Biology Lesson 1 - Basic Concepts of Biology

BIOLOGY IN YOUR LIFE - Life is a profound scientific undertaking - Organisms are so complex and are diverse having different functions, structures, manner of growth and origin. - Scientific principles helps us understand complexities of organisms - Biology means \"the study of life\"...

BIOLOGY IN YOUR LIFE - Life is a profound scientific undertaking - Organisms are so complex and are diverse having different functions, structures, manner of growth and origin. - Scientific principles helps us understand complexities of organisms - Biology means \"the study of life\". CHARACTERISTICS OF LIVING THINGS - Living things are made up of cells. - Living things reproduce. - Living things grow and develop. - Living things obtain and use energy. - Living things respond to their environment. TERMS TO REMEMBER: - Unicellular - A single cell can form an entire living organism. - Multicellular - composed of more than one cell, with groups of cells differentiating to take on specialized functions. - Sexual reproduction - requires that two cells from different individuals unite to produce the first cell of a new organism. - Asexual reproduction - is a single organism can reproduce without the aid of another. - Anabolism - is the process of putting together, or synthesizing complex substances into simpler substances. - Catabolism - the breakdown of complex into simpler ones using the release of energy. - Metabolism - is the sum total of all the chemical reactions in the body. - Homeostasis - is the process by which organisms respond to stimuli in ways to keep conditions in the body suitable for life. LEVELS OF ORGANIZATION Biosphere -\> Ecosystem -\> Community -\> Population -\> Individual Organism -\> Organ System -\> Organ -\> Tissue -\> Cell -\> Molecule -\> Atom WHAT ARE CELLS? - All organisms are composed of the fundamental unit of life, the cell. - The cell is the simplest unit of matter that is alive. - Cells are the defined as the structural and functional unit of life. WHAT IS A MICROSCOPE? - A microscope, from the Ancient Greek words **mikrós** or \"small\" and skopein or \"to look or see\" - It is a tool that is used to view smaller objects that the human eye can see. - Microscopy is the scientific field of study which is used to study minute structures and objects by a microscope. - It was in the 16th century when the first **compound microscope** was discovered by and credited to Zacharias Janssen. MOST COMMON TYPES OF MICROSCOPE 1. Simple Microscope A simple microscope is **simply a large magnifying glass with a shorter focal length that has a convex mirror with a small focal area**. The most common examples of this type of device are the handheld lens and eyepiece lens. Since it\'s only a simple microscope, **it only has one magnification level depending on what lens is used**. Therefore, simple microscopes are only **used for reading and magnifying non- complex items**. For instance, you can use a magnifying glass to zoom in the details of a map 2. Compound Light Microscope A compound microscope is the **most common type of microscope used today** it is basically a **microscope that has a lens or a camera on it that has a compound medium in between.** This compound medium allows for magnifications in a very fine scale. Compound microscopes **extremely useful for research on different areas**. it has made a big impact on science and technology in general. Some of its popular **uses are when viewing a scientific specimen for educational and research purposes.** 3. **Stereo Microscope** The stereo microscope, **dissecting or stereoscopic microscope**, is an **optical microscopy version designed specifically for low magnification imaging of a biological specimen**. It works through **reflecting light off the specimen\'s surface rather than transmitted through its medium.** 4. **Scanning Electron Microscope (SEM)** A scanning electron microscope is a very popular type of scanning electron microscopes, which **produces images of a material by scanning the sample with a high-powered beam of electrons**. The electrons interacting with atoms within the sample create different signals which contain data about the structure and topography of the material. **The images that are produced using these microscope instruments are highly accurate** as well as they can be viewed in high resolution using a microscope eyepiece or magnifier 5. Transmission Electron Microscope Transmission electron microscopy is an **optical microscopy method in which an electrical beam of electrons is transmitted through an unstained sample to create an optical image of the sample**. Instead of sending electrons to scan and bounce off the specimen as what SEMs