LOOKING AT HUMANS
Chances are... you're a human. Whether you're a boy or a girl, man or a woman, you are still human. It doesn't matter what you look like, or what you believe... you're still a part of the human species. You are of the species Homo sapiens! That's what a scientist would call you anyway. But what makes you a Homo sapiens? Why are you different from a dog? Or a cat?
HOW ARE HUMANS LABELED?
Cats, dogs, and now you. Below is the exact name a scientist would use to describe you. If an alien came from outer space, and wanted to understand about every living thing on Earth, they would use these labels. You could put a big sign on your dog with his description and you could wear one that described you. Your sign would read...
ANIMALIA - CHORDATA - MAMMALIA - PRIMATA - HOMINIDAE - HOMO - SAPIENS
WHY DO SCIENTISTS THINK YOU ARE HUMAN?
We don't care what people say about you, we know that you are human. But then again, we're scientists. So let's start with the biggest grouping. You live in the KINGDOM - ANIMALIA. If you remember, there are four Kingdoms. You are made up of many, many cells (multicellular) and all those cells have a nucleus with a membrane. You don't have any chlorophyll. If you did, you would be a plant.
Next is the Phylum. You are PHYLUM - CHORDATA. So when you were a fetus (in the womb before you were born) you had something called a notochord. That's a rod made out of cartilage. As you developed, that cartilage turned into a spinal cord made out of bones. That's what scientists call vertebrae. Those magic vertebrae put you in the SUBPHYLUM - VERTEBRATA.
Feel your hand. Hopefully it's warm, not cold like a snake. Having warm blood makes you special. Look in the mirror. Do you have any feathers? Do you have teeth? If you had feathers and no teeth scientists would toss you in with the birds. One last thing, if you are an adult woman you should have the ability to nurse your babies. That's called breast feeding (or suckling). Most mammals do that for their babies. Now you're falling into the CLASS - MAMMALIA.
Okay, you're a mammal. That's still a long way from being human. As far as we know, you're some blind mole that lives out in the desert. Do you lay eggs? No. Do you have a pouch? No. You, assuming you are an adult female, have babies that start their life in something called a placenta. That's the lining for the womb where the baby (or fetus) grows until it is born. That magic placenta puts you in the SUBCLASS - EUTHERIA.
Now for the easy stuff. You should have five fingers and five toes on each hand and foot. One of those fingers should be a thumb. You have flat fingernails on those fingers and toes. You have a collarbone (that's the one between your neck and your shoulders). You are officially in the ORDER - PRIMATA (that's where the primates and monkeys are). Your eyes are in the front of your head. Not on the sides like a dolphin or some other monkeys. SUBORDER - ANTHROPOIDEA.
Almost there. Tail? Nope. Do you walk on two legs? Yup. Your spinal cord and vertebrae are also "S" shaped (that's important). That puts you in the FAMILY - HOMINIDAE.
You are in the GENUS - HOMO. There was another genus, which is now extinct called Australopithecus. Very close to you, but not quite human.
And finally, you are SPECIES - SAPIENS. There used to be a species Homo erectus. They are now extinct. That's it. All those names tell scientists huge amounts about you, your physiology, your genetics, and they way you develop into being an adult.
Selasa, 27 Oktober 2009
Jumat, 09 Oktober 2009
An Ecological System
The word ecosystem is short for ecological systems. An ecosystem includes all of the living organisms in a specific area. These systems are the plants and animals interacting with their non-living environments (weather, Earth, Sun, soil, atmosphere). An ecosystem's development depends on the energy that moves in and out of that system. As far as the boundaries of an ecosystem, it depends upon how you use the term. You could have an entire ecosystem underneath a big rock. On the other hand, you could be talking about the overall ecosystem of the entire planet (biosphere).
An ecosystem can be as small as a puddle or as large as the Pacific Ocean. That ecosystem includes every living and non-living thing in the area. It is several small communities interacting with each other.
Let's look at a puddle example. You might start by looking at the temperature, depth, turbulence, sunlight, atmospheric pressure, weather patterns, wind, nutrients, etc. Those are just the non-living things in the ecosystem of a puddle. When you add on all the living interactions, you have a good idea how complex an ecosystem can be. Even a puddle is an amazing place.
