1. Biology - introduction and scope - 2024-25 (1).pptx

Introduction to Biology and its scope Chapter 1 and 4 Science – an approach to understand the natural world based on Inquiry, Analysis & Survey Search for information, explanation and answers to specific questions Then, what according to YOU is Biology? BIOLOGY –The sci...

Introduction to Biology and its scope Chapter 1 and 4 Science – an approach to understand the natural world based on Inquiry, Analysis & Survey Search for information, explanation and answers to specific questions Then, what according to YOU is Biology? BIOLOGY –The scientific study of life Usually, a combination of two main scientific approaches employed: 1. Discovery Science: Relies on verifiable observations and measurements of structures and processes Collection of DATA – e.g. Charles Darwin’s work in South America 2. Hypothesis-driven Science: Observations give rise to questions and efforts to seek answers – experimental investigations using the scientific method Done by formulating a hypothesis to explain the natural world, which is then tested What is a hypothesis? It is a tentative answer to a question, proposed explanation for a set of observations A tentative insight into the natural world; a concept that is not yet verified but if proven true, it would explain the phenomena observed THE SCIENTIFIC METHOD A series of steps providing a broad guideline for scientific investigations Not rigid – scientists can test a hypothesis many times and in different ways What makes a GOOD hypothesis? Any hypothesis may be revised or even rejected OBSERVATI ON  Applying Scientific Method to a Common Problem Observation - Maple trees lose their leaves in the fall. A possible explanation for this observation: - “cold weather causes maple trees to lose their leaves in the fall.” Is this statement testable? Grow maple trees in a warm enclosed environment such as a greenhouse and see if their leaves still dropped in the fall. Is this statement also falsifiable? If the leaves still dropped in the warm environment, then clearly temperature was not the main factor in causing maple leaves to drop in autumn. Determine whether the following statement is a scientific hypothesis? A) Air pollution from automobile exhaust can trigger symptoms in people with asthma. 1.No. This statement is not testable or falsifiable. 2.No. This statement is not testable. 3.No. This statement is not falsifiable. 4.Yes. This statement is testable and falsifiable B) Natural disasters, such as tornadoes, are punishments for bad thoughts and behaviours. C) Fresh water pond freezes more quickly in winter than the ocean does How does a HYPOTHESIS differ from a THEORY? Facts in the form of verifiable observations and repeatable experimental results, are the prerequisites of science A scientific theory - comprehensive explanation of many observations supported by abundant evidence Enough to spin off many new testable hypotheses Compared to a hypothesis, it is much broader in scope Hypothesis: "Mimicking poisonous snakes is an adaptation that protects nonpoisonous snakes from predators.” Theory: "Adaptations such as mimicry evolve by natural selection.“ Hypothesis 1 – White fur of polar bears is an Hypothesis 2 - unusual bone structure of a adaptation for survival in the Arctic habitat hummingbirds’ wing is an evolutionary adaption for better nectar gathering - Two SEEMINGLY unrelated hypotheses; tied together by a single theory: “Adaptations to the local environment evolve by NATURAL SELECTION” Theories become widely accepted only if they are validated by significant number and variety of observations and evidences without The nature of life – what distinguishes the living from the non-living? The Properties of life! 1. Order – life is complex but orderly organized (Cellular organization –cell basic unit) 2. Regulation – maintenance of internal environment 3. Growth and development - Information in the DNA controls the pattern of growth and development 4. Energy processing – Energy uptake and expenditure to perform all activities 5. Response to the environment - Stimulus 6. Reproduction - Population growth through propagation of their own kind 1) ORDER Living organisms are highly organized – complex but ordered organization: ▪ coordinated structures consisting of one or more cells -fundamental units of life ▪ Even unicellular organisms like bacteria show complex organization ▪ Inside each cell, atoms make up molecules, which make up cell organelles and