do, TEMs **allow the electrons to pass through the thin sample**. The sample is usually an ultrathin slice less than 50 micrometers thick or an electrolyte suspension suspended on a grid of grid-like plates. DEVELOPMENT OF MICROSCOPE **Nimrud lens** The Nimrud lens -- **a piece of rock crystal** may have been used as a magnifying glass or as a burning-glass to start fires by concentrating sunlight. It is later unearthed by **Austen Henry Layard** at the Assyrian palace of Nimrud in modern-day Iraq. **First eyeglasses** **Salvino D'Armate** is credited with inventing the first wearable eye glasses **Early microscope** **Zacharias Janssen and his son Hans** place multiple lenses in a tube. They observe that viewed objects in front of the tube appear greatly enlarged. This is a forerunner of the compound microscope and the telescope. **Compound microscope** **Galileo Galilei** develops a compound microscope with a convex and a concave lens. **1625 -- First use of term 'microscope'** **Giovanni Faber** coins the name 'microscope' for Galileo Galilei's compound microscope. **1665 -- First use of term 'cells'** English physicist **Robert Hooke** publishes **Micrographia**, in which he coins the term 'cells' when describing tissue. The book includes drawings of hairs on a nettle and the honeycomb structure of cork. He uses a simple, single-lens microscope illuminated by a candle. **1830 -- Spherical aberration solved** **Joseph Jackson Lister** reduces spherical aberration (which produces imperfect images) by using several weak lenses together at certain distances to give good magnification without blurring the image. **1874 -- Abbe equation** **Ernst Abbe** writes a mathematical formula that correlates resolving power to the wavelength of light. Abbe's formula makes it possible to calculate the theoretical maximum resolution of a microscope. Explaining the Postulates of the Cell Theory DID YOU KNOW? - **Every organism,** no matter what size becomes when fully grown, **comes from a multicellular unit called \"cell\"**, A single unit of this cell **continuously divide and replicate to make up an organism.** - The cell theory states that **all organisms are composed of cells**. It also **has postulates that describes other properties of the cell** - Louis Pasteur (disproving spontaneous generation) is credited with conclusively **disproving the theory of spontaneous generation with his famous swan-neck flask experiment**. He subsequently **proposed that "life only comes from life."** - Anton Van Leeuwenhoek (father of microscopy) - is the **first to discover free-living algae Spirogyra cells in water in the pond in 1674 with the improved microscope**. The **living cells were first discovered** by Antony Van Leeuwenhoek. He observed living cells and called them **\'animalcules** Some small \'animalcules are now called **bacteria**. - The **existence of cells** was first discovered by an English scientist named **Robert Hooke**. In **1665**, Hooke was **able to observe these structural units in a cork using his compound microscope**. He then published this discovery that inspired other scientists to investigate more about cells. - Giovanni Faber coins the name " microscope" THE CELL THEORY - The Cell Theory is one of the **basic principles of Biology**. It was formally established in **1839** following the discoveries of Theodor Schwann and Matthias Schleiden - The theory originally **consists of three tenets**, the **third** of which was contributed by **Robert Virchow**. - The original postulates of the cell theory states that: 1. All living cells are made of cell - **Schleiden and Schwann\'s** discovery of cells **being present in both plant and animal tissue** led them to conclude that all living are made of cells. Basically, cells **make up the structure and organization of organisms** --- without the cells, there would be no tissue that would then make up the organs of the body. - Organisms may have different cell type: **Prokaryotic Cells** and **Eukaryotic Cells.** - **Matthias Jakob Schleiden -** He investigated plants microscopically and conceived that **plants were made up of recognizable units, or cells**. He thought plant growth came about through the production of new cells, which, he speculated, came from the nuclei of old cells. - Theodore Schwann - a German biologist who reached the same conclusion as Schleiden about **animal tissue being composed of cells**, ending speculations that plants and animals were different in structure. 2. Cells are the basic unit of life - The cells of an organism are where all **metabolic processes occur** that keeps the organism alive, hence it is called the **fundamental unit of life**. Its structure houses different molecules and compounds with different but cooperative functions. 