BIO 101 Notes 2024 PDF

**Classification of Living Things & Naming Organism** A living thing pertains to any organism or a life form that possesses or shows the characteristics of life or being alive. They may be distinguished from non-living things in their ability to carry on life processes such as movement, respiration...

**Classification of Living Things & Naming Organism** A living thing pertains to any organism or a life form that possesses or shows the characteristics of life or being alive. They may be distinguished from non-living things in their ability to carry on life processes such as movement, respiration, growth, responsiveness to environmental stimuli and reproduction. Examples of living things include bacterium, animals, plants and fungus. An individual living thing is known as an organism. And seven characteristics distinguish a living organism from its non-living counterparts. **These characteristics are**; 1. Nutrition 2. Reproduction 3. Movement 4. Excretion 5. Growth 6. Reproduction 7. Sensitivity Nutrition: This is the process by which an organism obtains energy and raw materials from nutrients such as proteins, carbohydrate and fats. Respiration: Is the release of energy from food substances in all living cells. Living things break down food within their cells to release energy for respiration. Movement: It has been established that all living things move. How they move, however, varies. For example, the way humans move is different from how plants move. Excretion: This is defined as the removal of toxic materials, the waste products of metabolism and excess substances from the body. All living things that ingest must excrete as a result of the many chemical reactions occurring in a cell. Growth: Often, it involves using food to produce new cells. It is the permanent increase in cell number and size. Reproduction: All living things can produce offspring. Sensitivity: All living things can sense and respond to stimuli around them. Be it squinting of the eyes as a response to light, increased urination as a response to cold weather, retention of water as a response to heat and so on. Definition of Basic Terminologies 1. Taxonomy: is the practice and science of categorization or classification. It is the way different organisms are named, classified, and described. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. This system gives each species its unique name, making it easier to keep track of species. It was invented in the 18th century by Swedish botanist Carolus Linnaeus, which only had two layers of classification and is known as the Linnaean system. 2. Binomial nomenclature: is an internationally agreed system of naming an organism. In taxonomy, binomial nomenclature (\"two-term naming system\"), also called binomi*n*al nomenclature (\"two-name naming system\") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomial name (which may be shortened to just \"binomial\"), a binomen, binominal name or a scientific name. A binomial name is comprised of two parts. They are (1) the generic name (genus name) and (2) the specific name (or specific epithet, in botanical nomenclature). 3. Kingdom: This is the highest category in the hierarchical classification of organisms created by Carolus Linnaeus around 1750. Linnaeus recognized two kingdoms, plants and animals, a scheme that worked reasonably well for large multicellular organisms but failed as microscopes revealed diverse unicellular organisms. In 1959, Robert Whittaker devised a five-kingdom system that maintained kingdoms Plantae and Animalia but added kingdoms Monera, Protista, and Fungi. Sometimes you may have subgroup like sub Kingdom. 4. Phylum: This is the next level of classification and is more specific than the kingdom. In the Kingdom Animalia for example, there are 35 phyla that includes Porifera, Chordata, Arthropoda, etc. 5. Class: Class was the most general rank in the taxonomic hierarchy until the introduction of phyla. The classes used today are different from those proposed by Linnaeus. Within the Kingdom Animalia, there are about 108 classes including Mammalia, Reptilia, and Aves. 6. Order: Order is a more specific rank than class. The order constitutes one or more than one similar family. There are around 26 orders in class Mammalia only and they include Primates and Carnivora. 7. Family: This category of taxonomic hierarchy includes various genera that share a few similarities. For example, in the order Carnivora there are the families Canidae (dogs), Felidae (cats), Ursidae (Bears), etc. 8. Genus: A group of similar species forms a genus. Some genera have only one species and are known as monotypic, whereas some have more than one species and are known as polytypic. For example., lion and tiger are placed under the genus Panthera. 