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Biology made simple


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Biology basics made incredibly easy.

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Biology made simple

  1. 1. CHAPTER 1 BASIC CONCEPTS BIOLOGY MADE SIMPLE “If you can’t explain it simply enough, you didn’t understand it well enough” (Albert Einstein)
  2. 2. What is Biology? Biology is the science that studies everything that is alive, or put more academically, Biology is the science that studies living organisms. Living organisms are those that can do the following 3 things: 1) Reproduce: Ability to generate other living organisms similar to themselves. This function is important for the perpetuation of the species since the lifespan of living organisms is limited. The ability to reproduce resides in the nuclei of the cells, in the DNA. 2) Feed: Ability to metabolize - that is, to extract, transform and use - the energy from nutrients in the environment in order to grow and perform vital functions. The process of metabolism involves the creation (anabolism) and destruction (catabolism) of substances. During anabolism the living being obtains substances with which it builds its own molecules to grow. Anabolism consumes energy. During catabolism the products obtained in the previous stage are destroyed releasing energy to maintain vital functions. 3) Relate to the environment: Ability to receive stimuli and react to them.
  3. 3. The Organization of Life (or levels of organization) Living organisms (or beings) are like buildings. If you want to construct a building you need bricks. Many bricks put together with mortar form a wall, several walls will form a room, several rooms will form an apartment and several apartments will form a building. Likewise, many buildings form a district, many districts form a city, many cities form a country, many countries form continents, and they all form the Earth. Now back to living organisms: The bricks are the atoms. Several bricks with mortar are a molecule, a whole wall is a tissue, the room is an organ, the apartment is a system (or group of organs) and the building is the living organism (that is, you!). You and others form a population, the population in their environment (or ecosystem) is called a community, and everything put together is the Earth and the atmosphere or biosphere. Nice. Source: www.
  4. 4. From an Atom to a Tom If you chop something many, many, maaany times, there will come a time when you cannot make it any smaller and this is called “atom”. Atom means “not divisible” [or “can’t be made any smaller”]. That was true for a long time until someone spoiled it with the development of the electron microscope that showed that atoms are made of 3 particles: a nucleus made of protons and neutrons, and orbiting particles called electrons. It’s pretty much like the Earth and the Moon but often with several Moons. Imagine you are chopping off a can of soft drink and a ring made of gold. The can is made of aluminium and the ring, well..., of gold. Aluminium and gold are substances (more fancily known as “elements”). The smallest you could make the can would be an atom of aluminium and the smallest you could make the ring would be an atom of gold. Put differently, an atom is the smallest possible piece of an element that retains all the properties of that element. There are a bit over 100 elements but only 6 of them make up most of what exists on Earth. The acronym CHNOPS stands for Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur. The acronym goes from most to least common of the most common elements (hope you got that). Put several elements (atoms of one type) together and you’ll have a compound (molecule). Examples of compounds (or molecules) are water (2 hydrogens + 1 oxygen) and salt (1 sodium + 1 chloride). Cells are made of many different molecules. Cells of the same kind form tissues. For example cells with stretchy fibres inside form a tissue called the muscle. Cells with lots of calcium form a tissue called the bone. An organ like the stomach is made of several tissues (muscle, epithelial and nerve tissues). A system is made of several organs working towards the same end. For example the heart, arteries, veins, the thorax, and specific nerves form the cardio-vascular system. Put all the systems together (cardio-vascular, respiratory, gastro-intestinal, etc.) together and you’ve got an organism (or a being, and they often have names like Mary or Tom. This explains the silly header of this section: From an atom to a Tom...).
  5. 5. Classification of Cells We already know what it means to be alive: To be able to reproduce, feed, and relate to the environment. Knowing this, we can say that the cell is “the smallest living thing” or that the cell is ” the smallest unit of life “ There are 2 types of cells based on whether their nucleus has a membrane (eukaryotic cells) or not (prokaryotic cells). Animal cells (that is, human cells) are eukaryotic. Below are 2 images of an animal cell. All living organisms are made of cells. One kind of cell makes one kind of tissue. Only bone cells can make bone tissue, only muscle cells can make muscle tissue, etc. Our bodies have many different kinds of cells because we have many different kinds of tissues. Tissues are groups of cells all doing the same job. Animal cell for beginners Animal cell for pros
  6. 6. Classification of Tissues There are 4 major kinds of tissues: epithelial, connective, nerve, and muscle tissue. The job of the epithelial tissue is to shield the body and protect it from injury and infection. The skin and the lining of hollow organs like the stomach, intestines, blood vessels, bronchi, etc. are made of epithelial tissue. Connective tissue supports our bodies like an internal scaffold. Bone, cartilage, and fatty tissues are types of connective tissues. The blood is a special type of connective tissue. It is a liquid tissue. Nerve tissue is the information network of our bodies. Nerves send information from one part of our body to another. Nerve cells, or neurons, have many short thin branches (dendrites) and one long fat branch (axon) that connect one cell to another. Muscle tissue can contract and relax. There are 3 types of muscle tissue: Striated, smooth, and cardiac. The striated muscle tissue is attached to the bones and allows us to move whenever we want to, that’s why it is also called voluntary muscle tissue. Smooth muscle tissue makes involuntary muscles move. Involuntary muscles move on their own and we could not make them move if we wanted to. These muscles are inside hollow organs - like the intestine- behind the epithelium. Cardiac muscle tissue is the type of tissue that makes our heart pump.