Biomes
Scientists discuss some general ecosystem types. They call them biomes. A biome is a large area on the Earth's surface that is defined by the types of animals and plants living there. A biome can be partially defined by the local climate patterns. You may also have more than one type of biome within a larger climate zone. Here is a short list of possible biomes.
- Tropical Rainforest (Think about Brazil)
- Tropical Savanna (Think about Africa)
- Desert (Think about the middle east)
- Mediterranean Woodland (Think about coniferous forests)
- Mid-latitude Grassland (Think about Oklahoma)
- Mid-latitude Deciduous Forest (Think about the east coast of North America)
- Tundra (Think about frozen plains of Alaska)
- Ice Caps (Think about the poles)
Ecotones
Biomes don't just start and stop when they border each other. They all have transition zones that have characteristics of both sides. That zone is like a blending of two biomes. Scientists call it an ecotone. Ecotones can happen at the edges of forests, deserts, and mountain ranges. They are often easy to see because one type of world (many trees) changes quickly into another type (the cliffs of a mountain). While an ecotone on the ground may not cover a large area of land, climate transition zones between biomes are often very large.
The word ecosystem is short for ecological systems. An ecosystem includes all of the living organisms in a specific area. These systems are the plants and animals interacting with their non-living environments (weather, Earth, Sun, soil, atmosphere). An ecosystem's development depends on the energy that moves in and out of that system. As far as the boundaries of an ecosystem, it depends upon how you use the term. You could have an entire ecosystem underneath a big rock. On the other hand, you could be talking about the overall ecosystem of the entire planet (biosphere).
An ecosystem can be as small as a puddle or as large as the Pacific Ocean. That ecosystem includes every living and non-living thing in the area. It is several small communities interacting with each other.
Let's look at a puddle example. You might start by looking at the temperature, depth, turbulence, sunlight, atmospheric pressure, weather patterns, wind, nutrients, etc. Those are just the non-living things in the ecosystem of a puddle. When you add on all the living interactions, you have a good idea how complex an ecosystem can be. Even a puddle is an amazing place.
Biomes
Scientists discuss some general ecosystem types. They call them biomes. A biome is a large area on the Earth's surface that is defined by the types of animals and plants living there. A biome can be partially defined by the local climate patterns. You may also have more than one type of biome within a larger climate zone. Here is a short list of possible biomes.
- Tropical Rainforest (Think about Brazil)
- Tropical Savanna (Think about Africa)
- Desert (Think about the middle east)
- Mediterranean Woodland (Think about coniferous forests)
- Mid-latitude Grassland (Think about Oklahoma)
- Mid-latitude Deciduous Forest (Think about the east coast of North America)
- Tundra (Think about frozen plains of Alaska)
- Ice Caps (Think about the poles)
Ecotones
Biomes don't just start and stop when they border each other. They all have transition zones that have characteristics of both sides. That zone is like a blending of two biomes. Scientists call it an ecotone. Ecotones can happen at the edges of forests, deserts, and mountain ranges. They are often easy to see because one type of world (many trees) changes quickly into another type (the cliffs of a mountain). While an ecotone on the ground may not cover a large area of land, climate transition zones between biomes are often very large.
REASONING IN SCIENCE
Learning about the scientific method is almost like saying that you are learning how to learn. You see, the scientific method is the way scientists learn and study the world around them. It can be used to study anything from a leaf to a dog to the entire Universe.
The basis of the scientific method is asking questions and then trying to come up with the answers. You could ask, "Why do dogs and cats have hair?" One answer might be that it keeps them warm. BOOM! It's the scientific method in action.
QUESTIONS AND ANSWERS
Just about everything starts with a question. Usually, scientists come up with questions by looking at the world around them. "Hey look! What's that?" See that squiggly thing at the end of the sentence? A question has been born.
So you've got a scientist. When scientists see something they don't understand they have some huge urge to answer questions and discover new things. It's just one of those scientist personality traits. The trick is that you have to be able to offer some evidence that confirms every answer you give. If you can't test your answer, other scientists can't test it to see if you were right or not.