9. Species: A species can be defined as a group of organisms with similar features that are capable of breeding and producing fertile offspring. It is the lowest level of taxonomic hierarchy. There are about 8.7 million different species on earth. Species can be further divided into subspecies. E.g. *Bos taurus taurus*, commonly called taurines and *Bos taurus indicus,* commonly called Zebus. **Eukaryotes & Prokaryotes** Eukaryotes are more complex in structure, with nuclei and membrane-bound organelles. Some characteristics of eukaryotes are: - - - - - - Prokaryotes refer to the smallest and simplest type of cells, without a true nucleus and no membrane-bound organelles. Bacteria fall under this category. Some characteristics: - - - - - - **The five Kingdoms** R.H. Whittaker organized the organisms into five kingdoms. He classified organisms on the basis of cell structure, mode, source of nutrition and body design. The five kingdoms proposed by Whittaker are Monera, Protista, Fungi, Plantae, and Animalia. **Monera**  is a kingdom that contains unicellular organisms with a prokaryotic cell organization (having no nuclear membrane), such as bacteria. They are single-celled organisms with no true nuclear membrane (prokaryotic organisms). **Protists**, was introduced by the German biologist Ernst Haeckel in 1866 to classify micro-organisms which are neither animals nor plants. The **Protista** is an heterogeneous group of eukaryotic organisms. That is, the nucleus is surrounded by a nuclear envelope, and they contain organized plastids and mitochondria. Most protists are unicellular, but there are some relatively simple multicellular forms. **Fungi** are organisms which obtain food by absorbing materials in their bodies. Mushrooms and moulds belong in this kingdom. Originally, they were part of the plant kingdom but were recategorised when they were discovered not to photosynthesise. **Plantae** Plantae is the plant kingdom which includes all plants on the earth. They are multicellular eukaryotes. Typically, they consist of a rigid structure that surrounds the cell membrane called the cell wall. [Plants](https://byjus.com/biology/plants/) also have a green coloured pigment called chlorophyll that are quite important for photosynthesis. Hence, they have an autotrophic mode of nutrition. The plant kingdom is a vast group; therefore, the kingdom is further classified into subgroups. Level of classification is based on the following three criteria: 1. **Plant body**: whether the body has well-differentiated structures or not. 2. **Vascular system**: whether the plant has vascular system for transportation of substances or not 3. **Seed formation**: whether the plant bears flowers and seeds or not; if it does, then whether it is enclosed within fruits or not. **Animalia** **General characteristics** - Eukaryotic and multicellualar - They have no cell walls - All are heterotrophic - Most reproduce sexually and few asexually. - Most show locomotion **Origins of Diversity** The diversity in our planet is attributed to diversity within a species. As the world changed in climate and in geography as time passed, the characteristics of species diverged so much that new species were formed. This process, by which new species evolve, was first described by British naturalist Charles Darwin as **natural selection**. For an organism to change, genetic mutations must occur. At times, genetic mutations are accidental, as in the case of prokaryotes when they undergo asexual reproduction. For most eukaryotes, genetic mutations occur through sexual reproduction, where meiosis produces haploid gametes from the original parent cells. The fusion of these haploid gametes into a diploid zygote results in genetic variation in each generation. Over time, with enough arrangement of genes and traits, new species are produced. Sexual reproduction creates an immense potential of genetic variety. One goal of taxonomy is to determine the evolutionary history of organisms. This can be achieved by comparing species living today with species in the past. The comparison in anatomy and structure is based on data from development, physical anatomy, biochemistry, DNA, behaviour, and ecological preferences. The following are examples of how such data is used: **Phylogeny, Cladistics & Cladogram** Modern taxonomy is based on many hypotheses\' of the evolutionary history of organisms, known as **phylogeny**. As with the Scientific Method, scientists develop a hypothesis on the history of an animal and utilise modern science and technology to prove the phylogeny. **Cladistics** is a classification system which is based on phylogeny. Expanding on phylogeny, cladistics is based on the assumption that each group of related species has one common ancestor and would therefore retain some ancestral characteristics. Moreover, as these related species evolve and diverge from their common ancestor, they would develop unique characteristics. Such characteristics are known as **derived characteristics** The principles of phylogeny and cladistics can be expressed visually as a **cladogram**, a branching diagram which acts as a family (phylogenetic) tree for similar species. A cladogram can also be used to test alternative hypotheses for an animal\'s phylogeny. In order to determine the most likely cladogram, the derived characteristics of similar species are matched and analysed. **CELL** Cells are the simplest unit of living organism. The two primary kinds of cells are **eukaryotic** **cells**, which have a true [nucleus](https://www.thoughtco.com/the-cell-nucleus-373362) containing DNA and **prokaryotic cells**, which have no true nucleus. In prokaryotic cells, the DNA is coiled up in a region called the nucleoid. **Cells** are the basic building blocks of all living things. German scientists Theodor Schwann, Matthias Schleiden, and Rudolph Virchow proposed cell theories The Cell Theory states: - All living organisms are composed of [cells](https://www.thoughtco.com/facts-about-cells-373372). They may be unicellular or multicellular. - The cell is the basic unit of life. - Cells arise from pre-existing cells. (They are not derived from [spontaneous generation](https://www.thoughtco.com/spontaneous-generation-4118145).) The modern version of the Cell Theory includes the ideas that: - Energy flow occurs within cells. - Heredity information ([DNA](https://www.thoughtco.com/dna-models-373331)) is passed on from cell to cell. - All cells have the same basic chemical composition. Cells contain [organelles](https://www.thoughtco.com/organelles-meaning-373368), or tiny cellular structures, that carry out specific functions necessary for normal cellular operation. Cells also contain [DNA](https://www.thoughtco.com/dna-373454) (deoxyribonucleic acid) and [RNA](https://www.thoughtco.com/rna-373565) (ribonucleic acid), the genetic information necessary for directing cellular activities. Eukaryotic cells grow and reproduce through a complex sequence of events called the [cell cycle](https://www.thoughtco.com/understanding-the-cell-cycle-373391). At the end of the cycle, cells will divide either through the processes of [mitosis](https://www.thoughtco.com/stages-of-mitosis-373534) or [meiosis](https://www.thoughtco.com/stages-of-meiosis-373512). Somatic cells replicate through mitosis and [sex cells](https://www.thoughtco.com/sex-cells-meaning-373386) reproduce via meiosis. Prokaryotic cells reproduce commonly through a type of asexual reproduction called [binary fission](https://www.thoughtco.com/prokaryotes-meaning-373369). Higher organisms are also capable of [asexual reproduction](https://www.thoughtco.com/asexual-reproduction-373441). Plants, [algae](https://www.thoughtco.com/major-types-of-algae-373409), and [fungi](https://www.thoughtco.com/interesting-facts-about-fungi-373407) reproduce through the formation of reproductive cells called [spores](https://www.thoughtco.com/spores-reproductive-cells-3859771). Animal organisms can reproduce asexually through processes such as budding, fragmentation, regeneration, and [parthenogenesis](https://www.thoughtco.com/parthenogenesis-373474). Cells perform a number of important processes that are necessary for the survival of an organism. Cells undergo the complex process of [cellular respiration](https://www.thoughtco.com/cellular-respiration-process-373396) in order to obtain energy stored in the nutrients consumed. [Photosynthetic organisms](https://www.thoughtco.com/all-about-photosynthetic-organisms-4038227) including [plants](https://www.thoughtco.com/all-about-photosynthetic-organisms-4038227), [algae](https://www.thoughtco.com/all-about-photosynthetic-organisms-4038227), and [cyanobacteria](https://www.thoughtco.com/all-about-photosynthetic-organisms-4038227) are capable of [photosynthesis](https://www.thoughtco.com/photosynthesis-373604). In photosynthesis, light energy from the sun is converted to glucose. Glucose is the energy source used by photosynthetic organisms and other organisms that consume photosynthetic organisms. An organelle is a tiny cellular structure that performs specific functions within a [cell](https://www.thoughtco.com/facts-about-cells-373372). Organelles are embedded within the [cytoplasm](https://www.thoughtco.com/cytoplasm-defined-373301) of eukaryotic and [prokaryotic cells](https://www.thoughtco.com/prokaryotes-meaning-373369). In the more complex [eukaryotic cells](https://www.thoughtco.com/what-are-cells-373361), organelles are often enclosed by their own [membrane](https://www.thoughtco.com/cell-membrane-373364). Analogous to the body\'s internal [organs](https://www.thoughtco.com/organ-systems-373571), organelles are specialized and perform valuable functions necessary for normal cellular operation. Organelles have a wide range of responsibilities that include everything from generating energy for a cell to controlling the cell\'s growth and reproduction.  **Eukaryotic Organelles** Eukaryotic cells are cells with a nucleus. The nucleus is an organelle that is surrounded by a double membrane called the nuclear envelope. The nuclear envelope separates the contents of the nucleus from the rest of the cell. Eukaryotic cells also have a [cell membrane](https://www.thoughtco.com/cell-membrane-373364) (plasma membrane), [cytoplasm](https://www.thoughtco.com/cytoplasm-defined-373301), [cytoskeleton](https://www.thoughtco.com/cytoskeleton-anatomy-373358), and various cellular organelles. Animals, plants, fungi, and protists are examples of eukaryotic organisms. Animal and plant cells contain many of the same kinds or organelles. There are also certain organelles found in plant cells that are not found in animal cells and vice versa. Examples of organelles found in [plant cells](https://www.thoughtco.com/what-is-a-plant-cell-373384) and [animal cells](https://www.thoughtco.com/all-about-animal-cells-373379) include: - [Nucleus](https://www.thoughtco.com/the-cell-nucleus-373362) - a membrane bound structure that contains the cell\'s hereditary ([DNA](https://www.thoughtco.com/dna-373454)) information and controls the cell\'s growth and reproduction. It is commonly the most prominent organelle in the cell. - [Mitochondria](https://www.thoughtco.com/mitochondria-defined-373367) - as the cell\'s power producers, mitochondria convert energy into forms that are usable by the cell. They are the sites of [cellular respiration](https://www.thoughtco.com/cellular-respiration-process-373396) which ultimately generates fuel for the cell\'s activities. Mitochondria are also involved in other cell processes such as [cell division](https://www.thoughtco.com/understanding-the-cell-cycle-373391) and growth, as well as [cell death](https://www.thoughtco.com/apoptosis-372446).​ - [Endoplasmic Reticulum](https://www.thoughtco.com/endoplasmic-reticulum-373365) - extensive network of membranes composed of both regions with ribosomes (rough ER) and regions without ribosomes (smooth ER). This organelle manufactures membranes, secretory [proteins](https://www.thoughtco.com/protein-function-373550), [carbohydrates](https://www.thoughtco.com/carbohydrates-373558), [lipids](https://www.thoughtco.com/lipids-373560), and [hormones](https://www.thoughtco.com/hormones-373559).​ - [Golgi complex](https://www.thoughtco.com/golgi-apparatus-meaning-373366) - also called the Golgi apparatus, this structure is responsible for manufacturing, warehousing, and shipping certain cellular products, particularly those from the endoplasmic reticulum (ER).​ - [Ribosomes](https://www.thoughtco.com/ribosomes-meaning-373363) - these organelles consist of [RNA](https://www.thoughtco.com/rna-373565) and proteins and are responsible for protein production. Ribosomes are found suspended in the cytosol or bound to the endoplasmic reticulum.​ - [Lysosomes](https://www.thoughtco.com/lysosomes-cell-organelles-373357) - these membranous sacs of enzymes recycle the cell\'s organic material by digesting cellular [macromolecules](https://www.thoughtco.com/biological-polymers-373562), such as [nucleic acids](https://www.thoughtco.com/nucleic-acids-373552), polysaccharides, fats, and [proteins](https://www.thoughtco.com/proteins-373564).​ - [Peroxisomes](https://www.thoughtco.com/journey-into-the-cell-peroxisomes-373360) - Like lysosomes, peroxisomes are bound by a membrane and contain enzymes. Peroxisomes help to detoxify alcohol, form bile acid, and break down fats.​ - [Vacuole](https://www.thoughtco.com/vacuole-organelle-373617) - these fluid-filled, enclosed structures are found most commonly in plant cells and fungi. Vacuoles are responsible for a wide variety of important functions in a cell including nutrient storage, detoxification, and waste exportation.​ - [Chloroplast](https://www.thoughtco.com/chloroplast-373614) - this chlorophyll containing plastid is found in plant cells, but not animal cells. Chloroplasts absorb the sun\'s light energy for [photosynthesis](https://www.thoughtco.com/photosynthesis-373604).​ - [Cell Wall](https://www.thoughtco.com/cell-wall-373613) - this rigid outer wall is positioned next to the cell membrane in most plant cells. Not found in animal cells, the cell wall helps to provide support and protection for the cell.​ - [Centrioles](https://www.thoughtco.com/centrioles-373538) - these cylindrical structures are found in animal cells, but not plant cells. Centrioles help to organize the assembly of microtubules during [cell division](https://www.thoughtco.com/understanding-the-cell-cycle-373391).​ - [Cilia and Flagella](https://www.thoughtco.com/cilia-and-flagella-373359) - cilia and flagella are protrusions from some cells that aid in cellular locomotion. They are formed from specialized groupings of [microtubules](https://www.thoughtco.com/microtubules-373545)called basal bodies.