Biology

= = = Origin of Life = = = Amino acids are the building blocks of life as we know it. They can be formed from abiotic (non-biological) chemical reactions (in a jar with electricity for example). It’s been known for a while that amino acids can be found on comets and asteroids, but now this fascinating article suggests that a lot of the chemical reactions that created these precursors to life happened on the asteroids themselves. Then when the asteroids bombarded the Earth, the seeds of life were delivered. = =

= = Until the 1600's, most people believed in spontaneous generation. This theory maintained that life could start from non-living matter. People believed that mice came from straw and that frogs and turtles came from rotting wood and mud at the bottom ofa pond. For example, many people know that if you left meat out to rot that maggots would often appear within a few days. They thought that the meat turned into little worms, which would eventually turn into flies. = =

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= = =Scientists= = =

Francesco Redi
= = An Italian doctor, Francesco Redi, did not believe in this idea. Like many educated people of his time, he was interested in how life developed. He decided to test the common idea that maggots could come from rotting meat that was exposed to air. In 1668~ he disproved the theory of spontaneous generation using the scientific method. Redi thought that if spontaneous generation was possible, maggots would be found even in meat that was sealed in jars. So Redi placed pieces of meat into several jars. Some jars he sealed tightly. Some he covered with a fine cloth. Some he left open to the air. No maggots appeared in the sealed jars. The meat in the open jars attracted flies and soon maggots appeared on the meat. Flies were attracted to the cloth covered jars too. But the maggots laid eggs on the top of the cloth. Since the flies could not reach the meat, eggs could not develop into maggots without food and moisture. = =

= = If maggots could come from meat alone, they would have appeared in all of the jars. If maggots could come from meat and air, they would have appeared in the jars covered by the cloth. Redi had shown that maggots did not arise from meat, whether air was present or not. The maggots had to come from some other source. = =

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Lazaro Spallanzani
= = In 1768~ an Italian biologist boiled a broth in glass bottles. Boiling killed any organisms in the broth. He sealed the bottles so that air could not enter. The broth stayed clear. Finally he opened the bottles and allowed the air to enter. Small organisms floating in the air got into the broth. The broth quickly began to spoil. = =

= = Spallanzani's results supported Redi's. But Spallanzani had not tested the effect of the presence or the absence of air. Some people thought that if there had been air in the sealed bottles, the results would have been different. About 100 years later, a French scientist changed the format of Spallanzani's experiment in order to make it more scientific. = =

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Louis Pasteur
= = Louis Pasteur believed that bacteria existed in the air as spores that were in a resting state. He thought these spores were attached to dust particles in the air. When the spores landed on a place where there was food and water, they would begin to grow and reproduce. Pasteur modified Spallanzani' s experiment by using special long necked flasks to hold the broth. The necks were curved and very thin, but they were open. Air could enter the flasks, but dust carried in the air became trapped in the curved necks. Pasteur found that nothing grew in the flasks until he broke off the necks. Then dust from the air could enter, carrying small organisms with it. Soon the broth became cloudy and bubbly, and organisms in the broth were visible under the microscope. He showed that organisms could not appear in the broth unless the broth first came in contact with living organisms. Scientists have not believed in spontaneous generation since the results of this experiment became known. Today there is no doubt that living things can come only from other living things. Scientists finally were convinced that living things, no matter how small, do NOT come from nonliving things. The present theory of where living things come from is called Biogenesis. This theory states that living things come only from other living things. For example, mice come only from mice, and microorganisms such as bacteria can only come from other bacteria. = =

= = So if living things can only come from other living things, then where did the first living things come from? = =

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Stanley Miller
= = In 1953 a graduate student named Stanley Miller set out to verify the Oparin-Haldane­Urey hypothesis with a simple but elegant experiment. The results of this experiment have been taught to every high school and college biology student for nearly four decades. He reproduced the early atmosphere of Earth that Urey proposed by creating a chamber with only hydrogen, water, methane, and ammonia. To speed up "geologic time" in his experiment, he boiled the water and instead of exposing the mix to ultraviolet light he used an electric discharge something like lightning. After just a week, Miller had a residue of compounds settled in his system. He analyzed them and the results were electrifying: Organic compounds had been formed, most notably some of the "building blocks of life," amino acids. Amino acids are necessary to form proteins which themselves form the structure of cells and play important roles in the biochemical reactions life requires. = =