As more questions are asked, scientists work hard and come up with a bunch of answers. Then it is time to organize. One of the cool things about science is that other scientists can learn things from what has already been established. They don't have to go out and test everything again and again. That's what makes science special: it builds on what has been learned before.
This process allows the world to advance, evolve, and grow. All of today's advancements are based on the achievements of scientists who already did great work. Think about it this way: you will never have to show that water (H2O) is made up of one oxygen (O) and two hydrogen (H) atoms. Many scientists before you have confirmed that fact. It will be your job as a new scientist to take that knowledge and use it in your new experiments.
EXPERIMENTAL EVIDENCE
Experimental evidence is what makes all of the observations and answers in science valid (truthful or confirmed). The history of evidence and validations show that the original statements were correct and accurate. It sounds like a simple idea, but it is the basis of all science. Statements must be confirmed with loads of evidence. Enough said.
Scientists start with observations and then make a hypothesis (a guess), and then the fun begins. They must then prove their hypothesis with trials and tests that show why their data and results are correct. They must use controls, which are quantitative (based on values and figures, not emotions). Science needs both ideas (the hypothesis) and facts (the quantitative results) to move forward. Scientists can then examine their data and develop newer ideas. This process will lead to more observation and refinement of hypotheses.
THE WHOLE PROCESS
There are different terms used to describe scientific ideas based on the amount of confirmed experimental evidence.
Hypothesis
- a statement that uses a few observations
- an idea based on observations without experimental evidence
Theory
- uses many observations and has loads of experimental evidence
- can be applied to unrelated facts and new relationships
- flexible enough to be modified if new data/evidence introduced
Law
- stands the test of time, often without change
- experimentally confirmed over and over
- can create true predictions for different situations
- has uniformity and is universal
You may also hear about the term "model." A model is a scientific statement that has some experimental validity or is a scientific concept that is only accurate under limited situations. Models do not work or apply under all situations in all environments. They are not universal ideas like a law or theory.
Learning about the scientific method is almost like saying that you are learning how to learn. You see, the scientific method is the way scientists learn and study the world around them. It can be used to study anything from a leaf to a dog to the entire Universe.
The basis of the scientific method is asking questions and then trying to come up with the answers. You could ask, "Why do dogs and cats have hair?" One answer might be that it keeps them warm. BOOM! It's the scientific method in action.
QUESTIONS AND ANSWERS
Just about everything starts with a question. Usually, scientists come up with questions by looking at the world around them. "Hey look! What's that?" See that squiggly thing at the end of the sentence? A question has been born.
So you've got a scientist. When scientists see something they don't understand they have some huge urge to answer questions and discover new things. It's just one of those scientist personality traits. The trick is that you have to be able to offer some evidence that confirms every answer you give. If you can't test your answer, other scientists can't test it to see if you were right or not.
As more questions are asked, scientists work hard and come up with a bunch of answers. Then it is time to organize. One of the cool things about science is that other scientists can learn things from what has already been established. They don't have to go out and test everything again and again. That's what makes science special: it builds on what has been learned before.
This process allows the world to advance, evolve, and grow. All of today's advancements are based on the achievements of scientists who already did great work. Think about it this way: you will never have to show that water (H2O) is made up of one oxygen (O) and two hydrogen (H) atoms. Many scientists before you have confirmed that fact. It will be your job as a new scientist to take that knowledge and use it in your new experiments.
EXPERIMENTAL EVIDENCE
Experimental evidence is what makes all of the observations and answers in science valid (truthful or confirmed). The history of evidence and validations show that the original statements were correct and accurate. It sounds like a simple idea, but it is the basis of all science. Statements must be confirmed with loads of evidence. Enough said.
Scientists start with observations and then make a hypothesis (a guess), and then the fun begins. They must then prove their hypothesis with trials and tests that show why their data and results are correct. They must use controls, which are quantitative (based on values and figures, not emotions). Science needs both ideas (the hypothesis) and facts (the quantitative results) to move forward. Scientists can then examine their data and develop newer ideas. This process will lead to more observation and refinement of hypotheses.
THE WHOLE PROCESS
There are different terms used to describe scientific ideas based on the amount of confirmed experimental evidence.
