Why Leaves Change Color?

hy Leaves Change Color?
image of leaf
The Splendor of Autumn

Every autumn we revel in the beauty of the fall colors. The mixture of red, purple, orange and yellow is the result of chemical processes that take place in the tree as the seasons change from summer to winter.

During the spring and summer the leaves have served as factories where most of the foods necessary for the tree’s growth are manufactured. This food-making process takes place in the leaf in numerous cells containing chlorophyll, which gives the leaf its green color. This extraordinary chemical absorbs from sunlight the energy that is used in transforming carbon dioxide and water to carbohydrates, such as sugars and starch.

Along with the green pigment are yellow to orange pigments, carotenes and xanthophyll pigments which, for example, give the orange color to a carrot. Most of the year these colors are masked by great amounts of green coloring.
Chlorophyll Breaks Down

But in the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their food-making process. The chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible and give the leaves part of their fall splendor.

At the same time other chemical changes may occur, which form additional colors through the development of red anthocyanin pigments. Some mixtures give rise to the reddish and purplish fall colors of trees such as dogwoods and sumacs, while others give the sugar maple its brilliant orange.

The autumn foliage of some trees show only yellow colors. Others, like many oaks, display mostly browns. All these colors are due to the mixing of varying amounts of the chlorophyll residue and other pigments in the leaf during the fall season.
Other Changes Take Place

As the fall colors appear, other changes are taking place. At the point where the stem of the leaf is attached to the tree, a special layer of cells develops and gradually severs the tissues that support the leaf. At the same time, the tree seals the cut, so that when the leaf is finally blown off by the wind or falls from its own weight, it leaves behind a leaf scar.

Image of trees changing colors in the fall

Most of the broad-leaved trees in the North shed their leaves in the fall. However, the dead brown leaves of the oaks and a few other species may stay on the tree until growth starts again in the spring. In the South, where the winters are mild, some of the broad-leaved trees are evergreen; that is, the leaves stay on the trees during winter and keep their green color.
Only Some Trees Lose Leaves

Most of the conifers – pines, spruces, firs, hemlocks, cedars, etc. – are evergreen in both the North and South. The needle- or scale-like leaves remain green or greenish the year round, and individual leaves may stay on for two to four or more years.
Weather Affects Color Intensity

Temperature, light, and water supply have an influence on the degree and the duration of fall color. Low temperatures above freezing will favor anthocyanin formation producing bright reds in maples. However, early frost will weaken the brilliant red color. Rainy and/or overcast days tend to increase the intensity of fall colors. The best time to enjoy the autumn color would be on a clear, dry, and cool (not freezing) day.

Enjoy the color, it only occurs for a brief period each fall.

Life Cycle of A Mosquito (Practical IX Class Biology)


Our objective is to study the life cycle of a mosquito.

The Theory

The mosquitoes are a family of small, midge-like flies. Like all flies, mosquitoes go through four stages in their life – egg, larva, pupa, and adult. We call this as the life cycle.  Each of these stages is morphologically different from the other, with even the habitat of each stage differing. The first three stages – egg, larva and pupa are largely aquatic, whereas the adult stage is aerial.

Mosquito Life cycle

We will now look at the four distinct stages of development in the life cycle of a mosquito.

Stage 1 – Egg

The eggs are laid one at a time and they float on the surface of the water. Normally the eggs are white when first deposited, then darken to near black within a day. They hatch in one to three days depending on the temperature. Eggs left on moist soil can last for up to a year, until the ground is flooded again, before hatching.

In the case of Culex and Culiseta species, 200-300 eggs are stuck together in rafts. Anopheles and Aedes species do not make egg rafts but lay their eggs separately. Culex, Culiseta, and Anopheles lay their eggs on water while Aedes lay their eggs on damp mud. The eggs generally do not hatch until the place is flooded. Most eggs hatch into larvae within 48 hours. When the larvae are ready to hatch, they use a small temporary ‘tooth’ on their head to break open the egg along a suture that was made by it.

