory of evolution by natural selection is simple, elegant, and profound. Yet, a large number of undergraduate students including biology majors, medical students, and pre-service science teachers maintain a large set of misconceptions that interfere with a solid understanding of the process of natural selection. It is also well known that lecturing is an insufficient strategy to help students confront and correct these misconceptions. This activity uses the evolution of coat color in oldfield mice (Peromyscus polionotus) as the basis of a case study in which students investigate the role of variation, heritability, and selection in the evolution of a trait. Students examine graphs, data, and excerpts from a series of papers that have been published about this system over the last 100 years. The content is delivered as an interrupted case and encourages peer-to-peer teaching and interaction. The case is appropriate for use in non-major, introductory, or advanced biology courses.

4:42 At least one entire class of dinosaurs seems to have had feathers -- including velociraptors, and probably T. rex. Find out how we know, and how we even know what color some of them were!

This interrupted case is based on a genome wide association study (GWAS) that identified the genetic variation causing some inhabitants of the Solomon Islands to have blond hair. The case illustrates the connection between genotype and phenotype, and an application of Hardy-Weinberg equilibrium. The narrative focusses on John and his new roommate, Peter, from the Solomon Islands who happens to have dark skin and blond hair. Using thought-provoking questions students learn about the genetics and the biochemistry of the hair color trait and how a single genetic variation can influence phenotype. Is migration or mutation involved?  Upon completion of the activity students will know the source of the genetic variation that causes the blond hair phenomenon in the Solomon Islands and if it has any European origins. The case was written for an upper-level genetics course, but could also be adapted for introductory biology or for a genetics course for non-majors. An optional PowerPoint presentation with clicker questions is available for download from within the Answer Key.

The online textbook provides a background to understand and discuss the natural functioning of the different Earth systems; it introduces humans as part of the overall ecosystem and explores what is needed to sustain human life; and it looks at the effects that human actions have on different natural systems. The online textbook also includes full-color images of related figures, glossary terms, and a bibliography for further reading.