The human skeleton is comprised of bones, fused or individual. These bones are also supported by ligaments, muscles, tendons, and cartilage. Ligaments are tough, fibrous, dense connective tissues which fasten two bones together to form a joint. The muscles are used to maintain the bones in a good posture, and they are also needed for movement. The muscles are connected to the bones with tendons. Tendons are another types of tough, fibrous connective tissue, which unlike the ligaments who join bones, they join the muscles to the bones. Cartilage is a stiff, but still flexible connective tissue, whose main function is to prevent bone on bone rubbing. Cartilage also makes up certain parts of our body such as our nose, and ears. The actual bones are not logs of solid, but are logs with a honey-combed interior, which is what makes them so light and yet very hard. The outside of the bones, where the blood vessels attach themselves, is called the periosteum. The layer that we see, the white, smooth outside, is called the compact bone. Within this compact bone, there are many layers of cancellous bone, which resembles a sponge, or honeycomb. In most bones, these cancellous layers protect the innermost of the bone, the bone marrow. This is where the cells are created.

The skeletal system serves many purposes. It has many main functions:
1. Structure: the skeleton maintains our body in place, like a wire on which a sculptor places strips of clay. Without the skeleton, our muscles, veins, arteries, and organs would have nothing to hold themselves to, and we would be heaps of meat unable to move.
2. Movement: the joints (where bones are connected with ligaments) and skeletal muscles allow certain bones to move in a certain way. We can do all our movement because of the skeleton and the nervous system which has control over the movement.
3. Protection: the skeleton protects a variety of organs and tissues such as:
-The skull protects the brain, and the eyes.
-The ribcage, spine and sternum protect the heart, lungs, and major blood vessels.
-The spine protects the spinal cord.
The skeleton also protects the digestive system, the ankles, the wrists, etc.
4. Blood Cell Production and Storage: the bones create red and white blood cells as well as storing minerals.

Left: Male, Right: Female

Skeletons of each individual differ slightly. When a baby is born, s/he contains approx. 270 bones, but as the child develops, many bones fuse together, creating less bones. An average adult contains 206 bones. There are also differences between male and female skeletons, as they do not require to do the same actions. The female body has a flatter, larger, and slightly rounder pelvis in order to allow the head of the fetus to pass during childbirth. Even so, the pelvis widens even more during childbirth, which tells osteologists (scientists studying bones), whether the skeleton found on an excavation was a woman, and if she was a mother. Woman also have narrower ribcages and less pronounced cranial features. Men seem to have thicker, and longer limbs and digit bones.

Reference: http://en.wikipedia.org/wiki/Human_skeleton, http://en.wikipedia.org/wiki/Tendon, http://en.wikipedia.org/wiki/Skeletal_muscle, http://en.wikipedia.org/wiki/Ligament, http://en.wikipedia.org/wiki/Bone, http://wiki.answers.com/Q/What_is_the_name_of_a_scientist_that_studies_bones, http://kidshealth.org/kid/htbw/bones.html#, http://en.wikipedia.org/wiki/File:Human_skeleton_front_en.svg, http://en.wikipedia.org/wiki/File:Human_skeleton_back_en.svg, http://hippie.nu/~unicorn/tut/xhtml/

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Metabolism is a term used to describe chemical reactions in cells. In all chemical reactions there are the reactants (chemicals which react with each other), and the product (what you end up with at the end of the reaction).
There are two main sorts of chemical reactions: Anabolic and Catabolic. Anabolic means the reaction creates more complex molecules from much simpler molecules. Eg: using letters ‘a’ and ‘b’, A+B=AB. Catabolic means the opposite, using very complex molecules and breaking them down into simpler molecules. Eg: using letters ‘a’ and ‘b’, AB–>A + B.
Anabolic reactions usually need some energy to start reacting, whereas Catabolic reactions usually release energy. Metabolic activity doesn’t happen spontaneously, it needs what is called an activation energy. However, sometimes the energy needed can too much for the cells to tolerate. Usually, the activation energy is heat energy, but reactions sometimes need a huge amount of heat to start, a heat so great that the cells would not survive it. To resolve this problem, cells have enzymes. Enzymes are long chains of Protein, but the long chains fold over one an other the create a very specific shape. Without the right shape, enzymes cannot work. Here is an analogy which should help you understand:

Chemical Reaction Analogy

Imagine a hill with a little crater at the top. Within this crater is a boulder. You want to push the crater out so it can roll down (releasing energy) and shatter into smaller pieces (Catabolic Reaction). You have to push the boulder up over the crater’s edge first however (activation energy), and this will take a lot of time and strength to do. So you are given a sturdy spade (enzyme). Using this spade, you can reduce the ridge, and thus reducing the distance you have to push (reducing activation energy needed).