Stage 2 – Larva

Mosquito larvae, commonly called ‘wigglers’ or ‘wrigglers’, live in water from 7 to 14 days depending on the water temperature. Larvae swim either through propulsion with their mouth brushes, or by jerky movements of their entire bodies, giving them the common name of ‘wigglers’. The larva begins to feed on bacteria and decaying organic matter on the water surface, soon after they hatch out of eggs. They spend most of their time hanging upside down at the surface, sucking in oxygen through the siphon. The siphon is located at the base of their abdomen and is similar to a snorkel. Brushes that are located in front of their mouths collect the food. Anopheles larvae do not have a siphon and they lay parallel to the water surface. The larval stage lasts for a few days to a few weeks, during which the larvae shed several layers of their outer skin, called moulting. This allows further growth.

Stage 3 – Pupa

After the larvae have completed moulting, they become pupae. This is the stage in which they undergo metamorphosis to become an adult mosquito. The pupal stage is a resting, non-feeding stage. Mosquito pupae are commonly called ‘tumblers’. The pupa is lighter than water and therefore floats at the surface. The mosquito pupa is comma-shaped. The head and thorax are merged into a cephalothorax, with the abdomen curving around underneath. At one end of these curved bodies is the large head and at the other end is the flippers used for swimming. They must take in oxygen from time to time through two breathing tubes known as ‘trumpets’. After a few days or longer, depending on the temperature and other circumstances, the pupa rises to the water surface, the dorsal surface of its cephalothorax splits, and the adult mosquito emerges.

Stage 4 – Adult

The newly emerged adult rests on the surface of the water for a short time to allow itself to dry and harden its parts. Also, the wings have to spread out and dry properly before it can fly.

Adult mosquitoes have a head with two large compound eyes, a thorax, a pair of scaled wings and six jointed legs. They also have antennae and a proboscis. Adult mosquitoes mate within the first few days after emerging from the pupal stage.

It is the carbon dioxide that we exhale, and the lactic acid from our sweat that combine to make us smell like a mosquito buffet. Mosquitoes can pick up these smells from 100 feet, and they can also feel our body heat and notice movements.

Only female mosquitoes have the mouth parts necessary for sucking blood. When biting with their proboscis, they stab two tubes into the skin, one is an anti-coagulant to keep the blood flowing and is a mild painkiller that helps them escape detection, the other helps to suck blood. They use the blood not for their own nourishment but as a source of protein for their eggs. For food, both males and females eat nectar and other plant sugars.

Some interesting mosquito facts

  • There are over 2500 different species of mosquitoes.
  • The feeding habits of mosquitoes are quite unique in that it is only the adult females that feed on blood. The male mosquitoes feed only on plant juices.
  • Mosquitoes must have water in which to complete their life cycle.
  • Most female mosquitoes need to feed on animal blood before they can develop eggs.
  • A female can produce up to 500 eggs before she finally dies.
  • Mosquitoes don’t travel more than a mile from the place where they were hatched.
  • The length of life of the adult mosquito usually depends on factors like – temperature, humidity, sex of the mosquito and time of the year.
  • Once mosquitoes emerge from their pupal cocoons and take flight, male mosquitoes last less than a week and the females’ maybe a couple of months.

Learning Outcomes

  1. Students understand the different stages of a Mosquito life cycle.
  2. Students get to know different types of Mosquitoes and the diseases spread by them.
  3. Students understand the differences in each stage of the mosquito life cycle through the animated demonstrations.

A public health agency in Finland is using an interesting approach to shock teens into not smoking

The Tobacco Body website features an interactive image of a man and a woman. Users zoom in and out of their body parts to observe the effects smoking has on a male and female body.

This is a new campaign by the Cancer Society of Finland, whose objective, according to the website of their ad agency, is to use this as a tool to show teenagers “to think critically about smoking.” The idea is to move beyond the black lungs, gooey tar and damaged livers, and use technology to “make the shock effect more shocking.”

And pretty shocking it is. Before-lady and Before-man are indeed much better-looking than After-lady and the After-man.

The strategy employed is clear: teens today don’t care about lungs, livers and cancer, or if they do, the constant exposure to such warnings has rendered them ineffective. What they do care about is appearances. So let’s show them how ugly smoking makes them.