structures ▪ Multicellular organisms: cells - tissues –organs-organ system –organism ▪ similar cells form tissues ▪ Tissues- collaborate to create organs (body structures with a distinct function). Organs work together to form organ systems. ▪ Information flows in an ordered manner at all levels of organization 2) REGULATION ▪ Outside environment may change drastically but internal environment is always kept constant through various adjustments ▪ Homeostasis - maintenance of a stable internal environment, even in the face of a changing external environment For instance: ▪ Osmoregulation ▪ Thermal regulation ▪ Hot – sweating, dilation of blood vessels => heat loss ▪ Cold – vasoconstriction, rapid muscle movements (?) => heat Even the smallest organisms are complex and generation require multiple regulatory mechanisms to coordinate internal functions, respond to stimuli, 3) GROWTH & DEVELOPMENT ▪ Information encoded in the DNA controls the pattern of growth and development in ALL organisms ▪ Living organisms undergo regulated growth ▪ Individual cells become larger in size – GROWTH (unicellular organisms) ▪ Multicellular organisms – increase in number of cells through cell division => GROWTH ▪ Body Growth depends on anabolic pathways - building large, complex molecules (proteins and DNA, the genetic material) 4) ENERGY PROCESSING All organisms use a source of energy for their activities in order to carry out life processes Some organisms capture energy from the sun and convert it into chemical energy in food (photosynthesis) others use chemical energy in molecules they take in as food (cellular respiration) Transformation of energy from one form to another. Example - Food Chain ▪ METABOLISM - Vast network of interconnected chemical reactions within living cells The California condor (Gymnogyps californianus) uses chemical energy derived from food to power flight ▪ Energy released from food after it is broken down, processed and harnessed as chemical bond energy - usable form ATP ▪ Some energy emitted as heat ▪ Atoms and molecules – recycled –build new tissues ▪ Energy & matter transformation is Important 5) RESPONSE TO THE ENVIRONMENT ▪ All organisms respond or react to environmental stimuli ▪ For example ✔Response to infection ✔Carnivorous -Venus fly trap ✔Response to touch –Mimosa pudica ✔Tropism – growth or movement of an organism in response to an external stimulus ▪ An example of a common tropism in plants is phototropism (or light response) ▪ Even tiny bacteria can move toward or away from certain chemicals (a process called chemotaxis) 6) REPRODUCTION ▪ Reproduction – Propagation of their own kind ▪ Ensures survival and growth of the population ▪ Single-celled organisms - reproduce by first duplicating their DNA, and then dividing it equally as the cell prepares to divide to form two new cells ▪ Splitting into two – BINARY FISSION ▪ Multi-cellular organisms – different methods, such as vegetative propagation, fusion of gametes etc. 6) EVOLUTION Populations of living organisms can undergo evolution - genetic makeup of a population may change over time Evolution is a long-term process wherein changes occur at the genetic level for a better functioning and survival as a race Giant leaf insect - evolved to provide camouflage in its environment ▪ Evolutionary change is a central, unifying phenomenon of all life Giant leaf insect (Phyllium giganteum) EVOLUTION OF POLAR BEARS The polar bear has evolved over time from the common brown bear by changing its fur colour to white, the ideal colour to blend in with its ice-covered surroundings. Researchers believe that the brown bear migrated to the north during a warmer climate period and when a cold period subsequently set in, a group of brown bears may have become isolated and therefore forced to quickly adapt to the new colder conditions. www.cell.com/cell/abstract/S0092-8674(14)00488-7  MAJOR THEMES IN BIOLOGY 1. Evolution - by natural selection - core theme that unifies all of biology 2. Structure-Function relationship - correlation seen at every level of biological organization (structure of lungs - gaseous exchange) 3. Information flow – Life’s functions proceed as intended through transmission of information (genes, inter-cellular communication etc.) 4. Energy transformations – Energy generation and transformation from one form to another sustains all life 5. Interconnections within systems - study of life extends from microscopic scale to global; all biological systems depend on interaction