Hypothesis
- a statement that uses a few observations
- an idea based on observations without experimental evidence
Theory
- uses many observations and has loads of experimental evidence
- can be applied to unrelated facts and new relationships
- flexible enough to be modified if new data/evidence introduced
Law
- stands the test of time, often without change
- experimentally confirmed over and over
- can create true predictions for different situations
- has uniformity and is universal
You may also hear about the term "model." A model is a scientific statement that has some experimental validity or is a scientific concept that is only accurate under limited situations. Models do not work or apply under all situations in all environments. They are not universal ideas like a law or theory.
METABOLISM
Metabolism is such a big word to explain a simple idea. We all need energy to survive. Plants, animals, or bacteria, we all need energy. Energy doesn't just float around in a form we can use to survive. We need to eat (mainly sugars) and digest food. That process of chemical digestion and its related reactions is called metabolism. Metabolism is the total of all of the chemical reactions an organism needs to survive.
Sounds a lot like biology. Why's it here in biochemistry? Two main chemical processes make our world go round. There are two simple chemical reactions. The first is called glycolysis. That's the breakdown of sugars. The second process is called photosynthesis. That is the reaction that builds sugars. You need to remember that the overall metabolism of an organism includes thousands of chemical reactions. Glycolysis and photosynthesis are the cornerstones to life.
BUILDING UP
First, you need to build up the molecules that store energy. We'll start with photosynthesis. It's no use explaining the breakdown of sugars without telling you how they were made.
LIGHT (Energy) + CO2 + H2O --> C6H12O6 + O2
This is the reaction that only plants can do (and some algae/bacteria). They take sunlight and combine carbon dioxide (CO2) and water (H2O). They create Glucose (C6H12O6) and oxygen gas (O2). Remember, plants put the energy in glucose.
BREAKING DOWN
It's metabolism and the process of glycolysis that takes that energy out of the sugar related molecules.
C6H12O6 + O2--> Usable Energy (ATP) + CO2 + H2O
Cells then use that extra energy to power the functions of the cell. The energy isn't still floating around; it's stored in an excitable compound called adenosine triphosphate (ATP). ATP is the power molecule used all over organisms and their cells to power the secondary reactions that keep us alive.
Metabolism is such a big word to explain a simple idea. We all need energy to survive. Plants, animals, or bacteria, we all need energy. Energy doesn't just float around in a form we can use to survive. We need to eat (mainly sugars) and digest food. That process of chemical digestion and its related reactions is called metabolism. Metabolism is the total of all of the chemical reactions an organism needs to survive.
Sounds a lot like biology. Why's it here in biochemistry? Two main chemical processes make our world go round. There are two simple chemical reactions. The first is called glycolysis. That's the breakdown of sugars. The second process is called photosynthesis. That is the reaction that builds sugars. You need to remember that the overall metabolism of an organism includes thousands of chemical reactions. Glycolysis and photosynthesis are the cornerstones to life.
BUILDING UP
First, you need to build up the molecules that store energy. We'll start with photosynthesis. It's no use explaining the breakdown of sugars without telling you how they were made.
LIGHT (Energy) + CO2 + H2O --> C6H12O6 + O2
This is the reaction that only plants can do (and some algae/bacteria). They take sunlight and combine carbon dioxide (CO2) and water (H2O). They create Glucose (C6H12O6) and oxygen gas (O2). Remember, plants put the energy in glucose.
BREAKING DOWN
It's metabolism and the process of glycolysis that takes that energy out of the sugar related molecules.
C6H12O6 + O2--> Usable Energy (ATP) + CO2 + H2O
Cells then use that extra energy to power the functions of the cell. The energy isn't still floating around; it's stored in an excitable compound called adenosine triphosphate (ATP). ATP is the power molecule used all over organisms and their cells to power the secondary reactions that keep us alive.
Plant Basics
If you're not a microbe and you're not an animal, chances are you are a plant. There are loads of species of plants on Earth. Just as there is a system of classification for animals, there is also a system of classification for plants. Because plants adapt so well to any climate, scientists need a way to organize the hundreds of thousands of species.
What Makes a Plant?