There are also many factors which affect chemical reactions and enzymes. Two main factor would be temperate and pH. Back to our analogy, an affecting factor could be the rain. If it is raining, the spade (enzyme) will not work properly, with the water turning the dirt to mud. The mud would be very liquid and the spade will not successfully be able to clear away everything. Eventually, the little crater at the top would fill with mud, and then it will harden, making the pushing of the boulder over the edge (chemical reaction) impossible.
For the temperature factor:
If the temperature rises, then it is more heat as activation energy and more reactions take place. However, if the temperature continues to rise, the enzymes become denatured, i.e., they are malformed, and therefore cannot operate any longer. There is at first there is an increase in reactions, but then the number rapidly decreases as the enzymes are denatured.
The other factor is the pH. Every enzyme has a certain pH point at which they work the best. If the pH goes up or down, the enzyme will work less properly until it will stop working altogether. Imagine the spade we talked about earlier being bent back more and more until eventually it is bent all the way back to the handle, making it useless.

And that is all about enzymes and chemical reactions.

Reference: http://www.folens.ie/catalog/book_detail.php?bookid=91, http://www.omahonys.ie/catalog/product_info.php?products_id=115286, Image from me.

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Cells are what could be called the building blocks of life. They are the smallest units of life. Cells are considered to be living things. All organisms are built up with cells. Some organisms are said to be unicellular, meaning the organism is one cell, such as bacteria. All living things come from just one cell which ‘reproduced’. Cells divide themselves into two exact replicas to be able to multiply. There are two different types of cells: Animal and Plant cells. These two differ because the organisms do not need or do the same things. And there are also different sub-categories of cells. Each group of cells is unalike. A cheek cell is not the same as a blood cell. However, there is a generalisation in what most plant cells look like and the same for animal cells.

Plant Cell

Cell Wall: this is what gives the plant cell a straight shape. It decides what can come into the cell and what can’t, also what can or can’t come out. Animal cells do not have this.

Nucleus: this is basically the ‘brain’ of the cell. It is a control centre. This is where DNA (Deoxyribonucleic Acid) is found. The nucleus decides what chemicals the cell will make and also how the cell will divide.

Cytoplasm: this is the watery substance in which everything is suspended. This is also where all the chemical reactions take place.

Animal Cell

Chloroplast: this contains chlorophyll which is the necessary component plants need to make food. Animal cells do not have these.

Cell Membrane: This is like a skin around the cell which protects it and also acts as a guard, only allowing some chemicals into the cell.

Vacuole: this is just a storage space within the cell. Animal cells have much smaller ones than plants.

Did you know that the name ‘cell’ was derived from the Latin cellula, meaning ‘small room’? The name was coined by Robert Hooke, when he was examining Cork Oak under a microscope. He described the cells as small rooms which resembled the ones monks used to live in.

Reference: http://en.wikipedia.org/wiki/Cell_(biology), http://www.folens.ie/catalog/book_detail.php?bookid=527 , http://www.folens.ie/catalog/book_detail.php?bookid=91. Pictures from me.

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All living things need food. Food provides energy, the raw materials necessary for building and repairing the body, and food is also needed to control the chemical reactions in cells (meaning to control the metabolism). Food is made up of chemical components, which are made up of molecules, which are made up of atoms. There are four major types of molecules when mixed in different proportions create different types of food. Carbohydrates, Lipids, Proteins, and Vitamins are the four major types of molecules found in food.