On one hand you can’t argue with facts: smoking does give you spots, increase your testosterone levels, give you bad breath and unhealthy hair, yellow your teeth and nails, etc. Fact-wise there’s not much to dispute in the Tobacco Body website. But how advisable is it to resort to telling teenagers what is beautiful/popular/acceptable and what is not, even if it is towards the noble cause of telling them to not smoke?

Sample these snippets taken from the website:

[Man & Woman] “Dear Smoker, we’re sorry to inform you that according to nail fashion experts, nicotine yellow is not this season’s colour.”

[Woman] “Hey non-smoking girl, you are on a wonder-diet and you don’t even know it! Your body shape is closer to the average, whereas research shows that smokers weigh more and are rounder around the abdominal area.”

[Woman] “The non-smoking woman is less-likely to have as much hair growing on her arms as a smoker.”

[Woman] “The non-smoking woman usually has no additional hairs growing under her nose… No need for a five-bladed special razor.”

[Man & Woman] “Smokers have bad breath. As many as 20 per cent of people have ended relationships because of smoking. In Burn Magazine’s interviews several celebrities reveal they prefer kissing non-smokers.”

[Man & Woman] “A weary face is not a popular one: out of the 100 most popular profile pictures in a dating service only 2 were pictures of smokers.”

Basically, the Cancer Society of Finland is telling youngsters that smoking makes you hairy, fat, yellow-toothed and gives you bad breath. I found it slightly bothersome how features that are quite normal in several healthy teenagers, like rounded abdomens and hair on arms (for women), was being grouped with those which are blatantly undesirable and unhealthy, like yellowing teeth, bad breath and damaged lungs.

I wondered if this ad could be sending negative body image messages to kids who are naturally fat or hairy – are they implying that these kids are not as desirable?

But the more I thought about it the harder I realised it was to completely buy into that line of reasoning. Because, as a friend pointed out, this may be a case where the end could perhaps justify the means.

It was different in the case of the Dove ‘You’re more beautiful than you think you are’ campaign which also used a similar strategy to sell their product. They too inadvertently (?) went about setting definitions for beauty. The glaring difference of course was that Dove, at the end of the day, was trying to sell us soap under the guise of the noble motive of wanting women to feel good about themselves.

In the case of Tobacco Body, there’s no such deception. As questionable as their strategy might be, we can probably be sure that all this campaign wants is for teenagers to say no to smoking. They are, after all, the Cancer Society of Finland.

ScreenHunter_15 Oct. 18 13.27


The Mechanism of Muscle Contraction

1) The sequence of events leading to contraction is initiated somewhere in the central nervous system, either as voluntary activity from the brain or as reflex activity from the spinal cord.

(2) A motor neuron in the ventral horn of the spinal cord is activated, and an action potential passes outward in a ventral root of the spinal cord.

(3) The axon branches to supply a number of muscle fibers called a motor unit, and the action potential is conveyed to a motor end plate on each muscle fiber.

(4) At the motor end plate, the action potential causes the release of packets or quanta of acetylcholine into the synaptic clefts on the surface of the muscle fiber.

(5) Acetylcholine causes the electrical resting potential under the motor end plate to change, and this then initiates an action potential which passes in both directions along the surface of the muscle fiber.

(6) At the opening of each transverse tubule onto the muscle fiber surface, the action potential spreads inside the muscle fiber.

(7) At each point where a transverse tubule touches part of the sarcoplasmic reticulum, it causes the sarcoplasmic reticulum to release Ca++ ions.

(8) The calcium ions result in movement of troponin and tropomyosin on their thin filaments, and this enables the myosin molecule heads to “grab and swivel” their way along the thin filament. This is the driving force of muscle contraction.

Contraction is turned off by the following sequence of events:

(9) Acetylcholine at the neuromuscular junction is broken down by acetylcholinesterase, and this terminates the stream of action potentials along the muscle fiber surface.

(10) The sarcoplasmic reticulum ceases to release calcium ions, and immediately starts to resequester all the calcium ions that have been released.