between various components Atoms – molecules – organelles – membrane bound cells – tissues – organs - organ systems – organism - Population – community - communities interact with their environment - Ecosystem (all living organisms in a particular place and all nonliving components of environment) - Sum of all ecosystem and communities on EARTH – BIOSPHERE (all places where life exist)  MAJOR THEMES IN BIOLOGY 1. Evolution - by natural selection - core theme that unifies all of biology 2. Structure-Function relationship - correlation seen at every level of biological organization (structure of lungs - gaseous exchange) 3. Information flow - every cell contain information in the form of genes, hereditary units of information 4. Energy transformations - from one form to another makes life possible 5. Interconnections within systems - study of life extends from microscopic level of molecules, all biological systems from molecules to ecosystems depend on interaction between components Atoms – molecules –organelle –membrane bound cells – tissue – organ - organ system – organism - Population – community - communities interact with their environment - Ecosystem (all living organisms in a particular place and all nonliving components of environment) - Sum of all ecosystem and communities on EARTH – BIOSPHERE (all places where life exist) 1) EVOLUTION Natural selection - does not promote changes - edits the changes that have already occurred – product of natural selection is ADAPTION Examples - Fur color in bears –polar bears and brown (similar species - share common ancestor) Resulted from Natural selection operating in their respective environment Finches of Galapagos Island – Darwin measured changes in beak size in a population of ground finches - dry and wet years Dry years - preferred small seeds in short supply – birds have large seeds to eat – Advantageous for birds with bigger beaks – greater reproductive success Wet years- small seeds are abundant – smaller beaks more efficient in eating smaller seeds Average beak depth decreased over generations Changes in beak structure are measurable evidence of natural selection Development of antibiotic resistance bacteria Artificial selection – selecting breeding stocks with certain traits Plants we grow today have little resemblance to their wild relatives, customized crop ADAPTATION 🡪 NATURAL SELECTION 🡪 EVOLUTION Evolution of Polar Bears Evolution of Beak shape in Darwin’s finches Application of Natural Selection 🡪 Artificial Abuse of Natural Selection Selection Antibiotic resistance in Plant and animal cattle breeding  Theme 2: The Relationship of Structure to Function Ribonuclease A (an enzyme/protein) – Structure: A pocket to fit RNA substrate Human Lungs – Structure: Human Lungs – Function: 600sqft in surface area (only 24cm Holds 6L of O2 in height!!!) Ribonuclease A – Function: Cleaves RNA THEME 3) Information flows in an ordered manner at all levels of organization THEME 5) Interconnections within biological systems Interconnections within biological systems  Diversity of life There are millions of organisms in the biosphere that fulfil that definition of life. In order to study them using scientific process we need to group them. All of us have a general sense of grouping. Can you apply that on the following: Taxonomy gives us a scientific basis for grouping  Diversity of life Species : Taxonomic group whose members can interbreed -share a genetic heritage Population - group of organisms living in the same place and time and are capable of interbreeding - producing healthy fertile offspring TAXONOMY Branch of biology that names and classifies species by grouping them into logical categories. A classification of organisms into groups based on similarities of structure or origin etc. Taxonomists use morphological, behavioral, genetic and biochemical observations an arrangement of species into hierarchy of broader and broader ⮚ Do you recognise these two organisms? ⮚ Would you classify them in the same group – same species? Why or why not? Classification of living forms On broadest level - Biologists divide the diversity of life into 3 main domains: Archae, Eubacteria, Eucarya Every organism on earth belong to one of three domains DOMAIN EUBACTERIA Eubacteria- “eu”=true Small, prokaryotic, single celled organisms ranging in size from 1 - 10 µm Lack nucleus & membrane bound organelles Cell wall contains a complex organic molecule called Peptidoglycan DOMAIN ARCHAEA Archaea- “archaios”=ancient