Carbohydrates: there are three different types of carbohydrates that occur in nature.
1: Monosaccharides: these are more often named as simple sugars. Examples include fructose and glucose (found in fruit). They are called simple sugars because they consist of only one molecule, instead of groups of molecules joined together.
2: Disaccharides: these are a bit more complex than simple sugars (monosaccharides). Instead of one molecule, there are two molecules joined together. Examples are sucrose (cane sugar) and lactose (milk).
3: Polysaccharides: this consist of many molecules joined together. Examples are starch (bread) and cellulose (vegetables).
In respiration (see the 7 characteristics of life), carbohydrates break down and release energy, waste (carbon dioxide) and water. This type of reaction is called a catabolic reaction i.e. a complex molecule broken down into simpler molecules. The opposite, anabolic reaction, means a simple molecule built up into a complex molecule. Plants use this reaction to make their food.

Lipids: these are better known as fats and oils. Fats and oils are basically the same, except one is solid (fats e.g. butter) and the other one is liquid (oils e.g. sunflower oil). Lipids are important storage molecules. They provide insulation by depositing under the skin, and they protect the internal organs. Also, oils secreted from the skin help to waterproof the body.

Proteins: protein molecules are made up of sub-units called amino acids. These can be linked and they can form many different types of protein. Think of these amino acids as letters of the aphabet: when joined together, they form many different words. These amino acids are joined by what is called peptide links or bonds. Proteins can be found in muscle, hair, and nails. Enzymes, which are molecules who control chemical reactions in cells, are made from proteins. Hormones, which control and regulate body functions, are also made from proteins.

Vitamins: there are six different vitamins.
Vitamin A: these promote healthy eyes and eye sight and are mainly found in liver and carrots.
Vitamin B: there are eight sub sections of vitamins within this vitamin group, but they are all for mainly healthy skin and enhancing the immune and nervous systems. They can be found in pulses (beans, lentils), and meat such as liver and tuna.
Vitamin C: this is for good, healthy, strong connective tissue. It is mainly found in citrus fruits, but also in liver.
Vitamin D: this helps the absorption of calcium, which helps the bones and teeth grow. In a way, it indirectly helps the bones and teeth grow. It can be found in dairy products, but the skin also produces it when exposed to sunlight.
Vitamin E: these promote a healthy heart. They can be found in dairy products and in green leafy vegetables (e.g. spinach).
Vitamin K: this vitamin helps the blood to clot properly. It can be found in green leafy vegetables such as spinach, or cabbage.

Sources: New Senior Biology, Wikipedia,

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There are many things needed to do to be able to properly study an ecosystem. There are different parts of the ecosystem that are to be studied. There is the animal part, the plant part, and the abiotic (non-living) part. Studying ecosystems can answer some of these questions:
-What organisms are present?
-What organisms live in what part of the ecosystem?
-Who eats what and what eats them?
-What abiotic factors are important?
To make a good, structured, detailed study, there are some steps recommended to do. These steps can vary depending on what ecosystem you are studying. You will not have to check water salinity in desert.

1. Making a Map: this is useful to then mark off certain things found in what areas. Even easier if done in bird’s-eye-view. (squiggly line for path, small circle for tree etc.)
2. Observe and Collect: look around at the different animals and plant visible. Then collect samples of these organisms to bring back to your lab. Note: not all studying of ecosystems is done entirely in the field, sometimes almost as much time is spent outside than inside.
3. Analyse and Name: using a key, which is a simple set of yes/no questions which ask questions such as “Less than four legs? or More than four legs?”. Organisms can be identified using this key. For trees and plants, the leaves can be used to identify the plant.
4. Observe and Collect Abiotic Factors: look at factors such as the air, soil, water temperature, oxygen presence in water and soil, light intensity, and much more. Samples of soil and water can be collected to conduct different tests.
5. Distribution: this means that you can try to determine the percentage of organisms present in an ecosystem. Random sampling can be used to do this. Using a quadrat (relatively big empty frame, usually wooden planks nailed together), you can place this randomly in different areas and note the different organisms contained within the frame, and later calculate an average on all the notes.

There are many different objects (apparatus) used to carry out these steps easier and faster. For collecting animal samples, this can be used:

Net

Cryptozoic Trap: A piece of wood or stone laid on the ground and after some time, small insects could be found underneath.
Nets: Lots of different nets exist that have been adapted to catch certain organisms. e.g. fish net, plankton net.

Tullgren Funnel

Tullgren Funnel: This is to extract insects from soil. A soil sample is placed on a wire gauze which is over a funnel which leads into a beaker with a mixture of alcohol and water. There is a strong light held over the soil for the necessary amount of time. The light gradually dries out the soil, driving the insects within it to go downward until eventually reaching the beaker of liquids.