(11) In the absence of calcium ions, a change in the configuration of troponin and tropomyosin then blocks the action of the myosin molecule heads, and contraction ceases.

(12) In the living animal, an external stretching force, such as gravity or an antagonistic muscle, pulls the muscle back to its original length.

Pituitary Gland – Endocrine System.

In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 grams (0.018 oz) in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity (sella turcica) covered by a dural fold (diaphragma sellae). The posterior pituitary gland is functionally connected to the hypothalamus by the median eminence via a small tube called the pituitary stalk, (also called the infundibular stalk or the infundibulum). The pituitary gland sits in the hypophysial fossa, situated in the sphenoid bone in the middle cranial fossa at the base of the brain. The pituitary gland secretes nine hormones that regulate homeostasis.


The pituitary gland is a pea-sized gland that sits in a protective bony enclosure called the sella turcica. It is composed of three lobes: anterior, intermediate, and posterior. In many animals, these three lobes are distinct. However, in humans, the intermediate lobe is but a few cell layers thick and indistinct; as a result, it is often considered part of the anterior pituitary. In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary. It belongs to the diencephalon.


Main article: Anterior pituitary

The anterior pituitary arises from an invagination of the oral ectoderm and forms Rathke’s pouch. This contrasts with the posterior pituitary, which originates from neuroectoderm.

Endocrine cells of the anterior pituitary are controlled by regulatory hormones released by parvocellular neurosecretory cells in the hypothalamus. The latter release regulatory hormones into hypothalamic capillaries leading to infundibular blood vessels, which in turn lead to a second capillary bed in the anterior pituitary. This vascular relationship constitutes the hypothalamo-hypophyseal portal system. Diffusing out of the second capillary bed, the hypothalamic releasing hormones then bind to anterior pituitary endocrine cells, upregulating or downregulating their release of hormones.

The anterior pituitary is divided into anatomical regions known as the pars tuberalis, pars intermedia, and pars distalis. It develops from a depression in the dorsal wall of the pharynx (stomodial part) known as Rathke’s pouch.


Main article: Posterior pituitary

The posterior lobe develops as an extension of the hypothalamus. The magnocellular neurosecretory cells of the posterior side possess cell bodies located in the hypothalamus that project axons down the infundibulum to terminals in the posterior pituitary. This simple arrangement differs sharply from that of the adjacent anterior pituitary, which does not develop from the hypothalamus. The release of pituitary hormones by both the anterior and posterior lobes is under the control of the hypothalamus, albeit in different ways.

Intermediate lobe

Although rudimentary in humans (and often considered part of the anterior pituitary), the intermediate lobe located between the anterior and posterior pituitary is important to many animals. For instance, in fish, it is believed to control physiological color change. In adult humans, it is just a thin layer of cells between the anterior and posterior pituitary. The intermediate lobe produces melanocyte-stimulating hormone (MSH), although this function is often (imprecisely) attributed to the anterior pituitary.

The intermediate lobe is, in general, not well developed in tetrapods, and is entirely absent in birds.

Variations among vertebrates

The pituitary gland is found in all vertebrates, but its structure varies between different groups.

The division of the pituitary described above is typical of mammals, and is also true, to varying degrees, of all tetrapods. However, only in mammals does the posterior pituitary have a compact shape. In lungfishes, it is a relatively flat sheet of tissue lying above the anterior pituitary, and, in amphibians, reptiles, and birds, it becomes increasingly well developed. The intermediate lobe is, in general, not well developed in tetrapods, and is entirely absent in birds.

Apart from lungfishes, the structure of the pituitary in fish is generally different from that in tetrapods. In general, the intermediate lobe tends to be well developed, and may equal the remainder of the anterior pituitary in size. The posterior lobe typically forms a sheet of tissue at the base of the pituitary stalk, and in most cases sends irregular finger-like projection into the tissue of the anterior pituitary, which lies directly beneath it. The anterior pituitary is typically divided into two regions, a more anterior rostral portion and a posterior proximal portion, but the boundary between the two is often not clearly marked. In elasmobranchs there is an additional, ventral lobe beneath the anterior pituitary proper.

