Human eye sight compared with the eyesight of cats; evolutionary advantage of seeing in color; different parts of the eye including the cornea, pupil, iris, lens, ciliary muscles, sclera, choroid, vitreous homor and vitreous chamber; an explanation of the pupillary reflex action, short sightedness and long sightedness and how lenses can assist sight, ‘red eye’ syndrome following the use of flash photography.
This article provides a brief overview of the evolutionary path which led to the appearance of human camera eyes which allow us to see so effectively. Features of human vision are explained including how electrical nerve impulses are transmitted from retina of the eye to the visual cortex of the human brain allowing us to ‘see’. How the brain composes images and an explanation of saccadic eye movements.
The ancient greek Galenist view of the movement of blood round the body; Versalius, Fabricuius and Fallopius and their studies of human anatomy. The emergence of William Harvey and how he drew on the work of his predecessors to discover how blood circulates in the human body. A description of some of Harvey’s practical experiments including tying a ligature around a forearm and interpreting the outcome.
‘Warm blood’ and an explanation of what it means to be endothermic. How homeothermic endotherms are able to maintain a constant body temperature within a narrow temperature range; the strong relationship between ‘mass specific basal metabolic rate’ and body mass; surface area to volume ratios; mechanisms by which the body loses and gains heat; abandoning endothermy by hibernation and torpor.
What makes reptiles ‘cold blooded; why ‘ectothermic’ is a more accurate description of reptiles than ‘cold blooded.’ How ectotherms ‘thermoregulate’ their core temperatures by adopting different types of behavior. Physiological adaptions of ectotherms including changing skin color, freeze avoidance and freeze tolerance. Why ectotherms make excellent ambush predators. The hearts of ectotherms.
Reasons why our hunter gatherer ancestors originally evolved a sense of taste; the five senses of taste explained; how our taste receptors are housed in our taste buds; a description of what taste buds are and how our taste receptors work; the four different types of papillae and where they are located on our tongues; the taste buds of some other organisms including catfish, cows, ducks and cats.
Reasons for the evolution of eyesight during the period known as the Cambrian explosion; how the evolution of eyesight resulted in organisms becoming either prey or predators. An explanation of how eyesight evolved through eight simple steps; recessed light sensitive cells, the pin hole eye including a description of the eye of the nautilus mollusc; the spherical lens with greater refractive powers.