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Photoreceptors

Photoreceptors

The function of the retinal pigment epithelium in the outmost layer of the retina; an explanation of depolarization and the dark current; meaning of membrane potential and how depolarization releases neurotransmitters; how light hyperpolarizes a photoreceptor and reduces the release of neurotransmitters through a graded response; synapse of a photoreceptor onto bipolar cells.

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Inside the Human Eye

Inside the Human Eye

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.

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Human Vision

Human Vision

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.

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Truly Amazing Mangroves

Truly Amazing Mangroves

Adaptions allowing mangroves to populate intertidal areas including aerial stilt roots, ways of disposing of excess salt and ways of conserving water. Features of red, black, white mangroves and buttonwoods and their zonation in mangrove forests. Seedlings of different mangrove species and their dispersal. How seedlings grow on parent trees before dropping off. Benefits to communities.

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Origins of Plants on Land

Origins of Plants on Land

The evolution of prokaryotic bacteria in ancient seas 3.8 billion years ago; how cyanobacteria evolved to use visible light as a source of energy; the appearance of stromatolites in ancient seas; how the evolution of eukaroyotic cells led to the appearance of sea algae; how sea algae adapted to living on land to form the first land plants, the bryophytes. Some adaptions that prevent the dessication of bryophytes.

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Discovery of Circulation of Blood

Discovery of Circulation of Blood

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.

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Mammals, Endotherms and Warm Blood

Mammals, Endotherms and Warm Blood

‘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.

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Reptiles, Ectotherms and Cold Blood

Reptiles, Ectotherms and Cold Blood

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.

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Seed Dispersal by Fire

Seed Dispersal by Fire

This article discusses ways in which plants have adapted to disperse their seeds after fire has destroyed the landscape. Species explored include the Lodgepole pine trees and two Banksia species from Australia; how seeds disperse through the effects of smoke shock (Whispering Bells) and heat shock (Sweet Wattle) following forest fires; how species indirectly benefit from forest fires to help disperse their seeds.

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Convergent Evolution -What Is It?

Convergent Evolution -What Is It?

This science artilce investigates convergent evolution in different organisms and how two totally unrelated species can evolve to resemble each other in different ways. We investigate convergent evolution in color, body shape, body organs, defensive spines, tongues, eyes, animal behavior, brain function, mimicry and in extinct species. We also look at convergent evolution in animals, plants, fish, insects and reptiles.

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