The arrangement in lampreys, which are among the most primitive of all fish, may indicate how the pituitary originally evolved in ancestral vertebrates. Here, the posterior pituitary is a simple flat sheet of tissue at the base of the brain, and there is no pituitary stalk. Rathke’s pouch remains open to the outside, close to the nasal openings. Closely associated with the pouch are three distinct clusters of glandular tissue, corresponding to the intermediate lobe, and the rostral and proximal portions of the anterior pituitary. These various parts are separated by meningial membranes, suggesting that the pituitary of other vertebrates may have formed from the fusion of a pair of separate, but associated, glands.

Most armadillos also possess a neural secretory gland very similar in form to the posterior pituitary, but located in the tail and associated with the spinal cord. This may have a function in osmoregulation.

There is a structure analogous to the pituitary in the octopus brain.

Hormones secreted


The anterior pituitary synthesizes and secretes the following important endocrine hormones:


  • Growth hormone (also referred to as ‘Human Growth Hormone’, ‘HGH’ or ‘GH’ or somatotropin), released under influence of hypothalamic Growth Hormone-Releasing Hormone (GHRH), (also known as growth-hormone-releasing factor (GHRF)); inhibited by hypothalamic somatostatin


  • Thyroid-stimulating hormone (TSH), released under influence of hypothalamic Thyrotropin-releasing hormone (TRH) (or TRF); inhibited by somatostatin


  • Adrenocorticotropic hormone (ACTH), released under influence of hypothalamic Corticotropin-Releasing Hormone (CRH), (or CRF)
  • Beta-endorphin, released under influence of hypothalamic Corticotropin-Releasing Hormone (CRH)or (CRF)[5]


  • Prolactin (PRL), also known as ‘Luteotropic’ hormone (LTH), whose release is inconsistently stimulated by hypothalamic TRH, oxytocin, vasopressin, vasoactive intestinal peptide, angiotensin II, neuropeptide Y, galanin, substance P, bombesin-like peptides (gastrin-releasing peptide, neuromedin B and C), and neurotensin, and inhibited by hypothalamic dopamine.[6]


  • Luteinizing hormone (also referred to as ‘Lutropin’ or ‘LH’).
  • Follicle-stimulating hormone (FSH), both released under influence of Gonadotropin-Releasing Hormone (GnRH)

These hormones are released from the anterior pituitary under the influence of the hypothalamus. Hypothalamic hormones are secreted to the anterior lobe by way of a special capillary system, called the hypothalamic-hypophysial portal system.


The posterior pituitary synthesizes and secretes the following important endocrine hormones:

Magnocellular Neurons:

  • Antidiuretic hormone (ADH, also known as vasopressin and AVP, arginine vasopressin), the majority of which is released from the supraoptic nucleus in the hypothalamus
  • Oxytocin, most of which is released from the paraventricular nucleus in the hypothalamus. Oxytocin is one of the few hormones to create a positive feedback loop. For example, uterine contractions stimulate the release of oxytocin from the posterior pituitary, which, in turn, increases uterine contractions. This positive feedback loop continues throughout labour.


The intermediate lobe synthesizes and secretes the following important endocrine hormone:

  • Melanocyte–stimulating hormones (MSHs), although this function is often (imprecisely) attributed to the anterior pituitary. These are sometimes called “intermedins,” as these are released by the pars intermedia.


Hormones secreted from the pituitary gland help control the following body processes:

  • Growth (Excess of HGH can lead to gigantism and acromegaly.)
Compared with the hand of an unaffected person (left), the hand of someone with acromegaly (right) is enlarged.
  • Blood pressure
  • Some aspects of pregnancy and childbirth including stimulation of uterine contractions during childbirth
  • Breast milk production
  • Sex organ functions in both males and females
  • Thyroid gland function
  • The conversion of food into energy (metabolism)
  • Water and osmolarity regulation in the body
  • Water balance via the control of reabsorption of water by the kidneys
  • Temperature regulation
  • Pain relief

Diseases involving the pituitary gland

Main article: Pituitary disease

Some of the diseases involving the pituitary gland are:

  • Hyperpituitarism, the increased (hyper) secretion of one or more of the hormones normally produced by the pituitary gland.
  • Hypopituitarism, the decreased (hypo) secretion of one or more of the hormones normally produced by the pituitary gland. If there is decreased secretion of most pituitary hormones, the term panhypopituitarism (pan meaning “all”) is used.
  • Pituitary tumours.
  • Pituitary adenomas, noncancerous tumors that occur in the pituitary gland.