3. Cells arise from pre-existing cells - Rudolph Virchow correctly revised the original third postulate of Schleiden and Schwann, that cells arise from spontaneous generation. Virchow\'s discovery stated that one cell essentially just splits numerous times forming new cells. - Rudolph Virchow - was studying cells under a microscope when he happens to see them **dividing and forming new cells**. He realized that living cells produce new cells through division. Based on this realization, Virchow proposed that living cells arise only from other living cells. THE MODERN CELL THEORY - The cell theory holds **true for all living things**, no matter how big or small, or how simple or complex. With the original postulates as foundation, scientists **discovered new information** about this fundamental unit of life and developed the \"Modern Cell Theory\". - With the **advancement of technology,** new discoveries about the cell allowed the revision of the cell theory. - The general accepted postulates of the modern cell theory are: 1. All living things are made of cells. 2. Cells come from pre-existing cells. 3. Cells are the basic unit of life. 4. **Cells contain hereditary information (DNA).** 5. **All cells are basically the same in chemical composition in organisms of similar species.** 6. **Energy flow (metabolism and biochemistry) happens in cells.** **Cells have three parts: the membrane, the nucleus, and the cytoplasm.** **The Endosymbiotic Theory** **The endosymbiotic theory is a scientific theory that proposes that some of the organelles in the eukaryotic cells, such as mitochondria and chloroplast, have originated from free-living prokaryotes** (bacteria and archaea). Endosymbiosis is the relationship between two organisms when one lives within the other organism, eventually benefiting both partners. **Endosymbiotic Theory** The endosymbiotic theory explains that when one organism, typically a microbe, takes up residence within the cell of another organism, over time, they form a close relationship that can be advantageous for both partners. The larger host cell provides a protected environment and essential nutrients. At the same time, the internalized microbe contributes its specialized functions, often becoming an organelle within the host cell**.** **The theory was conceptualized first by Konstantin Mereschkowsk in 1905 and then supported with evidence by Lynn Margulis in 1967.** **The Theory of Endosymbiosis in Timeline** The German botanist **Heinrich Anton de Bary** coined the term **'Symbiose'** to designate this coexistence. The concept of symbiosis, that two different organisms stably coexist and even give rise to a new type of organism, is attributed to **Simon Schwendener.** **19th Century** In 1905, **Russian biologist Konstantin Mereschkowski** suggested that the origin of eukaryotic cells involved the engulfment of smaller prokaryotic cells. Around the same time, German botanist Andreas Schimper proposed that chloroplasts in plant cells might have originated from independent photosynthetic organisms. **1960s-1970s** **In 1967, Lynn Margulis proposed** that eukaryotic cells, with their complex structures and organelles, resulted from symbiotic relationships between ancestral prokaryotic cells. He argued that mitochondria, the cellular powerhouses, were once free-living bacteria capable of aerobic respiration. Similarly, she suggested that chloroplasts originated from photosynthetic bacteria that became incorporated into host cells. **1980s-1990s** Researchers discovered striking similarities between the DNA of organelles like mitochondria and chloroplasts and the DNA of modern-day bacteria. Protists like single-celled organisms are found to host certain bacteria fixing nitrogen (nitrogen-fixing bacteria). **2000s-Present** **In the 21st Century, endosymbiosis forms the basis of the origin of mitochondria, chloroplast, and other organelles. It also explains the development of complex multicellular organisms and the coevolution of symbiotic partners.** **The Process of Endosymbiosis**  **Endosymbiosis** **According to the endosymbiotic theory, the symbiotic origin of eukaryotic cells is a multi-event process.** **1. Primary Endosymbiosis** It refers to the initial engulfment of a free-living bacterium by a host cell, creating a new organelle within the host cell. The most prominent examples of primary endosymbiosis are the origin of mitochondria and chloroplasts; both were once free-living cells. Here, two membranes surround the organelles; the inner is obtained from the bacterium, and the outer is derived from the host cell. **Origin of Mitochondria**: A eukaryotic cell engulfed a bacterium capable of aerobic respiration. This bacterium provides a valuable energy source through respiration. Over time, the host cell and the engulfed bacterium developed a mutually beneficial relationship. The bacterium became the mitochondrion, retaining its own DNA and membrane structure while working in tandem with the host cell**.