Pooter

Pooter: A small beaker beaker with two separate tubes leading out. one tube is covered with a wire gauze on the inside of the beaker. Inhale through this tube while placing to other one over small insect to suck the insect into the beaker.

Thermometers: Lots of different thermometers exist to measure the heat of different things. Different thermometers even exist to measure the heat of the same thing.

Images from: http://bohart.ucdavis.edu, http://www.blackrockec.ie, http://herbarium.usu.edu

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A population is a group of individuals of the same species living together in the same habitat at any given time. Many organisms live in populations for the reasons that it is safer when there are more of them, it is easier to find a mate, and food and shelter may be abundant in the habitat, bringing the organisms to live in that habitat, subsequently making them live with each other.

Biologists study populations for many reasons. They can find out what factors affect populations, they help in the conservation of endangered animals, or even warn against killing certain animals who are starting to become endangered. The size of the population is affected by these factors:

Two male deers competing.

1. Competition
2. Predation
3. Parasitism

Competition is when two or more organisms ‘fight’ or ‘compete’ each other for the same resource. For example, plants could compete for sunlight, food, and soil. Animals could compete for mates, territory or food. A shortage of a needed resource could increase the competition between organisms, and some of the losers may even starve to death if the resource is food. There are two recognised types of competition. There is contest competition and scramble competition. Contest competition is when a physical fight or confrontation is involved. Deer do this by locking their antlers together and pushing, and the one who gives in is the loser. Scramble competition is when each organism competing tries to gather the most of the resource available for itself. For example, birds do this during spring when they have chicks to feed. The parents try collecting as much as possible food before other parents do.

A cheetah has captured it's prey.

Predation is when an organism kills another organism for food. The predator, the killer, has many tricks up it’s sleeves (called adaptations) to capture the prey, the victim. For example, the cheetah has a lot of speed to capture it’s prey, and it’s spotty coat camouflages in it’s environment. They can have good eyesight, good hearing, or even the perfect teeth for biting and chewing the sort of food they capture. Some predators hunt in groups, and some migrate to another area where food is more bountiful, where as other predators would simply change their diet. Preys also have adaptations to protect themselves. Some plants use thorns and spikes to ward off predators.

Adult roundworm infestation in intestines.

Some animals use a camouflage colour, and others use a warning colour. A warning colour is a bright colour, sometimes red, used to ward off predators because the bright, vivid colour is usually associated with bad taste. Some preys even actually have a bad taste.

Head lice close-up.

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Ecology is the study of the interaction between living things and their environment. The environment of an organism includes the living and non-living factors. For example, a frog’s environment would include the living parts: the flies it eats, the plants it uses as shelter, it’s fellow frogs, etc, and the non-living parts: the water temperature, the amount of minerals, the sun, the humidity. An ecosystem is a group organisms and their environment, i.e. ecology is the study of ecosystems. The earth itself is a great big ecosystem, although not all of it can sustain life. The parts of the earth where life can grow is called the biosphere. The living part of an ecosystem is called the biotic component. The different organisms within that group can then be organised in an other subsection group. There are
1. Producers, which make their own food, e.g. plants
2. Consumers, they feed on other plants and animals, e.g. fox
3. Decomposers, they feed on dead and decaying plants and animals, e.g. fungi
The term abiotic refers to the non living in an ecosystem.

Example of Grazing Food Chain (taken from New Senior Biology)

Example of Detritus Food Chain (taken from New Senior Biology)

The primary source of energy is the sun. All organisms need energy to live. Organisms pass down energy using feeding relationships. The producers absorbe the sun’s energy to make their food. These producers are then eaten by the primary consumers (herbivores), who in turn are eaten by the secondary consumers (carnivores), who are then eaten by the tertiary consumers (top carnivores). We use food chains to describe the feeding relationship and passing down of energy from one organism to the next. An example of a food chain would be: (Sun–>) Grass–> Rabbit–> Fox . The sun is always the beginning of the food chain, but since it always where the producer gets it’s energy, it is not noted when food chains are written.  There are two types of food chains, a grazing food chain and a detritus food chain. The grazing food chain is when a primary consumer eats a live plant, and a detritus food chain is when the primary consumer eats detritus (dead organisms). In nature, food chains can interconnect, and two or more interconnecting food chains are then called food webs.