Magnifying the Universe…..


This interactive infographic from Number Sleuth accurately illustrates the scale of over 100 items within the observable universe ranging from galaxies to insects, nebulae and stars to molecules and atoms. Numerous hot points along the zoom slider allow for direct access to planets, animals, the hydrogen atom and more. As you scroll, a handy dial spins to show you your present magnification level.

While other sites have tried to magnify the universe, no one else has done so with real photographs and 3D renderings. To fully capture the awe of the vastly different sizes of the Pillars of Creation, Andromeda, the sun, elephants and HIV, you really need to see images, not just illustrations of these items. Stunningly enough, the Cat’s Eye Nebula is surprising similar to coated vesicles, showing that even though the nebula is more than 40,000,000,000,000,000,000,000 times larger, many things are similar in our universe.

We hope you have a blast magnifying the universe, know that each time you zoom in a depth, you’re magnifying the universe 10x … and every time you zoom out, the bigger objects are 1/10th of their prior size. If you zoom from the biggest object, The Observable Universe (8.8 x 10E26 … or 880,000,000,000,000,000,000,000,000m across), all the way down to the hydrogen atom’s proton nucleus (1.7 x 10E-15 … or 0.0000000000000017m across), you will have zoomed in over 100,000,000,000,000,000,000,000,000,000,000,000,000,000x! Unbelievable isn’t it? Our universe really is immensely massive and surprisingly small.

How To Use:

Step 1:
To experience this interactive infographic in full screen (our recommendation) click the “Full Screen” button in the top right corner of the infographic.

Step 2:
Choose one of nine starting points by moving your mouse over and clicking one of the 9 images (atoms, animals, buildings, mountains, planets, stars, nebulae, galaxies and the observable universe).

Step 3:
Now on the bottom of the infographic, there is a blue blue dot that you can click on with your mouse.Drag the blue circle left to go “up” in size and drag the blue circle right to go “down” in size

Step 4:
To relocate to one of the nine entry points, click the corresponding yellow dot on the scroller at the bottom of the page


You can view a list of image credits used in the construction of this infographic by clicking here.

Produced for Number Sleuth by Science is Beautiful in coordination with Mandril Design and Killer Infographics.

<br />Copyright 2012.  <a href=”http://www.numbersleuth.org/universe/”>Magnifying the Universe</a>  by <a href=”http://www.numbersleuth.org”>Number Sleuth</a>.

Insulin Administration…

Insulin is necessary for normal carbohydrate, protein, and fat metabolism. People with type 1 diabetes mellitus do not produce enough of this hormone to sustain life and therefore depend on exogenous insulin for survival. In contrast, individuals with type 2 diabetes are not dependent on exogenous insulin for survival. However, over time, many of these individuals will show decreased insulin production, therefore requiring supplemental insulin for adequate blood glucose control, especially during times of stress or illness.

An insulin regimen is often required in the treatment of gestational diabetes and diabetes associated with certain conditions or syndromes (e.g., pancreatic diseases, drug- or chemical-induced diabetes, endocrinopathies, insulin-receptor disorders, certain genetic syndromes). In all instances of insulin use, the insulin dosage must be individualized and balanced with medical nutrition therapy and exercise.

This position statement addresses issues regarding the use of conventional insulin administration (i.e., via syringe or pen with needle and cartridge) in the self-care of the individual with diabetes. It does not address the use of insulin pumps. (See the American Diabetes Association’s position statement “Continuous Subcutaneous Insulin Infusion” for further discussion on this subject.)