Lecture 1: Introduction to Biology PDF

Lecture 1: Introduction to biology Prof. Dr. Nahida Mohammed Introduction to biology: Biology: from the Greek word (Bios which means life, Logos which means study of), is the study of living organisms, divided into many specialized fields that cover their morpholo...

Lecture 1: Introduction to biology Prof. Dr. Nahida Mohammed Introduction to biology: Biology: from the Greek word (Bios which means life, Logos which means study of), is the study of living organisms, divided into many specialized fields that cover their morphology, anatomy, behavior, origin, and distribution. History: ❖ Aristotle (384-322 B.C.) - Famous Greek Philosopher. - Pioneered Zoology. - First to classify living things. - Divided the plants into herbs, shrubs and trees and animals into land dwellers, water dwellers and air dwellers. ❖ Galen (A.D. 131-200) - Greek physician who describes the anatomy of the human body based on dissections of apes and pigs. - showed that arteries carry blood. - His description contained many errors, however, and were unchallenged for 1,300 years. ❖ Versalius (1514-1564) - Father of Modern Anatomy. - Made the first studies on human anatomy by dissecting corpses. ❖ William Harvey (1578-1657) - English physician who showed conclusively that the heart pumps the blood and the blood circulates. - He stimulated the development of anatomy by proving the principle that structure and function must be studied together. - Gave an accurate account of the mechanism of the circulatory system. ❖ Marcello Malpighi (1628-1694) - Italian physician and anatomist who was the founder of microscopic anatomy. - In 1661, he discovered the capillaries. - observed the microscopic components of the liver, brain, kidneys, spleen, bone, and the inner, or what came to be known as the Malpighian, layer of the skin. - discover red blood corpuscles. Lecture 1: Introduction to biology Prof. Dr. Nahida Mohammed ❖ Anton van Leeuwenhoek (1632-1694) - Invented a simple microscope. - His most important discoveries were microorganisms (including bacteria), sperm cells and single-celled organisms called protozoans by using microscope. ❖ Carolus Linnaeus (1707-1778) - Father of Taxonomy. - binomial system of nomenclature. ❖ Gregor Mendel (1822-1884) - Father of Genetics. ❖ Charles Darwin (1809-1882) - His book "Origin of Species" presents the theory of evolution by natural selection. ❖ James Watson and Francis Crick. - They discover DNA double helix model. ❖ Frederick Sanger and Walter Gilbert - DNA sequencing technology. ❖ Georges J.F Kohler and Cesar Milstein - Use antibodies in medicine as diagnostic and therapeutic agents. ❖ Kary Mullis - Uses of polymerase chain reaction in diagnosis of genetic diseases. Characteristics of Life: 1. Cellular composition: Made up of at least one cell. Unicellular - made of one cell (bacteria, amoeba, paramecium) Multicellular - made up of two or more cells (plants, fungi, animals) 2. Growth: Increase in cell size (unicellular) and/or an increase in cell number (multicellular) 3. Reproduction: Asexual- cell division (mitosis one cell becomes two Ex: bacteria Sexual- union of sex cells (sperm and egg) Ex: plants and animals 4. Movement There are 3 types: A- Place to Place- (ex: bear running, bird flying, etc) B- External Part- (ex: phototropism, plants orient leaves toward sun) C- Internal- (ex: cytoplasmic streaming) Lecture 1: Introduction to biology Prof. Dr. Nahida Mohammed 5. Adaptation It means changing to meet the needs of the environment Examples: Bird migration- behavioral adaptation 6. Metabolism: Means set of chemical reactions that convert "food" into energy. 7. Specific organization: Certain parts do specific jobs (ex: heart, nucleus, chloroplasts, etc. 8. Homeostasis: Maintaining the same state Homeo = same, steady Stasis = state Examples: - Water balance inside and outside of cell - Human body temperature * Cells function best when these are in balance 9. Responsiveness: Reaction(s) to various stimuli Examples of stimuli: light, heat, PH, vibration, smell, etc.- earthworms respond to all of these. What is the Cell It Is the structural and functional unit of all living organisms and sometimes called the building block of life. History of the Cell: Discovering the Cell: The discovery of the cell would not have been possible if not for advancements to the microscope. Interested in learning more about the microscopic world, scientist Robert Hooke improved the design of the existing compound microscope in 1665. His microscope used three lenses and a stage light, which illuminated and enlarged the specimens. These advancements allowed Hooke to see something wondrous when he placed a piece of cork under the microscope. Hooke detailed his observations of this tiny and previously unseen world in his book, Micrographia. To him, the cork looked as if it was made of tiny pores, which he came to call “cells” because they reminded him of the cells in a monastery. Lecture 1: Introduction to biology Prof. Dr. Nahida Mohammed Not long after Hooke’s discovery, Dutch scientist Antonie van Leeuwenhoek detected other hidden, minuscule organisms—bacteria and protozoa. Van Leeuwenhoek was a master microscope maker and perfected the