Beth+L.

= Wiki Post #3-The Endocrine System: January 24th, 2014 =



The **endocrine system** is a system of glands involved in maintaining homeostasis in the body. Directed by the **pituitary gland,** the endocrine glands secretes different types of hormones directly into the bloodstream (some of which are transported along nerve tracts). Unlike the **exocrine system,** it does not secrete into ducts. The hormones secreted by the endocrine glands help to regulate blood pH, glucose levels, thirst and hunger, and many other functions.

**The Endocrine System and its ten glands **

**Pituitary Gland**: It is often considered to be the most important part of the endocrine system. It produces hormones that control many functions of other endocrine glands. **Hypothalamus:** This part of the brain is important in regulation of metabolism and body temperature. It also produces hormones that are stored in the pituitary gland.

**Thyroid Gland:** The thyroid glands produce hormones that regulate the body's metabolism. They also play a role in bone growth and development of the brain and nervous system in children.

**Parathyroid Glands:** They release the parathyroid hormone, which plays a role in regulating calcium levels in the blood and bones.

**Adrenal Glands:** The adrenal glands are made up of two parts. The outer part is called the adrenal cortex and the inner part is called the adrenal medulla. The outer part produces hormones which regulate: the body's metabolism, the balance of salt and water in the body, the immune system, and sexual function. The inner part, or adrenal medulla, produces hormones that help the body cope with physical and emotional stress by increasing the heart rate and blood pressure.

**Pineal Gland:** It secretes a hormone called melatonin, which may help regulate the wake-sleep cycle of the body.

**Reproductive Glands:** The reproductive glands are the main source of sex hormones. In males they are testicles, and in females they are ovaries.  **Pancreas:** The pancreas has digestive and hormonal functions.


 * The ten endocrine glands close-up **

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 * A video explaining the endocrine system **



**Resources: ** [] [] [|http://www.livestrong.com/article/78174-three-parts-human-brain] []

**Read More: ** [] [] [] [] = = = Wiki Post #2-Evolution: November 29th, 2013 =

The Evolution of Eyes
Different types of animal eyes Of all the animal species in the world, about 96% have eyes. Because life is so closely linked to the sun, many organisms (outside those who live in total darkness) have evolved the ability to detect and respond to light. The first animal eyes mainly detected light —they helped to establish day/night and coordinate behavior—but eventually more complex eyes evolved. It is the animals like human beings with image-forming eyes that have taken light direction to an entirely new level.

The evolution of eyes over a span of 350 000 generations
 * The Origin of the Eye**

Most experts believe the development of the eye is monophyletic. All modern eyes, as varied as they are, are believed to have their origins in a proto-eye believed to have evolved about 540 million years ago. The earliest predecessors of the eye were photoreceptor proteins that can sense light. These predecessors are called eyespots, and they are found even in unicellular organisms. These eyespots can only sense ambient brightness: they can distinguish light from dark. The eye seemingly began evolving so prey animals and competing predators alike match and exceed the capabilities needed for survival. Eyes were no longer just needed for light detection, but were needed to survive. With that being said, multiple eye types and subtypes developed in parallel to match the needs of organisms.

The //stigma// (2) of the euglena hides a light-sensitive spot. media type="custom" key="24525802" align="center"

A video explaining how the human eye could have evolved from eyespots
 * Developments in the Ey****e**

The eyes of many organisms have come quite far from the simple eyespots that were once so common. Some species, like humans, have **//color vision//**. The ability to see colors presents selective advantages for species, such as being better able to recognize predators, food, and mates. Color vision developed at some point when photoreceptor cells developed multiple pigments. Many species have also evolved the **//location//** of their eyes to best suit their means of survival. Prey animals, like flatfish, generally have their eyes on the sides of their heads to have a larder field of view. Predators, however, have their eyes in front of their head to have better depth perception and to locate their prey more easily.

Predator vs. prey eyes Many animals have also developed a **//focusing mechanism.//** Many organisms with small eyes are active in direct sunlight and can survive without a focusing mechanism. As a species grows larger, or moves to a dimmer environment, a need of focusing appears gradually.


 * Further Information**

"The Evolution of Vision", a documentary: []

A Virtual Timeline of vision: []

Why the eye evolved: []

A slideshow of macro eye pictures: []


 * Sources Cited**

[] [] [|http://en.wikipedia.org/wiki/Evolution_of_the_eye#One_origin_or_many.3F] []