What do they all have in common? The big thing that connects plants is photosynthesis. Photosynthesis is the process that allows plants to take energy from the Sun and create sugars. Not all plants go through the process of photosynthesis. As with all of biology, there are exceptions and you may learn about plant species that are parasites. Plants also have cell walls. In the cells tutorials we explained that all cells have a membrane. Only plants have an additional cell wall made from cellulose.
Let's look at photosynthesis. Plants are able to turn sunlight into energy but not directly. Plants are actually able to store energy in some chemical bonds that can be used later. Before we get into details, we'll explain that there are two processes on Earth: Photosynthesis and Respiration. Photosynthesis stores the energy and respiration releases that energy. It all starts with the Sun. Check out the tutorial on photosynthesis.
Learning from Plants
Not only do you see plants everywhere in the real world, but they are also all over the scientific world. Scientists use them for studies in genetics. A guy named Gregor Mendel used pea pods and their flowers to come up with some of the first ideas on how traits are passed from one generation of organism to another (genetics). We also use plants for food. Scientists are constantly developing new plants that are more resistant to disease and insects. Scientists also help create plants that grow faster and make more food.
If you're not a microbe and you're not an animal, chances are you are a plant. There are loads of species of plants on Earth. Just as there is a system of classification for animals, there is also a system of classification for plants. Because plants adapt so well to any climate, scientists need a way to organize the hundreds of thousands of species.
What Makes a Plant?
What do they all have in common? The big thing that connects plants is photosynthesis. Photosynthesis is the process that allows plants to take energy from the Sun and create sugars. Not all plants go through the process of photosynthesis. As with all of biology, there are exceptions and you may learn about plant species that are parasites. Plants also have cell walls. In the cells tutorials we explained that all cells have a membrane. Only plants have an additional cell wall made from cellulose.
Let's look at photosynthesis. Plants are able to turn sunlight into energy but not directly. Plants are actually able to store energy in some chemical bonds that can be used later. Before we get into details, we'll explain that there are two processes on Earth: Photosynthesis and Respiration. Photosynthesis stores the energy and respiration releases that energy. It all starts with the Sun. Check out the tutorial on photosynthesis.
Learning from Plants
Not only do you see plants everywhere in the real world, but they are also all over the scientific world. Scientists use them for studies in genetics. A guy named Gregor Mendel used pea pods and their flowers to come up with some of the first ideas on how traits are passed from one generation of organism to another (genetics). We also use plants for food. Scientists are constantly developing new plants that are more resistant to disease and insects. Scientists also help create plants that grow faster and make more food.
Looking at Cell Functions
All cells have a purpose. If they don't do anything productive, they are not needed anymore. In the big picture, a cell's purpose is much more important than acting as small organizational pieces. They had their purpose long before they started working together in groups and building more advanced organisms. When alone, a cell's main purpose is to survive.
Even if you were a single cell, you would have a purpose. You would have to survive. You would be moving around (probably in a liquid) and just trying to stay alive. You would have all of your pieces inside of you. If you were missing a piece you needed to survive, you would die. Scientists call those pieces organelles. Organelles are groups of complex molecules that help a cell survive.
All Cells are not Created Equal
In the same way that cells survive in different ways; all cells have different types and amounts of organelles. The larger a cell becomes the more organelles it will need. It makes sense if you think about it. If you are a big cell, you will need to eat more than a little cell. You will also need to convert that food into energy. A larger cell would need to eat more and may wind up having more mitochondria to process that food into energy.
While they might have a purpose, more advanced cells have a difficult time surviving on their own. A cell from your brain could not survive in a Petri dish for long. It doesn't have the right pieces to live on its own. It does have the ability to transmit electrical systems around your body. An amoeba could survive in a dish forever, thrive, and reproduce. On the other hand, that amoeba will never help you transmit electrical impulses. The brain cell is far more advanced and has specific abilities and organelles. Simpler cells have a better chance of surviving on their own while complex cells can accomplish tasks that are more advanced.
All cells have a purpose. If they don't do anything productive, they are not needed anymore. In the big picture, a cell's purpose is much more important than acting as small organizational pieces. They had their purpose long before they started working together in groups and building more advanced organisms. When alone, a cell's main purpose is to survive.