= = =The Cell Theory= While observing dead cork samples with a crude lens, Robert Hooke identified and named “cells.” He was able to see the minute, boxlike units of which the cork was made up. Hooke called these structures cells because he thought the boxes looked like monastery cells.

Years later, as microscopes improved, other biologists were able to continue the work of Hooke and Leeuwenhoek, learning more about cells. German biologist Matthias Schleiden discovered that every part of a plant he looked at was made of cells. Another German scientist by the name of Theodor Schwann discovered that every part of an animal he looked at through a microscope was made of cells.

Today scientists have developed what we call the **Cell Theory**. This theory states the following:


 * **All living things are made of cells.**


 * **Cells are the basic units of structure and function in living things.**
 * **Living cells come only from other living cells.**

=Characteristics of Living Things= = = Living things are able to move, grow, reproduce, respond to stimulus and perform certain chemical activities called metabolism. = =

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Movement
= = An ability to move through the environment is an important characteristic of many living things. Animals must move in order to find food and shelter. Animals move in a variety of ways. Plants do not move in the same way that animals do. Only parts of the plants move. Stems bend and leaves turn towards the light. = =

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** Metabolism **
= = Living things can not move if they do not receive and have energy. Energy is stored and released by building up and breaking down chemical substances. These energy related activities are called metabolism. Metabolism includes many chemical reactions that happen in an organism. There are 4 basic parts of metabolism: = =

** 1. Ingestion **
= = All living things must either take in food or produce their own food. Some animals take in food with their mouths by eating it while others absorb food through their skin. Plants do not have to ingest food because they make their own. They use their roots to absorb minerals and water from the soil and tiny openings in their leaves to exchange oxygen and carbon dioxide. = =

** 2. Digestion **
= = The food taken in then must be digested. Digestion is the process by which food is broken down into simpler substances. = =

** 3. Respiration **
= = Living things combine oxygen with the products of digestion to produce energy. The energy is used to do all the work of the organism. The process by which living things take in oxygen and use it to produce energy is called respiration. = =

** 4. Excretion **
= = Not all the products of digestion and respiration can be used by organisms. Some products are waste materials that must be released. The process of getting rid of waste materials is called excretion. If these products are not removed, they will eventually poison the organism. = =

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** Response to Stimulus **
= = What smells make your mouth water? An organism reacts to changes in its environment. Plants respond to water and light by growing toward them. Animals have the senses of seeing, hearing, tasting, smelling, and touching, which enable them to respond to the may changes in their environment. = =

= = A **stimulus** is any change in the environment of an organism that produces a response. A response is some action or movement of the organism. = =

= = Many responses are involuntary: = = = =
 * Clapping hands in your faces causes you to blink your eyes Bright light causes your pupils to dilate
 * Sour lemons cause you to pucker
 * Lack of oxygen causes you to yawn

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** Reproduction **
= = = =
 * Reproduction** is the process by which living things give rise to the same type of living thing that can also reproduce.

= = There are two types of reproduction: = = = = = =
 * Sexual - **involves two parents and produces offspring that are similar to the parents
 * Asexual - **involves only one parent and produces offspring that are identical to the parent

= = Either way, the offspring gets a set of chemical plans or blueprints that determine the characteristics of that type of living thing. Reproduction is the only life activity that is not necessary for keeping an individual organism of a species alive. All of the other life activities are. Although reproduction is not essential for the life of an individual organism, this activity is essential for the continuation of life from one generation to another.

