Introduction to Biology PDF

Introduction to Biology  What is Biology? ØBiology is the scientific study of living things (organisms) both alive and dead (fossils).  Main branches of Biology v Zoology v Anatomy v Botany v Physiology v Microbiology...

Introduction to Biology  What is Biology? ØBiology is the scientific study of living things (organisms) both alive and dead (fossils).  Main branches of Biology v Zoology v Anatomy v Botany v Physiology v Microbiology v Immunology v Virology v Neuroscience v Parasitology v Cell Biology v Mycology v Molecular Biology v Entomology v Genetics v Marine Biology v Biochemistry v Ecology v Biotechnology v Evolutionary Biology v Paleontology  Specialized fields within Biology ü Biophysics ü Pharmacology ü Dermatology ü Astrobiology ü Toxicology ü Pathology ü Developmental Biology ü Biostatistics ü Agricultural Biology ü Biogeography ü Cryobiology ü Radiobiology ü Systems Biology ü Ornithology ü Synthetic Biology ü Herpetology ü Taxonomy ü Ichthyology ü Chronobiology ü Limnology ü Biometrics ü Ethology ü Bioinformatics ü Oncology  What is the goal of Biology? ØThe goal: discovering and understanding the underlying unity and diversity of the complex processes that make up life.  What distinguishes living things from nonliving things? v Cellular Structure and function v Growth v Developpment v Metabolism v Homeostasis v Response to stimuli v Reproduction v Adaptation v Evolution v Limited lifespan  All living things are made of cells Ø Latin “cellula” = small room Ø Cell: a small membrane bound unit filled with a concentrated aqueous solution of chemicals with reproduction capacity. ØAll have similar cellular structure (the same lipid containing membrane, organelles, etc).  All living things are made of cells Ø All cells have similar chemical composition in their cells: ü a common set of chemical compounds (carbohydrates, fatty acids, nucleic acids, and amino acids) ü same 20 amino acids, same lipids, same sugars ü only six types of elements (hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur) ü same chemical groups (methyl, hydroxyl, carboxyl, carbonyl, phosphoryl, amino and thiol)  All living things have genetic information in their cells Ø Their genetic information is stored in DNA (deoxyribonucleic acid). Ø DNA molecules are composed of four different subunits called nucleotides. ØAll DNA in a cell constitutes its genome. ØA segment of DNA that contains the instructions for making a protein or an RNA is called a gene.  All living things use their genetic information in the same way Ø genetic information flows from DNA to RNA (transcription) and from RNA to protein (translation). ü They use a universal genetic code to build proteins from their genomic information.  All living things grow Ø The mass of the organism increases by: -An increase in cell number -An increase in cell size  All multicellular living things develop from a single cell ØDuring development specialized cells appear from non-specialized cells. Ø This process of specialization is called cell differentiation. ØCell differentiation involves changes in gene expression.  All living things extract energy and raw materials from the environment ØLiving organisms obtain nutrients from their environment. ØBiochemical reactions break down nutrient molecules. ØChemical breakdown produces building blocks for structures and energy for cell works (mechanical, biochemical and electrical).  All living things regulate their internal environment ØMaintenance of a constant internal enviroment is called homeostasis. ØHomeostasis requires cell activity regulation. ØSensory, effector and signaling mechanisms help integrate information. ØThe major information systems of animals are the nervous, hormonal, and immune systems. ØThey use chemical and electric signals to process information. All living things respond to their environment and reproduce  The genetic information of all living things changes overtime ØPermanent changes in DNA sequence are called mutations.  All living things evolve ØMutations lead to differences among individuals in a population. ØThese differences affect their chances of survival and reproduction. ØThe most adapted individuals survive and reproduce (natural selection). Ø Mutations and natural selection account for the evolution of biodiversity on earth.  All these similarities point to a common ancestor Ø These similarities indicated that the diverse organisms alive today all originated from one life form.  Biologists trace the evolutionary tree of life ØIdentification, analysis and quantification of similarities and differences among species help construct phylogenetic trees. ØPhylogenetic trees display the evolutionary history of different groups of organisms.  Biologists trace the evolutionary tree of life ØEach species is given a scientific name (binomial name). Biologists estimate that there may be up ØThe first part to indicates 100 millionthe distinct genus and the second species part, things of living the species (ex: Homo onsapiens) our planet ØUp to 100 million species are estimated to live on earth The history of life on earth ØEarth formed around 4.6 billion years ago (ya). ØLife appeared 600 million year later (~4 billion ya). ØPhotosynthesis: 2.5 billion ya ØEukaryotic cells: 2 billion ya ØMulticellular organisms: 600 million ya ØModern humans: 500.000 ya  Life appeared through chemical evolution ØThe critical step for the evolution of life was the appearance of nucleic acids. ØNucleic acids could reproduce themselves and serve as templates for the synthesis of proteins.  The first cell appeared by the enclosure of biological molecules by a lipid membranes Ø Fatty acids make spherical structures called liposomes. Ø In a primordial ocean, such membranous structures could have enveloped complex biological molecules.  