Even if you were a single cell, you would have a purpose. You would have to survive. You would be moving around (probably in a liquid) and just trying to stay alive. You would have all of your pieces inside of you. If you were missing a piece you needed to survive, you would die. Scientists call those pieces organelles. Organelles are groups of complex molecules that help a cell survive.
All Cells are not Created Equal
In the same way that cells survive in different ways; all cells have different types and amounts of organelles. The larger a cell becomes the more organelles it will need. It makes sense if you think about it. If you are a big cell, you will need to eat more than a little cell. You will also need to convert that food into energy. A larger cell would need to eat more and may wind up having more mitochondria to process that food into energy.
While they might have a purpose, more advanced cells have a difficult time surviving on their own. A cell from your brain could not survive in a Petri dish for long. It doesn't have the right pieces to live on its own. It does have the ability to transmit electrical systems around your body. An amoeba could survive in a dish forever, thrive, and reproduce. On the other hand, that amoeba will never help you transmit electrical impulses. The brain cell is far more advanced and has specific abilities and organelles. Simpler cells have a better chance of surviving on their own while complex cells can accomplish tasks that are more advanced.
Cells are the Starting Point
All living organisms on Earth are divided in pieces called cells. There are smaller pieces to cells that include proteins and organelles. There are also larger pieces called tissues and systems. Cells are small compartments that hold all of the biological equipment necessary to keep an organism alive and successful on Earth.
A main purpose of a cell is to organize. Cells hold a variety of pieces and each cell has a different set of functions. It is easier for an organism to grow and survive when cells are present. If you were only made of one cell, you would only be able to grow to a certain size. You don't find single cells that are as large as a cow. Also, if you were only one cell you couldn't have a nervous system, no muscles for movement, and using the internet would be out of the question. The trillions of cells in your body make your life possible.
One Name, Many Types
There are many types of cells. In biology class, you will usually work with plant-like cells and animal-like cells. We say animal-like because an animal type of cell could be anything from a tiny microorganism to a nerve cell in your brain. Plant cells are easier to identify because they have a protective structure called a cell wall made of cellulose. Plants have the wall; animals do not. Plants also have organelles like the chloroplast (the things that make them green) or large water-filled vacuoles.
We said that there are many types of cells. Cells are unique to each type of organism. Humans may have hundreds of types of cells. Some cells are used to carry oxygen (O2) through the blood (red blood cells) and others might be specific to the heart. If you look at very simple organisms, you will discover cells that have no defined nucleus (prokaryotes) and other cells that have hundreds of nuclei (multinucleated). The thing they all have in common is that they are compartments surrounded by some type of membrane.
All living organisms on Earth are divided in pieces called cells. There are smaller pieces to cells that include proteins and organelles. There are also larger pieces called tissues and systems. Cells are small compartments that hold all of the biological equipment necessary to keep an organism alive and successful on Earth.
A main purpose of a cell is to organize. Cells hold a variety of pieces and each cell has a different set of functions. It is easier for an organism to grow and survive when cells are present. If you were only made of one cell, you would only be able to grow to a certain size. You don't find single cells that are as large as a cow. Also, if you were only one cell you couldn't have a nervous system, no muscles for movement, and using the internet would be out of the question. The trillions of cells in your body make your life possible.
One Name, Many Types
There are many types of cells. In biology class, you will usually work with plant-like cells and animal-like cells. We say animal-like because an animal type of cell could be anything from a tiny microorganism to a nerve cell in your brain. Plant cells are easier to identify because they have a protective structure called a cell wall made of cellulose. Plants have the wall; animals do not. Plants also have organelles like the chloroplast (the things that make them green) or large water-filled vacuoles.
We said that there are many types of cells. Cells are unique to each type of organism. Humans may have hundreds of types of cells. Some cells are used to carry oxygen (O2) through the blood (red blood cells) and others might be specific to the heart. If you look at very simple organisms, you will discover cells that have no defined nucleus (prokaryotes) and other cells that have hundreds of nuclei (multinucleated). The thing they all have in common is that they are compartments surrounded by some type of membrane.
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