= Eukaryotic Cells: The Inside Story = There are lots of different types of cells. Each type of cell is different and performs a different function. In the human body, we have nerve cells which can be as long as from our feet to our spinal cord. Nerve cells help to transport messages around the body. We also have billions of tiny little brain cells and muscle cells which help us move around. There are many more cells in our body that help us to function and stay alive.

Although there are lots of different cells, most of them can be divided into two main categories: prokaryotic and eukaryotic.


 * Prokaryotic Cells** - The prokaryotic cell is a simple, small cell with no nucleus. Most bacteria are prokaryotic. There are three main parts to the prokaryotic cell: 1) the outside of the cell called the cell wall 2) the flagella which is like an appendage and can help the cell to move 3) the inside of the cell called the cytoplasm.


 * Eukaryotic Cells** - these cells are a lot bigger and have a cell nucleus which houses the cell's DNA. These are the types of cells we find in plants and animals.

= = Cells have many different organelles that help it function. There is sometimes a cell wall that supports the cell membrane, a endoplasmic reticulum that creates lipids (fats). Chloroplasts give plant color and energy.Mitochondria gives a cell protein while a golgi complex ships content around the cell. Vesicles form when cell membrane covers something outside and a vacuole that stores water for a plant. Finally, lysosomes that eat used up things and dissolve cells. = = =Cell Parts=
 * **Nucleus** - the "brain" of the cell. DNA.
 * **Ribosomes** - these organelles make new proteins for the cell
 * **Endoplasmic Reticulum** - this organelle acts as a delivery system of the proteins made by the ribosomes.
 * **Golgi Apparatus** - prepares the proteins for delivery
 * **Mitochondria** - this is the "energy station" for the cell.
 * **Chloroplast -** converts energy from the sun into food for autotrophs
 * **Lysosomes** - digests food
 * **Central Vacuole** - cell sap, water, salts (calcium), inorganic ions (K+ and Cl-), enzymes, toxic byproducts.
 * **Cell Wall** - cellulose, cell shape, protection, filtering mechanism, found in plants, bacteria, Archaea, fungi, and algae.
 * **Cytoplasm** - cytosol. This is the semi-liquid materials in which organielle float.
 * **Cytoskeleton** - microfilaments, microtubules / centrioles. This provides support to the structure of the cell.
 * **Cell Membrane** - phospholipid bilayer that currounds the cell. It controls what can go in and out of the cell because it is semi-permeable.

Holding It All Together
 * All cells have an outer covering that separates the inside of the cell from the outside
 * All the cells are covered with a cell membrane
 * The job of the cell membrane is to keep all the cytoplasm, allow nutrients in and waste out, and to interact with things outside the cell
 * The cell wall is only found in the cells of plant and algae
 * The cell wall is a layer that surrounds and provide strength and support to the cell membrane
 * The cell wall keeps the cell membrane from ripping when too much water enters the cell
 * Cell walls in plants are made of cellulose fiber that crosses over each other
 * The strength of a cell wall can defy gravity

The Cell's Library
 * The largest and most visible organelle is the nuclues
 * Nucleus is the control center and contains DNA
 * The dark spot in the nucleus is the nucleolus
 * The nucleolus stores materials that will be used later to make ribosomes in the cytoplasm

Protein Factories
 * Proteins are the building blocks of all cells
 * Proteins are made of amino acids
 * Amino cells are hooked together to make proteins at an organelle called ribosomes
 * Ribosomes are the smallest organelle
 * Ribosomes are the only organelles that have no membrane
 * Every cell needs ribosomes to live

The Cell's Delivery System
 * The endoplasmic reticulum, or ER, is a membrane covered compartment that makes lipids and other materials to be used inside and outside the cell
 * The ER breaks down drugs and other harmful materials in the cell
 * The internal delivery system of a cell
 * The ER gathers the protein from the ribosomes and release it for use elsewhere