When the plant (producer) takes in energy from the sun, it is used for food and new cells. However, most of the energy escapes as heat. This means that the primary consumer does not get all the energy, and after a while, the sun’s energy has been completely used. Out of all the energy absorbed by the plant, only 10% is used for growth and food. And when the plant gets eaten, only 10% of the plant’s absorbed energy gets taken in, i.e. animal gets 10% of the 10% of the sun’s energy the plant used for growth and food. This continues, each animal passing down less energy than what they received, until eventually, no more energy can be passed down. This means that food chains cannot contain more than four or five levels. This flow of energy is called trophic levels. In food chains, the further you get, the less organisms there are in the species. There are less animals as you go up because the energy available to the tertiary consumer is less than that available to the producers, i.e. the tertiary consumer doesn’t have enough energy available to produce more of its species, to sustain it’s self it has to eat a lot of secondary consumers, who ate a lot of primary consumers, who as well ate a lot of producers.

References: New Senior Biology, Wikipedia

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What is life? This is what scientists have been asking themselves for years. Now, to determine if something is alive or not, characteristics of life have been developed. For something to be considered alive, that something must have all the characteristics, not just one or two. If it does have all the characteristics, it is called an organism.

There are many different versions of these characteristics available, which doesn’t make sense. I compiled a list by comparing the many lists I saw. This is what I believe to be an ultimate list from several lists.

1. Organisation: This characteristic doesn’t mean that living things should be organised in their daily life but chemically. They have to be composed of atoms, which form molecules, which form cells.  Similar cells put together make a tissue, and two or more tissues make organs. Organs then make a system. A living thing doesn’t have to have a system, but at least one cell. These are called unicellular organisms (e.g. Amoeba). If the living thing has more than one cell, it is called a multicellular organism (e.g. Cat, Human).

Example: Muscle cells->Muscle Tissue->Heart (an organ made up of muscle tissue)->Circulatory System (Lungs and Heart and Blood Vessels working together)

2. Growth: All living things should be able to gather resources to use them to make their cells bigger, making their entire system enlarge.

3. Reproduction: All living things should be able to create another of its species. If it couldn’t, species would not be able to survive because no young would be born to keep the species going. There are two kinds of reproduction: asexual and sexual. Asexual involves only one parent, for example, bacteria dividing their cells in two, creating two new beings. Sexual involves two parents.

4. Movement: All things should be able to move in some way. It is noticeable that a human, dog, centipede, can all move, but then what about plants? Plants move, only they move so slowly it is only noticeable after a certain number of time. For example, sunflowers move into the direction of the sun, flowering plants open their petals. The roots move down into the earth. Although it is not obvious, like a running animal, plants do move.

5. Response: Response is when an organism has the ability to respond to changes in its environment and to things happening in their bodies. Organisms respond to light, sound, and touch. Again, plants do not seem to be responding much, when you pull of one of their leaves, they don’t jump back from shock and pain. But plants do respond. They have no nervous system, so they won’t respond to touch, but they grow toward the light. If the sun changes place, they adapt themselves so that they end up back towards the sun. Another example would be that if a seed that is growing finds itself the wrong way, with its roots in the air, then the plant will respond to gravity and shift so that it’s roots are back down in the earth.

6. Respiration: Respiration is how organisms get and use their food. There are two types of organisms for this characteristic: Autotrophs and Heterotrophs. Autotrophs are organisms that create their own food, i.e. plants. Heterotrophs are organisms that get food by eating other organisms, i.e. animals.

7. Metabolism: This is how an organism uses it’s food, which food it requires, and how much of it it requires, and also what is poisonous to the organism. It is also the ability to create energy, and to divide it for separating it into different parts of the organism. A living thing must be able to metabolize.

All these characteristics must be present in something for it to be an organism, otherwise it is not alive. Is a cellphone alive?  It reacts with it’s environment (when you press buttons), it moves when it vibrates, but does it reproduce or break down its food to make energy?

Reference: http://en.wikipedia.org/wiki/Life,

http://wiki.answers.com/Q/What_are_the_7_characteristics_of_life

http://edhelper.com/ReadingComprehension_37_158.html

http://en.wikipedia.org/wiki/Metabolism

http://bit.ly/a2HcIm

http://bit.ly/ctPcRv

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