Photosynthetic organisms changed earth’s atmosphere ØPhotosynthesis allows some organisms to capture energy from the Sun. ØAerobic metabolism is far more efficient than anaerobic metabolism in extracting energy from nutrient molecules. ØWith oxygen accumulation life moved onto land (500 million ya). Eukaryotic cells probably evolved in several steps Ø Nuclear membranes and the endoplasmic reticulum (ER) may have evolved through invagination of the plasma membrane. Ø Mitochondria are probably ancient aerobic prokaryote engulfed by a pre- eukaryotic cell. Ø Chloroplasts are thought to have originated when a eukaryotic cell with mitochondria engulfed a photosynthetic prokaryote. Endosymbiosis is probably responsible for the appearance of mitochondria and chloroplasts. Multicellular organisms probably evolved from aggregated eukaryotic cells Aggregation: Single-celled organisms began to form colonies or groups. This allowed cells to work together and share resources Specialization: Within these colonies, cells started to specialize in different functions. Evolution led to the appearance of the three domains of life  Discoveries in biology can be generalized from model systems Arabidopsis thaliana Saccharomyces cerevisiae Drosophila melanogaster Escherichia coli (E. coli ) Caenorhabditis elegans Zebrafish (Danio rerio) House mouse (Mus musculus)  Biologists investigate life through experiments that test hypotheses ØObservation and quantification are important skills in science. ØScientific methods combine observation, experimentation and logic (inductive/deductive logic). Ø Good experiments can falsify hypotheses (controlled/comparative experiments). ØStatistical methods are essential scientific tools (null hypothesis, probability of error).  Comparative experiments Ø collecting and comparing data from two or more groups Ø groups that differ in multiple unknown ways Ø It starts with the prediction that there will be a difference between the groups Ø difficult to isolate the impact of one variable and to generalize Ø it is challenging to control all variables Ø other variables (confounding variables) may influence the results and make it difficult to isolate the impact of the variables of interest.  Controlled experiments Ø one predicts that a critical factor or variable affects a phenomenon Ø all variables are held constant between the two groups Ø studied organisms/cells are divided into two groups: ü manipulated group called “experimental” ü unmanipulated group called “control” Ø only the factor of interest is manipulated in the experimental group Ø The effect of the manipulated variable is investigated. Ø Not easy to design, hard to change just one factor in a biological system  Corals in hot water: a scientific investigation Ø Reef-building corals provide: -shelter, breeding grounds, and food for marine species. -storm protection -are source of natural beauty Ø Ocean warming causes coral to lose their essential microscopic algal partners (dinoflagellates). Ø This process is known as 'coral bleaching'.  Corals in hot water: a scientific investigation Ø Question: Are corals from warmer pools more resistant to bleaching? Ø Hypothesis: corals from warm pools are less subject to bleaching under heat stress than are corals from cool pools. Ø Method: 1. Transplant corals from warm and cool pools into laboratory aquariums. 2. Subject experimental corals to heat stress 3. Measure coral bleaching as the ratio of chlorophyll in the corals exposed to heat stress versus corals not exposed to heat stress. A ratio of less than 1.0 indicates higher bleaching in the heat-stressed corals than in the controls.  Corals in hot water: a scientific investigation Ø Results: 1. Corals from both cool pools and warm pools exhibited higher bleaching under heat stress. 2. However, the cool-pool corals showed higher average levels of bleaching than the warm-pool corals did. Ø Conclusion: The warm-pool corals were less affected by heat stress than the cool-pool corals. The difference could be due to either genetic or epigenetic (gene expression) adaptation.  Whay understanding Biology is important? ØGenetic engineering allows the production of higher yielding and resistant crop plants. ØGenetically improved crop plants: -with the toxin gene from Bacillus thuringiensis -resistant to herbicides -β-Carotene producing rice -flood tolerant rice -salt tolerant tomato plants  Whay understanding Biology is important? ØAccurate scientific data help take informed decisions (ex Atlantic bluefin tunas) ØKnowledge of pathogenic organisms and their pathogenesis helped develop vaccins. ØKnowledge of genes and mechanisms responsible of genetic diseases helped find treatments or cures.  Learning outcomes Ø List the major characteristics shared among all living things and outline, with examples, ways in which cells share a fundamental chemistry. Ø Explain the concepts of gene, genome, genetic information flow, cell differentiation, energy flow and material cycling, homeostasis, mutation, natural selection, adaptation, evolution and phylogenetic tree. Ø Explain how genetic information allows to establish evolutionary relationships and describe what information can be represented in a phylogenetic tree.  Learning outcomes Ø Explain the history of life on earth (appearance of the first cell, importance of photosynthesis in the history of life, appearance of eukaryotic cells, appearance of multicellularity and the evolution of the three domains). Ø Explain the principles of scientific method, contrast the concept of controlled and comparative experiments. Ø Explain why understanding biology is important for health, agricultural improvement and environment preservation. Provide examples.