design of the simple microscope (which only had a single lens), enabling it to magnify an object by around two hundred to three hundred times its original size. What van Leeuwenhoek saw with these microscopes was bacteria and protozoa, but he called these tiny creatures “animalcules”. In the nineteenth century, biologists began taking a closer look at both animal and plant tissues, perfecting cell theory. Scientists could readily tell that plants were completely made up of cells due to their cell wall. However, this was not so obvious for animal cells, which lack a cell wall. Many scientists believed that animals were made of “globules.” German scientists Theodore Schwann and Mattias Schleiden studied cells of animals and plants respectively. These scientists identified key differences between the two cell types and put forth the idea that cells were the fundamental units of both plants and animals. At the turn of the century, attention began to shift toward cytogenetics, which aimed to link the study of cells to the study of genetics. In the 1880s, Walter Sutton and Theodor Boveri were responsible for identifying the chromosome as the hub for heredity. forever linking genetics and cytology. Later discoveries further confirmed and solidified the role of the cell in heredity, such as James Watson and Francis Crick’s studies on the structure of DNA. The discovery of the cell has had a far greater impact on science than Hooke could have ever dreamed in 1665. In addition to giving us a fundamental understanding of the building blocks of all living organisms, the discovery of the cell has led to advances in medical technology and treatment. Today, scientists are working on personalized medicine, which would allow us to grow stem cells from our very own cells and then use them to understand disease processes. Principles of Modern Cell Theory All organisms composed of cells and cell products. A cell is the simplest structural and functional unit of life. An organism's structure and all of its functions are ultimately due to the activities of its cells. Cells come only from preexisting cells, not from nonliving matter. Because of this common ancestry, the cells of all species have many fundamental similarities in their chemical composition and metabolic mechanisms. Lecture 1: Introduction to biology Prof. Dr. Nahida Mohammed Cell types: There are two types of cells in general 1. Prokaryotic cell: Cell that lack membrane-bound organelles for example bacteria. 2. Eukaryotic Cells: Cell that have membrane-bound organelles for example animal and plant cell. Eukaryotic Vs. Prokaryotic Cells: Prokaryotic and eukaryotic cell differ in size and complexity. Similarities All cells are surrounded by a plasma membrane. The semi-fluid substance within the cell is called "cytosol", containing the cell organelles. All cells contain chromosomes which have genes in the form of DNA. All cells have tiny organelles called "Ribosomes" that make proteins. Lecture 1: Introduction to biology Prof. Dr. Nahida Mohammed Differences Feature Eukaryotic cell Prokaryotic cell The nuclear body is bounded The nuclear body is not bounded by a nuclear membrane having by a nuclear pores connecting it with the pores membrane. endoplasmic reticulum It usually contains one circular It contains one or more paired, chromosome composed of linear chromosomes composed Nuclear body deoxyribonucleic composed of of deoxyribonucleic acid deoxyribonucleic acid (DNA) (DNA) associated with histone associated with histone-like proteins. proteins. A nucleolus is present. There is no nucleolus. The nuclear body is called a The nuclear body is called a nucleus. nucleoid. The nucleus divides by The cell usually divides by binary mitosis. fission. There is no mitosis. Haploid (1N) sex cells in Cell division Prokaryotic cells are haploid diploid or 2N organisms are produced Meiosis is not needed. through meiosis. Membrane bounded present absent organelles size Generally, much bigger smaller Eukaryotic cell can be divided into: 1. Animal cell. 2. Plant Cell. Lecture 1: Introduction to biology Prof. Dr. Nahida Mohammed Feature Animal Cell Plant Cell Nucleus Present Present Mitochondria Present Present Cytoplasm Present Present Chloroplast Absent Present Golgi Apparatus Present Present Cell Wall Absent Present Plasma membrane Present Present Microtubules/microfilaments Present Present Lysosomes Occur in cytoplasm Usually not evident May be found in some May be found in some Flagella cells cells Ribosomes Present Present Endoplasmic reticulum Present Present (Smooth and Rough) Plastids Absent Present One or more small One, large central Vacuole vacuoles (Much smaller vacuole taking up 90% than plant cells) of cell volume Present Present in lower plant Centrioles forms Round (irregular shape) Rectangular (fixed Shape shape) Cilia Present Very rare Human cell size - most range from 10 - 15 µm in diameter - egg cells (very large)100 µm diameter, visible to naked eye - nerve cell over 1 meter long, muscle cell up to 30 cm long, (too slender to be seen) Limitations on cell size - As cell enlarges, volume increases faster than surface area so the need for increased nutrients and waste removal exceeds ability of membrane surface to exchange.