The Cell's Power Plants
 * Cells need energy to function
 * Food molecules are burned to release energy
 * The burned/broken down molecules are transfered a special moelcule called ATP
 * Mitochondria produce ATP
 * Mitochondria need oxygen to make ATP, and that is the reason we need to breathe
 * Plant and algae have an organelle called chloroplast
 * Chloroplast looks like stack of coins and contains a chemical called chlorophyll
 * Chlorophyll makes the plant green and traps sunlight to create sugar, this is the process of photosynthesis
 * The sugar is used by the mitochondria to make ATP
 * The mitochondria and the chloroplast are as small as a bacteria and have two cell membranes
 * They divide like a bacteria and known to be originated from prokaryotic cells

The Cell's Packaging Center
 * The golgi complex is the organelle that ships and processes proteins and other materials out of the eukaryotic cells
 * Named after the Italian scientist, Camillo Golgi
 * Golgi complex looks like a ER, but closer to the cell membrane
 * Lipids and proteins from the ER is delievered to the golgi complex to be modified for different function
 * The final product is enclosed in a piece of the golgi complex's membrane that pinches off to form a compartment where materials are put in to be shipped

The Cell's Storage Center
 * All eukaryotic cells have membrane covered compartmeent called vesicles
 * Vesicles cover objects outside the cell
 * Vacuole is a large membrane covered chamber that contains the plant's water
 * Vacuoles can change the color of a plant and contain the juice of a plant
 * Some unicelluar organisms that live in water has a special vacuole called contractile vacuole that squeeze out water when there is too much

Packages of Destruction
 * Lysosomes are special vesicles that contain enzymes
 * Lysosomes pour enzymes on a particle that is enclosed in a vesicle
 * Lysosomes destroy worn out or damaged cells
 * They protect the cell from waste materials and foreign invaders
 * Sometimes the lysosome break and spill the enzymes that destroies the cell

**Needs of Living Things**

**Homeostasis**
Living organisms must remain in homeostasis. If they don’t, they are ill or they are dead. **Homeostasis**- same stationary condition- steady state- organisms need to maintain a steady state despite an ever-changing internal and external environment. How do we maintain balance? How does the body know? The **nervous system** is most related to this- sweat.

**Water**
The amount needed varies, but all living organisms require water. Some organisms live in water, some need salt water and others can only survive with fresh water. Plants take water to grow and create food. Certain plants, including algae, can only survive submerged in water, and they absorb carbon dioxide. For humans and animals, water serves as a digestion assistant, as well as a critical component of body fluids.

**Living Space**
While habitats vary greatly from organism to organism, every living thing needs an efficient living space in order to survive. A key component of such a habitat is the proper temperature. Some plants can only survive in the dampest of conditions, while others require a drier home. The habitat must also have sufficient resources for the living organism. Limited resources will result in competition, leading to the death of certain organisms.

Organisms need energy to survive.All organisms need energy in the form of food to grow, move and carry out body movement. Organisms can get energy in one of two ways. As an autotroph (self feeder), the organism has the ability to make their own food. Most autotrophic organisms use energy from the sun to make food through the process of photosynthesis. As a heterotroph (other feeder), the organisms needs to eat other organisms in order to gain energy.
 * Energy**

= Organization of Life =

Biological organization is simply by the way of classifying the physical basics of a living thing from the smallest to the largest.

These levels are listed from the smallest to the largest.

**1. cells** Are the basic unit of structure and function in living things. May serve a specific function within the organism. Examples- blood cells, nerve cells, bone cells, etc.

2. tissues: Made up of cells that are similar in structure and function and which work together to perform a specific activity Examples - blood, nervous, bone, etc. Humans have 4 basic tissues: connective, epithelial, muscle, and nerve.

3. organs Made up of tissues that work together to perform a specific activity. Examples - heart, brain, skin, etc.

4. organ systems Groups of two or more tissues that work together to perform a specific function for the organism. Examples - circulatory system, nervous system, skeletal system, etc.

5. organisms Entire living things that can carry out all basic life processes. Meaning they can take in materials, release energy from food, release wastes, grow, respond to the environment, and reproduce. Usually made up of organ systems, but an organism may be made up of only one cell such as bacteria or protist.. Examples - bacteria, amoeba, mushroom, sunflower, human

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