** **Origin of Chloroplasts:** Here, an ancestral host cell captured a photosynthetic bacterium, which could convert sunlight into energy through photosynthesis. As with mitochondria, a symbiotic partnership formed, with the photosynthetic bacterium evolving into the chloroplast. It allowed the host cell to harness the power of photosynthesis for energy production. **2. Secondary Endosymbiosis** It involves a eukaryotic cell engulfing another eukaryotic cell already undergoing primary endosymbiosis. This secondary engulfment results in a more complex cellular arrangement, leading to the diversification of eukaryotic lineages and the emergence of new types of organelles. **Formation of Plastids:** These organelles involved in photosynthesis are found in various algae and plants. Different groups of algae have acquired plastids through secondary endosymbiosis, which consists of the engulfment of photosynthetic eukaryotic cells. In contrast to the two membranes of primary organelles, four membranes surround chloroplasts obtained by secondary endosymbiosis. In most cases, the nucleus of the engulfed cell disappears, with the remains of this nucleus still found lying between the two pairs of membranes. This structure is called a nucleomorph. **Thus, the endosymbiotic theory explains the presence of double-membraned organelles within protists.** **Evidence that Supports the Endosymbiotic Theory** **There are several proofs to support the Endosymbiotic Theory. However, the discovery of independent DNA (from the host) in mitochondria and chloroplasts supported the theory the most. The other evidences are as follows:** **Structural Similarities:** Mitochondria and chloroplasts share structural characteristics with free-living bacteria, such as double membranes and DNA. Both the organelles are almost of the same size as the bacterial cell. **Reproduction**: Mitochondria and chloroplasts replicate within the cell independently, similar to how bacteria reproduce. **Genetic Evidence**: The DNA within mitochondria and chloroplasts is more similar to bacterial DNA than the host cell's nucleus. **Evolutionary Relationships:** Analysis of genetic sequences shows that mitochondria and chloroplasts are more closely related to specific groups of bacteria than eukaryotic cells. However, the statement that mitochondria and chloroplasts are much larger than prokaryotic cells does not support the endosymbiotic theory. Describing the Structure and Function of Major and Subcellular Organelles ORGANELLES - An organelle is a **membrane-bound structure** within the cell. Its membrane is similar with the cell\'s lipid membrane that holds all the cell\'s components. - Each organelle in the cell performs a specific task wherein the combination of these tasks expresses the overall function of the cell. CELL ORGANELLES +-----------------------------------+-----------------------------------+ | **The Cell Theory** | **Contributors** | | | | | - All living things are made of | - Robert Hooke | | cells. | | | | - Theodor Schwann. | | - Cells are the basic unit of | | | life. | - Matthias Schleiden | | | | | - Cells arise from pre-existing | - Robert Virchow | | cells. | | +-----------------------------------+-----------------------------------+ - Cell Membrane - Golgi Body - Nucleus - Endoplasmic Reticulum - Mitochondrion - Lysosomes - Chloroplast - Cytoskeleton 1. PLASMA MEMBRANE 2. CELL WALL 3. NUCLEUS 4. CYTOPLASM 5. CYTOSKELETON 6. RIBOSOMES  7. ENDOPLASMIC RETICULUM 8. GOLGI BODY 9. MITOCHONDRIA 10. LYSOSOMES 11. PEROXISOMES FLAGELLA AND CILIA Flagella - A FLAGELLA IS A LASH-LIKE APPENDAGE THAT PROTRUDES FROM THE CELL BODY - The number of flagella is comparatively less (usually ranges from 1 to 8) - Flagella is comparatively longer in length - Beating pattern of Flagella involves circular, wave- like or propeller-like motion - Found in prokaryotic cells and eukaryotic cells - Flagella are of three types: Bacterial flagella, Archaeal flagella and Eukaryotic flagella Cilia - CILIA ARE SLENDER PROTUBERANCES THAT PROJECT FROM THE MUCH LARGER CELL BODY - The number of cilia is comparatively more (typically ranges in the thousands) - Cilia is usually shorter in length - Beating pattern of cilia is very complicated - Can move in a wide range of motions - Found in Eukaryotic cells - Cilia are of two types: Non-motile cilia and Motile cilia 12. CENTROSOME  BASAL BODIES 13. VACOULES 14. CHLOROPLAST