Prokaryotic cell structure DNA of Archaea have large proportions of genes that are different from Eubacteria Cell membranes have unique chemical structures. CM do not contain fatty acids but instead branched molecules called ISOPRENES Also known as extremophiles- they are found in extreme environments  Domain Eukarya includes three main Kingdoms- most members are multicellular Kingdoms are distinguished partly by how the organism obtains food Plantae: produce their own food- Photosynthesis -autotrophic Fungi: decomposers, obtain their food by digesting dead organisms and organic waste -heterotrophic Animalia: obtain food by ingesting and digesting other organisms - heterotrophic Eukaryotes not belonging to either of the three kingdoms fall into a catch all group: Protists Protists are mostly single celled microscopic organisms such as amoeba or multicellular such as seaweeds. Other examples protozoa, unicellular algae, and slime molds The Microscopic World of Cells Cell theory states that all living things are composed of cells and that all cells come from earlier cells every cell in our body (and in every other living organism on Earth) was formed by division of a previously living cell © 2016 Pearson Education, Inc.  The Two Major Categories of Cells The countless cells on Earth fall All cells have several basic into two basic categories features: Prokaryotic cells include They are all bounded by a thin Bacteria and plasma membrane Archaea Inside all cells is a thick, jelly-like fluid called the cytosol - cellular Eukaryotic cells include components are suspended 1. protists All cells have one or more 2. plants chromosomes carrying genes 3. fungi, and made of DNA 4. animals All cells have ribosomes, tiny © 2016 Pearson Education, Inc. structures that build proteins The Two Major Categories of Cells Prokaryotic cells are older than eukaryotic cells A prokaryotic cell lacks a nucleus Prokaryotes appeared DNA is coiled into a nucleus-like about 3.5 billion years region called the nucleoid, ago No nuclear membranes Eukaryotes appeared about 2.1 billion years Eukaryotic cells ago Only eukaryotic cells have organelles, membrane-enclosed Prokaryotic cells are structures that perform specific usually smaller than functions. eukaryotic cells and simpler in structure The most important organelle is the nucleus, Education, © 2016 Pearson houses Inc. most of a eukaryotic cell’s Table 4.1 Cell wall-rigid covering outside the plasma membrane protects the cell and helps maintain its shape Plasma membrane (encloses cytoplasm) Cell wall (provides rigidity) Capsule (sticky coating) Flagella (for propulsion) Ribosomes (synthesize proteins) Colorized TEM Nucleoid (contains single circular bacterial chromosome) Pili (attachment structures) Figure 4.2 Prokaryotes can have Pili - short projections for attachment or adhesion to surfaces Flagella- long projections to propel them through their liquid environment capsules make bacterial surface components more slippery, helping the bacterium to escape engulfment by phagocytic cells An Overview of Eukaryotic Cells Eukaryotic cells - fundamentally similar Cytoplasm - Region between the nucleus and plasma membrane The cytoplasm of a eukaryotic cell consists of various organelles suspended in the liquid cytosol Most organelles are found in both animal and plant cells. But there are some important differences: Only plant cells have chloroplasts (where photosynthesis occurs) Only animal cells have lysosomes (bubbles of digestive enzymes surrounded by membranes) © 2016 Pearson Education, Inc. Figure 4.3 IDEALIZED ANIMAL CELL Centriol Not in most Ribosome Lysosome plant cells e s Cytoskeleton Plasma membrane Nucleus Cytoplasm Mitochondrion Rough endoplasmic Smooth IDEALIZED PLANT CELL reticulum (ER) endoplasmic Golgi Cytoplasm apparatu reticulum (ER) Cytoskeleton s Mitochondrion Central Not vacuole Cell animal Nucleu in wall Chloroplas cells Rough s t endoplasmic reticulum (ER) Ribosome s Plasma membrane Smooth endoplasmic Channels between Golgi cells reticulum (ER) apparatus  microtubules microtubules mitochond (partof (part of rion cytoskeleton) cytoskeleton) chloropl chloropl ast ast Golgi central central complex vacuole vacuole smooth endoplasmic reticulum vesi vesi cle cle rough cell cell endoplasmic wall wall reticulum plasma membr ane nucleo nucleo nucle nuclear lus lus nucle chroma chroma pore us us nuclear nuclear tin tin intermed envelope envelope iate filaments free free riboso riboso ribosome ribosome END